Key points are not available for this paper at this time.
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 (VEGFR-2), both of which are selectively expressed on primary vascular endothelium. To dissect the respective signaling pathways and biological functions mediated by these receptors in primary endothelial cells with two receptors intact, we, recently developed chimeric receptors (EGDR and EGLT) in which the extracellular domain of the epidermal growth 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 showed an inhibitory effect on KDR-mediated proliferation but not migration. To further characterize the VPF/VEGF-stimulated HUVEC proliferation and migration here, we have created several EGDR mutants by site-directed mutagenesis. We show that tyrosine residues 1059 and 951 of KDR are essential for VPF/VEGF-induced HUVEC proliferation and migration, respectively. Furthermore, the mutation of tyrosine 1059 to phenylanaline results in the complete loss of KDR/EGDR-mediated intracellular Ca2+ mobilization and MAPK phosphorylation, but the mutation of tyrosine 951 to phenylanaline did not affect these events. Our results suggest that KDR mediates different signaling pathways for HUVEC proliferation and migration and, moreover, intracellular Ca2+ mobilization and MAPK phosphorylation are not essential for VPF/VEGF-induced HUVEC migration. 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 (VEGFR-2), both of which are selectively expressed on primary vascular endothelium. To dissect the respective signaling pathways and biological functions mediated by these receptors in primary endothelial cells with two receptors intact, we, recently developed chimeric receptors (EGDR and EGLT) in which the extracellular domain of the epidermal growth 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 showed an inhibitory effect on KDR-mediated proliferation but not migration. To further characterize the VPF/VEGF-stimulated HUVEC proliferation and migration here, we have created several EGDR mutants by site-directed mutagenesis. We show that tyrosine residues 1059 and 951 of KDR are essential for VPF/VEGF-induced HUVEC proliferation and migration, respectively. Furthermore, the mutation of tyrosine 1059 to phenylanaline results in the complete loss of KDR/EGDR-mediated intracellular Ca2+ mobilization and MAPK phosphorylation, but the mutation of tyrosine 951 to phenylanaline did not affect these events. Our results suggest that KDR mediates different signaling pathways for HUVEC proliferation and migration and, moreover, intracellular Ca2+ mobilization and MAPK phosphorylation are not essential for VPF/VEGF-induced HUVEC migration. vascular permeability factor vascular endothelial growth factor human umbilical vein endothelial cell epidermal growth factor endothelial cell mitogen-activated protein kinase bovine serum albumin phosphate-buffered saline fluorescence-activated cell sorter In order to grow beyond minimal size, tumors must generate a new vascular supply for the purpose of gas exchange, cell nutrition, and waste disposal (1Folkman J. Sci. Am. 1996; 275: 150-154Crossref PubMed Scopus (315) Google Scholar, 2Folkman J. N. Engl. J. Med. 1971; 285: 1182-1186Crossref PubMed Scopus (216) Google Scholar, 3Folkman J. Klagsburn M. Science. 1987; 235: 442-447Crossref PubMed Scopus (4006) Google Scholar, 4Folkman J. Watson K. Ingber D. Hanahan D. Nature. 1989; 339: 58-61Crossref PubMed Scopus (1765) Google Scholar). They do so by secreting angiogenic cytokines that induce the formation of new blood vessels (3Folkman J. Klagsburn M. Science. 1987; 235: 442-447Crossref PubMed Scopus (4006) Google Scholar, 4Folkman J. Watson K. Ingber D. Hanahan D. Nature. 1989; 339: 58-61Crossref PubMed Scopus (1765) Google Scholar, 5Dvorak H.F. Nagy J.A. Feng D. Brown L.F. Dvorak A.M. Curr. Top. Microbiol. Immunol. 1999; 237: 97-132Crossref PubMed Scopus (634) Google Scholar, 6Risau W. Nature. 