bims-lypmec 2025-12-28 papers

Autophagy. 2025 Dec 24.

Microautophagy mediated by lysosomal membrane proteins: insights from LAMP2B-dependent microlipophagy.

Microautophagy involves the direct uptake of cytoplasmic materials by lysosomes, but its regulation, including substrate specificity, has remained largely unclear in mammalian cells. Microlipophagy, a form of lipid droplet microautophagy, has been suggested in mammalian cells, yet the molecular basis that links lysosomes to lipid droplets and supports their uptake has not been elucidated. In our recent study, we showed that the lysosomal membrane protein LAMP2B mediates this process via its cytoplasmic region, which can bind phosphatidic acid, a lipid present on lipid droplets. We also found that this pathway depends on the ESCRT machinery and proceeds independently of macroautophagy. In this commentary, we summarize these findings and describe how LAMP2B affects lipid droplet degradation in cells. We describe that LAMP2B overexpression protects mice from high-fat-diet-induced obesity and related disorders. We also outline a model of microautophagy and microautophagy-like processes in which LAMP2 isoforms use their cytoplasmic regions to recognize distinct cargos.

Keywords: Autophagy; LAMP2; LAMP2B; lipid droplet; microautophagy; microlipophagy

DOI: https://doi.org/10.1080/15548627.2025.2609920

Autophagy. 2025 Dec 26.

Proteotoxic stress triggers TFEB- and TFE3-mediated autophagy and lysosomal biogenesis via non-canonical MTORC1 inactivation.

Zhou Zhu, Jing Yang, Sandro Montefusco, Siyu Xia, Jinhuan Ou, Haibo Tong, Qingzhong Zeng, Fengmei Xu, Lingyun Dai, Jichao Sun, Chengchao Xu, Diego Luis Medina, Jigang Wang, Wei Zhang, Chuanbin Yang.

Proteotoxic stress, arising from conditions that cause misfolded protein accumulation, is closely linked to the pathogenesis of multiple diseases. Macroautophagy/autophagy activation is considered a compensatory mechanism to maintain protein homeostasis, but the underlying regulatory mechanisms remain incompletely understood. Here, we show that proteotoxic stress induced by proteasome inhibition, puromycin treatment, or polyglutamine-expanded HTT (huntingtin) expression promotes nuclear accumulation of TFEB and TFE3, key regulators of lysosomal biogenesis and autophagy. Mechanistically, TFEB activation under proteotoxic stress occurs independently of canonical MTORC1 inactivation mediated by TSC2 or ATF4. Instead, it involves non-canonical inhibition of MTORC1 via RRAG GTPases. Proteotoxic stress disrupts the RRAGC-TFEB interaction, preventing TFEB recruitment to lysosomes and subsequent MTORC1 phosphorylation. An activated RRAGC mutant rescues impaired lysosomal localization and nuclear accumulation of TFEB, while co-overexpression of FLCN and FNIP2, a GAP for RRAGC, partially restores stress-induced TFEB dephosphorylation. In addition, proteasome inhibition activates non-canonical autophagy. Deletion of ATG16L1 or ATG5, which blocks Atg8-familyh protein lipidation and sequesters the FLCN-FNIP2 complex, partially abolishes proteotoxic stress-induced TFEB dephosphorylation and nuclear accumulation. Together, these findings demonstrate that proteotoxic stress triggers both non-canonical autophagy and TFEB-mediated canonical autophagy, with Atg8-family protein lipidation contributing to TFEB activation. Our results provide novel insights into how proteotoxic stress engages non-canonical MTORC1 inhibition and TFEB activation, thereby enhancing understanding of cellular adaptation to proteotoxic stress.

Keywords: Autophagy; MTORC1; RRAG GTPase; TFEB; lysosomal biogenesis; proteosome

DOI: https://doi.org/10.1080/15548627.2025.2608973

Nat Commun. 2025 Dec 21.

Mechanosensitive dynamics of lysosomes along microtubules regulate leader cell emergence during collective cell migration.

Rituraj Marwaha, Diya Manoj, Simran Rawal, Purnati Khuntia, Sanak Banerjee, Praver Gupta, Basil Thurakkal, Manish Jaiswal, Tamal Das.

