bims-auttor Biomed News
on Autophagy and mTOR
Issue of 2023‒07‒30
48 papers selected by
Viktor Korolchuk, Newcastle University
  1. Alkaline intracellular pH (pHi) increases PI3K kinase activity to promote mTORC1 and mTORC2 signaling and function during growth factor limitation.
  2. Regulation of mTOR Signaling: Emerging Role of Cyclic Nucleotide-Dependent Protein Kinases and Implications for Cardiometabolic Disease.
  3. UBQLN2 and HSP70 participate in Parkin-mediated mitophagy by facilitating outer mitochondrial membrane rupture.
  4. Role of lipids in the control of autophagy and primary cilium signaling in neurons.
  5. Antioxidative Role of Heterophagy, Autophagy, and Mitophagy in the Retina and Their Association with the Age-Related Macular Degeneration (AMD) Etiopathogenesis.
  6. Revisiting the Role of Autophagy in Cardiac Differentiation: A Comprehensive Review of Interplay with Other Signaling Pathways.
  7. Ionizing radiation triggers mitophagy to enhance DNA damage in cancer cells.
  8. Exploring the mTOR Signalling Pathway and Its Inhibitory Scope in Cancer.
  9. The Metabolic Basis for Nervous System Dysfunction in Alzheimer's Disease, Parkinson's Disease, and Huntington's Disease.
  10. ER membrane curvature and ubiquitin as drivers of ER-phagy.
  11. The UPR Maintains Proteostasis and the Viability and Function of Hippocampal Neurons in Adult Mice.
  12. mTOR inhibition reprograms cellular proteostasis by regulating eIF3D-mediated selective mRNA translation and promotes cell phenotype switching.
  13. Dissecting the multifaced function of transcription factor EB (TFEB) in human diseases: From molecular mechanism to pharmacological modulation.
  14. Restoration of β-GC trafficking improves the lysosome function in Gaucher disease.
  15. Should evidence of an autolysosomal de-acidification defect in Alzheimer and Parkinson diseases call for caution in prescribing chronic PPI and DMARD?
  16. Protective Autophagy Attenuates the Cytotoxicity of MTI-31 in Renal Cancer Cells by Activating the ERK Pathway.
  17. Lysosomal dysfunction in Down syndrome and Alzheimer mouse models is caused by v-ATPase inhibition by Tyr682-phosphorylated APP βCTF.
  18. The Complex Role of Chaperone-Mediated Autophagy in Cancer Diseases.
  19. mTOR Signaling Pathway and Gut Microbiota in Various Disorders: Mechanisms and Potential Drugs in Pharmacotherapy.
  20. Rev1 deficiency induces a metabolic shift in MEFs that can be manipulated by the NAD+ precursor nicotinamide riboside.
  21. Autophagy, Oxidative Stress, and Alcoholic Liver Disease: A Systematic Review and Potential Clinical Applications.
  22. Hyperglucagonaemia in diabetes: altered amino acid metabolism triggers mTORC1 activation, which drives glucagon production.
  23. Small cytosolic double-stranded DNA represses cyclic GMP-AMP synthase activation and induces autophagy.
  24. Linking ROS Levels to Autophagy: The Key Role of AMPK.
  25. Mitophagy in intracerebral hemorrhage: a new target for therapeutic intervention.
  26. Modulation of Lysosomal Cl- Mediates Migration and Apoptosis through the TRPML1 as a Lysosomal Cl- Sensor.
  27. LRRK2 suppresses lysosome degradative activity in macrophages and microglia through MiT-TFE transcription factor inhibition.
  28. Stub1 ameliorates ER stress-induced neural cell apoptosis and promotes locomotor recovery through restoring autophagy flux after spinal cord injury.
  29. Pathophysiology of diabetic kidney disease and autophagy: A review.
  30. Calnexin controls TrkB cell surface transport and ER-phagy in mouse cerebral cortex development.
  31. The constructive and destructive impact of autophagy on both genders' reproducibility, a comprehensive review.
  32. miR-29a-3p Regulates Autophagy by Targeting Akt3-Mediated mTOR in SiO2-Induced Lung Fibrosis.
  33. Starvation-inactivated MTOR triggers cell migration via a ULK1-SH3PXD2A/TKS5-MMP14 pathway in ovarian carcinoma.
  34. An Autophagy-Associated MITF-GAS5-miR-23 Loop Attenuates Vascular Oxidative and Inflammatory Damage in Sepsis.
  35. Autophagy mediates an amplification loop during ferroptosis.
  36. Increased degradation of FMRP contributes to neuronal hyperexcitability in tuberous sclerosis complex.
  37. Basal autophagic flux measured in blood correlates positively with age in adults at increased risk of type 2 diabetes.
  38. A Role of PI3K/Akt Signaling in Oocyte Maturation and Early Embryo Development.
  39. Arsenic induced autophagy-dependent apoptosis in hippocampal neurons via AMPK/mTOR signaling pathway.
  40. TRAF6 regulates autophagy and apoptosis of melanoma cells through c-Jun/ATG16L2 signaling pathway.
  41. KLHL3-dependent WNK4 degradation affected by potassium through the neddylation and autophagy pathway.
  42. Modulating p38 MAPK signaling by proteostasis mechanisms supports tissue integrity during growth and aging.
  43. Impaired BCAA catabolism in adipose tissues promotes age-associated metabolic derangement.
  44. Streptococcus uberis induced expressions of pro-inflammatory IL-6, TNF-α, and IFN-γ in bovine mammary epithelial cells associated with inhibited autophagy and autophagy flux formation.
  45. Hyper-ubiquitylation of DNA helicase RECQL4 by E3 ligase MITOL prevents mitochondrial entry and potentiates mitophagy.
  46. Evolutionarily divergent mTOR remodels translatome for tissue regeneration.
  47. PTEN-induced putative kinase 1 regulates mitochondrial quality control and is essential for the maturation of human induced pluripotent stem cell-derived cardiomyocytes.
  48. The Effects of Cinobufagin on Hepatocellular Carcinoma Cells Enhanced by MRT68921, an Autophagy Inhibitor.
  1. J Biol Chem. 2023 Jul 26. pii: S0021-9258(23)02125-7. [Epub ahead of print] 105097
    Alkaline intracellular pH (pHi) increases PI3K kinase activity to promote mTORC1 and mTORC2 signaling and function during growth factor limitation.
    Dubek Kazyken, Stephen I Lentz, Maxwell Wadley, Diane C Fingar.
      The conserved protein kinase mTOR (mechanistic target of rapamycin) responds to diverse environmental cues to control cell metabolism and promote cell growth, proliferation, and survival as part of two multiprotein complexes, mTOR complex 1 (mTORC1) and mTORC2. Our prior work demonstrated that an alkaline intracellular pH (pHi) increases mTORC2 activity and cell survival in complete media in part by activating AMPK, a kinase best known to sense energetic stress. It is important to note that an alkaline pHi represents an under-appreciated hallmark of cancer cells that promotes their oncogenic behaviors. In addition, mechanisms that control mTORC1 and mTORC2 signaling and function remain incompletely defined, particularly in response to stress conditions. Here, we demonstrate that an alkaline pHi increases PI3K activity to promote mTORC1 and mTORC2 signaling in the absence of serum growth factors. Alkaline pHi increases mTORC1 activity through PI3K-Akt signaling, which mediates inhibitory phosphorylation of the upstream proteins TSC2 and PRAS40 and dissociates TSC2 from lysosomal membranes, thus enabling Rheb-mediated activation of mTORC1. Thus, we show that an alkaline pHi mimics growth factor-PI3K signaling. Functionally, we also demonstrate that an alkaline pHi increases cap-dependent protein synthesis through inhibitory phosphorylation of 4EBP1 and suppresses apoptosis in a PI3K- and mTOR-dependent manner. We speculate that an alkaline pHi promotes a low, basal level of cell metabolism (e.g., protein synthesis) that enables cancer cells within growing tumors to proliferate and survive despite limiting growth factors and nutrients, in part through elevated PI3K-mTORC1 and/or PI3K-mTORC2 signaling.
    Keywords:  Akt PKB; S6 kinase; apoptosis; cell signaling; eukaryotic translation initiation factor 4E (eIF4E); eukaryotic translation initiation factor 4E-binding protein (eIF4EBP1); pH regulation; phosphatidylinositide 3-kinase (PI 3-kinase); protein synthesis; target of rapamycin (TOR)
    DOI:  https://doi.org/10.1016/j.jbc.2023.105097
  2. Int J Mol Sci. 2023 Jul 15. pii: 11497. [Epub ahead of print]24(14):
    Regulation of mTOR Signaling: Emerging Role of Cyclic Nucleotide-Dependent Protein Kinases and Implications for Cardiometabolic Disease.
    Fubiao Shi, Sheila Collins.
      The mechanistic target of rapamycin (mTOR) kinase is a central regulator of cell growth and metabolism. It is the catalytic subunit of two distinct large protein complexes, mTOR complex 1 (mTORC1) and mTORC2. mTOR activity is subjected to tight regulation in response to external nutrition and growth factor stimulation. As an important mechanism of signaling transduction, the 'second messenger' cyclic nucleotides including cAMP and cGMP and their associated cyclic nucleotide-dependent kinases, including protein kinase A (PKA) and protein kinase G (PKG), play essential roles in mediating the intracellular action of a variety of hormones and neurotransmitters. They have also emerged as important regulators of mTOR signaling in various physiological and disease conditions. However, the mechanism by which cAMP and cGMP regulate mTOR activity is not completely understood. In this review, we will summarize the earlier work establishing the ability of cAMP to dampen mTORC1 activation in response to insulin and growth factors and then discuss our recent findings demonstrating the regulation of mTOR signaling by the PKA- and PKG-dependent signaling pathways. This signaling framework represents a new non-canonical regulation of mTOR activity that is independent of AKT and could be a novel mechanism underpinning the action of a variety of G protein-coupled receptors that are linked to the mTOR signaling network. We will further review the implications of these signaling events in the context of cardiometabolic disease, such as obesity, non-alcoholic fatty liver disease, and cardiac remodeling. The metabolic and cardiac phenotypes of mouse models with targeted deletion of Raptor and Rictor, the two essential components for mTORC1 and mTORC2, will be summarized and discussed.
    Keywords:  PKA; PKG; Raptor; Rictor; cAMP; cGMP; cardiac hypertrophy; fatty liver disease; mTOR; obesity
    DOI:  https://doi.org/10.3390/ijms241411497
  3. EMBO Rep. 2023 Jul 28. e55859
    UBQLN2 and HSP70 participate in Parkin-mediated mitophagy by facilitating outer mitochondrial membrane rupture.
    Qilian Ma, Jiaqi Xin, Qiang Peng, Ningning Li, Shan Sun, Hongyu Hou, Guoqiang Ma, Nana Wang, Li Zhang, Kin Yip Tam, Heiko Dussmann, Jochen Hm Prehn, Hongfeng Wang, Zheng Ying.
      Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are two aging-related neurodegenerative diseases that share common key features, including aggregation of pathogenic proteins, dysfunction of mitochondria, and impairment of autophagy. Mutations in ubiquilin 2 (UBQLN2), a shuttle protein in the ubiquitin-proteasome system (UPS), can cause ALS/FTD, but the mechanism underlying UBQLN2-mediated pathogenesis is still uncertain. Recent studies indicate that mitophagy, a selective form of autophagy which is crucial for mitochondrial quality control, is tightly associated with neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and ALS. In this study, we show that after Parkin-dependent ubiquitination of damaged mitochondria, UBQLN2 is recruited to poly-ubiquitinated mitochondria through the UBA domain. UBQLN2 cooperates with the chaperone HSP70 to promote UPS-driven degradation of outer mitochondrial membrane (OMM) proteins. The resulting rupture of the OMM triggers the autophagosomal recognition of the inner mitochondrial membrane receptor PHB2. UBQLN2 is required for Parkin-mediated mitophagy and neuronal survival upon mitochondrial damage, and the ALS/FTD pathogenic mutations in UBQLN2 impair mitophagy in primary cultured neurons. Taken together, our findings link dysfunctional mitophagy to UBQLN2-mediated neurodegeneration.
