A genetically encoded sensor of membrane potential, FlaSh, was first introduced by Siegel and Isacoff (1997) as a fusion between the Shaker potassium channel and wild-type green fluorescent protein from Aequorea victoria (aqGFP).
Subsequent ion channel-based voltage sensors were designed to include a single fluorescent protein or FPs that form Förster Resonance Energy Transfer pairs (FRET).
Later sensors based on the voltage-sensing domain of Ciona intestinalis voltage-sensitive phosphatase (CiVSP) produced robust signals in mammalian cells.
These group have combined many Ciona intestinalis voltage sensor (CiVS) with different FPs to produce FP voltage sensors with improved properties.
However, to date this approach had not yielded probes with the necessary combination of signal size and speed that would make it possible to image individual voltage signals in neurons:
1. Action potentials
2. Subthreshold potentials
This paper report the development of an FP voltage sensor, named ArcLight, which is based on a fusion of the CiVS and the fluorescent protein super ecliptic pHluorin that carries an A227D mutation.