The Influence Of Voltage Sensor Activity On Arclight Dynamics

Many genetically-encoded voltage indicators have been developed based on voltage-sensitive phosphatases. One of the most promising of these indicators is Arclight, largely due to its substantial signal in response to voltage changes. Although it is evident that the fluorophore is fundamentally following the voltage sensor movement, the fluorescence change is comprised of multiple components; how these fluorescence components reflect voltage sensor movement remains poorly understood. Using simultaneous electrophysiological and optical recordings of oocytes expressing wild-type and mutant Arclight constructs, we investigated the influence of altered voltage sensor behavior on Arclight fluorescence. We found that the latency before fluorescence change onset correlated with gating charge movement, and that the fluorescence change following prolonged depolarizations showed alterations in kinetics and thermodynamics consistent with voltage sensor relaxation. Other features of fluorophore movement, however, were less obviously coupled to voltage sensor dynamics. These results may help guide future attempts to optimize the properties of Arclight and related fluorescent proteins. Support: NIH GM030376.