CXC chemokine receptors
Encyclopedia
CXC chemokine receptors are integral membrane protein
s that specifically bind and respond to cytokine
s of the CXC chemokine family. They represent one subfamily of chemokine receptor
s, a large family of G protein-linked receptors
that are known as seven transmembrane (7-TM) proteins since they span the cell membrane
seven times. There are currently seven known CXC chemokine receptors in mammals, named CXCR1 through CXCR7.
can both bind CXCR1 in humans, while all other ELR-positive chemokines, such as CXCL1
to CXCL7
bind only CXCR2. They are both expressed on the surface of neutrophils in mammals.
is predominantly expressed on T lymphocytes, and also on other lymphocytes (some B cells and NK cells) and is highly induced following cell activation. There are two isoforms, CXCR3-A and CXCR3-B. It has three highly related ligands in mammals, CXCL9
, CXCL10
and CXCL11
.
(also known as fusin) is the receptor for a chemokine known as CXCL12 (or SDF-1) and, as with CCR5, is utilized by HIV-1 to gain entry into target cells. This receptor has a wide cellular distribution, with expression on most immature and mature hematopoietic cell types (e.g. neutrophils, monocytes, T and B cells, dendritic cells, Langerhans cells and macrophages). In addition, CXCR4 can also be found on vascular endothelial cells and neuronal/nerve cells.
is selectively expressed on B cells and is involved in lymphocyte homing and the development of normal lymphoid tissue. Its principle ligand is CXCL13
(or BLC).
based on its chromosomal location (within the chemokine receptor cluster on human chromosome 3p21) and its similarity to other chemokine receptors in its gene
sequence. CXCR6 binds the ligand CXCL16
. Curiously, though, CXCR6 is structurally more closely related to CC chemokine receptors than to other CXC chemokine receptors
was originally called RDC-1 (an orphan receptor) but has since been shown to cause chemotaxis
in T lymphocytes in response to CXCL12 (the ligand for CXCR4) prompting the renaming of this molecule as CXCR7. There is no information publicly available to confirm whether this designation has been accepted by the IUIS/WHO Subcommittee on Chemokine Nomenclature at this time. This receptor has also been identified on memory B cells.
Integral membrane protein
An integral membrane protein is a protein molecule that is permanently attached to the biological membrane. Proteins that cross the membrane are surrounded by "annular" lipids, which are defined as lipids that are in direct contact with a membrane protein...
s that specifically bind and respond to cytokine
Cytokine
Cytokines are small cell-signaling protein molecules that are secreted by the glial cells of the nervous system and by numerous cells of the immune system and are a category of signaling molecules used extensively in intercellular communication...
s of the CXC chemokine family. They represent one subfamily of chemokine receptor
Chemokine receptor
Chemokine receptors are cytokine receptors found on the surface of certain cells, which interact with a type of cytokine called a chemokine. There have been 19 distinct chemokine receptors described in mammals...
s, a large family of G protein-linked receptors
G protein-coupled receptor
G protein-coupled receptors , also known as seven-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptor, and G protein-linked receptors , comprise a large protein family of transmembrane receptors that sense molecules outside the cell and activate inside signal...
that are known as seven transmembrane (7-TM) proteins since they span the cell membrane
Cell membrane
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
seven times. There are currently seven known CXC chemokine receptors in mammals, named CXCR1 through CXCR7.
CXCR1 and CXCR2
CXCR1 and CXCR2 are closely related receptors that recognize CXC chemokines that possess an E-L-R amino acid motif immediately adjacent to their CXC motif. CXCL8 (otherwise known as interleukin-8) and CXCL6CXCL6
Chemokine ligand 6 is a small cytokine belonging to the CXC chemokine family that is also known as granulocyte chemotactic protein 2 . As its former name suggests, CXCL6 is a chemoattractant for neutrophilic granulocytes. It elicits its chemotactic effects by interacting with the chemokine...
can both bind CXCR1 in humans, while all other ELR-positive chemokines, such as CXCL1
CXCL1
Chemokine ligand 1 is a small cytokine belonging to the CXC chemokine family that was previously called GRO1 oncogene, GROα, KC, Neutrophil-activating protein 3 and melanoma growth stimulating activity, alpha...
to CXCL7
CXCL7
Chemokine ligand 7 is a human gene.The encoded protein, Chemokine ligand is a small cytokine belonging to the CXC chemokine family. It is an isoform of Beta-Thromboglobulin or Pro-Platelet basic protein ....
bind only CXCR2. They are both expressed on the surface of neutrophils in mammals.
