Mitogen-activated protein kinase phosphatase 1 inhibits the stimulation of gene expression by hypertrophic agonists in cardiac myocytes.
The effect of constitutive expression of mitogen-activated protein kinase (MAPK) phosphatase 1 (MKP-1) on gene expression in response to hypertrophic agonists was examined in cultured neonatal rat ventricular myocytes. Luciferase (LUX) reporter genes linked to promoters for atrial natriuretic factor, ventricular myosin light chain 2, beta-myosin heavy chain, skeletal muscle alpha-actin (SkM alpha-actin) and serum response element-regulated c-fos (c-fos-SRE) were transfected into cardiomyocytes. Phenylephrine (PE; 10 microM), phorbol 12-myristate 13-acetate (1 microM) and endothelin 1 (10 nM) stimulated the expression of these various reporter genes by 2. 5-20-fold. MKP-1 inhibited these effects by 60-85%. In contrast, MKP-1 had no effect on the expression of a constitutively active Rous sarcoma virus-LUX reporter gene. A catalytically inactive mutant MKP-1CS (cysteine-->serine mutation) and the broad-specificity protein tyrosine phosphatase 1B (PTP-1B) had no significant effect on any reporter gene tested. MKP-1 had much less effect on the morphological features accompanying agonist-induced cardiac hypertrophy. PE (10 microM) increased myocyte area by 59% but this effect was only decreased by one-third by MKP-1 and was also partly decreased (by 25%) by expression of PTP-1B. PE also altered cell shape but this was unaffected by MKP-1. There was also no clear effect of MKP-1 on the organization of the contractile apparatus into sarcomeric structures in the presence of 10 microM PE. We conclude that the transcriptional responses accompanying cardiac myocyte hypertrophy are dependent on an MKP-1-sensitive step, presumably the activation of one or members of the MAPK family, but that cell size, shape and myofibrillar organization are much less sensitive to inhibition by MKP-1.
Fuller
S J
SJ
Cardiac Medicine, Imperial College School of Medicine at NHLI, University of London, Dovehouse Street, London SW3 6LY, UK.
Davies
E L
EL
Gillespie-Brown
J
J
Sun
H
H
Tonks
N K
NK
D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D054638:Dual Specificity Phosphatase 1; D019332:Endothelin-1 / Q000494:pharmacology; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D017874:Immediate-Early Proteins / Q000378:metabolism*; D008156:Luciferases / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1; D009206:Myocardium / Q000378:metabolism*; D010656:Phenylephrine / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012518:Sarcomeres / Q000648:ultrastructure; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D018797:Cell Cycle Proteins; D019332:Endothelin-1; D017874:Immediate-Early Proteins; D010656:Phenylephrine; D009320:Atrial Natriuretic Factor; D008156:Luciferases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054638:Dual Specificity Phosphatase 1; C517021:Dusp1 protein, rat; D017027:Protein Tyrosine Phosphatases; D013755:Tetradecanoylphorbol Acetate