bims-auttor Biomed News
on Autophagy and mTOR
Issue of 2023‒02‒19
fifty-five papers selected by
Viktor Korolchuk, Newcastle University
  1. Mechanistic Target of Rapamycin Complex 1: From a Nutrient Sensor to a Key Regulator of Metabolism and Health.
  2. SQSTM1 facilitates oocyte maturation through inducing ACLY degradation mediated by selective autophagy.
  3. Structural basis for ATG9A recruitment to the ULK1 complex in mitophagy initiation.
  4. Impaired autophagic-lysosomal fusion in Parkinson's patient midbrain neurons occurs through loss of ykt6 and is rescued by farnesyltransferase inhibition.
  5. The role of the mechanistic target of rapamycin complex 1 in the regulation of mitochondrial adaptation during skeletal muscle atrophy under denervation or calorie restriction in mice.
  6. Autophagy in synapse formation and brain wiring.
  7. The outer mitochondrial membrane protein TMEM11 demarcates spatially restricted BNIP3/BNIP3L-mediated mitophagy.
  8. Dysregulated autophagy: A key player in the pathophysiology of type 2 diabetes and its complications.
  9. Pharmacological vitamin C inhibits mTOR signaling and tumor growth by degrading Rictor and inducing HMOX1 expression.
  10. Recruiting the autophagy-lysosome pathway to engineered condensate-forming proteins.
  11. Association between autophagy and acute pancreatitis.
  12. The YAP1-TEAD axis promotes autophagy against intracellular Staphylococcus aureus in vitro.
  13. Sindbis virus is suppressed in the yellow fever mosquito Aedes aegypti by ATG-6/Beclin-1 mediated activation of autophagy.
  14. Torin1 restores proliferation rate in Charcot-Marie-Tooth disease type 2A cells harbouring MFN2 (mitofusin 2) mutation.
  15. Coupling of autophagy and the mitochondrial intrinsic apoptosis pathway modulates proteostasis and ageing in Caenorhabditis elegans.
  16. CTB-targeted protocells enhance ability of lanthionine ketenamine analogs to induce autophagy in motor neuron-like cells.
  17. Mitophagy: A promising therapeutic target for neuroprotection during aging and age-related diseases.
  18. Structural basis for mTORC1-dependent regulation of the lysosomal and autophagic transcription factor EB.
  19. Impairment of autophagy promotes human conjunctival fibrosis and pterygium occurrence via enhancing SQSTM1-NF-κB signaling pathway.
  20. CLU (clusterin) promotes mitophagic degradation of MSX2 through an AKT-DNM1L/Drp1 axis to maintain SOX2-mediated stemness in oral cancer stem cells.
  21. Dual function of Rab1A in secretion and autophagy: hypervariable domain dependence.
  22. Promoting TFEB nuclear localization with curcumin analog C1 attenuates sensory hair cell injury and delays age-related hearing loss in C57BL/6 mice.
  23. ERK1/2-dependent TSPO overactivation associates with the loss of mitophagy and mitochondrial respiration in ALS.
  24. Autophagy as a self-digestion signal in human cancers: Regulation by microRNAs in affecting carcinogenesis and therapy response.
  25. Porcine reproductive and respiratory syndrome virus degrades DDX10 via SQSTM1/p62-dependent selective autophagy to antagonize its antiviral activity.
  26. Methods to detect AUTOphagy-Targeting Chimera (AUTOTAC)-mediated Targeted Protein Degradation in Tauopathies.
  27. Rooibos tea-in the cross fire of ROS, mitochondrial dysfunction and loss of proteostasis-positioned for healthy aging.
  28. Regulation of autophagy and lipid accumulation under phosphate limitation in Rhodotorula toruloides.
  29. Mitochondrial quality control and its role in osteoporosis.
  30. Deletion of Arrb2 down-regulates autophagy in the mouse hippocampus via Akt-mTOR pathway activation.
  31. HOPS-dependent lysosomal fusion controls Rab19 availability for ciliogenesis in polarized epithelial cells.
  32. A dual-activity topoisomerase complex promotes both transcriptional activation and repression in response to starvation.
  33. Spatial proteomics reveals secretory pathway disturbances caused by neuropathy-associated TECPR2.
  34. Reduced secretion of LCN2 (lipocalin 2) from reactive astrocytes through autophagic and proteasomal regulation alleviates inflammatory stress and neuronal damage.
  35. Adipocyte autophagy limits gut inflammation by controlling oxylipin and IL-10.
  36. Cone photoreceptors transfer damaged mitochondria to Müller glia.
  37. TFEB-vacuolar ATPase signaling regulates lysosomal function and microglial activation in tauopathy.
  38. Silencing MYOT Expression May Inhibit Autophagy in Human Skeletal Muscle Cells.
  39. BAG3 regulates the specificity of the recognition of specific MAPT species by NBR1 and SQSTM1.
  40. Cellular transformation promotes the incorporation of docosahexaenoic acid into the endolysosome-specific lipid bis(monoacylglycerol)phosphate in breast cancer.
  41. Toward effective Atg8-based ATTECs: Approaches and perspectives.
  42. Neuronal endoplasmic reticulum architecture and roles in axonal physiology.
  43. ox-LDL induces autophagy-mediated apoptosis by suppressing secretagogin-regulated autophagic flux in pancreatic β-cells.
  44. Narirutin activates TFEB (transcription factor EB) to protect against acetaminophen-induced liver injury by targeting PPP3/calcineurin.
  45. Dual functions of dynamin in beta cell endocytosis and autophagy trafficking as a membrane fission molecule.
  46. Mitochondrial quality control in acute kidney disease.
  47. Targeting Unc51-like Autophagy Activating Kinase 1 (ULK1) overcomes adaptive drug resistance in acute myelogenous leukemia.
  48. Rational design and appraisal of selective Cdc2-Like kinase 1 (Clk1) inhibitors as novel autophagy inducers for the treatment of acute liver injury (ALI).
  49. Autophagy and necroptosis in cisplatin-induced acute kidney injury: Recent advances regarding their role and therapeutic potential.
  50. IL-17A regulates autophagy and promotes osteoclast differentiation through the ERK/mTOR/Beclin1 pathway.
  51. Hyperactive neuronal autophagy depletes BDNF and impairs adult hippocampal neurogenesis in a corticosterone-induced mouse model of depression.
  52. Autophagy and its role in osteosarcoma.
  53. The nutrient-responsive CDK Pho85 primes the Sch9 kinase for its activation by TORC1.
  54. Ethyl pyruvate protects SHSY5Y cells against 6-hydroxydopamine-induced neurotoxicity by upregulating autophagy.
  55. Lysosomal exocytosis releases pathogenic α-synuclein species from neurons.
  1. Adv Nutr. 2022 Sep;pii: S2161-8313(23)00046-7. [Epub ahead of print]13(5): 1882-1900
    Mechanistic Target of Rapamycin Complex 1: From a Nutrient Sensor to a Key Regulator of Metabolism and Health.
    Guoyan Wang, Lei Chen, Senlin Qin, Tingting Zhang, Junhu Yao, Yanglei Yi, Lu Deng.
      Mechanistic target of rapamycin complex 1 (mTORC1) is a multi-protein complex widely found in eukaryotes. It serves as a central signaling node to coordinate cell growth and metabolism by sensing diverse extracellular and intracellular inputs, including amino acid-, growth factor-, glucose-, and nucleotide-related signals. It is well documented that mTORC1 is recruited to the lysosomal surface, where it is activated and, accordingly, modulates downstream effectors involved in regulating protein, lipid, and glucose metabolism. mTORC1 is thus the central node for coordinating the storage and mobilization of nutrients and energy across various tissues. However, emerging evidence indicated that the overactivation of mTORC1 induced by nutritional disorders leads to the occurrence of a variety of metabolic diseases, including obesity and type 2 diabetes, as well as cancer, neurodegenerative disorders, and aging. That the mTORC1 pathway plays a crucial role in regulating the occurrence of metabolic diseases renders it a prime target for the development of effective therapeutic strategies. Here, we focus on recent advances in our understanding of the regulatory mechanisms underlying how mTORC1 integrates metabolic inputs as well as the role of mTORC1 in the regulation of nutritional and metabolic diseases.
    Keywords:  mTORC1; metabolic diseases; metabolism; nutrient; signal transduction
    DOI:  https://doi.org/10.1093/advances/nmac055
  2. Cell Cycle. 2023 Feb 14. 1-3
    SQSTM1 facilitates oocyte maturation through inducing ACLY degradation mediated by selective autophagy.
    Heide Schatten.
      Selective autophagy specifically eliminates certain intracellular substrates through the autophagy pathway. Organelles and aggregation-prone proteins can be degraded through the autophagy receptor protein SQSTM1/p62, which renders them a promising therapeutic approach against infertility. He et al. demonstrate that blocking of autophagy in cumulus granulosa cells can directly attenuate citrate levels and in turn affect oocyte maturation quality. Further findings show that SQSTM1 connects K63-polyubiquitinated ACLY (ATP citrate lyase) during the process of selective autophagic degradation, which further compromises the homeostasis of citrate. Therefore, the quality of oocyte meiotic maturation can be evaluated by the levels of selective autophagy in cumulus granulosa cells.
    Keywords:  ACLY; Sqstm1/P62; citrate; meiotic resumption; selective autophagy
    DOI:  https://doi.org/10.1080/15384101.2023.2176673
  3. Sci Adv. 2023 Feb 15. 9(7): eadg2997
    Structural basis for ATG9A recruitment to the ULK1 complex in mitophagy initiation.
    Xuefeng Ren, Thanh N Nguyen, Wai Kit Lam, Cosmo Z Buffalo, Michael Lazarou, Adam L Yokom, James H Hurley.
      The assembly of the autophagy initiation machinery nucleates autophagosome biogenesis, including in the PINK1- and Parkin-dependent mitophagy pathway implicated in Parkinson's disease. The structural interaction between the sole transmembrane autophagy protein, autophagy-related protein 9A (ATG9A), and components of the Unc-51-like autophagy activating kinase (ULK1) complex is one of the major missing links needed to complete a structural map of autophagy initiation. We determined the 2.4-Å x-ray crystallographic structure of the ternary structure of ATG9A carboxyl-terminal tail bound to the ATG13:ATG101 Hop1/Rev7/Mad2 (HORMA) dimer, which is part of the ULK1 complex. We term the interacting portion of the extreme carboxyl-terminal part of the ATG9A tail the "HORMA dimer-interacting region" (HDIR). This structure shows that the HDIR binds to the HORMA domain of ATG101 by β sheet complementation such that the ATG9A tail resides in a deep cleft at the ATG13:ATG101 interface. Disruption of this complex in cells impairs damage-induced PINK1/Parkin mitophagy mediated by the cargo receptor NDP52.
    DOI:  https://doi.org/10.1126/sciadv.adg2997
  4. J Neurosci. 2023 Feb 13. pii: JN-RM-0610-22. [Epub ahead of print]
    Impaired autophagic-lysosomal fusion in Parkinson's patient midbrain neurons occurs through loss of ykt6 and is rescued by farnesyltransferase inhibition.
    Caleb Pitcairn, Naomi Murata, Annie Zalon, Iva Stojkovska, Joseph R Mazzulli.