1997; 386: 671-674Crossref PubMed Scopus (4750) Google Scholar). Tumor-secreted angiogenic cytokines include fibroblast growth factor, platelet-derived growth factor-B, and vascular permeability factor/vascular endothelial growth factor (VPF1/VEGF) (6Risau W. Nature. 1997; 386: 671-674Crossref PubMed Scopus (4750) Google Scholar, 7Benezra M. Vlodasky I. Ishai-Michaeli R. Neufeld G. Bar-Shavit R. Blood. 1993; 81: 3324-3331Crossref PubMed Google Scholar, 8Senger D.R. Galli S.J. Dvorak A.M. Perruzzi C.A. Harvey V.S. Dvorak H.F. Science. 1983; 219: 983-985Crossref PubMed Scopus (3360) Google Scholar, 9Vlodavsky I. Fuks Z. Ishai-Michaeli R. Bashkin P. Levi E. Korner G. Bar-Shavit R. Klagsbrun M. J. Cell. Biochem. 1991; 45: 167-176Crossref PubMed Scopus (238) Google Scholar). VPF/VEGF is likely the most important of these cytokines because it is expressed abundantly by a wide variety of human and animal tumors and because of its potency, selectivity for endothelial cells, and ability to regulate most, if not all, of the steps in the angiogenic cascade (5Dvorak H.F. Nagy J.A. Feng D. Brown L.F. Dvorak A.M. Curr. Top. Microbiol. Immunol. 1999; 237: 97-132Crossref PubMed Scopus (634) Google Scholar, 6Risau W. Nature. 1997; 386: 671-674Crossref PubMed Scopus (4750) Google Scholar,10Dvorak H.F. Prog. Clin. Biol. Res. 1990; 354A: 317-330PubMed Google Scholar, 11Dvorak H.F. Orenstein N.S. Carvalho A.C. Churchill W.H. Dvorak A.M. Galli S.J. Feder J. Bitzer A.M. Rypysc J. Giovinco P. J. Immunol. 1979; 122: 166-174PubMed Google Scholar, 12Dvorak H.F. Senger D.R. Dvorak A.M. Dev. Oncol. 1984; 22: 96-114Google Scholar, 13Ferrara N. Curr. Top. Microbiol. Immunol. 1999; 237: 1-30Crossref PubMed Scopus (505) Google Scholar). Moreover, a number of other angiogenic cytokines act, at least in part, by up-regulating VPF/VEGF expression (5Dvorak H.F. Nagy J.A. Feng D. Brown L.F. Dvorak A.M. Curr. Top. Microbiol. Immunol. 1999; 237: 97-132Crossref PubMed Scopus (634) Google Scholar, 14Seghezzi G. Patel S. Ren C.J. Gualandris A. Pintucci G. Robbins E.S. Shapiro R.L. Galloway A.C. Rifkin D.B. Mignatti P. J. Cell Biol. 1998; 141: 1659-1673Crossref PubMed Scopus (700) Google Scholar). VPF/VEGF extensively reprograms endothelial cell expression of proteases, integrins, and glucose transporters; stimulates endothelial cell migration and division; protects endothelial cells from apoptosis and senescence; and induces angiogenesis in both in vitro andin vivo models (for reviews, see Refs. 5Dvorak H.F. Nagy J.A. Feng D. Brown L.F. Dvorak A.M. Curr. Top. Microbiol. Immunol. 1999; 237: 97-132Crossref PubMed Scopus (634) Google Scholar, 6Risau W. Nature. 1997; 386: 671-674Crossref PubMed Scopus (4750) Google Scholar, 13Ferrara N. Curr. Top. Microbiol. Immunol. 1999; 237: 1-30Crossref PubMed Scopus (505) Google Scholar, 15Leung D.W. Cachianes G. Kuang W.J. Goeddel D.V. Ferrara N. Science. 1989; 246: 1306-1309Crossref PubMed Scopus (4395) Google Scholar). In addition, VPF/VEGF is the only angiogenic cytokine identified thus far that renders microvessels hyperpermeable to circulating macromolecules, a characteristic feature of angiogenic blood vessels (8Senger D.R. Galli S.J. Dvorak A.M. Perruzzi C.A. Harvey V.S. Dvorak H.F. Science. 1983; 219: 983-985Crossref PubMed Scopus (3360) Google Scholar, 10Dvorak H.F. Prog. Clin. Biol. Res. 1990; 354A: 317-330PubMed Google Scholar, 11Dvorak H.F. Orenstein N.S. Carvalho A.C. Churchill W.H. Dvorak A.M. Galli S.J. Feder J. Bitzer A.M. Rypysc J. Giovinco P. J. Immunol. 1979; 122: 166-174PubMed Google Scholar, 12Dvorak H.F. Senger D.R. Dvorak A.M. Dev. Oncol. 