HHMI, The Rockefeller University, New York, NY, 10065.
Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, New York, NY, 10065.
Proc Natl Acad Sci U S A. 2023 Mar 21;120(12):e2221541120. doi: 10.1073/pnas.2221541120. Epub 2023 Mar 13.
Mechanical forces modify the cell membrane potential by opening mechanosensitive ion channels. We report the design and construction of a lipid bilayer tensiometer to study channels that respond to lateral membrane tension, [Formula: see text] , in the range 0.2 to 1.4 [Formula: see text] (0.8 to 5.7 [Formula: see text] ). The instrument consists of a black-lipid-membrane bilayer, a custom-built microscope, and a high-resolution manometer. Values of [Formula: see text] are obtained from the determination of the bilayer curvature as a function of applied pressure by means of the Young-Laplace equation. We demonstrate that [Formula: see text] can be determined by calculating the bilayer radius of curvature from fluorescence microscopy imaging or from measurements of the bilayer's electrical capacitance, both yielding similar results. Using electrical capacitance, we show that the mechanosensitive potassium channel TRAAK responds to [Formula: see text] , not curvature. TRAAK channel open probability increases as [Formula: see text] is increased from 0.2 to 1.4 [Formula: see text] but open probability never reaches 0.5. Thus, TRAAK opens over a wide range of [Formula: see text] , but with a tension sensitivity about one-fifth that of the bacterial mechanosensitive channel MscL.
机械力通过打开机械敏感离子通道来改变细胞膜电位。我们设计并构建了一种脂质双层张力计，用于研究对侧向膜张力 [Formula: see text] （0.8 至 5.7 [Formula: see text]）作出响应的通道。该仪器由黑脂质膜双层、定制显微镜和高分辨率压力计组成。通过使用杨氏拉普拉斯方程确定施加压力下双层曲率的函数，可以获得 [Formula: see text] 的值。我们证明，通过荧光显微镜成像或测量双层的电容来计算双层的曲率半径，可以确定 [Formula: see text]，两者得出的结果相似。通过电容测量，我们发现机械敏感钾通道 TRAAK 对 [Formula: see text] 作出响应，而不是曲率。当 [Formula: see text] 从 0.2 增加到 1.4 [Formula: see text] 时，TRAAK 通道的开放概率增加，但开放概率从未达到 0.5。因此，TRAAK 在 [Formula: see text] 较宽的范围内打开，但张力敏感性约为细菌机械敏感通道 MscL 的五分之一。
