Differential regulation of caveolin‐2 phosphorylation at serine 23 and 36 by caveolin‐1 and cell cycle in human endothelial cells.

Abstract

In the present study, we are focusing on regulation of serine phosphorylation of caveolin‐2 in endothelial cells. We show that phosphorylation of caveolin‐2 at serines 23 and 36 can be differentially regulated by caveolin‐1 and in endothelial cells synchronized in mitosis. To directly address the role of caveolin‐1 in regulating phosphorylation of endogenous caveolin‐2, we have used siRNA approach. The specific knockdown of caveolin‐1 in endothelial cells decreases caveolin‐2 phosphorylation at serine 23 but not serine 36. Furthermore, immunofluorescence microscopy studies determined that serine 23‐phosphorylated caveolin‐2 mostly localizes to plasma membrane caveolae. Thus, upregulation of serine 23 phosphorylation of caveolin‐2 depends on caveolin‐1‐driven targeting to plasma membrane caveolae. Interestingly, although, serine 36 phosphorylation does not seem to be regulated by caveolin‐1, it can be selectively upregulated in endothelial cells synchronized in mitosis. The latter data suggests a possible involvement of serine 36‐phosphorylated caveolin‐2 in modulating endothelial cell cycle, in particular mitosis.