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Purpose: Severe side effects prevent the utilization of otherwise promising drugs in treatments. These side effects arise when drugs affect untargeted tissues due to poor target specificity. In photopharmacology, light controls the timing and the location of drug delivery, improving treatment specificity and pharmacokinetic control. Photopharmaceuticals have not seen widespread adoption in part because researchers do not always have access to reliable and reproducible light delivery devices at prices which fit within the larger research budget. Method: In this work, we present a customizable photomodulator for use in both wearable and implantable devices. For experimental validation of the photomodulator, we photolyse JF-NP-26 in rats. Results: We successfully drive in vivo photopharmacology with a tethered photomodulator and demonstrate modifications which enable the photomodulator to operate wirelessly. Conclusion: By documenting our photomodulator development, we hope to introduce researchers to a simple solution which significantly lowers the engineering barriers to photopharmacology research.

In recent years, there has been growing interest in the potential therapeutic use of inhibitors of adenosine A2A receptors (A2AR) for the treatment of neurodegenerative diseases and cancer. Nevertheless, the widespread expression of A2AR throughout the body emphasizes the importance of temporally and spatially selective ligands. Photopharmacology is an emerging strategy that utilizes photosensitive ligands to attain high spatiotemporal precision and regulate the function of biomolecules using light. In this study, we combined photochemistry and cellular and in vivo photopharmacology to investigate the light sensitivity of the FDA-approved antagonist istradefylline and its potential use as an A2AR photopharmacological tool. Our findings reveal that istradefylline exhibits rapid trans-to-cis isomerization under near-UV light, and prolonged exposure results in the formation of photocycloaddition products. We demonstrate that exposure to UV light triggers a time-dependent decrease in the antagonistic activity of istradefylline in A2AR-expressing cells and enables real-time optical control of A2AR signaling in living cells and zebrafish. Together, these data demonstrate that istradefylline is a photoinactivatable A2AR antagonist and that this property can be utilized to perform photopharmacological experiments in living cells and animals.

Traditional methods for site-specific drug delivery in the brain are slow, invasive, and difficult to interface with recordings of neural activity. Here, we demonstrate the feasibility and experimental advantages of in vivo photopharmacology using caged opioid drugs that are activated in the brain with light after systemic administration in an inactive form. To enable bidirectional manipulations of endogenous opioid receptors in vivo, we developed photoactivatable oxymorphone (PhOX) and photoactivatable naloxone (PhNX), photoactivatable variants of the mu opioid receptor agonist oxymorphone and the antagonist naloxone. Photoactivation of PhOX in multiple brain areas produced local changes in receptor occupancy, brain metabolic activity, neuronal calcium activity, neurochemical signaling, and multiple pain- and reward-related behaviors. Combining PhOX photoactivation with optical recording of extracellular dopamine revealed adaptations in the opioid sensitivity of mesolimbic dopamine circuitry in response to chronic morphine administration. This work establishes a general experimental framework for using in vivo photopharmacology to study the neural basis of drug action.

Background and Purpose: Opioid-based drugs are the gold standard medicines for pain relief. However, tolerance and several side effects (i.e. constipation and dependence) may occur upon chronic opioid administration. Photopharmacology is a promising approach to improve the benefit/risk profiles of these drugs. Thus, opioids can be locally activated with high spatiotemporal resolution, potentially minimizing systemic-mediated adverse effects. Here, we aimed at developing a morphine photo-derivative (photocaged morphine), which can be activated upon light irradiation both in vitro and in vivo. Experimental Approach: Light-dependent activity of pc-morphine was assessed in cell-based assays (intracellular calcium accumulation and electrophysiology) and in mice (formalin animal model of pain). In addition, tolerance, constipation and dependence were investigated in vivo using experimental paradigms. Key results: In mice, pc-morphine was able to elicit antinociceptive effects, both using external light-irradiation (hind paw) and spinal cord implanted fibre-optics. In addition, remote morphine photoactivation was devoid of common systemic opioid-related undesired effects, namely, constipation, tolerance to the analgesic effects, rewarding effects and naloxone-induced withdrawal. Conclusion and Implications: Light-dependent opioid-based drugs may allow effective analgesia without the occurrence of tolerance or the associated and severe opioid-related undesired effects.

Background and Purpose: Opioid-based drugs are the gold standard medicines for pain relief. However, tolerance and several side effects (i.e. constipation and dependence) may occur upon chronic opioid administration. Photopharmacology is a promising approach to improve the benefit/risk profiles of these drugs. Thus, opioids can be locally activated with high spatiotemporal resolution, potentially minimizing systemic-mediated adverse effects. Here, we aimed at developing a morphine photo-derivative (photocaged morphine), which can be activated upon light irradiation both in vitro and in vivo. Experimental Approach: Light-dependent activity of pc-morphine was assessed in cell-based assays (intracellular calcium accumulation and electrophysiology) and in mice (formalin animal model of pain). In addition, tolerance, constipation and dependence were investigated in vivo using experimental paradigms. Key results: In mice, pc-morphine was able to elicit antinociceptive effects, both using external light-irradiation (hind paw) and spinal cord implanted fibre-optics. In addition, remote morphine photoactivation was devoid of common systemic opioid-related undesired effects, namely, constipation, tolerance to the analgesic effects, rewarding effects and naloxone-induced withdrawal. Conclusion and Implications: Light-dependent opioid-based drugs may allow effective analgesia without the occurrence of tolerance or the associated and severe opioid-related undesired effects.