      Macroautophagy is a catabolic process that coordinates with lysosomes to degrade aggregation-prone proteins and damaged organelles. Loss of macroautophagy preferentially affects neuron viability and is associated with age-related neurodegeneration. We previously found that a-synuclein (a-syn) inhibits lysosomal function by blocking ykt6, a farnesyl-regulated SNARE protein that is essential for hydrolase trafficking in midbrain neurons. Using Parkinson's disease (PD) patient iPSC-derived midbrain cultures, we find that chronic, endogenous accumulation of a-syn directly inhibits autophagosome-lysosome fusion by impairing ykt6-SNAP-29 complexes. In wild-type cultures, ykt6 depletion caused a near-complete block of autophagic flux, highlighting its critical role for autophagy in human iPSC-derived neurons. In PD, macroautophagy impairment was associated with increased farnesyltransferase (FTase) activity, and FTase inhibitors restored macroautophagic flux through promoting active forms of ykt6 in human cultures, and male and female mice. Our findings indicate that ykt6 mediates cellular clearance by coordinating autophagic-lysosomal fusion and hydrolase trafficking, and that macroautophagy impairment in PD can be rescued by FTase inhibitors.Significance Statement:The pathogenic mechanisms that lead to the death of neurons in Parkinson's disease (PD) and Dementia with Lewy bodies (LBD) is currently unknown. Furthermore, disease modifying treatments for these diseases do not exist. Our study indicates that a cellular clearance pathway termed autophagy is impaired in patient-derived culture models of PD and in vivo We identified a novel druggable target, a SNARE protein called ykt6, that rescues autophagy in vitro and in vivo upon blocking its farnesylation. Our work suggests that farnesyltransferase inhibitors may be useful therapies for PD and DLB through enhancing autophagic-lysosomal clearance of aggregated proteins.
    DOI:  https://doi.org/10.1523/JNEUROSCI.0610-22.2023
  5. Appl Physiol Nutr Metab. 2023 Feb 14.
    The role of the mechanistic target of rapamycin complex 1 in the regulation of mitochondrial adaptation during skeletal muscle atrophy under denervation or calorie restriction in mice.
    Kazuki Uemichi, Takanaga Shirai, Ryunosuke Matsuno, Tomohiro Iwata, Riku Tanimura, Tohru Takemasa.
      Mechanistic target of rapamycin complex 1 (mTORC1) is a protein complex that regulates skeletal muscle protein synthesis and hypertrophy. mTORC1-mediated signaling activities are activated during denervation-induced skeletal muscle atrophy and suppressed during calorie restriction-induced atrophy. Mitochondria control the qualitative plasticity of skeletal muscles primarily through biogenesis, fusion, and fission. We recently showed that mTORC1 activation contributes toward mitochondrial homeostasis. In this study, we examined the role of mTORC1 in mitochondrial adaptation during denervation- or calorie restriction-induced skeletal muscle atrophy. Seven-week-old Institute of Cancer Research mice were subjected to 14 days of denervation or calorie restriction combined with the administration of the mTORC1 inhibitor-"rapamycin". Our results showed that although mTORC1 inhibition did not alter mitochondrial biogenesis, content and enzyme activity, it suppressed the activation of dynamin-related protein 1 (DRP1), a mitochondrial fission-related protein in denervated muscle, and reduced DRP1 expression in calorie-restricted muscle. Furthermore, calorie restriction-induced mitochondrial fragmentation was partially suppressed by mTORC1 inhibition. Taken together, our results indicate that mTORC1 activation upon denervation and inhibition upon calorie restriction contributes to qualitative changes in muscle plasticity by at least partially regulating the mitochondrial fission response.
    Keywords:  mTORC1; mitochondrial dynamics; skeletal muscle atrophy
    DOI:  https://doi.org/10.1139/apnm-2022-0336
  6. Autophagy. 2023 Feb 13.
    Autophagy in synapse formation and brain wiring.
    Bassem A Hassan, P Robin Hiesinger.
      A recent characterization of the role of autophagy in two different neuron types during brain development in Drosophila revealed two different mechanisms to regulate synapse formation. In photoreceptor neurons, autophagosome formation in synaptogenic filopodia destabilizes presumptive synaptic contacts and thereby restricts incorrect synaptic partnerships. In dorsal cluster neurons, autophagy is actively suppressed to keep mature synapses stable during axonal branching. These findings indicate that different neuron types can require activation or suppression of synaptic autophagy during the same developmental period to ensure proper synapse formation and brain connectivity.
    Keywords:  active zone; brain development; filopodia; neuron; neuronal autophagy; synapse; synaptic autophagy; synaptogenesis
    DOI:  https://doi.org/10.1080/15548627.2023.2179778
  7. J Cell Biol. 2023 Apr 03. pii: e202204021. [Epub ahead of print]222(4):
    The outer mitochondrial membrane protein TMEM11 demarcates spatially restricted BNIP3/BNIP3L-mediated mitophagy.
    Mehmet Oguz Gok, Olivia M Connor, Xun Wang, Cameron J Menezes, Claire B Llamas, Prashant Mishra, Jonathan R Friedman.
      Mitochondria play critical roles in cellular metabolism and to maintain their integrity, they are regulated by several quality control pathways, including mitophagy. During BNIP3/BNIP3L-dependent receptor-mediated mitophagy, mitochondria are selectively targeted for degradation by the direct recruitment of the autophagy protein LC3. BNIP3 and/or BNIP3L are upregulated situationally, for example during hypoxia and developmentally during erythrocyte maturation. However, it is not well understood how they are spatially regulated within the mitochondrial network to locally trigger mitophagy. Here, we find that the poorly characterized mitochondrial protein TMEM11 forms a complex with BNIP3 and BNIP3L and co-enriches at sites of mitophagosome formation. We find that mitophagy is hyper-active in the absence of TMEM11 during both normoxia and hypoxia-mimetic conditions due to an increase in BNIP3/BNIP3L mitophagy sites, supporting a model that TMEM11 spatially restricts mitophagosome formation.
    DOI:  https://doi.org/10.1083/jcb.202204021
  8. Biochim Biophys Acta Mol Basis Dis. 2023 Feb 13. pii: S0925-4439(23)00032-7. [Epub ahead of print] 166666
    Dysregulated autophagy: A key player in the pathophysiology of type 2 diabetes and its complications.
    Abhishek Sehrawat, Jayapriya Mishra, Sarabjit Singh Mastana, Umashanker Navik, Gurjit Kaur Bhatti, P Hemachandra Reddy, Jasvinder Singh Bhatti.
      Autophagy is essential in regulating the turnover of macromolecules via removing damaged organelles, misfolded proteins in various tissues, including liver, skeletal muscles, and adipose tissue to maintain the cellular homeostasis. In these tissues, a specific type of autophagy maintains the accumulation of lipid droplets which is directly related to obesity and the development of insulin resistance. It appears to play a protective role in a normal physiological environment by eliminating the invading pathogens, protein aggregates, and damaged organelles and generating energy and new building blocks by recycling the cellular components. Ageing is also a crucial modulator of autophagy process. During stress conditions involving nutrient deficiency, lipids excess, hypoxia etc., autophagy serves as a pro-survival mechanism by recycling the free amino acids to maintain the synthesis of proteins. The dysregulated autophagy has been found in several ageing associated diseases including type 2 diabetes (T2DM), cancer, and neurodegenerative disorders. So, targeting autophagy can be a promising therapeutic strategy against the progression to diabetes related complications. Our article provides a comprehensive outline of understanding of the autophagy process, including its types, mechanisms, regulation, and role in the pathophysiology of T2DM and related complications. We also explored the significance of autophagy in the homeostasis of β-cells, insulin resistance (IR), clearance of protein aggregates such as islet amyloid polypeptide, and various insulin-sensitive tissues. This will further pave the way for developing novel therapeutic strategies for diabetes-related complications.
    Keywords:  Autophagy; ER stress; Insulin resistance; Type 2 diabetes; microRNAs
    DOI:  https://doi.org/10.1016/j.bbadis.2023.166666
  9. PLoS Genet. 2023 Feb;19(2): e1010629
    Pharmacological vitamin C inhibits mTOR signaling and tumor growth by degrading Rictor and inducing HMOX1 expression.
    Senlin Qin, Guoyan Wang, Lei Chen, Huijun Geng, Yining Zheng, Chao Xia, Shengru Wu, Junhu Yao, Lu Deng.
      Pharmacological vitamin C (VC) is a potential natural compound for cancer treatment. However, the mechanism underlying its antitumor effects remains unclear. In this study, we found that pharmacological VC significantly inhibits the mTOR (including mTORC1 and mTORC2) pathway activation and promotes GSK3-FBXW7-mediated Rictor ubiquitination and degradation by increasing the cellular ROS. Moreover, we identified that HMOX1 is a checkpoint for pharmacological-VC-mediated mTOR inactivation, and the deletion of FBXW7 or HMOX1 suppresses the regulation of pharmacological VC on mTOR activation, cell size, cell viability, and autophagy. More importantly, it was observed that the inhibition of mTOR by pharmacological VC supplementation in vivo produces positive therapeutic responses in tumor growth, while HMOX1 deficiency rescues the inhibitory effect of pharmacological VC on tumor growth. These results demonstrate that VC influences cellular activities and tumor growth by inhibiting the mTOR pathway through Rictor and HMOX1, which may have therapeutic potential for cancer treatment.
    DOI:  https://doi.org/10.1371/journal.pgen.1010629
  10. Biophys J. 2023 Feb 10. pii: S0006-3495(22)03511-1. [Epub ahead of print]122(3S1): 485a
    Recruiting the autophagy-lysosome pathway to engineered condensate-forming proteins.
    Mateo P Hoare, Daniel Mcilwaine, Tin Long Chris Ng, Luisa Capalbo, Ellis J Wilde, Laura S Itzhaki, Janet R Kumita.
      
    DOI:  https://doi.org/10.1016/j.bpj.2022.11.2595
  11. Front Genet. 2023 ;14 998035
    Association between autophagy and acute pancreatitis.
    Tao Zhang, Yu Gan, Shuai Zhu.
      Autophagy pathway involves maintaining intracellular homeostasis by regulating the degradation of cytoplasmic components. Disfunction of autophagic process has been confirmed to be critical mechanism in many diseases, including cancer, inflammation, infection, degeneration and metabolic disorders. Recent studies have shown that autophagy is one of the early events in acute pancreatitis. Impaired autophagy promotes the abnormal activation of zymogen granules and results in apoptosis and necrosis of exocrine pancreas. Furthermore, multiple signal paths involve progression of acute pancreatitis by regulating autophagy pathway. This article provides a comprehensive review of the recent advances in epigenetic regulation of autophagy and the role of autophagy in acute pancreatitis.
    Keywords:  N6-methyladenosine; acute pancreatitis; advance; autophagy; mechanism
    DOI:  https://doi.org/10.3389/fgene.2023.998035
  12. Autophagy. 2023 Feb 13.
    The YAP1-TEAD axis promotes autophagy against intracellular Staphylococcus aureus in vitro.
    Robin Caire, Nicola Pordone, Paul O Verhoeven.
      Previously considered as an exclusive extracellular bacterium, Staphylococcus aureus has been shown to be able to invade many cells in vitro and in humans. Once inside the host cell, both cytosolic and endosome-associated S. aureus strongly induce macroautophagy/autophagy. Whether autophagy fosters S. aureus intracellular survival or clearance remains unclear. The YAP1-TEAD axis regulates the expression of target genes controlling the cell fate (e.g., proliferation, migration, cell cycle …). Growing evidence indicates that YAP1-TEAD also regulates autophagy and lysosomal pathways. Recently we showed that the YAP1-TEAD axis promotes autophagy and lysosome biogenesis to restrict S. aureus intracellular replication. We also discovered that the C3 exoenzyme-like EDIN-B toxin produced by the pathogenic S. aureus ST80 strain inhibits YAP1 nuclear translocation resulting in a strong increase of intracellular S. aureus burden.
    Keywords:  Autophagy; C3 exoenzyme; EDIN; Staphylococcus aureus; YAP; cell-autonomous immunity; host response genes; inflammation; lysosome
    DOI:  https://doi.org/10.1080/15548627.2023.2179771
  13. bioRxiv. 2023 Feb 02. pii: 2023.02.02.526867. [Epub ahead of print]
    Sindbis virus is suppressed in the yellow fever mosquito Aedes aegypti by ATG-6/Beclin-1 mediated activation of autophagy.
