Roeckl W, Hecht D, Sztajer H, Waltenberger J, Yayon A, Weich H A
Department of Gene Regulation, GBF, Braunschweig, Germany.
Exp Cell Res. 1998 May 25;241(1):161-70. doi: 10.1006/excr.1998.4039.
The FLT-1 and KDR genes encode transmembrane tyrosine kinases which function as high-affinity receptors for vascular endothelial growth factor (VEGF). We have used the baculovirus system to express the extracellular parts of the FLT-1 receptor and KDR receptor in soluble form (sFLT-1 and sKDR), for in vitro binding and competition assays. Here, we show that the binding of VEGF165 to sKDR but not sFLT-1 is dependent on heparin, regardless of whether VEGF165 or sKDR is immobilized. Further, only sFLT-1 acts as a receptor antagonist in solution and sKDR can neither compete with the binding of VEGF165 to human endothelial cells carrying both receptors nor block VEGF165 induced mitogenicity. Soluble KDR only partially inhibits cell migration even at high concentrations, in contrast to sFLT which can almost completely block (82%) VEGF-induced cell proliferation and migration. Taken together these results show that the two soluble VEGF receptor proteins, sFLT-1 and sKDR, despite binding the same ligand, behave very differently when immobilized with regard to their dependence on heparin for VEGF binding. In solution their respective ability to function as receptor antagonists is also strikingly different, possibly a reflection of their different dependency on heparin.
FLT-1和KDR基因编码跨膜酪氨酸激酶，其作为血管内皮生长因子（VEGF）的高亲和力受体发挥作用。我们已利用杆状病毒系统以可溶性形式（sFLT-1和sKDR）表达FLT-1受体和KDR受体的胞外部分，用于体外结合和竞争分析。在此，我们表明，无论VEGF165还是sKDR被固定，VEGF165与sKDR而非sFLT-1的结合都依赖于肝素。此外，只有sFLT-1在溶液中作为受体拮抗剂起作用，而sKDR既不能与VEGF165与携带这两种受体的人内皮细胞的结合竞争，也不能阻断VEGF165诱导的有丝分裂活性。可溶性KDR即使在高浓度下也只能部分抑制细胞迁移，相比之下，sFLT几乎可以完全阻断（82%）VEGF诱导的细胞增殖和迁移。综上所述，这些结果表明，两种可溶性VEGF受体蛋白sFLT-1和sKDR，尽管结合相同的配体，但在固定时，它们对VEGF结合的肝素依赖性表现非常不同。在溶液中，它们各自作为受体拮抗剂的功能能力也存在显著差异，这可能反映了它们对肝素的不同依赖性。
