Genetically-Encoded Fluorescent Voltage Sensors Capable of Resolving a 6MV Depolarization

Abstract

Genetically encoded fluorescent sensors of membrane potentials utilize the voltage sensing domain of the voltage-sensing phosphatase (VSPs) gene family. Probes based on the Danio Rerio voltage-sensing domain exhibit fast optical responses of around 5 msec. Here we developed several potential optical sensors by mutating the voltage-sensing domain which consists of four transmembrane segments (S1-S4). Mutations to S4 changed the voltage response resulting in a 'tuned' sensor that yields an optical response at physiological values. Mutations to the S2 domain improved the speed of the optical response to less than 5 msec Tau on/off. Double mutations incorporating the S2 and S4 mutations were not necessarily additive suggesting potential interaction sites between the S2 and S4 transmembrane domains.