bims-auttor Biomed News
on Autophagy and mTOR
Issue of 2024‒06‒02
58 papers selected by
Viktor Korolchuk, Newcastle University
  1. Autophagy Dysfunction: The Kernel of Hair Loss?
  2. Regulation of TSC2 lysosome translocation and mitochondrial turnover by TSC2 acetylation status.
  3. TBK1 is ubiquitinated by TRIM5α to assemble mitophagy machinery.
  4. Autophagy and machine learning: Unanswered questions.
  5. Targeting the autophagy-NAD axis protects against cell death in Niemann-Pick type C1 disease models.
  6. FIP200 phosphorylation regulates late steps in mitophagy.
  7. The physiological relevance of autophagosome morphogenesis.
  8. RTN3L and CALCOCO1 function in parallel to maintain proteostasis in the endoplasmic reticulum.
  9. Biallelic variants in LARS1 induce steatosis in developing zebrafish liver via enhanced autophagy.
  10. Hyperactive mTORC1/4EBP1 Signaling Dysregulates Proteostasis and Accelerates Cardiac Aging.
  11. ALS-linked C9orf72 dipeptide repeats inhibit starvation-induced autophagy through modulating BCL2-BECN1 interaction.
  12. When an underdog becomes a major player: the role of protein structural disorder in the Atg8 conjugation system.
  13. Bacterial ubiquitin ligases hijack the host deubiquitinase OTUB1 to inhibit MTORC1 signaling and promote autophagy.
  14. Development and characterization of phospho-ubiquitin antibodies to monitor PINK1-PRKN signaling in cells and tissue.
  15. Pathogenic hyperactivation of mTORC1 by cytoplasmic EP300 in Hutchinson-Gilford progeria syndrome.
  16. YIPF3 and YIPF4 regulate autophagic turnover of the Golgi apparatus.
  17. Systemic administration of a novel Beclin 1-derived peptide significantly upregulates autophagy in the spinal motor neurons of autophagy reporter mice.
  18. Vesicle-vesicle fusion promoted by the Atg8-family autophagy protein LC3C: relevance of the N-terminal region.
  19. Unravelling the role of autophagy in human dental pulp.
  20. Regulation of mesenchymal stem cell differentiation by autophagy.
  21. Varicella zoster virus-induced autophagy in human neuronal and hematopoietic cells exerts antiviral activity.
  22. Proteostasis in neurodegenerative diseases.
  23. Molecular determinants of Ras-mTORC2 signaling.
  24. Mitochondrial quality control in human health and disease.
  25. Neuronal activity promotes secretory autophagy for the extracellular release of α-synuclein.
  26. Role of PIM Kinase Inhibitor in the Treatment of Alzheimer's Disease.
  27. Interleukin-1 mediated hyperinflammation in XIAP-deficiency is associated with defective autophagy.
  28. TOR signaling regulates GPCR levels on the plasma membrane and suppresses the Saccharomyces cerevisiae mating pathway.
  29. Targeting TRPs in autophagy regulation and human diseases.
  30. Golm1 facilitates the CaO2-DOPC-DSPE200-PEI -CsPbBr3 QDs -induced apoptotic death of hepatocytes through the stimulation of mitochondrial autophagy and mitochondrial reactive oxygen species production through interactions with P53/Beclin-1/Bcl-2.
  31. Cellular senescence induced by cholesterol accumulation is mediated by lysosomal ABCA1 in APOE4 and AD.
  32. CTCF and BORIS-mediated Autophagy regulation via Alternative splicing of BNIP3L in Breast Cancer.
  33. Axonal autophagic vesicle transport in the rat optic nerve in vivo under normal conditions and during acute axonal degeneration.
  34. Hydatid fluid from Echinococcus granulosus induces autophagy in dendritic cells and promotes polyfunctional T-cell responses.
  35. HRD1-mediated ubiquitination of HDAC2 regulates PPARα-mediated autophagy and alleviates metabolic-associated fatty liver disease.
  36. The 18S rRNA Methyltransferase DIMT-1 Regulates Lifespan in the Germline Later in Life.
  37. Neuronal autosis is Na+/K+-ATPase alpha 3-dependent and involved in hypoxic-ischemic neuronal death.
  38. GSK-3α-BNIP3 axis promotes mitophagy in human cardiomyocytes under hypoxia.
  39. Ibrutinib Contributes to Atrial Arrhythmia through the Autophagic Degradation of Connexins by Inhibiting the PI3K-AKT-mTOR Signaling Pathway.
  40. CircRNA regulates the liquid-liquid phase separation of ATG4B, a novel strategy to inhibit cancer metastasis?
  41. Atg44/Mdi1/mitofissin facilitates Dnm1-mediated mitochondrial fission.
  42. Regulatory feedback loop between circ-EIF4A3 and EIF4A3 Enhances autophagy and growth in colorectal cancer cells.
  43. Pain hypersensitivity is dependent on autophagy protein Beclin 1 in males but not females.
  44. IGF2BP3 modified GLI2 transcriptionally regulates SYVN1 and facilitates sepsis liver injury through autophagy.
  45. Age-related driving mechanisms of retinal diseases and neuroprotection by transcription factor EB-targeted therapy.
  46. Genipin Activates Autophagy and Promotes Myoblast Differentiation by Activating AMPK Pathway.
  47. Chaperone-mediated autophagy protects the bone formation from excessive inflammation through PI3K/AKT/GSK3β/β-catenin pathway.
  48. SPAG5 deficiency activates autophagy to reduce atherosclerotic plaque formation in ApoE-/- mice.
  49. HSP70-mediated mitochondrial dynamics and autophagy represent a novel vulnerability in pancreatic cancer.
  50. Capsule-deficient group A Streptococcus evades autophagy-mediated killing in macrophages.
  51. Spartin is a Lipid Transfer Protein That Facilitates Lipid Droplet Turnover.
  52. A viral small interfering RNA-host plant mRNA pathway modulates virus-induced drought tolerance by enhancing autophagy.
  53. mTOR pathway inhibition alters proliferation as well as differentiation of neural stem cells.
  54. VAMP2 controls murine epidermal differentiation and carcinogenesis by regulation of nucleophagy.
  55. HSDL2 links nutritional cues to bile acid and cholesterol homeostasis.
  56. Impact of long-term rapamycin treatment on age-related osteoarthritis in common marmoset.
  57. TMX2 potentiates cell viability of hepatocellular carcinoma by promoting autophagy and mitophagy.
  58. K48- and K63-linked ubiquitin chain interactome reveals branch- and length-specific ubiquitin interactors.
  1. Clin Cosmet Investig Dermatol. 2024 ;17 1165-1181
    Autophagy Dysfunction: The Kernel of Hair Loss?
    Xiaofan Jin, Xiuzu Song.
      Autophagy is recognized as a crucial regulatory process, instrumental in the removal of senescent, dysfunctional, and damaged cells. Within the autophagic process, lysosomal digestion plays a critical role in the elimination of impaired organelles, thus preserving fundamental cellular metabolic functions and various biological processes. Mitophagy, a targeted autophagic process that specifically focuses on mitochondria, is essential for sustaining cellular health and energy balance. Therefore, a deep comprehension of the operational mechanisms and implications of autophagy and mitophagy is vital for disease prevention and treatment. In this context, we examine the role of autophagy and mitophagy during hair follicle cycles, closely scrutinizing their potential association with hair loss. We also conduct a thorough review of the regulatory mechanisms behind autophagy and mitophagy, highlighting their interaction with hair follicle stem cells and dermal papilla cells. In conclusion, we investigate the potential of manipulating autophagy and mitophagy pathways to develop innovative therapeutic strategies for hair loss.
    Keywords:  alopecia; dermal papilla cell; hair follicle; hair follicle stem cell; mitophagy
    DOI:  https://doi.org/10.2147/CCID.S462294
  2. Sci Rep. 2024 May 31. 14(1): 12521
    Regulation of TSC2 lysosome translocation and mitochondrial turnover by TSC2 acetylation status.
    Patricia Marqués, Jesús Burillo, Carlos González-Blanco, Beatriz Jiménez, Gema García, Ana García-Aguilar, Sarai Iglesias-Fortes, Ángela Lockwood, Carlos Guillén.
      Sirtuin1 (SIRT1) activity decreases the tuberous sclerosis complex 2 (TSC2) lysine acetylation status, inhibiting the mechanistic target of rapamycin complex 1 (mTORC1) signalling and concomitantly, activating autophagy. This study analyzes the role of TSC2 acetylation levels in its translocation to the lysosome and the mitochondrial turnover in both mouse embryonic fibroblast (MEF) and in mouse insulinoma cells (MIN6) as a model of pancreatic β cells. Resveratrol (RESV), an activator of SIRT1 activity, promotes TSC2 deacetylation and its translocation to the lysosome, inhibiting mTORC1 activity. An improvement in mitochondrial turnover was also observed in cells treated with RESV, associated with an increase in the fissioned mitochondria, positive autophagic and mitophagic fluxes and an enhancement of mitochondrial biogenesis. This study proves that TSC2 in its deacetylated form is essential for regulating mTORC1 signalling and the maintenance of the mitochondrial quality control, which is involved in the homeostasis of pancreatic beta cells and prevents from several metabolic disorders such as Type 2 Diabetes Mellitus.
    Keywords:  Acetylation; Lysosome; Mitophagy; Pancreatic β cells; TSC2; mTORC1
    DOI:  https://doi.org/10.1038/s41598-024-63525-7
  3. Cell Rep. 2024 May 29. pii: S2211-1247(24)00622-3. [Epub ahead of print]43(6): 114294
    TBK1 is ubiquitinated by TRIM5α to assemble mitophagy machinery.
    Bhaskar Saha, Hallvard Olsvik, Geneva L Williams, Seeun Oh, Gry Evjen, Eva Sjøttem, Michael A Mandell.
      Ubiquitination of mitochondrial proteins provides a basis for the downstream recruitment of mitophagy machinery, yet whether ubiquitination of the machinery itself contributes to mitophagy is unknown. Here, we show that K63-linked polyubiquitination of the key mitophagy regulator TBK1 is essential for its mitophagy functions. This modification is catalyzed by the ubiquitin ligase TRIM5α and is required for TBK1 to interact with and activate a set of ubiquitin-binding autophagy adaptors including NDP52, p62/SQSTM1, and NBR1. Autophagy adaptors, along with TRIM27, enable TRIM5α to engage with TBK1 following mitochondrial damage. TRIM5α's ubiquitin ligase activity is required for the accumulation of active TBK1 on damaged mitochondria in Parkin-dependent and Parkin-independent mitophagy pathways. Our data support a model in which TRIM5α provides a mitochondria-localized, ubiquitin-based, self-amplifying assembly platform for TBK1 and mitophagy adaptors that is ultimately necessary for the recruitment of the core autophagy machinery.
    Keywords:  CP: Cell biology; NBR1; NDP52; Optineurin; TAX1BP1; TBK1; TRIM27/RFP; autophagy; p62; tripartite motif; ubiquitin ligase
    DOI:  https://doi.org/10.1016/j.celrep.2024.114294
  4. Biochim Biophys Acta Mol Basis Dis. 2024 May 25. pii: S0925-4439(24)00252-7. [Epub ahead of print]1870(6): 167263
    Autophagy and machine learning: Unanswered questions.
    Ying Yang, Zhaoying Pan, Jianhui Sun, Joshua Welch, Daniel J Klionsky.
      Autophagy is a critical conserved cellular process in maintaining cellular homeostasis by clearing and recycling damaged organelles and intracellular components in lysosomes and vacuoles. Autophagy plays a vital role in cell survival, bioenergetic homeostasis, organism development, and cell death regulation. Malfunctions in autophagy are associated with various human diseases and health disorders, such as cancers and neurodegenerative diseases. Significant effort has been devoted to autophagy-related research in the context of genes, proteins, diagnosis, etc. In recent years, there has been a surge of studies utilizing state of the art machine learning (ML) tools to analyze and understand the roles of autophagy in various biological processes. We taxonomize ML techniques that are applicable in an autophagy context, comprehensively review existing efforts being taken in this direction, and outline principles to consider in a biomedical context. In recognition of recent groundbreaking advances in the deep-learning community, we discuss new opportunities in interdisciplinary collaborations and seek to engage autophagy and computer science researchers to promote autophagy research with joint efforts.
    Keywords:  Artificial intelligence; Lysosome; Macroautophagy; Stress
    DOI:  https://doi.org/10.1016/j.bbadis.2024.167263
  5. Cell Death Dis. 2024 May 31. 15(5): 382
    Targeting the autophagy-NAD axis protects against cell death in Niemann-Pick type C1 disease models.
    Tetsushi Kataura, Lucia Sedlackova, Congxin Sun, Gamze Kocak, Niall Wilson, Peter Banks, Faisal Hayat, Sergey Trushin, Eugenia Trushina, Oliver D K Maddocks, John E Oblong, Satomi Miwa, Masaya Imoto, Shinji Saiki, Daniel Erskine, Marie E Migaud, Sovan Sarkar, Viktor I Korolchuk.
      Impairment of autophagy leads to an accumulation of misfolded proteins and damaged organelles and has been implicated in plethora of human diseases. Loss of autophagy in actively respiring cells has also been shown to trigger metabolic collapse mediated by the depletion of nicotinamide adenine dinucleotide (NAD) pools, resulting in cell death. Here we found that the deficit in the autophagy-NAD axis underpins the loss of viability in cell models of a neurodegenerative lysosomal storage disorder, Niemann-Pick type C1 (NPC1) disease. Defective autophagic flux in NPC1 cells resulted in mitochondrial dysfunction due to impairment of mitophagy, leading to the depletion of both the reduced and oxidised forms of NAD as identified via metabolic profiling. Consequently, exhaustion of the NAD pools triggered mitochondrial depolarisation and apoptotic cell death. Our chemical screening identified two FDA-approved drugs, celecoxib and memantine, as autophagy activators which effectively restored autophagic flux, NAD levels, and cell viability of NPC1 cells. Of biomedical relevance, either pharmacological rescue of the autophagy deficiency or NAD precursor supplementation restored NAD levels and improved the viability of NPC1 patient fibroblasts and induced pluripotent stem cell (iPSC)-derived cortical neurons. Together, our findings identify the autophagy-NAD axis as a mechanism of cell death and a target for therapeutic interventions in NPC1 disease, with a potential relevance to other neurodegenerative disorders.