    Sujit Pujhari, Chan C Heu, Marco Brustolin, Rebecca M Johnson, Donghun Kim, Jason L Rasgon.
      Autophagy is a critical modulator of pathogen invasion response in vertebrates and invertebrates. However, how it affects mosquito-borne viral pathogens that significantly burden public health remains underexplored. To address this gap, we use a genetic approach to activate macroautophagy/autophagy in the yellow fever mosquito ( Aedes aegypti ), infected with a recombinant Sindbis virus (SINV) expressing an autophagy activator. We first demonstrate a 17- amino acid peptide derived from the Ae. aegypti autophagy-related protein 6 (ATG-6/beclin-1-like protein) is sufficient to induce autophagy in C6/36 mosquito cells, as marked by lipidation of ATG- 8 and puncta formation. Next, we engineered a recombinant SINV expressing this bioactive beclin- 1-like peptide and used it to infect and induce autophagy in adult mosquitoes. We find that modulation of autophagy using this recombinant SINV negatively regulated production of infectious viruses. The results from this study improve our understanding of the role of autophagy in arboviruses in invertebrate hosts and also highlight the potential for the autophagy pathway to be exploited for arboviral control.
    DOI:  https://doi.org/10.1101/2023.02.02.526867
  14. Acta Myol. 2022 ;41(4): 201-206
    Torin1 restores proliferation rate in Charcot-Marie-Tooth disease type 2A cells harbouring MFN2 (mitofusin 2) mutation.
    Paola Zanfardino, Alessandro Amati, Easter Anna Petracca, Filippo M Santorelli, Vittoria Petruzzella.
      Objective: Mitofusin 2 (MFN2) is a mitochondrial outer membrane protein that serves primarily as a mitochondrial fusion protein but has additional functions including the tethering of mitochondrial-endoplasmic reticulum membranes, movement of mitochondria along axons, and control of the quality of mitochondria. Intriguingly, MFN2 has been referred to play a role in regulating cell proliferation in several cell types such that it acts as a tumour suppressor role in some forms of cancer. Previously, we found that fibroblasts derived from a Charcot-Marie-Tooth disease type 2A (CMT2A) patient with a mutation in the GTPase domain of MFN2 exhibit increased proliferation and decreased autophagy.Methods: Primary fibroblasts from a young patient affected by CMT2A harbouring c.650G > T/p.Cys217Phe mutation in the MFN2 gene were evaluated versus a healthy control to measure the proliferation rate by growth curves analysis and to assess the phosphorylation of protein kinase B (AKT) at Ser473 in response to different doses of torin1, a selective catalytic ATP-competitive mammalian target of rapamycin complex (mTOR) inhibitor, by immunoblot analysis.
    Results: Herein, we demonstrated that the mammalian target of rapamycin complex 2 (mTORC2) is highly activated in the CMT2AMFN2 fibroblasts to promote cell growth via the AKT(Ser473) phosphorylation-mediated signalling. We report that torin1 restores CMT2AMFN2 fibroblasts' growth rate in a dose-dependent manner by decreasing AKT(Ser473) phosphorylation.
    Conclusions: Overall, our study provides evidence for mTORC2, as a novel molecular target that lies upstream of AKT to restore the cell proliferation rate in CMT2A fibroblasts.
    Keywords:  AKT; Charcot-Marie-Tooth type 2A2; cell proliferation; mTORC2; mitofusin2
    DOI:  https://doi.org/10.36185/2532-1900-085
  15. Cell Death Dis. 2023 Feb 11. 14(2): 110
    Coupling of autophagy and the mitochondrial intrinsic apoptosis pathway modulates proteostasis and ageing in Caenorhabditis elegans.
    Christina Ploumi, Emmanouil Kyriakakis, Nektarios Tavernarakis.
      Mitochondria preserve metabolic homeostasis and integrate stress signals, to trigger cytoprotective, or cell death pathways. Mitochondrial homeostasis and function decline with age. The mechanisms underlying the deterioration of mitochondrial homeostasis during ageing, or in age-associated pathologies, remain unclear. Here, we show that CISD-1, a mitochondrial iron-sulfur cluster binding protein, implicated in the pathogenesis of Wolfram neurodegenerative syndrome type 2, modulates longevity in the nematode Caenorhabditis elegans by engaging autophagy and the mitochondrial intrinsic apoptosis pathway. The anti-apoptotic protein CED-9 is the downstream effector that mediates CISD-1-dependent effects on proteostasis, neuronal integrity and lifespan. Moreover, intracellular iron abundance is critical for CISD-1 function, since mild iron supplementation is sufficient to decelerate ageing and partly ameliorate the disturbed mitochondrial bioenergetics and proteostasis of CISD-1 deficient animals. Our findings reveal that CISD-1 serves as a mechanistic link between autophagy and the apoptotic pathway in mitochondria to differentially modulate organismal proteostasis and ageing, and suggest novel approaches which could facilitate the treatment of Wolfram Syndrome or related diseases.
    DOI:  https://doi.org/10.1038/s41419-023-05638-x
  16. Sci Rep. 2023 Feb 13. 13(1): 2581
    CTB-targeted protocells enhance ability of lanthionine ketenamine analogs to induce autophagy in motor neuron-like cells.
    Maria A Gonzalez Porras, Heather M Gransee, Travis T Denton, Dunxin Shen, Kevin L Webb, C Jeffrey Brinker, Achraf Noureddine, Gary C Sieck, Carlos B Mantilla.
      Impaired autophagy, a cellular digestion process that eliminates proteins and damaged organelles, has been implicated in neurodegenerative diseases, including motor neuron disorders. Motor neuron targeted upregulation of autophagy may serve as a promising therapeutic approach. Lanthionine ketenamine (LK), an amino acid metabolite found in mammalian brain tissue, activates autophagy in neuronal cell lines. We hypothesized that analogs of LK can be targeted to motor neurons using nanoparticles to improve autophagy flux. Using a mouse motor neuron-like hybrid cell line (NSC-34), we tested the effect of three different LK analogs on autophagy modulation, either alone or loaded in nanoparticles. For fluorescence visualization of autophagy flux, we used a mCherry-GFP-LC3 plasmid reporter. We also evaluated protein expression changes in LC3-II/LC3-I ratio obtained by western blot, as well as presence of autophagic vacuoles per cell obtained by electron microscopy. Delivering LK analogs with targeted nanoparticles significantly enhanced autophagy flux in differentiated motor neuron-like cells compared to LK analogs alone, suggesting the need of a delivery vehicle to enhance their efficacy. In conclusion, LK analogs loaded in nanoparticles targeting motor neurons constitute a promising treatment option to induce autophagy flux, which may serve to mitigate motor neuron degeneration/loss and preserve motor function in motor neuron disease.
    DOI:  https://doi.org/10.1038/s41598-023-29437-8
  17. Br J Pharmacol. 2023 Feb 15.
    Mitophagy: A promising therapeutic target for neuroprotection during aging and age-related diseases.
    Ela Mishra, Mahendra Kumar Thakur.
      Mitochondria and mitochondria-mediated signaling pathways are known to control synaptic signaling as well as long-lasting changes in neuronal structure and function. Mitochondrial impairment is linked to synaptic dysfunction in normal aging and age-associated neurodegenerative ailments including Parkinson's disease (PD) and Alzheimer's disease (AD). Both proteolysis and mitophagy perform a major role in neuroprotection by maintaining a healthy mitochondrial population during aging. Mitophagy, a highly evolutionarily conserved cellular process, helps in the clearance of damaged mitochondria and thereby maintains the mitochondrial and metabolic balance, energy supply, neuronal survival, and neuronal health. Besides the maintenance of brain homeostasis, hippocampal mitophagy also helps in synapse formation, axonal development, dopamine release, and long-term depression. In contrast, defective mitophagy contributes to aging and age-related neurodegeneration by promoting the accumulation of damaged mitochondria leading to cellular dysfunction. Exercise, stress management, maintaining healthy mitochondrial dynamics, and administering natural or synthetic pharmacological compounds are some of the strategies used for neuroprotection during aging and age-related neurological diseases. The current review discusses the impact of defective mitophagy in aging and age-associated neurodegenerative conditions, the underlying molecular pathways, and potential therapies based on recently elucidated mitophagy-inducing strategies.
    Keywords:  Aging; Mitochondrial dysfunction; Mitophagy; Neurodegeneration; Pharmacological compounds; Therapeutic interventions
    DOI:  https://doi.org/10.1111/bph.16062
  18. Biophys J. 2023 Feb 10. pii: S0006-3495(22)02651-0. [Epub ahead of print]122(3S1): 308a
    Structural basis for mTORC1-dependent regulation of the lysosomal and autophagic transcription factor EB.
    Zhicheng Cui, James H Hurley.
      
    DOI:  https://doi.org/10.1016/j.bpj.2022.11.1735
  19. J Mol Cell Biol. 2023 Feb 15. pii: mjad009. [Epub ahead of print]
    Impairment of autophagy promotes human conjunctival fibrosis and pterygium occurrence via enhancing SQSTM1-NF-κB signaling pathway.
    Qin He, Yiting Cai, Jiani Huang, Xiaoying He, Wei Han, Wei Chen.
      Pterygium is a common ocular disease with high recurrence rate, characterized by hyperplasia of subconjunctival fibrovascular tissue. Autophagy, the important process to maintain cellular homeostasis, participates the pathogenic fibrosis of different organs. However, the exact role of autophagy in pterygium pathogenesis remains unknown. Here we found that autophagic activity was decreased in human pterygium tissues compared with adjacent normal conjunctival tissues. The in vitro model of fibrosis was successfully established using human primary conjunctival fibroblasts (ConFB) treated with TGF-β1, evidenced by increased fibrotic level and strong proliferative and invasive capability. The autophagic activity was suppressed during TGF-β1 or ultraviolet-induced fibrosis of ConFB. Activating autophagy dramatically retarded the fibrotic progress of ConFB, while blocking autophagy exacerbated this process. Furthermore, SQSTM1, the main cargo receptor of selective autophagy, was found to significantly promote the fibrosis of ConFB through activating PKCι-NF-κB signaling pathway. Knockdown of SQSTM1, PKCι, or p65 in ConFB delayed the TGF-β1-induced fibrosis. Over-expression of SQSTM1 drastically abrogated the inhibitory effect of rapamycin or serum starvation on the TGF-β1-induced fibrosis. Collectively, our data suggested that autophagy impairment of human ConFB facilitates fibrosis via activating SQSTM1-PKCι-NF-κB signaling cascades. This work was contributory to elucidating the mechanism of autophagy underlying pterygium occurrence.
    Keywords:  NF-κB; SQSTM1; autophagy; fibrosis; pterygium
    DOI:  https://doi.org/10.1093/jmcb/mjad009
  20. Autophagy. 2023 Feb 13.
    CLU (clusterin) promotes mitophagic degradation of MSX2 through an AKT-DNM1L/Drp1 axis to maintain SOX2-mediated stemness in oral cancer stem cells.
    Prakash P Praharaj, Srimanta Patra, Soumya R Mishra, Subhadip Mukhopadhyay, Daniel J Klionsky, Shankargouda Patil, Sujit K Bhutia.
