Description
Background: Integrins are heterodimeric cell surface receptors that play a pivotal role in cell adhesion and migration, as well as in growth and survival (1,2). The integrin family contains at least 18 alpha and 8 beta subunits that form 24 known integrins with distinct tissue distribution and overlaping ligand specificities (3). Integrins not only transmit signals to cells in response to the extracellular environment (outside-in signaling), but also sense intracellular cues to alter their interaction with the extracellular environment (inside-out signaling) (1,2). alphaIIbeta3 and alphaVbeta3 are the two beta3 containing integrins which are prominently expressed in hematopoietic cells and angiogenic endothelic cells and perform adhesive functions in hemostasis, wound healing and angiogenesis (1,4). Tyr773 and Tyr785 (usually referred to as Tyr747 and Tyr759 based on the chicken sequence) are phosphorylated upon ligand binding (5). Phosphorylation of these tyrosine residues is required for certain ligand-induced signaling (6). Thr779 (corresponding to Thr753 of the chicken sequence) of integrin beta3 in the platelet specific alphaIIbeta3 is phosphorylated by PKD and/or Akt, which may modulate integrin association with other signaling molecules (7)