Fc mu receptor (FcμR) (FcμR)

The Fc mu receptor (FcμR), also known as FAIM3 or TOSO, is a type I transmembrane glycoprotein that specifically binds the Fc portion of IgM antibodies [1, 2]. It is primarily expressed on the surface of B-lymphocytes, and to a lesser extent on T and NK cells, where it plays a vital role in B-cell homeostasis and the regulation of the humoral immune response [2, 4]. FcμR facilitates the internalization of IgM-antigen complexes, thereby influencing B-cell receptor signaling and antigen presentation [2]. In clinical oncology, FcμR is significantly overexpressed in chronic lymphocytic leukemia (CLL) cells, making it a valuable biomarker for diagnosis and a potential target for antibody-based therapies [3]. While its initial characterization suggested a role in inhibiting Fas-mediated apoptosis, its primary physiological function is now recognized as the regulation of IgM metabolism and B-cell activation [1, 4]. Current therapeutic research focuses on utilizing anti-FcμR monoclonal antibodies to selectively target malignant B-cells while minimizing impact on other immune subsets [3]. [1] UniProt Consortium, Q9NR71; [2] Kubagawa et al. (2009) J. Exp. Med.; [3] Vire et al. (2011) Blood; [4] Lang et al. (2013) J. Exp. Med.

Other names

FAIM3Fas apoptotic inhibitory molecule 3TOSOFCMRIgM Fc receptor

Binding and internalization of IgM-antigen complexes; modulation of B-cell survival and activation signals.