bims-lypmec 2025-04-13 papers

Front Cell Dev Biol. 2025 ;13 1559125

Lysosome-associated CASM: from upstream triggers to downstream effector mechanisms.

Namrita Kaur, Sven R Carlsson, Alf Håkon Lystad.

Lysosomes are dynamic organelles critical for cellular degradation and signaling, safeguarded by a limiting membrane that prevents leakage of harmful contents into the cytoplasm. Upon lysosomal damage, cells deploy defensive mechanisms, including a key process called CASM (conjugation of ATG8 to single membranes), which lipidates ATG8 proteins onto the limiting membrane to support protective pathways. CASM operates through two pathways: VAIL, induced by lysosomal pH changes via V-ATPase and ATG16L1, and STIL, triggered by sphingomyelin exposure and mediated by TECPR1. This review examines CASM's role in lysosomal damage responses, exploring the mechanisms of damaging agents, distinctions between VAIL and STIL, and the downstream effects of decorating lysosomes with ATG8, including effector recruitment for membrane repair or removal.

Keywords: Atg8; CASM; STIL; VAIL; atg8ylation; autophagy; lysosome damage

DOI: https://doi.org/10.3389/fcell.2025.1559125

Mol Cell. 2025 Mar 27. pii: S1097-2765(25)00201-1. [Epub ahead of print]

STING mediates lysosomal quality control and recovery through its proton channel function and TFEB activation in lysosomal storage disorders.

Zhen Tang, Cong Xing, Antonina Araszkiewicz, Kun Yang, Wanwan Huai, Devon Jeltema, Nicole Dobbs, Yihe Zhang, Lu O Sun, Nan Yan.

Lysosomes are essential organelles for cellular homeostasis. Defective lysosomes are associated with diseases like lysosomal storage disorders (LSDs). How lysosomal defects are detected and lysosomal function restored remain incompletely understood. Here, we show that STING mediates a neuroinflammatory gene signature in three distinct LSD mouse models, Galctwi/twi, Ppt1-/-, and Cln7-/-. Transcriptomic analysis of Galctwi/twi mouse brain tissue revealed that STING also mediates the expression of lysosomal genes that are regulated by transcriptional factor EB (TFEB). Immunohistochemical and single-nucleus RNA-sequencing (snRNA-seq) analysis show that STING regulates lysosomal gene expression in microglia. Mechanistically, we show that STING activation leads to TFEB dephosphorylation, nuclear translocation, and expression of lysosomal genes. This process requires STING's proton channel function, the V-ATPase-ATG5-ATG8 cascade, and is independent of immune signaling. Furthermore, we show that the STING-TFEB axis facilitates lysosomal repair. Together, our data identify STING-TFEB as a lysosomal quality control mechanism that responds to lysosomal dysfunction.

Keywords: Krabbe disease; Niemann-Pick disease; STING; TFEB; innate immunity; lysosomal storage disorder; lysosome repair; neuroinflammation; non-canonical autophagy

DOI: https://doi.org/10.1016/j.molcel.2025.03.008

J Cell Biol. 2025 Jun 02. pii: e202411092. [Epub ahead of print]224(6):

The autophagy protein ATG-9 regulates lysosome function and integrity.

Kangfu Peng, Guoxiu Zhao, Hongyu Zhao, Nobuo N Noda, Hong Zhang.

The transmembrane autophagy protein ATG9 has multiple functions essential for autophagosome formation. Here, we uncovered a novel function of ATG-9 in regulating lysosome biogenesis and integrity in Caenorhabditis elegans. Through a genetic screen, we identified that mutations attenuating the lipid scrambling activity of ATG-9 suppress the autophagy defect in epg-5 mutants, in which non-degradative autolysosomes accumulate. The scramblase-attenuated ATG-9 mutants promote lysosome biogenesis and delivery of lysosome-localized hydrolases and also facilitate the maintenance of lysosome integrity. Through manipulation of phospholipid levels, we found that a reduction in phosphatidylethanolamine (PE) also suppresses the autophagy defects and lysosome damage associated with impaired lysosomal degradation. Our results reveal that modulation of phospholipid composition and distribution, e.g., by attenuating the scramblase activity of ATG-9 or reducing the PE level, regulates lysosome function and integrity.

DOI: https://doi.org/10.1083/jcb.202411092

Cell. 2025 Apr 04. pii: S0092-8674(25)00282-X. [Epub ahead of print]

Quiescent cell re-entry is limited by macroautophagy-induced lysosomal damage.

Andrew Murley, Ann Catherine Popovici, Xiwen Sophie Hu, Anina Lund, Kevin Wickham, Jenni Durieux, Larry Joe, Etai Koronyo, Hanlin Zhang, Naomi R Genuth, Andrew Dillin.

