Light-controllable tools provide powerful means to manipulate and interrogate brain function with relatively low invasiveness and high spatiotemporal precision. Although optogenetic approaches permit neuronal excitation or inhibition at the network level, other technologies, such as optopharmacology (also known as photopharmacology) have emerged that provide molecular-level control by endowing light sensitivity to endogenous biomolecules. In this Review, we discuss the challenges and opportunities of photocontrolling native neuronal signalling pathways, focusing on ion channels and neurotransmitter receptors. We describe existing strategies for rendering receptors and channels light sensitive and provide an overview of the neuroscientific insights gained from such approaches. At the crossroads of chemistry, protein engineering and neuroscience, optopharmacology offers great potential for understanding the molecular basis of brain function and behaviour, with promises for future therapeutics.
Your institute does not have access to this article
Subscribe to Nature+
Get immediate online access to the entire Nature family of 50+ journals
Subscribe to Journal
Get full journal access for 1 year
only $4.92 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Get time limited or full article access on ReadCube.
All prices are NET prices.
Hille, B. Ionic Channels of Excitable Membranes 3rd edn (Sinauer Associates, 2001).
Lemoine, D. et al. Ligand-gated ion channels: new insights into neurological disorders and ligand recognition. Chem. Rev. 112, 6285–6318 (2012).
Smart, T. G. & Paoletti, P. Synaptic neurotransmitter-gated receptors. Cold Spring Harb. Perspect. Biol. 4, a009662 (2012).
Foster, D. J. & Conn, P. J. Allosteric modulation of GPCRs: new insights and potential utility for treatment of schizophrenia and other CNS disorders. Neuron 94, 431–446 (2017).
Rask-Andersen, M., Almen, M. S. & Schioth, H. B. Trends in the exploitation of novel drug targets. Nat. Rev. Drug Discov. 10, 579–590 (2011).
Coetzee, W. A. et al. Molecular diversity of K+ channels. Ann. NY Acad. Sci. 868, 233–285 (1999).
Engin, E., Benham, R. S. & Rudolph, U. An emerging circuit pharmacology of GABAA receptors. Trends Pharmacol. Sci. 39, 710–732 (2018).
Kramer, R. H., Mourot, A. & Adesnik, H. Optogenetic pharmacology for control of native neuronal signaling proteins. Nat. Neurosci. 16, 816–823 (2013).
Scanziani, M. & Hausser, M. Electrophysiology in the age of light. Nature 461, 930–939 (2009).
Kim, C. K., Adhikari, A. & Deisseroth, K. Integration of optogenetics with complementary methodologies in systems neuroscience. Nat. Rev. Neurosci. 18, 222–235 (2017).
Bartels, E., Wassermann, N. H. & Erlanger, B. F. Photochromic activators of the acetylcholine receptor. Proc. Natl Acad. Sci. USA 68, 1820–1823 (1971).
Lester, H. A., Krouse, M. E., Nass, M. M., Wassermann, N. H. & Erlanger, B. F. Light-activated drug confirms a mechanism of ion channel blockade. Nature 280, 509–510 (1979).
Kaplan, J. H., Forbush, B. 3rd & Hoffman, J. F. Rapid photolytic release of adenosine 5′-triphosphate from a protected analogue: utilization by the Na:K pump of human red blood cell ghosts. Biochemistry 17, 1929–1935 (1978).
Lester, H. A., Krouse, M. E., Nass, M. M., Wassermann, N. H. & Erlanger, B. F. A covalently bound photoisomerizable agonist: comparison with reversibly bound agonists at Electrophorus electroplaques. J. Gen. Physiol. 75, 207–232 (1980).
Ellis-Davies, G. C. Caged compounds: photorelease technology for control of cellular chemistry and physiology. Nat. Methods 4, 619–628 (2007).
Hamouda, A. K., Jayakar, S. S., Chiara, D. C. & Cohen, J. B. Photoaffinity labeling of nicotinic receptors: diversity of drug binding sites! J. Mol. Neurosci. 53, 480–486 (2014).
Berlin, S. & Isacoff, E. Y. Synapses in the spotlight with synthetic optogenetics. EMBO Rep. 18, 677–692 (2017).
Hüll, K., Morstein, J. & Trauner, D. In vivo photopharmacology. Chem. Rev. 118, 10710–10747 (2018).
Ellis-Davies, G. C. R. A chemist and biologist talk to each other about caged neurotransmitters. Beilstein J. Org. Chem. 9, 64–73 (2013).
Ellis-Davies, G. C. R. Two-photon uncaging of glutamate. Front. Synaptic Neurosci. 10, 48 (2019).
Wilcox, M. et al. Synthesis of photolabile precursors of amino acid neurotransmitters. J. Org. Chem. 55, 1585–1589 (1990).
Wieboldt, R. et al. Photolabile precursors of glutamate: synthesis, photochemical properties, and activation of glutamate receptors on a microsecond time scale. Proc. Natl Acad. Sci. USA 91, 8752–8756 (1994).
Matsuzaki, M. et al. Dendritic spine geometry is critical for AMPA receptor expression in hippocampal CA1 pyramidal neurons. Nat. Neurosci. 4, 1086–1092 (2001).
Matsuzaki, M., Honkura, N., Ellis-Davies, G. C. & Kasai, H. Structural basis of long-term potentiation in single dendritic spines. Nature 429, 761–766 (2004). This is the first evidence that LTP (spine growth and an increase in AMPAR current) can be induced at single spines using two-photon glutamate uncaging, in a non-Hebbian manner (that is, not requiring presynaptic release).
Gee, K. R., Wieboldt, R. & Hess, G. P. Synthesis and photochemistry of a new photolabile derivative of GABA-neurotransmitter release and receptor activation in the microsecond time region. J. Am. Chem. Soc. 116, 8366–8367 (1994).
Rial Verde, E. M., Zayat, L., Etchenique, R. & Yuste, R. Photorelease of GABA with visible light using an inorganic caging group. Front. Neural Circuits 2, 2 (2008).
Kantevari, S., Matsuzaki, M., Kanemoto, Y., Kasai, H. & Ellis-Davies, G. C. Two-color, two-photon uncaging of glutamate and GABA. Nat. Methods 7, 123–125 (2010).
Matsuzaki, M., Hayama, T., Kasai, H. & Ellis-Davies, G. C. R. Two-photon uncaging of gamma-aminobutyric acid in intact brain tissue. Nat. Chem. Biol. 6, 255–257 (2010).
