Engineering light-gated glutamate receptors

Ionotropic glutamate receptors are the major neurotransmitter receptor found at excitatory synapses in the central nervous system. We have developed a light-gated ionotropic glutamate receptor (LiGluR) that, when introduced into neurons, enables remote control of their activity. Light regulation is conferred by a nanoscale photoswitch consisting of a glutamate analog that is covalently tethered to the glutamate receptor through a photoisomerizable azobenzene moiety. The photo-switch requires a single amino-acid substitution in the glutamate receptor as a point for covalent attachment; thus LiGluR can be genetically targeted to neurons of interest.We show that optical stimulation can be structured in designed spatial and temporal patterns, with action potentials generated by 1-5 millisecond long pulses of light. By changing the location of the amino-acid substitution, modifying the properties of the photo-switch, or applying this strategy to other glutamate receptors, we show that this approach represents a toolbox of options for precisely manipulating glutamate receptors and neural activity with light.