A requirement of growth factor receptor PTK and metalloproteinase activation in triggering endothelin‐1 (ET‐1)‐induced ERK1/2 and PKB phosphorylation In VSMC.

Abstract

A role of growth factor receptor transactivation and metalloproteinase in angiotensin II‐induced signaling events has been well established in vascular smooth muscle cells (VSMC). However, an involvement of receptor transactivation and metalloproteinase activation as upstream mediators of ET‐1‐induced signaling in VSMC has not been explored. In this study, we examined if similar to angiotensin II, ET‐1‐induced ERK1/2, PKB and GSK‐3 phosphorylation also requires transactivation of IGF‐1‐R, EGF‐R and PDGF‐R in VSMC. This possibility was tested by using a series of pharmacological inhibitors. We found that AG1024 and AG1478, inhibitors of IGF‐1‐R, and EGF‐R protein tyrosine kinases (PTKs) respectively, decreased ET‐1‐induced ERK1/2, PKB and GSK‐3 phosphorylation in a dose‐dependent fashion whereas, AG1295 an inhibitor of PDGF‐R‐PTK had no effect on ET‐1‐induced signaling events. Furthermore, PP‐2 a specific inhibitor of Src‐family PTK also blocked ET‐1‐induced phosphorylation of these protein kinases. Doxycycline and GM6001 two specific inhibitors of metalloproteinases, markedly attenuated ET‐1‐induced ERK1/2, PKB and GSK‐3 phosphorylation. These data suggest that, in VSMC, the phosphorylation of ERK1/2, PKB and GSK‐3 induced by ET‐1 is mediated through Src family PTKs, IGF‐1‐R and EGF‐R transactivation as well as metalloproteinase activation and not through PDGF‐R transactivation. (Supported by a grant from CIHR).