Donato, L. et al. Water-soluble, donor-acceptor biphenyl derivatives in the 2-(o-nitrophenyl)propyl series: highly efficient two-photon uncaging of the neurotransmitter gamma-aminobutyric acid at lambda = 800 nm. Angew. Chem. Int. Ed. 51, 1840–1843 (2012).
Araya, R., Andino-Pavlovsky, V., Yuste, R. & Etchenique, R. Two-photon optical interrogation of individual dendritic spines with caged dopamine. ACS Chem. Neurosci. 4, 1163–1167 (2013).
Breitinger, H. G., Wieboldt, R., Ramesh, D., Carpenter, B. K. & Hess, G. P. Synthesis and characterization of photolabile derivatives of serotonin for chemical kinetic investigations of the serotonin 5-HT(3) receptor. Biochemistry 39, 5500–5508 (2000).
Warther, D. et al. Two-photon uncaging: new prospects in neuroscience and cellular biology. Bioorg. Med. Chem. 18, 7753–7758 (2010).
Walker, J. W., McCray, J. A. & Hess, G. P. Photolabile protecting groups for an acetylcholine receptor ligand. Synthesis and photochemistry of a new class of o-nitrobenzyl derivatives and their effects on receptor function. Biochemistry 25, 1799–1805 (1986).
Milburn, T. et al. Synthesis, photochemistry, and biological activity of a caged photolabile acetylcholine receptor ligand. Biochemistry 28, 49–55 (1989).
Banala, S. et al. Photoactivatable drugs for nicotinic optopharmacology. Nat. Methods 15, 347–350 (2018).
Passlick, S., Thapaliya, E. R., Chen, Z., Richers, M. T. & Ellis-Davies, G. C. R. Optical probing of acetylcholine receptors on neurons in the medial habenula with a novel caged nicotine drug analogue. J. Physiol. 596, 5307–5318 (2018).
Niu, L., Wieboldt, R., Ramesh, D., Carpenter, B. K. & Hess, G. P. Synthesis and characterization of a caged receptor ligand suitable for chemical kinetic investigations of the glycine receptor in the 3-microseconds time domain. Biochemistry 35, 8136–8142 (1996).
Gee, K. R., Niu, L., Schaper, K., Jayaraman, V. & Hess, G. P. Synthesis and photochemistry of a photolabile precursor of N-methyl-D-aspartate (NMDA) that is photolyzed in the microsecond time region and is suitable for chemical kinetic investigations of the NMDA receptor. Biochemistry 38, 3140–3147 (1999).
Palma-Cerda, F. et al. New caged neurotransmitter analogs selective for glutamate receptor sub-types based on methoxynitroindoline and nitrophenylethoxycarbonyl caging groups. Neuropharmacology 63, 624–634 (2012).
Niu, L., Gee, K. R., Schaper, K. & Hess, G. P. Synthesis and photochemical properties of a kainate precursor and activation of kainate and AMPA receptor channels on a microsecond time scale. Biochemistry 35, 2030–2036 (1996).
Banghart, M. R. & Sabatini, B. L. Photoactivatable neuropeptides for spatiotemporally precise delivery of opioids in neural tissue. Neuron 73, 249–259 (2012).
Banghart, M. R., Williams, J. T., Shah, R. C., Lavis, L. D. & Sabatini, B. L. Caged naloxone reveals opioid signaling deactivation kinetics. Mol. Pharmacol. 84, 687–695 (2013).
Banghart, M. R., He, X. J. & Sabatini, B. L. A. Caged enkephalin optimized for simultaneously probing mu and delta opioid receptors. ACS Chem. Neurosci. 9, 684–690 (2018).
Volgraf, M. et al. Reversibly caged glutamate: a photochromic agonist of ionotropic glutamate receptors. J. Am. Chem. Soc. 129, 260–261 (2007).
Banghart, M. R. et al. Photochromic blockers of voltage-gated potassium channels. Angew. Chem. Int. Ed. 48, 9097–9101 (2009).
Izquierdo-Serra, M. et al. Optical control of endogenous receptors and cellular excitability using targeted covalent photoswitches. Nat. Commun. 7, 12221 (2016).
Szymanski, W., Yilmaz, D., Kocer, A. & Feringa, B. L. Bright ion channels and lipid bilayers. Acc. Chem. Res. 46, 2910–2923 (2013).
Broichhagen, J. & Trauner, D. The in vivo chemistry of photoswitched tethered ligands. Curr. Opin. Chem. Biol. 21, 121–127 (2014).
Reiner, A., Levitz, J. & Isacoff, E. Y. Controlling ionotropic and metabotropic glutamate receptors with light: principles and potential. Curr. Opin. Pharmacol. 20, 135–143 (2015).
Fortin, D. L. et al. Photochemical control of endogenous ion channels and cellular excitability. Nat. Methods 5, 331–338 (2008).
Mourot, A. et al. Tuning photochromic ion channel blockers. ACS Chem. Neurosci. 2, 536–543 (2011).
Mourot, A. et al. Rapid optical control of nociception with an ion-channel photoswitch. Nat. Methods 9, 396–402 (2012). In this paper, a light-controllable lidocaine derivative was developed and targeted to pain-sensing neurons without requiring genetic modification, allowing photocontrol of pain signalling in living rats.
Schonberger, M., Althaus, M., Fronius, M., Clauss, W. & Trauner, D. Controlling epithelial sodium channels with light using photoswitchable amilorides. Nat. Chem. 6, 712–719 (2014).
Fehrentz, T. et al. Optical control of L-type Ca(2+) channels using a diltiazem photoswitch. Nat. Chem. Biol. 14, 764–767 (2018).
Barber, D. M. et al. Optical control of neuronal activity using a light-operated GIRK channel opener (LOGO). Chem. Sci. 7, 2347–2352 (2016).
Leippe, P., Winter, N., Sumser, M. P. & Trauner, D. Optical control of a delayed rectifier and a two-pore potassium channel with a photoswitchable bupivacaine. ACS Chem. Neurosci. 9, 2886–2891 (2018).
Broichhagen, J. et al. Optical control of insulin release using a photoswitchable sulfonylurea. Nat. Commun. 5, 5116 (2014).
