-
Neuron Aug 2023Autophagy disorders prominently affect the brain, entailing neurodevelopmental and neurodegenerative phenotypes in adolescence or aging, respectively. Synaptic and...
Autophagy disorders prominently affect the brain, entailing neurodevelopmental and neurodegenerative phenotypes in adolescence or aging, respectively. Synaptic and behavioral deficits are largely recapitulated in mouse models with ablation of autophagy genes in brain cells. Yet, the nature and temporal dynamics of brain autophagic substrates remain insufficiently characterized. Here, we immunopurified LC3-positive autophagic vesicles (LC3-pAVs) from the mouse brain and proteomically profiled their content. Moreover, we characterized the LC3-pAV content that accumulates after macroautophagy impairment, validating a brain autophagic degradome. We reveal selective pathways for aggrephagy, mitophagy, and ER-phagy via selective autophagy receptors, and the turnover of numerous synaptic substrates, under basal conditions. To gain insight into the temporal dynamics of autophagic protein turnover, we quantitatively compared adolescent, adult, and aged brains, revealing critical periods of enhanced mitophagy or degradation of synaptic substrates. Overall, this resource unbiasedly characterizes the contribution of autophagy to proteostasis in the maturing, adult, and aged brain.
Topics: Animals; Mice; Autophagy; Mitophagy; Macroautophagy; Aging; Brain
PubMed: 37279748
DOI: 10.1016/j.neuron.2023.05.011 -
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 -
Autophagy May 2020Macroautophagy (autophagy) is a key catabolic pathway for the maintenance of proteostasis through constant digestion of selective cargoes. The selectivity of autophagy...
Macroautophagy (autophagy) is a key catabolic pathway for the maintenance of proteostasis through constant digestion of selective cargoes. The selectivity of autophagy is mediated by autophagy receptors that recognize and recruit cargoes to autophagosomes. SQSTM1/p62 is a prototype autophagy receptor, which is commonly found in protein aggregates associated with major neurodegenerative diseases. While accumulation of SQSTM1 implicates a disturbance of selective autophagy pathway, the pathogenic mechanism that contributes to impaired autophagy degradation remains poorly characterized. Herein we show that amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD)-linked mutations of and disrupt selective autophagy and cause neurotoxicity. Our data demonstrates that proteotoxic stress activates serine/threonine kinase TBK1, which coordinates with autophagy kinase ULK1 to promote concerted phosphorylation of autophagy receptor SQSTM1 at the UBA domain and activation of selective autophagy. In contrast, ALS-FTLD-linked mutations of or reduce SQSTM1 phosphorylation and compromise ubiquitinated cargo binding and clearance. Moreover, disease mutation SQSTM1 abolishes phosphorylation of Ser351 and impairs KEAP1-SQSTM1 interaction, thus diminishing NFE2L2/Nrf2-targeted gene expression and increasing TARDBP/TDP-43 associated stress granule formation under oxidative stress. Furthermore, expression of SQSTM1 in neurons impairs dendrite morphology and KEAP1-NFE2L2 signaling. Therefore, our results reveal a mechanism whereby pathogenic SQSTM1 mutants inhibit selective autophagy and disrupt NFE2L2 anti-oxidative stress response underlying the neurotoxicity in ALS-FTLD. ALS: amyotrophic lateral sclerosis; FTLD: frontotemporal lobar degeneration; G3BP1: GTPase-activating protein (SH3 domain) binding protein 1; GSTM1: glutathione S-transferase, mu 1; HMOX/HO-1: Heme oxygenase 1; IP: immunoprecipitation; KEAP1: kelch-like ECH associated protein 1; KI: kinase inactive; KIR: KEAP1 interaction region; KO: knockout; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MBP: maltose binding protein; NBR1: NBR1, autophagy cargo receptor; NFE2L2/Nrf2: nuclear factor, erythroid derived 2, like 2; NQO1: NAD(P)H quinone dehydrogenase 1; SQSTM1/p62: sequestosome 1; SOD1: superoxide dismutase 1, soluble; S.S.: serum starvation; TARDBP/TDP-43: TAR DNA binding protein; TBK1: TANK binding kinase 1; UBA: iquitin ssociation; ULK1: unc-51 like autophagy activating kinase 1; WT: wild type.
Topics: Amyotrophic Lateral Sclerosis; Autophagy; Humans; Macroautophagy; Mutation; Oxidative Stress; Protein Serine-Threonine Kinases; Sequestosome-1 Protein; Signal Transduction
PubMed: 31362587
DOI: 10.1080/15548627.2019.1644076 -
Autophagy Dec 2021Dysfunction of macroautophagy/autophagy in macrophages contributes to atherosclerosis. Impaired autophagy-lysosomal degradation system leads to lipid accumulation,...