      Mitophagy regulates cancer stem cell (CSC) populations affecting tumorigenicity and malignancy in various cancer types. Here, we report that cisplatin treatment led to the activation of higher mitophagy through regulating CLU (clusterin) levels in oral CSCs. Moreover, both the gain-of-function and loss-of-function of CLU indicated its mitophagy-specific role in clearing damaged mitochondria. CLU also regulates mitochondrial fission by activating the Ser/Thr kinase AKT, which triggered phosphorylation of DNM1L/DRP1 at the serine 616 residue initiating mitochondrial fission. More importantly, we also demonstrated that CLU-mediated mitophagy positively regulates oral CSCs through mitophagic degradation of MSX2 (msh homeobox 2), preventing its nuclear translocation from suppressing SOX2 activity and subsequent inhibition of cancer stemness and self-renewal ability. However, CLU knockdown disturbed mitochondrial metabolism generating excessive mitochondrial superoxide, which improves the sensitivity to cisplatin in oral CSCs. Notably, our results showed that CLU-mediated cytoprotection relies on SOX2 expression. SOX2 inhibition through genetic (shSOX2) and pharmacological (KRX-0401) strategies reverses CLU-mediated cytoprotection, sensitizing oral CSCs towards cisplatin-mediated cell death.
    Keywords:  Cancer stem cells; MSX2; SOX2; clusterin; mitophagy
    DOI:  https://doi.org/10.1080/15548627.2023.2178876
  21. Life Sci Alliance. 2023 May;pii: e202201810. [Epub ahead of print]6(5):
    Dual function of Rab1A in secretion and autophagy: hypervariable domain dependence.
    Valeriya Gyurkovska, Rakhilya Murtazina, Sarah F Zhao, Sojin Shikano, Yukari Okamoto, Nava Segev.
      We currently understand how the different intracellular pathways, secretion, endocytosis, and autophagy are regulated by small GTPases. In contrast, it is unclear how these pathways are coordinated to ensure efficient cellular response to stress. Rab GTPases localize to specific organelles through their hypervariable domain (HVD) to regulate discrete steps of individual pathways. Here, we explored the dual role of Rab1A/B (92% identity) in secretion and autophagy. We show that although either Rab1A or Rab1B is required for secretion, Rab1A, but not Rab1B, localizes to autophagosomes and is required early in stress-induced autophagy. Moreover, replacing the HVD of Rab1B with that of Rab1A enables Rab1B to localize to autophagosomes and regulate autophagy. Therefore, Rab1A-HVD is required for the dual functionality of a single Rab in two different pathways: secretion and autophagy. In addition to this mechanistic insight, these findings are relevant to human health because both the pathways and Rab1A/B were implicated in diseases ranging from cancer to neurodegeneration.
    DOI:  https://doi.org/10.26508/lsa.202201810
  22. Neurotoxicology. 2023 Feb 13. pii: S0161-813X(23)00024-4. [Epub ahead of print]
    Promoting TFEB nuclear localization with curcumin analog C1 attenuates sensory hair cell injury and delays age-related hearing loss in C57BL/6 mice.
    Wuhui He, Fan Wu, Hao Xiong, Junbo Zeng, Yiming Gao, Ziyi Cai, Jiaqi Pang, Yiqing Zheng.
      Sensory hair cell (HC) injuries, especially outer hair cell (OHC) loss, are well-documented to be the primary pathology of age-related hearing loss (AHL). Recent studies have demonstrated that autophagy plays an important role in HC injury in the inner ear. In our previous works, a decline in autophagy levels and HC loss were found to occur simultaneously in the inner ears of aged C57BL/6 mice, and the administration of rapamycin promoted autophagy levels, which reduced OHC loss and delayed AHL, but the underlying mechanism of autophagy in AHL has not been well elucidated. Transcription factor EB (TFEB), an autophagy regulator and the downstream target of mammalian target of rapamycin (mTOR), is involved in the pathological development of neurodegenerative disease. This study would address the link between autophagy and TFEB in aged C57BL/6 mouse cochleae and clarify the effect of the TFEB activator curcumin analog C1 (C1) in aged cochleae. Decreased TFEB nuclear localization (p = 0.0371) and autophagy dysfunction (p = 0.0273) were observed in the cochleae of aged C57BL/6 mice that exhibited AHL, HCs loss and HCs senescence. Treatment with C1 promoted TFEB nuclear localization and restored autophagy, subsequently alleviating HC injury and delaying AHL. The protective effect of C1 on HEI-OC1 cells against autophagy disorder and aging induced by D-galactose was abolished by chloroquine, which is one of the commonly used autophagy inhibitors. Overall, our results demonstrated that the capacity to perform autophagy is mediated by the nuclear localization of TFEB in aged C57BL/6 mouse cochleae. C1 promotes the nuclear localization of TFEB, subsequently alleviating HC injury and delaying AHL by restoring the impaired autophagy function. TFEB may serve as a new therapeutic target for AHL treatment.
    Keywords:  Age-related hearing loss; Autophagy; Curcumin analog C1; Hair cell; Transcription factor EB (TFEB)
    DOI:  https://doi.org/10.1016/j.neuro.2023.02.004
  23. Cell Death Dis. 2023 Feb 15. 14(2): 122
    ERK1/2-dependent TSPO overactivation associates with the loss of mitophagy and mitochondrial respiration in ALS.
    Andrea Magrì, Cristiana Lucia Rita Lipari, Pierpaolo Risiglione, Stefania Zimbone, Francesca Guarino, Antonella Caccamo, Angela Messina.
      Mitochondrial dysfunction and the loss of mitophagy, aimed at recycling irreversibly damaged organelles, contribute to the onset of amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease affecting spinal cord motor neurons. In this work, we showed that the reduction of mitochondrial respiration, exactly oxygen flows linked to ATP production and maximal capacity, correlates with the appearance of the most common ALS motor symptoms in a transgenic mouse model expressing SOD1 G93A mutant. This is the result of the equal inhibition in the respiration linked to complex I and II of the electron transport chain, but not their protein levels. Since the overall mitochondrial mass was unvaried, we investigated the expression of the Translocator Protein (TSPO), a small mitochondrial protein whose overexpression was recently linked to the loss of mitophagy in a model of Parkinson's disease. Here we clearly showed that levels of TSPO are significantly increased in ALS mice. Mechanistically, this increase is linked to the overactivation of ERK1/2 pathway and correlates with a decrease in the expression of the mitophagy-related marker Atg12, indicating the occurrence of impairments in the activation of mitophagy. Overall, our work sets out TSPO as a key regulator of mitochondrial homeostasis in ALS.
    DOI:  https://doi.org/10.1038/s41419-023-05643-0
  24. Pharmacol Res. 2023 Feb 11. pii: S1043-6618(23)00051-8. [Epub ahead of print] 106695
    Autophagy as a self-digestion signal in human cancers: Regulation by microRNAs in affecting carcinogenesis and therapy response.
    Mustafa M Kadhim, Andrés Alexis Ramírez-Coronel, Abduladheem Turki Jalil, Hayder Abdullah Talib, Jitendra Gupta, Zanko Hassan Jawhar, Mawan Mahmood Saleh, Vijay Pandey, Xi Zhang, Haroon Khan.
      Autophagy is defined as a "self-digestion" signal, and it is a cell death mechanism its primary function is degrading toxic agents and aged organelles to ensure homeostasis in cells. The basic leve ls of autophagy are found in cells, and when its levels exceed to standard threshold, cell death induction is observed. Autophagy dysregulation in cancer has been well-documented, and regulation of this pathway by epigenetic factors, especially microRNAs (miRNAs), is interesting and noteworthy. miRNAs are considered short endogenous RNAs that do not encode functional proteins, and they are essential regulators of cell death pathways such as apoptosis, necroptosis, and autophagy. Accumulating data has revealed miRNA dysregulation (upregulation or downregulation) during tumor progression, and their therapeutic manipulation provides new insight into cancer therapy. miRNA/autophagy axis in human cancers has been investigated an exciting point is the dual function of both autophagy and miRNAs as oncogenic and onco-suppressor factors. The stimulation of pro-survival autophagy by miRNAs can increase the survival rate of tumor cells and mediates cancer metastasis via EMT inductionFurthermore, pro-death autophagy induction by miRNAs has a negative impact on the viability of tumor cells and decreases their survival rate. The miRNA/autophagy axis functions beyond regulating the growth and invasion of tumor cells, and they can also affect drug resistance and radio-resistance. These subjects are covered in the current review regarding the new updates provided by recent experiments.
    Keywords:  autophagy; miRNA; non-coding RNAs; therapy resistance; tumor progression
    DOI:  https://doi.org/10.1016/j.phrs.2023.106695
  25. Autophagy. 2023 Feb 13.
    Porcine reproductive and respiratory syndrome virus degrades DDX10 via SQSTM1/p62-dependent selective autophagy to antagonize its antiviral activity.
    Jia Li, Yanrong Zhou, Wenkai Zhao, Jiao Liu, Rizwan Ullah, Puxian Fang, Liurong Fang, Shaobo Xiao.
      Porcine reproductive and respiratory syndrome virus (PRRSV) is a typical immunosuppressive virus that has been devastating the global swine industry for over three decades. DEAD-box helicases (DDXs) are a family of ATP-dependent RNA helicases that are predominantly implicated in modulating cellular RNA metabolism. Meanwhile, a growing number of studies have suggested that some DDXs are associated with innate immunity and virus infection, so they are considered potential antiviral targets. Herein, we screened 40 DDXs and found that ectopic expression of DDX10 exhibited a significant anti-PRRSV effect, while DDX10 knockdown promoted PRRSV proliferation. Further analysis revealed that DDX10 positively regulates type I interferon production, which may contribute to its anti-PRRSV effect. Interestingly, PRRSV infection promoted DDX10 translocation from the nucleus to the cytoplasm for macroautophagic/autophagic degradation to block the antiviral effect of DDX10. By screening PRRSV-encoded proteins, we found that the viral envelope (E) protein interacted with DDX10. In line with the autophagic degradation of DDX10 during PRRSV infection, E protein could induce autophagy and reduce DDX10 expression in wild-type cells, but not in ATG5 or ATG7 knockout (KO) cells. When further screening the cargo receptors for autophagic degradation, we found that SQSTM1/p62 (sequestosome 1) interacted with both DDX10 and E protein, and E protein-mediated DDX10 degradation was almost entirely blocked in SQSTM1 KO cells, demonstrating that E protein degrades DDX10 by promoting SQSTM1-mediated selective autophagy. Our study reveals a novel mechanism by which PRRSV escapes host antiviral innate immunity through selective autophagy, providing a new target for developing anti-PRRSV drugs.
    Keywords:  DDX10; E protein; PRRSV; SQSTM1/p62; innate immunity; selective autophagy; type I interferon
    DOI:  https://doi.org/10.1080/15548627.2023.2179844
  26. Bio Protoc. 2023 Jan 20. 13(2): e4594
    Methods to detect AUTOphagy-Targeting Chimera (AUTOTAC)-mediated Targeted Protein Degradation in Tauopathies.
    Min Ju Lee, Su Bin Kim, Hee Yeon Kim, Su Jin Lee, Ji Su Lee, Yong Tae Kwon, Chang Hoon Ji.
      Targeted protein degradation (TPD) facilitates the selective elimination of unwanted and pathological cellular cargoes via the proteasome or the lysosome, ranging from proteins to organelles and pathogens, both within and outside the cell. Currently, there are several in vitro and in vivo protocols that assess the degradative potency of a given degrader towards a myriad of targets, most notably soluble, monomeric oncoproteins. However, there is a clear deficiency of methodologies to assess the degradative potency of heterobifunctional chimeric degraders, especially those in the autophagy space, against pathological, mutant tau species, such as detergent-insoluble oligomers and high-molecular aggregates. The protocol below describes both in vitro and in vivo biochemical assays to induce tau aggregation, as well as to qualitatively and quantitatively measure the degradative potency of a given degrader towards said aggregates, with specific applications of the AUTOTAC (AUTOphagy-TArgeting Chimera) platform provided as an example. A well-defined set of methodologies to assess TPD-mediated degradation of pathological tau species will help expand the scope of the TPD technology to neurodegeneration and other proteinopathies, in both the lab and the clinic. Graphical abstract Overview of assays observing elimination of tauP301L aggregates with AUTOTAC. (A) Description of the biological working mechanism of heterobifunctional chimeric AUTOTAC degraders. (B) Schematic illustration of assays described in this paper.