Stein, M., Breit, A., Fehrentz, T., Gudermann, T. & Trauner, D. Optical control of TRPV1 channels. Angew. Chem. Int. Ed. 52, 9845–9848 (2013).
Stawski, P., Sumser, M. & Trauner, D. A photochromic agonist of AMPA receptors. Angew. Chem. Int. Ed. 51, 5748–5751 (2012).
Laprell, L. et al. Optical control of NMDA receptors with a diffusible photoswitch. Nat. Commun. 6, 8076 (2015).
Laprell, L. et al. Restoring light sensitivity in blind retinae using a photochromic AMPA receptor agonist. ACS Chem. Neurosci. 7, 15–20 (2016).
Barber, D. M. et al. Optical control of AMPA receptors using a photoswitchable quinoxaline-2,3-dione antagonist. Chem. Sci. 8, 611–615 (2017).
Damijonaitis, A. et al. AzoCholine enables optical control of alpha 7 nicotinic acetylcholine receptors in neural networks. ACS Chem. Neurosci. 6, 701–707 (2015).
Bahamonde, M. I. et al. Photomodulation of G protein-coupled adenosine receptors by a novel light-switchable ligand. Bioconjug. Chem. 25, 1847–1854 (2014).
Huckvale, R., Mortensen, M., Pryde, D., Smart, T. G. & Baker, J. R. Azogabazine; a photochromic antagonist of the GABAA receptor. Org. Biomol. Chem. 14, 6676–6678 (2016).
Pittolo, S. et al. An allosteric modulator to control endogenous G protein-coupled receptors with light. Nat. Chem. Biol. 10, 813–815 (2014). This paper describes the first development of a light-controllable allosteric modulator for GPCRs, used to control locomotion in tadpoles.
Rovira, X. et al. OptoGluNAM4.1, a photoswitchable allosteric antagonist for real-time control of mGlu4 receptor activity. Cell Chem. Biol 23, 929–934 (2016).
Gomez-Santacana, X. et al. Illuminating phenylazopyridines to photoswitch metabotropic glutamate receptors: from the flask to the animals. ACS Cent. Sci. 3, 81–91 (2017).
Zussy, C. et al. Dynamic modulation of inflammatory pain-related affective and sensory symptoms by optical control of amygdala metabotropic glutamate receptor 4. Mol. Psychiatry 23, 509–520 (2018).
Bossi, S. et al. A light-controlled allosteric modulator unveils a role for mGlu4 receptors during early stages of ischemia in the rodent cerebellar cortex. Front. Cell. Neurosci. 12, 449 (2018).
Stein, M. et al. Azo-propofols: photochromic potentiators of GABA(A) receptors. Angew. Chem. Int. Ed. 51, 10500–10504 (2012).
Yue, L. et al. Robust photoregulation of GABA(A) receptors by allosteric modulation with a propofol analogue. Nat. Commun. 3, 1095 (2012).
Beharry, A. A. & Woolley, G. A. Azobenzene photoswitches for biomolecules. Chem. Soc. Rev. 40, 4422–4437 (2011).
Broichhagen, J., Frank, J. A. & Trauner, D. A roadmap to success in photopharmacology. Acc. Chem. Res. 48, 1947–1960 (2015).
Lin, W. C., Tsai, M. C., Rajappa, R. & Kramer, R. H. Design of a highly bistable photoswitchable tethered ligand for rapid and sustained manipulation of neurotransmission. J. Am. Chem. Soc. 140, 7445–7448 (2018).
Samanta, S., Qin, C., Lough, A. J. & Woolley, G. A. Bidirectional photocontrol of peptide conformation with a bridged azobenzene derivative. Angew. Chem. Int. Ed. 51, 6452–6455 (2012).
Thapaliya, E. R., Zhao, J. & Ellis-Davies, G. C. R. Locked-azobenzene: testing the scope of a unique photoswitchable scaffold for cell physiology. ACS Chem. Neurosci. 10, 2481–2488 (2019).
Chi, L., Sadovski, O. & Woolley, G. A. A blue-green absorbing cross-linker for rapid photoswitching of peptide helix content. Bioconjug. Chem. 17, 670–676 (2006).
Samanta, S. et al. Photoswitching azo compounds in vivo with red light. J. Am. Chem. Soc. 135, 9777–9784 (2013).
Kienzler, M. A. et al. A red-shifted, fast-relaxing azobenzene photoswitch for visible light control of an ionotropic glutamate receptor. J. Am. Chem. Soc. 135, 17683–17686 (2013).
Rullo, A. et al. Long wavelength optical control of glutamate receptor ion channels using a tetra-ortho-substituted azobenzene derivative. Chem. Commun. 50, 14613–14615 (2014).
Hoppmann, C., Maslennikov, I., Choe, S. & Wang, L. In situ formation of an azo bridge on proteins controllable by visible light. J. Am. Chem. Soc. 137, 11218–11221 (2015).
Dong, M., Babalhavaeji, A., Samanta, S., Beharry, A. A. & Woolley, G. A. Red-shifting azobenzene photoswitches for in vivo use. Acc. Chem. Res. 48, 2662–2670 (2015).
Dong, M. et al. Near-infrared photoswitching of azobenzenes under physiological conditions. J. Am. Chem. Soc. 139, 13483–13486 (2017).
Passlick, S., Richers, M. T. & Ellis-Davies, G. C. R. Thermodynamically stable, photoreversible pharmacology in neurons with one- and two-photon excitation. Angew. Chem. Int. Ed. 57, 12554–12557 (2018).
Borowiak, M. et al. Photoswitchable inhibitors of microtubule dynamics optically control mitosis and cell death. Cell 162, 403–411 (2015).
Gorostiza, P. et al. Mechanisms of photoswitch conjugation and light activation of an ionotropic glutamate receptor. Proc. Natl Acad. Sci. USA 104, 10865–10870 (2007).
Mourot, A., Tochitsky, I. & Kramer, R. H. Light at the end of the channel: optical manipulation of intrinsic neuronal excitability with chemical photoswitches. Front. Mol. Neurosci. 6, 5 (2013).
Schoenberger, M., Damijonaitis, A., Zhang, Z., Nagel, D. & Trauner, D. Development of a new photochromic ion channel blocker via azologization of fomocaine. ACS Chem. Neurosci. 5, 514–518 (2014).
Kocer, A., Walko, M., Meijberg, W. & Feringa, B. L. A light-actuated nanovalve derived from a channel protein. Science 309, 755–758 (2005).
