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Nature Communications Aug 2023Mitochondrial quality control is critical for cardiac homeostasis as these organelles are responsible for generating most of the energy needed to sustain contraction....
Mitochondrial quality control is critical for cardiac homeostasis as these organelles are responsible for generating most of the energy needed to sustain contraction. Dysfunctional mitochondria are normally degraded via intracellular degradation pathways that converge on the lysosome. Here, we identified an alternative mechanism to eliminate mitochondria when lysosomal function is compromised. We show that lysosomal inhibition leads to increased secretion of mitochondria in large extracellular vesicles (EVs). The EVs are produced in multivesicular bodies, and their release is independent of autophagy. Deletion of the small GTPase Rab7 in cells or adult mouse heart leads to increased secretion of EVs containing ubiquitinated cargos, including intact mitochondria. The secreted EVs are captured by macrophages without activating inflammation. Hearts from aged mice or Danon disease patients have increased levels of secreted EVs containing mitochondria indicating activation of vesicular release during cardiac pathophysiology. Overall, these findings establish that mitochondria are eliminated in large EVs through the endosomal pathway when lysosomal degradation is inhibited.
Topics: Animals; Mice; Lysosomes; Mitochondria; Biological Transport; Extracellular Vesicles; Multivesicular Bodies
PubMed: 37596294
DOI: 10.1038/s41467-023-40680-5 -
Ageing Research Reviews Aug 2023Old age is associated with a greater burden of disease, including neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease, as well as other... (Review)
Review
Old age is associated with a greater burden of disease, including neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease, as well as other chronic diseases. Coincidentally, popular lifestyle interventions, such as caloric restriction, intermittent fasting, and regular exercise, in addition to pharmacological interventions intended to protect against age-related diseases, induce transcription factor EB (TFEB) and autophagy. In this review, we summarize emerging discoveries that point to TFEB activity affecting the hallmarks of aging, including inhibiting DNA damage and epigenetic modifications, inducing autophagy and cell clearance to promote proteostasis, regulating mitochondrial quality control, linking nutrient-sensing to energy metabolism, regulating pro- and anti-inflammatory pathways, inhibiting senescence and promoting cell regenerative capacity. Furthermore, the therapeutic impact of TFEB activation on normal aging and tissue-specific disease development is assessed in the contexts of neurodegeneration and neuroplasticity, stem cell differentiation, immune responses, muscle energy adaptation, adipose tissue browning, hepatic functions, bone remodeling, and cancer. Safe and effective strategies of activating TFEB hold promise as a therapeutic strategy for multiple age-associated diseases and for extending lifespan.
Topics: Humans; Autophagy; Parkinson Disease; Alzheimer Disease; Aging; Lysosomes; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors
PubMed: 37321382
DOI: 10.1016/j.arr.2023.101985 -
Cell Reports Oct 2023Lipid droplets (LDs) play a crucial role in maintaining cellular lipid balance by storing and delivering lipids as needed. However, the intricate lipolytic pathways...
Lipid droplets (LDs) play a crucial role in maintaining cellular lipid balance by storing and delivering lipids as needed. However, the intricate lipolytic pathways involved in LD turnover remain poorly described, hindering our comprehension of lipid catabolism and related disorders. Here, we show a function of the small GTPase ARL8B in mediating LD turnover in lysosomes. ARL8B-GDP localizes to LDs, while ARL8-GTP predominantly favors lysosomes. GDP binding induces a conformation with an exposed N-terminal amphipathic helix, enabling ARL8B to bind to LDs. By associating with LDs and lysosomes, and with its property to form a heterotypic complex, ARL8B mediates LD-lysosome contacts and efficient lipid transfer between these organelles. In human macrophages, this ARL8B-dependent LD turnover mechanism appears as the major lipolytic pathway. Our finding opens exciting possibilities for understanding the molecular mechanisms underlying LD degradation and its potential implications for inflammatory disorders.