    DOI:  https://doi.org/10.1038/s41419-024-06770-y
  6. J Mol Biol. 2024 May 29. pii: S0022-2836(24)00226-2. [Epub ahead of print] 168631
    FIP200 phosphorylation regulates late steps in mitophagy.
    Christopher Eickhorst, Riccardo Babic, Jorrell Rush-Kittle, Leon Lucya, Fatimah Lami Imam, Pablo Sánchez-Martín, David M Hollenstein, Jonas Michaelis, Christian Münch, Chris Meisinger, Dea Slade, Laura Gámez-Díaz, Claudine Kraft.
      Mitophagy is a specific type of autophagy responsible for the selective elimination of dysfunctional or superfluous mitochondria, ensuring the maintenance of mitochondrial quality control. The initiation of mitophagy is coordinated by the ULK1 kinase complex, which engages mitophagy receptors via its FIP200 subunit. Whether FIP200 performs additional functions in the subsequent later phases of mitophagy beyond this initial step and how its regulation occurs, remains unclear. Our findings reveal that multiple phosphorylation events on FIP200 differentially control the early and late stages of mitophagy. Furthermore, these phosphorylation events influence FIP200's interaction with ATG16L1. In summary, our results highlight the necessity for precise and dynamic regulation of FIP200, underscoring its importance in the progression of mitophagy.
    Keywords:  ATG16L1; Atg1/ULK1 kinase complex; FIP200; autophagy; mitophagy
    DOI:  https://doi.org/10.1016/j.jmb.2024.168631
  7. Trends Biochem Sci. 2024 May 24. pii: S0968-0004(24)00112-9. [Epub ahead of print]
    The physiological relevance of autophagosome morphogenesis.
    Oren Shatz, Zvulun Elazar.
      Autophagy sequesters cytoplasmic portions into autophagosomes. While selective cargo is engulfed by elongation of cup-shaped isolation membranes (IMs), the morphogenesis of non-selective IMs remains elusive. Based on recent observations, we propose a novel model for autophagosome morphogenesis wherein active regulation of the IM rim serves the physiological roles of autophagy.
    Keywords:  Atg2; Atg24; DFCP1; PI3P; autophagy; phagophore
    DOI:  https://doi.org/10.1016/j.tibs.2024.05.002
  8. Autophagy. 2024 May 31. 1-9
    RTN3L and CALCOCO1 function in parallel to maintain proteostasis in the endoplasmic reticulum.
    Kamal Kumar, Ravi Chidambaram, Smriti Parashar, Susan Ferro-Novick.
      Reticulophagy is mediated by autophagy receptors that function in one of the two domains of the ER, tubules or flat sheets. Three different conserved mammalian receptors mediate autophagy in ER tubules: RTN3L, ATL3 and CALCOCO1. Previous studies have shown that RTN3L maintains proteostasis by targeting mutant aggregation-prone proteins for autophagy at distinct foci in ER tubules that we named ERPHS (ER-reticulophagy sites). The role for ATL3 and CALCOCO1 in proteostasis has not been addressed. Here we analyzed three different misfolded disease-causing RTN3L substrates and show that ATL3 and CALCOCO1 target the same cargoes for autophagy. Colocalization and knock down studies revealed that RTN3L and ATL3 are both required for the formation of RTN3L-containing ERPHS, while CALCOCO1 is not. We propose that RTN3L, ATL3 and CALCOCO1 work in parallel to maintain proteostasis within the ER network by targeting cargoes at different sites in the tubules.Abbreviation ATL3: atlastin GTPase 3; Baf: bafilomycin A1; CALCOCO1: calcium binding and coiled-coil domain 1; Epr1: ER-phagy receptor 1; ER: endoplasmic reticulum; ERAD: ER-associated protein degradation; ERPHS: ER-reticulophagy sites; LAMP1: lysosomal associated membrane protein 1; PGRMC1: progesterone receptor membrane component 1; POMC: proopiomelanocortin; Pro-AVP: pro-arginine vasopressin; RETREG1: reticulophagy regulator 1; reticulophagy: endoplasmic reticulum selective autophagy; RTN3L: reticulon 3 long isoform; VAPA: VAMP associated protein A.
    Keywords:  Aggregation-prone proteins; endoplasmic reticulum; endoplasmic reticulum stress; reticulophagy receptors; selective autophagy
    DOI:  https://doi.org/10.1080/15548627.2024.2353502
  9. Orphanet J Rare Dis. 2024 May 28. 19(1): 219
    Biallelic variants in LARS1 induce steatosis in developing zebrafish liver via enhanced autophagy.
    Masanori Inoue, Wulan Apridita Sebastian, Shota Sonoda, Hiroaki Miyahara, Nobuyuki Shimizu, Hiroshi Shiraishi, Miwako Maeda, Kumiko Yanagi, Tadashi Kaname, Reiko Hanada, Toshikatsu Hanada, Kenji Ihara.
      BACKGROUND: Biallelic pathogenic variants of LARS1 cause infantile liver failure syndrome type 1 (ILFS1), which is characterized by acute hepatic failure with steatosis in infants. LARS functions as a protein associated with mTORC1 and plays a crucial role in amino acid-triggered mTORC1 activation and regulation of autophagy. A previous study demonstrated that larsb-knockout zebrafish exhibit conditions resembling ILFS. However, a comprehensive analysis of larsb-knockout zebrafish has not yet been performed because of early mortality.METHODS: We generated a long-term viable zebrafish model carrying a LARS1 variant identified in an ILFS1 patient (larsb-I451F zebrafish) and analyzed the pathogenesis of the affected liver of ILFS1.
    RESULTS: Hepatic dysfunction is most prominent in ILFS1 patients during infancy; correspondingly, the larsb-I451F zebrafish manifested hepatic anomalies during developmental stages. The larsb-I451F zebrafish demonstrates augmented lipid accumulation within the liver during autophagy activation. Inhibition of DGAT1, which converts fatty acids to triacylglycerols, improved lipid droplets in the liver of larsb-I451F zebrafish. Notably, treatment with an autophagy inhibitor ameliorated hepatic lipid accumulation in this model.
    CONCLUSIONS: Our findings suggested that enhanced autophagy caused by biallelic LARS1 variants contributes to ILFS1-associated hepatic dysfunction. Furthermore, the larsb-I451F zebrafish model, which has a prolonged survival rate compared with the larsb-knockout model, highlights its potential utility as a tool for investigating the pathophysiology of ILFS1-associated liver dysfunction.
    Keywords:  Autophagy; DGAT1; Fatty liver; ILFS1; LARS1
    DOI:  https://doi.org/10.1186/s13023-024-03226-6
  10. bioRxiv. 2024 May 14. pii: 2024.05.13.594044. [Epub ahead of print]
    Hyperactive mTORC1/4EBP1 Signaling Dysregulates Proteostasis and Accelerates Cardiac Aging.
    Weronika Zarzycka, Kamil A Kobak, Catherine J King, Frederick F Peelor, Benjamin F Miller, Ying Ann Chiao.
      The mechanistic target of rapamycin complex 1 (mTORC1) has a major impact on aging by regulation of proteostasis. It is well established that mTORC1 signaling is hyperactivated with aging and age-related diseases. Previous studies have shown that partial inhibition of mTOR signaling by rapamycin reverses the age-related decline in cardiac function and structure in old mice. However, the downstream signaling pathways involved in this protection against cardiac aging have not been established. TORC1 phosphorylates 4E-binding protein 1 (4EBP1) to promote the initiation of cap-dependent translation. The aim of this project is to examine the role of the mTORC1/4EBP1 axis in age-related cardiac dysfunction. We utilized a whole-body 4EBP1 KO mouse model, which mimics a hyperactive 4EBP1/eIF4E axis, to investigate the effects of hyperactive mTORC1/4EBP1 axis in cardiac aging. Echocardiographic measurements revealed that young 4EBP1 KO mice have no difference in cardiac function at baseline compared to WT mice. Interestingly, middle-aged (14-15-month-old) 4EBP1 KO mice show impaired diastolic function and myocardial performance compared to age-matched WT mice and their diastolic function and myocardial performance are at similar levels as 24-month-old WT mice, suggesting that 4EBP1 KO mice experience accelerated cardiac aging. Old 4EBP1 KO mice show further declines in systolic and diastolic function compared to middle-aged 4EBP1 KO mice and have worse systolic and diastolic function than age-matched old WT mice. Gene expression levels of heart failure markers are not different between 4EBP1 KO and WT mice at these advanced ages. However, ribosomal biogenesis and overall protein ubiquitination are significantly increased in 4EBP1 KO mice when compared to WT, which suggests dysregulated proteostasis. Together, these results show that a hyperactive 4EBP1/eIF4E axis accelerates cardiac aging, potentially by dysregulating proteostasis.
    DOI:  https://doi.org/10.1101/2024.05.13.594044
  11. Acta Pharm Sin B. 2024 May;14(5): 2026-2038
    ALS-linked C9orf72 dipeptide repeats inhibit starvation-induced autophagy through modulating BCL2-BECN1 interaction.
    Shiqiang Xu, Qilian Ma, Junwen Shen, Ningning Li, Shan Sun, Nana Wang, Yang Chen, Chunsheng Dong, Kin Yip Tam, Jochen H M Prehn, Hongfeng Wang, Zheng Ying.
      Growing evidences indicate that dysfunction of autophagy contributes to the disease pathogenesis of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), two neurodegenerative disorders. The GGGGCC·GGCCCC repeat RNA expansion in chromosome 9 open reading frame 72 (C9orf72) is the most genetic cause of both ALS and FTD. According to the previous studies, GGGGCC·GGCCCC repeat undergoes the unconventional repeat-associated non-ATG translation, which produces dipeptide repeat (DPR) proteins. Although there is a growing understanding that C9orf72 DPRs have a strong ability to harm neurons and induce C9orf72-linked ALS/FTD, whether these DPRs can affect autophagy remains unclear. In the present study, we find that poly-GR and poly-PR, two arginine-containing DPRs which display the most cytotoxic properties according to the previous studies, strongly inhibit starvation-induced autophagy. Moreover, our data indicate that arginine-rich DPRs enhance the interaction between BCL2 and BECN1/Beclin 1 by inhibiting BCL2 phosphorylation, therefore they can impair autophagic clearance of neurodegenerative disease-associated protein aggregates under starvation condition in cells. Importantly, our study not only highlights the role of C9orf72 DPR in autophagy dysfunction, but also provides novel insight that pharmacological intervention of autophagy using SW063058, a small molecule compound that can disrupt the interaction between BECN1 and BCL2, may reduce C9orf72 DPR-induced neurotoxicity.
    Keywords:  Amyotrophic lateral sclerosis; Autophagy; BCL2; BECN1/Beclin 1; C9orf72; Dipeptide repeat; Frontotemporal dementia; Neurodegeneration
    DOI:  https://doi.org/10.1016/j.apsb.2024.02.004
  12. Autophagy. 2024 May 29. 1-8
    When an underdog becomes a major player: the role of protein structural disorder in the Atg8 conjugation system.
    Hana Popelka, Daniel J Klionsky.
      The noncanonical ubiquitin-like conjugation cascade involving the E1 (Atg7), E2 (Atg3, Atg10), and E3 (Atg12-Atg5-Atg16 complex) enzymes is essential for incorporation of Atg8 into the growing phagophore via covalent linkage to PE. This process is an indispensable step in autophagy. Atg8 and E1-E3 enzymes are the first subset from the core autophagy protein machinery structures that were investigated in earlier studies by crystallographic analyses of globular domains. However, research over the past decade shows that many important functions in the conjugation machinery are mediated by intrinsically disordered protein regions (IDPRs) - parts of the protein that do not adopt a stable secondary or tertiary structure, which are inherently dynamic and well suited for protein-membrane interactions but are invisible in protein crystals. Here, we summarize earlier and recent findings on the autophagy conjugation machinery by focusing on the IDPRs. This summary reveals that IDPRs, originally considered dispensable, are in fact major players and a driving force in the function of the autophagy conjugation system. Abbreviation: AD, activation domain of Atg7; AH, amphipathic helix; AIM, Atg8-family interacting motif; CL, catalytic loop (of Atg7); CTD, C-terminal domain; FR, flexible region (of Atg3 or Atg10); GUV, giant unilammelar vesicles; HR, handle region (of Atg3); IDPR, intrinsically disordered protein region; IDPs: intrinsically disordered proteins; LIR, LC3-interacting region; NHD: N-terminal helical domain; NMR, nuclear magnetic resonance; PE, phosphatidylethanolamine; UBL, ubiquitin like.
    Keywords:  Atg8–PE conjugation; E1-E2-E3-like enzymes; crystal structure; membrane association; protein intrinsic disorder
    DOI:  https://doi.org/10.1080/15548627.2024.2357496
  13. Autophagy. 2024 May 31. 1-16
    Bacterial ubiquitin ligases hijack the host deubiquitinase OTUB1 to inhibit MTORC1 signaling and promote autophagy.
    Kelong Ma, Wei Xian, Hongtao Liu, Rundong Shu, Jinli Ge, Zhao-Qing Luo, Xiaoyun Liu, Jiazhang Qiu.
      Many bacterial pathogens have evolved effective strategies to interfere with the ubiquitination network to evade clearance by the innate immune system. Here, we report that OTUB1, one of the most abundant deubiquitinases (DUBs) in mammalian cells, is subjected to both canonical and noncanonical ubiquitination during Legionella pneumophila infection. The effectors SidC and SdcA catalyze OTUB1 ubiquitination at multiple lysine residues, resulting in its association with a Legionella-containing vacuole. Lysine ubiquitination by SidC and SdcA promotes interactions between OTUB1 and DEPTOR, an inhibitor of the MTORC1 pathway, thus suppressing MTORC1 signaling. The inhibition of MTORC1 leads to suppression of host protein synthesis and promotion of host macroautophagy/autophagy during L. pneumophila infection. In addition, members of the SidE family effectors (SidEs) induce phosphoribosyl (PR)-linked ubiquitination of OTUB1 at Ser16 and Ser18 and block its DUB activity. The levels of the lysine and serine ubiquitination of OTUB1 are further regulated by effectors that function to antagonize the activities of SidC, SdcA and SidEs, including Lem27, DupA, DupB, SidJ and SdjA. Our study reveals an effectors-mediated complicated mechanism in regulating the activity of a host DUB.Abbreviations: BafA1: bafilomycin A1; BMDMs: bone marrow-derived macrophages; DUB: deubiquitinase; Dot/Icm: defective for organelle trafficking/intracellular multiplication; DEPTOR: DEP domain containing MTOR interacting protein; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; L. pneumophila: Legionella pneumophila; LCV: Legionella-containing vacuole; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MOI: multiplicity of infection; MTORC1: mechanistic target of rapamycin kinase complex 1; OTUB1: OTU deubiquitinase, ubiquitin aldehyde binding 1; PR-Ub: phosphoribosyl (PR)-linked ubiquitin; PTM: posttranslational modification; SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel electrophoresis; SidEs: SidE family effectors; Ub: ubiquitin.
