MGST1 regulates the assembly of MIB complex and promotes MAMs coupling to ameliorate pathological cardiac hypertrophy

AimDysregulation of mitochondria-associated endoplasmic reticulum membrane (MAM) coupling and the consequent impairment of endoplasmic reticulum-mitochondria signaling transduction are critical pathogenic links in pathological myocardial hypertrophy (PMH). The present study aims to systematically elucidate the molecular mechanisms underlying the role of MGST1, a key regulatory protein of MAM, in the initiation and progression of PMH, as well as its therapeutic potential.HypothesisWe hypothesize that microsomal glutathione S-transferase 1 (MGST1), as a key component of MAMs, maintains normal ER-mitochondrial cross-talk by modulation of the mitochondrial intermembrane bridging (MIB) complex. In PMH, downregulation of MGST1 destabilizes the MIB complex formation, leading to aberrant lipid transport and calcium transduction signals, and ultimately impairing mitochondrial function.MethodsMulti-omics analysis characterized MGST1 expression in TAC-induced PMH murine hearts and PE-stimulated hypertrophic cardiomyocytes (CMs). Clinical relevance was validated via single-cell RNA sequencing of heart failure patients. PMH murine models were established by TAC; myocardial-specific MGST1 knockout (MGST1cko) mice were generated, and cardiac MGST1 overexpression was achieved via AAV9-cTNT-MGST1. Genetically modified mice and controls were randomized to TAC/sham groups. At 4 weeks post-operation, left ventricular (LV) structure/function was assessed by echocardiography; LV tissues were analyzed via immunofluorescence and Western blotting for myocardial injury and MAM coupling. In vitro, PE-stimulated neonatal rat cardiomyocytes (NRCMs) were used to induce hypertrophy (quantified by immunofluorescence and qPCR). MAM coupling and mitochondrial function were evaluated via live-cell imaging, calcium transients, and flow cytometry. Co-immunoprecipitation verified MGST1-MIB interactions, with key mechanisms validated in HEK293T cells.ResultsMulti-omics analysis identified MGST1 as a critical MAM component with significant downregulation in PMH, and its expression negatively correlated with disease progression. Single-cell RNA sequencing confirmed progressive reduction of MGST1 during cardiomyocyte transition from normal to failing states. MGST1 protein levels also decreased in a time-dependent manner in both TAC-induced hypertrophic hearts and PE-stimulated NRCMs. MGST1cko mice exhibited exacerbated cardiac hypertrophy and impaired ventricular function post-TAC, while MGST1 overexpression exerted cardioprotective effects. In NRCMs, MGST1 knockdown aggravated PE-induced hypertrophy, disrupted MAM coupling, and induced mitochondrial dysfunction; conversely, MGST1 overexpression attenuated cellular hypertrophy, enhanced MAM connectivity, and improved mitochondrial performance. Mechanistically, MGST1 physically interacted with all three core MIB complex components (Samm50, Mic19, and Mic60), facilitating their assembly and mitochondrial cristae formation, thereby preserving mitochondrial ultrastructure.ConclusionsMGST1 maintains MAM coupling by promoting MIB complex assembly. Downregulation of MGST1 disrupts mitochondrial ultrastructure and ER-mitochondria communication, thereby exacerbating pathological cardiac hypertrophy. These findings indicate that the MGST1-MAM axis represents a potential therapeutic target for heart failure intervention Funding: This research was funded by grants from the National Natural Science Foundation of China (No. 82370334 and 82400312). This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.