Tyrosine phosphorylation of the dense plaque protein paxillin is
regulated during smooth muscle contraction.
Wang, Zhonglin, Fredrick. M. Pavalko, and Susan J. Gunst.
Dept. of Physiology and Biophysics, Indiana Univ. School of
Medicine, Indianapolis, IN, 46202
APStracts 3:0164C, 1996.
Regulation of the attachment of actin filaments to the cell membrane
at membrane-associated dense plaque (MADP) sites could allow smooth
muscle cells to modulate their cytostructure in response to changes
in external stress. In this study, changes in the tyrosine
phosphorylation of the MADP protein, paxillin, were measured by
Western blot during the contraction and relaxation of tracheal smooth
muscle strips. Tyrosine phosphorylation of paxillin increased by 3-4
fold with a time course similar to force development during
contractile stimulation with ACh, 5-hydroxytryptamine and KCl, and
decreased during washout of contractile stimuli and during relaxation
induced by forskolin. Immunoprecipitation of muscle extracts with
multiple rounds of anti-phosphotyrosine antibody removed
approximately 20% of the total paxillin in resting muscles, and about
60% of paxillin in muscles maximally stimulated with ACh. These
results provide the first evidence associating the tyrosine
phosphorylation of paxillin with the active contraction of smooth
muscle, or with any functional response of a fully differentiated
tissue in vivo. The results are consistent with a role for MADP
proteins in the regulation of force development in smooth muscle.
Received 29 January 1996; accepted in final form 8 May 1996.
APS Manuscript Number C58-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 28 May 96