    Keywords:  DEPTOR; deubiquitinase; effector protein; intracellular bacteria; type IV secretion system; ubiquitination
    DOI:  https://doi.org/10.1080/15548627.2024.2353492
  14. Autophagy. 2024 May 27. 1-16
    Development and characterization of phospho-ubiquitin antibodies to monitor PINK1-PRKN signaling in cells and tissue.
    Jens O Watzlawik, Xu Hou, Tyrique Richardson, Szymon L Lewicki, Joanna Siuda, Zbigniew K Wszolek, Casey N Cook, Leonard Petrucelli, Michael DeTure, Dennis W Dickson, Odetta Antico, Miratul M K Muqit, Jordan B Fishman, Karima Pirani, Ravindran Kumaran, Nicole K Polinski, Fabienne C Fiesel, Wolfdieter Springer.
      The selective removal of dysfunctional mitochondria, a process termed mitophagy, is critical for cellular health and impairments have been linked to aging, Parkinson disease, and other neurodegenerative conditions. A central mitophagy pathway is orchestrated by the ubiquitin (Ub) kinase PINK1 together with the E3 Ub ligase PRKN/Parkin. The decoration of damaged mitochondrial domains with phosphorylated Ub (p-S65-Ub) mediates their elimination though the autophagy system. As such p-S65-Ub has emerged as a highly specific and quantitative marker of mitochondrial damage with significant disease relevance. Existing p-S65-Ub antibodies have been successfully employed as research tools in a range of applications including western blot, immunocytochemistry, immunohistochemistry, and enzyme-linked immunosorbent assay. However, physiological levels of p-S65-Ub in the absence of exogenous stress are very low, therefore difficult to detect and require reliable and ultrasensitive methods. Here we generated and characterized a collection of novel recombinant, rabbit monoclonal p-S65-Ub antibodies with high specificity and affinity in certain applications that allow the field to better understand the molecular mechanisms and disease relevance of PINK1-PRKN signaling. These antibodies may also serve as novel diagnostic or prognostic tools to monitor mitochondrial damage in various clinical and pathological specimens.Abbreviations: AD: Alzheimer disease; CCCP: carbonyl cyanide 3-chlorophenylhydrazone; ELISA: enzyme-linked immunosorbent assay; HEK293E cell: human embryonic kidney E cell; ICC: immunocytochemistry; IHC: immunohistochemistry: KO: knockout; LoB: limit of blank; LoD: limit of detection; LoQ: limit of quantification; MEF: mouse embryonic fibroblast; MSD: Meso Scale Discovery; n.s.: non-significant; nonTg: non-transgenic; PBMC: peripheral blood mononuclear cell; PD: Parkinson disease; p-S65-PRKN: phosphorylated PRKN at serine 65; p-S65-Ub: phosphorylated Ub at serine 65; Ub: ubiquitin; WT: wild-type.
    Keywords:  Autophagy; PINK1; Parkinson disease; mitochondria; mitophagy; ubiquitin
    DOI:  https://doi.org/10.1080/15548627.2024.2356490
  15. Cell Stress. 2024 ;8 51-55
    Pathogenic hyperactivation of mTORC1 by cytoplasmic EP300 in Hutchinson-Gilford progeria syndrome.
    Lucille Ferret, Guido Kroemer, Mojgan Djavaheri-Mergny.
      In a recent issue in Nature Cell Biology, Sung Min Son et al. unveil a novel layer in the regulation of the mTORC1/autophagy axis by EP300 which can undergo nucleocytoplasmic shuttling in response to alterations in nutrient availability. The study highlights that, in Hutchinson-Gilford progeria syndrome, overabundant cytoplasmic EP300 results in mTORC1 hyperactivation and impaired autophagy, potentially contributing to premature and accelerated aging.
    Keywords:  EP300; MTORC1; aging; autophagy
    DOI:  https://doi.org/10.15698/cst2024.04.295
  16. EMBO J. 2024 May 31.
    YIPF3 and YIPF4 regulate autophagic turnover of the Golgi apparatus.
    Shinri Kitta, Tatsuya Kaminishi, Momoko Higashi, Takayuki Shima, Kohei Nishino, Nobuhiro Nakamura, Hidetaka Kosako, Tamotsu Yoshimori, Akiko Kuma.
      The degradation of organelles by autophagy is essential for cellular homeostasis. The Golgi apparatus has recently been demonstrated to be degraded by autophagy, but little is known about how the Golgi is recognized by the forming autophagosome. Using quantitative proteomic analysis and two novel Golgiphagy reporter systems, we found that the five-pass transmembrane Golgi-resident proteins YIPF3 and YIPF4 constitute a Golgiphagy receptor. The interaction of this complex with LC3B, GABARAP, and GABARAPL1 is dependent on a LIR motif within YIPF3 and putative phosphorylation sites immediately upstream; the stability of the complex is governed by YIPF4. Expression of a YIPF3 protein containing a mutated LIR motif caused an elongated Golgi morphology, indicating the importance of Golgi turnover via selective autophagy. The reporter assays reported here may be readily adapted to different experimental contexts to help deepen our understanding of Golgiphagy.
    Keywords:  Autophagy Receptor; Golgi Turnover; Golgiphagy; Organelle Degradation; Selective Autophagy
    DOI:  https://doi.org/10.1038/s44318-024-00131-3
  17. Int J Pharm. 2024 May 10. pii: S0378-5173(24)00432-0. [Epub ahead of print] 124198
    Systemic administration of a novel Beclin 1-derived peptide significantly upregulates autophagy in the spinal motor neurons of autophagy reporter mice.
    Azin Amin, Nirma D Perera, Doris Tomas, Brittany Cuic, Mona Radwan, Danny M Hatters, Bradley J Turner, Fazel Shabanpoor.
      Autophagy, an intracellular degradation system, plays a vital role in protecting cells by clearing damaged organelles, pathogens, and protein aggregates. Autophagy upregulation through pharmacological interventions has gained significant attention as a potential therapeutic avenue for proteinopathies. Here, we report the development of an autophagy-inducing peptide (BCN4) derived from the Beclin 1 protein, the master regulator of autophagy. To deliver the BCN4 into cells and the central nervous system (CNS), it was conjugated to our previously developed cell and blood-brain barrier-penetrating peptide (CPP). CPP-BCN4 significantly upregulated autophagy and reduced protein aggregates in motor neuron (MN)-like cells. Moreover, its systemic administration in a reporter mouse model of autophagy resulted in a significant increase in autophagy activity in the spinal MNs. Therefore, this novel autophagy-inducing peptide with a demonstrated ability to upregulate autophagy in the CNS has significant potential for the treatment of various neurodegenerative diseases with protein aggregates as a characteristic feature.
    Keywords:  Autophagy; Beclin; Blood-brain barrier; Neurodegenerative diseases; Peptides; Protein aggregates
    DOI:  https://doi.org/10.1016/j.ijpharm.2024.124198
  18. Autophagy. 2024 May 31. 1-3
    Vesicle-vesicle fusion promoted by the Atg8-family autophagy protein LC3C: relevance of the N-terminal region.
    Uxue Ballesteros, Alicia Alonso, L Ruth Montes, Asier Etxaniz.
      Among the MAP1LC3/LC3 subfamily of Atg8 proteins, LC3B and LC3C constitute the most and least studied members, respectively, LC3B being generally considered as an autophagosomal marker and a canonical representative of the LC3 subfamily. In several recent studies, LC3C has emerged as an important modulator in various processes of cell homeostasis. Our own research data demonstrate that LC3C induces higher levels of tethering and of intervesicular lipid mixing than LC3B. LC3C contains a peculiar N-terminal region, different from the other Atg8-family protein members. Using a series of mutants, we have shown that the N-terminal region of LC3C is responsible for the enhanced vesicle tethering, membrane perturbation and vesicle-vesicle fusion activities of LC3C as compared to LC3B.Abbreviations: ATG: autophagy related; GABARAP: gamma-aminobutyric acid receptor associated protein; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; PC: phosphatidyl choline; PE: phosphatidylethanolamine; PEmal: maleimide-derivatized PE; PtdIns: phosphatidylinositol.
    Keywords:  Atg8; LC3C; N terminus; autophagy proteins; vesicle fusion
    DOI:  https://doi.org/10.1080/15548627.2024.2359354
  19. J Oral Maxillofac Pathol. 2024 Jan-Mar;28(1):28(1): 106-108
    Unravelling the role of autophagy in human dental pulp.
    Tulika Wakhloo, Sanjeev Kishore, Prashant Durgapal.
      Autophagy is an evolutionarily conserved intracellular catabolic process that recycles and degrades proteins, organelles and pathogens. It is an endogenous defence mechanism regulating multiple cellular pathways like apoptosis, inflammation, immune response and pathogen clearance and acts as a modulator of pathogenesis. This article highlights the emerging role of autophagy in inflammation and regeneration of human dental pulp. It emphasizes exploring autophagy and autophagy agonists as potential targets for the development of novel therapeutic interventions.
    Keywords:  Autophagy; platelet-rich plasma; pulpitis; rapamycin; regenerative dentistry; therapeutic targets
    DOI:  https://doi.org/10.4103/jomfp.jomfp_197_23
  20. Open Med (Wars). 2024 ;19(1): 20240968
    Regulation of mesenchymal stem cell differentiation by autophagy.
    Yanan Wei, Zejun Zheng, Ying Zhang, Jinmeng Sun, Shuangshuang Xu, Xinsheng Di, Xiaoling Ding, Gang Ding.
      Autophagy, a process that isolates intracellular components and fuses them with lysosomes for degradation, plays an important cytoprotective role by eliminating harmful intracellular substances and maintaining cellular homeostasis. Mesenchymal stem cells (MSCs) are multipotent progenitor cells with the capacity for self-renewal that can give rise to a subset of tissues and therefore have potential in regenerative medicine. However, a variety of variables influence the biological activity of MSCs following their proliferation and transplantation in vitro. The regulation of autophagy in MSCs represents a possible mechanism that influences MSC differentiation properties under the right microenvironment, affecting their regenerative and therapeutic potential. However, a deeper understanding of exactly how autophagy is mobilized to function as well as clarifying the mechanisms by which autophagy promotes MSCs differentiation is still needed. Here, we review the current literature on the complex link between MSCs differentiation and autophagy induced by various extracellular or intracellular stimuli and the molecular targets that influence MSCs lineage determination, which may highlight the potential regulation of autophagy on MSCs' therapeutic capacity, and provide a broader perspective on the clinical application of MSCs in the treatment of a wide range of diseases.
    Keywords:  autophagy; differentiation; mesenchymal stem cells; regenerative medicine
    DOI:  https://doi.org/10.1515/med-2024-0968
  21. J Med Virol. 2024 Jun;96(6): e29690
    Varicella zoster virus-induced autophagy in human neuronal and hematopoietic cells exerts antiviral activity.
    Johanna L Heinz, Daniëla M Hinke, Muyesier Maimaitili, Jiayi Wang, Ira K D Sabli, Michelle Thomsen, Ensieh Farahani, Fanghui Ren, Lili Hu, Thomas Zillinger, Anna Grahn, Joanna von Hofsten, Georges M G M Verjans, Søren R Paludan, Abel Viejo-Borbolla, Vanessa Sancho-Shimizu, Trine H Mogensen.
      Autophagy is a degradational pathway with pivotal roles in cellular homeostasis and survival, including protection of neurons in the central nervous system (CNS). The significance of autophagy as antiviral defense mechanism is recognized and some viruses hijack and modulate this process to their advantage in certain cell types. Here, we present data demonstrating that the human neurotropic herpesvirus varicella zoster virus (VZV) induces autophagy in human SH-SY5Y neuronal cells, in which the pathway exerts antiviral activity. Productively VZV-infected SH-SY5Y cells showed increased LC3-I-LC3-II conversion as well as co-localization of the viral glycoprotein E and the autophagy receptor p62. The activation of autophagy was dependent on a functional viral genome. Interestingly, inducers of autophagy reduced viral transcription, whereas inhibition of autophagy increased viral transcript expression. Finally, the genotype of patients with severe ocular and brain VZV infection were analyzed to identify potential autophagy-associated inborn errors of immunity. Two patients expressing genetic variants in the autophagy genes ULK1 and MAP1LC3B2, respectively, were identified. Notably, cells of both patients showed reduced autophagy, alongside enhanced viral replication and death of VZV-infected cells. In conclusion, these results demonstrate a neuro-protective role for autophagy in the context of VZV infection and suggest that failure to mount an autophagy response is a potential predisposing factor for development of severe VZV disease.
    Keywords:  CNS infection; acute retinal necrosis; autophagy; innate immunity; varicella zoster virus
    DOI:  https://doi.org/10.1002/jmv.29690
  22. Adv Clin Chem. 2024 ;pii: S0065-2423(24)00063-5. [Epub ahead of print]121 270-333
    Proteostasis in neurodegenerative diseases.
    Sumit Kinger, Yuvraj Anandrao Jagtap, Prashant Kumar, Akash Choudhary, Amit Prasad, Vijay Kumar Prajapati, Amit Kumar, Gunjan Mehta, Amit Mishra.
      Proteostasis is essential for normal function of proteins and vital for cellular health and survival. Proteostasis encompasses all stages in the "life" of a protein, that is, from translation to functional performance and, ultimately, to degradation. Proteins need native conformations for function and in the presence of multiple types of stress, their misfolding and aggregation can occur. A coordinated network of proteins is at the core of proteostasis in cells. Among these, chaperones are required for maintaining the integrity of protein conformations by preventing misfolding and aggregation and guide those with abnormal conformation to degradation. The ubiquitin-proteasome system (UPS) and autophagy are major cellular pathways for degrading proteins. Although failure or decreased functioning of components of this network can lead to proteotoxicity and disease, like neuron degenerative diseases, underlying factors are not completely understood. Accumulating misfolded and aggregated proteins are considered major pathomechanisms of neurodegeneration. In this chapter, we have described the components of three major branches required for proteostasis-chaperones, UPS and autophagy, the mechanistic basis of their function, and their potential for protection against various neurodegenerative conditions, like Alzheimer's, Parkinson's, and Huntington's disease. The modulation of various proteostasis network proteins, like chaperones, E3 ubiquitin ligases, proteasome, and autophagy-associated proteins as therapeutic targets by small molecules as well as new and unconventional approaches, shows promise.
