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

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. J Immunol 2015 May 1; 194(9):4055-7

Structural and evolutionary analysis of HLA-D-region products.

The major histocompatibility complex (MHC)--HLA in man and H-2 in mouse--encodes two classes of cell-surface antigens involved in the immune response. The amino acid sequences have been determined for a number of these molecules. Class I antigens, typified by the HLA-ABC antigens, are composed of a 43,000-molecular weight (MW) glycosylated transmembrane polypeptide with three external domains (alpha 1, alpha 2 and alpha 3), of which the one nearest the membrane (alpha 3) is associated with a 12,000-MW nonglycosylated polypeptide, beta 2-microglobulin. The HLA-D-region or class II antigens, DR, DC and SB, are composed of two glycosylated transmembrane polypeptides, of MWs 34,000 (alpha-chain) and 28,000 (beta-chain). Both chains have two external domains which presumably associate with each other, alpha 2, beta 2 being membrane proximal and alpha 1, beta 1 N-terminal and membrane distal. All four membrane-proximal domains (class I alpha 3, beta 2-microglobulin, class II alpha 2 and beta 2) have amino acid sequences that show significant similarities with immunoglobulin constant-region domains. This, together with the similarly placed internal disulphide bonds, suggests they might have an immunoglobulin-like structure (Fig. 1). We have now used computer graphics techniques to predict a detailed three-dimensional structure for the membrane-proximal domains of the class II antigens (alpha 2 and beta 2) based on the known coordinates of immunoglobulin constant domains (Fig. 2). The transmembrane regions of class II antigens have been modelled as two alpha-helices packed together. The proposed structure accounts for conservation of amino acids and leads to evolutionary predictions