| Description: |
Chemokines (chemotactic cytokines) are a family of chemoattractant molecules. They attract leukocytes to areas of inflammation and lesions, and play a key role in leukocyte activation. Originally defined as host defense proteins, chemokines are now known to play a much broader biological role []. They have a wide range of effects in many different cell types beyond the immune system, including, for example, various cells of the central nervous system [], and endothelial cells, where they may act as either angiogenic or angiostatic factors [].The chemokine family is divided into four classes based on the number and spacing of their conserved cysteines: 2 Cys residues may be adjacent (the CC family); separated by an intervening residue (the CXC family); have only one of the first two Cys residues (C chemokines); or contain both cysteines, separated by three intervening residues (CX3C chemokines).Chemokines exert their effects by binding to rhodopsin-like G protein-coupled receptors on the surface of cells. Following interaction with their specific chemokine ligands, chemokine receptors trigger a flux in intracellular calcium ions, which cause a cellular response, including the onset of chemotaxis. There are over fifty distinct chemokines and least 18 human chemokine receptors []. Although the receptors bind only a single class of chemokines, they often bind several members of the same class with high affinity. Chemokine receptors are preferentially expressed on important functional subsets of dendritic cells, monocytes and lymphocytes, including Langerhans cells and T helper cells [, ]. Chemokines and their receptors can also be subclassified into homeostatic leukocyte homing molecules (CXCR4, CXCR5, CCR7, CCR9) versus inflammatory/inducible molecules (CXCR1, CXCR2, CXCR3, CCR1-6, CX3CR1).CC chemokine receptors are a subfamily of the chemokine receptors that specifically bind and respond to cytokines of the CC chemokine family. There are currently ten members of the CC chemokine receptor subfamily, named CCR1 to 10. The receptors receptors are found in monocytes, lymphocytes, basophils and eosinophils.This entry represents CC chemokine receptor 9 (CCR9), which was previously designated as the orphan receptors GPR28 and GPR 9-6. CCR9 is expressed predominantly in the thymus, in both mature and immature T cells, and is also found in the lymph nodes, spleen, glomerular podocytes, bone marrow stromal cells and the small intestine [, , , , ]. Transfected cells expressing CCR9 receptor bind specifically to CCL25 (also known as Thymus-Expressed Chemokine) []. This interaction may play a pivotal role in T-cell migration in the thymus []. CCR9 activation has also been shown to influence cancer cell migration, invasion and matrix metallopeptidase expression, which together may affect prostate cancer metastasis []. |