    Keywords:  Autophagy; Chaperones; Misfolded Proteins; Neurodegeneration; Proteasome; Ubiquitin
    DOI:  https://doi.org/10.1016/bs.acc.2024.04.002
  23. J Biol Chem. 2024 May 28. pii: S0021-9258(24)01924-0. [Epub ahead of print] 107423
    Molecular determinants of Ras-mTORC2 signaling.
    Stephen F Smith, A F M Tariqul Islam, Shoxruxxon Alimukhamedov, Ethan T Weiss, Pascale G Charest.
      Recent research has identified the mechanistic Target of Rapamycin Complex 2 (mTORC2) as a conserved direct effector of Ras proteins. While previous studies suggested the involvement of the Switch I (SWI) effector domain of Ras in binding mTORC2 components, the regulation of the Ras-mTORC2 pathway is not entirely understood. In Dictyostelium, mTORC2 is selectively activated by the Ras protein RasC, and the RasC-mTORC2 pathway then mediates chemotaxis to cAMP and cellular aggregation by regulating the actin cytoskeleton and promoting cAMP signal relay. Here, we investigated the role of specific residues in RasC's SWI, C-terminal allosteric domain, and hypervariable region (HVR) related to mTORC2 activation. Interestingly, our results suggest that RasC SWI residue A31, which was previously implicated in RasC-mediated aggregation, regulates RasC's specific activation by the Aimless RasGEF. On the other hand, our investigation identified a crucial role for RasC SWI residue T36, with secondary contributions from E38 and allosteric domain residues. Finally, we found that conserved basic residues and the adjacent prenylation site in the HVR, which are crucial for RasC's membrane localization, are essential for RasC-mTORC2 pathway activation by allowing for both RasC's own cAMP-induced activation and its subsequent activation of mTORC2. Therefore, our findings revealed new determinants of RasC-mTORC2 pathway specificity in Dictyostelium, contributing to a deeper understanding of Ras signaling regulation in eukaryotic cells.
    Keywords:  Dictyostelium; HVR; RasC; allosteric domain; hypervariable region; mTOR; mechanistic Target of Rapamycin Complex 2; switch I
    DOI:  https://doi.org/10.1016/j.jbc.2024.107423
  24. Mil Med Res. 2024 May 29. 11(1): 32
    Mitochondrial quality control in human health and disease.
    Bo-Hao Liu, Chen-Zhen Xu, Yi Liu, Zi-Long Lu, Ting-Lv Fu, Guo-Rui Li, Yu Deng, Guo-Qing Luo, Song Ding, Ning Li, Qing Geng.
      Mitochondria, the most crucial energy-generating organelles in eukaryotic cells, play a pivotal role in regulating energy metabolism. However, their significance extends beyond this, as they are also indispensable in vital life processes such as cell proliferation, differentiation, immune responses, and redox balance. In response to various physiological signals or external stimuli, a sophisticated mitochondrial quality control (MQC) mechanism has evolved, encompassing key processes like mitochondrial biogenesis, mitochondrial dynamics, and mitophagy, which have garnered increasing attention from researchers to unveil their specific molecular mechanisms. In this review, we present a comprehensive summary of the primary mechanisms and functions of key regulators involved in major components of MQC. Furthermore, the critical physiological functions regulated by MQC and its diverse roles in the progression of various systemic diseases have been described in detail. We also discuss agonists or antagonists targeting MQC, aiming to explore potential therapeutic and research prospects by enhancing MQC to stabilize mitochondrial function.
    Keywords:  Cancer; Cardiovascular disease; Digestive system disease; Kidney disease; Metabolic disease; Metabolism; Mitochondrial quality control; Nervous disease; Programmed cell death; Pulmonary disease
    DOI:  https://doi.org/10.1186/s40779-024-00536-5
  25. J Biol Chem. 2024 May 28. pii: S0021-9258(24)01920-3. [Epub ahead of print] 107419
    Neuronal activity promotes secretory autophagy for the extracellular release of α-synuclein.
    Yoshitsugu Nakamura, Taiki Sawai, Kensuke Kakiuchi, Shigeki Arawaka.
      Extracellular secretion is an essential mechanism for α-synuclein (α-syn) proteostasis. Although it was reported that neuronal activity affects α-syn secretion, the underlying mechanisms remain unclear. Here, we investigated the autophagic processes that regulate the physiological release of α-syn in mouse primary cortical neurons and SH-SY5Y cells. Stimulating neuronal activity with glutamate or depolarization with high KCl enhanced α-syn secretion. This glutamate-induced α-syn secretion was blocked by a mixture of NMDA receptor antagonist AP5 and AMPA receptor antagonist NBQX, as well as by cytosolic Ca2+ chelator BAPTA-AM. Additionally, mTOR inhibitor rapamycin increased α-syn and p62/SQSTM1 (p62) secretion, and this effect of rapamycin was reduced in primary cortical neurons deficient in the autophagy regulator beclin 1 (derived from BECN1+/- mice). Glutamate-induced α-syn and p62 secretion was suppressed by knockdown of ATG5, which is required for autophagosome formation. Glutamate increased LC3-II generation and decreased intracellular p62 levels, and the increase in LC3-II levels was blocked by BAPTA-AM. Moreover, glutamate promoted co-localization of α-syn with LC3-positive puncta, but not with LAMP1-positive structures in the neuronal somas. Glutamate-induced α-syn and p62 secretion was also reduced by knockdown of RAB8A, which is required for autophagosome fusion with the plasma membrane. Collectively, these findings suggest that stimulating neuronal activity mediates autophagic α-syn secretion in a cytosolic Ca2+-dependent manner, and autophagosomes may participate in autophagic secretion by functioning as α-syn carriers.
    Keywords:  Autophagy; Calcium; Glutamate; Parkinson disease; Protein secretion; Synuclein
    DOI:  https://doi.org/10.1016/j.jbc.2024.107419
  26. Mol Neurobiol. 2024 May 30.
    Role of PIM Kinase Inhibitor in the Treatment of Alzheimer's Disease.
    Shreyasi Meur, Swarupananda Mukherjee, Souvik Roy, Dipanjan Karati.
      Alzheimer's disease (AD), a neurodegenerative disorder, is the most prevalent form of senile dementia, causing progressive deterioration of cognition, behavior, and rational skills. Neuropathologically, AD is characterized by two hallmark proteinaceous aggregates: amyloid beta (Aβ) plaques and neurofibrillary tangles (NFTs) formed of hyperphosphorylated tau. A significant study has been done to understand how Aβ and/or tau accumulation can alter signaling pathways that affect neuronal function. A conserved protein kinase known as the mammalian target of rapamycin (mTOR) is essential for maintaining the proper balance between protein synthesis and degradation. Overwhelming evidence shows mTOR signaling's primary role in age-dependent cognitive decline and the pathogenesis of AD. Postmortem human AD brains consistently show an upregulation of mTOR signaling. Confocal microscopy findings demonstrated a direct connection between mTOR and intraneuronal Aβ42 through molecular processes of PRAS40 phosphorylation. By attaching to the mTORC1 complex, PRAS40 inhibits the activity of mTOR. Furthermore, inhibiting PRAS40 phosphorylation can stop the Aβ-mediated increase in mTOR activity, indicating that the accumulation of Aβ may aid in PRAS40 phosphorylation. Physiologically, PRAS40 is phosphorylated by PIM1 which is a serine/threonine kinase of proto-oncogene PIM kinase family. Pharmacological inhibition of PIM1 activity prevents the Aβ-induced mTOR hyperactivity in vivo by blocking PRAS40 phosphorylation and restores cognitive impairments by enhancing proteasome function. Recently identified small-molecule PIM1 inhibitors have been developed as potential therapeutic to reduce AD-neuropathology. This comprehensive study aims to address the activity of PIM1 inhibitor that has been tested for the treatment of AD, in addition to the pharmacological and structural aspects of PIM1.
    Keywords:  Alzheimer’s disease; PIM kinase inhibitor; PIM1; PRAS40 phosphorylation; mTOR; mTORC1 complex
    DOI:  https://doi.org/10.1007/s12035-024-04257-7
  27. Blood. 2024 May 31. pii: blood.2023023707. [Epub ahead of print]
    Interleukin-1 mediated hyperinflammation in XIAP-deficiency is associated with defective autophagy.
    Dilan Dissanayake, Ashkan Firouzabady, Mohammad Massumi, Guillermo A de Paz Linares, Christian Marshall, Spencer A Freeman, Ronald Laxer, Rae S M Yeung.
      Deficiency of X-linked Inhibitor of Apoptosis Protein (XIAP) is a rare genetic condition that can present with recurrent episodes of hemophagocytic lymphohistiocytosis (HLH), though the exact mechanisms leading to this hyperinflammatory disorder are unclear. Understanding its biology is critical to developing targeted therapies for this potentially fatal disease. Here we report on a novel multi-exonic intragenic duplication leading to XIAP deficiency with recurrent HLH that demonstrated complete response to interleukin (IL)-1b blockade. We further demonstrate using both primary patient cells and genetically modified THP-1 monocyte cell lines that, contrary to what has previously been shown in mouse cells, XIAP-deficient human macrophages do not produce excess IL-1b when stimulated under standard conditions. Instead, NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome-mediated hyperproduction of IL-1b is observed only when the XIAP-deficient cells are stimulated under autophagy-promoting conditions and this correlates with defective autophagic flux as measured by decreased accumulation of the early autophagy marker LC3-II. This work therefore highlights IL-1b blockade as a therapeutic option for patients with XIAP deficiency experiencing recurrent HLH and identifies a critical role for XIAP in promoting autophagy as a means of limiting IL-1b-mediated hyperinflammation during periods of cellular stress.
    DOI:  https://doi.org/10.1182/blood.2023023707
  28. bioRxiv. 2024 May 13. pii: 2024.05.09.593412. [Epub ahead of print]
    TOR signaling regulates GPCR levels on the plasma membrane and suppresses the Saccharomyces cerevisiae mating pathway.
    Nicholas R Leclerc, Toby M Dunne, Sudati Shrestha, Cory P Johnson, Joshua B Kelley.
      Saccharomyces cerevisiae respond to mating pheromone through the GPCRs Ste2 and Ste3, which promote growth of a mating projection in response to ligand binding. This commitment to mating is nutritionally and energetically taxing, and so we hypothesized that the cell may suppress mating signaling during starvation. We set out to investigate negative regulators of the mating pathway in nutritionally depleted environments. Here, we report that nutrient deprivation led to loss of Ste2 from the plasma membrane. Recapitulating this effect with nitrogen starvation led us to hypothesize that it was due to TORC1 signaling. Rapamycin inhibition of TORC1 impacted membrane levels of all yeast GPCRs. Inhibition of TORC1 also dampened mating pathway output. Deletion analysis revealed that TORC1 repression leads to α-arrestin-directed CME through TORC2-Ypk1 signaling. We then set out to determine whether major downstream effectors of the TOR complexes also downregulate pathway output during mating. We found that autophagy contributes to pathway downregulation through analysis of strains lacking ATG8 . We also show that Ypk1 significantly reduced pathway output. Thus, both autophagy machinery and TORC2-Ypk1 signaling serve as attenuators of pheromone signaling during mating. Altogether, we demonstrate that the stress-responsive TOR complexes coordinate GPCR endocytosis and reduce the magnitude of pheromone signaling, in ligand-independent and ligand-dependent contexts.One Sentence Summary: TOR signaling regulates the localization of all Saccharomyces cerevisiae GPCRs during starvation and suppress the mating pathway in the presence and absence of ligand.
    DOI:  https://doi.org/10.1101/2024.05.09.593412
  29. Eur J Pharmacol. 2024 May 29. pii: S0014-2999(24)00369-8. [Epub ahead of print] 176681
    Targeting TRPs in autophagy regulation and human diseases.
    Yongkang Yuan, Qiuju Zhang, Feng Qiu, Ning Kang, Qiang Zhang.
      Transient receptor potential channels (TRPs) are widely recognized as a group of ion channels involved in various sensory perceptions, such as temperature, taste, pressure, and vision. While macroautophagy (hereafter referred to as autophagy) is primarily regulated by core machinery, the ion exchange mediated by TRPs between intracellular and extracellular compartments, as well as within organelles and the cytoplasm, plays a crucial role in autophagy regulation as an important signaling transduction mechanism. Moreover, certain TRPs can directly interact with autophagy regulatory proteins to participate in autophagy regulation. In this article, we provide an in-depth review of the current understanding of the regulatory mechanisms of autophagy, with a specific focus on TRPs. Furthermore, we highlight the potential prospects for drug development targeting TRPs in autophagy for the treatment of human diseases.
    Keywords:  Autophagy; Disease targets; Human diseases; cellular and molecular mechanisms; transient receptor potential channels
    DOI:  https://doi.org/10.1016/j.ejphar.2024.176681
  30. Chem Biol Interact. 2024 May 28. pii: S0009-2797(24)00222-9. [Epub ahead of print] 111076
    Golm1 facilitates the CaO2-DOPC-DSPE200-PEI -CsPbBr3 QDs -induced apoptotic death of hepatocytes through the stimulation of mitochondrial autophagy and mitochondrial reactive oxygen species production through interactions with P53/Beclin-1/Bcl-2.
    Zhiqiang Zhang, Qinglong Wang, Haibo Zhang, Shengchao Wang, Xia Ma, Hui Wang.
