Variable Consequences of Membrane Targeting Motifs for Genetically Encoded Voltage Indicators

Abstract

Golgi and ER export signals have widely been used to improve membrane trafficking of optical bio-sensors. Previously, we reported a linker modified version of a genetically encoded voltage indicator engineered to image action potential spikes of neurons. Optimization of membrane expression was expected to improve the signal to noise ratio by minimizing unwanted none voltage dependent fluorescence. Accordingly, either Golgi or ER trafficking motif, or both were introduced into Bongwoori-R3 and affected its voltage sensing properties such as the kinetics, responsive voltage range and ΔF/F signal size. The ER motif improved the fluorescence response but it also caused increased time constants and a shifted V1/2 toward hyperpolarization. Introducing spacers between the fluorescent protein and the ER targeting motif recovered the response speed while maintaining the improved fluorescence signal size. This research was supported by the National Institute of Neurological Disorders and Stroke of the National Institutes of Health under the award number U01NS099691.