Protein kinase C, but not tyrosine kinases or Ras, plays a critical role in angiotensin II-induced activation of Raf-1 kinase and extracellular signal-regulated protein kinases in cardiac myocytes.
Angiotensin II (AngII) induces cardiac hypertrophy through activating a variety of protein kinases. In this study, to understand how cardiac hypertrophy develops, we examined AngII-evoked signal transduction pathways leading to the activation of extracellular signal-regulated protein kinases (ERKs), which are reportedly critical for the development of cardiac hypertrophy, in cultured cardiac myocytes isolated from neonatal rats. Inhibition of protein kinase C (PKC) with calphostin C or down-regulation of PKC by pretreatment with a phorbol ester for 24 h abolished AngII-induced activation of Raf-1 and ERKs, and addition of a phorbol ester conversely induced a marked increase in the activities of Raf-1 and ERKs. Pretreatment with two chemically and mechanistically dissimilar tyrosine kinase inhibitors, genistein and tyrphostin, did not attenuate AngII-induced activation of ERKs. In contrast, genistein strongly blocked insulin-induced ERK activation in cardiac myocytes. Although pretreatment with manumycin, a Ras farnesyltransferase inhibitor, or overexpression of a dominant-negative mutant of Ras inhibited insulin-induced ERK activation, neither affected AngII-induced activation of ERKs. Overexpression of a dominant-negative mutant of Raf-1 completely suppressed ERK2 activation by AngII, endothelin-1, and insulin. These results suggest that PKC and Raf-1, but not tyrosine kinases or Ras, are critical for AngII-induced activation of ERKs in cardiac myocytes.
Zou
Y
Y
Department of Medicine III, University of Tokyo School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113, Japan. komuro-tky@umin.u-tokyo.ac.jp
Komuro
I
I
Yamazaki
T
T
Aikawa
R
R
Kudoh
S
S
Shiojima
I
I
Hiroi
Y
Y
Mizuno
T
T
Yazaki
Y
Y
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D019332:Endothelin-1 / Q000494:pharmacology; D004789:Enzyme Activation; D019833:Genistein; D007328:Insulin / Q000494:pharmacology; D007529:Isoflavones / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1; D009206:Myocardium / Q000201:enzymology*; D011090:Polyenes / Q000494:pharmacology; D053284:Polyunsaturated Alkamides; D011493:Protein Kinase C / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018631:ras Proteins / Q000378:metabolism*
D019332:Endothelin-1; D007328:Insulin; D007529:Isoflavones; D011090:Polyenes; D053284:Polyunsaturated Alkamides; D011518:Proto-Oncogene Proteins; D000804:Angiotensin II; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D018631:ras Proteins; D013755:Tetradecanoylphorbol Acetate; C054474:manumycin