    Keywords:  ALS; Parkin; UBQLN2; mitophagy; ubiquitin
    DOI:  https://doi.org/10.15252/embr.202255859
  4. Neural Regen Res. 2024 Feb;19(2): 264-271
    Role of lipids in the control of autophagy and primary cilium signaling in neurons.
    María Paz Hernández-Cáceres, Daniela Pinto-Nuñez, Patricia Rivera, Paulina Burgos, Francisco Díaz-Castro, Alfredo Criollo, Maria Jose Yañez, Eugenia Morselli.
      The brain is, after the adipose tissue, the organ with the greatest amount of lipids and diversity in their composition in the human body. In neurons, lipids are involved in signaling pathways controlling autophagy, a lysosome-dependent catabolic process essential for the maintenance of neuronal homeostasis and the function of the primary cilium, a cellular antenna that acts as a communication hub that transfers extracellular signals into intracellular responses required for neurogenesis and brain development. A crosstalk between primary cilia and autophagy has been established; however, its role in the control of neuronal activity and homeostasis is barely known. In this review, we briefly discuss the current knowledge regarding the role of autophagy and the primary cilium in neurons. Then we review the recent literature about specific lipid subclasses in the regulation of autophagy, in the control of primary cilium structure and its dependent cellular signaling in physiological and pathological conditions, specifically focusing on neurons, an area of research that could have major implications in neurodevelopment, energy homeostasis, and neurodegeneration.
    Keywords:  GPCR; NPC1; autophagic flux; cholesterol; fatty acids; lysosomal storage diseases; neurons; phosphoinositides; primary cilium
    DOI:  https://doi.org/10.4103/1673-5374.377414
  5. Antioxidants (Basel). 2023 Jun 29. pii: 1368. [Epub ahead of print]12(7):
    Antioxidative Role of Heterophagy, Autophagy, and Mitophagy in the Retina and Their Association with the Age-Related Macular Degeneration (AMD) Etiopathogenesis.
    Małgorzata Nita, Andrzej Grzybowski.
      Age-related macular degeneration (AMD), an oxidative stress-linked neurodegenerative disease, leads to irreversible damage of the central retina and severe visual impairment. Advanced age and the long-standing influence of oxidative stress and oxidative cellular damage play crucial roles in AMD etiopathogenesis. Many authors emphasize the role of heterophagy, autophagy, and mitophagy in maintaining homeostasis in the retina. Relevantly modifying the activity of both macroautophagy and mitophagy pathways represents one of the new therapeutic strategies in AMD. Our review provides an overview of the antioxidative roles of heterophagy, autophagy, and mitophagy and presents associations between dysregulations of these molecular mechanisms and AMD etiopathogenesis. The authors performed an extensive analysis of the literature, employing PubMed and Google Scholar, complying with the 2013-2023 period, and using the following keywords: age-related macular degeneration, RPE cells, reactive oxygen species, oxidative stress, heterophagy, autophagy, and mitophagy. Heterophagy, autophagy, and mitophagy play antioxidative roles in the retina; however, they become sluggish and dysregulated with age and contribute to AMD development and progression. In the retina, antioxidative roles also play in RPE cells, NFE2L2 and PGC-1α proteins, NFE2L2/PGC-1α/ARE signaling cascade, Nrf2 factor, p62/SQSTM1/Keap1-Nrf2/ARE pathway, circulating miRNAs, and Yttrium oxide nanoparticles performed experimentally in animal studies.
    Keywords:  RPE cells; age-related macular degeneration; autophagy; heterophagy; mitophagy; oxidative stress; reactive oxygen species
    DOI:  https://doi.org/10.3390/antiox12071368
  6. Genes (Basel). 2023 Jun 24. pii: 1328. [Epub ahead of print]14(7):
    Revisiting the Role of Autophagy in Cardiac Differentiation: A Comprehensive Review of Interplay with Other Signaling Pathways.
    Mina Kolahdouzmohammadi, Roya Kolahdouz-Mohammadi, Seyed Abdolhossein Tabatabaei, Brunella Franco, Mehdi Totonchi.
      Autophagy is a critical biological process in which cytoplasmic components are sequestered in autophagosomes and degraded in lysosomes. This highly conserved pathway controls intracellular recycling and is required for cellular homeostasis, as well as the correct functioning of a variety of cellular differentiation programs, including cardiomyocyte differentiation. By decreasing oxidative stress and promoting energy balance, autophagy is triggered during differentiation to carry out essential cellular remodeling, such as protein turnover and lysosomal degradation of organelles. When it comes to controlling cardiac differentiation, the crosstalk between autophagy and other signaling networks such as fibroblast growth factor (FGF), Wnt, Notch, and bone morphogenetic proteins (BMPs) is essential, yet the interaction between autophagy and epigenetic controls remains poorly understood. Numerous studies have shown that modulating autophagy and precisely regulating it can improve cardiac differentiation, which can serve as a viable strategy for generating mature cardiac cells. These findings suggest that autophagy should be studied further during cardiac differentiation. The purpose of this review article is not only to discuss the relationship between autophagy and other signaling pathways that are active during the differentiation of cardiomyocytes but also to highlight the importance of manipulating autophagy to produce fully mature cardiomyocytes, which is a tough challenge.
    Keywords:  autophagy; cardiomyocyte; differentiation
    DOI:  https://doi.org/10.3390/genes14071328
  7. Cell Death Discov. 2023 Jul 28. 9(1): 267
    Ionizing radiation triggers mitophagy to enhance DNA damage in cancer cells.
    Yanxian Ren, Pengfei Yang, Chenghao Li, Wen-An Wang, Tianyi Zhang, Jin Li, Haining Li, Chunlu Dong, Wenbo Meng, Heng Zhou.
      Radiotherapy is an important cancer treatment strategy that causes DNA damage in tumor cells either directly or indirectly. Autophagy is a physiological process linked to DNA damage. Mitophagy is a form of autophagy, which specifically targets and eliminates impaired mitochondria, thereby upholding cellular homeostasis. However, the connection between DNA damage and mitophagy has yet to be fully elucidated. We found that mitophagy, as an upstream signal, increases ionizing radiation-induced DNA damage by downregulating or overexpressing key mitophagy proteins Parkin and BNIP3. Enhancing the basal level of mitophagy in conjunction with X-ray irradiation can potentially diminish cell cycle arrest at the G2/M phase, substantially elevate the accumulation of γ-H2AX, 53BP1, and PARP1 foci within the nucleus, augment DNA damage, and facilitate the demise of tumor cells. Consequently, this approach prolongs the survival of melanoma-bearing mice. The findings of this study are anticipated to offer a therapeutic approach for enhancing the therapeutic effectiveness of radiotherapy.
    DOI:  https://doi.org/10.1038/s41420-023-01573-0
  8. Pharmaceuticals (Basel). 2023 Jul 14. pii: 1004. [Epub ahead of print]16(7):
    Exploring the mTOR Signalling Pathway and Its Inhibitory Scope in Cancer.
    Suhail Ahmad Mir, Ashraf Dar, Saad Ali Alshehri, Shadma Wahab, Laraibah Hamid, Mohammad Ali Abdullah Almoyad, Tabasum Ali, Ghulam Nabi Bader.
      Mechanistic target of rapamycin (mTOR) is a protein kinase that regulates cellular growth, development, survival, and metabolism through integration of diverse extracellular and intracellular stimuli. Additionally, mTOR is involved in interplay of signalling pathways that regulate apoptosis and autophagy. In cells, mTOR is assembled into two complexes, mTORC1 and mTORC2. While mTORC1 is regulated by energy consumption, protein intake, mechanical stimuli, and growth factors, mTORC2 is regulated by insulin-like growth factor-1 receptor (IGF-1R), and epidermal growth factor receptor (EGFR). mTOR signalling pathways are considered the hallmark in cancer due to their dysregulation in approximately 70% of cancers. Through downstream regulators, ribosomal protein S6 kinase β-1 (S6K1) and eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1), mTORC1 influences various anabolic and catabolic processes in the cell. In recent years, several mTOR inhibitors have been developed with the aim of treating different cancers. In this review, we will explore the current developments in the mTOR signalling pathway and its importance for being targeted by various inhibitors in anti-cancer therapeutics.
    Keywords:  cancer; mTOR inhibitors; mTORC1/2; rapamycin; regulation of mTOR signalling pathway
    DOI:  https://doi.org/10.3390/ph16071004
  9. Curr Neurovasc Res. 2023 Jul 21.
    The Metabolic Basis for Nervous System Dysfunction in Alzheimer's Disease, Parkinson's Disease, and Huntington's Disease.
    Kenneth Maiese.
      Disorders of metabolism affect multiple systems throughout the body but may have the greatest impact on both central and peripheral nervous systems. Currently available treatments and behavior changes for disorders that include diabetes mellitus (DM) and nervous system diseases are limited and cannot reverse the disease burden. Greater access to healthcare and a longer lifespan have led to an increased prevalence of metabolic and neurodegenerative disorders. In light of these challenges, innovative studies into the underlying disease pathways offer new treatment perspectives for Alzheimer's Disease, Parkinson's Disease, and Huntington's Disease. Metabolic disorders are intimately tied to neurodegenerative diseases and can lead to debilitating outcomes, such as multi-nervous system disease, susceptibility to viral pathogens, and long-term cognitive disability. Novel strategies that can robustly address metabolic disease and neurodegenerative disorders involve a careful consideration of cellular metabolism, programmed cell death pathways, the mechanistic target of rapamycin (mTOR) and its associated pathways of mTOR Complex 1 (mTORC1), mTOR Complex 2 (mTORC2), AMP-activated protein kinase (AMPK), growth factor signaling, and underlying risk factors such as the apolipoprotein E (APOE-4) gene. Yet, these complex pathways necessitate comprehensive understanding to achieve clinical outcomes that target disease susceptibility, onset, and progression.
    Keywords:  Alzheimer’s disease; COVID-19; Huntington’s disease; Parkinson’s disease; apoptosis; autophagy; diabetes mellitus; erythropoietin; mTOR; pyroptosis
    DOI:  https://doi.org/10.2174/1567202620666230721122957
  10. Dev Cell. 2023 Jul 24. pii: S1534-5807(23)00306-4. [Epub ahead of print]58(14): 1219-1220
    ER membrane curvature and ubiquitin as drivers of ER-phagy.
    Melissa J Hoyer, J Wade Harper.
      In a recent issue of Nature, González et al. and Foronda et al. examine the role of ubiquitin in autophagic capture of ER by ER-phagy. They propose that ubiquitylation of ER-phagy receptor FAM134B and ER-shaping protein ARL61PL1 promotes receptor clustering in nanodomains, which generates membrane curvature, facilitating autophagosomal capture.
    DOI:  https://doi.org/10.1016/j.devcel.2023.06.008
  11. Int J Mol Sci. 2023 Jul 16. pii: 11542. [Epub ahead of print]24(14):
    The UPR Maintains Proteostasis and the Viability and Function of Hippocampal Neurons in Adult Mice.
