SDF-1beta (CXCL12) (SDF1B) Active Protein

This gene encodes a member of the alpha chemokine protein family. The encoded protein is secreted and functions as the ligand for the G-protein coupled receptor, chemokine (C-X-C motif) receptor 4. The encoded protein plays a role in many diverse cellular functions, including embryogenesis, immune surveillance, inflammation response, tissue homeostasis, and tumor growth and metastasis. Alternative splicing results in multiple transcript variants. [provided by RefSeq, May 2013]

CXCL12 iso3: Chemoattractant active on T-lymphocytes, monocytes, but not neutrophils. Activates the C-X-C chemokine receptor CXCR4 to induce a rapid and transient rise in the level of intracellular calcium ions and chemotaxis. Also binds to another C-X-C chemokine receptor CXCR7, which activates the beta-arrestin pathway and acts as a scavenger receptor for SDF-1. SDF-1-beta(3-72) and SDF-1- alpha(3-67) show a reduced chemotactic activity. Binding to cell surface proteoglycans seems to inhibit formation of SDF-1-alpha(3- 67) and thus to preserve activity on local sites. Acts as a positive regulator of monocyte migration and a negative regulator of monocyte adhesion via the LYN kinase. Stimulates migration of monocytes and T-lymphocytes through its receptors, CXCR4 and CXCR7, and decreases monocyte adherence to surfaces coated with ICAM-1, a ligand for beta-2 integrins. SDF1A/CXCR4 signaling axis inhibits beta-2 integrin LFA-1 mediated adhesion of monocytes to ICAM-1 through LYN kinase. Inhibits CXCR4-mediated infection by T- cell line-adapted HIV-1. Plays a protective role after myocardial infarction. Induces down-regulation and internalization of CXCR7 expressed in various cells. Has several critical functions during embryonic development; required for B-cell lymphopoiesis, myelopoiesis in bone marrow and heart ventricular septum formation. Monomer or homodimer; in equilibrium. Dimer formation is induced by non acidic pH and the presence of multivalent anions, and by binding to CXCR4 or heparin. Monomeric form is required for full chemotactic activity and resistance to ischemia/reperfusion injury, whereas the dimeric form acts as a partial agonist of CXCR4, stimulating Ca2+ mobilization but with no chemotactic activity and instead acts as a selective antagonist that blocks chemotaxis induced by the monomeric form. Interacts with the N- terminus of CXCR7. Isoform Alpha and isoform Beta are ubiquitously expressed, with highest levels detected in liver, pancreas and spleen. Isoform Gamma is mainly expressed in heart, with weak expression detected in several other tissues. Isoform Delta, isoform Epsilon and isoform Theta have highest expression levels in pancreas, with lower levels detected in heart, kidney, liver and spleen. Belongs to the intercrine alpha (chemokine CxC) family. 6 isoforms of the human protein are produced by alternative splicing.

Protein type: Motility/polarity/chemotaxis; Cell development/differentiation; Secreted, signal peptide; Secreted; Chemokine

Cellular Component: extracellular space; plasma membrane; extracellular region; external side of plasma membrane

Molecular Function: growth factor activity; chemokine receptor binding; chemokine activity; CXCR chemokine receptor binding; cytokine activity

Biological Process: positive regulation of dopamine secretion; organ regeneration; positive regulation of cell adhesion; adult locomotory behavior; neuron migration; motor axon guidance; regulation of calcium ion transport; chemotaxis; regulation of cell migration; germ cell development; induction of positive chemotaxis; T cell proliferation; patterning of blood vessels; ameboidal cell migration; germ cell migration; positive regulation of cell proliferation; positive regulation of axon extension involved in axon guidance; immune response; positive regulation of endothelial cell proliferation; brain development; positive regulation of neuron differentiation; positive regulation of cell migration; telencephalon cell migration