Molecular basis for cold and menthol sensing by mammalian TRPM8.

The transient receptor potential melastatin member 8 (TRPM8) is a polymodal ion channel that senses cold and menthol in mammals. Despite prior structural studies, the mechanisms by which cold and menthol activate TRPM8 remain unresolved. Here, we present cryo-EM structures and extensive functional analyses to reveal cold- and menthol-dependent activation mechanisms. We observe that cold-sensing residues are widespread and that snapshots of cooling-dependent opening reveal dramatic pore rearrangement which suggest a mechanism for cold sensing. Menthol binds dynamically to drive channel activation toward a common gate with cold, but with specific outer pore conformations. Finally, we show how TRPM8 integrates cold and menthol modalities through overlapping but non-identical networks, revealing a coldspot that is central to cold activation of TRPM8 and is the location of allyl isothiocyanate (AITC) binding. These findings enhance our understanding of the molecular basis of physically and chemically induced cool sensation in mammals.