ATAD3 is a limiting factor in mitochondrial biogenesis and adipogenesis of white adipocyte‐like 3T3‐L1 cells

Abstract ATAD3 is a vital ATPase of the inner mitochondrial membrane of pluri‐cellular eukaryotes, with largely unknown functions but early required for organism development as necessary for mitochondrial biogenesis. ATAD3 knock‐down in C. elegans inhibits at first the development of adipocyte‐like intestinal tissue so we used mouse adipocyte model 3T3‐L1 cells to analyze ATAD3 functions during adipogenesis and lipogenesis in a mammalian model. ATAD3 function was studied by stable and transient modulation of ATAD3 expression in adipogenesis‐ induced 3T3‐L1 cells using Knock‐Down and overexpression strategies, exploring different steps of adipocyte differentiation and lipogenesis. We show that (i) an increase in ATAD3 is preceding differentiation‐induced mitochondrial biogenesis; (ii) downregulation of ATAD3 inhibits adipogenesis, lipogenesis, and impedes overexpression of many mitochondrial proteins; (iii) ATAD3 re‐expression rescues the phenotype of ATAD3 KD, and (iv) differentiation and lipogenesis are accelerated by ATAD3 overexpression, but inhibited by expression of a dominant‐negative mutant. We further show that the ATAD3 KD phenotype is not due to altered insulin signal but involves a limitation of mitochondrial biogenesis linked to Drp1. These results demonstrate that ATAD3 is limiting for in vitro mitochondrial biogenesis and adipogenesis/lipogenesis and therefore that ATAD3 mutation/over‐ or under‐expression could be involved in adipogenic and lipogenic pathologies.