    Pingting Liu, Md Razaul Karim, Ana Covelo, Yuan Yue, Michael K Lee, Wensheng Lin.
      The unfolded protein response (UPR), which comprises three branches: PERK, ATF6α, and IRE1, is a major mechanism for maintaining cellular proteostasis. Many studies show that the UPR is a major player in regulating neuron viability and function in various neurodegenerative diseases; however, its role in neurodegeneration is highly controversial. Moreover, while evidence suggests activation of the UPR in neurons under normal conditions, deficiency of individual branches of the UPR has no major effect on brain neurons in animals. It remains unclear whether or how the UPR participates in regulating neuronal proteostasis under normal and disease conditions. To determine the physiological role of the UPR in neurons, we generated mice with double deletion of PERK and ATF6α in neurons. We found that inactivation of PERK and ATF6α in neurons caused lysosomal dysfunction (as evidenced by decreased expression of the V0a1 subunit of v-ATPase and decreased activation of cathepsin D), impairment of autophagic flux (as evidenced by increased ratio of LC3-II/LC3-I and increased p62 level), and accumulation of p-tau and Aβ42 in the hippocampus, and led to impairment of spatial memory, impairment of hippocampal LTP, and hippocampal degeneration in adult mice. These results suggest that the UPR is required for maintaining neuronal proteostasis (particularly tau and Aβ homeostasis) and the viability and function of neurons in the hippocampus of adult mice.
    Keywords:  UPR; autophagy; lysosome; neuron; proteostasis; tau
    DOI:  https://doi.org/10.3390/ijms241411542
  12. Cell Rep. 2023 Jul 25. pii: S2211-1247(23)00879-3. [Epub ahead of print]42(8): 112868
    mTOR inhibition reprograms cellular proteostasis by regulating eIF3D-mediated selective mRNA translation and promotes cell phenotype switching.
    Sejeong Shin, Min-Joon Han, Mark P Jedrychowski, Ziyang Zhang, Kevan M Shokat, David R Plas, Noah Dephoure, Sang-Oh Yoon.
      Cells maintain and dynamically change their proteomes according to the environment and their needs. Mechanistic target of rapamycin (mTOR) is a key regulator of proteostasis, homeostasis of the proteome. Thus, dysregulation of mTOR leads to changes in proteostasis and the consequent progression of diseases, including cancer. Based on the physiological and clinical importance of mTOR signaling, we investigated mTOR feedback signaling, proteostasis, and cell fate. Here, we reveal that mTOR targeting inhibits eIF4E-mediated cap-dependent translation, but feedback signaling activates a translation initiation factor, eukaryotic translation initiation factor 3D (eIF3D), to sustain alternative non-canonical translation mechanisms. Importantly, eIF3D-mediated protein synthesis enables cell phenotype switching from proliferative to more migratory. eIF3D cooperates with mRNA-binding proteins such as heterogeneous nuclear ribonucleoprotein F (hnRNPF), heterogeneous nuclear ribonucleoprotein K (hnRNPK), and Sjogren syndrome antigen B (SSB) to support selective mRNA translation following mTOR inhibition, which upregulates and activates proteins involved in insulin receptor (INSR)/insulin-like growth factor 1 receptor (IGF1R)/insulin receptor substrate (IRS) and interleukin 6 signal transducer (IL-6ST)/Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling. Our study highlights the mechanisms by which cells establish the dynamic change of proteostasis and the resulting phenotype switch.
    Keywords:  CP: Cell biology; CP: Molecular biology; eIF3D; eIF4E; mRNA translation; mTOR; proteome; proteostasis
    DOI:  https://doi.org/10.1016/j.celrep.2023.112868
  13. Biochem Pharmacol. 2023 Jul 22. pii: S0006-2952(23)00289-7. [Epub ahead of print]215 115698
    Dissecting the multifaced function of transcription factor EB (TFEB) in human diseases: From molecular mechanism to pharmacological modulation.
    Lijuan Zhang, Zhijia Li, Lan Zhang, Yuan Qin, Dongke Yu.
      The transcription factor EB (TFEB) is a transcription factor of the MiT/TFE family that translocations from the cytoplasm to the nucleus in response to various stimuli, including lysosomal stress and nutrient starvation. By activating genes involved in lysosomal function, autophagy, and lipid metabolism, TFEB plays a crucial role in maintaining cellular homeostasis. Dysregulation of TFEB has been implicated in various diseases, including cancer, neurodegenerative diseases, metabolic diseases, cardiovascular diseases, infectious diseases, and inflammatory diseases. Therefore, modulating TFEB activity with agonists or inhibitors may have therapeutic potential. In this review, we reviewed the recently discovered regulatory mechanisms of TFEB and their impact on human diseases. Additionally, we also summarize the existing TFEB inhibitors and agonists (targeted and non-targeted) and discuss unresolved issues and future research directions in the field. In summary, this review sheds light on the crucial role of TFEB, which may pave the way for its translation from basic research to practical applications, bringing us closer to realizing the full potential of TFEB in various fields.
    Keywords:  Autophagy; Human disease; Pharmacological modulator; TFEB
    DOI:  https://doi.org/10.1016/j.bcp.2023.115698
  14. Traffic. 2023 Jul 25.
    Restoration of β-GC trafficking improves the lysosome function in Gaucher disease.
    Saloni Patel, Dhwani Radhakrishnan, Darpan Kumari, Priyanka Bhansali, Subba Rao Gangi Setty.
      Lysosomes function as a primary site for catabolism and cellular signaling. These organelles digest a variety of substrates received through endocytosis, secretion and autophagy with the help of resident acid hydrolases. Lysosomal enzymes are folded in the endoplasmic reticulum (ER) and trafficked to lysosomes via Golgi and endocytic routes. The inability of hydrolase trafficking due to mutations or mutations in its receptor or cofactor leads to cargo accumulation (storage) in lysosomes, resulting in lysosome storage disorder (LSD). In Gaucher disease (GD), the lysosomes accumulate glucosylceramide because of low β-glucocerebrosidase (β-GC) activity that causes lysosome enlargement/dysfunction. We hypothesize that improving the trafficking of mutant β-GC to lysosomes may improve the lysosome function in GD. RNAi screen using high throughput based β-GC activity assay followed by reporter trafficking assay utilizing β-GC-mCherry led to the identification of nine potential phosphatases. Depletion of these phosphatases in HeLa cells enhanced the β-GC activity by increasing the folding and trafficking of Gaucher mutants to the lysosomes. Consistently, the lysosomes in primary fibroblasts from GD patients restored their β-GC activity upon the knockdown of these phosphatases. Thus, these studies provide evidence that altering phosphatome activity is an alternative therapeutic strategy to restore the lysosome function in GD.
    Keywords:  Gaucher disease; lysosome; lysosome storage diseases; phosphatome; β-glucocerebrosidase
    DOI:  https://doi.org/10.1111/tra.12911
  15. Autophagy. 2023 Jul 23. 1-7
    Should evidence of an autolysosomal de-acidification defect in Alzheimer and Parkinson diseases call for caution in prescribing chronic PPI and DMARD?
    Sandy Giuliano, Christopher Montemagno, Marie-Angela Domdom, Manon Teisseire, Patrick Brest, Daniel J Klionsky, Paul Hofman, Gilles Pagès, Baharia Mograbi.
      Nearly fifty million older people suffer from neurodegenerative diseases, including Alzheimer (AD) and Parkinson (PD) disease, a global burden expected to triple by 2050. Such an imminent "neurological pandemic" urges the identification of environmental risk factors that are hopefully avoided to fight the disease. In 2022, strong evidence in mouse models incriminated defective lysosomal acidification and impairment of the autophagy pathway as modifiable risk factors for dementia. To date, the most prescribed lysosomotropic drugs are proton pump inhibitors (PPIs), chloroquine (CQ), and the related hydroxychloroquine (HCQ), which belong to the group of disease-modifying antirheumatic drugs (DMARDs). This commentary aims to open the discussion on the possible mechanisms connecting the long-term prescribing of these drugs to the elderly and the incidence of neurodegenerative diseases.Abbreviations: AD: Alzheimer disease; APP-βCTF: amyloid beta precursor protein-C-terminal fragment; BACE1: beta-secretase 1; BBB: brain blood barrier; CHX: Ca2+/H+ exchanger; CMI: cognitive mild impairment; CQ: chloroquine; DMARD: disease-modifying antirheumatic drugs; GBA1: glucosylceramidase beta 1; HCQ: hydroxychloroquine; HPLC: high-performance liquid chromatography; LAMP: lysosomal associated membrane protein; MAPK/JNK: mitogen-activated protein kinase; MAPT: microtubule associated protein tau; MCOLN1/TRPML1: mucolipin TRP cation channel 1; NFE2L2/NRF2: NFE2 like bZIP transcription factor 2; NRBF2: nuclear receptor binding factor 2; PANTHOS: poisonous flower; PD: Parkinson disease; PIK3C3: phosphatIdylinositol 3-kinase catalytic subunit type 3; PPI: proton pump inhibitor; PSEN1: presenilin 1, RUBCN: rubicon autophagy regulator; RUBCNL: rubicon like autophagy enhancer; SQSTM1: sequestosome 1; TMEM175: transmembrane protein 175; TPCN2: two pore segment channel 2; VATPase: vacuolar-type H+-translocating ATPase; VPS13C: vacuolar protein sorting ortholog 13 homolog C; VPS35: VPS35 retromer complex component; WDFY3: WD repeat and FYVE domain containing 3; ZFYVE1: zinc finger FYVE-type containing 1.
    Keywords:  Autophagy; disease-modifying antirheumatic drugs; lysosome; neurodegenerative disease; proton pump inhibitor
    DOI:  https://doi.org/10.1080/15548627.2023.2214960
  16. Appl Biochem Biotechnol. 2023 Jul 26.
    Protective Autophagy Attenuates the Cytotoxicity of MTI-31 in Renal Cancer Cells by Activating the ERK Pathway.
    Yiwen Zang, Chen Yang, Meng-Shi Dai, Wenye Zhang, Lujia Zou, Jimeng Hu, Yun Hu, Chenyang Xu, Rongzong Liu, Hao Wang, Zuquan Xiong.
      The mammalian target of rapamycin (mTOR) is a key regulatory molecular target to treat cancer, and MTI-31 is a potent mTOR inhibitory agent for the therapeutically target of the renal cell carcinoma (RCC). However, the therapeutic efficacy of MTI-31 is limited by multiple factors, including autophagy. MTI-31 can activate cells to generate autophagy, which may in turn indirectly affect cell proliferation and apoptosis. We aimed to observe changes in cell protective autophagy via the ERK pathway and explore the potential mechanism underlying drug resistance of RCC cells to MTI-31. Different concentrations of 786-O and RCC4 cells were co-cultured with MTI-31 for distinct durations. The result of autophagy marker detection by Western blot showed that MTI-31 could induce RCC cells to produce autophagy in a dose and time-dependent manner. After treating the RCC cells with the autophagy inhibitor chloroquine (CQ), CCK8 and Western blot assays demonstrated that CQ could effectively enhance cell apoptosis induced by MTI-31 and that the autophagy induced by MTI-31 was cytoprotective. In addition, CCK8 and Western blot demonstrated that MTI-31 exerted its effect by activating the ERK pathway rather than the JNK or p38 pathway. The use of the ERK inhibitor AZD6244 to block the ERK pathway could effectively promote cell apoptosis induced by MTI-31. AZD6244 attenuated the autophagy induced by MTI-31 and increased the cytotoxicity of MTI-31. Western blot also demonstrated that MTI-31-induced autophagy was mediated by the downstream regulators of ERK pathways, including Beclin-1 and Bcl-2. It demonstrated that the MTI-31 mediated activation ERK pathway is associated with the induction of autophagy, and autophagy can attenuate the cytotoxicity of MTI-31 on RCC cells. In summary, inhibition of ERK pathway-mediated autophagy can rectify drug resistance to MTI-31 effectively.
