c-Jun N-terminal kinase-interacting protein 1 inhibits gene expression in response to hypertrophic agonists in neonatal rat ventricular myocytes.
G(q)-coupled receptor agonists, such as endothelin-1 (ET-1) and phenylephrine (PE), initiate a hypertrophic response in cardiac myocytes that is characterized by increased expression of atrial natriuretic factor (ANF), beta-myosin heavy chain (beta-MHC), skeletal muscle alpha-actin (SkalphaA) and ventricular myosin light chain-2 (vMLC2). ET-1 and PE activate both the extracellular signal-regulated kinases and c-Jun N-terminal kinases (JNKs) in cardiac myocytes, but the extent to which each contributes to the hypertrophic response is uncertain. Here we have used the JNK-binding domain of JNK-interacting protein 1 (JIP-1), a cytosolic scaffold protein that binds to JNK and inhibits its signalling when overexpressed, to assess the contribution of JNK activation to the hypertrophic response. Expression of JIP-1 inhibited the increase in ANF, beta-MHC, SkalphaA and vMLC2 reporter gene expression in response to ET-1 (by 45-86%) and PE (by 56-60%). However, activation of these reporter genes by PMA, which does not activate JNK significantly in myocytes, was much less affected by overexpression of JIP-1. JIP-1 also failed to inhibit reporter gene activation in response to constitutively active Ras or Raf, but attenuated reporter gene activation induced by a constitutively active mutant of mitogen-activated protein kinase kinase kinase 1 (MEKK1), an upstream kinase that preferentially activates JNKs, by 50%. Overexpression of JIP-1 also significantly reduced the increase in cell area in response to PE from 63% to 56%, but had no effect on the increase in cell size in response to ET-1 (38%). These results suggest that activation of the JNK pathway contributes to the transcriptional and morphological responses to G(q) receptor-coupled hypertrophic agonists.
Finn
S G
SG
NHLI Division (Cardiac Medicine), Imperial College School of Medicine, Dovehouse Street, London SW3 6LY, UK.
Dickens
M
M
Fuller
S J
SJ
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000831:Animals, Newborn; D006332:Cardiomegaly / Q000378:metabolism* / Q000473:pathology; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D048429:Cell Size; D002478:Cells, Cultured; D019332:Endothelin-1 / Q000494:pharmacology*; D017781:Genes, Immediate-Early; D006352:Heart Ventricles / Q000378:metabolism / Q000473:pathology; D048031:JNK Mitogen-Activated Protein Kinases; D020935:MAP Kinase Signaling System; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D010656:Phenylephrine / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015533:Transcriptional Activation; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D019332:Endothelin-1; C110528:Mapk8ip1 protein, rat; D010656:Phenylephrine; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases