Dissociation of p44 and p42 mitogen-activated protein kinase activation from receptor-induced hypertrophy in neonatal rat ventricular myocytes.
In response to hormones and mechanical stretch, neonatal rat ventricular myocytes exhibit a hypertrophic response that is characterized by induction of cardiac-specific genes and increased myocardial cell size. Hypertrophic stimuli also activate mitogen-activated protein kinase (MAPK), an enzyme thought to play a central role in the regulation of cell growth and differentiation. To determine if MAPK activation is sufficient for acquisition of the molecular and morphological features of cardiac hypertrophy we compared four agonists that stimulate G protein-coupled receptors. Whereas phenylephrine and endothelin transactivate cardiac-specific promoter/luciferase reporter genes, increase atrial natriuretic factor (ANF) expression, and promote myofilament organization, neither carbachol nor ATP induces these responses. Interestingly, all four agonists activate both the p42 and the p44 isoforms of MAPK. Furthermore, the kinetics of MAPK activation are not different for the hypertrophic agonist phenylephrine and the nonhypertrophic agonist carbachol. Transient transfection of myocytes with dominant-interfering mutants of p42 and p44 MAPK failed to block phenylephrine-induced ANF expression, although Ras-induced gene expression was inhibited by expression of the mutant MAPK constructs. Moreover, PD 098059, an inhibitor of MAPK kinase, blocked phenylephrine-stimulated MAPK activity but not ANF reporter gene expression. Thus, MAPK activation is not sufficient for G protein receptor-mediated induction of cardiac cell growth and gene expression and is apparently not required for transcriptional activation of the ANF gene.
Post
G R
GR
Department of Pharmacology, University of California, San Diego, La Jolla, California 92093-0636, USA.
Goldstein
D
D
Thuerauf
D J
DJ
Glembotski
C C
CC
Brown
J H
JH
D008841:Actin Cytoskeleton / Q000648:ultrastructure; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D009320:Atrial Natriuretic Factor / Q000235:genetics; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D006332:Cardiomegaly / Q000201:enzymology*; D016232:Endothelins / Q000494:pharmacology; D004789:Enzyme Activation; D005419:Flavonoids / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D009206:Myocardium / Q000166:cytology / Q000201:enzymology*; D009219:Myosin-Light-Chain Kinase / Q000235:genetics; D010656:Phenylephrine / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011956:Receptors, Cell Surface / Q000502:physiology
D000316:Adrenergic alpha-Agonists; D016232:Endothelins; D005419:Flavonoids; D011956:Receptors, Cell Surface; D010656:Phenylephrine; D009320:Atrial Natriuretic Factor; D000255:Adenosine Triphosphate; D002217:Carbachol; D011505:Protein-Tyrosine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D009219:Myosin-Light-Chain Kinase; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D016283:Proto-Oncogene Proteins p21(ras); C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one