Abstract
Transient receptor potential channels are a family of cation channels involved in diverse cellular functions. Most of these channels are expressed in the nervous system and play a key role in sensory physiology. TRPM8 (transient receptor potential melastatine 8), a member of this family, is activated by cold, cooling substances such menthol and icilin and voltage. Although TRPM8 is a thermosensitive channel highly expressed in cold sensory neurons, the mechanisms underlying its temperature sensitivity are still poorly understood. Here we show that, in sensory neurons, TRPM8 channel is localized in cholesterol-rich specialized membrane domains known as lipid rafts. We also show that, in heterologous expression systems, lipid raft segregation of TRPM8 is favored by glycosylation at the Asn(934) residue of the polypeptide. In electrophysiological and imaging experiments, using cold and menthol as agonists, we also demonstrate that lipid raft association modulates TRPM8 channel activity. We found that menthol- and cold-mediated responses of TRPM8 are potentiated when the lipid raft association of the channel is prevented. In addition, lipid raft disruption shifts the threshold for TRPM8 activation to a warmer temperature. In view of these data, we suggest a role for lipid rafts in the activity and temperature sensitivity of TRPM8. We propose a model wherein different lipid membrane environments affect the cold sensing properties of TRPM8, modulating the response of cold thermoreceptors.