Huffer Kate, Denley Matthew C S, Oskoui Elisabeth V, Swartz Kenton J
Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892.
Present Address: Imperial College London, Exhibition Rd, South Kensington, London SW7 2AZ, UK.
bioRxiv. 2024 Aug 21:2024.05.20.595003. doi: 10.1101/2024.05.20.595003.
Transient Receptor Potential (TRP) channels are a large and diverse family of tetrameric cation selective channels that are activated by many different types of stimuli, including noxious heat or cold, organic ligands such as vanilloids or cooling agents, or intracellular Ca. Structures available for all subtypes of TRP channels reveal that the transmembrane domains are closely related despite their unique sensitivity to activating stimuli. Here we use computational and electrophysiological approaches to explore the conservation of the cooling agent binding pocket identified within the S1-S4 domain of the Melastatin subfamily member TRPM8, the mammalian sensor of noxious cold, with other TRPM channel subtypes. We find that a subset of TRPM channels, including TRPM2, TRPM4 and TRPM5, contain pockets very similar to the cooling agent binding pocket in TRPM8. We then show how the cooling agent icilin modulates activation of TRPM4 to intracellular Ca, enhancing the sensitivity of the channel to Ca and diminishing outward-rectification to promote opening at negative voltages. Mutations known to promote or diminish activation of TRPM8 by cooling agents similarly alter activation of TRPM4 by icilin, suggesting that icilin binds to the cooling agent binding pocket to promote opening of the channel. These findings demonstrate that TRPM4 and TRPM8 channels share related ligand binding pockets that are allosterically coupled to opening of the pore.
瞬时受体电位（TRP）通道是一个庞大且多样的四聚体阳离子选择性通道家族，可被多种不同类型的刺激激活，包括有害的热或冷、香草酸或冷却剂等有机配体，或细胞内钙离子。所有TRP通道亚型的现有结构表明，尽管它们对激活刺激具有独特的敏感性，但跨膜结构域密切相关。在这里，我们使用计算和电生理方法来探索在Melastatin亚家族成员TRPM8（有害冷觉的哺乳动物感受器）的S1 - S4结构域中鉴定出的冷却剂结合口袋与其他TRPM通道亚型之间的保守性。我们发现，包括TRPM2、TRPM4和TRPM5在内的一部分TRPM通道含有与TRPM8中的冷却剂结合口袋非常相似的口袋。然后我们展示了冷却剂艾西利定如何调节TRPM4对细胞内钙离子的激活，增强通道对钙离子的敏感性并减少外向整流，以促进在负电压下的开放。已知可促进或减少冷却剂对TRPM8激活的突变同样会改变艾西利定对TRPM4的激活，这表明艾西利定与冷却剂结合口袋结合以促进通道开放。这些发现表明，TRPM4和TRPM8通道共享相关的配体结合口袋，这些口袋与孔的开放变构偶联。
