Structural Superimposition

Abstact

TRPM8, a cold-activated ion channel, enables mammals to sense cooling agents such as menthol. While PIP(2) is essential for menthol-induced activation of TRPM8, the precise cooperative mechanism and the specific binding mode of menthol have remained elusive. Here, we present cryo-EM structures of mouse TRPM8 in diverse conformations, including a PIP(2)-induced two-fold symmetric intermediate and an icilin-bound open state. Our results reveal that PIP(2) binding initiates a symmetry-breaking event, priming the channel for activation through a noncanonical intermediate states. The subsequent binding of cooling agonists promotes a transition back to four-fold symmetry. Notably, we find that menthol stabilizes the PIP(2)-bound state, thereby overcoming channel desensitization, while icilin, in concert with calcium, stabilizes a fully open conformation. Together, these structures illuminate a stepwise activation pathway involving distinct symmetry transitions and define the cooperative allosteric mechanism by which PIP(2) and cooling agonists gate the channel.