      Mitophagy is a distinct physiological process that can have beneficial or deleterious effects in particular tissues. Prior research suggests that mitophagic activity can be triggered by CaO2-PM-CsPbBr3 QDs, yet the specific role that mitophagy plays in hepatic injury induced by CaO2-PM-CsPbBr3 QDs has yet to be established. Accordingly, in this study a series of mouse model- and cell-based experiments were performed that revealed the ability of CaO2-PM-CsPbBr3 QDs to activate mitophagic activity. Golm1 was upregulated in response to CaO2-PM-CsPbBr3 QDs treatment, and overexpressing Golm1 induced autophagic flux in the murine liver and hepatocytes, whereas knocking down Golm1 had the opposite effect. CaO2-PM-CsPbBr3 QDs were also able to Golm1 expression, in turn promoting the degradation of P53 and decreasing the half-life of this protein. Overexpressing Golm1 was sufficient to suppress the apoptotic death of hepatocytes in vitro and in vivo, whereas the knockdown of Golm1 had the opposite effect. The ability of Golm1 to promote p53-mediated autophagy was found to be associated with the disruption of Beclin-1 binding to Bcl-2, and the Golm1 N-terminal domain was determined to be required for p53 interactions, inducing autophagic activity in a manner independent of helicase activity or RNA binding. Together, these results indicate that inhibiting Golm1 can promote p53-dependent autophagy via disrupting Beclin-1 binding to Bcl-2, highlighting a novel approach to mitigating liver injury induced by CaO2-PM-CsPbBr3 QDs.
    Keywords:  CaO2-PM-CsPbBr3 QDs; Golm1; mitochondrial autophagy; mtROS
    DOI:  https://doi.org/10.1016/j.cbi.2024.111076
  31. Res Sq. 2024 May 14. pii: rs.3.rs-4373201. [Epub ahead of print]
    Cellular senescence induced by cholesterol accumulation is mediated by lysosomal ABCA1 in APOE4 and AD.
    Shaowei Wang, Boyang Li, Zhiheng Cai, Cristelle Hugo, Jie Li, Yi Sun, Lu Qian, Alan T Remaley, Julia Tcw, Helena C Chui, David A Bennett, Zoe Arvanitakis, Bilal Kerman, Hussein Yassine.
      Background Cellular senescence is a hallmark of aging and has been implicated in Alzheimer's disease (AD) pathogenesis. Cholesterol accumulation drives cellular senescence; however, the underlying mechanisms are unclear. ATP-binding cassette transporter A1 (ABCA1) plays an important role in cholesterol homeostasis. ABCA1 expression and its trafficking is altered in APOE4 and AD cellular and mouse models. However, whether ABCA1 trafficking is involved in cellular senescence in APOE4 and AD remains unknown. Methods We examined the association between cellular senescence and ABCA1 expression in human postmortem brain samples using transcriptomic, histological, and biochemical analyses. An unbiased proteomic screening was performed to identify targets that mediate cellular ABCA1 trafficking. APOE4-TR mice, immortalized, primary and induced pluripotent stem cell (iPSC) models were used to examine the cholesterol-ABCA1-senescence pathways. Results Bulk and single nuclei transcriptomic profiling of the human dorsolateral prefrontal cortex from the Religious Order Study/Memory Aging Project (ROSMAP) revealed upregulation of cellular senescence transcriptome signatures in AD, which was strongly correlated with ABCA1 expression. Immunofluorescence and immunoblotting analyses confirmed increased ABCA1 expression in AD brain tissues, which was associated with lipofuscin-stained lipids and mTOR phosphorylation. Using discovery proteomics, caveolin-1, a sensor of cellular cholesterol accumulation, was identified to promote ABCA1 endolysosomal trafficking. Greater caveolin-1 expression was found in both APOE4-TR mouse models and AD human brains. Cholesterol induced mTORC1 activation was regulated by ABCA1 expression or its lysosomal trapping. Reducing cholesterol by cyclodextrin in APOE4-TR mice reduced ABCA1 lysosome trapping and increased ABCA1 recycling to efflux cholesterol to HDL particles, reducing mTORC1 activation and senescence-associated neuroinflammation. In human iPSC-derived astrocytes, the reduction of cholesterol by cyclodextrin attenuated inflammatory responses. Conclusions Cholesterol accumulation in APOE4 and AD induced caveolin-1 expression, which traps ABCA1 in lysosomes to activate mTORC1 pathways and induce cellular senescence. This study provided novel insights into how cholesterol accumulation in APOE4 and AD accelerates senescence.
    DOI:  https://doi.org/10.21203/rs.3.rs-4373201/v1
  32. J Biol Chem. 2024 May 27. pii: S0021-9258(24)01917-3. [Epub ahead of print] 107416
    CTCF and BORIS-mediated Autophagy regulation via Alternative splicing of BNIP3L in Breast Cancer.
    Anchala Pandey, Parik Kakani, Sanjeev Shukla.
      Autophagy is a pivotal regulatory and catabolic process, induced under various stressful conditions, including hypoxia. However, little is known about alternative splicing of autophagy genes in the hypoxic landscape in breast cancer. Our research unravels the hitherto unreported alternative splicing of BNIP3L, a crucial hypoxia-induced autophagic gene. We showed that BNIP3L, under hypoxic condition, forms two isoforms, a full-length isoform (BNIP3L-F) and a shorter isoform lacking exon 1 (BNIP3L-Δ1). The hypoxia-induced BNIP3L-F promotes autophagy, while under normoxia, the BNIP3L-Δ1 inhibits autophagy. We discovered a novel dimension of hypoxia-mediated epigenetic modification that regulates the alternative splicing of BNIP3L. Here, we showed differential DNA methylation of BNIP3L intron 1, causing reciprocal binding of epigenetic factor CTCF and its paralogue BORIS. Additionally, we highlighted the role of CTCF, and BORIS impacting autophagy in breast cancer. The differential binding of CTCF and BORIS results in alternative splicing of BNIP3L forming BNIP3L-F and BNIP3L-Δ1, respectively. The binding of CTCF on unmethylated BNIP3L intron 1 under hypoxia results in RNA Pol-II pause and inclusion of exon 1, promoting BNIP3L-F and autophagy. Interestingly, the binding of BORIS on methylated BNIP3L intron 1 under normoxia also results in RNA Pol-II pause but leads to the exclusion of exon 1 from BNIP3L mRNA. Finally, we reported the critical role of BORIS-mediated RNA Pol-II pause, which subsequently recruits SRSF6, redirecting the proximal splice-site selection, promoting BNIP3L-Δ1, and inhibiting autophagy. Our study provides novel insights into the potential avenues for breast cancer therapy by targeting autophagy regulation, specifically under hypoxic condition.
    Keywords:  BNIP3L-F; BNIP3L-Δ1; DNA methylation; Hypoxia; SRSF6
    DOI:  https://doi.org/10.1016/j.jbc.2024.107416
  33. Acta Neuropathol Commun. 2024 May 29. 12(1): 82
    Axonal autophagic vesicle transport in the rat optic nerve in vivo under normal conditions and during acute axonal degeneration.
    Xiaoyue Luo, Jiong Zhang, Johan Tolö, Sebastian Kügler, Uwe Michel, Mathias Bähr, Jan Christoph Koch.
      Neurons pose a particular challenge to degradative processes like autophagy due to their long and thin processes. Autophagic vesicles (AVs) are formed at the tip of the axon and transported back to the soma. This transport is essential since the final degradation of the vesicular content occurs only close to or in the soma. Here, we established an in vivo live-imaging model in the rat optic nerve using viral vector mediated LC3-labeling and two-photon-microscopy to analyze axonal transport of AVs. Under basal conditions in vivo, 50% of the AVs are moving with a majority of 85% being transported in the retrograde direction. Transport velocity is higher in the retrograde than in the anterograde direction. A crush lesion of the optic nerve results in a rapid breakdown of retrograde axonal transport while the anterograde transport stays intact over several hours. Close to the lesion site, the formation of AVs is upregulated within the first 6 h after crush, but the clearance of AVs and the levels of lysosomal markers in the adjacent axon are reduced. Expression of p150Glued, an adaptor protein of dynein, is significantly reduced after crush lesion. In vitro, fusion and colocalization of the lysosomal marker cathepsin D with AVs are reduced after axotomy. Taken together, we present here the first in vivo analysis of axonal AV transport in the mammalian CNS using live-imaging. We find that axotomy leads to severe defects of retrograde motility and a decreased clearance of AVs via the lysosomal system.
    Keywords:  Autophagy; Axonal transport; Axotomy; Dynactin; Optic nerve; p150Glued
    DOI:  https://doi.org/10.1186/s40478-024-01791-2
  34. Front Cell Infect Microbiol. 2024 ;14 1334211
    Hydatid fluid from Echinococcus granulosus induces autophagy in dendritic cells and promotes polyfunctional T-cell responses.
    Maia Chop, Camila Ledo, María Celeste Nicolao, Julia Loos, Andrea Cumino, Christian Rodriguez Rodrigues.
      Parasites possess remarkable abilities to evade and manipulate the immune response of their hosts. Echinococcus granulosus is a parasitic tapeworm that causes cystic echinococcosis in animals and humans. The hydatid fluid released by the parasite is known to contain various immunomodulatory components that manipulate host´s defense mechanism. In this study, we focused on understanding the effect of hydatid fluid on dendritic cells and its impact on autophagy induction and subsequent T cell responses. Initially, we observed a marked downregulation of two C-type lectin receptors in the cell membrane, CLEC9A and CD205 and an increase in lysosomal activity, suggesting an active cellular response to hydatid fluid. Subsequently, we visualized ultrastructural changes in stimulated dendritic cells, revealing the presence of macroautophagy, characterized by the formation of autophagosomes, phagophores, and phagolysosomes in the cell cytoplasm. To further elucidate the underlying molecular mechanisms involved in hydatid fluid-induced autophagy, we analyzed the expression of autophagy-related genes in stimulated dendritic cells. Our results demonstrated a significant upregulation of beclin-1, atg16l1 and atg12, indicating the induction of autophagy machinery in response to hydatid fluid exposure. Additionally, using confocal microscopy, we observed an accumulation of LC3 in dendritic cell autophagosomes, confirming the activation of this catabolic pathway associated with antigen presentation. Finally, to evaluate the functional consequences of hydatid fluid-induced autophagy in DCs, we evaluated cytokine transcription in the splenocytes. Remarkably, a robust polyfunctional T cell response, with inhibition of Th2 profile, is characterized by an increase in the expression of il-6, il-10, il-12, tnf-α, ifn-γ and tgf-β genes. These findings suggest that hydatid fluid-induced autophagy in dendritic cells plays a crucial role in shaping the subsequent T cell responses, which is important for a better understanding of host-parasite interactions in cystic echinococcosis.
    Keywords:  C-type lectin receptors; Echinococcus granulosus; T cell responses; autophagy; dendritic cells; hydatid fluid
    DOI:  https://doi.org/10.3389/fcimb.2024.1334211
  35. Biochim Biophys Acta Mol Cell Res. 2024 May 28. pii: S0167-4889(24)00108-3. [Epub ahead of print] 119765
    HRD1-mediated ubiquitination of HDAC2 regulates PPARα-mediated autophagy and alleviates metabolic-associated fatty liver disease.
    Yina Wang, Yuanguo Chen, Xiao Xiao, Silei Deng, Jingjie Kuang, Yayong Li.
      BACKGROUND: Metabolic-associated fatty liver disease (MAFLD) is a leading cause of chronic liver disease worldwide. Autophagy plays a pivotal role in lipid metabolism; however, the mechanism underlying the reduced autophagic activity in MAFLD remains elusive.METHODS: Autophagy was monitored by TUNEL assay and immunofluorescence staining of LC3. The expression of autophagy-related proteins, PPARα, HDAC2, and HRD1 was detected by Western blot. The association between HDAC2 and PPARα promoter was assessed by chromatin immunoprecipitation (ChIP) and dual-luciferase assays, and the HRD1-mediated ubiquitin-proteasomal degradation of HDAC2 was detected by co-immunoprecipitation (co-IP). The in vitro findings were validated in a hypoxia-induced MAFLD mouse model. Histological changes, fibrosis, and apoptosis in liver tissues were detected by hematoxylin and eosin staining, Masson's trichrome staining, and TUNEL assay. The immunoreactivities of key molecules were examined by IHC analysis.
    RESULTS: Hypoxia-suppressed autophagy in hepatocytes. Hypoxic exposure downregulated HRD1 and PPARα, while upregulating HDAC2 in hepatocytes. Overexpression of PPARα promoted hepatic autophagy, while knocking down HDAC2 or overexpressing HRD1 reduced hypoxia-suppressed autophagy in hepatocytes. Mechanistically, HDAC2 acted as a transcriptional repressor of PPARα, and HRD1 mediated the degradation of HDAC2 through the ubiquitin-proteasome pathway. Functional studies further showed that hypoxia-suppressed hepatic autophagy via the HRD1/HDAC2/PPARα axis in vitro and in vivo.
    CONCLUSION: HRD1-mediated ubiquitination of HDAC2 regulates PPARα-mediated autophagy and ameliorates hypoxia-induced MAFLD.
    Keywords:  Autophagy; HDAC2; HRD1; MAFLD; PPARα
    DOI:  https://doi.org/10.1016/j.bbamcr.2024.119765
  36. bioRxiv. 2024 May 15. pii: 2024.05.14.594211. [Epub ahead of print]
    The 18S rRNA Methyltransferase DIMT-1 Regulates Lifespan in the Germline Later in Life.
    M Hafiz Rothi, Gautam Chandra Sarkar, Joseph Al Haddad, Wayne Mitchell, Kejun Ying, Nancy Pohl, Roberto G Sotomayor-Mena, Julia Natale, Scarlett Dellacono, Vadim N Gladyshev, Eric Lieberman Greer.
      Ribosome heterogeneity has emerged as an important regulatory control feature for determining which proteins are synthesized, however, the influence of age on ribosome heterogeneity is not fully understood. Whether mRNA transcripts are selectively translated in young versus old cells and whether dysregulation of this process drives organismal aging is unknown. Here we examined the role of ribosomal RNA (rRNA) methylation in maintaining appropriate translation as organisms age. In a directed RNAi screen, we identified the 18S rRNA N6'-dimethyl adenosine (m 6,2 A) methyltransferase, dimt-1, as a regulator of C. elegans lifespan and stress resistance. Lifespan extension induced by dimt-1 deficiency required a functional germline and was dependent on the known regulator of protein translation, the Rag GTPase, raga- 1, which links amino acid sensing to the mechanistic target of rapamycin complex (mTORC)1. Using an auxin-inducible degron tagged version of dimt-1, we demonstrate that DIMT-1 functions in the germline after mid-life to regulate lifespan. We further found that knock-down of dimt-1 leads to selective translation of transcripts important for stress resistance and lifespan regulation in the C. elegans germline in mid-life including the cytochrome P450 daf-9, which synthesizes a steroid that signals from the germline to the soma to regulate lifespan. We found that dimt-1 induced lifespan extension was dependent on the daf-9 signaling pathway. This finding reveals a new layer of proteome dysfunction, beyond protein synthesis and degradation, as an important regulator of aging. Our findings highlight a new role for ribosome heterogeneity, and specific rRNA modifications, in maintaining appropriate translation later in life to promote healthy aging.
