A unified nomenclature for the superfamily of TRP cation channels.

The TRP superfamily includes a diversity of non-voltagegated cation channels that vary significantly in their selectivity and mode of activation. Nevertheless, members of the TRP superfamily share significant sequence homology and predicted structural similarities. Currently, most of the genes and proteins that comprise the TRP superfamily have multiple names and, in at least one instance, two distinct genes belonging to separate subfamilies have the same name. Moreover, there are many cases in which highly related proteins that belong to the same subfamily have unrelated names. Therefore, to minimize confusion, we propose a unified nomenclature for the TRP superfamily. The current effort to unify the TRP nomenclature focuses on three subfamilies (TRPC, TRPV, and TRPM) that bear significant similarities to the founding member of this superfamily, Drosophila TRP, and which include highly related members in worms, flies, mice, and humans (Table 1). Members of the three subfamilies conFigure 1. Phylogenetic Tree of the TRP Superfamily tain six transmembrane segments, a pore loop sepaThe tree, which was adapted from Clapham et al., 2001 (Nat. Rev. rating the final two transmembrane segments, and Neurosci. 2, 387–396), was calculated using the neighbor-joining similarity in the lengths of the cytoplasmic and extracelmethod and human, rat, and mouse sequences. lular loops. In addition, the charged residues in the S4 segment that appear to contribute to the voltage sensor and proteins (Table 2). In the case of the TRPV proteins, in voltage-gated ion channels are not conserved. The the numbering system is also based in part on the groupTRP-Canonical (TRPC) subfamily (formerly short-TRPs ings of the TRPV proteins. New members of each subor STRPs) is comprised of those proteins that are the family will maintain the same root name and, with the most highly related to Drosophila TRP. The TRPV subexception of TRPV3, will be assigned the next number family (formerly OTRPC), is so named based on the origiin the sequence. Currently, TRPV3 is unassigned to nal designation, Vanilloid Receptor 1 (VR1), for the first maintain the TRPV1/ TRPV2 and TRPV5/TRPV6 groupmammalian member of this subfamily (now TRPV1). The ings and so that the former OTRPC4 could be renamed TRPV4. The next TRPV protein will be designated name for the TRPM subfamily (formerly long-TRPs or TRPV3. LTRPs) is derived from the first letter of Melastatin, the We hope this new nomenclature will add clarity to the former name (now TRPM1) of the founding member of field and simplify the naming of new members of the TRP this third subfamily of TRP-related proteins. Based on superfamily. We recommend that accession numbers amino acid homologies, the mammalian members of be used whenever it is necessary to unambiguously these three subfamilies can be subdivided into several specify a given variant resulting from alternative mRNA groups each (Table 2 and Figure 1). splicing. Finally, this nomenclature has been approved The numbering system for the mammalian TRPC, by the HUGO Gene Nomenclature Committee and we TRPV, and TRPM proteins takes into account the order recommend that this system be used in all future publiof their discovery and, in as many cases as possible, cations concerning TRPC, TRPV, and TRPM subfamily the number that has already been assigned to the genes members.