MAP kinase- and Rho-dependent signals interact to regulate gene expression but not actin morphology in cardiac muscle cells.
Post-natal growth of cardiac muscle cells occurs by hypertrophy rather than division and is associated with changes in gene expression and muscle fiber morphology. We show here that the protein kinase MEKK1 can induce reporter gene expression from the atrial natriuretic factor (ANF) promoter, a genetic marker that is activated during in vivo hypertrophy. MEKK1 induced both stress-activated protein kinase (SAPK) and extracellular signal-regulated protein kinase (ERK) activity; however, while the SAPK cascade stimulated ANF expression, activation of the ERK cascade inhibited expression. C3 transferase, a specific inhibitor of the small GTPase Rho, also inhibited both MEKK- and phenylephrine-induced ANF expression, indicating an additional requirement for Rho-dependent signals. Microinjection or transfection of C3 transferase into the same cells did not disrupt actin muscle fiber morphology, indicating that Rho-dependent pathways do not regulate actin morphology in cardiac muscle cells. While active MEKK1 was a potent activator of hypertrophic gene expression, this kinase did not induce actin organization and prevented phenylephrine-induced organization. These data suggest that multiple signals control hypertrophic phenotypes. Positive and negative signals mediated by parallel MAP kinase cascades interact with Rho-dependent pathways to regulate hypertrophic gene expression while other signals induce muscle fiber morphology in cardiac muscle cells.
Thorburn
J
J
Program in Human Molecular Biology and Genetics, Eccles Institute of Human Genetics, University of Utah, Salt Lake City 84112, USA.
Xu
S
S
Thorburn
A
A
D016475:3T3 Cells; D036002:ADP Ribose Transferases / Q000494:pharmacology; D000199:Actins / Q000032:analysis; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000235:genetics; D001905:Botulinum Toxins; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D006332:Cardiomegaly / Q000201:enzymology / Q000503:physiopathology*; D018797:Cell Cycle Proteins; D054638:Dual Specificity Phosphatase 1; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology*; D017930:Genes, Reporter / Q000235:genetics; D049452:Green Fluorescent Proteins; D017874:Immediate-Early Proteins / Q000502:physiology; D008164:Luminescent Proteins / Q000235:genetics; D048728:MAP Kinase Kinase Kinase 1; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1; D018485:Muscle Fibers, Skeletal; D009206:Myocardium / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D010656:Phenylephrine / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases; D011494:Protein Kinases / Q000502:physiology; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000502:physiology*; D017027:Protein Tyrosine Phosphatases / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000502:physiology*; D051381:Rats; D012234:Rho Factor / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D018808:Transcription Factor AP-1 / Q000235:genetics
D000199:Actins; D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D017874:Immediate-Early Proteins; D008164:Luminescent Proteins; D012234:Rho Factor; D018808:Transcription Factor AP-1; D049452:Green Fluorescent Proteins; D010656:Phenylephrine; D009320:Atrial Natriuretic Factor; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048728:MAP Kinase Kinase Kinase 1; C482578:Map3k1 protein, mouse; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054638:Dual Specificity Phosphatase 1; C517020:Dusp1 protein, mouse; C517021:Dusp1 protein, rat; D017027:Protein Tyrosine Phosphatases; D001905:Botulinum Toxins; D020558:GTP Phosphohydrolases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one