1984; 22: 96-114Google Scholar,16Senger D.R. Perruzzi C.A. Feder J. Dvorak H.F. Cancer Res. 1986; 46: 5629-5632PubMed Google Scholar). All of the VPF/VEGF activities are thought to be mediated by its interaction with two high affinity receptor tyrosine kinases, vascular endothelial growth factor receptor-2 (KDR, in human and Flk-1 in mice) and vascular endothelial growth factor receptor-1 (Flt-1), which are selectively expressed on the vascular endothelium. A third receptor, neuropilin, has been discovered recently but its function is not clear (17Gagnon M.L. Bielenberg D.R. Gechtman Z. Miao H.Q. Takashima S. Soker S. Klagsbrun M. Proc. Natl. Acad. Sci. U. S. A. 2000; 97: 2573-2578Crossref PubMed Scopus (248) Google Scholar, 18Soker S. Takashima S. Miao H.Q. Neufeld G. Klagsbrun M. Cell. 1998; 92: 735-745Abstract Full Text Full Text PDF PubMed Scopus (2048) Google Scholar). Both Flt-1 and KDR are essential for normal vascular development (19Fong G.H. Rossant J. Gertsenstein M. Breitman M.L. Nature. 1995; 376: 66-70Crossref PubMed Scopus (2184) Google Scholar, 20Shalaby F. Ho J. Stanford W.L. Fischer K.D. Schuh A.C. Schwartz L. Bernstein A. Rossant J. Cell. 1997; 89: 981-990Abstract Full Text Full Text PDF PubMed Scopus (736) Google Scholar). Flt-1 null mice do not survive beyond 8.5–9.5 days of gestation because of defective blood vessel formation that may cause increased numbers of endothelial progenitor cells (19Fong G.H. Rossant J. Gertsenstein M. Breitman M.L. Nature. 1995; 376: 66-70Crossref PubMed Scopus (2184) Google Scholar). Homozygous Flk-1/KDR knockout mice have different phenotypes that include impaired hematopoiesis and lack of differentiated endothelial cells (20Shalaby F. Ho J. Stanford W.L. Fischer K.D. Schuh A.C. Schwartz L. Bernstein A. Rossant J. Cell. 1997; 89: 981-990Abstract Full Text Full Text PDF PubMed Scopus (736) Google Scholar). Because both receptors are expressed on vascular endothelium, it has been difficult to define the respective roles of each in mediating the various signaling events and biological activities induced in the endothelium by VPF/VEGF. Current information, therefore, has been gleaned largely from: (a) studies with a cell line, porcine aortic endothelial cells, which do not express either receptor unless engineered to do so (21Joukov V. Sorsa T. Kumar V. Jeltsch M. Claesson-Welsh L. Cao Y. Saksela O. Kalkkinen N. Alitalo K. EMBO J. 1997; 16: 3898-3911Crossref PubMed Scopus (634) Google Scholar, 22Waltenberger J. Claesson-Welsh L. Siegbahn A. Shibuya M. Heldin C.H. J. Biol. Chem. 1994; 269: 26988-26995Abstract Full Text PDF PubMed Google Scholar); (b) studies with the placenta growth factor (PlGF), a ligand that binds Flt-1 but not KDR (23Petrova T.V. Makinen T. Alitalo K. Exp. Cell Res. 1999; 253: 117-130Crossref PubMed Scopus (238) Google Scholar); (c) the use of a Flt-1-specific antibody (24Kanno S. Oda N. Abe M. Terai Y. Ito M. Shitara K. Tabayashi K. Shibuya M. Sato Y. Oncogene. 2000; 19: 2138-2146Crossref PubMed Scopus (248) Google Scholar); (d) studies with antisense oligonucleotides that block Flt-1 expression (25Bernatchez P.N. Soker S. Sirois M.G. J. Biol. Chem. 1999; 274: 31047-31054Abstract Full Text Full Text PDF PubMed Scopus (237) Google Scholar); and (e) characterization of VPF/VEGF mutants that specifically bind Flt-1. To delineate the respective roles of KDR and Flt-1 in early passage endothelial cells in which both receptors remained intact and functional, we engineered two receptor chimeras (EGDR and EGLT) by fusing the extracellular domain of the EGF receptor (EGFR) with the transmembrane and intracellular domains of either KDR or Flt-1. These two receptor chimeras were overexpressed in early passages of human umbilical vein endothelial cells (HUVEC) with a retroviral vector (27Zeng H. Dvorak H.F. Mukhopadhyay D. J. Biol. Chem. 2001; 276: 26969-26979Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar). With this chimeric receptor system, we found results similar to others: KDR is responsible for VPF/VEGF-stimulated HUVEC proliferation and migration (21Joukov V. Sorsa T. Kumar V. Jeltsch M. Claesson-Welsh L. Cao Y. Saksela O. Kalkkinen N. Alitalo K. EMBO J. 1997; 16: 3898-3911Crossref PubMed Scopus (634) Google Scholar, 22Waltenberger J. Claesson-Welsh L. Siegbahn A. Shibuya M. Heldin C.H. J. Biol. Chem. 1994; 269: 26988-26995Abstract Full Text PDF PubMed Google Scholar). Furthermore, our results suggest that the downstream signaling pathway of VPF/VEGF-stimulated HUVEC proliferation was different from that of VPF/VEGF-stimulated HUVEC migration (27Zeng H. Dvorak H.F. Mukhopadhyay D. J. Biol. Chem. 2001; 276: 26969-26979Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar). In order to further characterize these different signaling pathways, we conducted the site-directed mutational analysis in the KDR chimera, EGDR. KDR possesses tyrosine kinase domains, tentative ATP-binding sites, and a long kinase-insert region. This kinase-insert region is known to contain several phosphorylation sites that show binding sites for different signaling molecules. At present, tyrosine residues 951, 996, 1054, and 1059 have been identified as autophosphorylation sites for KDR in a bacterial expression system (28Dougher-Vermazen M. Hulmes J.D. Bohlen P. Terman B.I. Biochem. Biophys. Res. Commun. 1994; 205: 728-738Crossref PubMed Scopus (108) Google Scholar). However, the importance of these tyrosine residues with respect to endothelial cell signaling is not yet well defined. In the present context, we show that the tyrosine residue 1059 of KDR is responsible for ligand-mediated intracellular Ca2+ mobilization, MAPK activation, and EC proliferation, whereas tyrosine residue 951 is required for EC migration. Recombinant VPF/VEGF was obtained from R 276: 26969-26979Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar). To the cells were at a of cells was with the CA). of the or of and of the of the that are required for by were in of EC of was to the at for of was to the and at for was to was was and for or at HUVEC were at a of cells of solution and of were to cells with was and the cells were for HUVEC were for and with different of EGF for various of as was by the of and the cells were with and with and Cell were for at of protein was with of different antibodies for and protein at for were with and were in for HUVEC with were with and with of solution trypsin and in at for were by and at for Cell were two with and were in the at cells in were to and were by at for were in of the of antibody or and at for were at for Cell were two with the in of the and at for were two and in of the analysis was in a with HUVEC were for with and with of solution trypsin and in at for were by and at for Cell were in of Ca2+ and and at the Cell were in of Ca2+ Fura-2 and F-127 and were at for were by at for and were in of Ca2+ for with Ca2+ were with the cells were in a plate with cells HUVEC were with of as cells were for and with VPF/VEGF or EGF for of was to each well and cells were with with for at with for at with and with of for at 3HThymidine was in are expressed as the of HUVEC were for with and with of solution trypsin and in at for were by and at for and with bovine were the with and the were a plate of the a of to cells well were in a plate for the were at for to the cells to and VPF/VEGF or EGF was at a of for an cells on the of the were with a was and in an well of the which the cells for the of was to each well cells or and the plate was at to cells were in a with are expressed as the of All were at least To further the different signaling pathways for KDR-mediated endothelial cell proliferation and migration, we created mutants in the by 951, 1054, and 1059 to 951 is in the kinase-insert and the are in the These mutants were and respectively. EGDR and these mutants were early passage HUVEC with a retroviral system, which we developed recently (27Zeng H. Dvorak H.F. Mukhopadhyay D. J. Biol. Chem. 2001; 276: 26969-26979Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar). HUVEC with or were and of were with antibody against the of EGFR by with antibody against the of