    Keywords:  ERK pathway; Molecular target, autophagy; Renal cell carcinoma; mTOR
    DOI:  https://doi.org/10.1007/s12010-023-04569-9
  17. Sci Adv. 2023 Jul 28. 9(30): eadg1925
    Lysosomal dysfunction in Down syndrome and Alzheimer mouse models is caused by v-ATPase inhibition by Tyr682-phosphorylated APP βCTF.
    Eunju Im, Ying Jiang, Philip H Stavrides, Sandipkumar Darji, Hediye Erdjument-Bromage, Thomas A Neubert, Jun Yong Choi, Jerzy Wegiel, Ju-Hyun Lee, Ralph A Nixon.
      Lysosome dysfunction arises early and propels Alzheimer's disease (AD). Herein, we show that amyloid precursor protein (APP), linked to early-onset AD in Down syndrome (DS), acts directly via its β-C-terminal fragment (βCTF) to disrupt lysosomal vacuolar (H+)-adenosine triphosphatase (v-ATPase) and acidification. In human DS fibroblasts, the phosphorylated 682YENPTY internalization motif of APP-βCTF binds selectively within a pocket of the v-ATPase V0a1 subunit cytoplasmic domain and competitively inhibits association of the V1 subcomplex of v-ATPase, thereby reducing its activity. Lowering APP-βCTF Tyr682 phosphorylation restores v-ATPase and lysosome function in DS fibroblasts and in vivo in brains of DS model mice. Notably, lowering APP-βCTF Tyr682 phosphorylation below normal constitutive levels boosts v-ATPase assembly and activity, suggesting that v-ATPase may also be modulated tonically by phospho-APP-βCTF. Elevated APP-βCTF Tyr682 phosphorylation in two mouse AD models similarly disrupts v-ATPase function. These findings offer previously unknown insight into the pathogenic mechanism underlying faulty lysosomes in all forms of AD.
    DOI:  https://doi.org/10.1126/sciadv.adg1925
  18. Biomedicines. 2023 Jul 20. pii: 2050. [Epub ahead of print]11(7):
    The Complex Role of Chaperone-Mediated Autophagy in Cancer Diseases.
    Jing Liu, Lijuan Wang, Hua He, Yueying Liu, Yiqun Jiang, Jinfeng Yang.
      Chaperone-mediated autophagy (CMA) is a process that rapidly degrades proteins labeled with KFERQ-like motifs within cells via lysosomes to terminate their cellular functioning. Meanwhile, CMA plays an essential role in various biological processes correlated with cell proliferation and apoptosis. Previous studies have shown that CMA was initially found to be procancer in cancer cells, while some theories suggest that it may have an inhibitory effect on the progression of cancer in untransformed cells. Therefore, the complex relationship between CMA and cancer has aroused great interest in the application of CMA activity regulation in cancer therapy. Here, we describe the basic information related to CMA and introduce the physiological functions of CMA, the dual role of CMA in different cancer contexts, and its related research progress. Further study on the mechanism of CMA in tumor development may provide novel insights for tumor therapy targeting CMA. This review aims to summarize and discuss the complex mechanisms of CMA in cancer and related potential strategies for cancer therapy.
    Keywords:  autophagy; cancer protein; chaperone-mediated; degradation; lysosome
    DOI:  https://doi.org/10.3390/biomedicines11072050
  19. Int J Mol Sci. 2023 Jul 22. pii: 11811. [Epub ahead of print]24(14):
    mTOR Signaling Pathway and Gut Microbiota in Various Disorders: Mechanisms and Potential Drugs in Pharmacotherapy.
    Yuan Gao, Tian Tian.
      The mammalian or mechanistic target of rapamycin (mTOR) integrates multiple intracellular and extracellular upstream signals involved in the regulation of anabolic and catabolic processes in cells and plays a key regulatory role in cell growth and metabolism. The activation of the mTOR signaling pathway has been reported to be associated with a wide range of human diseases. A growing number of in vivo and in vitro studies have demonstrated that gut microbes and their complex metabolites can regulate host metabolic and immune responses through the mTOR pathway and result in disorders of host physiological functions. In this review, we summarize the regulatory mechanisms of gut microbes and mTOR in different diseases and discuss the crosstalk between gut microbes and their metabolites and mTOR in disorders in the gastrointestinal tract, liver, heart, and other organs. We also discuss the promising application of multiple potential drugs that can adjust the gut microbiota and mTOR signaling pathways. Despite the limited findings between gut microbes and mTOR, elucidating their relationship may provide new clues for the prevention and treatment of various diseases.
    Keywords:  gut microbes; mTOR; metabolites; therapy
    DOI:  https://doi.org/10.3390/ijms241411811
  20. Heliyon. 2023 Jun;9(6): e17392
    Rev1 deficiency induces a metabolic shift in MEFs that can be manipulated by the NAD+ precursor nicotinamide riboside.
    Sharath Anugula, Zhiquan Li, Yuan Li, Alexander Hendriksen, Peter Bjarn Christensen, Lin Wang, Jonathan M Monk, Niels de Wind, Vilhelm A Bohr, Claus Desler, Robert K Naviaux, Lene Juel Rasmussen.
      Replication stress, caused by Rev1 deficiency, is associated with mitochondrial dysfunction, and metabolic stress. However, the overall metabolic alterations and possible interventions to rescue the deficits due to Rev1 loss remain unclear. Here, we report that loss of Rev1 leads to intense changes in metabolites and that this can be manipulated by NAD + supplementation. Autophagy decreases in Rev1-/- mouse embryonic fibroblasts (MEFs) and can be restored by supplementing the NAD+ precursor nicotinamide riboside (NR). The abnormal mitochondrial morphology in Rev1-/- MEFs can be partially reversed by NR supplementation, which also protects the mitochondrial cristae from rotenone-induced degeneration. In nematodes rev-1 deficiency causes sensitivity to oxidative stress but this cannot be rescued by NR supplementation. In conclusion, Rev1 deficiency leads to metabolic dysregulation of especially lipid and nucleotide metabolism, impaired autophagy, and mitochondrial anomalies, and all of these phenotypes can be improved by NR replenishment in MEFs.
    Keywords:  Autophagy; Healthspan; Mitochondria; NAD+; Nicotinamide riboside; Replication stress; Rev1
    DOI:  https://doi.org/10.1016/j.heliyon.2023.e17392
  21. Antioxidants (Basel). 2023 Jul 14. pii: 1425. [Epub ahead of print]12(7):
    Autophagy, Oxidative Stress, and Alcoholic Liver Disease: A Systematic Review and Potential Clinical Applications.
    Daniel Salete-Granado, Cristina Carbonell, David Puertas-Miranda, Víctor-José Vega-Rodríguez, Marina García-Macia, Ana Belén Herrero, Miguel Marcos.
      Ethanol consumption triggers oxidative stress by generating reactive oxygen species (ROS) through its metabolites. This process leads to steatosis and liver inflammation, which are critical for the development of alcoholic liver disease (ALD). Autophagy is a regulated dynamic process that sequesters damaged and excess cytoplasmic organelles for lysosomal degradation and may counteract the harmful effects of ROS-induced oxidative stress. These effects include hepatotoxicity, mitochondrial damage, steatosis, endoplasmic reticulum stress, inflammation, and iron overload. In liver diseases, particularly ALD, macroautophagy has been implicated as a protective mechanism in hepatocytes, although it does not appear to play the same role in stellate cells. Beyond the liver, autophagy may also mitigate the harmful effects of alcohol on other organs, thereby providing an additional layer of protection against ALD. This protective potential is further supported by studies showing that drugs that interact with autophagy, such as rapamycin, can prevent ALD development in animal models. This systematic review presents a comprehensive analysis of the literature, focusing on the role of autophagy in oxidative stress regulation, its involvement in organ-organ crosstalk relevant to ALD, and the potential of autophagy-targeting therapeutic strategies.
    Keywords:  alcohol; alcoholic liver disease; antioxidant; autophagy; ethanol; macroautophagy; mitophagy; oxidative stress; rapamycin; redox
    DOI:  https://doi.org/10.3390/antiox12071425
  22. Diabetologia. 2023 Jul 22.
    Hyperglucagonaemia in diabetes: altered amino acid metabolism triggers mTORC1 activation, which drives glucagon production.
    Yael Riahi, Aviram Kogot-Levin, Liat Kadosh, Bella Agranovich, Assaf Malka, Michael Assa, Ron Piran, Dana Avrahami, Benjamin Glaser, Eyal Gottlieb, Fields Jackson, Erol Cerasi, Ernesto Bernal-Mizrachi, Aharon Helman, Gil Leibowitz.
      AIM/HYPOTHESIS: Hyperglycaemia is associated with alpha cell dysfunction, leading to dysregulated glucagon secretion in type 1 and type 2 diabetes; however, the mechanisms involved are still elusive. The nutrient sensor mammalian target of rapamycin complex 1 (mTORC1) plays a major role in the maintenance of alpha cell mass and function. We studied the regulation of alpha cell mTORC1 by nutrients and its role in the development of hyperglucagonaemia in diabetes.METHODS: Alpha cell mTORC1 activity was assessed by immunostaining for phosphorylation of its downstream target, the ribosomal protein S6, and glucagon, followed by confocal microscopy on pancreatic sections and flow cytometry on dispersed human and mouse islets and the alpha cell line, αTC1-6. Metabolomics and metabolic flux were studied by 13C glucose labelling in 2.8 or 16.7 mmol/l glucose followed by LC-MS analysis. To study the role of mTORC1 in mediating hyperglucagonaemia in diabetes, we generated an inducible alpha cell-specific Rptor knockout in the Akita mouse model of diabetes and tested the effects on glucose tolerance by IPGTT and on glucagon secretion.
    RESULTS: mTORC1 activity was increased in alpha cells from diabetic Akita mice in parallel to the development of hyperglycaemia and hyperglucagonaemia (two- to eightfold increase). Acute exposure of mouse and human islets to amino acids stimulated alpha cell mTORC1 (3.5-fold increase), whereas high glucose concentrations inhibited mTORC1 (1.4-fold decrease). The mTORC1 response to glucose was abolished in human and mouse diabetic alpha cells following prolonged islet exposure to high glucose levels, resulting in sustained activation of mTORC1, along with increased glucagon secretion. Metabolomics and metabolic flux analysis showed that exposure to high glucose levels enhanced glycolysis, glucose oxidation and the synthesis of glucose-derived amino acids. In addition, chronic exposure to high glucose levels increased the expression of Slc7a2 and Slc38a4, which encode amino acid transporters, as well as the levels of branched-chain amino acids and methionine cycle metabolites (~1.3-fold increase for both). Finally, conditional Rptor knockout in alpha cells from adult diabetic mice inhibited mTORC1, thereby inhibiting glucagon secretion (~sixfold decrease) and improving diabetes, despite persistent insulin deficiency.
    CONCLUSIONS/INTERPRETATION: Alpha cell exposure to hyperglycaemia enhances amino acid synthesis and transport, resulting in sustained activation of mTORC1, thereby increasing glucagon secretion. mTORC1 therefore plays a major role in mediating alpha cell dysfunction in diabetes.
    DATA AVAILABILITY: All sequencing data are available from the Gene Expression Omnibus (GEO) repository (accession no. GSE154126; https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE154126 ).
