Abstract
Purpose: :
Angiogenesis, a hallmark step in ocular neovascularization, is primarily driven by the function of VEGF on its receptor, VEGFR-2. Central to the initiation of angiogenesis by VEGF, the abundance of VEGFR-2 on the surface of endothelial cells is essential for VEGF to recognize and activate VEGFR-2. We have identified PDCL3 (phosducin like 3) as a novel protein involved in the stabilization of VEGFR-2 by serving as a VEGFR-2 co-chaperone protein.
Methods: :
Various molecular and cell biology methods including Western blotting, site direct mutagenesis, endothelial cell culture systems, knock-down experiments with siRNA, invitro-angiogenesis assays and immunohistochemical studies on mouse eyes exposed to hypoxia were used to study the role of PDCL3 in regulation of VGFR2 in endometrial cells.
Results: :
PDCL3 expression is upregulated by hypoxia in endothelial cells and its expression is responsible for hypoxia-induced expression of VEGFR-2. PDCL3 co-localizes with VEGFR-2 in cells and recognizes the JM domain of VEGFR-2. Over-expression of PDCL3 increases, whereas depleting its expression by siRNA in endothelial cells reduces the abundance of VEGFR-2 protein. Upregulation of PDCL3 markedly increases ligand-mediated activation of VEGFR-2.
Conclusions: :
Our studies provide experimental evidence for the role of PDCL3 in governing the angiogenic pathway by controlling VEGFR-2 destruction. PDCL3 elicits its activity by rendering VEGFR-2 to a more stable protein by preventing its ubiquitylation and degradation. PDCL3 activity is required for endothelial cell proliferation and tube formation of endothelial cells and angiogenesis.
Keywords: retinal neovascularization • ischemia • pathobiology