CX3CR1
Description
The CX3CR1 (C-X3-C motif chemokine receptor 1) is a protein-coding gene located on chromosome 3.
CX3C motif chemokine receptor 1 (CX3CR1), also known as the fractalkine receptor or G-protein coupled receptor 13 (GPR13), is a transmembrane protein of the G protein-coupled receptor 1 (GPCR1) family and the only known member of the CX3C chemokine receptor subfamily. As the name suggests, this receptor binds the inflammatory chemokine CX3CL1 (also called neurotactin in mice or fractalkine in humans). This endogenous ligand solely binds to CX3CR1 receptor. Interaction of CX3CR1 with CX3CL1 can mediate migration, adhesion and retention of leukocytes, because Fractalkine exists as membrane-anchored protein (mCX3CL1) as well as cleaved soluble molecule (sCX3CL1) due to proteolysis by metalloproteinases (MPPs). The shedded form carries out typical function of conventional chemokines, the chemotaxis, while the membrane-bound protein behaves as adhesion molecule for facilitation of diapedesis. Both partners of CX3CL1-CX3CR1 axis are present on numerous cell types from hematopoietic and nonhematopoietic cells throughout the body. Moreover, their distinct cell expression is dependent on specific tissues and organs, which provides broad sphere of biological activity. Hence, considering their various functional activity, they are also linked with multiple neurodegenerative and inflammatory disorders as well as with tumorigenesis.
== Genetics == The coding gene for CX3CR1 is now officially called identically to its protein: CX3CR1 gene, but may be still referred to by other older names such as V28; CCRL1; GPR13; CMKDR1; GPRV28; CMKBRL1. A genome location of the gene in humans is on the short arm of the chromosome 3p22.2.
CX3CR1 is a receptor for the chemokine CX3CL1, also known as fractalkine. It is expressed on many early leukocyte cells and plays a role in various biological processes. CX3CR1-CX3CL1 signaling is involved in immune responses, inflammation, cell adhesion, and chemotaxis. It mediates cell migration, recruits natural killer cells to inflamed tissues, regulates inflammation in atherogenesis, and promotes cell survival in atherosclerotic plaques. CX3CR1 also plays a role in airway inflammation, promoting the survival of interleukin 2-producing T helper cells. It is involved in the migration of circulating monocytes to non-inflamed tissues, where they differentiate into macrophages and dendritic cells. CX3CR1 acts as a negative regulator of angiogenesis by promoting macrophage chemotaxis. In the brain, it regulates inflammatory responses in the central nervous system (CNS), regulates synapse maturation, and is involved in brain development through synaptic pruning. CX3CR1 is also an important regulator of the gut microbiota, controlling immunity to intestinal bacteria and fungi. It is expressed in lamina propria dendritic cells in the small intestine, where it takes up bacteria to provide defense against pathogenic bacteria. CX3CR1 is required to initiate innate and adaptive immune responses against the dissemination of commensal fungi. It also acts as a receptor for the chemokine CCL26, inducing cell chemotaxis. CX3CR1 can act as a coreceptor with CD4 for the HIV-1 virus envelope protein, potentially with more potent activity than isoform 1. It interacts with CX3CL1, ITGAV, ITGB3, ITGA4, ITGB1, and human respiratory syncytial virus (HRSV) protein G. CX3CR1 is involved in modulating host immune response.
CX3CR1 is also known as CCRL1, CMKBRL1, CMKDR1, GPR13, GPRV28, V28.
