Objective: Vascular endothelial growth factor (VEGF) is a potent angiogenic growth factor that promotes endothelial cell (EC) survival, migration, and permeability. The forkhead transcription factors FKHR, FKHRL1, and AFX are mammalian orthologues of DAF-16, a forkhead protein that controls longevity in Caenorhabditis elegans. In this study, we examined whether VEGF is coupled to phosphatidyl inositol 3-kinase (PI3K)/Akt/forkhead in ECs.
Methods and results: We demonstrate that human ECs express members of the forkhead family (FKHR, FKHRL1, and AFX) and that VEGF modulates the phosphorylation, subcellular localization, and transcriptional activity of one or more of these isoforms by a PI3K/Akt signaling pathway. VEGF inhibited EC apoptosis, promoted DNA synthesis and the G(1)-to-S transition, and reduced expression of the cyclin-dependent kinase inhibitor p27(kip1). Each of these effects was blocked by the PI3K inhibitor LY294002 or by a phosphorylation-resistant mutant of FKHRL1, but not by wild-type FKHRL1.
Conclusions: These results suggest that VEGF signaling in ECs is coupled to forkhead transcription factors through a PI3K/Akt-dependent pathway.