Collective cell migration during embryonic development, wound healing, and cancer metastasis requires the emergence of leader cells at the migration front. Despite their physiological relevance, the full mechanisms underlying the emergence of leader cells remain elusive. Here we report that leader cells display a peripheral accumulation of lysosomes in diverse model systems for wound healing, including cultured epithelial monolayer, mouse embryonic skin, and Drosophila embryos. This accumulation involves cellular contractile forces driving lysosomal transport along microtubules towards the leading edge. Indeed, we control leader cell emergence by manipulating lysosomal movement on microtubules. We further find that peripheral lysosomes associate with Rac1 molecules at the leading periphery, regulating local Rac1-activity, triggering actin polymerization and promoting lamellipodium formation. Taken together, we demonstrate that beyond their catabolic role, lysosomes act as an intracellular platform that links mechanical and biochemical signals to control the emergence of leader cells.

DOI: https://doi.org/10.1038/s41467-025-67645-0

Autophagy. 2025 Dec 23.

Comprehensive methodological evaluation of V-ATPase assembly in the context of cardiac lipid overload: implications for (endo)lysosomal function and autophagy.

Hongtao Tie, Mengqian Hou, Jun Zhang, Martijn F Hoes, Dietbert Neumann, Joost J F P Luiken, Shujin Wang.

The vacuolar-type H+-translocating ATPase (V-ATPase) plays a pivotal role in cellular homeostasis by acidifying endosomes and lysosomes, regulating key processes such as autophagy and membrane trafficking. While the importance of V-ATPase in these functions is well-established, the methodologies for studying its assembly and function remain varied and under-characterized. In this study, we systematically validated and compared methodologies for assessing V-ATPase assembly and endo/lysosomal acidification under physiological and high-fat conditions, both in vitro and in vivo. Various techniques, including fractionation, immunoprecipitation, immunofluorescence microscopy, and proximity ligation assays, were evaluated using cardiomyocyte cell lines, rat models of lipid overload, and two heart-specific V-ATPase-knockout mouse models (V-ATPase subunits ATP6V1G1 and ATP6V0D2). High palmitate (HP) and bafilomycin A1 (BafA) were used to manipulate v-ATPase function, while a colorimetric assay assessed proton-pumping activity. Results consistently showed that HP and BafA induced V-ATPase disassembly and inhibited proton-pumping activity, leading to impaired endo/lysosomal acidification and autophagy inhibition upon fusion of autophagosomes with lysosomes. Similar findings were observed in vivo, where a high-fat diet (HFD) reproduced the effects of HP on cardiac tissue. The methodologies were further validated in two heart-specific V-ATPase-knockout mouse models, demonstrating consistent outcomes across different experimental approaches. This study establishes a robust framework for evaluating V-ATPase assembly and function. The validated methodologies reveal that lipid overload inhibits autophagy and contributes to insulin resistance by inducing V-ATPase disassembly and subsequent lysosomal dysfunction. These findings offer insights into the molecular mechanisms underlying metabolic diseases and provide valuable tools for further research.

Keywords: Autophagy; V-type H±ATPase; bafilomycin A1; endosomes; heart; high palmitate; insulin resistance; lysosomes

DOI: https://doi.org/10.1080/15548627.2025.2608963

Arterioscler Thromb Vasc Biol. 2025 Dec 23.

Cytosolic Versus Lysosomal Lipolysis in Adipose Tissue: Opposing Roles in Cardiometabolic Disease.

Yu-Sheng Yeh, Jun Huang, Ziyang Liu, Carlos Cosme, Xiangyu Zhang, Babak Razani.

Adipose tissue lipid metabolism is a critical regulator of systemic energy balance, but its impact on cardiometabolic health is paradoxical. This review dissects the 2 primary lipolytic systems in adipocytes: the canonical cytosolic pathway driven by ATGL/PNPLA2 (adipose triglyceride lipase) and the lysosomal pathway governed by LAL/LIPA (lysosomal acid lipase). We present emerging evidence that these pathways exert opposing effects in the context of obesity. While excessive fatty acid efflux from dysregulated cytosolic lipolysis is a known driver of adiposopathic dyslipidemia, adipose inflammation, and direct cardiac lipotoxicity, which collectively impair cardiometabolic health, the activity of the lysosomal pathway is emerging as a protective counterbalance. Genetic and pharmacological studies demonstrate that inhibiting cytosolic ATGL is beneficial for metabolic health, whereas enhancing LAL-mediated lipolysis mitigates obesity-related dysfunction. This functional antagonism between cytosolic and lysosomal lipolysis presents a new paradigm in lipid metabolism, suggesting that therapeutic strategies must be pathway-specific. We conclude that selectively inhibiting pathogenic cytosolic lipid release while promoting beneficial lysosomal lipid processing offers a nuanced approach to treating metabolic disease.

Keywords: adiponectin; cardiovascular diseases; endothelium, vascular; hydrolysis; insulin resistance

DOI: https://doi.org/10.1161/ATVBAHA.125.323273