    Keywords:  Alpha cells; Diabetes; Glucagon; Islet biology; Metabolism; mTORC1
    DOI:  https://doi.org/10.1007/s00125-023-05967-8
  23. Cell Rep. 2023 Jul 21. pii: S2211-1247(23)00863-X. [Epub ahead of print]42(8): 112852
    Small cytosolic double-stranded DNA represses cyclic GMP-AMP synthase activation and induces autophagy.
    Yao Liu, Xiao Chen, Yuemei Zhao, Xing-Yue Wang, Yu-Wei Luo, Lina Chen, Weiyun Wang, Shouhui Zhong, Meizhen Hu, Zhizheng Dai, Jiayu Jiang, Xin Wang, Hongyu Ji, Xiao-Xiao Cheng, Anqi Zheng, Jiwei Zuo, Hui Liu, Di Ma, Zhicheng Luo, Fang Cao, Shanshan Hu, Ai-Long Huang, Kai-Fu Tang.
      The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway is a major mediator of inflammation following stimulation with >45 bp double-stranded DNA (dsDNA). Herein, we identify a class of ∼20-40 bp small cytosolic dsDNA (scDNA) molecules that compete with long dsDNA (200-1,500 bp herring testis [HT]-DNA) for binding to cGAS, thus repressing HT-DNA-induced cGAS activation. The scDNA promotes cGAS and Beclin-1 interaction, releasing Rubicon, a negative regulator of phosphatidylinositol 3-kinase class III (PI3KC3), from the Beclin-1-PI3KC3 complex. This leads to PI3KC3 activation and induces autophagy, causing degradation of STING and long cytosolic dsDNA. Moreover, DNA damage decreases, and autophagy inducers increase scDNA levels. scDNA transfection and treatment with autophagy inducers attenuate DNA damage-induced cGAS activation. Thus, scDNA molecules serve as effective brakes for cGAS activation, preventing excessive inflammatory cytokine production following DNA damage. Our findings may have therapeutic implications for cytosolic DNA-associated inflammatory diseases.
    Keywords:  CP: Immunology; CP: Molecular biology; DNA damage; PI3KC3; STING; autophagy; cGAS; interferon β; small cytosolic double-stranded DNA
    DOI:  https://doi.org/10.1016/j.celrep.2023.112852
  24. Antioxidants (Basel). 2023 Jul 10. pii: 1406. [Epub ahead of print]12(7):
    Linking ROS Levels to Autophagy: The Key Role of AMPK.
    Francesco Agostini, Marco Bisaglia, Nicoletta Plotegher.
      Oxygen reactive species (ROS) are a group of molecules generated from the incomplete reduction of oxygen. Due to their high reactivity, ROS can interact with and influence the function of multiple targets, which include DNA, lipids, and proteins. Among the proteins affected by ROS, AMP-activated protein kinase (AMPK) is considered a major sensor of the intracellular energetic status and a crucial hub involved in the regulation of key cellular processes, like autophagy and lysosomal function. Thanks to these features, AMPK has been recently demonstrated to be able to perceive signals related to the variation of mitochondrial dynamics and to transduce them to the lysosomes, influencing the autophagic flux. Since ROS production is largely dependent on mitochondrial activity, through the modulation of AMPK these molecules may represent important signaling agents which participate in the crosstalk between mitochondria and lysosomes, allowing the coordination of these organelles' functions. In this review, we will describe the mechanisms through which ROS activate AMPK and the signaling pathways that allow this protein to affect the autophagic process. The picture that emerges from the literature is that AMPK regulation is highly tissue-specific and that different pools of AMPK can be localized at specific intracellular compartments, thus differentially responding to altered ROS levels. For this reason, future studies will be highly advisable to discriminate the specific contribution of the activation of different AMPK subpopulations to the autophagic pathway.
    Keywords:  AMPK; ROS; autophagy; lysosomes; mitochondria
    DOI:  https://doi.org/10.3390/antiox12071406
  25. Neural Regen Res. 2024 Feb;19(2): 316-323
    Mitophagy in intracerebral hemorrhage: a new target for therapeutic intervention.
    Yiyang Chen, Wenxuan Tang, Xinqi Huang, Yumei An, Jiawen Li, Shengye Yuan, Haiyan Shan, Mingyang Zhang.
      Intracerebral hemorrhage is a life-threatening condition with a high fatality rate and severe sequelae. However, there is currently no treatment available for intracerebral hemorrhage, unlike for other stroke subtypes. Recent studies have indicated that mitochondrial dysfunction and mitophagy likely relate to the pathophysiology of intracerebral hemorrhage. Mitophagy, or selective autophagy of mitochondria, is an essential pathway to preserve mitochondrial homeostasis by clearing up damaged mitochondria. Mitophagy markedly contributes to the reduction of secondary brain injury caused by mitochondrial dysfunction after intracerebral hemorrhage. This review provides an overview of the mitochondrial dysfunction that occurs after intracerebral hemorrhage and the underlying mechanisms regarding how mitophagy regulates it, and discusses the new direction of therapeutic strategies targeting mitophagy for intracerebral hemorrhage, aiming to determine the close connection between mitophagy and intracerebral hemorrhage and identify new therapies to modulate mitophagy after intracerebral hemorrhage. In conclusion, although only a small number of drugs modulating mitophagy in intracerebral hemorrhage have been found thus far, most of which are in the preclinical stage and require further investigation, mitophagy is still a very valid and promising therapeutic target for intracerebral hemorrhage in the long run.
    Keywords:  intracerebral hemorrhage; mitochondrial dysfunction; mitophagy; neuroinflammation; neuroprotection; reactive oxygen species; secondary brain injury; therapeutic target
    DOI:  https://doi.org/10.4103/1673-5374.379019
  26. Cells. 2023 Jul 12. pii: 1835. [Epub ahead of print]12(14):
    Modulation of Lysosomal Cl- Mediates Migration and Apoptosis through the TRPML1 as a Lysosomal Cl- Sensor.
    Dongun Lee, Jeong Hee Hong.
      Lysosomes are responsible for protein degradation and clearance in cellular recycling centers. It has been known that the lysosomal chloride level is enriched and involved in the intrinsic lysosomal function. However, the mechanism by which chloride levels can be sensed and that of the chloride-mediated lysosomal function is unknown. In this study, we verified that reduced chloride levels acutely induced lysosomal calcium release through TRPML1 and lysosomal repositioning toward the juxtanuclear region. Functionally, low chloride-induced lysosomal calcium release attenuated cellular migration. In addition, spontaneous exposure to low chloride levels dysregulated lysosomal biogenesis and subsequently induced delayed migration and promoted apoptosis. Two chloride-sensing GXXXP motifs in the TRPML1 were identified. Mutations in the GXXXP motif of TRPML1 did not affect chloride levels, and there were no changes in migratory ability. In this study, we demonstrated that the depletion of chloride induces reformation of the lysosomal calcium pool and subsequently dysregulated cancer progression, which will assist in improving therapeutic strategies for lysosomal accumulation-associated diseases or cancer cell apoptosis.
    Keywords:  GXXXP motif; TRPML1; calcium; chloride; lysosome
    DOI:  https://doi.org/10.3390/cells12141835
  27. Proc Natl Acad Sci U S A. 2023 Aug;120(31): e2303789120
    LRRK2 suppresses lysosome degradative activity in macrophages and microglia through MiT-TFE transcription factor inhibition.
    Narayana Yadavalli, Shawn M Ferguson.
      Cells maintain optimal levels of lysosome degradative activity to protect against pathogens, clear waste, and generate nutrients. Here, we show that LRRK2, a protein that is tightly linked to Parkinson's disease, negatively regulates lysosome degradative activity in macrophages and microglia via a transcriptional mechanism. Depletion of LRRK2 and inhibition of LRRK2 kinase activity enhanced lysosomal proteolytic activity and increased the expression of multiple lysosomal hydrolases. Conversely, the kinase hyperactive LRRK2 G2019S Parkinson's disease mutant suppressed lysosomal degradative activity and gene expression. We identified MiT-TFE transcription factors (TFE3, TFEB, and MITF) as mediators of LRRK2-dependent control of lysosomal gene expression. LRRK2 negatively regulated the abundance and nuclear localization of these transcription factors and their depletion prevented LRRK2-dependent changes in lysosome protein levels. These observations define a role for LRRK2 in controlling lysosome degradative activity and support a model wherein LRRK2 hyperactivity may increase Parkinson's disease risk by suppressing lysosome degradative activity.
    Keywords:  Parkinson’s disease; lysosome; macrophage; microglia
    DOI:  https://doi.org/10.1073/pnas.2303789120
  28. Exp Neurol. 2023 Jul 24. pii: S0014-4886(23)00180-2. [Epub ahead of print] 114495
    Stub1 ameliorates ER stress-induced neural cell apoptosis and promotes locomotor recovery through restoring autophagy flux after spinal cord injury.
    Ermei Lu, Yingdan Tang, Jiaojiao Chen, Abdullah Al Mamun, Zhiyi Feng, Lin Cao, Xie Zhang, Yunsen Zhu, Tingting Mo, ChangJu Chun, Hongyu Zhang, Jiqing Du, Chang Jiang, Jian Xiao.
      Endoplasmic reticulum (ER) stress-induced apoptosis and autophagy flux blockade significantly contribute to neuronal pathology of spinal cord injury (SCI). Yet, the molecular interplay between these two distinctive pathways in mediating the pathology of SCI remains largely unexplored. Currently, we aimed at exploring the crucial role of Stub1 in maintaining ER homeostasis and regulating autophagic flux after SCI. Our results demonstrate that Stub1 reduces ER stress induced neuronal apoptosis, promotes axonal regeneration, inhibits glial scar formation and fosters functional recovery by restoring autophagic flux following SCI. Stub1 enhances autophagic flux following SCI by alleviating the permeabilization of lysosomal membrane through activating TFEB. Importantly, we showed that Stub1 promotes the activation of TFEB by targeting HDAC2 for ubiquitination and degradation. Furthermore, the neuroprotective effect of Stub1 on SCI was abrogated by chloroquine administration, underscoring the essential role of Stub1-mediated enhancement of autophagic flux in its protective effects against SCI. Collectively, our data highlights the vital role of Stub1 in regulating ER stress and autophagy flux after SCI, and propose its potential as a promising target for neuroprotective interventions in SCI.
    Keywords:  Autophagy-lysosomal pathway; ER stress; Spinal cord injury; Stub1
    DOI:  https://doi.org/10.1016/j.expneurol.2023.114495
  29. Medicine (Baltimore). 2023 Jul 28. 102(30): e33965
    Pathophysiology of diabetic kidney disease and autophagy: A review.
    Jiawei Yu, Yan Liu, Hongjie Li, Peirong Zhang.
      Diabetic kidney disease (DKD) is one of the main complications of diabetic microangiopathy. The pathogenesis of DKD is very complex, including autophagy, inflammation, oxidative stress. Although a series of treatment intervention have achieved certain results in the treatment of diabetic nephropathy, still cannot reverse the kidney injury of diabetic nephropathy. The kidney is one of the most important organs of energy metabolism. Renal function is highly dependent on phagocytosis of mitochondria, and aberrant or defective autophagic mechanisms are central to the pathology of many renal diseases. Under high glucose conditions, mitochondrial fragments accumulate in the kidney, suggesting that mitochondrial clearance mechanisms may be attenuated with changes in mitochondrial transformation mechanisms. However, the exact mechanism of mitophagy regulation in DKD has not been elucidated. Recent advances in autophagy have renewed interest in these signaling pathways and molecules in the pathogenesis of DKD. Investigating autophagy and its associated signaling molecules may provide potential unique targets for therapeutic intervention in DKD.
