Lemoine, D. et al. Proc. Natl. Acad. Sci. USA 110, 20813–20818 (2013).

Optogenetic approaches rely on the expression of heterologous light-sensitive ion channels or pumps in cells, enabling the use of light to selectively control cells. Optopharmacological approaches, in contrast, rely on the expression of engineered versions of endogenous receptors or channels that are tagged with a tethered photoswitchable ligand. This strategy has been used to generate light-sensitive versions of glutamate, GABA and nicotinic receptors by fusing a photoisomerizable azobenzene derivative to a molecule that acts as a competitive or noncompetitive ligand to the receptor. Lemoine et al. report an engineered, photoactivatable version of the ATP-activated P2X channel by adding the azobenzene to the transmembrane region of the protein. This tool lends control over P2X signaling in cells and offers a new strategy for rendering engineered channels susceptible to light.