    DOI:  https://doi.org/10.1101/2024.05.14.594211
  37. Cell Death Dis. 2024 May 25. 15(5): 363
    Neuronal autosis is Na+/K+-ATPase alpha 3-dependent and involved in hypoxic-ischemic neuronal death.
    Pauline Depierre, Vanessa Ginet, Anita C Truttmann, Julien Puyal.
      Macroautophagy (hereafter called autophagy) is an essential physiological process of degradation of organelles and long-lived proteins. The discovery of autosis, a Na+/K+-ATPase (ATP1)-dependent type of autophagic cell death with specific morphological and biochemical features, has strongly contributed to the acceptance of a pro-death role of autophagy. However, the occurrence and relevance of autosis in neurons has never been clearly investigated, whereas we previously provided evidence that autophagy mechanisms could be involved in neuronal death in different in vitro and in vivo rodent models of hypoxia-ischemia (HI) and that morphological features of autosis were observed in dying neurons following rat perinatal cerebral HI. In the present study, we demonstrated that neuronal autosis could occur in primary cortical neurons using two different stimulations enhancing autophagy flux and neuronal death: a neurotoxic concentration of Tat-BECN1 (an autophagy-inducing peptide) and a hypoxic/excitotoxic stimulus (mimicking neuronal death induced by cerebral HI). Both stimulations induce autophagic neuronal death (dependent on canonical autophagic genes and independent on apoptotic, necroptotic or ferroptotic pathways) with all morphological and biochemical (ATP1a-dependent) features of autosis. However, we demonstrated that autosis is not dependent on the ubiquitous subunit ATP1a1 in neurons, as in dividing cell types, but on the neuronal specific ATP1a3 subunit. We also provided evidence that, in different in vitro and in vivo models where autosis is induced, ATP1a3-BECN1 interaction is increased and prevented by cardiac glycosides treatment. Interestingly, an increase in ATP1a3-BECN1 interaction is also detected in dying neurons in the autoptic brains of human newborns with severe hypoxic-ischemic encephalopathy (HIE). Altogether, these results suggest that ATP1a3-BECN1-dependent autosis could play an important role in neuronal death in HI conditions, paving the way for the development of new neuroprotective strategies in hypoxic-ischemic conditions including in severe case of human HIE.
    DOI:  https://doi.org/10.1038/s41419-024-06750-2
  38. Free Radic Biol Med. 2024 May 28. pii: S0891-5849(24)00498-2. [Epub ahead of print]221 235-244
    GSK-3α-BNIP3 axis promotes mitophagy in human cardiomyocytes under hypoxia.
    Hezlin Marzook, Anamika Gupta, Manju N Jayakumar, Mohamed A Saleh, Dhanendra Tomar, Rizwan Qaisar, Firdos Ahmad.
      Dysregulated autophagy/mitophagy is one of the major causes of cardiac injury in ischemic conditions. Glycogen synthase kinase-3alpha (GSK-3α) has been shown to play a crucial role in the pathophysiology of cardiac diseases. However, the precise role of GSK-3α in cardiac mitophagy remains unknown. Herein, we investigated the role of GSK-3α in cardiac mitophagy by employing AC16 human cardiomyocytes under the condition of acute hypoxia. We observed that the gain-of-GSK-3α function profoundly induced mitophagy in the AC16 cardiomyocytes post-hypoxia. Moreover, GSK-3α overexpression led to increased ROS generation and mitochondrial dysfunction in cardiomyocytes, accompanied by enhanced mitophagy displayed by increased mt-mKeima intensity under hypoxia. Mechanistically, we identified that GSK-3α promotes mitophagy through upregulation of BNIP3, caused by GSK-3α-mediated increase in expression of HIF-1α and FOXO3a in cardiomyocytes post-hypoxia. Moreover, GSK-3α displayed a physical interaction with BNIP3 and, inhibited PINK1 and Parkin recruitment to mitochondria was observed specifically under hypoxia. Taken together, we identified a novel mechanism of mitophagy in human cardiomyocytes. GSK-3α promotes mitochondrial dysfunction and regulates FOXO3a -mediated BNIP3 overexpression in cardiomyocytes to facilitate mitophagy following hypoxia. An interaction between GSK-3α and BNIP3 suggests a role of GSK-3α in BNIP3 recruitment to the mitochondrial membrane where it enhances mitophagy in stressed cardiomyocytes independent of the PINK1/Parkin.
    Keywords:  BNIP3; FOXO3a; GSK-3alpha; Mitophagy; PINK1; Parkin
    DOI:  https://doi.org/10.1016/j.freeradbiomed.2024.05.041
  39. Front Biosci (Landmark Ed). 2024 May 22. 29(5): 201
    Ibrutinib Contributes to Atrial Arrhythmia through the Autophagic Degradation of Connexins by Inhibiting the PI3K-AKT-mTOR Signaling Pathway.
    Huiyuan Qin, Bingyu Zheng, Zhiqiao Lin, Yumeng Ji, Cheng Wang, Huayuan Zhu, Chang Cui, Zidun Wang, Minglong Chen.
      BACKGROUND: Ibrutinib could increase the risk of atrial fibrillation (AF) in chronic lymphocytic leukemia (CLL) patients. However, the precise mechanism underlying ibrutinib-induced AF remains incompletely elucidated.METHODS: We investigated the proportion of ibrutinib-treated CLL patients with new-onset AF. Optical mapping was conducted to reveal the proarrhythmic effect of ibrutinib on HL-1 cells. Fluorescence staining and western blot were used to compare connexins 43 and 40 expression in ibrutinib-treated and control groups. To identify autophagy phenotypes, we used western blot to detect autophagy-related proteins, transmission electron microscopy to picture autophagosomes, and transfected mCherry-GFP-LC3 virus to label autophagosomes and lysosomes. Hydroxychloroquine as an autophagy inhibitor was administered to rescue ibrutinib-induced Cx43 and Cx40 degradation.
    RESULTS: About 2.67% of patients developed atrial arrhythmias after ibrutinib administration. HL-1 cells treated with ibrutinib exhibited diminished conduction velocity and a higher incidence of reentry-like arrhythmias compared to controls. Cx43 and Cx40 expression reduced along with autophagy markers increased in HL-1 cells treated with ibrutinib. Inhibiting autophagy upregulated Cx43 and Cx40.
    CONCLUSIONS: The off-target effect of ibrutinib on the PI3K-AKT-mTOR signaling pathway caused connexin degradation and atrial arrhythmia via promoting autophagy.
    CLINICAL TRIAL REGISTRATION: ChiCTR2100046062, https://clin.larvol.com/trial-detail/ChiCTR2100046062.
    Keywords:  atrial fibrillation; autophagy; connexins 40; connexins 43; ibrutinib
    DOI:  https://doi.org/10.31083/j.fbl2905201
  40. Cell Stress. 2024 ;8 56-58
    CircRNA regulates the liquid-liquid phase separation of ATG4B, a novel strategy to inhibit cancer metastasis?
    Ziyuan Guo, Yang Chen, Yaran Wu, Jiqin Lian.
      Anoikis is a common programmed death for most of detached cells, but cancer cells can obtain anoikis resistance to facilitate their distant metastasis through the circulation system. Researches have indicated that enhanced autophagic flux accounts for the survival of many cancer cells under detached conditions. Targeting ATG4B, the key factor of autophagy progress, can inhibit cancer metastasis in vitro, but ATG4B-deficient mice are susceptible to many serious diseases, which indicates the potential uncontrolled side effects of direct targeting of ATG4B. In our recent research, we confirmed that ATG4B is a novel RNA binding protein in the gastric cancer (GC) cell. It interacts with circSPECC1 which consequently facilitates the liquid-liquid phase separation and ubiquitination of ATG4B. Additionally, the m6A reader ELAVL1 inhibits the expression of circSPECC1 to enhance the expression of ATG4B and anoikis resistance of GC cells. Further, we screened out an FDA-approved compound, lopinavir, to restore circSPECC1 abundance and suppress GC metastasis. In conclusion, our research identified a novel signal pathway (ELAVL1-circSPECC1-ATG4B-autophagy) to facilitate anoikis resistance and metastasis of GC cells and screened out a compound with clinical application potential to block this pathway, providing a novel strategy for the prevention of GC metastasis.
    Keywords:  ATG4B; anoikis; autophagy; circSPECC1; liquid-liquid phase separation; lopinavir
    DOI:  https://doi.org/10.15698/cst2024.05.296
  41. Autophagy. 2024 May 31.
    Atg44/Mdi1/mitofissin facilitates Dnm1-mediated mitochondrial fission.
    Kentaro Furukawa, Manabu Hayatsu, Kentaro Okuyama, Tomoyuki Fukuda, Shun-Ichi Yamashita, Keiichi Inoue, Shinsuke Shibata, Tomotake Kanki.
      Mitochondria undergo fission and fusion, and their coordinated balance is crucial for maintaining mitochondrial homeostasis. In yeast, the dynamin-related protein Dnm1 is a mitochondrial fission factor acting from outside the mitochondria. We recently reported the mitochondrial intermembrane space protein Atg44/mitofissin/Mdi1/Mco8 as a novel fission factor, but the relationship between Atg44 and Dnm1 remains elusive. Here, we show that Atg44 is required to complete Dnm1-mediated mitochondrial fission under homeostatic conditions. Atg44-deficient cells often exhibit enlarged mitochondria with accumulated Dnm1 and rosary-like mitochondria with Dnm1 foci at constriction sites. These mitochondrial constriction sites retain the continuity of both the outer and inner membranes within an extremely confined space, indicating that Dnm1 is unable to complete mitochondrial fission without Atg44. Moreover, accumulated Atg44 proteins are observed at mitochondrial constriction sites. These findings suggest that Atg44 and Dnm1 cooperatively execute mitochondrial fission from inside and outside the mitochondria, respectively.
    Keywords:  Atg44; Dnm1; mitochondrial fission; mitofissin; mitophagy; yeast
    DOI:  https://doi.org/10.1080/15548627.2024.2360345
  42. Transl Oncol. 2024 May 24. pii: S1936-5233(24)00123-2. [Epub ahead of print]46 101996
    Regulatory feedback loop between circ-EIF4A3 and EIF4A3 Enhances autophagy and growth in colorectal cancer cells.
    Qingke Li, Zhiwu Wang, Jian Wang, Jiangong Wang, Xuan Zheng, Dan Li, Zhuo Wang, Jingwu Li, Yufeng Li.
      Recent studies indicate that circular RNAs (circRNAs) are crucial in the progression of colorectal cancer (CRC). Eukaryotic translation initiation factor 4A3 (EIF4A3) has been identified as a promoter of circRNA production. The biological roles and mechanisms of EIF4A3-derived circRNA (circEIF4A3) in CRC cell autophagy remain poorly understood. This study explores the effects of circEIF4A3 on CRC cell growth and autophagy, aiming to elucidate the underlying molecular mechanisms. We discovered that EIF4A3 and circEIF4A3 synergistically enhance CRC cell growth. CircEIF4A3 sequesters miR-3126-5p, consequently upregulating EIF4A3. Further, circEIF4A3 increases EIF4A3 expression, which promotes autophagy by stabilizing ATG5 mRNA and enhances ATG7 protein stability through the stabilization of USP14 mRNA, a deubiquitinating enzyme. Upregulation of ATG5 and ATG7 counteracts the growth-inhibitory effects of EIF4A3 knockdown on CRC cells. Moreover, our findings demonstrate that EIF4A3 induces the formation of circEIF4A3 in CRC cells. In conclusion, a positive feedback loop between circEIF4A3 and EIF4A3 supports CRC cell growth by facilitating autophagy.
    Keywords:  Autophagy; Colorectal cancer; EIF4A3; circEIF4A3
    DOI:  https://doi.org/10.1016/j.tranon.2024.101996
  43. Cell Rep. 2024 May 29. pii: S2211-1247(24)00621-1. [Epub ahead of print]43(6): 114293
    Pain hypersensitivity is dependent on autophagy protein Beclin 1 in males but not females.
    Theresa H Tam, Wenbo Zhang, YuShan Tu, Janice L Hicks, Sophia Farcas, Doyeon Kim, Michael W Salter.
      Chronic pain is associated with alterations in fundamental cellular processes. Here, we investigate whether Beclin 1, a protein essential for initiating the cellular process of autophagy, is involved in pain processing and is targetable for pain relief. We find that monoallelic deletion of Becn1 increases inflammation-induced mechanical hypersensitivity in male mice. However, in females, loss of Becn1 does not affect inflammation-induced mechanical hypersensitivity. In males, intrathecal delivery of a Beclin 1 activator, tat-beclin 1, reverses inflammation- and nerve injury-induced mechanical hypersensitivity and prevents mechanical hypersensitivity induced by brain-derived neurotrophic factor (BDNF), a mediator of inflammatory and neuropathic pain. Pain signaling pathways converge on the enhancement of N-methyl-D-aspartate receptors (NMDARs) in spinal dorsal horn neurons. The loss of Becn1 upregulates synaptic NMDAR-mediated currents in dorsal horn neurons from males but not females. We conclude that inhibition of Beclin 1 in the dorsal horn is critical in mediating inflammatory and neuropathic pain signaling pathways in males.
    Keywords:  BDNF; Beclin 1; CP: Cell biology; CP: Neuroscience; NMDA receptors; autophagy; pain; sex differences
    DOI:  https://doi.org/10.1016/j.celrep.2024.114293
  44. iScience. 2024 Jun 21. 27(6): 109870
    IGF2BP3 modified GLI2 transcriptionally regulates SYVN1 and facilitates sepsis liver injury through autophagy.
    Chuanzheng Sun, Min Gao, Haotian Hu, Jing Qi, Yishu Tang, Xiaoxue Cao, Runbang Zhang, Huaizheng Liu.
