Mek-1 is required for pdgf-induced erk activation and dna synthesis
in tracheal myocytes.
Karpova, Alla Yu., Mark K. Abe, Jing Li, Pai T. Liu, Jessica M. Rhee,
Wen-Liang Kuo, and Marc B. Hershenson.
Department of Pediatrics, Department of Pharmacological and
Physiological Sciences, University of Chicago, Chicago, IL 60637
APStracts 3:0198L, 1996.
We tested whether activation of mitogen-activated protein
kinase/extracellular signal-regulated kinase kinase-1 (MEK-1) is
required and sufficient for extracellular signal-regulated kinase
(ERK) activation in airway smooth muscle cells. First, we transiently
co-transfected bovine tracheal myocytes with an epitope-tagged ERK2
and either a dominant-negative or constitutively-active form of the
gene encoding MEK-1, and assessed ERK2 activation by in vitro
phosphorylation assay. Expression of the dominant-negative MEK-1
inhibited platelet-derived growth factor (PDGF)-induced ERK2
activation, whereas expression of the constitutively-active MEK-1
induced ERK2 activation, suggesting that MEK-1 is required and
sufficient for ERK activation in these cells. Next, we assessed the
effect of PD98059, a synthetic MEK inhibitor, on PDGF-induced MEK-1
and ERK activation. PD98059 (10 [mu]M) inhibited both MEK-1 and ERK
activation, confirming that MEK-1 is required for ERK activation in
bovine tracheal myocytes. PD98059 had no effect on Src or Raf
-1?activity, evidence that PD98059 is a specific inhibitor of MEK in
this system. Finally, PD98059 reduced PDGF-induced [3H]-thymidine
incorporation in a concentration-dependent manner, suggesting that
catalytic activation of MEK-1 and ERKs is required for DNA synthesis.
We conclude that MEK-1 is required for PDGF-induced ERK activation in
bovine tracheal myocytes, and that MEK-1 and ERKs are required for
PDGF-induced DNA synthesis in these cells.
Received 29 May 1996; accepted in final form 17 October 1996.
APS Manuscript Number L157-6.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 November 1996