CD31 (Platelet Endothelial Cell Adhesion Molecule-1: PECAM-1), a member of the Ig superfamily of cell adhesion molecules, is expressed by circulating platelets, monocytes, neutrophils, some T cells, and endothelial cells and modulates cell adhesion, endothelial cell migration, and angiogenesis. CD31 is phosphorylated on Tyr686 at the cytoplasmic carboxy-terminal tail upon various stimuli (e.g. mechanical or oxidative stress), presumably by Src family members. The tyrosine phosphorylation mediates associations with a number of SH2 domain-containing binding partners such as PI3 kinase, SHIP, PLC?, and SHP-2. Thus, CD31 serves as a scaffold for various signaling molecules.