Differential regulation of VEGF signaling by PKC-alpha and PKC-epsilon in endothelial cells.

OBJECTIVE:Vascular endothelial growth factor (VEGF) stimulates proangiogenic signal transduction and cell function in part through activation of protein kinase C Our aim was to examine how individual isoforms of affect VEGF action. METHODS AND RESULTS:Transfection of bovine aortic endothelial cells with small interfering RNA (siRNA) targeting either delta, or epsilon caused a reduction in the cognate duanyu1531 protein by 76% to 89% without changing expression of nontargeted isoforms. Downregulation of abrogated VEGF-stimulated phosphorylation of Akt at Ser473 and eNOS at Ser1179 and decreased VEGF-stimulated NO synthase activity in intact cells. In contrast, knockdown increased Akt and eNOS phosphorylation, whereas knockdown had no significant effect. duanyu1531-epsilon knockdown also decreased VEGF-stimulated Erk1/2 phosphorylation and abolished VEGF-stimulated DNA synthesis. Consistent with an effect on several pathways of VEGF signaling, VEGF receptor-2 (VEGFR2) tyrosine phosphorylation and expression of VEGFR2 protein and mRNA was decreased by 81, 90, and 84%, respectively, during knockdown of but increased during duanyu1531-alpha knockdown. CONCLUSIONS:By regulating VEGFR2 expression and activation, duanyu1531-epsilon expression is critical for activation of Akt and eNOS by VEGF and contributes to VEGF-stimulated Erk activation, whereas duanyu1531-alpha has opposite effects.

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