Tyrosine phosphorylation and activation of pp60c-src and pp125fak
in bradykinin-stimulated fibroblasts.
Lee, Kyung-Mi, and Mitchel L. Villereal.
Department of Pharmacological and Physiological Sciences, The
University of Chicago, 947 E. 58th Street, Chicago, IL 60637, (Tel)
312-702-9334, (Fax) 312-702-5903
APStracts 2:0402C, 1995.
Bradykinin (BK) stimulates protein tyrosine phosphorylation in human
foreskin fibroblasts (Lee, K-M., Toscas, K., and Villereal, M.L.
(1993) J. Biol. Chem. 268, 9945-9948). The major tyrosine
phosphorylation occurs in proteins of MW 130 kDa and 70 kDa. In this
report, we demonstrate that focal adhesion-associated tyrosine
kinase, pp125FAK, is one component of the 130 kDa phosphotyrosine
band. The BK-stimulated pp125FAK tyrosine phosphorylation level is
well correlated with increased kinase activity, as assessed by in
vitro immune complex kinase assays. We have identified paxillin, a
protein which is localized in focal adhesions, as a component of the
70 kDa phosphotyrosine band. In addition to identifying the two
proteins responsible for the major phosphotyrosine bands, we also
report that pp60c-src is tyrosine phosphorylated and activated in
response to BK, as analyzed by immunoblotting and in vitro kinase
assays, respectively. These findings indicate, for the first time,
that the BK receptor is coupled to the important protooncogene c-src
and that the src pathway may mediate some of the events downstream
from BK binding.
Received 14 June 1995; accepted in final form 24 October 1995.
APS Manuscript Number C339-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 November 95