Abstract
Adipose tissue is a central organiser of systemic lipid homeostasis and a pharmacological target in obesity, orchestrating cellular responses to environmental cues. Nutritionally regulated adipose and cardiac enriched protein (NRAC) is a small adipocyte-specific transmembrane protein with unknown function. Here, we show that Nrac directly interacts with scavenger receptor CD36 via its first transmembrane domain. Forming a complex with CD36 and caveolin-1 under low extracellular fatty acid (FA) concentrations, NRAC modulates CD36-dependent fatty acid uptake in adipocytes. Upon increase in extracellular FA levels, NRAC is ubiquitinated and internalised, leading to CD36's dissociation from caveolin-1 and clathrin-mediated endocytosis. This results in increased fatty acid uptake into fat cells, adipocyte hypertrophy, increased fat mass and elevated lipid clearance from the blood in chow-diet-fed mice. Finally, human NRAC expression and the intronic SNP rs12878589 are associated with body fat distribution and obesity. Together, these findings reveal a novel regulatory mechanism by which adipocytes sense and respond to extracellular fatty acid availability to fine-tune lipid uptake and storage at cellular and organismal level.
Keywords:
Adipose Tissue; CD36; Clathrin-mediated Endocytosis; Fatty Acid Uptake; Hypertrophy.