Laboratory of Molecular Neurobiology and Biophysics, Rockefeller University, New York, United States.
Howard Hughes Medical Institute, New York, United States.
Elife. 2021 Aug 10;10:e71188. doi: 10.7554/eLife.71188.
Mechanosensitive ion channels mediate transmembrane ion currents activated by mechanical forces. A mechanosensitive ion channel called TACAN was recently reported. We began to study TACAN with the intent to understand how it senses mechanical forces and functions as an ion channel. Using cellular patch-recording methods, we failed to identify mechanosensitive ion channel activity. Using membrane reconstitution methods, we found that TACAN, at high protein concentrations, produces heterogeneous conduction levels that are not mechanosensitive and are most consistent with disruptions of the lipid bilayer. We determined the structure of TACAN using single-particle cryo-electron microscopy and observed that it is a symmetrical dimeric transmembrane protein. Each protomer contains an intracellular-facing cleft with a coenzyme A cofactor, confirmed by mass spectrometry. The TACAN protomer is related in three-dimensional structure to a fatty acid elongase, ELOVL7. Whilst its physiological function remains unclear, we anticipate that TACAN is not a mechanosensitive ion channel.
机械敏感离子通道介导由机械力激活的跨膜离子电流。最近报道了一种称为 TACAN 的机械敏感离子通道。我们开始研究 TACAN，旨在了解它如何感知机械力并作为离子通道发挥作用。使用细胞贴附记录方法，我们未能鉴定出机械敏感离子通道活性。使用膜重建方法，我们发现 TACAN 在高蛋白质浓度下产生非机械敏感的异质传导水平，最符合脂质双层的破坏。我们使用单颗粒冷冻电子显微镜确定了 TACAN 的结构，并观察到它是一种对称的二聚体跨膜蛋白。每个原聚体都包含一个含有辅酶 A 辅因子的细胞内裂隙，这一点通过质谱法得到了证实。TACAN 原聚体在三维结构上与脂肪酸延长酶 ELOVL7 相关。虽然它的生理功能尚不清楚，但我们预计 TACAN 不是一种机械敏感的离子通道。
