Fc Receptor Like 1 (FCRL1)

FCRL molecules belong to the immunoglobulin super family (IgSF) with a potential activating and inhibitory roles. The FCRL genes encode two intracellular receptors (FCRL A and B) and six transmembrane glycoproteins type I (FCRL1-6). FCRL1-6 are all type 1 transmembrane glycoproteins that contain immunoglobulin-like domains in their extracellular regions. They consist of three to nine immunoglobulin (Ig)-like domains in the extracellular region and immunoreceptor tyrosine-based activation (ITAM)/inhibition (ITIM) motifs in their cytoplasmic domain. Unlike FcRs, which are typically either activatory or inhibitory, three of the FCRLs (FCRL2, FCRL3, and FCRL5) contain both activatory and inhibitory sequences, suggesting that they might be capable of dual-modulation. FCRL1-5 are dominantly expressed in different stages of B-cells development. But, FCRL6 is preferentially expressed in different subsets of T-cells and NK cells. FCRL1-5 could regulate different features of B-cell evolution such as development, differentiation, activation, antibody secretion and isotype switching.