      Autophagy enhancement in septic liver injury can play a protective role. Nerveless, the mechanism of autophagy-mediated septic liver injury needs further investigation. Our study demonstrated that in septic condition, GLI Family Zinc Finger 2 (GLI2) was elevated, whereas peroxisome-proliferator-activated receptor α (PPARα) was downregulated. Suppressing GLI2 or synovialapoptosis inhibitor 1 (SYVN1) in LPS-exposed cells increased PPARα levels, enhanced cell viability and autophagy, while inhibiting apoptosis. LPS enhanced the GLI2-SYVN1 promoter binding. SYVN1 fostered ubiquitin-mediated degradation of PPARα. IGF2BP3 stabilized GLI2 mRNA by targeting its m6A site. Silencing IGF2BP3 led to decreased GLI2 and SYVN1 but increased PPARα levels, promoting cell survival and autophagy, while repressing apoptosis. This was counteracted by SYVN1 overexpression. In cecal ligation and puncture mice, IGF2BP3, SYVN1, or GLI2 knockdown ameliorated liver damage and augmented autophagy. In summary, IGF2BP3 enhanced GLI2 stability, overexpressed GLI2 subsequent promoted SYVN1 levels by interacting with its promoter, leading to ubiquitinated degradation of PPARα, thereby inhibiting PPARα-mediated autophagy and then exacerbating liver injury in sepsis.
    Keywords:  cell biology; hepatology; immunology
    DOI:  https://doi.org/10.1016/j.isci.2024.109870
  45. Neural Regen Res. 2025 Feb 01. 20(2): 366-377
    Age-related driving mechanisms of retinal diseases and neuroprotection by transcription factor EB-targeted therapy.
    Samuel Abokyi, Dennis Yan-Yin Tse.
      Retinal aging has been recognized as a significant risk factor for various retinal disorders, including diabetic retinopathy, age-related macular degeneration, and glaucoma, following a growing understanding of the molecular underpinnings of their development. This comprehensive review explores the mechanisms of retinal aging and investigates potential neuroprotective approaches, focusing on the activation of transcription factor EB. Recent meta-analyses have demonstrated promising outcomes of transcription factor EB-targeted strategies, such as exercise, calorie restriction, rapamycin, and metformin, in patients and animal models of these common retinal diseases. The review critically assesses the role of transcription factor EB in retinal biology during aging, its neuroprotective effects, and its therapeutic potential for retinal disorders. The impact of transcription factor EB on retinal aging is cell-specific, influencing metabolic reprogramming and energy homeostasis in retinal neurons through the regulation of mitochondrial quality control and nutrient-sensing pathways. In vascular endothelial cells, transcription factor EB controls important processes, including endothelial cell proliferation, endothelial tube formation, and nitric oxide levels, thereby influencing the inner blood-retinal barrier, angiogenesis, and retinal microvasculature. Additionally, transcription factor EB affects vascular smooth muscle cells, inhibiting vascular calcification and atherogenesis. In retinal pigment epithelial cells, transcription factor EB modulates functions such as autophagy, lysosomal dynamics, and clearance of the aging pigment lipofuscin, thereby promoting photoreceptor survival and regulating vascular endothelial growth factor A expression involved in neovascularization. These cell-specific functions of transcription factor EB significantly impact retinal aging mechanisms encompassing proteostasis, neuronal synapse plasticity, energy metabolism, microvasculature, and inflammation, ultimately offering protection against retinal aging and diseases. The review emphasizes transcription factor EB as a potential therapeutic target for retinal diseases. Therefore, it is imperative to obtain well-controlled direct experimental evidence to confirm the efficacy of transcription factor EB modulation in retinal diseases while minimizing its risk of adverse effects.
    DOI:  https://doi.org/10.4103/NRR.NRR-D-23-02033
  46. J Agric Food Chem. 2024 May 28.
    Genipin Activates Autophagy and Promotes Myoblast Differentiation by Activating AMPK Pathway.
    Jiaxin Li, Lianghua Xie, Zishan Dou, Yiyang Zhou, Jianling Mo, Wei Chen.
      Cultured meat technology is expected to solve problems such as resource shortages and environmental pollution, but the muscle fiber differentiation efficiency of cultured meat is low. Genipin is the active compound derived from Gardenia jasminoides Ellis, which has a variety of activities. Additionally, genipin serves as a noncytotoxic agent for cross-linking, which is suitable as a foundational scaffold for in vitro tissue regeneration. However, the impact of genipin on myoblast differentiation remains to be studied. The research revealed that genipin was found to improve the differentiation efficiency of myoblasts. Genipin improved mitochondrial membrane potential by activating the AMPK signaling pathway of myoblasts, promoting mitochondrial biogenesis, and mitochondrial network remodeling. Genipin activated autophagy in myoblasts and maintained cellular homeostasis. Autophagy inhibitors blocked the pro-differentiation effect of genipin. These results showed that genipin improved the differentiation efficiency of myoblasts, which provided a theoretical basis for the development of cultured meat technology.
    Keywords:  AMPK pathway; autophagy; genipin; myoblast differentiation
    DOI:  https://doi.org/10.1021/acs.jafc.3c06638
  47. FASEB J. 2024 May 31. 38(10): e23646
    Chaperone-mediated autophagy protects the bone formation from excessive inflammation through PI3K/AKT/GSK3β/β-catenin pathway.
    Kai Hang, YiBo Wang, JinWu Bai, ZhongXiang Wang, WeiLiang Wu, WeiWei Zhu, ShuangAi Liu, ZhiJun Pan, JianSong Chen, WenHao Chen.
      Multiple regulatory mechanisms are in place to ensure the normal processes of bone metabolism, encompassing both bone formation and absorption. This study has identified chaperone-mediated autophagy (CMA) as a critical regulator that safeguards bone formation from the detrimental effects of excessive inflammation. By silencing LAMP2A or HSCA8, we observed a hindrance in the osteoblast differentiation of human bone marrow mesenchymal stem cells (hBMSCs) in vitro. To further elucidate the role of LAMP2A, we generated LAMP2A gene knockdown and overexpression of mouse BMSCs (mBMSCs) using adenovirus. Our results showed that LAMP2A knockdown led to a decrease in osteogenic-specific proteins, while LAMP2A overexpression favored the osteogenesis of mBMSCs. Notably, active-β-catenin levels were upregulated by LAMP2A overexpression. Furthermore, we found that LAMP2A overexpression effectively protected the osteogenesis of mBMSCs from TNF-α, through the PI3K/AKT/GSK3β/β-catenin pathway. Additionally, LAMP2A overexpression significantly inhibited osteoclast hyperactivity induced by TNF-α. Finally, in a murine bone defect model, we demonstrated that controlled release of LAMP2A overexpression adenovirus by alginate sodium capsule efficiently protected bone healing from inflammation, as confirmed by imaging and histological analyses. Collectively, our findings suggest that enhancing CMA has the potential to safeguard bone formation while mitigating hyperactivity in bone absorption.
    Keywords:  BMSCs; CMA; HSCA8; LAMP2A; bone healing
    DOI:  https://doi.org/10.1096/fj.202302425R
  48. BMC Cardiovasc Disord. 2024 May 28. 24(1): 275
    SPAG5 deficiency activates autophagy to reduce atherosclerotic plaque formation in ApoE-/- mice.
    Liangyun Guo, Huijing Yuan, Huayao Zhu, Jie Zhou, Zixin Wan, Yihua Zhou.
      BACKGROUND: Autophagy, as a regulator of cell survival, plays an important role in atherosclerosis (AS). Sperm associated antigen 5 (SPAG5) is closely associated with the classical autophagy pathway, PI3K/Akt/mTOR signaling pathway. This work attempted to investigate whether SPAG5 can affect AS development by regulating autophagy.METHODS: Human umbilical vein endothelial cells (HUVECs) were treated with oxidized-low density lipoprotein (ox-LDL) to induce cell damage. ApoE-/- mice were fed a Western diet to establish an AS mouse model. Haematoxylin and eosin (H&E) staining and Oil Red O staining evaluated the pathological changes and in lipid deposition in aortic tissues. CCK-8 and flow cytometry detected cell proliferation and apoptosis. Immunohistochemistry, Enzyme linked immunosorbent assay, qRT-PCR and western blotting assessed the levels of mRNA and proteins.
    RESULTS: Ox-LDL treatment elevated SPAG5 expression and the expression of autophagy-related proteins, LC3-I, LC3-II, Beclin-1, and p62, in HUVECs. GFP-LC3 dots were increased in ox-LDL-treated HUVECs and LPS-treated HUVECs. SPAG5 knockdown reversed both ox-LDL and LPS treatment-mediated inhibition of cell proliferation and promotion of apoptosis in HUVECs. SPAG5 silencing further elevated autophagy and repressed the expression of PI3K, p-Akt/Akt, and p-mTOR/mTOR in ox-LDL-treated HUVECs. 3-MA (autophagy inhibitor) treatment reversed SPAG5 silencing-mediated increase of cell proliferation and decrease of apoptosis in ox-LDL-treated HUVECs. In vivo, SPAG5 knockdown reduced atherosclerotic plaques in AS mice through activating autophagy and inhibiting PI3K/Akt/mTOR signaling pathway.
    CONCLUSION: This work demonstrated that SPAG5 knockdown alleviated AS development through activating autophagy. Thus, SPAG5 may be a potential target for AS therapy.
    Keywords:  Atherosclerosis; Autophagy; PI3K/Akt/mTOR; SPAG5
    DOI:  https://doi.org/10.1186/s12872-024-03945-5
  49. Cell Death Differ. 2024 May 28.
    HSP70-mediated mitochondrial dynamics and autophagy represent a novel vulnerability in pancreatic cancer.
    Giulia D S Ferretti, Colleen E Quaas, Irene Bertolini, Alessandro Zuccotti, Ozge Saatci, Jennifer A Kashatus, Salma Sharmin, David Y Lu, Adi Narayana Reddy Poli, Abigail F Quesnelle, Jezabel Rodriguez-Blanco, Aguirre A de Cubas, G Aaron Hobbs, Qin Liu, John P O'Bryan, Joseph M Salvino, David F Kashatus, Ozgur Sahin, Thibaut Barnoud.
      Pancreatic ductal adenocarcinoma (PDAC), the most prevalent type of pancreatic cancer, is one of the deadliest forms of cancer with limited therapy options. Overexpression of the heat shock protein 70 (HSP70) is a hallmark of cancer that is strongly associated with aggressive disease and worse clinical outcomes. However, the underlying mechanisms by which HSP70 allows tumor cells to thrive under conditions of continuous stress have not been fully described. Here, we report that PDAC has the highest expression of HSP70 relative to normal tissue across all cancers analyzed. Furthermore, HSP70 expression is associated with tumor grade and is further enhanced in metastatic PDAC. We show that genetic or therapeutic ablation of HSP70 alters mitochondrial subcellular localization, impairs mitochondrial dynamics, and promotes mitochondrial swelling to induce apoptosis. Mechanistically, we find that targeting HSP70 suppresses the PTEN-induced kinase 1 (PINK1) mediated phosphorylation of dynamin-related protein 1 (DRP1). Treatment with the HSP70 inhibitor AP-4-139B was efficacious as a single agent in primary and metastatic mouse models of PDAC. In addition, we demonstrate that HSP70 inhibition promotes the AMP-activated protein kinase (AMPK) mediated phosphorylation of Beclin-1, a key regulator of autophagic flux. Accordingly, we find that the autophagy inhibitor hydroxychloroquine (HCQ) enhances the ability of AP-4-139B to mediate anti-tumor activity in vivo. Collectively, our results suggest that HSP70 is a multi-functional driver of tumorigenesis that orchestrates mitochondrial dynamics and autophagy. Moreover, these findings support the rationale for concurrent inhibition of HSP70 and autophagy as a novel therapeutic approach for HSP70-driven PDAC.
    DOI:  https://doi.org/10.1038/s41418-024-01310-9
  50. mBio. 2024 May 31. e0077124
    Capsule-deficient group A Streptococcus evades autophagy-mediated killing in macrophages.
    Yong-An Shi, Shiou-Ling Lu, Takeshi Noda, Cheng-Hsun Chiu, Chuan Chiang-Ni.
      The hyaluronic acid capsule is crucial in protecting group A Streptococcus (GAS) against phagocytic killing. However, there have been reported outbreaks caused by capsule-deficient GAS strains, and the mechanisms underlying their evasion of immune clearance remain unclear. This study demonstrated that the capsule-deficient mutant [Cap(-)] of the emm1 strain increased survival within phagocytic cells compared to the wild-type strain [Cap(+)]. Although both Cap(+) and Cap(-) strains exhibited similar abilities to disrupt the phagosome, only the Cap(+) strain was colocalized with lysosomes and acidified compartments in phagocytic cells, indicating its susceptibility to autophagosome elimination. In contrast, the Cap(-) mutant evaded the recognition of galectin-8 and ubiquitin, impairing selective autophagy-mediated elimination. These findings suggest that a deficiency in the capsule could impair the intracellular elimination of GAS in macrophages, revealing previously unknown aspects of the host's recognition of the GAS capsule in macrophages.IMPORTANCE: Group A Streptococcus (GAS) is a Gram-positive bacterium that causes diseases ranging from mild pharyngitis to severe necrotizing fasciitis. Phagocytic cells serve as the primary defense against bacterial infections, exhibiting remarkable efficiency in eliminating intracellular pathogens. The hyaluronic acid capsule is a critical virulence factor that contributes to the resistance of phagocytosis in GAS. Nevertheless, the outbreaks caused by GAS strains that lack the hyaluronic acid capsule have been reported, and the selective advantage of capsule-deficient strains during infection is not fully understood. This study showed that the autophagic adaptor proteins recognize the capsulated GAS strain but not the capsule-deficient mutant, indicating that the hyaluronic acid capsule could be the autophagic target in macrophages. These findings imply that the hyaluronic acid capsule of GAS actually enhances its elimination within phagocytic cells, subverting the understanding of the capsule in GAS pathogenesis.
    Keywords:  autophagy; group A Streptococcus; hyaluronic acid capsule; macrophages
    DOI:  https://doi.org/10.1128/mbio.00771-24
  51. Contact (Thousand Oaks). 2024 Jan-Dec;7:7 25152564241255782
    Spartin is a Lipid Transfer Protein That Facilitates Lipid Droplet Turnover.
    Yaoyang Zhong, Tim P Levine.
