Autophagy最新文献

SNAI (snail family transcriptional repressor) is a master regulator of epithelial-mesenchymal transition (EMT), yet its protein abundance varies markedly across breast cancer subtypes and cellular states. We identify SNAI as a bona fide substrate of chaperone-mediated autophagy (CMA) and propose a localization gate model in which nucleocytoplasmic trafficking dictates CMA accessibility. Macroautophagy inhibition stabilizes SQSTM1/p62 but does not alter SNAI levels, whereas depletion of the CMA chaperone HSPA8/HSC70 or the lysosomal receptor LAMP2A increases SNAI protein levels and extends its half-life. A CMA-resistant SNAI mutant fails to bind HSPA8-LAMP2A, is stabilized, and enhances EMT outputs, including migration, invasion, and lung colonization. In triple-negative breast cancer cells, SNAI is predominantly nuclear at baseline and thus inaccessible to CMA. Serum starvation promotes nuclear export, enabling cytosolic exposure and CMA-dependent degradation, which is blocked by leptomycin B. These findings connect selective autophagy to compartmental shielding and suggest that promoting cytosolic exposure and/or enhancing CMA capacity may attenuate SNAI-driven EMT competence.

Mutations in PINK1 and PRKN/parkin are the leading recessive causes of Parkinson disease (PD). Together PINK1 and PRKN form a mitophagy pathway for clearing damaged mitochondria from the cell. It was unclear, however, whether diverse forms of mitochondrial damage activate the PINK1-PRKN pathway through a unified mechanism. Recently, we demonstrated that loss of mitochondrial membrane potential (MMP) leads to the stabilization and activation of PINK1 under a wide range of mitochondrial stressors, including mitochondrial protein misfolding. Mechanistically, we suggest that the MMP is required at a key step of PINK1 import into mitochondria, in which PINK1 is transferred between the translocases of the outer and inner mitochondrial membranes. Consistent with this model, retention of active PINK1 of the outer membrane requires the translocase of the outer mitochondrial membrane (TOMM) complex, whereas import of PINK1 from the outer to inner membrane requires the TIMM23 (translocase of inner mitochondrial membrane 23) complex. Notably, chronic disruption of the TIMM23 complex is sufficient to stabilize active PINK1 in the TOMM complex, phenocopying MMP loss. Together, our findings suggest PINK1 primarily senses catastrophic drops in a mitochondrion's MMP: a dead-end for the mitochondrion's continued biogenesis.

Since its discovery as a key component of the autophagosome membrane, the small ubiquitin-like protein ATG8 and its mammalian homologs (ATG8s) have garnered a lot of attention. Many researchers use it as a marker for autophagosome number, size and composition. A lot of research has focussed on its function in forming complexes required for autophagosome-lysosome fusion or generally, its interaction with other proteins via the ATG8-family interacting motif/AIM. Many additional functions have been discovered, for instance in non-canonical autophagy processes and in the nucleus. The list of known functions of ATG8 are ever expanding, and, most recently, evidence has emerged that, similar to ubiquitin, ATG8 can modify proteins by covalent attachment to a lysine residue (protein ATG8ylation). In this review, we aim to summarize the current literature on protein ATG8ylation and highlight the currently known substrates. We propose strategies to investigate this modification and provide an outlook for its possible cellular function.Abbreviations: ATG: autophagy related; DUBs: de-ubiquitinating enzymes; GABARAPL: GABA type A receptor associated protein like; GIR: GABARAP-interacting region; LIR: LC3-interacting region; MAP1LC3: microtubule associated protein 1 light chain 3; RMSD: root mean square; UBL: ubiquitin-like; UPS: ubiquitin-proteasome-system.

