FCAR
Description
The FCAR (Fc alpha receptor) is a protein-coding gene located on chromosome 19.
The Fc fragment of IgA receptor (FCAR) is a human gene that encodes for the transmembrane receptor FcαRI, also known as CD89. FcαRI binds to the heavy-chain constant region of IgA antibodies. It is expressed on the cell surface of myeloid lineage cells, including neutrophils, monocytes, macrophages, and eosinophils, but is absent from intestinal macrophages and mast cells. FcαRI plays a role in both pro- and anti-inflammatory responses depending on the state of IgA bound. Inside-out signaling primes FcαRI for ligand binding, while outside-in signaling, triggered by ligand binding, depends on FcαRI association with the Fc receptor gamma chain (FcR γ-chain). Despite being part of the Fc receptor immunoglobulin superfamily, the protein's primary structure is similar to receptors in the leukocyte receptor cluster (LRC), and the FCAR gene resides among LRC genes on chromosome 19. This contrasts with the location of other Fc receptor immunoglobulin superfamily members, which are encoded on chromosome 1. While FCAR equivalents exist in several species, there is no homolog in mice. The FcαRI α-chain comprises two extracellular domains, EC1 and EC2, a transmembrane domain, and an intracellular domain. However, this chain alone cannot perform signaling in response to IgA binding, requiring association with a dimeric form of FcR g-chain, which contains immunoreceptor tyrosine-based activation motifs (ITAMs).
FCAR is also known as CD89, CTB-61M7.2, FcalphaR, FcalphaRI.
