CXCR7

• OMIM: 610 376
• UniProt: P25106

CXCR7 (short for CXC motif chemokine receptor - 7) is a receptor protein of the family of chemokine receptors, which occurs on the cell membrane of various cells of the hematopoietic system, such as monocytes, basophils and B lymphocytes. Although he can be phylogenetically and structurally due to its seven the cell membrane spanning helices assigned to the G- protein -coupled receptor, it is not capable of directly to signal transduction via G proteins. Activation of the receptor by the chemokines CXCL11 and CXCL12 is associated with growth and metastasis of various tumors.

Occurrence

Within the hematopoietic system CXCR7 can be demonstrated in particular monocytes, basophils and B lymphocytes. Different levels of expression can be detected in different populations of dendritic cells and T lymphocytes. And laboratory cell lines, such as CHO cells and HEK293 cells expressing CXCR7.

Biochemistry

Structure

CXCR7 is a transmembrane protein is selected from the group of G protein- coupled receptor encoded by a gene on the chromosome 2 gene locus Q37. The gene is located in a cluster of chromosome 2, which also contains the genes of other chemokine receptors such as CXCR1, CXCR2 and CXCR4 are located. In its amino acid sequence CXCR7 is related to these receptors and shows about 40% sequence identity to CXCR2. A characteristic of G protein- coupled receptors, heptahelical structure is adopted.

Receptor activation and signal transduction

CXCR7 is a G - protein - coupled receptor that selectively bind to the chemokines CXCL11 and CXCL12 as endogenous ligands. As a consequence of ligand binding may not have a direct activation of G - proteins is observed. Therefore, CXCR7 is similar to the chemokine receptors D6 and DARC viewed as a scavenger for chemokines. Regardless of a CXCR7 -mediated induction of cell adhesion and chemotaxis could be observed in some model systems. These effects are associated with an activation of alternative signaling pathways involving β -arrestin and the protein kinase B. In addition, a modulation of signal transduction pathways could by interaction with the chemokine receptor CXCR4 are shown.

Function

The physiological role of CXCR7 in the organism is controversial. Thanks to the absence of activation of classical signal transduction G- protein -coupled receptors as a function of chemokine or chemokine scavengers memory is assumed. Regardless, CXCR7 involved in organogenesis.

The expression of CXCR7 on tumor cells suggest a possible role of the receptor in tumorigenesis. In animal studies the promotion of tumor growth and metastasis could be detected. Like other chemokine receptors, such as CCR5 and CXCR4 in particular, can serve CXCR7 for some HIV strains in addition to CD4 and co-receptor for entry into the cell.