Dysfunction of macroautophagy/autophagy in macrophages contributes to atherosclerosis. Impaired autophagy-lysosomal degradation system leads to lipid accumulation, facilitating atherosclerotic plaque. ATG14 is an essential regulator for the fusion of autophagosomes with lysosomes. Whether ATG14 plays a role in macrophage autophagy dysfunction in atherosclerosis is unknown. To investigate the effects of ATG14 on macrophage autophagy, human atherosclerotic plaque, mice and cultured mouse macrophages were evaluated. Overexpression of ATG14 by adenovirus was used to reveal its function in autophagy, inflammation and atherosclerotic plaque formation. Results showed that impaired autophagy function with reduction of ATG14 expression existed in macrophages of human and mouse atherosclerotic plaques. Ox-LDL impaired autophagosome-lysosome fusion with reduction of ATG14 expression in macrophages. Overexpression of ATG14 in macrophages enhanced fusion of autophagosomes with lysosomes and promoted lipid degradation, decreasing Ox-LDL-induced apoptosis and inflammatory response. Augmenting ATG14 expression reversed the autophagy dysfunction in macrophages of mice plaque, blunted SQSTM1/p62 accumulation, inhibited inflammation, and upregulated the population of Treg cells, resulting in alleviating atherosclerotic lesions. ABCC1: ATP-binding cassette, sub-family C (CFTR/MRP), member 1; ABCA1: ATP-binding cassette, sub-family A (ABC1), member 1; Ad-: adenovirus vector carrying the mouse gene; Ad-: adenovirus vector carrying the gene for bacterial β-galactosidase; : apolipoprotein E knockout; ATG14: autophagy-related 14; CD68: CD68 antigen; DAPI: 4',6-diamidino-2-phenylindole; Dil-ox-LDL: Dil-oxidized low density lipoprotein; ELISA: enzyme-linked immunosorbent assay; HFD: high-fat diet (an atherogenic diet); IL: interleukin; LAMP2: lysosomal-associated membrane protein 2; LDL-C: low density lipoprotrein cholesterol; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; ND: normal diet; Ox-LDL: oxidized low density lipoprotein; PBMC: peripheral blood mononuclear cells; SQSTM1/p62: sequestosome 1; SREBF1/SREBP1c: sterol regulatory element binding transcription factor 1; SREBF2/SREBP2: sterol regulatory element binding factor 2; STX17: syntaxin 17; TC: serum total cholesterol; TG: triglyceride; TNF: tumor necrosis factor; IFN: interferon; Treg cell: regulatory T cell.
Topics: Animals; Atherosclerosis; Autophagosomes; Autophagy; Inflammation; Leukocytes, Mononuclear; Lysosomes; Macroautophagy; Macrophages; Mice
PubMed: 33849389
DOI: 10.1080/15548627.2021.1909833 -
Autophagy Jan 2020Lysosomal membrane permeabilization or full rupture of lysosomes is a common and severe stress condition that is relevant for degenerative disease, infection and cancer.... (Review)
Review
Lysosomal membrane permeabilization or full rupture of lysosomes is a common and severe stress condition that is relevant for degenerative disease, infection and cancer. Cells respond with extensive ubiquitination of damaged lysosomes, which triggers selective macroautophagy/autophagy of the whole organelle, termed lysophagy. We screened an siRNA library targeting human E2-conjugating enzymes and identified UBE2QL1 as critical for efficient lysosome ubiquitination after chemically-induced lysosomal damage. UBE2QL1 translocates to lysosomes upon damage and associates with autophagy regulators. Loss of UBE2QL1-mediated ubiquitination reduces association of the autophagy receptor SQSTM1/p62 and the LC3-decorated phagophore, and prevents recruitment of the ubiquitin-targeted AAA-ATPase VCP/p97 that facilitates lysophagy. Even in unchallenged cells, UBE2QL1 depletion leads to MTOR dissociation and TFEB activation, and mutation of the homolog UBC-25 destabilizes lysosomes in , indicating that UBE2QL1 is critical for maintaining lysosome integrity in addition to lysophagy.
Topics: Animals; Autophagy; Humans; Intracellular Membranes; Lysosomes; Macroautophagy; Organelles; Ubiquitin-Conjugating Enzymes
PubMed: 31679434
DOI: 10.1080/15548627.2019.1687217 -
Autophagy Apr 2022Until recently, the ubiquitin-proteasome system (UPS) and macroautophagy/autophagy were considered to be two independent systems that target proteins for degradation by...