The endoplasmic reticulum (ER) must carefully regulate the levels of nonmembrane lipids such as diacylglycerol (DAG), phosphatidic acid (PA), and triacylglycerol (TAG) to maintain membrane integrity and prevent lipotoxic stress. While ATG2A is well known as a lipid transfer protein essential for autophagosome formation, its role at lipid droplet (LD) contact sites has remained unclear. In our recent work, we show that ATG2A functions beyond its typical role in autophagy as a key regulator of lipid storage, transferring DAG, TAG, and PA from the ER to LDs and recruiting the TAG synthesis enzyme DGAT2 to promote LD expansion. Without ATG2A, lipids accumulate in the ER, leading to smaller, more numerous nucleated LDs rather than proper growth. Notably, ATG2A-mediated DAG transfer recruits DGAT2 to LD surfaces, enabling local TAG synthesis that prevents nonmembrane lipid accumulation in the ER. This cooperative process reveals ATG2A's dual role in both autophagy and lipid storage, highlighting an unexpected link between autophagy machinery and lipid storage.

Idiopathic pulmonary fibrosis (IPF) is a fatal interstitial lung disease driven by persistent activation of pulmonary myofibroblasts, but the regulatory mechanisms sustaining this pathological state remain incompletely understood. Using single-cell RNA sequencing (scRNA-seq), we identified SFRP2 (secreted frizzled related protein 2) as a critical mediator of profibrotic myofibroblasts in IPF lungs. Functional studies revealed that SFRP2 acted in an autocrine manner to promote myofibroblast activation and extracellular matrix (ECM) production. Mechanistically, SFRP2 activated FZD5-mediated non-canonical WNT-Ca²⁺ signaling, leading to PPP3/calcineurin-dependent translocation of PINK1 from the outer to the inner mitochondrial membrane (IMM), where it was degraded, thereby inhibiting PINK1-mediated mitophagy. Furthermore, therapeutic intervention with AAV6-shSfrp2, SFRP2-neutralizing antibody, or the autophagy inducer rapamycin significantly ameliorated lung fibrosis in bleomycin (BLM)-induced mouse models. Our results define a novel autocrine SFRP2-mitophagy regulatory axis that perpetuates myofibroblast activation and represents a promising therapeutic target for pulmonary fibrosis.Abbreviations: AAV: adeno-associated virus; BLM: bleomycin; CQ: chloroquine; ECM: extracellular matrix; FZD5: frizzled class receptor 5; H&E: hematoxylin and eosin; IHC: immunohistochemical; IMM: inner mitochondrial membrane; IPF: idiopathic pulmonary fibrosis; Micro-CT: micro-computed tomography; mtROS: mitochondrial reactive oxygen species; PMLFs: primary mouse lung fibroblasts; qPCR: quantitative real-time PCR; scRNA-seq: single-cell RNA sequencing; SFRP2: secreted frizzled related protein 2; TEM: transmission electron microscopy; ∆Ψm: mitochondrial membrane potential.