Lachmann, D. et al. Photochromic dopamine receptor ligands based on dithienylethenes and fulgides. Chemistry 23, 13423–13434 (2017).
Ruiz, M. L. & Karpen, J. W. Single cyclic nucleotide-gated channels locked in different ligand-bound states. Nature 389, 389–392 (1997). This paper reports the clever use of PALs to trap channel receptors in partially liganded states. Single-channel recordings were used to correlate ligand binding to channel gating.
Adesnik, H., Nicoll, R. A. & England, P. M. Photoinactivation of native AMPA receptors reveals their real-time trafficking. Neuron 48, 977–985 (2005).
Mortensen, M. et al. Photo-antagonism of the GABAA receptor. Nat. Commun. 5, 4454 (2014).
Huber, T. & Sakmar, T. P. Chemical biology methods for investigating G protein-coupled receptor signaling. Chem. Biol. 21, 1224–1237 (2014).
Jay, D. G. Selective destruction of protein function by chromophore-assisted laser inactivation. Proc. Natl Acad. Sci. USA 85, 5454–5458 (1988).
Sano, Y., Watanabe, W. & Matsunaga, S. Chromophore-assisted laser inactivation—towards a spatiotemporal-functional analysis of proteins, and the ablation of chromatin, organelle and cell function. J. Cell Sci. 127, 1621–1629 (2014).
Takemoto, K. et al. Optical inactivation of synaptic AMPA receptors erases fear memory. Nat. Biotechnol. 35, 38–47 (2017). This paper shows that precise inactivation of endogenous AMPARs at specific synapses using CALI affects memory formation.
Goglia, A. G. & Toettcher, J. E. A bright future: optogenetics to dissect the spatiotemporal control of cell behavior. Curr. Opin. Chem. Biol. 48, 106–113 (2018).
Spangler, S. M. & Bruchas, M. R. Optogenetic approaches for dissecting neuromodulation and GPCR signaling in neural circuits. Curr. Opin. Pharmacol. 32, 56–70 (2017).
Kim, J. M. et al. Light-driven activation of beta 2-adrenergic receptor signaling by a chimeric rhodopsin containing the beta 2-adrenergic receptor cytoplasmic loops. Biochemistry 44, 2284–2292 (2005).
Airan, R. D., Thompson, K. R., Fenno, L. E., Bernstein, H. & Deisseroth, K. Temporally precise in vivo control of intracellular signalling. Nature 458, 1025–1029 (2009).
Siuda, E. R. et al. Optodynamic simulation of beta-adrenergic receptor signalling. Nat. Commun. 6, 8480 (2015).
Li, P. et al. Optogenetic activation of intracellular adenosine A2A receptor signaling in the hippocampus is sufficient to trigger CREB phosphorylation and impair memory. Mol. Psychiatry 20, 1339–1349 (2015).
Barish, P. A. et al. Design and functional evaluation of an optically active mu-opioid receptor. Eur. J. Pharmacol. 705, 42–48 (2013).
Siuda, E. R. et al. Spatiotemporal control of opioid signaling and behavior. Neuron 86, 923–935 (2015). The authors of this paper developed an opioid receptor–rhodopsin chimera. Light was used to mimic opioid signalling at specific synapses and to manipulate mouse behaviour.
van Wyk, M., Pielecka-Fortuna, J., Lowel, S. & Kleinlogel, S. Restoring the ON switch in blind retinas: opto-mGluR6, a next-generation, cell-tailored optogenetic tool. PLOS Biol. 13, e1002143 (2015).
Gunaydin, L. A. et al. Natural neural projection dynamics underlying social behavior. Cell 157, 1535–1551 (2014).
Oh, E., Maejima, T., Liu, C., Deneris, E. & Herlitze, S. Substitution of 5-HT1A receptor signaling by a light-activated G protein-coupled receptor. J. Biol. Chem. 285, 30825–30836 (2010).
Spoida, K., Masseck, O. A., Deneris, E. S. & Herlitze, S. Gq/5-HT2c receptor signals activate a local GABAergic inhibitory feedback circuit to modulate serotonergic firing and anxiety in mice. Proc. Natl Acad. Sci. USA 111, 6479–6484 (2014).
Masseck, O. A. et al. Vertebrate cone opsins enable sustained and highly sensitive rapid control of Gi/o signaling in anxiety circuitry. Neuron 81, 1263–1273 (2014).
Morri, M. et al. Optical functionalization of human Class A orphan G-protein-coupled receptors. Nat. Commun. 9, 1950 (2018).
Rost, B. R., Schneider-Warme, F., Schmitz, D. & Hegemann, P. Optogenetic tools for subcellular applications in neuroscience. Neuron 96, 572–603 (2017).
Schmidt, D., Tillberg, P. W., Chen, F. & Boyden, E. S. A fully genetically encoded protein architecture for optical control of peptide ligand concentration. Nat. Commun. 5, 3019 (2014).
He, L. et al. Near-infrared photoactivatable control of Ca(2+) signaling and optogenetic immunomodulation. eLife 4, e10024 (2015).
Ma, G. et al. Optogenetic control of voltage-gated calcium channels. Angew. Chem. Int. Ed. 57, 7019–7022 (2018).
Wu, Y. I. et al. A genetically encoded photoactivatable Rac controls the motility of living cells. Nature 461, 104–108 (2009).
Dietz, D. M. et al. Rac1 is essential in cocaine-induced structural plasticity of nucleus accumbens neurons. Nat. Neurosci. 15, 891–896 (2012).
Hayashi-Takagi, A. et al. Labelling and optical erasure of synaptic memory traces in the motor cortex. Nature 525, 333–338 (2015). This article shows a direct link between synaptic plasticity (dendritic spine formation) and memory storage, using a light-controllable RHO-GTPase.
O’Neill, P. R. & Gautam, N. Subcellular optogenetic inhibition of G proteins generates signaling gradients and cell migration. Mol. Biol. Cell 25, 2305–2314 (2014).
Liu, Q. et al. A photoactivatable botulinum neurotoxin for inducible control of neurotransmission. Neuron 101, 863–875 (2019).
Cosentino, C. et al. Optogenetics. Engineering of a light-gated potassium channel. Science 348, 707–710 (2015).
Grusch, M. et al. Spatio-temporally precise activation of engineered receptor tyrosine kinases by light. EMBO J. 33, 1713–1726 (2014).