    DOI:  https://doi.org/10.1097/MD.0000000000033965
  30. Dev Cell. 2023 Jul 22. pii: S1534-5807(23)00334-9. [Epub ahead of print]
    Calnexin controls TrkB cell surface transport and ER-phagy in mouse cerebral cortex development.
    Patrick Lüningschrör, Thomas Andreska, Alexander Veh, Daniel Wolf, Neha Jadhav Giridhar, Mehri Moradi, Angela Denzel, Michael Sendtner.
      Transactivation of Tropomyosin receptor kinase B (TrkB) by EGF leads to cell surface transport of TrkB, promoting its signaling responsiveness to brain-derived neurotrophic factor (BDNF), a critical process for proper cortical plate development. However, the mechanisms that regulate the transport of TrkB to the cell surface are not fully understood. Here, we identified Calnexin as a regulator for targeting TrkB either to the cell surface or toward autophagosomal processing. Calnexin-deficient mouse embryos show impaired cortical plate formation and elevated levels of transactivated TrkB. In Calnexin-depleted mouse neuronal precursor cells, we detected an impaired cell surface transport of TrkB in response to EGF and an impaired delivery to autophagosomes. Mechanistically, we show that Calnexin facilitates the interaction of TrkB with the ER-phagy receptor Fam134b, thereby targeting TrkB to ER-phagy. This mechanism appears as a critical process for fine-tuning the sensitivity of neurons to BDNF.
    Keywords:  BDNF; Calnexin; EGF; ER-phagy; TrkB; autophagy; transactivation
    DOI:  https://doi.org/10.1016/j.devcel.2023.07.004
  31. Autophagy. 2023 Jul 28. 1-29
    The constructive and destructive impact of autophagy on both genders' reproducibility, a comprehensive review.
    Mohammad Samare-Najaf, Asma Neisy, Ali Samareh, Delaram Moghadam, Navid Jamali, Reza Zarei, Fatemeh Zal.
      Reproduction is characterized by a series of massive renovations at molecular, cellular, and tissue levels. Recent studies have strongly tended to reveal the involvement of basic molecular pathways such as autophagy, a highly conserved eukaryotic cellular recycling, during reproductive processes. This review comprehensively describes the current knowledge, updated to September 2022, of autophagy contribution during reproductive processes in males including spermatogenesis, sperm motility and viability, and male sex hormones and females including germ cells and oocytes viability, ovulation, implantation, fertilization, and female sex hormones. Furthermore, the consequences of disruption in autophagic flux on the reproductive disorders including oligospermia, azoospermia, asthenozoospermia, teratozoospermia, globozoospermia, premature ovarian insufficiency, polycystic ovarian syndrome, endometriosis, and other disorders related to infertility are discussed as well.Abbreviations: AKT/protein kinase B: AKT serine/threonine kinase; AMPK: AMP-activated protein kinase; ATG: autophagy related; E2: estrogen; EDs: endocrine disruptors; ER: endoplasmic reticulum; FSH: follicle stimulating hormone; FOX: forkhead box; GCs: granulosa cells; HIF: hypoxia inducible factor; IVF: in vitro fertilization; IVM: in vitro maturation; LCs: Leydig cells; LDs: lipid droplets; LH: luteinizing hormone; LRWD1: leucine rich repeats and WD repeat domain containing 1; MAP1LC3: microtubule associated protein 1 light chain 3; MAPK: mitogen-activated protein kinase; MTOR: mechanistic target of rapamycin kinase; NFKB/NF-kB: nuclear factor kappa B; P4: progesterone; PCOS: polycystic ovarian syndrome; PDLIM1: PDZ and LIM domain 1; PI3K: phosphoinositide 3-kinase; PtdIns3P: phosphatidylinositol-3-phosphate; PtdIns3K: class III phosphatidylinositol 3-kinase; POI: premature ovarian insufficiency; ROS: reactive oxygen species; SCs: Sertoli cells; SQSTM1/p62: sequestosome 1; TSGA10: testis specific 10; TST: testosterone; VCP: vasolin containing protein.
    Keywords:  Apoptosis; autophagy; fertility; follicles; granulosa cells; infertility
    DOI:  https://doi.org/10.1080/15548627.2023.2238577
  32. Int J Mol Sci. 2023 Jul 14. pii: 11440. [Epub ahead of print]24(14):
    miR-29a-3p Regulates Autophagy by Targeting Akt3-Mediated mTOR in SiO2-Induced Lung Fibrosis.
    Peiyuan Li, Xiaohui Hao, Jiaxin Liu, Qinxin Zhang, Zixuan Liang, Xinran Li, Heliang Liu.
      Silicosis is a refractory pneumoconiosis of unknown etiology that is characterized by diffuse lung fibrosis, and microRNA (miRNA) dysregulation is connected to silicosis. Emerging evidence suggests that miRNAs modulate pulmonary fibrosis through autophagy; however, its underlying molecular mechanism remains unclear. In agreement with miRNA microarray analysis, the qRT-PCR results showed that miR-29a-3p was significantly decreased in the pulmonary fibrosis model both in vitro and in vivo. Increased autophagosome was observed via transmission electron microscopy in lung epithelial cell models and lung tissue of silicosis mice. The expression of autophagy-related proteins LC3α/β and Beclin1 were upregulated. The results from using 3-methyladenine, an autophagy inhibitor, or rapamycin, an autophagy inducer, together with TGF-β1, indicated that autophagy attenuates fibrosis by protecting lung epithelial cells. In TGF-β1-treated TC-1 cells, transfection with miR-29a-3p mimics activated protective autophagy and reduced alpha-smooth muscle actin and collagen I expression. miRNA TargetScan predicted, and dual-luciferase reporter experiments identified Akt3 as a direct target of miR-29a-3p. Furthermore, Akt3 expression was significantly elevated in the silicosis mouse model and TGF-β1-treated TC-1 cells. The mammalian target of rapamycin (mTOR) is a central regulator of the autophagy process. Silencing Akt3 inhibited the transduction of the mTOR signaling pathway and activated autophagy in TGF-β1-treated TC-1 cells. These results show that miR-29a-3p overexpression can partially reverse the fibrotic effects by activating autophagy of the pulmonary epithelial cells regulated by the Akt3/mTOR pathway. Therefore, targeting miR-29a-3p may provide a new therapeutic strategy for silica-induced pulmonary fibrosis.
    Keywords:  autophagy; lung epithelial cell; miRNA microarray analysis; silicosis
    DOI:  https://doi.org/10.3390/ijms241411440
  33. Autophagy. 2023 Jul 28. 1-18
    Starvation-inactivated MTOR triggers cell migration via a ULK1-SH3PXD2A/TKS5-MMP14 pathway in ovarian carcinoma.
    Chiao-Yun Lin, Kai-Yun Wu, Lang-Ming Chi, Yun-Hsin Tang, Huei-Jean Huang, Chyong-Huey Lai, Chi-Neu Tsai, Chia-Lung Tsai.
      ABBREVIATIONS: AMPK: AMP-activated protein kinase; CHX: cycloheximide; RAD001: everolimus; HBSS: Hanks' balanced salt solution; LC-MS/MS: liquid chromatography-mass spectrometry/mass spectrometry; MMP14: matrix metallopeptidase 14; MTOR: mechanistic target of rapamycin kinase; MAPK: mitogen-activated protein kinase; RB1CC1/FIP200: RB1 inducible coiled-coil 1; PtdIns3P: phosphatidylinositol-3-phosphate; PX: phox homology; SH3: Src homology 3; SH3PXD2A/TKS5: SH3 and PX domains 2A; SH3PXD2A-[6A]: S112A S142A S146A S147A S175A S348A mutant; ULK1: unc-51 like autophagy activating kinase 1.
    Keywords:  MMP14; SH3PXD2A; ULK1; cellular migration; ovarian cancer
    DOI:  https://doi.org/10.1080/15548627.2023.2239633
  34. Biomedicines. 2023 Jun 24. pii: 1811. [Epub ahead of print]11(7):
    An Autophagy-Associated MITF-GAS5-miR-23 Loop Attenuates Vascular Oxidative and Inflammatory Damage in Sepsis.
    Junning Cheng, Chang Ding, Huying Tang, Haonan Zhou, Mingdong Wu, Yikuan Chen.
      BACKGROUND: Sepsis induces GAS5 expression in the vascular endothelium, but the molecular mechanism is unclear, as is the role of GAS5 in sepsis.METHODS AND RESULTS: We observed that GAS5 expression in the endothelium was significantly upregulated in a sepsis mouse model. ChIP-PCR and EMSA confirmed that the oxidative stress (OS)-activated MiT-TFE transcription factor (MITF, TFE3, and TFEB)-mediated GAS5 transcription. In vitro, GAS5 overexpression attenuated OS and inflammation in endothelial cells (ECs) while maintaining the structural and functional integrity of mitochondria. In vivo, GAS5 reduced tissue ROS levels, maintained vascular barrier function to reduce leakage, and ultimately attenuated sepsis-induced lung injury. Luciferase reporter assays revealed that GAS5 protected MITF from degradation by sponging miR-23, thereby forming a positive feedback loop consisting of MITF, GAS5, and miR-23. Despite the fact that the OS-activated MITF-GAS5-miR-23 loop boosted MITF-mediated p62 transcription, ECs do not need to increase mitophagy to exert mitochondrial quality control since MITF-mediated Nrf2 transcription exists. Compared to mitophagy, MITF-transcribed p62 prefers to facilitate the autophagic degradation of Keap1 through a direct interaction, thereby relieving the inhibition of Nrf2 by Keap1, indicating that MITF can upregulate Nrf2 at both the transcriptional and posttranscriptional levels. Following this, ChIP-PCR demonstrated that Nrf2 can also transcribe MITF, revealing that there is a reciprocal positive regulatory association between MITF and Nrf2.
    CONCLUSION: In sepsis, the ROS-activated MITF-GAS5-miR-23 loop integrated the antioxidant and autophagy systems through MITF-mediated transcription of Nrf2 and p62, which dynamically regulate the level and type of autophagy, as well as exert antioxidant and anti-inflammatory effects.
    Keywords:  MiT–TFE transcription factor; autophagy; inflammation; oxidative stress; sepsis
    DOI:  https://doi.org/10.3390/biomedicines11071811
  35. Cell Death Dis. 2023 07 25. 14(7): 464
    Autophagy mediates an amplification loop during ferroptosis.
    Seunghee Lee, Narae Hwang, Byeong Geun Seok, Sangguk Lee, Seon-Jin Lee, Su Wol Chung.
      Ferroptosis, a programmed cell death, has been identified and associated with cancer and various other diseases. Ferroptosis is defined as a reactive oxygen species (ROS)-dependent cell death related to iron accumulation and lipid peroxidation, which is different from apoptosis, necrosis, autophagy, and other forms of cell death. However, accumulating evidence has revealed a link between autophagy and ferroptosis at the molecular level and has suggested that autophagy is involved in regulating the accumulation of iron-dependent lipid peroxidation and ROS during ferroptosis. Understanding the roles and pathophysiological processes of autophagy during ferroptosis may provide effective strategies for the treatment of ferroptosis-related diseases. In this review, we summarize the current knowledge regarding the regulatory mechanisms underlying ferroptosis, including iron and lipid metabolism, and its association with the autophagy pathway. In addition, we discuss the contribution of autophagy to ferroptosis and elucidate the role of autophagy as a ferroptosis enhancer during ROS-dependent ferroptosis.
