Nomenclature of Toso, Fas Apoptosis Inhibitory Molecule 3, and IgM FcR

Abstract

Hiromi Kubagawa and John E. Coligan coordinated an online meeting to define an appropriate nomenclature for the cell surface glycoprotein presently designated by different names: Toso, Fas apoptosis inhibitory molecule 3 (FAIM3), and IgM FcR (FcμR). FAIM3 and Faim3 are the currently approved symbols for the human and mouse genes, respectively, in the National Center for Biotechnology Information, Ensembl, and other databases. However, recent functional results reported by several groups of investigators strongly support a recommendation for renaming FAIM3/Faim3 as FCMR/Fcmr, a name better reflecting its physiological function as the FcR for IgM. Participants included 12 investigators involved in studying Toso/FAIM3(Faim3)/FμR, representatives from the Human Genome Nomenclature Committee (Ruth Seal) and the Mouse Genome Nomenclature Committee (Monica McAndrews), and an observer from the IgM research field (Michael Carroll). In this article, we provide a brief background of the key research on the Toso/FAIM3(Faim3)/FcμR proteins, focusing on the ligand specificity and functional activity, followed by a brief summary of discussion about adopting a single name for this molecule and its gene and a resulting recommendation for genome nomenclature committees.

Secreted IgM: New tricks for an old molecule

“…While the receptor's ability to bind sIgM has been repeatedly demonstrated, the originally reported antiapoptotic function of this molecule appeared to have been due to the use of an anti‐Fas antibody of the IgM isotype, as the antiapoptotic activity was not seen with an IgG anti‐Fas antibody . Although further studies are required to resolve some of the apparent discordant data, these findings have since led to the proposal to rename this gene “FCMR” …”

“…113,134 Although further studies are required to resolve some of the apparent discordant data, these findings have since led to the proposal to rename this gene "FCMR". 113,135 In humans, the FCMR is located on chromosome 1q32.2, adjacent to the PIGR and the FCAMR. 113,125 The FCMR shares sequence homology with those receptors, further supporting its function as an Ig-binding protein, although it is more distantly related than the PIGR and FCAMR are related to each other.…”

Emerging Functions of Natural IgM and Its Fc Receptor FCMR in Immune Homeostasis

“…Originally identified and termed as TOSO [encoded by Fas apoptosis inhibitory molecule 3 (FAIM3)] in 1998 ( 26 ), FCMR was recently rediscovered and characterized as an IgM-specific Fc receptor ( 27 , 28 ). A consensus nomenclature for this molecule has recently been proposed as FCMR ( 1 ). FCMR is a transmembrane protein with a predicted molecular weight of ~41 KDa, but with heavily O-linked glycosylation in the extracellular domain, a mature molecule can reach ~60 KDa ( 26 , 27 , 29 ).…”

“…An Fc receptor specific for IgM, now termed FCMR ( 1 ), was defined only 8 years ago. Importantly, and in contrast to most secreted IgG antibodies, secreted IgM (sIgM) can be subdivided into natural and immune IgM.…”

Integrative multi-platform meta-analysis of gene expression profiles in pancreatic ductal adenocarcinoma patients for identifying novel diagnostic biomarkers

“…More specifically, our results showed downregulation of the gene FAIM3 , which plays an important role in the immune system as it encodes an Fc receptor for immunoglobulins (Ig), M. Fc receptors specifically bind to the Fc region of Igs to mediate the unique functions of each class [ 33 , 34 ]. The expression of FAIM3 is reported in peripheral blood leukocytes and detected in high levels in chronic lymphocytic leukemia cells [ 35 ].…”