Chang, K. Y. et al. Light-inducible receptor tyrosine kinases that regulate neurotrophin signalling. Nat. Commun. 5, 4057 (2014).
Sinnen, B. L. et al. Optogenetic control of synaptic composition and function. Neuron 93, 646–660 (2017). This paper describes a novel optogenetic approach to alter the molecular content of synapses. Intriguingly, light-induced recruitment of AMPARs affected the frequency, but not the amplitude, of synaptic events.
Tour, O., Meijer, R. M., Zacharias, D. A., Adams, S. R. & Tsien, R. Y. Genetically targeted chromophore-assisted light inactivation. Nat. Biotechnol. 21, 1505–1508 (2003).
Lin, J. Y. et al. Optogenetic inhibition of synaptic release with chromophore-assisted light inactivation (CALI). Neuron 79, 241–253 (2013).
Noren, C. J., Anthony-Cahill, S. J., Griffith, M. C. & Schultz, P. G. A general method for site-specific incorporation of unnatural amino acids into proteins. Science 244, 182–188 (1989).
Liu, C. C. & Schultz, P. G. Adding new chemistries to the genetic code. Annu. Rev. Biochem. 79, 413–444 (2010).
Chin, J. W. Expanding and reprogramming the genetic code. Nature 550, 53–60 (2017).
Beene, D. L., Dougherty, D. A. & Lester, H. A. Unnatural amino acid mutagenesis in mapping ion channel function. Curr. Opin. Neurobiol. 13, 264–270 (2003).
Klippenstein, V., Mony, L. & Paoletti, P. Probing ion channel structure and function using light-sensitive amino acids. Trends Biochem. Sci. 43, 436–451 (2018).
Miller, J. C., Silverman, S. K., England, P. M., Dougherty, D. A. & Lester, H. A. Flash decaging of tyrosine sidechains in an ion channel. Neuron 20, 619–624 (1998).
Philipson, K. D., Gallivan, J. P., Brandt, G. S., Dougherty, D. A. & Lester, H. A. Incorporation of caged cysteine and caged tyrosine into a transmembrane segment of the nicotinic ACh receptor. Am. J. Physiol. Cell Physiol. 281, C195–C206 (2001).
Kang, J. Y. et al. In vivo expression of a light-activatable potassium channel using unnatural amino acids. Neuron 80, 358–370 (2013).
Banghart, M., Borges, K., Isacoff, E., Trauner, D. & Kramer, R. H. Light-activated ion channels for remote control of neuronal firing. Nat. Neurosci. 7, 1381–1386 (2004). This pioneering paper reports the first rational engineering of a light-controllable protein by installing a photoswitchable ligand onto a cysteine-substituted K + channel and the demonstration of optogenetic control of action potential firing in cultured neurons.
Volgraf, M. et al. Allosteric control of an ionotropic glutamate receptor with an optical switch. Nat. Chem. Biol. 2, 47–52 (2006).
Broichhagen, J. et al. Orthogonal optical control of a G protein-coupled receptor with a SNAP-tethered photochromic ligand. ACS Cent. Sci. 1, 383–393 (2015).
Levitz, J. et al. Dual optical control and mechanistic insights into photoswitchable group II and III metabotropic glutamate receptors. Proc. Natl Acad. Sci. USA 114, E3546–E3554 (2017).
Farrants, H. et al. SNAP-tagged nanobodies enable reversible optical control of a G protein-coupled receptor via a remotely tethered photoswitchable ligand. ACS Chem. Biol. 13, 2682–2688 (2018).
Browne, L. E. et al. Optical control of trimeric P2X receptors and acid-sensing ion channels. Proc. Natl Acad. Sci. USA 111, 521–526 (2014).
Habermacher, C. et al. Photo-switchable tweezers illuminate pore-opening motions of an ATP-gated P2X ion channel. eLife 5, e11050 (2016).
Harkat, M. et al. On the permeation of large organic cations through the pore of ATP-gated P2X receptors. Proc. Natl Acad. Sci. USA 114, E3786–E3795 (2017).
Fortin, D. L. et al. Optogenetic photochemical control of designer K+ channels in mammalian neurons. J. Neurophysiol. 106, 488–496 (2011).
Sandoz, G., Levitz, J., Kramer, R. H. & Isacoff, E. Y. Optical control of endogenous proteins with a photoswitchable conditional subunit reveals a role for TREK1 in GABA(B) signaling. Neuron 74, 1005–1014 (2012).
Levitz, J. et al. Optical control of metabotropic glutamate receptors. Nat. Neurosci. 16, 507–516 (2013). This paper documents the extension of the PTL technology to GPCRs — specifically, the engineering of agonized and antagonized versions of metabotropic glutamate receptors.
Berlin, S. et al. A family of photoswitchable NMDA receptors. eLife 5, e12040 (2016).
Tochitsky, I. et al. Optochemical control of genetically engineered neuronal nicotinic acetylcholine receptors. Nat. Chem. 4, 105–111 (2012).
Lin, W. C. et al. Engineering a light-regulated GABAA receptor for optical control of neural inhibition. ACS Chem. Biol. 9, 1414–1419 (2014).
Lin, W. C. et al. A comprehensive optogenetic pharmacology toolkit for in vivo control of GABA(A) receptors and synaptic inhibition. Neuron 88, 879–891 (2015). This paper documents the first use of the PTL technology in the brain of living mice and the first development of transgenic mice expressing a cysteine-substituted receptor for optopharmacology.
Lemoine, D. et al. Optical control of an ion channel gate. Proc. Natl Acad. Sci. USA 110, 20813–20818 (2013).
Donthamsetti, P. C. et al. Optical control of dopamine receptors using a photoswitchable tethered inverse agonist. J. Am. Chem. Soc. 139, 18522–18535 (2017).
Reiner, A. & Isacoff, E. Y. Tethered ligands reveal glutamate receptor desensitization depends on subunit occupancy. Nat. Chem. Biol. 10, 273–280 (2014). This paper reports the clever use of the PTL technology to optically ‘clamp’ ligands in their binding pocket, to study the relationship between binding, gating and desensitization.
Li, G. D. et al. Identification of a GABAA receptor anesthetic binding site at subunit interfaces by photolabeling with an etomidate analog. J. Neurosci. 26, 11599–11605 (2006).
