G3BP1 translocates into mitochondria to impair MCU complex function and promotes NASH progression [G3bp1-HKO and G3bp1-Flox mice with BSA or PA treatment]

Mitochondrial calcium signaling plays a critical role in mitochondrial homeostasis during non-alcoholic steatohepatitis (NASH) progression. Here, we report Ras‐GTPase activating protein SH3 domain‐binding protein 1 (G3BP1), a core protein of stress granule (SG), significantly upregulated in NAFLD/NASH patients, mouse models and palmitic acid-stimulated hepatocytes. Hepatocyte-specific G3BP1 deficiency attenuates NASH in two dietary mouse models. SG and the mitochondrial import protein TOM70 collaboratively mediate the translocation of G3BP1 to the mitochondria. G3BP1 interacts and stabilizes mitochondrial calcium uptake 1 (MICU1) via inhibiting YME1L1-mediated degradation of MICU1, and also impedes MCU complex activity and assembly, leading to mitochondrial calcium overload. Moreover, metabolic stress suppresses TRIM25-mediated K63-ubiquitination of G3BP1 and subsequent SG disassembly. Pharmacological inhibition of G3BP1 impairs the G3BP1-MICU1 interaction and prevents mitochondrial homeostasis imbalance and NASH progression. Collectively, we uncover the significant role of mitochondrial G3BP1 in mitochondrial homeostasis and NASH progression, which provides a potential target for therapeutic interventions.