Until recently, the ubiquitin-proteasome system (UPS) and macroautophagy/autophagy were considered to be two independent systems that target proteins for degradation by proteasomes or via lysosomes, respectively. Here, we report that TRIM44 (tripartite motif containing 44) is a novel link that connects the UPS system with the autophagy degradation pathway. Suppressing the UPS degradation pathway leads to TRIM44 upregulation, which further promotes aggregated protein clearance through the binding of K48 ubiquitin chains on proteins. TRIM44 expression activates autophagy via promoting SQSTM1/p62 oligomerization, which rapidly increases the rate of aggregate protein removal. Overall, our data reveal that TRIM44 is a newly identified link between the UPS system and the autophagy pathway. Delineating the cross-talk between these two degradation pathways may reveal new mechanisms of targeting aggregate-prone diseases, such as cancer and neurodegenerative disease.: 3-MA: 3-methyladenine; ACTB: actin beta; ATG5: autophagy related 5; BB: B-box domain; BECN1: beclin1; BM: bone marrow; CC: coiled-coil domain; CFTR: cystic fibrosis transmembrane conductance regulator; CON: control; CQ: chloroquine; DOX: doxycycline; DSP: dithiobis(succinimidly propionate); ER: endoplasmic reticulum; FI: fluorescence intensity; FL: full length; HIF1A/HIF-1#x3B1;: hypoxia inducible factor 1 subunit alpha; HSC: hematopoietic stem cells; HTT: huntingtin; KD: knockdown; KD-CON: knockdown construct control; MM: multiple myeloma; MTOR: mechanistic target of rapamycin kinase; NP-40: nonidet P-40; NFE2L2/NRF2: nuclear factor, erythroid 2 like 2; OE: overexpression; OE-CON: overexpression construct control; PARP: poly (ADP-ribose) polymerase; SDS: sodium dodecyl sulfate; SQSTM1/p62: sequestosome 1; Tet-on: tetracycline; TRIM44: tripartite motif containing 44; UPS: ubiquitin-proteasome system; ZF: zinc-finger.
Topics: Autophagy; Humans; Intracellular Signaling Peptides and Proteins; Macroautophagy; Neurodegenerative Diseases; Proteasome Endopeptidase Complex; Sequestosome-1 Protein; Tripartite Motif Proteins; Ubiquitin
PubMed: 34382902
DOI: 10.1080/15548627.2021.1956105 -
Nature Communications Jan 2022Autophagy has been linked to a wide range of functions, including a degradative process that defends host cells against pathogens. Although the involvement of autophagy...
Autophagy has been linked to a wide range of functions, including a degradative process that defends host cells against pathogens. Although the involvement of autophagy in HBV infection has become apparent, it remains unknown whether selective autophagy plays a critical role in HBV restriction. Here, we report that a member of the galectin family, GAL9, directs the autophagic degradation of HBV HBc. BRET screening revealed that GAL9 interacts with HBc in living cells. Ectopic expression of GAL9 induces the formation of HBc-containing cytoplasmic puncta through interaction with another antiviral factor viperin, which co-localized with the autophagosome marker LC3. Mechanistically, GAL9 associates with HBc via viperin at the cytoplasmic puncta and enhanced the auto-ubiquitination of RNF13, resulting in p62 recruitment to form LC3-positive autophagosomes. Notably, both GAL9 and viperin are type I IFN-stimulated genes that act synergistically for the IFN-dependent proteolysis of HBc in HBV-infected hepatocytes. Collectively, these results reveal a previously undescribed antiviral mechanism against HBV in infected cells and a form of crosstalk between the innate immune system and selective autophagy in viral infection.
Topics: Antiviral Agents; Autophagosomes; Autophagy; Galectins; Gene Expression; HEK293 Cells; Hep G2 Cells; Hepatitis B; Hepatitis B virus; Humans; Macroautophagy; Proteolysis; Sequestosome-1 Protein; Viral Core Proteins; Virus Replication
PubMed: 35087074
DOI: 10.1038/s41467-022-28171-5 -
Nature Communications Mar 2023Autophagy is a critical process in the regulation of muscle mass, function and integrity. The molecular mechanisms regulating autophagy are complex and still partly...
