Remote Control of Neuronal Activity with a Light-Gated Glutamate Receptor

Abstract

The ability to stimulate select neurons in isolated tissue and in living animals is important for investigating their role in circuits and behavior. We show that the engineered light-gated ionotropic glutamate receptor (LiGluR), when introduced into neurons, enables remote control of their activity. Trains of action potentials are optimally evoked and extinguished by 380 nm and 500 nm light, respectively, while intermediate wavelengths provide graded control over the amplitude of depolarization. Light pulses of 1-5 ms in duration at approximately 380 nm trigger precisely timed action potentials and EPSP-like responses or can evoke sustained depolarizations that persist for minutes in the dark until extinguished by a short pulse of approximately 500 nm light. When introduced into sensory neurons in zebrafish larvae, activation of LiGluR reversibly blocks the escape response to touch. Our studies show that LiGluR provides robust control over neuronal activity, enabling the dissection and manipulation of neural circuitry in vivo.

Two-photon brightness of azobenzene photoswitches designed for glutamate receptor optogenetics

“…The 1P excitation with 405 nm generated a saturated photocurrent that was reversible with 488 nm (Fig. 3C, i, purple and green bars, respectively), consistent with previous studies on LiGluR (23). Scanning over the same region with a Ti:sapphire imaging laser (80-MHz repetition rate, time-averaged intensity < 20 mW/μm 2 ) with wavelengths in the range 800-900 nm produced reversible inward currents with much slower onset (Fig.…”

“…We next sought to validate 2P excitation of MAGs through functional measurements in live cells expressing engineered GluRs. For GluRs engineered to be agonized by the cis isomer, bistable L-MAG0 can mimic the chronic effect of soluble GluR agonists, with the unique feature of very fast and reversible action (23). The strength of MAG agonism is intrinsically limited by the largest population of cis isomers that can be attained, which is defined by the wavelength-dependent photostationary state (PSS).…”

“…3). Dissociated hippocampal neurons were transfected with an hSyn (human synapsin 1) gene promoter driven LiGluR (GluK2-L439C-K456A), where L439C is known to bind L-MAG0 as a cis-activated agonist (21)(22)(23)(24) (Fig. 3A).…”

“…PTLs have since been developed for a variety of other receptors and channels (2). Maleimideazobenzene-glutamate (MAG) compounds are designed to be conjugated to the extracellular ligand binding domains of genetically engineered mammalian glutamate receptors (GluRs), enabling pharmacological manipulation of signaling pathways dependent on the excitatory neurotransmitter glutamate (21)(22)(23)(24)(25). MAGs have been used to study neurotransmission and neuroplasticity in a variety of preparations (26)(27)(28)(29).…”

Holographic optogenetic stimulation of patterned neuronal activity for vision restoration

“…A pattern photo-stimulation system for artificially controlling neural activity in a vision prosthesis or for general neurostimulation applications is not expected to have this limitation (due to minimal light scattering in the inner retinal layers) and will ideally allow cellular-resolution, rapid, massively parallel, light-efficient stimulation across macroscopic (millimeter-scale) coverage areas. To date, however, optical excitation of optogenetically targeted populations is often delivered nonspecifically to the whole population using wide-field flashes with intense lamps 1,3,10 , LEDs (light-emitting diodes) and optical fibre coupled illumination 11,12 or in simple patterns using rapid random-access laser deflection 13,14 , digital micromirror arrays 8,9,[15][16][17][18] and micro-LED arrays 6,19 .…”