The Ig-like V-set domain comprises three loops analogous to the complementarity-determining regions (CDR) of Ig variable domains, which are responsible for engaging IgM. Mediates multivalent interactions with the CH4 domains of pentameric IgM, facilitating receptor clustering and signaling.
High-affinity Fc receptor for immunoglobulin M (IgM), both secreted and membrane-bound IgM (PubMed:19858324, PubMed:22675200, PubMed:36949194, PubMed:37095205). Primarily regulates IgM transport and homeostasis. In lymphoid cells, enables exocytosis of membrane-bound IgM on the plasma membrane as well as endocytosis of IgM-antigen complexes toward lysosomes for degradation. In mucosal epithelium, mediates retrotranscytosis of antigen-IgM complexes across mucosal M cells toward antigen-presenting cells in mucosal lymphoid tissues (PubMed:21908732, PubMed:28230186). Triggers costimulatory signaling and mediates most of IgM effector functions involved in B cell development and primary immune response to infection. Likely limits tonic IgM BCR signaling to self-antigens for proper negative selection of autoreactive B cells in the bone marrow and for the maintenance of regulatory B cell pool in peripheral lymphoid organs. Mediates antibody responses to T cell-dependent and T cell-independent antigens and promotes induction of an efficient neutralizing IgG response. Engages in cross-talk with antigen-receptor signaling via the non-canonical NF-kappa-B, MAP kinases and calcium signaling pathways (PubMed:19858324, PubMed:22675200, PubMed:25601920, PubMed:30840890).
Phosphorylated on both Tyr and Ser residues.
O-glycosylated. Sialylated. O-linked glycans regulate trafficking to the plasma membrane.
Expressed by CD19-positive B cells and CD4-positive and CD8-positive T cell populations in primary and secondary lymphoid tissues (at protein level). Among B cell subsets, detected in a subset of bone marrow pro- and pre-B cells, in most follicular and memory B cells and in a small subset of germinal center B cells (at protein level). Expressed at lower levels in CD56-positive NK cells (at protein level) (PubMed:19858324, PubMed:21908732, PubMed:22675200, PubMed:30840890). Expressed in lymph nodes, lung, thymus and kidneys. Very weak expression detected in spleen, liver, heart, and salivary gland.
FAIM3, TOSO, FCMR, Immunoglobulin mu Fc receptor, IgM FcR, Fas apoptotic inhibitory molecule 3, Regulator of Fas-induced apoptosis Toso
Proteins
Immuno-oncology
43146Da
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