    Keywords:  AUTOTAC; Detergent-insoluble/soluble fractionation; Lysosomal acidification; TPD; hTauP301L-BiFC; in vivo oligomerization
    DOI:  https://doi.org/10.21769/BioProtoc.4594
  27. Biogerontology. 2023 Feb 13.
    Rooibos tea-in the cross fire of ROS, mitochondrial dysfunction and loss of proteostasis-positioned for healthy aging.
    Catherine Smit, Sholto De Wet, Tamryn Barron, Ben Loos.
      Impaired mitochondrial function and loss of cellular proteostasis control are key hallmarks of aging and are implicated in the development of neurodegenerative diseases. A common denominator is the cell's inability to handle reactive oxygen species (ROS), leading to major downstream oxidative damage that exacerbates neuronal dysfunction. Although we have progressed in understanding the molecular defects associated with neuronal aging, many unanswered questions remain. How much ROS is required to serve cellular function before it becomes detrimental and how does the cell's oxidative status impact mitochondrial function and protein degradation through autophagy? How does ROS regulate autophagy? Aspalathus linearis, also commonly known as rooibos, is an endemic South African plant that is gaining globally acclaim for its antioxidant properties and its role as functional medicinal beverage. In this article we dissect the role of rooibos in the context of the cell's ROS handling capacity, mitochondrial function and autophagy activity. By addressing the dynamic relationship between these critical interconnected systems, and by evaluating the functional properties of rooibos, we unravel its position for preserving cell viability and promoting healthy aging.
    Keywords:  Autophagy; Healthy aging; Mitochondrial function; Neurodegeneration; Oxidative damage; Rooibos tea
    DOI:  https://doi.org/10.1007/s10522-022-10012-z
  28. Front Microbiol. 2022 ;13 1046114
    Regulation of autophagy and lipid accumulation under phosphate limitation in Rhodotorula toruloides.
    Ya-Nan Wang, Fang-Jie Liu, Hong-di Liu, Yue Zhang, Xiang Jiao, Ming-Liang Ye, Zong-Bao Kent Zhao, Su-Fang Zhang.
      Background: It is known that autophagy is essential for cell survival under stress conditions. Inorganic phosphate (Pi) is an essential nutrient for cell growth and Pi-limitation can trigger autophagy and lipid accumulation in oleaginous yeasts, yet protein (de)-phosphorylation and related signaling events in response to Pi limitation and the molecular basis linking Pi-limitation to autophagy and lipid accumulation remain elusive.Results: Here, we compared the proteome and phosphoproteome of Rhodotorula toruloides CGMCC 2.1389 under Pi-limitation and Pi-repletion. In total, proteome analysis identified 3,556 proteins and the phosphoproteome analysis identified 1,649 phosphoproteins contained 5,659 phosphosites including 4,499 pSer, 978 pThr, and 182 pTyr. We found Pi-starvation-induced autophagy was regulated by autophagy-related proteins, but not the PHO pathway. When ATG9 was knocked down, the engineered strains produced significantly less lipids under Pi-limitation, suggesting that autophagy required Atg9 in R. toruloides and that was conducive to lipid accumulation.
    Conclusion: Our results provide new insights into autophagy regulation under Pi-limitation and lipid accumulation in oleaginous yeast, which should be valuable to guide further mechanistic study of oleaginicity and genetic engineering for advanced lipid producing cell factory.
    Keywords:  Atg9; Rhodotorula toruloides; autophagy; lipid accumulation; phosphate limitation
    DOI:  https://doi.org/10.3389/fmicb.2022.1046114
  29. Front Endocrinol (Lausanne). 2023 ;14 1077058
    Mitochondrial quality control and its role in osteoporosis.
    Chunlu Yan, Yao Shi, Lingqing Yuan, Donghui Lv, Bai Sun, Jiayu Wang, Xiyan Liu, Fangyu An.
      Mitochondria are important organelles that provide cellular energy and play a vital role in cell differentiation and apoptosis. Osteoporosis is a chronic metabolic bone disease mainly caused by an imbalance in osteoblast and osteoclast activity. Under physiological conditions, mitochondria regulate the balance between osteogenesis and osteoclast activity and maintain bone homeostasis. Under pathological conditions, mitochondrial dysfunction alters this balance; this disruption is important in the pathogenesis of osteoporosis. Because of the role of mitochondrial dysfunction in osteoporosis, mitochondrial function can be targeted therapeutically in osteoporosis-related diseases. This article reviews different aspects of the pathological mechanism of mitochondrial dysfunction in osteoporosis, including mitochondrial fusion and fission, mitochondrial biogenesis, and mitophagy, and highlights targeted therapy of mitochondria in osteoporosis (diabetes induced osteoporosis and postmenopausal osteoporosis) to provide novel targets and prevention strategies for the prevention and treatment of osteoporosis and other chronic bone diseases.
    Keywords:  mitochondrial autophagy; mitochondrial biogenesis; mitochondrial fusion and fission; osteoporosis; targeted therapy
    DOI:  https://doi.org/10.3389/fendo.2023.1077058
  30. Neuroscience. 2023 Feb 14. pii: S0306-4522(23)00042-8. [Epub ahead of print]
    Deletion of Arrb2 down-regulates autophagy in the mouse hippocampus via Akt-mTOR pathway activation.
    Qingyu Peng, Yamei Liu, Lele Yu, Yizhe Shen, Feng Li, Shini Feng, Fuxue Chen.
      The cytoplasmic multifunctional adaptor protein β-arrestin 2 (Arrb2) is involved in the occurrence of various nervous system diseases, such as Alzheimer's disease and Parkinson's disease. Previous laboratory studies have shown that the expression and function of the Arrb2 gene was increased in valproic acid-induced autistic mice models. However, few reports have examined the possible role of Arrb2 in the pathogenesis of autism spectrum disorder. Therefore, Arrb2-deficient (Arrb2-/-) mice were further studied to uncover the physiological function of Arrb2 in the nervous system. In this study, we found that Arrb2-/- mice had normal behavioral characteristics compared with wild-type mice. The autophagy marker protein LC3B was decreased in the hippocampus of Arrb2-/- mice compared to wild-type mice. Western blot analysis revealed that deletion of Arrb2 caused hyperactivation of Akt-mTOR signaling in the hippocampus. In addition, abnormal mitochondrial dysfunction was observed in Arrb2-/- hippocampal neurons, which was characterized by a reduction in mitochondrial membrane potential and adenosine triphosphate production and an increase in reactive oxygen species levels. Therefore, this study elucidates the interaction between Arrb2 and the Akt-mTOR signaling pathway and provides insights into the role of Arrb2 in hippocampal neuron autophagy.
    Keywords:  Akt-mTOR; Autophagy; Hippocampus; β-arrestin 2
    DOI:  https://doi.org/10.1016/j.neuroscience.2023.01.024
  31. bioRxiv. 2023 Feb 08. pii: 2023.02.07.527563. [Epub ahead of print]
    HOPS-dependent lysosomal fusion controls Rab19 availability for ciliogenesis in polarized epithelial cells.
    Huxley K Hoffman, Rytis Prekeris.
      Primary cilia are sensory cellular organelles crucial for organ development and homeostasis. Ciliogenesis in polarized epithelial cells requires Rab19-mediated clearing of apical cortical actin to allow the cilium to grow from the apically-docked basal body into the extracellular space. Loss of the lysosomal membrane-tethering HOPS complex disrupts this actin-clearing and ciliogenesis, but it remains unclear how ciliary function of HOPS relates to its canonical function in regulating late endosome-lysosome fusion. Here, we show that disruption of HOPS-dependent lysosomal fusion indirectly impairs actin-clearing and ciliogenesis by disrupting the targeting of Rab19 to the basal body. We also find that Rab19 functions in endolysosomal cargo trafficking apart from its previously-identified role in ciliogenesis. In summary, we show that inhibition of lysosomal fusion abnormally accumulates Rab19 on late endosomes, thus depleting Rab19 from the basal body and thereby disrupting Rab19-mediated actin-clearing and ciliogenesis.Summary statement: Loss of HOPS-mediated lysosomal fusion indirectly blocks apical actin clearing and ciliogenesis in polarized epithelia by trapping Rab19 on late endosomes and depleting Rab19 from the basal body.
    DOI:  https://doi.org/10.1101/2023.02.07.527563
  32. Nucleic Acids Res. 2023 Feb 16. pii: gkad086. [Epub ahead of print]
    A dual-activity topoisomerase complex promotes both transcriptional activation and repression in response to starvation.
    Shuaikun Su, Yutong Xue, Seung Kyu Lee, Yongqing Zhang, Jinshui Fan, Supriyo De, Alexei Sharov, Weidong Wang.
      Topoisomerases are required to release topological stress generated by RNA polymerase II (RNAPII) during transcription. Here, we show that in response to starvation, the complex of topoisomerase 3b (TOP3B) and TDRD3 can enhance not only transcriptional activation, but also repression, which mimics other topoisomerases that can also alter transcription in both directions. The genes enhanced by TOP3B-TDRD3 are enriched with long and highly-expressed ones, which are also preferentially stimulated by other topoisomerases, suggesting that different topoisomerases may recognize their targets through a similar mechanism. Specifically, human HCT116 cells individually inactivated for TOP3B, TDRD3 or TOP3B topoisomerase activity, exhibit similarly disrupted transcription for both starvation-activated genes (SAGs) and starvation-repressed genes (SRGs). Responding to starvation, both TOP3B-TDRD3 and the elongating form of RNAPII exhibit concomitantly increased binding to TOP3B-dependent SAGs, at binding sites that overlap. Notably, TOP3B inactivation decreases the binding of elongating RNAPII to TOP3B-dependent SAGs while increased it to SRGs. Furthermore, TOP3B-ablated cells display reduced transcription of several autophagy-associated genes and autophagy per se. Our data suggest that TOP3B-TDRD3 can promote both transcriptional activation and repression by regulating RNAPII distribution. In addition, the findings that it can facilitate autophagy may account for the shortened lifespan of Top3b-KO mice.
    DOI:  https://doi.org/10.1093/nar/gkad086
  33. Nat Commun. 2023 Feb 16. 14(1): 870
    Spatial proteomics reveals secretory pathway disturbances caused by neuropathy-associated TECPR2.
    Karsten Nalbach, Martina Schifferer, Debjani Bhattacharya, Hung Ho-Xuan, Wei Tseng, Luis A Williams, Alexandra Stolz, Stefan F Lichtenthaler, Zvulun Elazar, Christian Behrends.
      Hereditary sensory and autonomic neuropathy 9 (HSAN9) is a rare fatal neurological disease caused by mis- and nonsense mutations in the gene encoding for Tectonin β-propeller repeat containing protein 2 (TECPR2). While TECPR2 is required for lysosomal consumption of autophagosomes and ER-to-Golgi transport, it remains elusive how exactly TECPR2 is involved in autophagy and secretion and what downstream sequels arise from defective TECPR2 due to its involvement in these processes. To address these questions, we determine molecular consequences of TECPR2 deficiency along the secretory pathway. By employing spatial proteomics, we describe pronounced changes with numerous proteins important for neuronal function being affected in their intracellular transport. Moreover, we provide evidence that TECPR2's interaction with the early secretory pathway is not restricted to COPII carriers. Collectively, our systematic profiling of a HSAN9 cell model points to specific trafficking and sorting defects which might precede autophagy dysfunction upon TECPR2 deficiency.
