145464

Sheep Anti-FCRLA (Fc Receptor-Like A, FCRLc1, FCRLM1, FCRLX, FcRX, FREB, Fc Receptor Homolog Expressed in B cells)

FCRLA (Fc Receptor­Like A; also known as FcRX and Fc receptor Homolog Expressed in B cells) is a 44kD intracellular member of the Fc gamma RI class, FcR family, Immunoglobulin Superfamily of molecules. It is associated with B lineage cells, and has been identified in virtually all splenic B cells, peritoneal B1b and B2 B cells, and immature through mature bone marrow B cells. Not all cells show equal expression patterns. In the spleen, weak FCRLA expression occurs in naïve follicular and marginal zone B cells, and increases with activation state. FcRLA is suggested to act as an ER chaperone during antibody maturation, and is known to bind to IgM, IgA, and IgG prior to their secretion. Mouse FCRLA is synthesized as a 34kD, 322 amino acid (aa) precursor that contains a 30 aa signal sequence, two C2-type Ig-like domains (aa80-169 and 182-26), and a C-terminal poly-Proline region (aa289-294). Although there is no traditional ER retention signal, a viable substitute is assumed to exist at the N­terminus of the mature molecule. FCRLA is believed to exist naturally as a monomer; however, disulfide­linkage can occur during experimental manipulation. While four potential isoform variants are reported, it is unclear if any are actually expressed. One shows an Ala insertion after Ala28, a second shows an AlaIle substitution for aa20-22, a third contains that previous AlaIle substitution coupled to a deletion of aa90-115, while a fourth utilizes an alternative start site at Met62. Over aa221-352, mouse FCRLA shares 68% and 55% aa sequence identity with rat and human FCRLA, respectively.