Endothelin-1 Induces Serine Phosphorylation of the Adaptor Protein p66 Shc and Its Association with 14-3-3 Protein in Glomerular Mesangial Cells

Abstract

Endothelin-1 (ET-1) is a vasoconstrictor peptide known to be a potent mitogen for glomerular mesangial cells (GMC). In the current study, it is demonstrated that ET-1 treatment of GMC results in serine phosphorylation of the 66-kDa isoform of the adapter protein Shc (p66Shc). ET-1-induced serine phosphorylation of p66Shc requires activation of the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) signaling module and is efficiently inhibited by both a MAPK/ERK kinase (MEK)-selective inhibitor and adenovirus-mediated transfer of a dominant interfering MEK1 mutant. Furthermore, adenovirus-mediated transfer of a constitutively active MEK1 mutant was found to markedly increase p66 Shc serine phosphorylation. Adenoviruses encoding constitutively active mutants of MAPK kinases 3 and 6 (upstream kinases of p38MAPK) and 7 (upstream kinase of c-Jun NH2-terminal kinase) failed to induce serine phosphorylation of this adaptor protein. Serine phosphorylation of p66Shc resulted in its association with the serine binding motif-containing protein 14-3-3. ET-1-induced phosphorylation of a serine encompassed in the 14-3-3 binding motif of p66Shc was confirmed in experiments employing anti-phospho-14-3-3 binding motif antibodies. These studies are the first to demonstrate that G protein-coupled receptors stimulate serine phosphorylation of p66Shc and the first to report the formation of a signaling complex between p66Shc and 14-3-3.