ABSTRACT
Wet age-related macular degeneration (AMD) is a leading cause of vision loss in old patients. In wet AMD,
excessive vascular endothelial growth factor (VEGF) causes abnormal angiogenesis and vascular leakage,
which in turn damages the retina. The overall goal of this proposal is to determine the mechanism how excessive
VEGF induces transition from quiescent blood vessels to pathological leaky angiogenesis in wet AMD by
studying the fundamental roles of VEGFR2 trafficking. Angiogenesis is restrained in quiescent healthy
endothelial cells (ECs), where VEGFR2 trafficking is limited by the interaction with VE-cadherin at adherens
junctions (AJs). In contrast, marked VEGFR2 trafficking is evident in angiogenic ECs, where VEGFR2
translocates to filopodia tips that extend towards the VEGF ligand. We provided the first evidence that VEGFR2
is directly transported by the kinesin-3 family protein, KIF13B, a microtubules plus-end motor, to filopodia of
sprouting ECs. Based on our finding, we will test our central hypothesis that KIF13B mediates VEGFR2
trafficking away from AJs to induce AJ disassembly and vascular leakage, and the directional trafficking of
VEGFR2 to filopodia induces pathological angiogenesis in response to excessive VEGF in wet AMD. Our
Specific Aims will test the following hypotheses; 1) KIF13B-mediated VEGFR2 trafficking from AJs breaks the
critical interaction between VEGFR2 and VE-cadherin involved in stabilizing AJs, thus induces AJ disassembly
and vascular leakage. 2) VEGF signaling induces KIF13B-mediated directional trafficking of VEGFR2 to filopodia
extending toward VEGF, and the trafficking is required for sprouting angiogenesis. 3) KIF13B-mediated VEGFR2
trafficking is pathogenesis in wet AMD, thus the inhibition of the trafficking is a promising strategy for the therapy
of wet AMD. To rigorously test these hypotheses, our lab has generated powerful tools (genetic mouse models
and peptide inhibitors) that have led to conceptual advances. EC specific KIF13B knockout mice display a
selective angiogenic defect in the pathological setting. A small peptide inhibitor disrupting the KIF13B/VEGFR2
interaction, termed KAI, inhibited choroidal neovascularization (CNV) in wet AMD model in mice. Using these
powerful tools, we will examine the roles of KIF13B in VEGF-induced permeability of ocular blood vessels, live
imaging of directional VEGFR2 trafficking in choroidal sprouting ex vivo, and pathology of wet AMD,
characterized by abnormal angiogenesis, vascular leakage, and inflammation, using laser-induced CNV model.
If successful, our proposed studies provide the novel concept of angiogenesis regulation by targeting VEGFR2
trafficking.