CXCR4 as an example of chemokine receptor signaling. Stromal cell derived factor-1 (SDF-1) interacts with CXCR4. Binding of SDF-1 (CXCL12) to CXCR4 activates Gαi (pertussis toxin-sensitive) signaling pathways through which reduces cAMP signaling molecules in cells, and leads to phosphatidylinositol 3-kinase (PI3K)/Akt and Ras/MAPK signaling pathways. These signaling pathways include locomotion, chemotaxis, homing, adhesion, invasion and angiogenesis in lymphocytes, macrophages, neutrophils, hematopoietic stem cells, and cancerous cells.