    DOI:  https://doi.org/10.1038/s41467-023-36553-6
  34. Autophagy. 2023 Feb 13.
    Reduced secretion of LCN2 (lipocalin 2) from reactive astrocytes through autophagic and proteasomal regulation alleviates inflammatory stress and neuronal damage.
    Byung-Kwon Jung, Yujin Park, Boran Yoon, Jin-Sil Bae, Seung-Woo Han, Ji-Eun Heo, Dong-Eun Kim, Kwon-Yul Ryu.
      LCN2/neutrophil gelatinase-associated lipocalin/24p3 (lipocalin 2) is a secretory protein that acts as a mammalian bacteriostatic molecule. Under neuroinflammatory stress conditions, LCN2 is produced and secreted by activated microglia and reactive astrocytes, resulting in neuronal apoptosis. However, it remains largely unknown whether inflammatory stress and neuronal loss can be minimized by modulating LCN2 production and secretion. Here, we first demonstrated that LCN2 was secreted from reactive astrocytes, which were stimulated by treatment with lipopolysaccharide (LPS) as an inflammatory stressor. Notably, we found two effective conditions that led to the reduction of induced LCN2 levels in reactive astrocytes: proteasome inhibition and macroautophagic/autophagic flux activation. Mechanistically, proteasome inhibition suppresses NFKB/NF-κB activation through NFKBIA/IκBα stabilization in primary astrocytes, even under inflammatory stress conditions, resulting in the downregulation of Lcn2 expression. In contrast, autophagic flux activation via MTOR inhibition reduced the intracellular levels of LCN2 through its pre-secretory degradation. In addition, we demonstrated that the N-terminal signal peptide of LCN2 is critical for its secretion and degradation, suggesting that these two pathways may be mechanistically coupled. Finally, we observed that LPS-induced and secreted LCN2 levels were reduced in the astrocyte-cultured medium under the above-mentioned conditions, resulting in increased neuronal viability, even under inflammatory stress.
    Keywords:  autophagy; lipocalin 2 (LCN2); proteasome; protein degradation; reactive astrocyte; secretory protein
    DOI:  https://doi.org/10.1080/15548627.2023.2180202
  35. EMBO J. 2023 Feb 16. e112202
    Adipocyte autophagy limits gut inflammation by controlling oxylipin and IL-10.
    Felix Clemens Richter, Matthias Friedrich, Nadja Kampschulte, Klara Piletic, Ghada Alsaleh, Ramona Zummach, Julia Hecker, Mathilde Pohin, Nicholas Ilott, Irina Guschina, Sarah Karin Wideman, Errin Johnson, Mariana Borsa, Paula Hahn, Christophe Morriseau, Bruce D Hammock, Henk Simon Schipper, Claire M Edwards, Rudolf Zechner, Britta Siegmund, Carl Weidinger, Nils Helge Schebb, Fiona Powrie, Anna Katharina Simon.
      Lipids play a major role in inflammatory diseases by altering inflammatory cell functions, either through their function as energy substrates or as lipid mediators such as oxylipins. Autophagy, a lysosomal degradation pathway that limits inflammation, is known to impact on lipid availability, however, whether this controls inflammation remains unexplored. We found that upon intestinal inflammation visceral adipocytes upregulate autophagy and that adipocyte-specific loss of the autophagy gene Atg7 exacerbates inflammation. While autophagy decreased lipolytic release of free fatty acids, loss of the major lipolytic enzyme Pnpla2/Atgl in adipocytes did not alter intestinal inflammation, ruling out free fatty acids as anti-inflammatory energy substrates. Instead, Atg7-deficient adipose tissues exhibited an oxylipin imbalance, driven through an NRF2-mediated upregulation of Ephx1. This shift reduced secretion of IL-10 from adipose tissues, which was dependent on the cytochrome P450-EPHX pathway, and lowered circulating levels of IL-10 to exacerbate intestinal inflammation. These results suggest an underappreciated fat-gut crosstalk through an autophagy-dependent regulation of anti-inflammatory oxylipins via the cytochrome P450-EPHX pathway, indicating a protective effect of adipose tissues for distant inflammation.
    Keywords:  IL-10; adipocyte; autophagy; inflammation; oxylipin
    DOI:  https://doi.org/10.15252/embj.2022112202
  36. Cell Rep. 2023 Feb 15. pii: S2211-1247(23)00126-2. [Epub ahead of print]42(2): 112115
    Cone photoreceptors transfer damaged mitochondria to Müller glia.
    Rachel A Hutto, Kaitlyn M Rutter, Michelle M Giarmarco, Edward D Parker, Zachary S Chambers, Susan E Brockerhoff.
      Mitochondria are vital organelles that require sophisticated homeostatic mechanisms for maintenance. Intercellular transfer of damaged mitochondria is a recently identified strategy broadly used to improve cellular health and viability. Here, we investigate mitochondrial homeostasis in the vertebrate cone photoreceptor, the specialized neuron that initiates our daytime and color vision. We find a generalizable response to mitochondrial stress that leads to loss of cristae, displacement of damaged mitochondria from their normal cellular location, initiation of degradation, and transfer to Müller glia cells, a key non-neuronal support cell in the retina. Our findings show transmitophagy from cones to Müller glia as a response to mitochondrial damage. Intercellular transfer of damaged mitochondria represents an outsourcing mechanism that photoreceptors use to support their specialized function.
    Keywords:  CP: Neuroscience; Müller glia; mitochondria; mitophagy; photoreceptor; retina; zebrafish
    DOI:  https://doi.org/10.1016/j.celrep.2023.112115
  37. bioRxiv. 2023 Feb 06. pii: 2023.02.06.527293. [Epub ahead of print]
    TFEB-vacuolar ATPase signaling regulates lysosomal function and microglial activation in tauopathy.
    Baiping Wang, Heidi Martini-Stoica, Chuangye Qi, Tzu-Chiao Lu, Shuo Wang, Wen Xiong, Yanyan Qi, Yin Xu, Marco Sardiello, Hongjie Li, Hui Zheng.
      Transcription factor EB (TFEB) mediates gene expression through binding to the C oordinated L ysosome E xpression A nd R egulation (CLEAR) sequence. TFEB targets include subunits of the vacuolar ATPase (v-ATPase) essential for lysosome acidification. Single nucleus RNA-sequencing (snRNA-seq) of wild-type and PS19 (Tau) transgenic mice identified three unique microglia subclusters in Tau mice that were associated with heightened lysosome and immune pathway genes. To explore the lysosome-immune relationship, we specifically disrupted the TFEB-v-ATPase signaling by creating a knock-in mouse line in which the CLEAR sequence of one of the v-ATPase subunits, Atp6v1h , was mutated. We show that the CLEAR mutant exhibited a muted response to TFEB, resulting in impaired lysosomal acidification and activity. Crossing the CLEAR mutant with Tau mice led to higher tau pathology but diminished microglia response. These microglia were enriched in a subcluster low in mTOR and HIF-1 pathways and was locked in a homeostatic state. Our studies demonstrate a physiological function of TFEB-v-ATPase signaling in maintaining lysosomal homoeostasis and a critical role of the lysosome in mounting a microglia and immune response in tauopathy and Alzheimer’s disease.
    DOI:  https://doi.org/10.1101/2023.02.06.527293
  38. Dis Markers. 2023 ;2023 3350685
    Silencing MYOT Expression May Inhibit Autophagy in Human Skeletal Muscle Cells.
    Zhao-Jing Lin, Jun-Mei Xu, He-Yu Ji, Ya-Qing Jiang, Jun Su, Liang-Liang Fan, Rong Yu.
      Muscle diseases are closely related to autophagy disorders. Studies of autophagy inhibition indicated the importance of autophagy in muscle regeneration, while activation of autophagy can restore muscle function in some myopathies. Previous studies have revealed that mutations in the MYOT gene may lead to several kinds of hereditary myopathies. However, whether the autophagy played a crucial role in hereditary myopathy caused by MYOT mutations was still not clear. In this study, we established the MYOT knockdown human skeletal muscle cell models (HSkMCs) by small interfering RNA. Real-time PCR and Western blot studies found that the expression of p62 and LC3B-II was decreased dramatically, which suggested that silencing MYOT expression may regulate the autophagy in HSkMCs. Further immunofluorescence study on Ad-mCherry-GFP-LC3B adenovirus transfection and monodansylcadaverine (MDC) staining revealed that knocking down the expression of MYOT may inhibit the autophagy. Next, we used the autophagy inducer Earle's balanced salt solution (EBSS) and late-autophagy inhibitor bafilomycin A1 (BAF A1) to treat the HSkMCs, respectively, and found that silencing MYOT expression can inhibit the activation of autophagy by EBSS and aggravate the inhibition of autophagy by BAF A1. Finally, we also found that silencing MYOT expression can downregulate the expression of ATG7 and ATG5, two important autophagy regulatory molecules. Hence, our study may first reveal that knocking down the expression of MYOT may inhibit the autophagy. Hereditary myopathies caused by MYOT mutations may partly result from the inhibition of autophagy in HSkMCs.
    DOI:  https://doi.org/10.1155/2023/3350685
  39. bioRxiv. 2023 Feb 09. pii: 2023.02.08.527546. [Epub ahead of print]
    BAG3 regulates the specificity of the recognition of specific MAPT species by NBR1 and SQSTM1.
    Heng Lin, Sarah Sandkuhler, Colleen Dunlea, Darron H King, Gail V W Johnson.
      Autophagy receptors are essential for the recognition and clearance of specific cargos by selective autophagy, which is essential for maintaining MAPT proteostasis. Previous studies have implicated different autophagy receptors in directing distinct species of MAPT to autophagy, but the underlying mechanisms have not been fully investigated. Here we examine how the autophagy receptors NBR1 and SQSTM1 differentially engage specific forms of MAPT and facilitate their clearance. In primary neurons depletion of NBR1, unlike depletion of SQSTM1, significantly increased phosphorylated MAPT levels. The specificity of the interactions were confirmed using in vitro binding assays with purified proteins. We provide direct evidence that NBR1 preferentially binds to monomeric MAPT, while SQSTM1 interacts predominantly with oligomeric MAPT, and that the co-chaperone BAG3 regulates the specificity of these interactions. Using an in vitro pulldown assay, we show that SQSTM1 only binds to monomeric MAPT when BAG3 is absent and fails to bind when BAG3 is present. The opposite is true of NBR1; its binding to monomeric MAPT was dependent on the presence of BAG3. Interestingly, in Alzheimer’s disease brain the association of NBR1 with BAG3 was significantly decreased. In a mouse model, ablation of BAG3 in neural cells disrupted the association of NBR1 with phosphorylated MAPT and lead to increased levels of phosphorylated and oligomeric MAPT. Overall, our results uncover a novel role for BAG3 in regulating the specificity of selective autophagy receptors in targeting different species of MAPT and provide compelling evidence that BAG3 plays a key role in maintaining MAPT proteostasis.Highlights: First direct evidence of the district role of NBR1 and SQSTM1 in binding with monomeric and oligomeric MAPT, respectively.Demonstration of a novel mechanism by which BAG3 regulates the specificity of the recognition of monomeric MAPT by NBR1 and oligomeric MAPT by SQSTM1.Conditional knockout of BAG3 in the brain disrupted the association of NBR1 with phosphorylated MAPT and lead to increased levels of phosphorylated and oligomeric MAPT.
    DOI:  https://doi.org/10.1101/2023.02.08.527546
  40. Cancer Lett. 2023 Feb 10. pii: S0304-3835(23)00041-1. [Epub ahead of print]557 216090
    Cellular transformation promotes the incorporation of docosahexaenoic acid into the endolysosome-specific lipid bis(monoacylglycerol)phosphate in breast cancer.
