Fig. 2.

Optogenetic modulation of postsynaptic neuronal function at multiple levels of cellular activity. (A) Synthetic light-gated receptors, such as the OptoXR’s, are coupled to G-protein signaling cascades that alter postsynaptic function by activating intracellular second-messenger cascades that may lead to alterations in neuronal excitability. (B) Light-inducible protein dimerizers will permit the selective control of intracellular signaling cascades and other diverse cellular processes with subsecond temporal resolution and subcellular spatial resolution through light activation of protein-protein interactions. (C) Light-switchable transgenes will permit the selective control of target gene expression within genetically defined neuronal populations to test the causal role of gene activation on various behaviors. Shown in the figure is a schematic of the LightOn gene expression system, which involves light-induced homodimerization of GAVP, which then interact with upstream UASG promoter elements to initiate the transcription of a gene of interest.