Topics: Humans; Lipid Droplets; Monomeric GTP-Binding Proteins; Signal Transduction; Lysosomes; Lipids; Lipid Metabolism; ADP-Ribosylation Factors
PubMed: 37777960
DOI: 10.1016/j.celrep.2023.113203 -
Neurobiology of Disease Sep 2023Lysosomes are acidic intracellular organelles with autophagic functions that are critical for protein degradation and mitochondrial homeostasis, while abnormalities in... (Review)
Review
Lysosomes are acidic intracellular organelles with autophagic functions that are critical for protein degradation and mitochondrial homeostasis, while abnormalities in lysosomal physiological functions are closely associated with neurological disorders. Transmembrane protein 175 (TMEM175), an ion channel in the lysosomal membrane that is essential for maintaining lysosomal acidity, has been proven to coordinate with V-ATPase to modulate the luminal pH of the lysosome to assist the digestion of abnormal proteins and organelles. However, there is considerable controversy about the characteristics of TMEM175. In this review, we introduce the research progress on the structural, modulatory, and functional properties of TMEM175, followed by evidence of its relevance for neurological disorders. Finally, we discuss the potential value of TMEM175 as a therapeutic target in the hope of providing new directions for the treatment of neurodegenerative diseases.
Topics: Humans; Ion Channels; Neurodegenerative Diseases; Lysosomes; Autophagy; Potassium Channels
PubMed: 37524211
DOI: 10.1016/j.nbd.2023.106244 -
Cell Reports Oct 2023Dysfunctional mitochondria are removed via multiple pathways, such as mitophagy, a selective autophagy process. Here, we identify an intracellular hybrid...
Dysfunctional mitochondria are removed via multiple pathways, such as mitophagy, a selective autophagy process. Here, we identify an intracellular hybrid mitochondria-lysosome organelle (termed the mitochondria-lysosome-related organelle [MLRO]), which regulates mitochondrial homeostasis independent of canonical mitophagy during hepatocyte dedifferentiation. The MLRO is an electron-dense organelle that has either a single or double membrane with both mitochondria and lysosome markers. Mechanistically, the MLRO is likely formed from the fusion of mitochondria-derived vesicles (MDVs) with lysosomes through a PARKIN-, ATG5-, and DRP1-independent process, which is negatively regulated by transcription factor EB (TFEB) and associated with mitochondrial protein degradation and hepatocyte dedifferentiation. The MLRO, which is galectin-3 positive, is reminiscent of damaged lysosome and could be cleared by overexpression of TFEB, resulting in attenuation of hepatocyte dedifferentiation. Together, results from this study suggest that the MLRO may act as an alternative mechanism for mitochondrial quality control independent of canonical autophagy/mitophagy involved in cell dedifferentiation.
Topics: Mitochondria; Organelles; Lysosomes; Autophagy; Mitophagy
PubMed: 37862166
DOI: 10.1016/j.celrep.2023.113291 -
Journal of Neuroinflammation Aug 2023Microglia are the resident innate immune cells in the brain with a major role in orchestrating immune responses. They also provide a frontline of host defense in the... (Review)
Review
Microglia are the resident innate immune cells in the brain with a major role in orchestrating immune responses. They also provide a frontline of host defense in the central nervous system (CNS) through their active phagocytic capability. Being a professional phagocyte, microglia participate in phagocytic and autophagic clearance of cellular waste and debris as well as toxic protein aggregates, which relies on optimal lysosomal acidification and function. Defective microglial lysosomal acidification leads to impaired phagocytic and autophagic functions which result in the perpetuation of neuroinflammation and progression of neurodegeneration. Reacidification of impaired lysosomes in microglia has been shown to reverse neurodegenerative pathology in Alzheimer's disease. In this review, we summarize key factors and mechanisms contributing to lysosomal acidification impairment and the associated phagocytic and autophagic dysfunction in microglia, and how these defects contribute to neuroinflammation and neurodegeneration. We further discuss techniques to monitor lysosomal pH and therapeutic agents that can reacidify impaired lysosomes in microglia under disease conditions. Finally, we propose future directions to investigate the role of microglial lysosomal acidification in lysosome-mitochondria crosstalk and in neuron-glia interaction for more comprehensive understanding of its broader CNS physiological and pathological implications.
Topics: Humans; Microglia; Neuroinflammatory Diseases; Alzheimer Disease; Lysosomes; Hydrogen-Ion Concentration
PubMed: 37543564
DOI: 10.1186/s12974-023-02866-y -
Science Advances Jul 2023Mutations in the E3 ubiquitin ligase parkin are the most common cause of early-onset Parkinson's disease (PD). Although parkin modulates mitochondrial and endolysosomal...