    DOI:  https://doi.org/10.1038/s41419-023-05978-8
  36. Cell Rep. 2023 Jul 25. pii: S2211-1247(23)00849-5. [Epub ahead of print]42(8): 112838
    Increased degradation of FMRP contributes to neuronal hyperexcitability in tuberous sclerosis complex.
    Kellen D Winden, Truc T Pham, Nicole A Teaney, Juan Ruiz, Ryan Chen, Cidi Chen, Mustafa Sahin.
      Autism spectrum disorder (ASD) is a highly prevalent neurodevelopmental disorder, but new therapies have been impeded by a lack of understanding of the pathological mechanisms. Tuberous sclerosis complex (TSC) and fragile X syndrome are associated with alterations in the mechanistic target of rapamycin (mTOR) and fragile X messenger ribonucleoprotein 1 (FMRP), which have been implicated in the development of ASD. Previously, we observed that transcripts associated with FMRP were down-regulated in TSC2-deficient neurons. In this study, we find that FMRP turnover is dysregulated in TSC2-deficient rodent primary neurons and human induced pluripotent stem cell (iPSC)-derived neurons and is dependent on the E3 ubiquitin ligase anaphase-promoting complex. We also demonstrate that overexpression of FMRP can partially rescue hyperexcitability in TSC2-deficient iPSC-derived neurons. These data indicate that FMRP dysregulation represents an important pathological mechanism in the development of abnormal neuronal activity in TSC and illustrate a molecular convergence between these two neurogenetic disorders.
    Keywords:  CP: Neuroscience; autism spectrum disorder; fragile X messenger ribonucleoprotein 1; iPSC-derived neuron; tuberous sclerosis complex
    DOI:  https://doi.org/10.1016/j.celrep.2023.112838
  37. Geroscience. 2023 Jul 27.
    Basal autophagic flux measured in blood correlates positively with age in adults at increased risk of type 2 diabetes.
    Julien Bensalem, Xiao Tong Teong, Kathryn J Hattersley, Leanne K Hein, Célia Fourrier, Kai Liu, Amy T Hutchison, Leonie K Heilbronn, Timothy J Sargeant.
      Preclinical data show that autophagy delays age-related disease. It has been postulated that age-related disease is-at least in part-caused by an age-related decline in autophagy. However, autophagic flux has never been measured in humans across a spectrum of aging in a physiologically relevant context. To address this critical gap in knowledge, the objective of this cross-sectional observational study was to measure basal autophagic flux in whole blood taken from people at elevated risk of developing type 2 diabetes and correlate it with chronological age. During this study, 119 people were recruited and five people were excluded during sample analysis such that 114 people were included in the final analysis. Basal autophagic flux measured in blood and correlations with parameters such as age, body weight, fat mass, AUSDRISK score, blood pressure, glycated hemoglobin HbA1c, blood glucose and insulin, blood lipids, high-sensitivity C-reactive protein, plasma protein carbonylation, and plasma β-hexosaminidase activity were analysed. Despite general consensus in the literature that autophagy decreases with age, we found that basal autophagic flux increased with age in this human cohort. This is the first study to report measurement of basal autophagic flux in a human cohort and its correlation with age. This increase in basal autophagy could represent a stress response to age-related damage. These data are significant not only for their novelty but also because they will inform future clinical studies and show that measurement of basal autophagic flux in a human cohort is feasible.
    Keywords:  Aging; Autophagy; Cell biology; Diabetes; Human
    DOI:  https://doi.org/10.1007/s11357-023-00884-5
  38. Cells. 2023 Jul 12. pii: 1830. [Epub ahead of print]12(14):
    A Role of PI3K/Akt Signaling in Oocyte Maturation and Early Embryo Development.
    Jaroslav Kalous, Daria Aleshkina, Martin Anger.
      A serine/threonine-specific protein kinase B (PKB), also known as Akt, is a key factor in the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway that regulates cell survival, metabolism and proliferation. Akt phosphorylates many downstream specific substrates, which subsequently control the nuclear envelope breakdown (NEBD), centrosome maturation, spindle assembly, chromosome segregation, and cytokinesis. In vertebrates, Akt is also an important player during oogenesis and preimplantation development. In the signaling pathways regulating mRNA translation, Akt is involved in the control of mammalian target of rapamycin complex 1 (mTORC1) and thereby regulates the activity of a translational repressor, the eukaryotic initiation factor 4E (eIF4E) binding protein 1 (4E-BP1). In this review, we summarize the functions of Akt in mitosis, meiosis and early embryonic development. Additionally, the role of Akt in the regulation of mRNA translation is addressed with respect to the significance of this process during early development.
    Keywords:  Akt kinase; early embryo; mRNA translation; mTORC1; meiosis; mitosis; oocyte; spindle
    DOI:  https://doi.org/10.3390/cells12141830
  39. Food Chem Toxicol. 2023 Jul 20. pii: S0278-6915(23)00356-3. [Epub ahead of print]179 113954
    Arsenic induced autophagy-dependent apoptosis in hippocampal neurons via AMPK/mTOR signaling pathway.
    Yao Chen, Xudan Liu, Qianhui Zhang, Huanhuan Wang, Ruo Zhang, Yanhong Ge, Huning Liang, Wanying Li, Juanjun Fan, Huimin Liu, Zhengyang Lv, Wenting Dou, Yi Wang, Xin Li.
      Arsenic contamination of groundwater remains a serious public health problem worldwide. Arsenic-induced neurotoxicity receives increasing attention, however, the mechanism remains unclear. Hippocampal neuronal death is regarded as the main event of arsenic-induced cognitive dysfunction. Mitochondria lesion is closely related to cell death, however, the effects of arsenic on PGAM5-regulated mitochondrial dynamics has not been documented. Crosstalk between autophagy and apoptosis is complicated and autophagy has a dual role in the apoptosis pathways in neuronal cells. In this study, arsenic exposure resulted in mitochondrial PGAM5 activation and subsequent activation of apoptosis and AMPK-mTOR dependent autophagy. Intervention by autophagy activator Rapamycin or inhibitor 3-MA, both targeting at mTOR, accordingly induced activation or inhibition of apoptosis. Intervention by MK-3903 or dorsomorphin, activator or inhibitor of AMPK, received similar results. Our findings suggested that arsenic-induced PGAM5 activation played a role in AMPK-mTOR dependent autophagy and arsenic induced autophagy-dependent apoptosis in hippocampal neurons via AMPK/mTOR signaling pathway.
    Keywords:  AMPK; Apoptosis; Arsenic; Autophagy; Neurotoxicity; PGAM5
    DOI:  https://doi.org/10.1016/j.fct.2023.113954
  40. MedComm (2020). 2023 Aug;4(4): e309
    TRAF6 regulates autophagy and apoptosis of melanoma cells through c-Jun/ATG16L2 signaling pathway.
    Yeye Guo, Xu Zhang, Jie Li, Zhe Zhou, Susi Zhu, Waner Liu, Juan Su, Xiang Chen, Cong Peng.
      Autophagy and apoptosis are essential processes that participate in cell death and maintain cellular homeostasis. Dysregulation of these biological processes results in the development of diseases, including cancers. Therefore, targeting the interaction between apoptosis and autophagy offers a potential strategy for cancer therapy. Melanoma is the most lethal skin cancer. We previously found that tumor necrosis factor receptor-associated factor 6 (TRAF6) is overexpressed in melanoma and benefits the malignant phenotype of melanoma cells. Additionally, TRAF6 promotes the activation of cancer-associated fibroblasts in melanoma. However, the role of TRAF6 in autophagy and apoptosis remains unclear. In this study, we found that knockdown of TRAF6 induced both apoptosis and autophagy in melanoma cells. Transcriptomic data and real-time PCR analysis demonstrated reduced expression of autophagy related 16 like 2 (ATG16L2) in TRAF6-deficient melanoma cells. ATG16L2 knockdown resulted in increased autophagy and apoptosis. Mechanism studies confirmed that TRAF6 regulated ATG16L2 expression through c-Jun. Importantly, targeting TRAF6 with cinchonine, a TRAF6 inhibitor, effectively suppressed the growth of melanoma cells by inducing autophagy and apoptosis through the TRAF6/c-Jun/ATG16L2 signaling pathway. These findings highlight the pivotal role of TRAF6 in regulating autophagy and apoptosis in melanoma, emphasizing its significance as a novel therapeutic target for melanoma treatment.
    Keywords:  ATG16L2; TRAF6; apoptosis; autophagy; c‐Jun; melanoma
    DOI:  https://doi.org/10.1002/mco2.309
  41. BMC Nephrol. 2023 07 22. 24(1): 217
    KLHL3-dependent WNK4 degradation affected by potassium through the neddylation and autophagy pathway.
    Siqi Ying, Qin Guo, Chong Zhang.
      BACKGROUND: Studies reported that kelch-like protein 3 (KLHL3)-Cullin3(CUL3) E3 ligase ubiquitinated with-no-lysine kinase 4 (WNK4). Impaired WNK4 ubiquitination plays a key role in Familial hyperkalemic hypertension (FHHt, also called pseudohypoaldosteronism type II) which results from overaction of thiazide-sensitive sodium chloride cotransport (NCC). In addition, researchers have also found that dietary potassium deficiency activates NCC along the renal distal convoluted tubule (DCT). However, the underlying mechanism remains unclear about the relationship between potassium and WNK4.METHODS: In the present study, we conducted in vitro and in vivo experiments to confirm that KLHL3-dependent WNK4 degradation is affected by potassium through the neddylation and autophagy pathway. In vitro, the WNK4 and KLHL3 plasmids were cotransfected into HEK293 cell lines by lipofectamine 2000, and then incubated with different potassium concentrations (1mmol/L and 10mmol/L) for 24 h, and further treated with MLN4924 or the autophagy inhibitor or both of MLN4924 and the autophagy inhibitor for another 24 h respectively. In vivo, we created mice that were fed with low or high potassium diets and then were injected MLN4924 in the experimental groups. The expression of WNK4, pWNK4, KLHL3, NEDD8, LC3 ,and P62 was detected by western blotting in vitro and vivo experiments.
    RESULTS: We found that the abundance and phosphorylation of WNK4 increase when neddylation is inhibited both in vitro and vivo. Furthermore, the abundance of pWNK4, WNK4, NEDD8, and KLHL3 was increased in the low potassium (LK) group. Inhibiting autophagy can ameliorate the effect of potassium on the abundance and activity of WNK4 to some extent.
    CONCLUSION: These findings suggest a complex regulation of potassium in the degradation of WNK4. Low potassium can activate WNK4, which may be related to neddylation and autophagy, but the mechanism needs to be further studied.
    Keywords:  Autophagy; CUL3; KLHL3; Neddylation; Potassium; WNK4
    DOI:  https://doi.org/10.1186/s12882-023-03257-4
  42. Nat Commun. 2023 Jul 28. 14(1): 4543
    Modulating p38 MAPK signaling by proteostasis mechanisms supports tissue integrity during growth and aging.
    Wang Yuan, Yi M Weaver, Svetlana Earnest, Clinton A Taylor, Melanie H Cobb, Benjamin P Weaver.
