Role of c-Cbl-Dependent Regulation of Phospholipase Cγ1 Activation in Experimental Choroidal Neovascularization

PURPOSE. Activation of phospholipase C gamma 1 (PLC gamma 1) by vascular endothelial growth factor receptor (VEGFR)-2 is necessary for proliferation and tube formation of endothelial cells in vitro. Previous work has demonstrated that Casitas B-lineage lymphoma (c-Cbl) promotes ubiquitination of PLC gamma 1 and suppression of its tyrosine phosphorylation. This study was designed to evaluate the importance of PLC gamma 1 and c-Cbl in experimental choroidal neovascularization (CNV). METHODS. The role of PLC gamma 1 was studied in three models of angiogenesis: the endothelial cell culture system, the chorioallantoic membrane (CAM) assay, and the laser-induced CNV model. Endothelial cells were analyzed for the role of PLC gamma 1 in promoting tube formation. CAMs were incubated with pharmacologic agents that either inhibit or stimulate PLC gamma 1. CNV was induced in wild-type and c-Cbl-knockout mice, and the progression of CNV was evaluated by fluorescein angiography. RESULTS. Activation of PLC gamma 1 was necessary for tube formation of endothelial cells. PLC gamma 1 stimulation increased the growth of blood vessels and conversely, PLC gamma 1 inhibition decreased the growth of blood vessels in the CAM model. CNV lesions in the c-Cbl-knockout mice were significantly greater in number, more confluent, and increased in size with time, compared with those in the control wild-type mice. CONCLUSIONS. The data show that PLC gamma 1 plays an important role in angiogenesis. Loss of c-Cbl results in enhanced CNV in the eye. The study also shows that c-Cbl plays an important role in ocular angiogenesis, suggesting that modulation of c-Cbl activity or inhibition of PLC gamma 1 would be a compelling target for antiangiogenesis therapy. (Invest Ophthalmol Vis Sci. 2010;51:6803-6809) DOI:10.1167/iovs.10-5255