Mutations in the E3 ubiquitin ligase parkin are the most common cause of early-onset Parkinson's disease (PD). Although parkin modulates mitochondrial and endolysosomal homeostasis during cellular stress, whether parkin regulates mitochondrial and lysosomal cross-talk under physiologic conditions remains unresolved. Using transcriptomics, metabolomics and super-resolution microscopy, we identify amino acid metabolism as a disrupted pathway in iPSC-derived dopaminergic neurons from patients with parkin PD. Compared to isogenic controls, parkin mutant neurons exhibit decreased mitochondria-lysosome contacts via destabilization of active Rab7. Subcellular metabolomics in parkin mutant neurons reveals amino acid accumulation in lysosomes and their deficiency in mitochondria. Knockdown of the Rab7 GTPase-activating protein TBC1D15 restores mitochondria-lysosome tethering and ameliorates cellular and subcellular amino acid profiles in parkin mutant neurons. Our data thus uncover a function of parkin in promoting mitochondrial and lysosomal amino acid homeostasis through stabilization of mitochondria-lysosome contacts and suggest that modulation of interorganelle contacts may serve as a potential target for ameliorating amino acid dyshomeostasis in disease.
Topics: Humans; Parkinson Disease; Mitochondria; Ubiquitin-Protein Ligases; Dopaminergic Neurons; Lysosomes; Homeostasis; GTPase-Activating Proteins
PubMed: 37467322
DOI: 10.1126/sciadv.adh3347 -
Autophagy Sep 2023Macroautophagy/autophagy plays a protective role in sepsis-induced liver injury. As a member of class B scavenger receptors, CD36 plays important roles in various...
Macroautophagy/autophagy plays a protective role in sepsis-induced liver injury. As a member of class B scavenger receptors, CD36 plays important roles in various disorders, such as atherosclerosis and fatty liver disease. Here we found that the expression of CD36 in hepatocytes was increased in patients and a mouse model with sepsis, accompanied by impaired autophagy flux. Furthermore, hepatocyte knockout (-HKO) markedly improved liver injury and the impairment of autophagosome-lysosome fusion in lipopolysaccharide (LPS)-induced septic mice. (ubiquilin 1) overexpression (OE) in hepatocyte blocked the protective effect of -HKO on LPS-induced liver injury in mice. Mechanistically, with LPS stimulation, CD36 on the plasma membrane was depalmitoylated and distributed to the lysosome, where CD36 acted as a bridge molecule linking UBQLN1 to soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins and hence promoting the proteasomal degradation of SNARE proteins, resulting in fusion impairment. Overall, our data reveal that CD36 is essential for modulating the proteasomal degradation of autophagic SNARE proteins in a UBQLN1-dependent manner. Targeting CD36 in hepatocytes is effective for improving autophagic flux in sepsis and therefore represents a promising therapeutic strategy for clinical treatment of septic liver injury. AAV8: adeno-associated virus 8; AOSC: acute obstructive suppurative cholangitis; ATP1A1: ATPase, Na+/K+ transporting, alpha 1 polypeptide; CASP3: caspase 3; CASP8: caspase 8; CCL2: chemokine (C-C motif) ligand 2; -HKO: hepatocyte-specific knockout; Co-IP: co-immunoprecipitation; CQ: chloroquine; Cys: cysteine; GOT1: glutamic-oxaloacetic transaminase 1, soluble; GPT: glutamic-pyruvic transaminase, soluble; IL1B: interleukin 1 beta; IL6: interleukin 6; KO: knockout; LAMP1: lysosomal associated membrane protein 1; LDH, lactate dehydrogenase; LPS: lipopolysaccharide; LYPLA1: lysophospholipase 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; OE: overexpression; qPCR: quantitative polymerase chain reaction; SNAP29: synaptosome associated protein 29; SNARE: soluble N-ethylmaleimide-sensitive factor attachment protein receptor; SQSTM1/p62: sequestosome 1; STX17: syntaxin 17; TNF: tumor necrosis factor; TRIM: tripartite motif-containing; UBA: ubiquitin-associated; UBL: ubiquitin-like; UBQLN: ubiquilin; VAMP8: vesicle associated membrane protein 8; WT: wild-type.
