Ca2+ channels mediate protein tyrosine kinase activation by
endothelin-1.
Simonson, Michael S., Yuan Wang, and William H. Herman.
Department of Medicine, Division of Nephrology, School of Medicine,
Case Western Reserve University, Cleveland, Ohio 44106
APStracts 2:0211F, 1995.
To investigate the novel interaction between endothelin-1 (ET-1) and
cellular protein tyrosine kinases (PTK), we asked whether Ca2+ influx
links ET-1 receptors to PTK activation. In glomerular mesangial
cells, ET-1 stimulated a biphasic increase in PTK activity in
antiphosphotyrosine immunoprecipitates that temporally correlated
with increased tyrosine phosphorylation of cellular proteins. ET-1
increased tyrosine phosphorylation of proteins in the cytosol and in
a punctate distribution consistent with focal adhesions. Addition of
ionomycin to increase Ca2+ influx stimulated PTK activity, and
inhibition of extracellular Ca2+ influx blocked PTK activation by ET
-1. ET-1 increased autophosphorylation of pp60c-src, which was
mimicked by addition of ionomycin and inhibited by chelation of
extracellular Ca2+. In addition, a selective PTK inhibitor blocked
induction of c-fos mRNA by ionomycin, suggesting that Ca2+-stimulated
PTKs contribute to a signaling pathway regulating immediate early
gene expression. Taken together, these results demonstrate that ET-1
stimulates non-receptor PTK activity, including pp60c-src, by
activating Ca2+ channels and subsequent influx of extracellular Ca2+.
Received 18 July 1995; accepted in final form 22 November 1995
APS Manuscript Number F235-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 December 95