FUNCTIONS OF THE VEGF RECEPTOR-1 (FLT-1) IN THE VASCULATURE

Vascular endothelial growth factor (VEGF) is a major inducer of angiog enesis and vasculogenesis. Two distinct receptors for VEGF; the tyrosi ne kinase receptors VEGFR-1 (Flt-1) and VEGFR-2 (Flk-1/KDR), have been identified. Transfection studies could demonstrate biological activit ies for the Flk-1/KDR-, but not for the Flt-1-receptor, which led to t he hypothesis that Flt-1 is a decoy receptor for VEGF. However, Flt-1 is biologically active in non-endothelial cells, namely monocytes, whi ch exclusively express this receptor. In addition, the Flt-1 ligand pl acenta growth factor (PlGF), which is unable to bind and activate Flk- 1/KDR, elicits activities in both monocytes and endothelial cells. The implications of Flt-1 mediated monocyte transmigration through endoth elial monolayers and induction Of the procoagulant tissue factor on mo nocytes for the field of vascular medicine ave discussed. (C) 1998, El sevier Science Inc.