Autophagy is a critical process in the regulation of muscle mass, function and integrity. The molecular mechanisms regulating autophagy are complex and still partly understood. Here, we identify and characterize a novel FoxO-dependent gene, d230025d16rik which we named Mytho (Macroautophagy and YouTH Optimizer), as a regulator of autophagy and skeletal muscle integrity in vivo. Mytho is significantly up-regulated in various mouse models of skeletal muscle atrophy. Short term depletion of MYTHO in mice attenuates muscle atrophy caused by fasting, denervation, cancer cachexia and sepsis. While MYTHO overexpression is sufficient to trigger muscle atrophy, MYTHO knockdown results in a progressive increase in muscle mass associated with a sustained activation of the mTORC1 signaling pathway. Prolonged MYTHO knockdown is associated with severe myopathic features, including impaired autophagy, muscle weakness, myofiber degeneration, and extensive ultrastructural defects, such as accumulation of autophagic vacuoles and tubular aggregates. Inhibition of the mTORC1 signaling pathway in mice using rapamycin treatment attenuates the myopathic phenotype triggered by MYTHO knockdown. Skeletal muscles from human patients diagnosed with myotonic dystrophy type 1 (DM1) display reduced Mytho expression, activation of the mTORC1 signaling pathway and impaired autophagy, raising the possibility that low Mytho expression might contribute to the progression of the disease. We conclude that MYTHO is a key regulator of muscle autophagy and integrity.
Topics: Adolescent; Humans; Animals; Mice; Muscle, Skeletal; Autophagy; Muscular Atrophy; Macroautophagy; Myotonic Dystrophy; Mechanistic Target of Rapamycin Complex 1
PubMed: 36864049
DOI: 10.1038/s41467-023-36817-1 -
Autophagy Jan 2024Omega-shaped domains of the endoplasmic reticulum, known as omegasomes, have been suggested to contribute to autophagosome biogenesis, although their exact function is...
Omega-shaped domains of the endoplasmic reticulum, known as omegasomes, have been suggested to contribute to autophagosome biogenesis, although their exact function is not known. Omegasomes are characterized by the presence of the double FYVE domain containing protein ZFYVE1/DFCP1, but it has remained a paradox that depletion of ZFYVE1 does not prevent bulk macroautophagy/autophagy. We recently showed that ZFYVE1 contains an N-terminal ATPase domain which dimerizes upon ATP binding. Mutations in the ATPase domain that inhibit ATP binding or hydrolysis do not prevent omegasome expansion and maturation. However, omegasome constriction is inhibited by these mutations, which results in an increased lifetime and thereby higher number of omegasomes. Interestingly, whereas knockout or mutations do not significantly affect bulk autophagy, selective autophagy of mitochondria, protein aggregates and micronuclei is inhibited. We propose that ATP binding and hydrolysis control the di- or multimerization state of ZFYVE1 which could provide the mechanochemical energy to drive large omegasome constriction and autophagosome completion.
Topics: Autophagy; Autophagosomes; Macroautophagy; Adenosine Triphosphatases; Adenosine Triphosphate
PubMed: 37722386
DOI: 10.1080/15548627.2023.2255967 -
The Journal of Cell Biology Nov 2022NBR1 was discovered as an autophagy receptor not long after the first described vertebrate autophagy receptor p62/SQSTM1. Since then, p62 has currently been mentioned in... (Review)
Review
NBR1 was discovered as an autophagy receptor not long after the first described vertebrate autophagy receptor p62/SQSTM1. Since then, p62 has currently been mentioned in >10,000 papers on PubMed, while NBR1 is mentioned in <350 papers. Nonetheless, evolutionary analysis reveals that NBR1, and likely also selective autophagy, was present already in the last eukaryotic common ancestor (LECA), while p62 appears first in the early Metazoan lineage. Furthermore, yeast-selective autophagy receptors Atg19 and Atg34 represent NBR1 homologs. NBR1 is the main autophagy receptor in plants that do not contain p62, while most animal taxa contain both NBR1 and p62. Mechanistic studies are starting to shed light on the collaboration between mammalian NBR1 and p62 in the autophagic degradation of protein aggregates (aggrephagy). Several domains of NBR1 are involved in cargo recognition, and the list of known substrates for NBR1-mediated selective autophagy is increasing. Lastly, roles of NBR1 in human diseases such as proteinopathies and cancer are emerging.
Topics: Animals; Humans; Autophagy; Carrier Proteins; Intracellular Signaling Peptides and Proteins; Macroautophagy; Mammals; Protein Aggregates; Sequestosome-1 Protein; Plants
PubMed: 36255390
DOI: 10.1083/jcb.202208092