CXCL12/SDF-1 alpha

SDF-1 alpha (Stromal Cell-Derived Factor-1α, SDF-1α) is a member of the chemokine α subfamily that lack the ELR domain. SDF-1α works as a chemoattractant for T- and B-lymphocytes and monocytes. SDF-1α is a ligand for CXCR4. The SDF-1α/CXCR4 signaling mediates many physiological processes including cell trafficking, angiogenesis, embryogenesis, tumor invasion and metastatic. It also controls the chemotaxis of hematopoietic stem cells homing to the bone marrow. SDF-1, an important member of the chemokine family, is expressed in two subtypes, SDF-1α and SDF-1β, with SDF-1α being the main subtype. SDF-1α is widely present in many tissues and organs of the human body, such as the lymph nodes, bone marrow, liver, lung, muscle, small intestine, kidney, and brain, and can sustainably exist in these organs and tissues. Studies have shown that SDF-1α plays an important role in the physiological mfunctions of migration, distribution, development, differentiation, and apoptosis of various cells. Moreover, SDF-1α plays a key role in the pathological process of some diseases, such as inflammation, tumor formation and metastasis, pathogen infection, and wound repair^[1][3].
SDF-1 has three isoforms, α, β, and γ, which are different at the splicing level, not at the transcriptional level. The analysis of the genomic structure of SDF-1 in human and mouse revealed two isoforms, SDF-1α and SDF-1β, which are encoded by a single gene and result from alternative splicing. SDF-1α comprises 3 exons and encodes a protein of 89 amino acids whereas SDF-1β consists of 4 exons and encodes a protein of 93 amino acids. Both isoforms are highly similar regarding their sequences with the only difference of 4 additional amino acids at the C-terminus of SDF1β. In adult rat brain, SDF-1α is the predominant one, present in astrocytes, microglia, as well as in neurons. SDF-1α is found positive in normal cholinergic neurons, such as in the medial septum and substantia innominata, and in dopaminergic neurons, such as in the substantia nigra (SN) pars compacta and the ventral tegmental area. SDF-1α is the only known ligand for CXCR4. CXCR4 is also a target for human immunodeficiency virus (HIV) binding^[1][2].

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