Transient receptor potential channels: current perspectives on evolution, structure, function and nomenclature

Abstract

The transient receptor potential superfamily of ion channels (TRP channels) is widely recognized for the roles its members play in sensory nervous systems. However, the incredible diversity within the TRP superfamily, and the wide range of sensory capacities found therein, has also allowed TRP channels to function beyond sensing an organism's external environment, and TRP channels have thus become broadly critical to (at least) animal life. TRP channels were originally discovered in Drosophila and have since been broadly studied in animals; however, thanks to a boom in genomic and transcriptomic data, we now know that TRP channels are present in the genomes of a variety of creatures, including green algae, fungi, choanoflagellates and a number of other eukaryotes. As a result, the organization of the TRP superfamily has changed radically from its original description. Moreover, modern comprehensive phylogenetic analyses have brought to light the vertebrate-centricity of much of the TRP literature; much of the nomenclature has been grounded in vertebrate TRP subfamilies, resulting in a glossing over of TRP channels in other taxa. Here, we provide a comprehensive review of the function, structure and evolutionary history of TRP channels, and put forth a more complete set of non-vertebrate-centric TRP family, subfamily and other subgroup nomenclature.

Keywords: ion channel evolution; molecular evolution; transient receptor potential evolution; transient receptor potential phylogeny.

Figure 1.

Current view of the relationship between TRP families (bold large) and subfamilies (at tree tips). For detailed family/subfamily/subgroup phylogenies and structural models, see electronic supplementary material, figures S1–S9. (Online version in colour.)

Figure 2.

Consensus phylogeny and distribution of the TRP superfamily. Top left shows TRP in the voltage-gated ion channel clade [13]. Taxa shown here: animals, choanoflagellates (Choano.; unicellular flagellates closely related to animals), fungi, apusozoans (Apuso.; flagellate eukaryotes), amoebozoans (Amoebo.; amoeboid eukaryotes), alveolates (including dinoflagellates), oomycetes (fungus-like eukaryotes), cryptophyte and green algae (Crypto. and G. Algae) and excavatans (basal eukaryotes). Filled circles indicate that the family to the left has been proposed to be present in the taxon above; blank circles indicate no evidence for that family in the indicated taxon [–11]. The dashed line for TRPY/TRPF indicates that its placement is especially uncertain. (Online version in colour.)