Fc receptor-like protein 3 (FCRL3)

Fc receptor-like protein 3 (FCRL3) is a type I transmembrane glycoprotein encoded by the FCRL3 gene on chromosome 1, belonging to the immunoglobulin receptor superfamily[1][5]. It features both immunoreceptor tyrosine-based activation (ITAM) and inhibitory (ITIM) motifs in its cytoplasmic tail, enabling it to co-regulate immune signaling by recruiting activating or inhibitory intracellular phosphatases. FCRL3 is mainly expressed on B lymphocytes—including naïve, memory, marginate zone, and some plasma B cell subsets—as well as on regulatory and certain cytotoxic T cells and rare NK cells[1][2][3]. Engagement of FCRL3 modulates B cell receptor and Toll-like receptor 9 (TLR9) signaling pathways, affecting B cell activation, proliferation, and differentiation; in T regulatory cells, high FCRL3 expression is linked with impaired suppressive function and association with the −169 C/T FCRL3 promoter SNP, which increases autoimmunity susceptibility[1][2][3]. FCRL3 is implicated in the development of rheumatoid arthritis, systemic lupus erythematosus, autoimmune thyroid disease, and other autoimmune disorders, and is considered a genetic and cellular biomarker for autoimmunity risk[1][2]. No endogenous ligand is currently known, and the molecule is only present in humans, not in mice[1][3].

Other names

FcRL3FCRH3IFGP3SPAP2CD307cFcR-like protein 3hIFGP3IRTA3MAIAImmune receptor translocation-associated protein 3SH2 domain-containing phosphatase anchor protein 2Immunoglobulin superfamily receptor translocation associated protein 3Fc receptor homolog 3IFGP family protein 3SPAP2aSPAP2bSPAP2cSPAP2dSPAP2e