Complement component 5a receptor 2 is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

of the

complement system The complement system, also known as complement cascade, is a part of the humoral, innate immune system and enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inf ...

that in humans is encoded by the ''C5AR2''

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

. It is highly expressed in the blood and spleen, predominantly by

myeloid Myeloid tissue, in the bone marrow sense of the word '' myeloid'' ('' myelo-'' + '' -oid''), is tissue of bone marrow, of bone marrow cell lineage, or resembling bone marrow, and myelogenous tissue (''myelo-'' + '' -genous'') is any tissue ...

cells.

Function

The

anaphylatoxin Anaphylatoxins, or complement peptides, are fragments ( C3a, C4a and C5a) that are produced as part of the activation of the complement system. Complement components C3, C4 and C5 are large glycoproteins that have important functions in the immu ...

s C3a and C5a are fragments of C3 and C5 generated via

proteolytic cleavage Proteolysis is the breakdown of proteins into smaller polypeptides or amino acids. Protein degradation is a major regulatory mechanism of gene expression and contributes substantially to shaping mammalian proteomes. Uncatalysed, the hydrolysis o ...

by C3 convertases and C5 convertases during the complement cascade. They are pro-inflammatory mediators which bind to the

anaphylatoxin receptors The anaphylatoxin receptors are a group of G-protein coupled receptors which bind anaphylatoxin Anaphylatoxins, or complement peptides, are fragments ( C3a, C4a and C5a) that are produced as part of the activation of the complement system. Comp ...

, C3aR, C5aR1 and C5aR2. The anaphylatoxin receptors are a family of three proteins which beloing to the

G protein-coupled receptor G protein-coupled receptors (GPCRs), also known as seven-(pass)-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptors, and G protein-linked receptors (GPLR), form a large group of evolutionarily related ...

superfamily. C3aR and C5aR1 bind C3a and C5a, respectively, which mediate a broad range of effects in host defense, including chemoattraction,

vasodilation Vasodilation, also known as vasorelaxation, is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. Blood vessel wa ...

and immune cell activation. C5aR2 binds C5a, but lacks GPCR activity, and its function is less well understood. C5aR2 was initially thought be a

decoy receptor A decoy receptor is a receptor that is able to recognize and bind specific growth factors or cytokines efficiently, but is not structurally able to signal or activate the intended receptor complex. It acts as an inhibitor, binding a ligand and keepi ...

, acting as a sink for C5a to negatively regulate C5aR1 function. However, more recent research has uncovered independent roles for C5aR2, including modulation of the innate immune response in myeloid cells, translocation of C5a to drive transendothelial migration of

neutrophil Neutrophils are a type of phagocytic white blood cell and part of innate immunity. More specifically, they form the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. Their functions vary in differe ...

β-arrestin Arrestins (abbreviated Arr) are a small family of proteins important for regulating signal transduction at G protein-coupled receptors. Arrestins were first discovered in the late '80s as a part of a conserved two-step mechanism for regulatin ...

recruitment and modulation of ERK signalling and modulation of

lipid metabolism Lipid metabolism is the synthesis and degradation of lipids in cells, involving the breakdown and storage of fats for energy and the synthesis of structural and functional lipids, such as those involved in the construction of cell membranes. In ani ...

obesity Obesity is a medical condition, considered by multiple organizations to be a disease, in which excess Adipose tissue, body fat has accumulated to such an extent that it can potentially have negative effects on health. People are classifi ...

through C3a-desArg binding. C5aR2 has been implicated in a broad range of inflammatory and infectious diseases.

References

{{G protein-coupled receptors G protein-coupled receptors