Figure 1.

VEGF-A-mediated vascular sprouting. VEGFR-2 is expressed on endothelial cells (shown in gray) including proliferating cells, where it binds VEGF-A, which then induces sprouting. One form of VEGFR-1 is expressed on mature endothelial cells, while another form is secreted (sVEGFR-1). Both forms of VEGFR-1 bind VEGF-A, hence preventing the binding of VEGF-A to VEGFR-2 on non-sprouting parts of the blood vessel (decoy function). This is important to guide the growing vessel in the right direction and prevent the sprouting of neighboring cells.