The fourth immunoglobulin-like loop in the extracellular domain of FLT-1, a VEGF receptor, includes a major heparin-binding site.
We found that heparin at low concentrations increases the vascular endothelial growth factor (VEGF)-induced proliferation of human umbilical vein endothelial cells (HUVECs) but at high concentrations decreases it. To examine whether FLT-1, a VEGF receptor, interacts with heparin and which domain of FLT-1 binds to heparin, various extracellular domains of FLT-1 were expressed in a baculovirus/insect cell system: sFLT-1(1-7), sFLT-1(1-4), sFLT-1(1-3), and sFLT-1(1-2) containing immunoglobulin (Ig)-like loop one to seven, one to four, one to three, and one to two, respectively. The sFLT-1(1-7) and sFLT-1(1-4) readily bound heparin at the physiological salt concentration and half-dissociated from heparin at 0.65 M and 0.57 M NaCl, respectively. In contrast, the sFLT-1(1-3) and sFLT-1(1-2) poorly bound heparin at the physiological salt concentration. In addition, the interaction of sFLT-1(1-7) with heparin was not affected by EDTA up to 80 mM. We thus concluded that the fourth Ig-like loop of FLT-1 is a major heparin-binding site and divalent cations are not involved in the interaction of FLT-1 and heparin.
Park
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M
College of Science, Yonsei University, Seoul, 120-749, Korea.
Lee
S T
ST
D001665:Binding Sites; D002478:Cells, Cultured; D016228:Endothelial Growth Factors / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000378:metabolism*; D006493:Heparin / Q000378:metabolism*; D006801:Humans; D007136:Immunoglobulins / Q000737:chemistry / Q000378:metabolism; D008222:Lymphokines / Q000378:metabolism*; D020794:Receptor Protein-Tyrosine Kinases / Q000737:chemistry* / Q000378:metabolism; D017978:Receptors, Growth Factor / Q000737:chemistry* / Q000378:metabolism; D040262:Receptors, Vascular Endothelial Growth Factor; D015398:Signal Transduction; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D016228:Endothelial Growth Factors; D007136:Immunoglobulins; D008222:Lymphokines; D017978:Receptors, Growth Factor; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D006493:Heparin; D020794:Receptor Protein-Tyrosine Kinases; D040262:Receptors, Vascular Endothelial Growth Factor