Structural basis of cooling agent and lipid sensing by the cold-activated TRPM8 channel

Abstract

Transient receptor potential melastatin member 8 (TRPM8) is a Ca²⁺-permeable cation channel that serves as the primary cold and menthol sensor in humans. Activation of TRPM8 by cooling compounds relies on allosteric actions of agonist and membrane lipid phosphatidylinositol-4,5-bisphosphate (PIP₂), but lack of structural information has thus far precluded a mechanistic understanding of ligand and lipid sensing by TRPM8. Using cryo-electron microscopy, we determined the structures of TRPM8 in complex with the synthetic cooling compound icilin, PIP₂, and Ca²⁺ and in complex with the menthol analog WS-12 and PIP₂. Our structures reveal the binding sites for cooling agonists and PIP₂ in TRPM8. Notably, PIP₂ binds to TRPM8 in two different modes, which illustrate the mechanism of allosteric coupling between PIP₂ and agonists. This study provides a platform for understanding the molecular mechanism of TRPM8 activation by cooling agents.