Multiple mechanisms for exogenous heparin modulation of vascular endothelial growth factor activity.
Heparin and heparin-like molecules are known to modulate the cellular responses to vascular endothelial growth factor-A (VEGF-A). In this study, we investigated the likely mechanisms for heparin's influence on the biological activity of VEGF-A. Previous studies have shown that exogenous heparin's effects on the biological activity of VEGF-A are many and varied, in part due to the endogenous cell-surface heparan sulfates. To circumvent this problem, we used mutant endothelial cells lacking cell-surface heparan sulfates. We showed that VEGF-induced cellular responses are dependent in part on the presence of the heparan sulfates, and that exogenous heparin significantly augments VEGF's cellular effects especially when endogenous heparan sulfates are absent. Exogenous heparin was also found to play a cross-bridging role between VEGF-A(165) and putative heparin-binding sites within its cognate receptor, VEGFR2 when they were examined in isolation. The cross-bridging appears to be more dependent on molecular weight than on a specific heparin structure. This was confirmed by surface plasmon resonance binding studies using sugar chips immobilized with defined oligosaccharide structures, which showed that VEGF-A(165) binds to a relatively broad range of sulfated glycosaminoglycan structures. Finally, studies of the far-UV circular dichroism spectra of VEGF-A(165) showed that heparin can also modulate the conformation and secondary structure of the protein.
Wijelath
Errol
E
Department of Surgery, Division of Vascular Surgery, VA Puget Sound Health Care System and University of Washington School of Medicine, Seattle, Washington 98108, USA. errolw@u.washington.edu
Namekata
Mayumi
M
Murray
Jacqueline
J
Furuyashiki
Mai
M
Zhang
Siyuan
S
Coan
Daniel
D
Wakao
Masahiro
M
Harris
Robert B
RB
Suda
Yasuo
Y
Wang
Lianchun
L
Sobel
Michael
M
D000818:Animals; D001665:Binding Sites; D042783:Endothelial Cells / Q000378:metabolism*; D006025:Glycosaminoglycans; D006493:Heparin / Q000494:pharmacology*; D006497:Heparan Sulfate; D006801:Humans; D008970:Molecular Weight; D011487:Protein Conformation / Q000187:drug effects; D020349:Surface Plasmon Resonance; D042461:Vascular Endothelial Growth Factor A / Q000187:drug effects* / Q000378:metabolism; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism
D006025:Glycosaminoglycans; D006493:Heparin; D006497:Heparan Sulfate; D042461:Vascular Endothelial Growth Factor A; D040301:Vascular Endothelial Growth Factor Receptor-2; C013786:A73025