Yip, G. M. et al. A propofol binding site on mammalian GABAA receptors identified by photolabeling. Nat. Chem. Biol. 9, 715–720 (2013).
Valentin-Hansen, L. et al. Mapping substance P binding sites on the neurokinin-1 receptor using genetic incorporation of a photoreactive amino acid. J. Biol. Chem. 289, 18045–18054 (2014).
Coin, I. et al. Genetically encoded chemical probes in cells reveal the binding path of urocortin-I to CRF class B GPCR. Cell 155, 1258–1269 (2013).
Simms, J. et al. Photoaffinity cross-linking and unnatural amino acid mutagenesis reveal insights into calcitonin gene-related peptide binding to the calcitonin receptor-like receptor/receptor activity-modifying protein 1 (CLR/RAMP1) complex. Biochemistry 57, 4915–4922 (2018).
Murray, C. I. et al. Unnatural amino acid photo-crosslinking of the IKs channel complex demonstrates a KCNE1:KCNQ1 stoichiometry of up to 4:4. eLife 5, e11815 (2016).
Westhoff, M., Murray, C. I., Eldstrom, J. & Fedida, D. Photo-cross-linking of IKs demonstrates state-dependent interactions between KCNE1 and KCNQ1. Biophys. J. 113, 415–425 (2017).
Klippenstein, V., Ghisi, V., Wietstruk, M. & Plested, A. J. Photoinactivation of glutamate receptors by genetically encoded unnatural amino acids. J. Neurosci. 34, 980–991 (2014).
Zhu, S. et al. Genetically encoding a light switch in an ionotropic glutamate receptor reveals subunit-specific interfaces. Proc. Natl Acad. Sci. USA 111, 6081–6086 (2014).
Tian, M. & Ye, S. Allosteric regulation in NMDA receptors revealed by the genetically encoded photo-cross-linkers. Sci. Rep. 6, 34751 (2016).
Klippenstein, V., Hoppmann, C., Ye, S., Wang, L. & Paoletti, P. Optocontrol of glutamate receptor activity by single side-chain photoisomerization. eLife 6, e25808 (2017). In this study, unnatural PSAAs were incorporated at key locations in NMDARs; robust photoregulation of receptor activity was observed upon subtle structural changes of the protein.
Matsubara, N., Billington, A. P. & Hess, G. P. How fast does an acetylcholine receptor channel open? Laser-pulse photolysis of an inactive precursor of carbamoylcholine in the microsecond time region with BC3H1 cells. Biochemistry 31, 5507–5514 (1992).
DiGregorio, D. A., Rothman, J. S., Nielsen, T. A. & Silver, R. A. Desensitization properties of AMPA receptors at the cerebellar mossy fiber granule cell synapse. J. Neurosci. 27, 8344–8357 (2007).
Levitz, J. et al. Mechanism of assembly and cooperativity of homomeric and heteromeric metabotropic glutamate receptors. Neuron 92, 143–159 (2016).
Eder, M., Zieglgansberger, W. & Dodt, H. U. Shining light on neurons—elucidation of neuronal functions by photostimulation. Rev. Neurosci 15, 167–183 (2004).
Shepherd, G. M. Circuit mapping by ultraviolet uncaging of glutamate. Cold Spring Harb. Protoc 2012, 998–1004 (2012).
Callaway, E. M. & Katz, L. C. Photostimulation using caged glutamate reveals functional circuitry in living brain slices. Proc. Natl Acad. Sci. USA 90, 7661–7665 (1993).
Denk, W. Two-photon scanning photochemical microscopy: mapping ligand-gated ion channel distributions. Proc. Natl Acad. Sci. USA 91, 6629–6633 (1994).
Khiroug, L., Giniatullin, R., Klein, R. C., Fayuk, D. & Yakel, J. L. Functional mapping and Ca2+ regulation of nicotinic acetylcholine receptor channels in rat hippocampal CA1 neurons. J. Neurosci. 23, 9024–9031 (2003).
Ko, K. W., Rasband, M. N., Meseguer, V., Kramer, R. H. & Golding, N. L. Serotonin modulates spike probability in the axon initial segment through HCN channels. Nat. Neurosci. 19, 826–834 (2016).
Patterson, M. A., Szatmari, E. M. & Yasuda, R. AMPA receptors are exocytosed in stimulated spines and adjacent dendrites in a Ras-ERK-dependent manner during long-term potentiation. Proc. Natl Acad. Sci. USA 107, 15951–15956 (2010).
Lee, S. J., Escobedo-Lozoya, Y., Szatmari, E. M. & Yasuda, R. Activation of CaMKII in single dendritic spines during long-term potentiation. Nature 458, 299–304 (2009).
Harvey, C. D., Yasuda, R., Zhong, H. & Svoboda, K. The spread of Ras activity triggered by activation of a single dendritic spine. Science 321, 136–140 (2008).
Murakoshi, H., Wang, H. & Yasuda, R. Local, persistent activation of Rho GTPases during plasticity of single dendritic spines. Nature 472, 100–104 (2011).
Hedrick, N. G. et al. Rho GTPase complementation underlies BDNF-dependent homo- and heterosynaptic plasticity. Nature 538, 104–108 (2016).
Zhai, S., Ark, E. D., Parra-Bueno, P. & Yasuda, R. Long-distance integration of nuclear ERK signaling triggered by activation of a few dendritic spines. Science 342, 1107–1111 (2013).
Yasuda, R. Biophysics of biochemical signaling in dendritic spines: implications in synaptic plasticity. Biophys. J. 113, 2152–2159 (2017).
Schiller, J., Major, G., Koester, H. J. & Schiller, Y. NMDA spikes in basal dendrites of cortical pyramidal neurons. Nature 404, 285–289 (2000).
Losonczy, A. & Magee, J. C. Integrative properties of radial oblique dendrites in hippocampal CA1 pyramidal neurons. Neuron 50, 291–307 (2006).
Noguchi, J., Matsuzaki, M., Ellis-Davies, G. C. & Kasai, H. Spine-neck geometry determines NMDA receptor-dependent Ca2+ signaling in dendrites. Neuron 46, 609–622 (2005).
Branco, T., Clark, B. A. & Hausser, M. Dendritic discrimination of temporal input sequences in cortical neurons. Science 329, 1671–1675 (2010).
