PLD1-dependent PKCγ activation downstream to Src is essential for the development of pathologic retinal neovascularization

Vascular endothelial growth factor (VEGF) appears to be an important mediator of pathologic retinal angiogenesis. In understanding the mechanisms of pathologic retinal neovascularization, we found that VEGF activates PLD1 in human retinal microvascular endothelial cells, and this event is dependent on Src. In addition, VEGF activates protein kinase C-gamma (PKC gamma) via Src-dependent PLD1 stimulation. Inhibition of Src, PLD1, or PKC gamma via pharmacologic, dominant negative mutant, or siRNA approaches significantly attenuated VEGF-induced human retinal microvascular endothelial cell migration, proliferation, and tube formation. Hypoxia also induced Src-PLD1-PKC gamma signaling in retina, leading to retinal neovascularization. Furthermore, siRNA-mediated down-regulation of VEGF inhibited hypoxia-induced Src-PLD1-PKC gamma activation and neovascularization. Blockade of Src-PLD1-PKC gamma signaling via the siRNA approach also suppressed hypoxia-induced retinal neovascularization. Thus, these observations demonstrate, for the first time, that Src-dependent PLD1-PKC gamma activation plays an important role in pathologic retinal angiogenesis. (Blood. 2010; 116(8): 1377-1385)