similar of protein were we showed that EGF receptor be in HUVEC or HUVEC with as (27Zeng H. Dvorak H.F. Mukhopadhyay D. J. Biol. Chem. 2001; 276: 26969-26979Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar). In order to that the are expressed on the cell as receptors, we the HUVEC with EGDR or different mutants to analysis with antibody against the of EGFR and normal as shown in of HUVEC with EGDR or mutants expressed the receptors on the cell whereas EGFR was on HUVEC with we the phosphorylation of EGDR and these mutants in to EGF HUVEC with or were with EGF for different as were with antibody against the of EGFR by with A in to the EGDR receptor is and at which is well with the KDR phosphorylation in VPF/VEGF-stimulated HUVEC (27Zeng H. Dvorak H.F. Mukhopadhyay D. J. Biol. Chem. 2001; 276: 26969-26979Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar). phosphorylation of receptor be in HUVEC with the phosphorylation of is that of whereas that of is for a be at and not However, a similar phosphorylation as but the phosphorylation is at EGF different phosphorylation of these mutants were not to expression of these because similar protein were the was and with C-terminal antibody by the loss of receptor results that tyrosine residues 951 and 1059 of KDR are important for receptor phosphorylation in We further the of these EGDR mutants on HUVEC shown in in HUVEC with either or EGF similar in the HUVEC with or did not show growth to EGF to 100 However, HUVEC with different receptors or show a similar to VPF/VEGF that the lack of of is not to the of the Moreover, the of the proliferation of HUVEC VPF/VEGF and EGF is to the effect of Flt-1 on whereas EGF not function Flt-1 as (27Zeng H. Dvorak H.F. Mukhopadhyay D. J. Biol. Chem. 2001; 276: 26969-26979Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar). These that tyrosine residue 1059 is essential for HUVEC proliferation whereas the other two tyrosine residues do not have a This is the that that only tyrosine residue of KDR is for VPF/VEGF-induced EC To the tyrosine responsible for VPF/VEGF-induced HUVEC migration, we have similar to (27Zeng H. Dvorak H.F. Mukhopadhyay D. J. Biol. Chem. 2001; 276: 26969-26979Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar). shown in HUVEC show an of migration with either VPF/VEGF or EGF Both tyrosine residue and 1059 mutants did not show in the as with that of to the other the mutation of tyrosine 951 of KDR the to 100 induced in HUVEC with but effect on VPF/VEGF-stimulated migration. This is the that different tyrosine residues are required for KDR-mediated HUVEC proliferation and migration. we further the signaling pathways of HUVEC proliferation and migration. by several N. U. Claesson-Welsh L. J. Biol. Chem. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar, L. N. Y. Neufeld G. S. Shibuya M. Oncogene. 1995; Google MAPK phosphorylation is of HUVEC by VPF/VEGF. Furthermore, the MAPK kinase proliferation but not migration in VPF/VEGF-stimulated HUVEC and that MAPK phosphorylation is not required for migration (27Zeng H. Dvorak H.F. Mukhopadhyay D. J. Biol. Chem. 2001; 276: 26969-26979Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar). In order to the of the different tyrosine residues of KDR in MAPK activation, from HUVEC with and different receptor mutants were to analysis an we MAPK phosphorylation of HUVEC cells with In mutation of tyrosine residue 1059 of KDR showed MAPK in to EGF other two and a similar of MAPK to that of the receptor These that the tyrosine residue 1059 of KDR is essential for MAPK by VPF/VEGF. These our that MAPK is not required for HUVEC migration because MAPK but HUVEC migration as that of is well known that VPF/VEGF in EC an of Dvorak H.F. Senger D.R. Am. J. 1991; Google and we have shown that this Ca2+ mobilization is KDR or EGDR in to VPF/VEGF or (27Zeng H. Dvorak H.F. Mukhopadhyay D. J. Biol. Chem. 2001; 276: 