To maintain tissue homeostasis, many cells reside in a quiescent state until prompted to divide. The reactivation of quiescent cells is perturbed with aging and may underlie declining tissue homeostasis and resiliency. The unfolded protein response regulators IRE-1 and XBP-1 are required for the reactivation of quiescent cells in developmentally L1-arrested C. elegans. Utilizing a forward genetic screen in C. elegans, we discovered that macroautophagy targets protein aggregates to lysosomes in quiescent cells, leading to lysosome damage. Genetic inhibition of macroautophagy and stimulation of lysosomes via the overexpression of HLH-30 (TFEB/TFE3) synergistically reduces lysosome damage. Damaged lysosomes require IRE-1/XBP-1 for their repair following prolonged L1 arrest. Protein aggregates are also targeted to lysosomes by macroautophagy in quiescent cultured mammalian cells and are associated with lysosome damage. Thus, lysosome damage is a hallmark of quiescent cells, and limiting lysosome damage by restraining macroautophagy can stimulate their reactivation.

Keywords: aging; endoplasmic reticulum; lysosome; mTOR; macroautophagy; protein aggregates; quiescence

DOI: https://doi.org/10.1016/j.cell.2025.03.009

Nat Commun. 2025 Apr 09. 16(1): 3375

Peripheral positioning of lysosomes supports melanoma aggressiveness.

Emerging evidence suggests that the function and position of organelles are pivotal for tumor cell dissemination. Among them, lysosomes stand out as they integrate metabolic sensing with gene regulation and secretion of proteases. Yet, how their function is linked to their position and how this controls metastasis remains elusive. Here, we analyze lysosome subcellular distribution in patient-derived melanoma cells and patient biopsies and show that lysosome spreading scales with melanoma aggressiveness. Peripheral lysosomes promote matrix degradation and cell invasion which is directly linked to the lysosomal and cell transcriptional programs. Using chemo-genetical control of lysosome positioning, we demonstrate that perinuclear clustering impairs lysosome secretion, matrix degradation and invasion. Impairing lysosome spreading significantly reduces invasive outgrowth in two in vivo models, mouse and zebrafish. Our study provides a direct demonstration that lysosome positioning controls cell invasion, illustrating the importance of organelle adaptation in carcinogenesis and suggesting its potential utility for diagnosis of metastatic melanoma.

DOI: https://doi.org/10.1038/s41467-025-58528-5

Nat Cell Biol. 2025 Apr 10.

The bridge-like lipid transport protein VPS13C/PARK23 mediates ER-lysosome contacts following lysosome damage.

Xinbo Wang, Peng Xu, Amanda Bentley-DeSousa, William Hancock-Cerutti, Shujun Cai, Benjamin T Johnson, Francesca Tonelli, Lin Shao, Gabriel Talaia, Dario R Alessi, Shawn M Ferguson, Pietro De Camilli.

Based on genetic studies, lysosome dysfunction is thought to play a pathogenetic role in Parkinson's disease. Here we show that VPS13C, a bridge-like lipid-transport protein and a Parkinson's disease gene, is a sensor of lysosome stress or damage. Following lysosome membrane perturbation, VPS13C rapidly relocates from the cytosol to the surface of lysosomes where it tethers their membranes to the ER. This recruitment depends on Rab7 and requires a signal at the damaged lysosome surface that releases an inhibited state of VPS13C, which hinders access of its VAB domain to lysosome-bound Rab7. Although another Parkinson's disease protein, LRRK2, is also recruited to stressed or damaged lysosomes, its recruitment occurs at much later stages and by different mechanisms. Given the role of VPS13 proteins in bulk lipid transport, these findings suggest that lipid delivery to lysosomes by VPS13C is part of an early protective response to lysosome damage.

DOI: https://doi.org/10.1038/s41556-025-01653-6

Circ Res. 2025 Apr 07.

Metabolic Coordination Structures Contribute to Diabetic Myocardial Dysfunction.

BACKGROUND: Individuals with diabetes are susceptible to cardiac dysfunction and heart failure, potentially resulting in mortality. Metabolic disorders frequently occur in patients with diabetes, and diabetes usually leads to remodeling of heart structure and cardiac dysfunction. However, the contribution and underlying mechanisms of metabolic and structural coupling in diabetic cardiac dysfunction remain elusive.
METHODS: Two mouse models of type 2 diabetes (T2DM) were used to assess alterations in glucose/lipid metabolism and cardiac structure. The potential metabolic-structural coupling molecule ACBP (acyl-coenzyme A-binding protein) was screened from 4 published datasets of T2DM-associated heart disease. In vivo loss-of-function and gain-of-function approaches were used to investigate the role of ACBP in diabetic cardiac dysfunction. The underlying mechanisms of metabolic and structural coupling were investigated by stable-isotope tracing metabolomics, coimmunoprecipitation coupled with mass spectrometry, and chromatin immunoprecipitation sequencing.
RESULTS: Diabetic mouse hearts exhibit enhanced lipid metabolism and impaired ultrastructure with marked cardiac systolic and diastolic dysfunction. Analysis of 4 T2DM public datasets revealed that Acbp was a significant lipid metabolism gene whose expression was upregulated. Consistently, ACBP expression levels were markedly elevated in the hearts of patients with diabetes and diabetic mice. Moreover, we constructed cardiomyocyte-specific Acbp knockout mice that exhibited attenuation of T2DM-induced cardiac remodeling and cardiac dysfunction, including attenuation of cardiac hypertrophy, fibrosis, ultrastructural damage, and enhanced cardiomyocyte contractility and cardiac function. Conversely, cardiac-specific Acbp overexpression via adeno-associated virus type 9, which encodes Acbp under the cTnT (cardiac troponin T) promoter, recapitulated cardiac dysfunction. Mechanistically, cardiac-specific Acbp knockout enhances glucose utilization in diabetic cardiomyocytes, suggesting a potential compensatory mechanism for insufficient ATP levels, highlighting its metabolic role. In addition, combined with mass spectrometry analysis revealed that ACBP binds MyBPC3 (myosin-binding protein C3) in T2DM individuals, which potentially prevents MyBPC3 from assisting the formation of cross-bridge structures between myosin and actin, thereby impairing myocardial contraction. Importantly, chromatin immunoprecipitation sequencing revealed that peroxisome proliferator-activated receptor γ regulates the transcriptional activity of Acbp.
CONCLUSIONS: Our findings demonstrated that ACBP mediates the bidirectional regulation of cardiomyocyte metabolic and structural associations and identified a promising therapeutic target for ameliorating cardiac dysfunction in patients with T2DM.

