VEGF Receptor Subtypes KDR and FLT1 Show Different Sensitivities to Heparin and Placenta Growth Factor

Abstract

Vascular endothelial growth factor (VEGF) is an angiogenic growth factor which binds to two structurally related tyrosine kinase receptors denoted KDR and FLT1. To compare the interaction of VEGF with each receptor, cell lines which express individual receptor subtypes were identified using Northern blot hybridization. Bovine aortic endothelial (ABAE) cells and WM35 melanoma cells were found to express KDR, while FLT1 was primarily expressed on SK-MEL-37. Both receptor subtypes were detected on another melanoma cell line (WM9). Heparin augmented VEGF binding to KDR-expressing cells (ABAE and WM35), but inhibited VEGF binding to FLT1-expressing cells (SK-MEL-37 and WM9). The concentration of heparin required for half maximal stimulation of VEGF binding to KDR-expressing cells (500 ng/ml) was 25 times greater than that required for half maximal inhibition of binding to FLT1-expressing cells (20 ng/ml). In WM9 cells, the effect of heparin was bimodal; low concentration inhibited, while higher concentrations stimulated binding of 125I-VEGF. Placenta growth factor (PIGF-1) is a recently described growth factor structurally similar to VEGF. PIGF-1 had a negligible or no effect on 125I-VEGF binding to KDR-expressing cells (ABAE, WM35), but did complete for binding to FLT1-expressing cells (SK-MEL-37 and WM9). Addition of heparin had no effect on its ability to compete for binding with 125I-VEGF. The data indicate differential regulation of the two VEGF receptors by heparin and extended specificity of FLT1 receptor, but not KDR, for binding PIGF-1 growth factor.

VEGF165 requires extracellular matrix components to induce mitogenic effects and migratory response in breast cancer cells

“…Our results showed that the presence of heparin and ®bronectin increased the activity of all VEGF receptors. These results, reporting the most signi®cant increase in activity and presumably binding of VEGF to Flt-1 in the presence of heparin and ®bronectin, are di erent than those presented by Terman et al (1994). These di erences may represent the di erent experimental conditions and cell types used.…”

Expression of VEGF and pleiotrophin in deer antler

“…The cervine VEGF sequence was most similar to that of bovine. VEGF165 has a heparin-binding region on the carboxyl terminal region (Keck et al, 1997) and binding to KDR but not Flt-1 has been identified to have heparin as a mediator (Terman et al, 1994). It thus seems probable that heparin would play some role in mediating the effects of at least the VEGF165 splice variant in the antler.…”

Upregulation of the angiogenic factors PlGF, VEGF and their receptors (Flt-1, Flk-1/KDR) by TSH in cultured thyrocytes and in the thyroid gland of thiouracil-fed rats suggest a TSH-dependent paracrine mechanism for goiter hypervascularization

“…VEGF homodimers bind to and induce autophosphorylation of both the high anity Flt-1 (k d , 16 pM) and Flk-1/KDR (k d , 410 pM) (Shibuya et al, 1990;Terman et al, 1991;De Vries et al, 1992) tyrosine kinase receptors; conversely, PlGF homodimers bind only to the Flt-1 receptor (k d , 160 pM) (Kendall et al, 1994;Terman et al, 1994;Cao et al, 1996;Sawano et al, 1996). Puri®ed heterodimeric VEGF/PlGF has been shown to bind to the Flk-1/KDR receptor (Cao et al, 1996).…”