Abstract
Snail belongs to the superfamily of zinc-finger transcription factors and plays a crucial role in processes regulating cell fate, such as the formation of mesoderm and initiation of epithelial-mesenchymal transition. We have previously discovered that Snail modulates adiponectin expression in 3T3-L1 cells during adipogenesis. In the present study, we elucidated the functional role of Snail in adipocyte differentiation and its underlying molecular mechanism. Snail expression was dramatically decreased during adipogenesis in 3T3-L1 cells. Overexpression of Snail blocked adipocyte differentiation by suppressing the expression of peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT-enhancer-binding protein alpha, while knockdown of Snail expression stimulated adipogenesis in 3T3-L1 cells. Chromatin immunoprecipitation assay and luciferase assay showed that Snail inhibits the transcriptional activity of the PPARγ gene by directly binding to the E-box motifs in the PPARγ promoter. Wnt10b induced phosphorylation of glycogen synthase kinase 3 beta (GSK3β), leading to inhibition of adipogenesis in 3T3-L1 cells in accordance with increased expression of Snail, whereas adipogenic capacity was restored in Snail siRNA-transfected preadipocytes. LiCl (a GSK3β inhibitor)-treated cells also showed increased expression of Snail, with a reduced adipogenic potential. Snail-overexpressing 3T3-F442A cells did not differentiate into mature adipocytes in immunodeficient nude mice. Taken together, Snail is a novel regulator of adipocyte differentiation, which acts by direct suppression of PPARγ expression. Our data also indicate that the expression of Snail is mediated by the Wnt-GSK3β signaling pathway.