Constitutive Endocytosis of VEGFR2 Protects the Receptor against Shedding.
VEGFR2 plays a fundamental role in blood vessel formation and in life threatening diseases, such as cancer angiogenesis and cardiovascular disorders. Although inactive growth factor receptors are mainly localized at the plasma membrane, VEGFR2 undergoes constitutive endocytosis (in the absence of ligand) and recycling. Intriguingly, the significance of these futile transport cycles of VEGFR2 remains unclear. Here we found that, unexpectedly, the function of constitutive endocytosis of VEGFR2 is to protect the receptor against plasma membrane cleavage (shedding), thereby preserving the functional state of the receptor until the time of activation by VEGF. Inhibition of constitutive endocytosis of VEGFR2, by interference with the function of clathrin, dynamin, or Rab5, increases dramatically the cleavage/shedding of VEGFR2. Shedding of VEGFR2 produces an N-terminal soluble fragment (100 kDa, s100), which is released in the extracellular space, and a residual C-terminal part (130 kDa, p130) that remains integrated at the plasma membrane. The released soluble fragment (s100) co-immunoprecipitates with VEGF, in line with the topology of the VEGF-binding domain at the N terminus of VEGFR2. Increased shedding of VEGFR2 (via inhibition of constitutive endocytosis) results in reduced response to VEGF, consistently with the loss of the VEGF-binding domain from the membrane remnant of VEGFR2. These data suggest that constitutive internalization of VEGFR2 protects the receptor against shedding and provides evidence for an unprecedented mechanism via which endocytosis can regulate the fate and activity of growth factor receptors.
From the Institute of Molecular Biology and Biotechnology-Biomedical Research, Foundation for Research and Technology, 45110 Ioannina and the Department of Medicine, Laboratory of Biological Chemistry, School of Health Sciences, University of Ioannina, 45110 Ioannina, Greece.
Dimitris
D
Basagiannis
From the Institute of Molecular Biology and Biotechnology-Biomedical Research, Foundation for Research and Technology, 45110 Ioannina and the Department of Medicine, Laboratory of Biological Chemistry, School of Health Sciences, University of Ioannina, 45110 Ioannina, Greece savvas_christoforidis@imbb.forth.gr schristo@uoi.gr.
Savvas
S
Christoforidis
D004705:Endocytosis / Q000502:physiology*; D061307:Human Umbilical Vein Endothelial Cells / Q000378:metabolism*; D006801:Humans; D000072417:Protein Domains; D021381:Protein Transport / Q000502:physiology; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000235:genetics / Q000378:metabolism*
C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; C000588866:KDR protein, human; D040301:Vascular Endothelial Growth Factor Receptor-2
clathrin; clathrin-mediated endocytosis; dynamin; endocytosis; matrix metalloproteinase (MMP); membrane trafficking; shedding; signaling; vascular endothelial growth factor (VEGF); vascular endothelial growth factor receptor 2