Metabolic dysfunction-associated steatohepatitis (MASH) serves as a primary contributor to liver fibrosis, cirrhosis, and hepatocellular carcinoma, yet specific diagnostic markers and therapeutic targets remain unavailable. This study elucidates the molecular mechanism by which UBQLN1 (ubiquilin 1) promotes MASH-related liver fibrosis by regulating small extracellular vesicles (sEVs) secretion and the functionality of the lysosome-mitochondria axis, as well as its clinical significance. Analysis of a multicenter cohort (n = 150) demonstrated significantly elevated UBQLN1 levels in both serum and serum-derived sEV from MASH patients, exhibiting diagnostic accuracies of 0.89 and 0.95, respectively. Furthermore, increased UBQLN1 was observed in mouse models of MASH, hiPSCs-derived human liver organoids, and oleic acid and palmitic acid injured hepatocytes (lipotoxic hepatocytes). Mechanistically, lipotoxic stress induces O-GlcNAcylation at the T277 site of UBQLN1 via OGT (O-GlcNAc transferase), which competitively inhibits its phosphorylation, consequently reducing ubiquitin-mediated degradation. Hepatocyte UBQLN1 facilitates the secretion of sEVs by regulating LAMP1-mediated fusion of multivesicular bodies (MVBs) with lysosomes. Subsequently, sEVs containing UBQLN1 regulate the activation of hepatic stellate cells by degrading the V-ATPase subunit ATP6V1B2 through E54D-dependent ubiquitin ligase activity, thereby inhibiting lysosomal acidification and mitophagy. Moreover, hepatic-specific knockdown of Ubqln1 or hepatocyte-specific knockdown of Ogt significantly alleviates fibrosis and metabolic disorders in MASH mice. This study elucidates the critical role of the post-translational modification regulatory network of UBQLN1 in the progression of MASH and proposes its translational potential as an integrated therapeutic target, providing a theoretical basis for the development of sEV-based intervention strategies.Abbreviations: ATP6V1B2 ATPase H+ transporting V1 subunit B2; Co-IP: co-immunoprecipitation; CCL4: carbon tetrachloride; ELISA: enzyme linked immunosorbent assay; GOT1/AST: glutamic-oxaloacetic transaminase; GPT/ALT: glutamic-pyruvic transaminase; hiPSCs: human induced pluripotent stem cells; HFD: high-fat diet; HFHC: high-fat and high-cholesterol diet; HSCs: hepatic stellate cells; LAMP1: lysosomal associated membrane protein 1; LTH-sEV: lipotoxic hepatocyte-derived small extracellular vesicles; LSECs: liver sinusoidal endothelial cells; MAP1LC3B/LC3: microtubule associated protein 1 light chain 3 beta; MVBs: multivesicular bodies; MASH: metabolic dysfunction-associated steatohepatitis; N-sEV: normal hepatocyte-derived sEV; OGT: O-linked N-acetylglucosamine (GlcNAc) transferase; O-GlcNAc: O-linked-β-D-N-acetylglucosamine; PAOA: oleic acid and palmitic acid; sEV: small extracellular vesicle; UBQLN1: ubiquilin 1.

Lipid droplets (LDs) are dynamic organelles that store neutral lipids and maintain lipid homeostasis. Many viruses exploit LDs as replication platforms or lipid sources, but their role in supplying membrane lipids for viral assembly remains unclear. Newcastle disease virus (NDV), an enveloped RNA virus with oncolytic potential, extensively remodels host metabolism, yet its impact on LD lipid mobilization is unknown. Here, we show that NDV reprograms host lipid metabolism via SQSTM1/p62-dependent lipophagy, selectively degrading triglycerides (TAGs) enriched in unsaturated fatty acids (UFAs). Lipidomics revealed concurrent depletion of UFA-containing triglycerides (UFA-TAGs) and UFA-containing phosphatidylcholines (UFA-PCs) during infection. Inhibition of lipophagy blocked LD degradation, reduced viral replication, and suppressed UFA-PC formation. Isotope tracing demonstrated that lipophagy-derived UFAs are incorporated into phosphatidylcholines (PCs) via the Kennedy pathway, whereas β-oxidation was dispensable. UFA supplementation rescued viral replication under lipophagy blockade and promoted virus-like particle (VLP) release, indicating that UFA-PCs facilitate viral budding. These findings uncover a distinct NDV strategy linking lipophagy-driven UFA release to phospholipid synthesis and membrane remodeling, revealing a lipid-based metabolic vulnerability for antiviral and oncolytic interventions.Abbreviations: AP: autophagosome; ATG: autophagy related; ATP: adenosine triphosphate; CQ: chloroquine; EGFP: enhance green fluorescent protein; FFA: free fatty acid; HN: Hemagglutinin-Neuraminidase; LA: linoleic acid; LD: lipid droplet; LIPA: lipase A, lysosomal acid type; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; NDV: newcastle disease virus; NP: nucleoprotein; OA: oleic acid; PA: palmitic acid; PC: phosphatidylcholine; PLIN2/ADRP: perilipin 2; PNPLA2/ATGL: patatin like phospholipase domain containing 2; POA: palmitoleic acid; SFA: saturated fatty acid; TAG: triglyceride; UFA: unsaturated fatty acid; UFA-PC: UFA-containing phosphatidylcholine; VLP: virus-like particle.