Neuronal growth regulator 1 promotes adipocyte lipid trafficking via interaction with CD36

Abstract

Neuronal growth regulator 1 (NEGR1) is a glycosylphosphatidylinositol-anchored membrane protein associated with several human pathologies, including obesity, depression, and autism. Recently, significantly enlarged white adipose tissue, hepatic lipid accumulation, and decreased muscle capacity were reported in Negr1-deficient mice. However, the mechanism behind these phenotypes was not clear. In the present study, we found NEGR1 to interact with cluster of differentiation 36 (CD36), the major fatty acid translocase in the plasma membrane. Binding assays with a soluble form of NEGR1 and in situ proximal ligation assays indicated that NEGR1-CD36 interaction occurs at the outer leaflet of the cell membrane. Furthermore, we show that NEGR1 overexpression induced CD36 protein destabilization in vitro. Both mRNA and protein levels of CD36 were significantly elevated in the white adipose tissue and liver tissues of Negr1−/− mice. Accordingly, fatty acid uptake rate increased in NEGR1-deficient primary adipocytes. Finally, we demonstrated that Negr1−/− mouse embryonic fibroblasts showed elevated reactive oxygen species levels and decreased adenosine monophosphate-activated protein kinase activation compared with control mouse embryonic fibroblasts. Based on these results, we propose that NEGR1 regulates cellular fat content by controlling the expression of CD36.

Keywords

• obesity
• adipose tissue
• fatty acid/transport
• CD36
• lipid rafts
• proximal ligation assay