Glycosylation is a novel TGFβ1-independent post-translational modification of Smad2

Smad2 is a crucial component of intracellular signaling by transforming growth factor-β (TGFβ). Here we describe that Smad2 is glycosylated, which is a novel for Smad2 post-translational modification. We showed that the Smad2 glycosylation was inhibited upon treatment of cells with 17β-estradiol, and was enhanced in cells in a dense culture as compared to cells in a sparse culture. The Smad2 glycosylation was not dependent on the C-terminal phosphorylation of Smad2, and was not affected by TGFβ1 treatment of the cells. Smad2 was glycosylated at multiple sites, and one of the predicted sites is Serine110. Thus, Smad2 is glycosylated, and this post-translational modification was modulated by 17β-estradiol but not by TGFβ1.