Regulation of Mitochondrial Remodeling in Adipose Thermogenesis

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PROJECT SUMMARY The global epidemic of obesity poses formidable challenges to human health associated with risks of chronic diseases such as type 2 diabetes and cardiovascular disease. Obesity is driven by systemic energy surplus with excessive fat deposition in white adipocytes (WAs). Brown adipocytes (BAs) that are specialized in dissipating energy through non-shivering thermogenesis and increasing energy expenditure represent a potential therapeutic target in obesity treatments. However, there is a critical knowledge gap in fully understanding the molecular mechanisms underlying BA function. Our long-term goal is therefore to explore the novel molecular regulation of BAs in order to facilitate the development of therapeutic strategies to combat obesity. By performing quantitative mitochondrial proteomics, we recently identified Family With Sequence Similarity 210, Member A (FAM210A), an uncharacterized protein, as a critical regulator of thermogenesis in brown adipose tissue (BAT). Emerging studies reported a potential role of FAM210A in regulating skeletal muscle growth and pathological cardiac remodeling, however the function of FAM210A in thermogenic BAs is completely unknown. Using newly developed Fam210a floxed mice, we provided strong preliminary data supporting an essential physiological role of FAM210A in BAT thermogenesis. We showed that 1) FAM210A is highly induced by cold and coupled with cold-induced mitochondrial cristae remodeling; 2) Adipocyte-specific knockout (KO) of Fam210a in mice leads to the whitening of BAT and cold intolerance; 3) Loss of Fam210a causes metabolic dysfunction of BAT; 4) Fam210a KO induces the depletion of mitochondria and disruption of cristae architecture. Based on this exciting discovery, the overall goal of this proposed study is to elucidate the cellular and molecular mechanisms by which FAM210A functions in BAs to regulate thermogenesis, and investigate the physiological role of adipose FAM210A in systemic metabolism. To achieve this goal, we propose three specific aims. In Aim 1, using mice and cells with inducible deletion of Fam210a in adipocytes, we will evaluate the regulatory role of FAM210A in mitochondrial metabolism, synthesis, and degradation in BAs in vivo and in vitro. Employing high-resolution three-dimensional imaging systems, we will dissect the function of FAM210A in controlling cold-induced cristae membrane remodeling. In Aim 2, we will define the molecular mechanisms through which FAM210A regulates mitochondrial homeostasis and cristae remodeling in BAs via the identification and characterization of interacting protein partners that enable FAM210A’s regulation of cristae-shaping protein. In Aim 3, we will utilize our unique loss- and gain-of-function mouse models to test whether FAM210A is required and sufficient to increase energy expenditure and systemic metabolism so as to ameliorate diet-induced obesity and metabolic dysfunction. Upon completion of the proposed studies, we expect to establish the functional role of FAM210A as a novel regulator of mitochondrial dynamics and BA thermogenesis, thus identifying a new potential therapeutic target for the obesity epidemic.