Background：C-X-C chemokine receptor type 4 (CXCR4) is a widely expressed G protein-coupled seven-transmembrane receptor. CXCL12/SDF-1 is the biological ligand for CXCR4. The binding of CXCL12 to CXCR4 induces intracellular signaling through several divergent pathways initiating signals related to chemotaxis, cell survival and/or proliferation, increase in intracellular calcium, and gene transcription (PMID: 20484021). CXCR4 also functions as a coreceptor for HIV-1 entry (PMID: 9427609). CXCR4 has a calculated molecular weight of 40 kDa. In addition to the predicted species of 45-47 kDa for glycosylated CXCR4 monomers, due to ubiquitination, dimeration, and different degrees of glycosylation, additional species can also exist and have been reported in some researches, including 67 kDa (PMID: 23917520), 55, 67, 87 kDa (PMID: 20028517), 80 kDa (PMID: 10506573), 47, 50, 62, and 98 kDa (PMID: 16204649).
