Tyrosine residues 951 and 1059 of vascular endothelial growth factor receptor-2 (KDR) are essential for vascular permeability factor/vascular endothelial growth factor-induced endothelium migration and proliferation, respectively

Vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) exerts its multiple functions by activating two receptor tyrosine kinases, Flt-1 (VEGFR-1) and KDR (VFGFR-2), both of which are selectively expressed on primary vascular endothelium. To dissect the respective signaling pathwa ys and biological functions mediated by these receptors in primary endothel ial cells with two receptors intact, we, recently developed chimeric recept ors (EGDR and EGLT) in which the extracellular domain of the epidermal grow th factor receptor was fused to the transmembrane domain and intracellular domain of KDR and Flt-1, respectively. With these fusion receptors, we have shown that KDR is solely responsible for VPF/VEGF-induced human umbilical vein endothelial cell (HUVEC) proliferation and migration, whereas Flt-1 sh owed an inhibitory effect on KDR-mediated proliferation but not migration. To further characterize the VPF/VEGF-stimulated HUVEC proliferation and mig ration here, we have created several EGDR mutants by site-directed mutagene sis. We show that tyrosine residues 1059 and 951 of KDR are essential for V PF/VEGF-induced HUVEC proliferation and migration, respectively. Furthermor e, the mutation of tyrosine 1059 to phenylanaline results in the complete l oss of KDR/EGDR-mediated intracellular Ca2+ mobilization and MAPK phosphory lation, but the mutation of tyrosine 951 to phenylanaline did not affect th ese events. Our results suggest that KDR mediates different signaling pathw ays for HUVEC proliferation and migration and, moreover, intracellular Ca2 mobilization and MAPK phosphorylation are not essential for VPF/VEGF-induc ed HUVEC migration.