Activation of protein kinase B/Akt by urocortin is essential for its ability to protect cardiac cells against hypoxia/reoxygenation-induced cell death.
Urocortin (Ucn), is a peptide related to hypothalamic corticotrophin-releasing factor (CRF) and binds with a high affinity to the CRF-R2 beta receptor which is expressed in the heart. Ucn promotes cardiac myocyte survival against hypoxia reoxygenation (HR) injury and this involves activation of the mitogen activated protein kinase pathway (MEK1/2 p42/44 MAPK). In this study we report that Ucn stimulates the phosphorylation of protein kinase B (PKB/Akt) via phosphatidylinositol (PI) 3-OH kinase (PI-3 kinase). To investigate the signalling pathways that mediate the anti-apoptotic and cell survival effect of Ucn in hypoxia reoxygenation (HR), gene based inhibitors of MEK1/2, PI-3 kinase and Akt were over-expressed in rat neonatal cardiac myocytes and cell survival effects against HR were assessed. The dominant negative mutants of the MEK1/2, PI-3 kinase and Akt inhibited Ucn mediated cardioprotection in HR and active PI-3 kinase was itself cardioprotective. In addition, chemical inhibitors of the PI-3 kinase pathway, wortmannin and LY294002 inhibit Ucn mediated cardioprotection in HR in both neonatal and adult cardiac myocytes. Hence the PI-3 kinase/Akt pathway is required in addition to MEK1/2 to mediate Ucn cardioprotection in HR. To our knowledge this is the first report of the activation of the PI-3 kinase/Akt pathway by a member of the CRF family of peptides.
Brar
Bhawanjit K
BK
Medical Molecular Biology Unit, Institute of Child Health, 30 Guilford Street, London, WC1N 1EH, UK.
Stephanou
Anastasis
A
Knight
Richard
R
Latchman
David S
DS
D000730:Androstadienes / Q000378:metabolism; D002316:Cardiotonic Agents / Q000378:metabolism; D016923:Cell Death; D002478:Cells, Cultured; D002867:Chromones / Q000378:metabolism; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism*; D004789:Enzyme Activation; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D009025:Morpholines / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D015428:Myocardial Reperfusion Injury / Q000201:enzymology* / Q000378:metabolism; D009206:Myocardium / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation; D010770:Phosphotransferases; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D054832:Urocortins; D000077191:Wortmannin
D000730:Androstadienes; D002316:Cardiotonic Agents; D002867:Chromones; D009025:Morpholines; D011518:Proto-Oncogene Proteins; D054832:Urocortins; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D003346:Corticotropin-Releasing Hormone; D010770:Phosphotransferases; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D020929:Mitogen-Activated Protein Kinase Kinases; D000077191:Wortmannin