CXCR4

CXCR4 is a G protein-coupled chemokine receptor that mediates migration of resting leukocytes and hematopoietic progenitors in response to SDF-1/CXCL12^[1]. Mechanistically, CXCR4-CXCL12 signaling supports hematopoiesis and cerebellar development, and CXCR4-deficient mice show hematopoietic and cardiac defects matching SDF-1-deficient mice^[1]. In vascular development, mice lacking CXCR4 or PBSF/SDF-1 show defective formation of large vessels supplying the gastrointestinal tract, identifying this axis as a signaling system for organ vascularization^[2]. In disease models, CXCR4 and CCR7 are highly expressed in human breast cancer cells, malignant breast tumors, and metastases, linking chemokine receptor programs to tumor cell migration and metastatic spread^[3]. Compared with the related ACKR3/CXCR7 receptor, CXCR4 couples to G proteins and directly promotes cell migration, whereas ACKR3 is G protein-independent and scavenges CXCL12 to regulate extracellular chemokine levels^[4]. For experimental applications, CXCR4 antagonist structures with IT1t and CVX15 define ligand-binding sites near the extracellular surface, supporting structure-guided inhibitor design^[5]. AMD3100 selectively antagonizes CXCR4 and rapidly mobilizes murine and human hematopoietic progenitor cells, especially with G-CSF^[6].