    Anastasia L Berg, Megan R Showalter, Nont Kosaisawe, Michelle Hu, Nathanial C Stephens, Michael Sa, Hailey Heil, Noemi Castro, Jenny J Chen, Kacey VanderVorst, Madelyn R Wheeler, Zachary Rabow, Tomas Cajka, John Albeck, Oliver Fiehn, Kermit L Carraway.
      Bis(monoacylglycero)phosphates (BMPs), a class of lipids highly enriched within endolysosomal organelles, are key components of the lysosomal intraluminal vesicles responsible for activating sphingolipid catabolic enzymes. While BMPs are understudied relative to other phospholipids, recent reports associate BMP dysregulation with a variety of pathological states including neurodegenerative diseases and lysosomal storage disorders. Since the dramatic lysosomal remodeling characteristic of cellular transformation could impact BMP abundance and function, we employed untargeted lipidomics approaches to identify and quantify BMP species in several in vitro and in vivo models of breast cancer and comparative non-transformed cells and tissues. We observed lower BMP levels within transformed cells relative to normal cells, and consistent enrichment of docosahexaenoic acid (22:6) fatty acyl chain-containing BMP species in both human- and mouse-derived mammary tumorigenesis models. Our functional analysis points to a working model whereby 22:6 BMPs serve as reactive oxygen species scavengers in tumor cells, protecting lysosomes from oxidant-induced lysosomal membrane permeabilization. Our findings suggest that breast tumor cells might divert polyunsaturated fatty acids into BMP lipids as part of an adaptive response to protect their lysosomes from elevated reactive oxygen species levels, and raise the possibility that BMP-mediated lysosomal protection is a tumor-specific vulnerability that may be exploited therapeutically.
    Keywords:  BMP; Bis(monoacylglycerol)phosphate; Breast cancer; Lipidomics; Lysosomal membrane permeabilization; Polyunsaturated fatty acids; Reactive oxygen species
    DOI:  https://doi.org/10.1016/j.canlet.2023.216090
  41. J Cell Biochem. 2023 Feb 13.
    Toward effective Atg8-based ATTECs: Approaches and perspectives.
    Martin P Schwalm, Stefan Knapp, Vladimir V Rogov.
      Induction of Atg8-family protein (LC3/GABARAP proteins in human) interactions with target proteins of interest by proximity-inducing small molecules offers the possibility for novel targeted protein degradation approaches. However, despite intensive screening campaigns during the last 5 years, no potent ligands for LC3/GABARAPs have been developed, rendering this approach largely unexplored and unsuitable for therapeutic exploitation. In this Viewpoint, we analyze the reported attempts identifying LC3/GABARAP inhibitors and provide our own point of view why no potent inhibitors have been found. Additionally, we designate reasonable directions for the identification of potent and probably selective LC3/GABARAP inhibitors for alternative therapeutic applications.
    Keywords:  ATTEC; Atg8 family proteins; GABARAP; LC3; autophagy; inhibitors; targeted protein degradation
    DOI:  https://doi.org/10.1002/jcb.30380
  42. Mol Cell Neurosci. 2023 Feb 11. pii: S1044-7431(23)00016-7. [Epub ahead of print] 103822
    Neuronal endoplasmic reticulum architecture and roles in axonal physiology.
    Klaas Yperman, Marijn Kuijpers.
      The endoplasmic reticulum (ER) is the largest membrane compartment within eukaryotic cells and is emerging as a key coordinator of many cellular processes. The ER can modulate local calcium fluxes and communicate with other organelles like the plasma membrane. The importance of ER in neuronal processes such as neurite growth, axon repair and neurotransmission has recently gained much attention. In this review, we highlight the importance of the ER tubular network in axonal homeostasis and discuss how the generation and maintenance of the thin tubular ER network in axons and synapses, requires a cooperative effort of ER-shaping proteins, cytoskeleton and autophagy processes.
    Keywords:  ER-phagy; Endoplasmic reticulum; Neuron; Neurotransmission; Synapse
    DOI:  https://doi.org/10.1016/j.mcn.2023.103822
  43. Acta Biochim Biophys Sin (Shanghai). 2022 Dec 25. 54(12): 1822-1831
    ox-LDL induces autophagy-mediated apoptosis by suppressing secretagogin-regulated autophagic flux in pancreatic β-cells.
    Ying Lv, Sijie Xiao, Shuhui Ouyang, Zhengliang Peng, Li Wu, Ziqing Tang, Weizheng Zhang, Renxian Cao, Jing Yang.
      Lipotoxicity has been shown to induce the loss of functional β-cell mass and lead to type 2 diabetes, but the mechanism remains unknown. In this study, we aim to explore the role of secretagogin (SCGN) in lipotoxicity-induced β-cell injury. Our results indicate that ox-LDL treatment leads to autophagic cell death, as evidenced by decreased cell viability, aggravated cell apoptosis, and the accumulation of the p62 protein in MIN6 cells. LysoTracker Red staining, TEM and mRFP-GFP-LC3 assays demonstrate that autophagic flux is blocked in ox-LDL-treated MIN6 cells. Intriguingly, SCGN is significantly decreased in MIN6 cells under lipotoxic conditions. Additionally, siRNA-guided SCGN knockdown blocks autophagic flux triggered by rapamycin, while SCGN restoration alleviates autophagic flux retardation and mitigates cell apoptosis. The physical interaction between SCGN and SNAP29 is validated by bioinformatics analysis, coimmunoprecipitation assay and SCGN knockdown test. Downregulation of SCGN expression reduces the interaction of these two proteins. Taken together, our results indicate that ox-LDL treatment induces apoptotic β-cell death by blocking autophagic flux dependent on SCGN downregulation. SCGN administration prevents lipotoxic β-cell injury and may be a potential therapeutic strategy to promote β-cell expansion in type 2 diabetes.
    Keywords:  apoptosis; autophagic flux; lipotoxicity; secretagogin; β-cells
    DOI:  https://doi.org/10.3724/abbs.2022186
  44. Autophagy. 2023 Feb 13.
    Narirutin activates TFEB (transcription factor EB) to protect against acetaminophen-induced liver injury by targeting PPP3/calcineurin.
    Zhiyuan Fang, Yanyong Xu, Guowen Liu, Qi Shao, Xiaodi Niu, Wenjun Tai, Taiyu Shen, Minghe Fan, Meng Chen, Lin Lei, Wenwen Gao, Yuxiang Song, Zhe Wang, Xiliang Du, Xinwei Li.
      Acetaminophen (APAP) overdose is the predominant cause of drug-induced liver injury worldwide. The macroautophagy/autophagy-lysosomal pathway (ALP) is involved in the APAP hepatotoxicity. TFEB (transcription factor EB) promotes the expression of genes related to autophagy and lysosomal biogenesis, thus, pharmacological activation of TFEB-mediated ALP may be an effective therapeutic approach for treating APAP-induced liver injury. We aimed to reveal the effects of narirutin (NR), the main bioactive constituents isolated from citrus peels, on APAP hepatotoxicity and to explore its underlying mechanism. Administration of NR enhanced activities of antioxidant enzymes, improved mitochondrial dysfunction and alleviated liver injury in APAP-treated mice, whereas NR did not affect APAP metabolism and MAPK/JNK activation. NR enhanced TFEB transcriptional activity and activated ALP in an MTOR complex 1 (MTORC1)-independent but PPP3/calcineurin-dependent manner. Moreover, knockout of Tfeb or knockdown of PPP3CB/CNA2 (protein phosphatase 3, catalytic subunit, beta isoform) in the liver abolished the beneficial effects of NR on APAP overdose. Mechanistically, NR bound to PPP3CB via PRO31, LYS61 and PRO347 residues and enhanced PPP3/calcineurin activity, thereby eliciting dephosphorylation of TFEB and promoting ALP, which alleviated APAP-induced oxidative stress and liver injury. Together, NR protects against APAP-induced liver injury by activating a PPP3/calcineurin-TFEB-ALP axis, indicating NR may be a potential agent for treating APAP overdose.
    Keywords:  PPP3CB/CNA2; TFEB; autophagy-lysosomal pathway; hepatotoxicity; oxidative stress
    DOI:  https://doi.org/10.1080/15548627.2023.2179781
  45. Biophys J. 2023 Feb 10. pii: S0006-3495(22)03392-6. [Epub ahead of print]122(3S1): 461a
    Dual functions of dynamin in beta cell endocytosis and autophagy trafficking as a membrane fission molecule.
    Fan Fan, Jenifer Wendlick, Xuelin Lou.
      
    DOI:  https://doi.org/10.1016/j.bpj.2022.11.2476
  46. J Nephrol. 2023 Feb 17.
    Mitochondrial quality control in acute kidney disease.
    Jingyi Sheng, Xian Li, Juan Lei, WeiHua Gan, Jiayu Song.
      Acute kidney disease (AKD) involves multiple pathogenic mechanisms,  including maladaptive repair of renal cells that are rich in mitochondria. Maintenance of mitochondrial homeostasis and quality control is crucial for normal kidney function. Mitochondrial quality control serves to maintain mitochondrial function under various conditions, including mitochondrial bioenergetics, mitochondrial biogenesis, mitochondrial dynamics (fusion and fission) and mitophagy. To date, increasing evidence indicates that mitochondrial quality control is disrupted when acute kidney disease develops. This review describes the mechanisms of mitochondria quality control in acute kidney disease, aiming to provide clues to help design new clinical treatments.
    Keywords:  Acute kidney disease; Mitochondria; Mitochondria quality control
    DOI:  https://doi.org/10.1007/s40620-023-01582-3
  47. Mol Cancer Res. 2023 Feb 14. pii: MCR-22-0343. [Epub ahead of print]
    Targeting Unc51-like Autophagy Activating Kinase 1 (ULK1) overcomes adaptive drug resistance in acute myelogenous leukemia.
    Seemana Bhattacharya, Sujan Piya, Huaxian Ma, Priyanka Sharma, Qi Zhang, Natalia Baran, Vivian R Ruvolo, Teresa McQueen, R Eric Davis, Rasoul Pourebrahim, Marina Konopleva, Hagop Kantarjian, Nicholas D P Cosford, Michael Andreeff, Gautam Borthakur.
      Despite effective new therapies, adaptive resistance remains the main obstacle in AML therapy. Autophagy induction is a key mechanism for adaptive resistance. Leukemic blasts at diagnosis express higher levels of the apical autophagy kinase ULK1 compared to normal hematopoietic cells. Exposure to chemotherapy and targeted agents upregulate ULK1, hence we hypothesize that developing ULK1 inhibitors may present the unique opportunity for clinical translation of autophagy inhibition. Accordingly, we demonstrate that ULK1 inhibition, by genetic and pharmacological means, suppresses treatment-induced autophagy, overcomes adaptive drug-resistance, and synergizes with chemotherapy and emerging anti-leukemia agents like venetoclax (ABT-199). The study next aims at exploring the underlying mechanisms. Mechanistically, ULK1 inhibition downregulates MCL1 anti-apoptotic gene, impairs mitochondrial function and downregulates components of the CD44-xCT system, resulting in impaired reactive oxygen species (ROS) mitigation, DNA damage and apoptosis. For further validation, several mouse models of AML were generated. In these mouse models, ULK1 deficiency impaired leukemic cell homing and engraftment, delayed disease progression and improved survival. Therefore, in the study we validated our hypothesis and identified ULK1 as an important mediator of adaptive resistance to therapy and an ideal candidate for combination therapy in AML. Therefore, we propose ULK1 inhibition as a therapeutically relevant treatment option to overcome adaptive drug-resistance in AML. Implications: ULK1 drives a cell-intrinsic adaptive resistance in AML and targeting ULK1 mediated autophagy can synergize with existing and emerging AML therapies to overcome drug-resistance and induce apoptosis.
