Up-regulation of c-jun mRNA in cardiac myocytes requires the extracellular signal-regulated kinase cascade, but c-Jun N-terminal kinases are required for efficient up-regulation of c-Jun protein

Biochem J. 2002 Nov 15;368(Pt 1):101-10. doi: 10.1042/BJ20021083.


Cardiac hypertrophy, an important adaptational response, is associated with up-regulation of the immediate early gene, c- jun, which encodes the c-Jun transcription factor. c-Jun may feed back to up-regulate its own transcription and, since the c-Jun N-terminal kinase (JNK) family of mitogen-activated protein kinases (MAPKs) phosphorylate c-Jun(Ser-63/73) to increase its transactivating activity, JNKs are thought to be the principal factors involved in c- jun up-regulation. Hypertrophy in primary cultures of cardiac myocytes is induced by endothelin-1, phenylephrine or PMA, probably through activation of one or more of the MAPK family. These three agonists increased c- jun mRNA with the rank order of potency of PMA approximately endothelin-1>phenylephrine. Up-regulation of c- jun mRNA by endothelin-1 was attenuated by inhibitors of protein kinase C (GF109203X) and the extracellular signal-regulated kinase (ERK) cascade (PD98059 or U0126), but not by inhibitors of the JNK (SP600125) or p38-MAPK (SB203580) cascades. Hyperosmotic shock (0.5 M sorbitol) powerfully activates JNKs, but did not increase c- jun mRNA. These data suggest that ERKs, rather than JNKs, are required for c- jun up-regulation. However, endothelin-1 and phenylephrine induced greater up-regulation of c-Jun protein than PMA and phosphorylation of c-Jun(Ser-63/73) correlated with the level of c-Jun protein. Up-regulation of c-Jun protein by endothelin-1 was attenuated by inhibitors of protein kinase C and the ERK cascade, probably correlating with a primary input of ERKs into transcription. In addition, SP600125 inhibited the phosphorylation of c-Jun(Ser-63/73), attenuated the increase in c-Jun protein induced by endothelin-1 and increased the rate of c-Jun degradation. Thus whereas ERKs are the principal MAPKs required for c- jun transcription, JNKs are necessary to stabilize c-Jun for efficient up-regulation of the protein.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Endothelin-1 / pharmacology
  • JNK Mitogen-Activated Protein Kinases
  • Mitogen-Activated Protein Kinases / metabolism*
  • Myocardium / enzymology
  • Myocardium / metabolism*
  • Osmotic Pressure
  • Phenylephrine / pharmacology
  • Proto-Oncogene Proteins c-jun / genetics
  • Proto-Oncogene Proteins c-jun / metabolism*
  • RNA, Messenger / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Signal Transduction
  • Tetradecanoylphorbol Acetate / pharmacology
  • Up-Regulation / drug effects


  • Endothelin-1
  • Proto-Oncogene Proteins c-jun
  • RNA, Messenger
  • Phenylephrine
  • JNK Mitogen-Activated Protein Kinases
  • Mitogen-Activated Protein Kinases
  • Tetradecanoylphorbol Acetate