1572-P: USP30 Regulates Hepatic Mitophagy and Mitochondrial Function

Abstract

Mitochondria regulate several cellular and metabolic processes, necessitating cells to employ highly evolved quality control mechanisms to remove damaged mitochondria through a selective form of autophagy called mitophagy. Mitophagy is a mitochondrial quality control pathway, mediated in part by the ubiquitination of outer mitochondrial membrane (OMM) proteins. USP30 is an OMM deubiquitinase that regulates mitophagy by degrading OMM ubiquitin, thus inhibiting mitophagy. Hepatic mitophagy is reduced in obese fatty liver and is associated with mitochondrial dysfunction. Whether USP30 regulates mitophagy in hepatocytes in vivo and affects mitochondrial function is currently unknown. Therefore, we utilized the Cre-lox system to modulate USP30 expression in vivo to determine the effects on hepatic mitochondrial and metabolic function. Tail-vain injection of AAV8-TBG-Cre into USP30fl/fl and wild-type C57BL6 male mice was used to generate liver-specific USP30 knockout (LKO) and control mice (WT). Mice were fed regular chow and sacrificed at 16 weeks of age, 6 weeks after AAV dosing. Mitochondrial respiratory capacity was assessed using purified liver mitochondria and lipid metabolism was assessed biochemically in mice liver and plasma. USP30 liver-specific deletion in mice resulted in an impaired mitochondrial respiratory capacity as evidenced by increased mitochondrial leak respiration and reduced ADP-stimulated respiration in LKO mice compared to WT, such that the respiratory control ratio was significantly reduced in LKO mice. There were no differences in liver triglyceride levels, nor plasma triglycerides or fatty acids, while plasma cholesterol levels were 25% reduced in LKO mice (p=0.051). These data demonstrate that USP30 is an important regulator of mitochondrial respiratory capacity in hepatocytes in vivo, and that USP30 may normally inhibit excessive non-selective mitophagy in otherwise healthy mice. Disclosure O.G.Fagunloye: None. F.Bello: None. A.Vandevender: None. I.J.Sipula: None. M.J.Jurczak: None. Funding National Institute of Diabetes and Digestive and Kidney Diseases (R01DK114012)