Abstract 403: FAM210A Maintains Cardiac Mitochondrial Homeostasis Through Regulating Letm1-dependent Ca 2+ Efflux

Abstract

Mitochondria play fundamental roles in supporting healthy myocardium function. Disturbed cardiac mitochondrial homeostasis causes mitochondrial dysfunction associated with cardiomyopathy in humans and mice. Recent genome-wide association studies (GWAS) discovered that the mutations of FAM210A (family with sequence similarity 210 member A) are associated with sarcopenia and osteoporosis. Interestingly, Fam210a is most highly expressed in the heart and multiple omics analyses in mouse hearts reveal Fam210a as a hub gene in cardiac hypertrophy. However, the molecular function of FAM210A in the heart remains elusive. Here, we discover that FAM210A is critical for maintaining cardiac mitochondrial function and homeostasis. Cardiomyocyte (CM) specific knockout (KO) of Fam210a in adult mice leads to progressive heart failure with enlarged left ventricle chamber and ultimately causes mortality at ~70 days after Fam210a KO. The FAM210A deficient CMs exhibit myofilament disarray at ~9 weeks post Fam210a KO. Moreover, Fam210a KO results in a remarkably elevated mitochondrial ROS production, dramatically compromised mitochondrial membrane potential, and reduced expression of mitochondrial electron transport chain (ETC) complex genes. As a result, the mitochondrial respiratory activity is significantly reduced and the mitochondrial cristae are disrupted in Fam210a KO CMs. In contrast, at the early stage of ~5 weeks post tamoxifen-induced Fam210a KO, we observe increased mitochondrial ROS production, disturbed mitochondrial membrane potential, and reduced respiratory activity in CMs prior to heart failure. Transcriptomic and proteomic analyses from Fam210a KO hearts indicate that FAM210A deficiency causes chronic integrated stress response (ISR) in the heart. Mechanistically, Interactome analyses show that FAM210A binds to mitochondrial Ca 2+ /H + exchanger LETM1 (leucine zipper and EF-hand containing transmembrane protein 1) and regulates LETM1-mediated mitochondrial Ca 2+ efflux. Altogether, we discover a novel function of FAM210A in maintaining the cardiac mitochondrial homeostasis by regulating mitochondrial Ca 2+ efflux, and deficiency of FAM210A causes mitochondrial dysfunction and leads to heart failure.