Figure 2 - Interplay of growth factor-receptor signals and cell adhesion receptors. The figure depicts an endothelial cell in the center, expressing various integrins (whose major ligands are noted), which are implicated in one or more aspects of vasculogenesis or angiogenesis (see text) and receptors for basic fibroblast growth factor (FGF-2), vascular endothelial growth factor (VEGF), and angiopoietins. The latter are produced by various cells in the vicinity of developing vessels and those cells in turn receive stimulation by factors secreted by the endothelial cells (e.g., platelet-derived growth factor (PDGF) and neuregulin) that act on receptors on the accessory cells. The latter cells also express and use integrins (data not shown). Thus, there is a two-way "conversation" between endothelial cells and their neighbors and adhesion events involving either or both. Also shown are interactions involving eph/ephrin family members, the Notch pathway and cadherins (see text). At the bottom are shown various cell biological events which must be appropriately controlled to yield vessels of different types. The challenge is to define the interplay among the various receptors and ligands and the contributions made by each to the cell biology of vasculogenesis and angiogenesis.