Fc receptor-like protein 1 (FCRL1)

Fc receptor-like protein 1 (FCRL1) is a type I transmembrane glycoprotein receptor belonging to the immunoglobulin superfamily and is specifically expressed on B cells. It contains three extracellular Ig-like domains, a transmembrane region with a charged glutamic acid residue, and a cytoplasmic tail featuring ITAM-like motifs important for intracellular signaling. Unlike classical Fc receptors, FCRL1 does not bind immunoglobulin (Ig) and its natural ligand is unknown. FCRL1 is unique among its family in positively regulating B cell activation, promoting proliferation and survival through its recruitment of c-Abl kinase to ITAM-like motifs, and participating both independently and with co-signaling from the B cell receptor. Its expression is elevated in various B-cell malignancies and correlates with disease aggressiveness, making it a potential biomarker and target for immunotherapy strategies, especially in diffuse large B-cell lymphoma (DLBCL). Antibody-based therapies targeting FCRL1 are being explored for selective elimination or modulation of malignant B cells, but potential effects on normal B cell function and immune homeostasis remain to be fully characterized.

Other names

Fc receptor-like protein 1FCRL1FcRH1IFGP1IRTA5CD307aFcR-like protein 1FcRL1hIFGP1FCRH1Immune receptor translocation-associated protein 5Fc receptor homolog 1IFGP family protein 1gp42

Targeted antibodies may block FCRL1 to restore immunosurveillance and inhibit tumor growth. Antibody ligation of FCRL1 can modulate B cell activation or induce cell death in malignant B cells.