Figure 1.

Chemokine receptor 4 (CXCR 4)–mediated signaling pathway. Stromal-derived factor-1 binding activates the G-protein-coupled receptor CXCR 4. Gai protein–mediated signaling involves various downstream pathways activation of calcium efflux, protein kinase C (PKC), and phosphoinositide 3-kinase (PI3K)/AKT pathway. PKC and PI3K are capable of phosphorylation of important focal adhesion components (Pyk-2, p130Cas, paxillin) regulating (i) cell migration and (ii) chemotaxis of stem cells. Signaling through the PI3K-AKT mediates (iii) cell proliferation and (iv) cell survival.