26969-26979Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar). To define which tyrosine residue of KDR is responsible for we EGF of HUVEC that express different that is to intracellular Ca2+ mobilization in to EGF whereas the other two receptors to of the These results that tyrosine residue 1059 of KDR is essential for and suggest that signaling pathways to MAPK and intracellular may from the tyrosine Moreover, these suggest similar to MAPK activation, be essential for VPF/VEGF-induced EC proliferation but not migration. Because KDR has been shown to be and important for KDR function is a of W. A. Nature. 1994; PubMed Scopus Google Scholar). is well that KDR is responsible for VPF/VEGF-stimulated HUVEC proliferation and migration, but the residues responsible for these activities have not been defined. it was shown that tyrosine 951, 996, 1054, and 1059 of KDR are in a bacterial system that overexpressed the domain of KDR (28Dougher-Vermazen M. Hulmes J.D. Bohlen P. Terman B.I. Biochem. Biophys. Res. Commun. 1994; 205: 728-738Crossref PubMed Scopus (108) Google Scholar). Moreover, it was by and Terman M. Terman B.I. Oncogene. 1999; PubMed Scopus Google that tyrosine residues and 1059 were required for autophosphorylation of KDR in to VPF/VEGF the was overexpressed in However, the of these residues in endothelial cells was not well Furthermore, it was that was of overexpressed KDR in cells by the ligand M. Ito N. Claesson-Welsh L. Curr. Top. Microbiol. Immunol. 1999; 237: Google Scholar). we created mutants with 951, 1054, and 1059 to in the and expressed in HUVEC that expressed shown in of HUVEC with or expressed the receptors on the cell Our that the of receptor phosphorylation is in HUVEC with whereas the receptor phosphorylation is in HUVEC with These results well with the obtained from the bacterial system and from cells these our that 951 and 1059 are required for migration and proliferation, respectively. V. R. K. N. J. Chem. 2001; 276: Full Text Full Text PDF PubMed Scopus Google mutational analysis in the fusion They that mutation of and in loss of whereas the of and cell They that these tyrosine residues were sites for the of and these mutants effect on MAPK Our show that the its ability to not only proliferation but the MAPK phosphorylation in HUVEC with well with the that MAPK phosphorylation is required for cell these results may suggest that and are in mediating the other the tyrosine residues and be in cell cell proliferation, because of are to MAPK and, was shown to be required for VPF/VEGF-stimulated EC A. J. M. V. Ferrara N. J. Biol. Chem. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar). we showed that KDR/EGDR-mediated HUVEC proliferation, but not migration, and this inhibitory effect was at or KDR/EGDR-mediated intracellular Ca2+ mobilization (27Zeng H. Dvorak H.F. Mukhopadhyay D. J. Biol. Chem. 2001; 276: 26969-26979Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar). Furthermore, the VPF/VEGF-stimulated HUVEC and proliferation, but not migration (27Zeng H. Dvorak H.F. Mukhopadhyay D. J. Biol. Chem. 2001; 276: 26969-26979Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar). we show that intracellular Ca2+ mobilization and MAPK phosphorylation but not migration. which not migration, has effect on intracellular Ca2+ mobilization and MAPK these results suggest that intracellular Ca2+ mobilization and MAPK phosphorylation are not essential for KDR/EGDR-mediated HUVEC cell migration. Moreover, VPF/VEGF-stimulated HUVEC proliferation and migration are mediated by different downstream signaling This thus the site-directed analysis of function in early passage primary EC and has identified two tyrosine residues responsible for KDR-mediated proliferation and migration, respectively. However, of these two signaling pathways is as yet and further is to the complete of signaling steps and pathway We for and
Zeng et al. (Wed,) studied this question.