CXCR3
CXCR3CXCR3
Chemokine receptor CXCR3 is a Gαi protein-coupled receptor in the CXC chemokine receptor family. Other names for CXCR3 are G protein-coupled receptor 9 and CD183...
is predominantly expressed on T lymphocytes, and also on other lymphocytes (some B cells and NK cells) and is highly induced following cell activation. There are two isoforms, CXCR3-A and CXCR3-B. It has three highly related ligands in mammals, CXCL9
CXCL9
Chemokine ligand 9 is a small cytokine belonging to the CXC chemokine family that is also known as Monokine induced by gamma interferon . CXCL9 is a T-cell chemoattractant, which is induced by IFN-γ. It is closely related to two other CXC chemokines called CXCL10 and CXCL11, whose genes are...
, CXCL10
CXCL10
C-X-C motif chemokine 10 also known as Interferon gamma-induced protein 10 or small-inducible cytokine B10 is an 8.7 kDa protein that in humans is encoded by the CXCL10 gene...
and CXCL11
CXCL11
Chemokine ligand 11 is a small cytokine belonging to the CXC chemokine family that is also called Interferon-inducible T-cell alpha chemoattractant and Interferon-gamma-inducible protein 9...
.
CXCR4
CXCR4CXCR4
C-X-C chemokine receptor type 4 also known as fusin or CD184 is a protein that in humans is encoded by the CXCR4 gene.- Function :...
(also known as fusin) is the receptor for a chemokine known as CXCL12 (or SDF-1) and, as with CCR5, is utilized by HIV-1 to gain entry into target cells. This receptor has a wide cellular distribution, with expression on most immature and mature hematopoietic cell types (e.g. neutrophils, monocytes, T and B cells, dendritic cells, Langerhans cells and macrophages). In addition, CXCR4 can also be found on vascular endothelial cells and neuronal/nerve cells.
CXCR5
The chemokine receptor CXCR5CXCR5
C-X-C chemokine receptor type 5 also known as Burkitt lymphoma receptor 1 is a G protein-coupled seven transmembrane receptor for chemokine CXCL13 and belongs to the CXC chemokine receptor family...
is selectively expressed on B cells and is involved in lymphocyte homing and the development of normal lymphoid tissue. Its principle ligand is CXCL13
CXCL13
C-X-C motif chemokine 13 also known as B lymphocyte chemoattractant is a protein that in humans is encoded by the CXCL13 gene.- Function :CXCL13 is a small cytokine belonging to the CXC chemokine family...
(or BLC).
CXCR6
Was formerly called three different names (STRL33, BONZO, and TYMSTR) before being assigned CXCR6CXCR6
C-X-C chemokine receptor type 6 is a protein that in humans is encoded by the CXCR6 gene.CXCR6 has also recently been designated CD186 .-Further reading:...
based on its chromosomal location (within the chemokine receptor cluster on human chromosome 3p21) and its similarity to other chemokine receptors in its gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
sequence. CXCR6 binds the ligand CXCL16
CXCL16
Chemokine ligand 16 is a small cytokine belonging to the CXC chemokine family. Larger than other chemokines , CXCL16 is composed of a CXC chemokine domain, a mucin-like stalk, a transmembrane domain and a cytoplasmic tail containing a potential tyrosine phosphorylation site that may bind SH2...
. Curiously, though, CXCR6 is structurally more closely related to CC chemokine receptors than to other CXC chemokine receptors
CXCR7
CXCR7CXCR7
C-X-C chemokine receptor type 7 is a protein that in humans is encoded by the CXCR7 gene.This gene encodes a member of the G-protein coupled receptor family. This protein was earlier thought to be a receptor for vasoactive intestinal peptide and was considered to be an orphan receptor...
was originally called RDC-1 (an orphan receptor) but has since been shown to cause chemotaxis
Chemotaxis
Chemotaxis is the phenomenon in which somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. This is important for bacteria to find food by swimming towards the highest concentration of food molecules,...
in T lymphocytes in response to CXCL12 (the ligand for CXCR4) prompting the renaming of this molecule as CXCR7. There is no information publicly available to confirm whether this designation has been accepted by the IUIS/WHO Subcommittee on Chemokine Nomenclature at this time. This receptor has also been identified on memory B cells.