Rall, W., Burke, R. E., Smith, T. G., Nelson, P. G. & Frank, K. Dendritic location of synapses and possible mechanisms for the monosynaptic EPSP in motoneurons. J. Neurophysiol. 30, 1169–1193 (1967).
Kauwe, G. & Isacoff, E. Y. Rapid feedback regulation of synaptic efficacy during high-frequency activity at the Drosophila larval neuromuscular junction. Proc. Natl Acad. Sci. USA 110, 9142–9147 (2013).
Li, D., Herault, K., Isacoff, E. Y., Oheim, M. & Ropert, N. Optogenetic activation of LiGluR-expressing astrocytes evokes anion channel-mediated glutamate release. J. Physiol 590, 855–873 (2012).
Zhang, Y. P., Holbro, N. & Oertner, T. G. Optical induction of plasticity at single synapses reveals input-specific accumulation of alphaCaMKII. Proc. Natl Acad. Sci. USA 105, 12039–12044 (2008).
Chiu, C. Q. et al. Compartmentalization of GABAergic inhibition by dendritic spines. Science 340, 759–762 (2013).
Hayama, T. et al. GABA promotes the competitive selection of dendritic spines by controlling local Ca2+ signaling. Nat. Neurosci. 16, 1409–1416 (2013).
Yagishita, S. et al. A critical time window for dopamine actions on the structural plasticity of dendritic spines. Science 345, 1616–1620 (2014).
Olson, J. P. et al. Optically selective two-photon uncaging of glutamate at 900 nm. J. Am. Chem. Soc. 135, 5954–5957 (2013).
Amatrudo, J. M. et al. Wavelength-selective one- and two-photon uncaging of GABA. ACS Chem. Neurosci. 5, 64–70 (2014).
Olson, J. P., Banghart, M. R., Sabatini, B. L. & Ellis-Davies, G. C. Spectral evolution of a photochemical protecting group for orthogonal two-color uncaging with visible light. J. Am. Chem. Soc. 135, 15948–15954 (2013).
Agarwal, H. K., Zhai, S., Surmeier, D. J. & Ellis-Davies, G. C. R. Intracellular uncaging of cGMP with blue light. ACS Chem. Neurosci. 8, 2139–2144 (2017).
Amatrudo, J. M., Olson, J. P., Agarwal, H. K. & Ellis-Davies, G. C. Caged compounds for multichromic optical interrogation of neural systems. Eur. J. Neurosci. 41, 5–16 (2015).
Herrera, C. G. & Adamantidis, A. R. An integrated microprobe for the brain. Nat. Biotechnol. 33, 259–260 (2015).
Canales, A., Park, S., Kilias, A. & Anikeeva, P. Multifunctional fibers as tools for neuroscience and neuroengineering. Acc. Chem. Res. 51, 829–838 (2018).
Kokel, D. et al. Photochemical activation of TRPA1 channels in neurons and animals. Nat. Chem. Biol. 9, 257–263 (2013).
Noguchi, J. et al. In vivo two-photon uncaging of glutamate revealing the structure-function relationships of dendritic spines in the neocortex of adult mice. J. Physiol 589, 2447–2457 (2011).
Font, J. et al. Optical control of pain in vivo with a photoactive mGlu5 receptor negative allosteric modulator. eLife 6, e23545 (2017).
Polosukhina, A. et al. Photochemical restoration of visual responses in blind mice. Neuron 75, 271–282 (2012).
Tochitsky, I. et al. Restoring visual function to blind mice with a photoswitch that exploits electrophysiological remodeling of retinal ganglion cells. Neuron 81, 800–813 (2014). This paper demonstrates that vision can be restored in mice in which photoreceptors have degenerated, using a small diffusible photoswitch that operates with visible light.
Tochitsky, I. et al. How azobenzene photoswitches restore visual responses to the blind retina. Neuron 92, 100–113 (2016).
Tochitsky, I., Trautman, J., Gallerani, N., Malis, J. G. & Kramer, R. H. Restoring visual function to the blind retina with a potent, safe and long-lasting photoswitch. Sci. Rep. 7, 45487 (2017).
Tochitsky, I., Kienzler, M. A., Isacoff, E. & Kramer, R. H. Restoring vision to the blind with chemical photoswitches. Chem. Rev. 118, 10748–10773 (2018).
Trusel, M. et al. Punishment-predictive cues guide avoidance through potentiation of hypothalamus-to-habenula synapses. Neuron 102, 120–127 (2019).
Levitz, J., Popescu, A. T., Reiner, A. & Isacoff, E. Y. A. Toolkit for orthogonal and in vivo optical manipulation of ionotropic glutamate receptors. Front. Mol. Neurosci. 9, 2 (2016).
Durand-de Cuttoli, R. et al. Manipulating midbrain dopamine neurons and reward-related behaviors with light-controllable nicotinic acetylcholine receptors. eLife 7, e37487 (2018). This paper describes the first demonstration of the PTL technology in freely behaving mice; the technology enabled reversible control of nicotinic transmission in mice in vivo.
Szobota, S. et al. Remote control of neuronal activity with a light-gated glutamate receptor. Neuron 54, 535–545 (2007).
Wyart, C. et al. Optogenetic dissection of a behavioural module in the vertebrate spinal cord. Nature 461, 407–410 (2009).
Janovjak, H., Szobota, S., Wyart, C., Trauner, D. & Isacoff, E. Y. A light-gated, potassium-selective glutamate receptor for the optical inhibition of neuronal firing. Nat. Neurosci. 13, 1027–1032 (2010).
Caporale, N. et al. LiGluR restores visual responses in rodent models of inherited blindness. Mol. Ther. 19, 1212–1219 (2011).
Gaub, B. M. et al. Restoration of visual function by expression of a light-gated mammalian ion channel in retinal ganglion cells or ON-bipolar cells. Proc. Natl Acad. Sci. USA 111, E5574–E5583 (2014).
Berry, M. H. et al. Restoration of patterned vision with an engineered photoactivatable G protein-coupled receptor. Nat. Commun. 8, 1862 (2017).
Izquierdo-Serra, M. et al. Two-photon neuronal and astrocytic stimulation with azobenzene-based photoswitches. J. Am. Chem. Soc. 136, 8693–8701 (2014).
Gascon-Moya, M. et al. An optimized glutamate receptor photoswitch with sensitized azobenzene isomerization. J. Org. Chem. 80, 9915–9925 (2015).
