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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2009;29:1119.)
© 2009 American Heart Association, Inc.

Cell Biology/Signaling

Rab GTPase Regulation of VEGFR2 Trafficking and Signaling in Endothelial Cells

Helen M. Jopling; Adam F. Odell; Nigel M. Hooper; Ian C. Zachary; John H. Walker; Sreenivasan Ponnambalam

From the Endothelial Cell Biology Unit (H.M.J., A.F.O., J.H.W., S.P.) and Proteolysis Research Group (N.M.H.), Institute for Molecular & Cellular Biology, LIGHT Laboratories, University of Leeds, UK; and the Centre for Cardiovascular Biology and Medicine (I.C.Z.), Rayne Institute, University College London, UK.

Correspondence to S. Ponnambalam, Endothelial Cell Biology Unit, Institute for Molecular & Cellular Biology, LIGHT Laboratories, University of Leeds, Leeds LS2 9JT, UK. E-mail s.ponnambalam{at}leeds.ac.uk

Objective— Vascular endothelial growth factor receptor 2 (VEGFR2) is a receptor tyrosine kinase that regulates vascular physiology. However, mechanism(s) by which VEGFR2 signaling and trafficking is coordinated are not clear. Here, we have tested endocytic Rab GTPases for regulation of VEGFR2 trafficking and signaling linked to endothelial cell migration.

Methods and Results— Quiescent VEGFR2 displays endosomal localization and colocalization with the Rab5a GTPase, an early endosome fusion regulator. Expression of GTP or GDP-bound Rab5a mutants block activated VEGFR2 trafficking and degradation. Manipulation of Rab7a GTPase activity associated with late endosomes using overexpression of wild-type or mutant proteins blocks activated VEGFR2 trafficking and degradation. Depletion of Rab7a decreased VEGFR2 Y1175 phosphorylation but increased p42/44 (pERK1/2) MAPK phosphorylation. Endothelial cell migration was increased by Rab5a depletion but decreased by Rab7a depletion.

Conclusions— Rab5a and Rab7a regulate VEGFR2 trafficking toward early and late endosomes. Our data suggest that VEGFR2-mediated regulation of endothelial function is dependent on different but specific Rab-mediated GTP hydrolysis activity required for endosomal trafficking.

Key Words: VEGFR2 • Rab • trafficking • signaling • migration