Insulin-mediated stimulation of protein kinase Akt: A potent survival signaling cascade for endothelial cells.

Content Provider	Semantic Scholar
Author	Hermann, Corinna A. Assmus, Birgit Urbich, Carmen Zeiher, Andreas Michael Dimmeler, Stefanie
Copyright Year	2000
Abstract	Insulin exerts potent antiapoptotic effects in neuronal cells and has been suggested to promote angiogenesis. Therefore, we investigated whether insulin inhibits tumor necrosis factor-alpha (TNF-alpha)-induced apoptosis in human umbilical vein endothelial cells (HUVECs). Because insulin has been shown to stimulate the protein kinase Akt, we investigated whether activation of Akt contributes to the apoptosis-suppressive effect of insulin and characterized the downstream signaling pathway. Incubation with insulin dose-dependently prevented apoptosis induced by TNF-alpha (50 ng/mL). The extent of apoptosis suppression by insulin was similar to the effect of vascular endothelial growth factor. Pharmacological inhibition of Akt activation or overexpression of a dominant-negative Akt mutant prevented the antiapoptotic effect of insulin. Furthermore, we investigated the effect of TNF-alpha on Akt phosphorylation by Western blot analysis with the use of a phosphospecific Akt antibody. Incubation of HUVECs with TNF-alpha induced a marked dephosphorylation of Akt. Insulin counteracted this TNF-alpha-induced dephosphorylation of Akt. Furthermore, we investigated the downstream signaling events. Akt has been shown to mediate its apoptosis-suppressive effects via phosphorylation of Bad or caspase-9. However, incubation with insulin did not lead to enhanced phosphorylation of Bad at Ser 136 or Ser 112. In contrast, insulin inhibited caspase-9 activity and prevented caspase-9-induced apoptosis. Mutation of the Akt site within caspase-9 significantly reduced the apoptosis-suppressive effect of insulin. The present study demonstrates an important role for insulin-mediated Akt activation in the prevention of endothelial cell apoptosis, which may importantly contribute to cell homeostasis and the integrity of the endothelium. In endothelial cells, Akt seems to mediate its antiapoptotic effect, at least in part, via phosphorylation of caspase-9 rather than Bad.
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Ending Page	2
Page Count	2
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Alternate Webpage(s)	http://atvb.ahajournals.org/content/atvbaha/20/2/402.full.pdf?download=true
Alternate Webpage(s)	http://atvb.ahajournals.org/content/atvbaha/20/2/402.full.pdf
PubMed reference number	10669636v1
Volume Number	20
Issue Number	2
Journal	Arteriosclerosis, thrombosis, and vascular biology
Language	English
Access Restriction	Open
Subject Keyword	Antiapoptotic Agent Apoptosis Bad protein Cascade Device Component Endothelial Growth Factors Growth Factor Human Umbilical Vein Endothelial Cells Insulin Neoplasms Protein Kinases Protein dephosphorylation Proto-Oncogene Proteins c-akt Signal Transduction Pathways Tumor Necrosis Factors Umbilicus (Anatomy) caspase-9 endothelial cell apoptotic process type I interferon receptor
Content Type	Text
Resource Type	Article