PINK1/Parkin promotes liver regeneration via Sigma-1 ubiquitination to inhibit ER-Mitochondrial calcium transfer

<b>Rationale:</b> Liver regeneration is regulated by both metabolic processes and immune responses. Nonetheless, there is limited comprehension of the mechanisms involved. PINK1/Parkin-mediated mitophagy has been well documented, the role and underlying alternative mechanism of PINK1/Parkin in regulating mitochondrial metabolism during liver regeneration remains unclear. <b>Methods:</b> Liver tissues from mice undergoing hepatectomy were utilized to evaluate the expression levels of PINK1/Parkin. Hepatocyte-specific PINK1 knockout and transgenic mouse models were generated to investigate the impact of PINK1 on regeneration. Mass spectrometry, co-immunoprecipitation, and ubiquitination assays were performed to explore the underlying molecular mechanisms. <b>Results:</b> We observed PINK1/Parkin expression was markedly upregulated in hepatic tissue following liver resection. PINK1 depletion in hepatocytes caused impaired liver regeneration. Moreover, mitochondrial calcium overload was found be responsible for restricted TCA by inhibiting succinate dehydrogenase activity in PINK1 deficient hepatocytes. Interestingly, PINK1 deficiency leads to succinate accumulation and release from hepatocytes, which impairs liver regeneration by restricting macrophage pro-repair phenotypes. This effect was further confirmed by enhanced regeneration in myeloid SUCNR1 knockout mice. Mechanistically, Sigma-1 is a molecular chaperone of the endoplasmic reticulum calcium channel IP3R, which helps maintain its normal functional conformation. Parkin was able to bind Sigma-1 through its UBL domain, facilitating its k48-linked ubiquitination, which promotes Sigma-1 degradation and subsequently suppressing calcium transfer from the ER to mitochondria at the mitochondrial-associated ER membrane. <b>Conclusions:</b> Collectively, PINK1/Parkin signaling regulates hepatocellular mitochondrial ATP and succinate production by modulating ER-mitochondria calcium transfer to promote liver regeneration, revealing a promising therapeutic target for liver regeneration.