CXCR4

Domain

The amino-terminus is critical for ligand binding. Residues in all four extracellular regions contribute to HIV-1 coreceptor activity.

Function

Receptor for the C-X-C chemokine CXCL12/SDF-1 that transduces a signal by increasing intracellular calcium ion levels and enhancing MAPK1/MAPK3 activation (PubMed:10452968, PubMed:28978524, PubMed:18799424, PubMed:24912431). Involved in the AKT signaling cascade (PubMed:24912431). Plays a role in regulation of cell migration, e.g. during wound healing (PubMed:28978524). Acts as a receptor for extracellular ubiquitin; leading to enhanced intracellular calcium ions and reduced cellular cAMP levels (PubMed:20228059). Binds bacterial lipopolysaccharide (LPS) et mediates LPS-induced inflammatory response, including TNF secretion by monocytes (PubMed:11276205). Involved in hematopoiesis and in cardiac ventricular septum formation. Also plays an essential role in vascularization of the gastrointestinal tract, probably by regulating vascular branching and/or remodeling processes in endothelial cells. Involved in cerebellar development. In the CNS, could mediate hippocampal-neuron survival (By similarity).

(Microbial infection) Acts as a coreceptor (CD4 being the primary receptor) for human immunodeficiency virus-1/HIV-1 X4 isolates and as a primary receptor for some HIV-2 isolates. Promotes Env-mediated fusion of the virus (PubMed:8849450, PubMed:8929542, PubMed:9427609, PubMed:10074122, PubMed:10756055).

Involvement in disease

WHIM syndrome

WHIMS

Immunodeficiency disease characterized by neutropenia, hypogammaglobulinemia and extensive human papillomavirus (HPV) infection. Despite the peripheral neutropenia, bone marrow aspirates from affected individuals contain abundant mature myeloid cells, a condition termed myelokathexis.

None

The disease is caused by variants affecting the gene represented in this entry.

CXCR4 mutations play a role in the pathogenesis of Waldenstroem macroglobulinemia (WM) and influence disease presentation and outcome, as well as response to therapy. WM is a B-cell lymphoma characterized by accumulation of malignant lymphoplasmacytic cells in the bone marrow, lymph nodes and spleen, and hypersecretion of monoclonal immunoglobulin M (IgM). Excess IgM production results in serum hyperviscosity, tissue infiltration, and autoimmune-related pathology.

Post-translational modifications

Phosphorylated on agonist stimulation. Rapidly phosphorylated on serine and threonine residues in the C-terminal. Phosphorylation at Ser-324 and Ser-325 leads to recruitment of ITCH, ubiquitination and protein degradation.

Ubiquitinated after ligand binding, leading to its degradation (PubMed:28978524). Ubiquitinated by ITCH at the cell membrane on agonist stimulation. The ubiquitin-dependent mechanism, endosomal sorting complex required for transport (ESCRT), then targets CXCR4 for lysosomal degradation. This process is dependent also on prior Ser-/Thr-phosphorylation in the C-terminal of CXCR4. Also binding of ARRB1 to STAM negatively regulates CXCR4 sorting to lysosomes though modulating ubiquitination of SFR5S.

Sulfation on Tyr-21 is required for efficient binding of CXCL12/SDF-1alpha and promotes its dimerization. Tyr-7 and Tyr-12 are sulfated in a sequential manner after Tyr-21 is almost fully sulfated, with the binding affinity for CXCL12/SDF-1alpha increasing with the number of sulfotyrosines present. Sulfotyrosines Tyr-7 and Tyr-12 occupy clefts on opposing CXCL12 subunits, thus bridging the CXCL12 dimer interface and promoting CXCL12 dimerization.

O- and N-glycosylated. Asn-11 is the principal site of N-glycosylation. There appears to be very little or no glycosylation on Asn-176. N-glycosylation masks coreceptor function in both X4 and R5 laboratory-adapted and primary HIV-1 strains through inhibiting interaction with their Env glycoproteins. The O-glycosylation chondroitin sulfate attachment does not affect interaction with CXCL12/SDF-1alpha nor its coreceptor activity.

Sequence similarities

Belongs to the G-protein coupled receptor 1 family.

Tissue specificity

Expressed in numerous tissues, such as peripheral blood leukocytes, spleen, thymus, spinal cord, heart, placenta, lung, liver, skeletal muscle, kidney, pancreas, cerebellum, cerebral cortex and medulla (in microglia as well as in astrocytes), brain microvascular, coronary artery and umbilical cord endothelial cells. Isoform 1 is predominant in all tissues tested.

Cellular localization

• Cell membrane
• Multi-pass membrane protein
• Cell junction
• Early endosome
• Late endosome
• Lysosome
• In unstimulated cells, diffuse pattern on plasma membrane. On agonist stimulation, colocalizes with ITCH at the plasma membrane where it becomes ubiquitinated. In the presence of antigen, distributes to the immunological synapse forming at the T-cell-APC contact area, where it localizes at the peripheral and distal supramolecular activation cluster (SMAC).

Alternative names

• C-X-C chemokine receptor type 4
• CXC-R4
• CXCR-4
• FB22
• Fusin
• HM89
• LCR1
• Leukocyte-derived seven transmembrane domain receptor
• Lipopolysaccharide-associated protein 3
• NPYRL
• Stromal cell-derived factor 1 receptor
• LESTR
• LAP-3
• LPS-associated protein 3
• SDF-1 receptor
• CXCR4

Database links

• entrezGene:7852
• omim:162643
• swissprot:P61073

Target type

Proteins

Primary research area

Immuno-oncology

Other research areas

• Cardiovascular
• Immunology & Infectious Disease
• Oncology

Molecular weight

39746Da