The menthol receptor TRPM8 is a thermosensitive transient receptor potential (TRP) ion channel that is activated at temperatures below 26 °C and is essential for the perception of cold or cooling agents in mammals. However, the structural and energetic details of the gating mechanism related to the temperature modulation have been eluding scientists. Now, writing in Nature, Choi, Lin et al. report cryo-electron microscopy (cryo-EM)-derived structural observations on this mechanism, and combine them with hydrogen–deuterium exchange mass spectroscopy (HDX-MS) to obtain a more dynamic view of the process.

The group of researchers first obtained cryo-EM structures of the avian TRPM8 in its apo form in cell-derived vesicles. Alongside already known states, the structures revealed a semi-swapped state due to large conformational transitions of the S6 transmembrane helix and pore regions, which were supported by HDX-MS studies detecting energetic changes in these regions. Comparison with both menthol-bound human and cold-insensitive avian TRPM8 structures identified Y995 in this region as a critical residue that induces its stabilization in the presence of menthol ligand. At the same time, temperature-dependent HDX-MS revealed differences in energetics between the human and avian orthologs, with cold-induced enthalpic stabilization of the outer pore region especially noteworthy in the human ortholog, conferring cold sensitivity. For the avian ortholog, manipulations that destabilize an interface coordinated by Y905 enhance its response to cold. Also, for both human and avian channels, a phosphatidylinositol lipid stabilizes a buried hydrophobic cleft within the S5–S6 region and in this way modulates the channel’s cold sensitivity.