      One means by which cells reutilize neutral lipids stored in lipid droplets is to degrade them by autophagy. This process involves spartin, mutations of which cause the rare inherited disorder Troyer syndrome (or spastic paraplegia-20, SPG20). A recently published paper from the team led by Karin Reinsich (Yale) suggests that the molecular function of spartin and its unique highly conserved "senescence" domain is as a lipid transfer protein. Spartin binds to and transfers all lipid species found in lipid droplets, from phospholipids to triglycerides and sterol esters. This lipid transfer activity correlates with spartin's ability to sustain lipid droplet turnover. The senescence domain poses an intriguing question around the wide range of its cargoes, but intriguingly it has yet to yield up its secrets because attempts at crystallization failed and AlphaFold's prediction is unconvincing.
    Keywords:  autophagy; lipophagy; lysophagy; membrane contact sites; spastin
    DOI:  https://doi.org/10.1177/25152564241255782
  52. Plant Cell. 2024 May 27. pii: koae158. [Epub ahead of print]
    A viral small interfering RNA-host plant mRNA pathway modulates virus-induced drought tolerance by enhancing autophagy.
    Xinyang Wu, Shuting Chen, Zixin Zhang, Weixin Zhou, Ting Sun, Kang Ning, Min Xu, Xubo Ke, Pei Xu.
      Virus-induced drought tolerance presents a fascinating facet of biotic-abiotic interaction in plants, yet its molecular intricacies remain unclear. Our study shows that cowpea mild mottle virus (CPMMV) infection enhances drought tolerance in common bean (Phaseolus vulgaris) plants through a virus-derived small interfering RNA (vsiRNA)-activated autophagy pathway. Specifically, a 21-bp vsiRNA originating from the CPMMV Triple Gene Block1 (TGB1) gene targeted the 5' untranslated region (UTR) of the host Teosinte branched 1, Cycloidea, Proliferating Cell Factor (TCP) transcription factor gene PvTCP2, independent of the known role of TGB1 as an RNA silencing suppressor. This targeting attenuated the expression of PvTCP2, which encodes a transcriptional repressor, and in turn upregulated the core autophagy-related gene (ATG) PvATG8c, leading to activated autophagy activity surpassing the level induced by drought or CPMMV infection alone. The downstream EARLY RESPONSIVE TO DEHYDRATION (ERD) effector PvERD15 is a homologue of Arabidopsis thaliana AtERD15, which positively regulates stomatal aperture. PvERD15 was degraded in PvATG8c-mediated autophagy. Therefore, we establish a TGB1-PvTCP2-PvATG8c-PvERD15 module as a trans-kingdom fine-tuning mechanism that contributes to virus-induced drought tolerance in plant-drought-virus interactions.
    Keywords:  Autophagy; CPMMV; Common bean; Drought tolerance; TCP transcription factor; vsiRNA
    DOI:  https://doi.org/10.1093/plcell/koae158
  53. Front Cell Neurosci. 2024 ;18 1298182
    mTOR pathway inhibition alters proliferation as well as differentiation of neural stem cells.
    Nataliya Romanyuk, Kristyna Sintakova, Ivan Arzhanov, Martin Horak, Chirag Gandhi, Meena Jhanwar-Uniyal, Pavla Jendelova.
      Introduction: Neural stem cells (NSCs) are essential for both embryonic development and adult neurogenesis, and their dysregulation causes a number of neurodevelopmental disorders, such as epilepsy and autism spectrum disorders. NSC proliferation and differentiation in the developing brain is a complex process controlled by various intrinsic and extrinsic stimuli. The mammalian target of rapamycin (mTOR) regulates proliferation and differentiation, among other cellular functions, and disruption in the mTOR pathway can lead to severe nervous system development deficits. In this study, we investigated the effect of inhibition of the mTOR pathway by rapamycin (Rapa) on NSC proliferation and differentiation.Methods: The NSC cultures were treated with Rapa for 1, 2, 6, 24, and 48 h. The effect on cellular functions was assessed by immunofluorescence staining, western blotting, and proliferation/metabolic assays.
    Results: mTOR inhibition suppressed NSC proliferation/metabolic activity as well as S-Phase entry by as early as 1 h of Rapa treatment and this effect persisted up to 48 h of Rapa treatment. In a separate experiment, NSCs were differentiated for 2 weeks after treatment with Rapa for 24 or 48 h. Regarding the effect on neuronal and glial differentiation (2 weeks post-treatment), this was suppressed in NSCs deficient in mTOR signaling, as evidenced by downregulated expression of NeuN, MAP2, and GFAP. We assume that the prolonged effect of mTOR inhibition is realized due to the effect on cytoskeletal proteins.
    Discussion: Here, we demonstrate for the first time that the mTOR pathway not only regulates NSC proliferation but also plays an important role in NSC differentiation into both neuronal and glial lineages.
    Keywords:  cytoskeletal proteins; differentiation; mTOR; neural stem cells; proliferation
    DOI:  https://doi.org/10.3389/fncel.2024.1298182
  54. Dev Cell. 2024 May 22. pii: S1534-5807(24)00321-6. [Epub ahead of print]
    VAMP2 controls murine epidermal differentiation and carcinogenesis by regulation of nucleophagy.
    Han Liu, Peihong Su, Yuanyuan Li, Alex Hoover, Sophie Hu, Sarah A King, Jing Zhao, Jun-Lin Guan, Shao-Yu Chen, Yingming Zhao, Minjia Tan, Xiaoyang Wu.
      Differentiation of murine epidermal stem/progenitor cells involves the permanent withdrawal from the cell cycle, the synthesis of various protein and lipid components for the cornified envelope, and the controlled dissolution of cellular organelles and nuclei. Deregulated epidermal differentiation contributes to the development of various skin diseases, including skin cancers. With a genome-wide shRNA screen, we identified vesicle-associated membrane protein 2 (VAMP2) as a critical factor involved in skin differentiation. Deletion of VAMP2 leads to aberrant skin stratification and enucleation in vivo. With quantitative proteomics, we further identified an autophagy protein, focal adhesion kinase family interacting protein of 200 kDa (FIP200), as a binding partner of VAMP2. Additionally, we showed that both VAMP2 and FIP200 are critical for murine keratinocyte enucleation and epidermal differentiation. Loss of VAMP2 or FIP200 enhances cutaneous carcinogenesis in vivo. Together, our findings identify important molecular mechanisms underlying epidermal differentiation and skin tumorigenesis.
    Keywords:  autophagy; differentiation; epidermal progenitor cells; skin; squamous cell carcinoma
    DOI:  https://doi.org/10.1016/j.devcel.2024.05.004
  55. Sci Adv. 2024 May 31. 10(22): eadk9681
    HSDL2 links nutritional cues to bile acid and cholesterol homeostasis.
    Nolwenn Samson, Cristina R Bosoi, Christian Roy, Laurie Turcotte, Laura Tribouillard, Mathilde Mouchiroud, Line Berthiaume, Jocelyn Trottier, Heitor C G Silva, Thomas Guerbette, Ana Belén Plata-Gómez, Aurèle Besse-Patin, Alicia Montoni, Nicolò Ilacqua, Jennifer Lamothe, Yemima R Citron, Yves Gélinas, Stéphane Gobeil, Roberto Zoncu, Alexandre Caron, Mathieu Morissette, Luca Pellegrini, Patrick J Rochette, Jennifer L Estall, Alejo Efeyan, Michael Shum, Étienne Audet-Walsh, Olivier Barbier, André Marette, Mathieu Laplante.
      In response to energy and nutrient shortage, the liver triggers several catabolic processes to promote survival. Despite recent progress, the precise molecular mechanisms regulating the hepatic adaptation to fasting remain incompletely characterized. Here, we report the identification of hydroxysteroid dehydrogenase-like 2 (HSDL2) as a mitochondrial protein highly induced by fasting. We show that the activation of PGC1α-PPARα and the inhibition of the PI3K-mTORC1 axis stimulate HSDL2 expression in hepatocytes. We found that HSDL2 depletion decreases cholesterol conversion to bile acids (BAs) and impairs FXR activity. HSDL2 knockdown also reduces mitochondrial respiration, fatty acid oxidation, and TCA cycle activity. Bioinformatics analyses revealed that hepatic Hsdl2 expression positively associates with the postprandial excursion of various BA species in mice. We show that liver-specific HSDL2 depletion affects BA metabolism and decreases circulating cholesterol levels upon refeeding. Overall, our report identifies HSDL2 as a fasting-induced mitochondrial protein that links nutritional signals to BAs and cholesterol homeostasis.
    DOI:  https://doi.org/10.1126/sciadv.adk9681
  56. bioRxiv. 2024 May 17. pii: 2024.05.14.594256. [Epub ahead of print]
    Impact of long-term rapamycin treatment on age-related osteoarthritis in common marmoset.
    Dennis M Minton, Aditya R Ailiani, Michael D K Focht, Mariana E Kersh, Angela J Marolf, Kelly S Santangelo, Adam B Salmon, Adam R Konopka.
      Objective: Pharmacologic inhibition of the mechanistic target of rapamycin (mTOR) can attenuate experimental osteoarthritis (OA) in young, male preclinical models. However, the potential of mTOR inhibition as a therapeutic mechanism for OA remains unknown. The goal of this study was to determine if mTOR-inhibition by oral rapamycin can modify OA pathology in the common marmoset, a translational model of age-associated OA.Methods: microCT and histopathologic assessments of the knee were performed on formalin-fixed hindlimbs obtained from common marmosets treated with oral rapamycin (n=24; 1mg/kg/day) or parallel control group (n=41). Rapamycin started at 9.2±3.0 years old and lasted until death (2.1±1.5 years). In a subset of marmosets, contralateral hind limbs were collected to determine mTOR signaling in several joint tissues.
    Results: Rapamycin decreased P-RPS6 Ser235/36 and increased P-Akt2 Ser473 in cartilage, meniscus, and infrapatellar fat pad, suggesting inhibition of mTORC1 but not mTORC2 signaling. Rapamycin-treated marmosets had lower lateral synovium score versus control but there was no difference in the age-related increase in microCT or cartilage OA scores. Subchondral bone thickness and thickness variability were not different with age but were lower in rapamycin-treated geriatric marmosets, which was largely driven by females. Rapamycin also tended to worsen age-related meniscus calcification in female marmosets.
    Conclusion: Oral rapamycin attenuated mTORC1 signaling and may have caused feedback activation of mTORC2 signaling in joint tissues. Despite modifying site-specific aspects of synovitis, rapamycin did not modify the age-associated increase in OA in geriatric marmosets. Conversely, rapamycin may have had deleterious effects on meniscus calcification and lateral tibia subchondral bone, primarily in geriatric female marmosets.
    DOI:  https://doi.org/10.1101/2024.05.14.594256
  57. Autophagy. 2024 May 26.
    TMX2 potentiates cell viability of hepatocellular carcinoma by promoting autophagy and mitophagy.
    Weiyu Zhang, Yao Tang, Pengfei Yang, Yutong Chen, Zhijie Xu, Chunhui Qi, Hongbin Huang, Ruiyang Liu, Haorui Qin, Haoying Ke, Caini Huang, Fuyuan Xu, Pengfei Pang, Zhiju Zhao, Hong Shan, Fei Xiao.
      The dysregulation of membrane protein expression has been implicated in tumorigenesis and progression, including hepatocellular carcinoma (HCC). In this study, we aimed to identify membrane proteins that modulate HCC viability. To achieve this, we performed a CRISPR activation screen targeting human genes encoding membrane-associated proteins, revealing TMX2 as a potential driver of HCC cell viability. Gain- and loss-of-function experiments demonstrated that TMX2 promoted growth and tumorigenesis of HCC. Clinically, TMX2 was an independent prognostic factor for HCC patients. It was significantly upregulated in HCC tissues and associated with poor prognosis of HCC patients. Mechanistically, TMX2 was demonstrated to promote macroautophagy/autophagy by facilitating KPNB1 nuclear export and TFEB nuclear import. In addition, TMX2 interacted with VDAC2 and VADC3, assisting in the recruitment of PRKN to defective mitochondria to promote cytoprotective mitophagy during oxidative stress. Most interestingly, HCC cells responded to oxidative stress by upregulating TMX2 expression and cell autophagy. Knockdown of TMX2 enhanced the anti-tumor effect of lenvatinib. In conclusion, our findings emphasize the pivotal role of TMX2 in driving the HCC cell viability by promoting both autophagy and mitophagy. These results suggest that TMX2 May serve as a prognostic marker and promising therapeutic target for HCC treatment.
    Keywords:  Autophagy; CRISPR activation screening; hepatocellular carcinoma (HCC); lenvatinib; thioredoxin related transmembrane protein 2
    DOI:  https://doi.org/10.1080/15548627.2024.2358732
  58. Life Sci Alliance. 2024 Aug;pii: e202402740. [Epub ahead of print]7(8):
    K48- and K63-linked ubiquitin chain interactome reveals branch- and length-specific ubiquitin interactors.
    Anita Waltho, Oliver Popp, Christopher Lenz, Lukas Pluska, Mahil Lambert, Volker Dötsch, Philipp Mertins, Thomas Sommer.
      The ubiquitin (Ub) code denotes the complex Ub architectures, including Ub chains of different lengths, linkage types, and linkage combinations, which enable ubiquitination to control a wide range of protein fates. Although many linkage-specific interactors have been described, how interactors are able to decode more complex architectures is not fully understood. We conducted a Ub interactor screen, in humans and yeast, using Ub chains of varying lengths, as well as homotypic and heterotypic branched chains of the two most abundant linkage types-lysine 48-linked (K48) and lysine 63-linked (K63) Ub. We identified some of the first K48/K63-linked branch-specific Ub interactors, including histone ADP-ribosyltransferase PARP10/ARTD10, E3 ligase UBR4, and huntingtin-interacting protein HIP1. Furthermore, we revealed the importance of chain length by identifying interactors with a preference for Ub3 over Ub2 chains, including Ub-directed endoprotease DDI2, autophagy receptor CCDC50, and p97 adaptor FAF1. Crucially, we compared datasets collected using two common deubiquitinase inhibitors-chloroacetamide and N-ethylmaleimide. This revealed inhibitor-dependent interactors, highlighting the importance of inhibitor consideration during pulldown studies. This dataset is a key resource for understanding how the Ub code is read.
    DOI:  https://doi.org/10.26508/lsa.202402740
This page is being maintained by Thomas Krichel. It was last updated on 2024‒06‒09 at 9:40.