Akt down-regulation of p38 signaling provides a novel mechanism of vascular endothelial growth factor-mediated cytoprotection in endothelial cells.
Vascular endothelial growth factor (VEGF) utilizes a phosphoinositide 3-kinase (PI 3-kinase)/Akt signaling pathway to protect endothelial cells from apoptotic death. Here we show that PI 3-kinase/Akt signaling promotes endothelial cell survival by inhibiting p38 mitogen-activated protein kinase (MAPK)-dependent apoptosis. Blockade of the PI 3-kinase or Akt pathways in conjunction with serum withdrawal stimulates p38-dependent apoptosis. Blockade of PI 3-kinase/Akt also led to enhanced VEGF activation of p38 and apoptosis. In this context, the pro-apoptotic effect of VEGF is attenuated by the p38 MAPK inhibitor SB203580. VEGF stimulation of endothelial cells or infection with an adenovirus expressing constitutively active Akt causes MEKK3 phosphorylation, which is associated with decreased MEKK3 kinase activity and down-regulation of MKK3/6 and p38 MAPK activation. Conversely, activation-deficient Akt decreases VEGF-stimulated MEKK3 phosphorylation and increases MKK/p38 activation. Activation of MKK3/6 is not dependent on Rac activation since dominant negative Rac does not decrease p38 activation triggered by inhibition of PI 3-kinase. Thus, cross-talk between the Akt and p38 MAPK pathways may regulate the level of cytoprotection versus apoptosis and is a new mechanism to explain the cytoprotective actions of Akt.
Gratton
J P
JP
Department of Pharmacology and Molecular Cardiobiology Program, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, Connecticut 06536, USA.
Morales-Ruiz
M
M
Kureishi
Y
Y
Fulton
D
D
Walsh
K
K
Sessa
W C
WC
D000256:Adenoviridae / Q000235:genetics / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002417:Cattle; D016923:Cell Death; D002460:Cell Line; D002470:Cell Survival; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D016228:Endothelial Growth Factors / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D008222:Lymphokines / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction; D013997:Time Factors; D014471:Umbilical Veins / Q000166:cytology; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D048051:p38 Mitogen-Activated Protein Kinases
D016228:Endothelial Growth Factors; D004791:Enzyme Inhibitors; D007093:Imidazoles; D008222:Lymphokines; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011725:Pyridines; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D048051:p38 Mitogen-Activated Protein Kinases; C494918:AKT1 protein, human; C093642:SB 203580