      The conserved p38 MAPK family is activated by phosphorylation during stress responses and inactivated by phosphatases. C. elegans PMK-1 p38 MAPK initiates innate immune responses and blocks development when hyperactivated. Here we show that PMK-1 signaling is enhanced during early aging by modulating the stoichiometry of non-phospho-PMK-1 to promote tissue integrity and longevity. Loss of pmk-1 function accelerates progressive declines in neuronal integrity and lysosome function compromising longevity which has both cell autonomous and cell non-autonomous contributions. CED-3 caspase cleavage limits phosphorylated PMK-1. Enhancing p38 signaling with caspase cleavage-resistant PMK-1 protects lysosomal and neuronal integrity extending a youthful phase. PMK-1 works through a complex transcriptional program to regulate lysosome formation. During early aging, the absolute phospho-p38 amount is maintained but the reservoir of non-phospho-p38 diminishes to enhance signaling without hyperactivation. Our findings show that modulating the stoichiometry of non-phospho-p38 dynamically supports tissue-homeostasis during aging without hyper-activation of stress response.
    DOI:  https://doi.org/10.1038/s41467-023-40317-7
  43. Nat Aging. 2023 Jul 24.
    Impaired BCAA catabolism in adipose tissues promotes age-associated metabolic derangement.
    Hye-Sook Han, Eunyong Ahn, Eun Seo Park, Tom Huh, Seri Choi, Yongmin Kwon, Byeong Hun Choi, Jueun Lee, Yoon Ha Choi, Yujin L Jeong, Gwang Bin Lee, Minji Kim, Je Kyung Seong, Hyun Mu Shin, Hang-Rae Kim, Myeong Hee Moon, Jong Kyoung Kim, Geum-Sook Hwang, Seung-Hoi Koo.
      Adipose tissues are central in controlling metabolic homeostasis and failure in their preservation is associated with age-related metabolic disorders. The exact role of mature adipocytes in this phenomenon remains elusive. Here we describe the role of adipose branched-chain amino acid (BCAA) catabolism in this process. We found that adipocyte-specific Crtc2 knockout protected mice from age-associated metabolic decline. Multiomics analysis revealed that BCAA catabolism was impaired in aged visceral adipose tissues, leading to the activation of mechanistic target of rapamycin complex (mTORC1) signaling and the resultant cellular senescence, which was restored by Crtc2 knockout in adipocytes. Using single-cell RNA sequencing analysis, we found that age-associated decline in adipogenic potential of visceral adipose tissues was reinstated by Crtc2 knockout, via the reduction of BCAA-mTORC1 senescence-associated secretory phenotype axis. Collectively, we propose that perturbation of BCAA catabolism by CRTC2 is critical in instigating age-associated remodeling of adipose tissue and the resultant metabolic decline in vivo.
    DOI:  https://doi.org/10.1038/s43587-023-00460-8
  44. Microb Pathog. 2023 Jul 25. pii: S0882-4010(23)00303-0. [Epub ahead of print] 106270
    Streptococcus uberis induced expressions of pro-inflammatory IL-6, TNF-α, and IFN-γ in bovine mammary epithelial cells associated with inhibited autophagy and autophagy flux formation.
    Sohrab Khan, Jingyue Yang, Eduardo R Cobo, Yue Wang, Maolin Xu, Tian Wang, Yuxiang Shi, Gang Liu, Bo Han.
      Autophagy is a highly conserved cellular defensive mechanism that can eliminate bacterial pathogens such as Streptococcus uberis, that causes mastitis in cows. However, S. uberis induced autophagy is still unclear. In this study, we tested if certain inflammatory cytokines such as IL-6, TNF-α, and IFN-γ, critical in mastitis due to S. uberis infection, regulate autophagy activation in bovine mammary epithelial cells (bMECs). Using Western blot and laser scanning confocal microscope in bMECs challenged by S. uberis, showed that the expression of IL-6, TNF-α, IFN-γ oscillated with the expressions of autophagic Atg5, ULK1, PTEN, P62, and LC3ӀӀ/LC3Ӏ. S. uberis infection induced autophagosomes and LC3 puncta in bMECs with upregulation of Atg5, ULK1, PTEN, LC3ӀӀ/LC3Ӏ, and downregulation of P62. The levels of IL-6, TNF-α, and IFN-γ increased during autophagy flux formation to decrease during autophagy induction. Autophagy inhibition increased the expression of IL-6, TNF-α, and IFN-γ and increased S. uberis burden. This study indicates autophagy is induced during S. uberis infection and IL-6, TNF-α, and IFN-γ contribute to autophagy and autophagy flux formation.
    Keywords:  Autophagy; Bovine mastitis; Inflammatory cytokines; Streptococcus uberis; bMECs
    DOI:  https://doi.org/10.1016/j.micpath.2023.106270
  45. J Biol Chem. 2023 Jul 24. pii: S0021-9258(23)02115-4. [Epub ahead of print] 105087
    Hyper-ubiquitylation of DNA helicase RECQL4 by E3 ligase MITOL prevents mitochondrial entry and potentiates mitophagy.
    Mansoor Hussain, Aftab Mohammed, Shabnam Saifi, Swati Priya, Sagar Sengupta.
      Mutations in the DNA helicase RECQL4 lead to Rothmund-Thomson Syndrome (RTS), a disorder characterized by mitochondrial dysfunctions, premature aging, and genomic instability. However, the mechanisms by which these mutations lead to pathology are unclear. Here we report that RECQL4 is ubiquitylated by a mitochondrial E3 ligase, MITOL, at two lysine residues (K1101, K1154) via K6 linkage. This ubiquitylation hampers the interaction of RECQL4 with mitochondrial importer Tom20, thereby restricting its own entry into mitochondria. We show the RECQL4 2K mutant (where both K1101 and K1154 are mutated) has increased entry into mitochondria and demonstrates enhanced mtDNA replication. We observed that the three tested RTS patient mutants were unable to enter the mitochondria and showed decreased mtDNA replication. Furthermore, we found that RECQL4 in RTS patient mutants are hyper-ubiquitylated by MITOL and form insoluble aggregate-like structures on the outer mitochondrial surface. However, depletion of MITOL allows RECQL4 expressed in these RTS mutants to enter mitochondria and rescue mtDNA replication. Finally, we show increased accumulation of hyper-ubiquitylated RECQL4 outside the mitochondria leads to the cells being potentiated to increased mitophagy. Hence, we conclude regulating the turnover of RECQL4 by MITOL may have a therapeutic effect in RTS patients.
    Keywords:  E3 ligases; RecQ helicases; Rothmund Thomson Syndrome; autophagy; mitochondrial replication
    DOI:  https://doi.org/10.1016/j.jbc.2023.105087
  46. Nature. 2023 Jul 26.
    Evolutionarily divergent mTOR remodels translatome for tissue regeneration.
    Olena Zhulyn, Hannah D Rosenblatt, Leila Shokat, Shizhong Dai, Duygu Kuzuoglu-Öztürk, Zijian Zhang, Davide Ruggero, Kevan M Shokat, Maria Barna.
      An outstanding mystery in biology is why some species, such as the axolotl, can regenerate tissues whereas mammals cannot1. Here, we demonstrate that rapid activation of protein synthesis is a unique feature of the injury response critical for limb regeneration in the axolotl (Ambystoma mexicanum). By applying polysome sequencing, we identify hundreds of transcripts, including antioxidants and ribosome components that are selectively activated at the level of translation from pre-existing messenger RNAs in response to injury. By contrast, protein synthesis is not activated in response to non-regenerative digit amputation in the mouse. We identify the mTORC1 pathway as a key upstream signal that mediates tissue regeneration and translational control in the axolotl. We discover unique expansions in mTOR protein sequence among urodele amphibians. By engineering an axolotl mTOR (axmTOR) in human cells, we show that these changes create a hypersensitive kinase that allows axolotls to maintain this pathway in a highly labile state primed for rapid activation. This change renders axolotl mTOR more sensitive to nutrient sensing, and inhibition of amino acid transport is sufficient to inhibit tissue regeneration. Together, these findings highlight the unanticipated impact of the translatome on orchestrating the early steps of wound healing in a highly regenerative species and provide a missing link in our understanding of vertebrate regenerative potential.
    DOI:  https://doi.org/10.1038/s41586-023-06365-1
  47. Genes Dis. 2023 Sep;10(5): 2151-2166
    PTEN-induced putative kinase 1 regulates mitochondrial quality control and is essential for the maturation of human induced pluripotent stem cell-derived cardiomyocytes.
    Huiwen Liu, Yanting Sun, Hao Xu, Bin Tan, Qin Yi, Jie Tian, Jing Zhu.
      Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have attracted attention in the field of regenerative medicine due to their potential ability to repair damaged hearts. However, the immature phenotype of these cells limits their clinical application. Cardiomyocyte maturation is accompanied by changes in mitochondrial quality. PTEN-induced putative kinase 1 (PINK1) has been linked to mitochondrial quality control. However, whether the changes in mitochondrial quality in hiPSC-CMs are associated with PINK1, and the impact of PINK1 on hiPSC-CMs development are not clear. In this study, we found that knockdown of PINK1 in hiPSC-CMs resulted in mitochondrial fragmentation and impaired mitochondrial functions such as mitophagy and mitochondrial biogenesis. PINK1 deletion also inhibited the maturation of hiPSC-CMs, reverting them to a naive structural and functional state. We found that restoring the mitochondrial structure did not completely rescue the mitochondrial dysfunction caused by PINK1 deletion, while activation of PINK1 kinase activity using kinetin promoted mitochondrial fusion, increased the mitochondrial membrane potential and ATP production, and maintained the development and maturation of hiPSC-CMs. In conclusion, PINK1 regulates the mitochondrial structure and function of hiPSC-CMs, and is essential for the maturation of hiPSC-CMs.
    Keywords:  Maturation; Mitochondrial quality; PINK1; hiPSC-CMs; hiPSCs
    DOI:  https://doi.org/10.1016/j.gendis.2022.08.023
  48. Am J Chin Med. 2023 Jul 25. 1-17
    The Effects of Cinobufagin on Hepatocellular Carcinoma Cells Enhanced by MRT68921, an Autophagy Inhibitor.
    Zhongwei Xu, Jun Bao, Xiaohan Jin, Heng Li, Kaiyuan Fan, Zhidong Wu, Min Yao, Yan Zhang, Gang Liu, Dan Wang, Xiaoping Yu, Jia Guo, Ruicheng Xu, Qian Gong, Fengmei Wang, Jin Wang.
      Cinobufagin, a cardiotonic steroid derived from toad venom extracts, exhibits significant anticancer properties by inhibiting Na[Formula: see text]/K[Formula: see text]-ATPase in cancer cells. It is frequently used in clinical settings to treat advanced-stage cancer patients, improving their quality of life and survival time. However, its long-term use can result in multidrug resistance to other chemotherapy drugs, and the exact mechanism underlying this effect remains unknown. Therefore, this study explores the molecular mechanism underlying the anticancer effects of cinobufagin in hepatocellular carcinomas (HCCs), specifically in HepG2 and Huh-7 cells. As determined using transcriptome analysis, cinobufagin-triggered protective autophagy suppressed cell apoptosis in liver cancer HepG2 and Huh-7 cells by inhibiting the phosphoinositide-3-Kinase (PI3K)-AKT serine/threonine kinase (AKT)-mammalian target of rapamycin (mTOR) pathway. Cinobufagin-inhibited cell proliferation, induced apoptosis, and generated cell autophagy by upregulating the expression of MAP1 light chain 3 protein II, Beclin1, and autophagy-related protein 12-5. In addition, the autophagy inhibitor MRT68921 improved the antiproliferative and proapoptotic effects of cinobufagin in the studied cell lines. Overall, this study suggests that combining cinobufagin with an autophagy inhibitor can effectively treat HCC, providing a potential strategy for cancer therapy.
    Keywords:  Autophagy; Cardiotonic Steroids; Cinobufagin; Hepatocellular Carcinoma; Transcriptome
    DOI:  https://doi.org/10.1142/S0192415X23500726
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