What is new about mild temperature sensing? A review of recent findings

Abstract

The superfamily of Transient Receptor Potential (TRP) channels is composed by a group of calcium-permeable ionic channels with a generally shared topology. The thermoTRP channels are a subgroup of 11 members, found in the TRPA, TRPV, TRPC, and TRPM subfamilies. Historically, members of this subgroup have been classified as cold, warm or hot-specific temperature sensors. Recently, new experimental results have shown that the role that has been given to the thermoTRPs in thermosensation is not necessarily strict. In addition, it has been shown that these channels activate over temperature ranges, which can have variations depending on the species and the interaction with a specific biological context. Investigation of these interactions could help to elucidate the mechanisms of activation by temperature, which remains uncertain. Abbreviations: Cryo-EM: Cryogenic electron microscopy; DRG: Dorsal root ganglia; H: Human; ROS: Reactive Oxygen Species; TG: Trigeminal ganglia; TRP: Transient Receptor Potential; TRPA: TRP ankyrin; TRPV: TRP vanilloid; TRPC: TRP canonical; TRPM: TRP melastatin.

Keywords: TRP channels; TRPA1; TRPM8; TRPV1; ThermoTRP; enthalpy; temperature sensing.

Figure 1.

Structures of some thermoTRPs determined by single-particle cryo-EM. The details of a single subunit are shown, the different colors match specific domains. The amino acids shown as red spheres represent the sites proposed as essential for the thermosensation. The asterisk in the structure of TRPV1 symbolizes some amino acids related to thermosensation (D261, M258, S250) that are not resolved in the available structures. Structural files from the Protein Data Bank and appropriate reference for each channel are as follows. TRPV1 (PDB 3J5P) [3]; TRPV2 (PDB 5AN8) [6]; TRPV3 (PDB 6MH0) [11]; TRPV4 (PDB 6BBJ) [7]; TRPA1 (PDB 3J9P) [12]; TRPM2 (PDB 6CO7) [17]; TRPM4 (PDB 6BCL) [18]; TRPM8 (PDB 6BPQ) [16]; TRPC5 structure (PDB 6AEI, is not available yet).

Figure 2.

Range of temperature of activation of thermoTRP channels and its variation in different species. The range of activation temperature for TRP channels in mammalians, amphibians, birds, fish, and reptiles is shown in °C. The most complete picture of the functions of thermoTRPs is only available in mammals. In most other species knowledge is incomplete and some thermoTRP channels show significant differences in their range of activation by temperature.