CX3C chemokine receptor 1, member of the class A family of seven-transmembrane G protein-coupled receptors
CX3CR1 is an inflammatory receptor specific for CX3CL1 (also known as fractalkine in human), which is involved in the adhesion and migration of leukocytes. The CX3C chemokine subfamily is only represented by CX3CL1, which exists in both soluble and membrane-anchored forms. Membrane-anchored form promotes strong adhesion of receptor-bearing leukocytes to CX3CL1-expressing endothelial cells. On the other hand, soluble CX3CL1, which is released by the proteolytic cleavage of membrane-anchored CX3CL1, is a potent chemoattractant for CX3CR1-expressing T cells and monocytes. Chemokine family membership is defined on the basis of sequence homology and on the presence of variations on a conserved cysteine motif, which allows the family to further divide into four subfamilies (CC, CXC, XC, and CX3C). Chemokines interact with seven-transmembrane receptors which are typically coupled to G protein for signaling.