Photoswitchable Lipids for the Optical Control of Mechanosensitive Ion Channels

传统意义上的光遗传学，即使用从天然丰富的生色团(视网膜、黄素等)获得光敏性的工程蛋白，只是用光影响生物活性的一种方式。光药理学提供了另一种选择，我们将其定义为通过合成光开关来控制生物活性的努力。它们可以共价或非共价连接到目的蛋白上。然而，光开关也可以整合到脂类中，直接通过蛋白质/脂类相互作用影响跨膜蛋白，或者通过改变承载蛋白质的膜的结构和动力学来间接影响跨膜蛋白。这将很难用纯粹的遗传方法进行编码。对于机械敏感通道，观察到脂类和蛋白质之间特别紧密的耦合，该通道随着脂双层侧向压力的变化而打开和关闭。为了更好地理解蛋白质和脂膜之间偶联的一般原理并用光来影响这一过程，我们建议使用一种依赖于可光切换脂类(光脂)的实验/理论相结合的方法。这些光脂来自膜的天然成分，可以通过化学合成获得。在通道方面，我们将研究MSCL，这是一个机械敏感通道的细菌模型系统，以及哺乳动物的TRAAK钾通道。实验和模拟将使我们了解光脂如何改变膜的结构和动力学，并得出脂/蛋白质偶联的分子图像。这项工作将指导进一步的方法来设计和合成功能改进的光脂。最终，我们的光脂可能会实现对机械敏感通道的光学控制，这些通道是听觉和触觉和疼痛的基础。

Optogenetics in the conventional sense, i.e. the use of engineered proteins that gain their light-sensitivity from naturally abundant chromophores (retinal, flavins etc.), is only one way to influence biological activity with light. An alternative is provided by Photopharmacology, which we define as an effort to control biological activity with synthetic photoswitches. These can be covalently or non-covalently attached to the protein of interest. However, photoswitches can also be integrated into lipids that influence transmembrane proteins directly via protein/lipid interactions, or indirectly by altering the structure and dynamics of the membrane that hosts the protein. This would be difficult to encode with purely genetic methods. A particularly intimate coupling between lipids and proteins is observed for mechanosensitive channels, which open and close in response to changes in the lateral pressure of the lipid bilayer. To better understand general principles of coupling between proteins and lipid membranes and to influence this process with light, we propose to use a combined experimental/theoretical approach that relies on photoswitchable lipids (photolipids). These photolipids are derived from natural components of the membrane and are accessible trough chemical synthesis. With respect to the channels, we will investigate MscL, which is a bacterial model system for mechanosensitive channels, and the mammalian TRAAK potassium channel. Experiments and simulations will allow us to understand how photolipids alter the structure and dynamics of the membrane, and to derive a molecular picture of the lipid/protein coupling. This work will then guide further approaches towards the design and synthesis of functionally improved photolipids. Ultimately, our photolipids may enable the optical control of mechanosensitive channels that underlie hearing and the perception of touch and pain.