A general approach to engineer positive-going eFRET voltage indicators
Ahmed S. Abdelfattah, Rosario Valenti, Jihong Zheng, Allan M. Wong, GENIE Project Team, Amy S. Chuong, J. Hasseman, Vivek Jayaraman, Ilya Kolb, Wyatt Korff, Luke D. Lavis, Yajie Liang, Loren L. Looger, Derek Merryweather, Daniel Reep, Nelson Spruston, Karel Svoboda, Arthur Tsang, Getahun Tsegaye, Glenn Turner, Kaspar Podgorski, Minoru Koyama, Douglas S. Kim, Eric R. Schreiter
Abstract
Imaging membrane voltage from genetically defined cells offers the unique ability to report spatial and temporal dynamics of electrical signaling at cellular and circuit levels. Here, we present a general approach to engineer electrochromic fluorescence resonance energy transfer (eFRET) genetically encoded voltage indicators (GEVIs) with positive-going fluorescence response to membrane depolarization through rational manipulation of the native proton transport pathway in microbial rhodopsins. We transform the state-of-the-art eFRET GEVI Voltron into Positron, with kinetics and sensitivity equivalent to Voltron but flipped fluorescence signal polarity. We further apply this general approach to GEVIs containing different voltage sensitive rhodopsin domains and various fluorescent dye and fluorescent protein reporters.