Topics: Animals; Mice; Adaptor Proteins, Signal Transducing; Autophagy; Autophagy-Related Proteins; Chemical and Drug Induced Liver Injury, Chronic; Hepatocytes; Lipopolysaccharides; Lysosomes; Sepsis; SNARE Proteins; Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; Ubiquitins
PubMed: 37014234
DOI: 10.1080/15548627.2023.2196876 -
The Journal of Cell Biology Dec 2023Cells harness multiple pathways to maintain lysosome integrity, a central homeostatic process. Damaged lysosomes can be repaired or targeted for degradation by...
Cells harness multiple pathways to maintain lysosome integrity, a central homeostatic process. Damaged lysosomes can be repaired or targeted for degradation by lysophagy, a selective autophagy process involving ATG8/LC3. Here, we describe a parallel ATG8/LC3 response to lysosome damage, mechanistically distinct from lysophagy. Using a comprehensive series of biochemical, pharmacological, and genetic approaches, we show that lysosome damage induces non-canonical autophagy and Conjugation of ATG8s to Single Membranes (CASM). Following damage, ATG8s are rapidly and directly conjugated onto lysosome membranes, independently of ATG13/WIPI2, lipidating to PS (and PE), a molecular hallmark of CASM. Lysosome damage drives V-ATPase V0-V1 association, direct recruitment of ATG16L1 via its WD40-domain/K490A, and is sensitive to Salmonella SopF. Lysosome damage-induced CASM is associated with formation of dynamic, LC3A-positive tubules, and promotes robust LC3A engagement with ATG2, a lipid transfer protein central to lysosome repair. Together, our data identify direct ATG8 conjugation as a rapid response to lysosome damage, with important links to lipid transfer and dynamics.
Topics: Autophagy; Lysosomes; Macroautophagy; Microtubule-Associated Proteins; Salmonella; Autophagy-Related Protein 8 Family
PubMed: 37796195
DOI: 10.1083/jcb.202303078 -
Autophagy Jul 2023Macroautophagy/autophagy has been shown to exert a dual role in cancer i.e., promoting cell survival or cell death depending on the cellular context and the cancer...
Macroautophagy/autophagy has been shown to exert a dual role in cancer i.e., promoting cell survival or cell death depending on the cellular context and the cancer stage. Therefore, development of potent autophagy modulators, with a clear mechanistic understanding of their target action, has paramount importance in both mechanistic and clinical studies. In the process of exploring the mechanism of action of a previously identified cytotoxic small molecule (SM15) designed to target microtubules and the interaction domain of microtubules and the kinetochore component NDC80/HEC1, we discovered that the molecule acts as a potent autophagy inhibitor. By using several biochemical and cell biology assays we demonstrated that SM15 blocks basal autophagic flux by inhibiting the fusion of correctly formed autophagosomes with lysosomes. SM15-induced autophagic flux blockage promoted apoptosis-mediated cell death associated with ROS production. Interestingly, autophagic flux blockage, apoptosis induction and ROS production were rescued by genetic or pharmacological inhibition of OGT (O-linked N-acetylglucosamine (GlcNAc) transferase) or by expressing an O-GlcNAcylation-defective mutant of the SNARE fusion complex component SNAP29, pointing to SNAP29 as the molecular target of SM15 in autophagy. Accordingly, SM15 was found to enhance SNAP29 O-GlcNAcylation and, thereby, inhibit the formation of the SNARE fusion complex. In conclusion, these findings identify a new pathway in autophagy connecting O-GlcNAcylated SNAP29 to autophagic flux blockage and autophagosome accumulation, that, in turn, drives ROS production and apoptotic cell death. Consequently, modulation of SNAP29 activity may represent a new opportunity for therapeutic intervention in cancer and other autophagy-associated diseases.
Topics: Autophagosomes; Autophagy; Macroautophagy; Reactive Oxygen Species; Lysosomes; SNARE Proteins; Apoptosis
PubMed: 36704963
DOI: 10.1080/15548627.2023.2170962