    DOI:  https://doi.org/10.1158/1541-7786.MCR-22-0343
  48. Eur J Med Chem. 2023 Feb 07. pii: S0223-5234(23)00083-1. [Epub ahead of print]250 115168
    Rational design and appraisal of selective Cdc2-Like kinase 1 (Clk1) inhibitors as novel autophagy inducers for the treatment of acute liver injury (ALI).
    Tao Yang, Yingxue Yang, Yong Chen, Minghai Tang, Mingsong Shi, Yang Tian, Xue Yuan, Zhuang Yang, Lijuan Chen.
      Autophagy inducers are promising agents for treating certain medical illnesses, while no safe autophagy inducers are in clinical applications. Cdc2-like kinase 1 (Clk1) inhibitors induce autophagy efficiently; however, most Clk1 inhibitors lack selectivity, especially against Dyrk1A kinase. Herein, we report a series of 1H-pyrrolo[2,3-b]pyridin-5-amine derivatives as novel Clk1 inhibitors. Through detailed structural modification and structure-activity relationship studies, compound 10ad shows potent and selective inhibition for Clk1, with an IC50 value of 5 nM and over 300-fold selectivity for Dyrk1A. Related kinase screening also validates the selectivity of compound 10ad. Furthermore, compound 10ad potently induces autophagy in vitro and exhibits significant hepatoprotective effects in the acute liver injury model induced by acetaminophen (paracetamol). In general, due to the excellent potency and selectivity, compound 10ad was worth further investigation in the treatment of autophagy-related diseases.
    DOI:  https://doi.org/10.1016/j.ejmech.2023.115168
  49. Front Pharmacol. 2023 ;14 1103062
    Autophagy and necroptosis in cisplatin-induced acute kidney injury: Recent advances regarding their role and therapeutic potential.
    Noha Alassaf, Hala Attia.
      Cisplatin (CP) is a broad-spectrum antineoplastic agent, used to treat many different types of malignancies due to its high efficacy and low cost. However, its use is largely limited by acute kidney injury (AKI), which, if left untreated, may progress to cause irreversible chronic renal dysfunction. Despite substantial research, the exact mechanisms of CP-induced AKI are still so far unclear and effective therapies are lacking and desperately needed. In recent years, necroptosis, a novel subtype of regulated necrosis, and autophagy, a form of homeostatic housekeeping mechanism have witnessed a burgeoning interest owing to their potential to regulate and alleviate CP-induced AKI. In this review, we elucidate in detail the molecular mechanisms and potential roles of both autophagy and necroptosis in CP-induced AKI. We also explore the potential of targeting these pathways to overcome CP-induced AKI according to recent advances.
    Keywords:  acute kidney injury; autophagy; cisplatin; macroautophagy; necroinflammation; necroptosis; nephrotoxicity
    DOI:  https://doi.org/10.3389/fphar.2023.1103062
  50. PLoS One. 2023 ;18(2): e0281845
    IL-17A regulates autophagy and promotes osteoclast differentiation through the ERK/mTOR/Beclin1 pathway.
    Hao Tang, Shida Zhu, Kai Chen, Shujie Yuan, Junzu Hu, Hongkai Wang.
      Bone is a frequent target of tumor metastasis, with high incidence rate and poor prognosis. Osteoclasts play a key role in the process of tumor bone metastasis. Interleukin-17A (IL-17A) is an inflammatory cytokine, highly expressed in a variety of tumor cells, that can alter the autophagic activity of other cells, thereby causing corresponding lesions. Previous studies have shown that low concentration IL-17A can promote osteoclastogenesis. The aim of this study was to clarify the mechanism of low concentration IL-17A promoting osteoclastogenesis by regulating autophagic activity. The results of our study showed that IL-17A could promote the differentiation of osteoclast precursors (OCPs) into osteoclasts in the presence of RANKL, and increase the mRNA levels of osteoclast-specific genes. Moreover, IL-17A increased the expression of Beclin1 by inhibiting the phosphorylation of ERK and mTOR, leading to enhanced autophagy of OCPs, accompanied by decreased OCP apoptosis. Furthermore, knockdown of Beclin1 and suppression of autophagy by 3-methyladenine (3-MA) significantly attenuated the enhanced osteoclastogenesis induced by IL-17A. In summary, these results indicate that low concentration IL-17A enhances the autophagic activity of OCPs through the ERK/mTOR/Beclin1 pathway during osteoclastogenesis, and further promotes osteoclast differentiation, suggesting that IL-17A may serve as a potential therapeutic target for cancer-related bone resorption in cancer patients.
    DOI:  https://doi.org/10.1371/journal.pone.0281845
  51. Theranostics. 2023 ;13(3): 1059-1075
    Hyperactive neuronal autophagy depletes BDNF and impairs adult hippocampal neurogenesis in a corticosterone-induced mouse model of depression.
    Kuo Zhang, Fan Wang, Mengying Zhai, Meiyao He, Yuxuan Hu, Lijin Feng, Yuting Li, Jingyu Yang, Chunfu Wu.
      Background: Depression is a mental disorder that poses a serious threat to human health. Adult hippocampal neurogenesis (AHN) is closely associated with the efficacy of antidepressants. Chronic treatment with corticosterone (CORT), a well-validated pharmacological stressor, induces depressive-like behaviors and suppresses AHN in experimental animals. However, the possible mechanisms of chronic CORT action remain elusive. Methods: A chronic CORT treatment (0.1 mg/mL, drinking water for 4 weeks) was applied to prepare a mouse model of depression. Immunofluorescence was performed to analyze the hippocampal neurogenesis lineage, and immunoblotting, immunofluorescence, electron microscopy, and adeno-associated virus (AAV) expressing a pH-sensitive tandemly tagged light chain 3 (LC3) protein were used to analyze neuronal autophagy. AAV-hSyn-miR30-shRNA was used to knock down autophagy-related gene 5 (Atg5) expression in the neurons. Results: Chronic CORT induces depressive-like behaviors and decreases the expression of neuronal brain-derived neurotrophic factor (BDNF) in the dentate gyrus (DG) of the hippocampus in mice. Moreover, it markedly diminishes the proliferation of neural stem cells (NSCs), neural progenitor cells, and neuroblasts and impairs the survival and migration of newborn immature and mature neurons in the DG, which may be attributed to changes in the cell cycle kinetics and induction of NSCs apoptosis. Furthermore, chronic CORT induces hyperactive neuronal autophagy in the DG, possibly by increasing the expression of ATG5 and causing excess lysosomal degradation of BDNF in neurons. Notably, inhibiting hyperactive neuronal autophagy in the DG of mice by knocking down Atg5 in neurons using RNA interference reverses the decrease of neuronal BDNF expression, rescues AHN, and exerts antidepressant effects. Conclusion: Our findings reveal a neuronal autophagy-dependent mechanism that links chronic CORT to reduced neuronal BDNF levels, AHN suppression and depressive-like behavior in mice. In addition, our results provide insights for treating depression by targeting neuronal autophagy in the DG of the hippocampus.
    Keywords:  Adult hippocampal neurogenesis; BDNF; Corticosterone; Depression; Neuronal autophagy.
    DOI:  https://doi.org/10.7150/thno.81067
  52. Cancer Med. 2023 Feb 15.
    Autophagy and its role in osteosarcoma.
    Biao Ning, Yixin Liu, Tianhe Huang, Yongchang Wei.
      Osteosarcoma (OS) is the most common bone malignancy and preferably occurs in children and adolescents. Despite significant advances in surgery and chemotherapy for OS over the past few years, overall survival rates of OS have reached a bottleneck. Thus, extensive researches aimed at developing new therapeutic targets for OS are urgently needed. Autophagy, a conserved process which allows cells to recycle altered or unused organelles and cellular components, has been proven to play a critical role in multiple biological processes in OS. In this article, we summarized the association between autophagy and proliferation, metastasis, chemotherapy, radiotherapy, and immunotherapy of OS, revealing that autophagy-related genes and pathways could serve as potential targets for OS therapy.
    Keywords:  autophagy; chemotherapy; immunotherapy; osteosarcoma; progression; radiotherapy
    DOI:  https://doi.org/10.1002/cam4.5407
  53. PLoS Genet. 2023 Feb 15. 19(2): e1010641
    The nutrient-responsive CDK Pho85 primes the Sch9 kinase for its activation by TORC1.
    Marie-Anne Deprez, Marco Caligaris, Joëlle Rosseels, Riko Hatakeyama, Ruben Ghillebert, Belém Sampaio-Marques, Kaivalya Mudholkar, Elja Eskes, Els Meert, Christian Ungermann, Paula Ludovico, Sabine Rospert, Claudio De Virgilio, Joris Winderickx.
      Yeast cells maintain an intricate network of nutrient signaling pathways enabling them to integrate information on the availability of different nutrients and adjust their metabolism and growth accordingly. Cells that are no longer capable of integrating this information, or that are unable to make the necessary adaptations, will cease growth and eventually die. Here, we studied the molecular basis underlying the synthetic lethality caused by loss of the protein kinase Sch9, a key player in amino acid signaling and proximal effector of the conserved growth-regulatory TORC1 complex, when combined with either loss of the cyclin-dependent kinase (CDK) Pho85 or loss of its inhibitor Pho81, which both have pivotal roles in phosphate sensing and cell cycle regulation. We demonstrate that it is specifically the CDK-cyclin pair Pho85-Pho80 or the partially redundant CDK-cyclin pairs Pho85-Pcl6/Pcl7 that become essential for growth when Sch9 is absent. Interestingly, the respective three CDK-cyclin pairs regulate the activity and distribution of the phosphatidylinositol-3 phosphate 5-kinase Fab1 on endosomes and vacuoles, where it generates phosphatidylinositol-3,5 bisphosphate that serves to recruit both TORC1 and its substrate Sch9. In addition, Pho85-Pho80 directly phosphorylates Sch9 at Ser726, and to a lesser extent at Thr723, thereby priming Sch9 for its subsequent phosphorylation and activation by TORC1. The TORC1-Sch9 signaling branch therefore integrates Pho85-mediated information at different levels. In this context, we also discovered that loss of the transcription factor Pho4 rescued the synthetic lethality caused by loss of Pho85 and Sch9, indicating that both signaling pathways also converge on Pho4, which appears to be wired to a feedback loop involving the high-affinity phosphate transporter Pho84 that fine-tunes Sch9-mediated responses.
    DOI:  https://doi.org/10.1371/journal.pgen.1010641
  54. PLoS One. 2023 ;18(2): e0281957
    Ethyl pyruvate protects SHSY5Y cells against 6-hydroxydopamine-induced neurotoxicity by upregulating autophagy.
    Yuening Luo, Kazuichi Sakamoto.
      Parkinson disease is a chronic progressive neurodegenerative disorder with a prevalence that increases with age. The glycolytic end-product pyruvate, has antioxidant and neuroprotective feature. Here, we investigated the effects of ethyl pyruvate (EP), a pyruvic acid derivative, on 6-hydroxydopamine-induced SH-SY5Y cell apoptosis. Ethyl pyruvate decreased protein levels of cleaved caspase-3, phosphorylated endoplasmic reticulum kinase (pERK), and extracellular signal-regulated kinase (ERK), suggesting that EP reduces apoptosis via the ERK signaling pathway. Ethyl pyruvate also decreased oxygen species (ROS) and neuromelanin contents, suggesting that it suppresses ROS-mediated neuromelanin synthesis. Furthermore, increased protein levels of Beclin-1 and LC-II, and LC-II:LC-I ratios indicated that EP upregulates autophagy.
    DOI:  https://doi.org/10.1371/journal.pone.0281957
  55. Biophys J. 2023 Feb 10. pii: S0006-3495(22)02681-9. [Epub ahead of print]122(3S1): 314a
    Lysosomal exocytosis releases pathogenic α-synuclein species from neurons.
    Manu Sharma.
      
    DOI:  https://doi.org/10.1016/j.bpj.2022.11.1765
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