Activation of map kinase and translocation with hsp27 in bombesin
induced contraction of rectosigmoid smooth muscle.
Yamada, H., J. Strahler, M. J. Welsh, and K. N. Bitar.
Departments of Pediatrics and Anatomy and Cell Biology, University
of Michigan Medical Center, Ann Arbor, MI 48109
APStracts 2:0093G, 1995.
We have investigated whether Mitogen-Activated protein (MAP) kinase
cascade is essential for sustained contraction of smooth muscle cells
of the rabbit rectosigmoid. We have identified MAP kinase as one of
the enzymes activated by bombesin, performed immunological studies,
blocking the activation of MAP kinase and conducted confocal
localization of MAP kinase in relation to heat shock protein (hsp27),
a protein postulated to be involved in the sustained contraction of
smooth muscle. Immunoblotting revealed two forms of MAP kinase (42
and 44 kDa). Activation of MAP kinase by bombesin was rapid, reaching
a maximum in 30 sec and subsequently declined. [D-Phe6, Leu13,
y(CH2NH), Phe14] BN-(6-14), a potent bombesin antagonist, and PKC
inhibitors, H7, calphostin-C and chelerythrine, inhibited the
increase in MAP kinase induced by bombesin. Immunofluorescent dual
labeling and confocal microscopy indicates that these two proteins
are closely distributed in resting cells and that during bombesin
-induced contraction, MAP kinase translocates accompanied by hsp27. In
conclusion, a series of events involving PKC activation, MAP kinase
activation and MAP kinase-hsp27 translocation could be the signaling
pathway involved in bombesin-induced sustained contraction.
Received 27 September 1994; accepted in final form 28 April 1995.
APS Manuscript Number G378-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 26 May 1995.