Carroll, E. C. et al. Two-photon brightness of azobenzene photoswitches designed for glutamate receptor optogenetics. Proc. Natl Acad. Sci. USA 112, E776–E785 (2015).
Cabre, G. et al. Rationally designed azobenzene photoswitches for efficient two-photon neuronal excitation. Nat. Commun. 10, 907 (2019).
Ernst, R. J. et al. Genetic code expansion in the mouse brain. Nat. Chem. Biol. 12, 776–778 (2016).
Han, S. et al. Expanding the genetic code of Mus musculus. Nat. Commun. 8, 14568 (2017).
Zheng, Y. et al. Virus-enabled optimization and delivery of the genetic machinery for efficient unnatural amino acid mutagenesis in mammalian cells and tissues. ACS Synth. Biol. 6, 13–18 (2017).
Chen, Y. et al. Heritable expansion of the genetic code in mouse and zebrafish. Cell Res. 27, 294–297 (2017).
Tufail, Y. et al. Transcranial pulsed ultrasound stimulates intact brain circuits. Neuron 66, 681–694 (2010).
Nimpf, S. & Keays, D. A. Is magnetogenetics the new optogenetics? EMBO J. 36, 1643–1646 (2017).
Lerch, M. M., Hansen, M. J., van Dam, G. M., Szymanski, W. & Feringa, B. L. Emerging targets in photopharmacology. Angew. Chem. Int. Ed. 55, 10978–10999 (2016).
Laprell, L. et al. Photopharmacological control of bipolar cells restores visual function in blind mice. J. Clin. Invest 127, 2598–2611 (2017).
Roska, B. & Sahel, J. A. Restoring vision. Nature 557, 359–367 (2018).
US National Library of Medicine. ClinicalTrials.gov https://clinicaltrials.gov/ct2/show/NCT02556736 (2019).
Basbaum, A. I., Bautista, D. M., Scherrer, G. & Julius, D. Cellular and molecular mechanisms of pain. Cell 139, 267–284 (2009).
Frank, J. A. et al. Photoswitchable fatty acids enable optical control of TRPV1. Nat. Commun. 6, 7118 (2015).
Schonberger, M. & Trauner, D. A photochromic agonist for mu-opioid receptors. Angew. Chem. Int. Ed. 53, 3264–3267 (2014).
Mourot, A., Herold, C., Kienzler, M. A. & Kramer, R. H. Understanding and improving photo-control of ion channels in nociceptors with azobenzene photo-switches. Br. J. Pharmacol. 175, 2296–2311 (2018).
Kim, T. I. et al. Injectable, cellular-scale optoelectronics with applications for wireless optogenetics. Science 340, 211–216 (2013).
Montgomery, K. L. et al. Wirelessly powered, fully internal optogenetics for brain, spinal and peripheral circuits in mice. Nat. Methods 12, 969–974 (2015).
Park, S. I. et al. Soft, stretchable, fully implantable miniaturized optoelectronic systems for wireless optogenetics. Nat. Biotechnol. 33, 1280–1286 (2015).
Park, S. I. et al. Stretchable multichannel antennas in soft wireless optoelectronic implants for optogenetics. Proc. Natl Acad. Sci. USA 113, E8169–E8177 (2016).
Shin, G. et al. Flexible near-field wireless optoelectronics as subdermal implants for broad applications in optogenetics. Neuron 93, 509–521 (2017).
Jeong, J. W. et al. Wireless optofluidic systems for programmable in vivo pharmacology and optogenetics. Cell 162, 662–674 (2015).
This work was supported by the French government (‘Investissements d’Avenir’ ANR-10-LABX-54 MEMOLIFE, ANR-11-IDEX-0001-02 PSL University and ANR-11-LABX-0011-01 to P.P.; ANR-JCJC 2014 to A.M.), the European Research Council (ERC Advanced Grant #693021 to P.P.), the Brain and Behavior Research Foundation (NARSAD Young Investigator Award to A.M.) and the US National Institutes of Health (grants #GM053395 and #NS069720 to G.C.R.E.-D.). A.M. was the recipient of a fundamental research prize from the Medisite Foundation for Neuroscience.
The authors declare no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Molecular groups that are responsible for light absorbance (and thus the colour of the molecule).
- Photo-isomerizing group
A molecular group that can be switched between two distinct cis and trans configurations, or isomers, with particular wavelengths of light.
- Allosteric modulators
Modulators of the activity of enzymes and receptors that target a ligand-binding site distinct from that to which the substrate or agonist binds.
- Quantum yield
The efficiency of a photochemical reaction with respect to the amount of light absorbed.
In azobenzenes, the ability for the cis and trans isomers each to be stable under particular illumination conditions and over long periods of time (minutes to days).
- Photostationary state
The steady state reached by a photochemical reaction under a given illumination condition. In photo-isomerization, the photostationary state is usually given as a ratio of cis to trans photo-isomers.
The process by which an established pharmacological compound is converted into a photoswitchable one, through the introduction of an azobenzene moiety.
- Singlet oxygen
A specific state of the diatomic oxygen molecule (O2) that is usually produced by light irradiation and that can cause photo-damage to nearby molecules.
- Genetic code expansion
A methodology that allows the introduction of unnatural amino acids into a protein. It is usually based on the re-assignment of an engineered stop codon within the protein coding sequence.
- Agonist deactivation kinetics
Current decay following agonist removal from a ligand-gated ion channel.
- Directional selectivity
The ability of a neuron to respond differentially to the direction of the stimulus.
The transmission of a signalling molecule that is released from glial cells and that acts on nearby cells (such as neurons).
- Topographic maps
Spatially organized representations of a sensory surface (for example, the retina or the skin) in the cortex or other brain areas.
- ON and OFF responses
Depolarization (ON) or hyperpolarization (OFF) of bipolar cells in the retina in response to light.
About this article
Cite this article
Paoletti, P., Ellis-Davies, G.C.R. & Mourot, A. Optical control of neuronal ion channels and receptors. Nat Rev Neurosci 20, 514–532 (2019). https://doi.org/10.1038/s41583-019-0197-2
Molecular Brain (2022)
Nature Reviews Chemistry (2022)
Emerging strategies for the genetic dissection of gene functions, cell types, and neural circuits in the mammalian brain
Molecular Psychiatry (2022)
Nature Reviews Chemistry (2022)
Journal of Molecular Neuroscience (2022)