The autophagy receptor Ncoa4 controls PPARγ activity and thermogenesis in brown adipose tissue
Adipose tissue dysfunction leads to a variety of deleterious systemic consequences including ectopic lipid deposition and impaired insulin sensitivity. PPAR{gamma} is a major regulator of adipocyte differentiation and functionality and is thus a determinant of systemic metabolic health. We recently reported that deletion of adipocyte fatty acid synthase (AdFasnKO) impairs autophagy in association with a striking upregulation of genes controlled by PPAR{gamma}, including thermogenic uncoupling protein 1 (Ucp1). In this present study, screening for PPAR{gamma} coactivators regulated by autophagy revealed a protein denoted as Nuclear receptor coactivator 4 (Ncoa4), known to mediate ferritinophagy and interact with PPAR{gamma} and other nuclear receptors. Indeed, we found Ncoa4 is upregulated in the early phase of adipocyte differentiation and is required for adipogenesis. Ncoa4 is also elevated in FasnKO adipocytes and necessary for full upregulation of Ucp1 expression in vitro, even in response to norepinephrine. Consistent with these findings, adipose-selective knockout of Ncoa4 (AdNcoa4KO mice) impairs Ucp1 expression in brown adipose tissue and cold-induced thermogenesis. Adipose-selective double KO of Fasn plus Ncoa4 (AdFasnNcoa4DKO mice) prevents the upregulation of classic PPAR{gamma} target genes normally observed in the white adipose tissue of AdFasnKO mice, but not thermogenic Ucp1 expression. These findings reveal Ncoa4 is a novel determinant of adipocyte PPAR{gamma} activity and regulator of white and brown adipocyte biology and suggest that manipulation of autophagy flux modulates PPAR{gamma} activity and key adipocyte functions via Ncoa4 actions.