Keywords: cardiomyopathies; heart diseases; lipid metabolism; myocytes, cardiac; myosins

DOI: https://doi.org/10.1161/CIRCRESAHA.124.326044

Am J Physiol Heart Circ Physiol. 2025 Apr 07.

Cardiac Energy Metabolism in Diabetes: Emerging Therapeutic Targets and Clinical Implications.

Archee Panwar, Sufyan Malik, Muhtasim Adib, Gary D Lopaschuk.

Patients with diabetes are at an increased risk for developing diabetic cardiomyopathy and other cardiovascular complications. Alterations in cardiac energy metabolism in diabetic patients, including an increase in mitochondrial fatty acid oxidation and a decrease in glucose oxidation are important contributing factors to this increase in cardiovascular disease. A switch from glucose oxidation to fatty acid oxidation not only decreases cardiac efficiency due to increased oxygen consumption, but it can also increase reactive oxygen species production, increase lipotoxicity, and redirect glucose into other metabolic pathways that, combined, can lead to heart dysfunction. Currently, there is a lack of therapeutics available to treat diabetes-induced heart failure that specifically target cardiac energy metabolism. However, it is becoming apparent that part of the benefit of existing agents such as GLP-1 receptor agonists and sodium-glucose co-transporter 2 inhibitors may be related to their effects on cardiac energy metabolism. In addition, direct approaches aimed at inhibiting cardiac fatty acid oxidation or increasing glucose oxidation hold future promise as potential therapeutic approaches to treat diabetes-induced cardiovascular disease.

Keywords: diabetic cardiomyopathy; fatty acid ß-oxidation; glucose oxidation; mitochondria

DOI: https://doi.org/10.1152/ajpheart.00615.2024

Cardiovasc Toxicol. 2025 Apr 07.

MiR214-3p Ameliorates Diabetic Cardiomyopathy by Inhibiting Ferroptosis.

Peng Chen, Xiaohui Huang, Weixing Wen, Yue Cao, Weiwen Li, Guolin Huang, Yuli Huang, Yunzhao Hu, Tianyi Ma.

Ferroptosis is involved in the pathogenesis of diabetic cardiomyopathy (DCM). It has been shown that miR214-3p regulates ferroptosis, but no studies have shown a relationship between miR214-3p and DCM. This study induced glucolipotoxicity cardiomyocytes by treating HL-1 with high glucose and palmitic acid. Under these conditions, intracellular proteins TfR1 and FTH1, involved in Fe2+ transport and storage, were significantly elevated, and intracellular Fe2+ deposition was increased. The expression of GPX4, a key antioxidant molecule in ferroptosis, was reduced considerably, and the expression of lipid peroxidation-related proteins ACSL4 and COX2 was significantly elevated, with increased intracellular lipid peroxidation. Glucolipotoxicity cardiomyocytes overexpressing miR214-3p showed reduced expression levels of intracellular iron metabolism-related proteins, decreased Fe2+ deposition, elevated GPX4 expression, markedly down-regulated expression of ACSL4 and COX2, and reduced intracellular lipid peroxidation. In contrast, glucolipotoxicity cardiomyocytes with knockdown of miR214-3p showed more severe Fe2+ deposition and lipid peroxidation. In vivo, DCM mice showed significant cardiac function reduction and myocardial fibrosis. Consistent with the in vitro experiments, the expression level of GPX4 in myocardial tissues of DCM mice was reduced, and the expression of FTH1, ACSL4, and COX2 was significantly elevated. In contrast, DCM mice treated with miR214-3p showed improved cardiac function and alleviated myocardial fibrosis, with up-regulated GPX4 protein expression levels and significantly suppressed FTH1, ACSL4, and COX2 expression. These findings revealed that miR214-3p inhibits ferroptosis to improve DCM.

Keywords: Diabetic cardiomyopathy; Ferroptosis; GPX4; Lipid peroxidation; MiR214-3p

DOI: https://doi.org/10.1007/s12012-025-09992-4