Light-responsive molecules have seen a major advance in modulating biological functions in recent years. Especially photoswitches are highly attractive building blocks due to the reversible nature of their light-mediated reactivity. They are frequently used to affect both the properties of small bioactive compounds and biomacromolecules if incorporated suitably. Despite their success in a plethora of applications, only a limited set of photochromic core structures is routinely employed and a large number of photochromic couples are under-investigated in biological context. Broadening the toolbox of photoswitches available to modulate biological activity would open new avenues and unlock the full potential of photoswitchable molecules for biological studies. In this work, we explore the photochemical and thermal properties of the dihydroazulene/vinylheptafulvene photochromic couple as peptide conjugates in aqueous environment.

Light-responsive molecules have seen a major advance in modulating biological functions in recent years. Especially photoswitches are highly attractive building blocks due to the reversible nature of their light-mediated reactivity. They are frequently used to affect both the properties of small bioactive compounds and biomacromolecules if incorporated suitably. Despite their success in a plethora of applications, only a limited set of photochromic core structures is routinely employed and a large number of photochromic couples are under-investigated in biological context. Broadening the toolbox of photoswitches available to modulate biological activity would open new avenues and unlock the full potential of photoswitchable molecules for biological studies. In this work, we explore the photochemical and thermal properties of the dihydroazulene/vinylheptafulvene photochromic couple as peptide conjugates in aqueous environment.

Light-responsive molecules have seen a major advance in modulating biological functions in recent years. Especially photoswitches are highly attractive building blocks due to the reversible nature of their light-mediated reactivity. They are frequently used to affect both the properties of small bioactive compounds and biomacromolecules if incorporated suitably. Despite their success in a plethora of applications, only a limited set of photochromic core structures is routinely employed and a large number of photochromic couples are under-investigated in biological context. Broadening the toolbox of photoswitches available to modulate biological activity would open new avenues and unlock the full potential of photoswitchable molecules for biological studies. In this work, we explore the photochemical and thermal properties of the dihydroazulene/vinylheptafulvene photochromic couple as peptide conjugates in aqueous environment.

Light-responsive molecules have seen a major advance in modulating biological functions in recent years. Especially photoswitches are highly attractive building blocks due to the reversible nature of their light-mediated reactivity. They are frequently used to affect both the properties of small bioactive compounds and biomacromolecules if incorporated suitably. Despite their success in a plethora of applications, only a limited set of photochromic core structures is routinely employed and a large number of photochromic couples are under-investigated in biological context. Broadening the toolbox of photoswitches available to modulate biological activity would open new avenues and unlock the full potential of photoswitchable molecules for biological studies. In this work, we explore the photochemical and thermal properties of the dihydroazulene/vinylheptafulvene photochromic couple as peptide conjugates in aqueous environment.

Light-responsive molecules have seen a major advance in modulating biological functions in recent years. Especially photoswitches are highly attractive building blocks due to the reversible nature of their light-mediated reactivity. They are frequently used to affect both the properties of small bioactive compounds and biomacromolecules if incorporated suitably. Despite their success in a plethora of applications, only a limited set of photochromic core structures is routinely employed and a large number of photochromic couples are under-investigated in biological context. Broadening the toolbox of photoswitches available to modulate biological activity would open new avenues and unlock the full potential of photoswitchable molecules for biological studies. In this work, we explore the photochemical and thermal properties of the dihydroazulene/vinylheptafulvene photochromic couple as peptide conjugates in aqueous environment.

Background and Purpose: Opioid-based drugs are the gold standard medicines for pain relief. However, tolerance and several side effects (i.e. constipation and dependence) may occur upon chronic opioid administration. Photopharmacology is a promising approach to improve the benefit/risk profiles of these drugs. Thus, opioids can be locally activated with high spatiotemporal resolution, potentially minimizing systemic-mediated adverse effects. Here, we aimed at developing a morphine photo-derivative (photocaged morphine), which can be activated upon light irradiation both in vitro and in vivo. Experimental Approach: Light-dependent activity of pc-morphine was assessed in cell-based assays (intracellular calcium accumulation and electrophysiology) and in mice (formalin animal model of pain). In addition, tolerance, constipation and dependence were investigated in vivo using experimental paradigms. Key results: In mice, pc-morphine was able to elicit antinociceptive effects, both using external light-irradiation (hind paw) and spinal cord implanted fibre-optics. In addition, remote morphine photoactivation was devoid of common systemic opioid-related undesired effects, namely, constipation, tolerance to the analgesic effects, rewarding effects and naloxone-induced withdrawal. Conclusion and Implications: Light-dependent opioid-based drugs may allow effective analgesia without the occurrence of tolerance or the associated and severe opioid-related undesired effects.

Background and Purpose: Opioid-based drugs are the gold standard medicines for pain relief. However, tolerance and several side effects (i.e. constipation and dependence) may occur upon chronic opioid administration. Photopharmacology is a promising approach to improve the benefit/risk profiles of these drugs. Thus, opioids can be locally activated with high spatiotemporal resolution, potentially minimizing systemic-mediated adverse effects. Here, we aimed at developing a morphine photo-derivative (photocaged morphine), which can be activated upon light irradiation both in vitro and in vivo. Experimental Approach: Light-dependent activity of pc-morphine was assessed in cell-based assays (intracellular calcium accumulation and electrophysiology) and in mice (formalin animal model of pain). In addition, tolerance, constipation and dependence were investigated in vivo using experimental paradigms. Key results: In mice, pc-morphine was able to elicit antinociceptive effects, both using external light-irradiation (hind paw) and spinal cord implanted fibre-optics. In addition, remote morphine photoactivation was devoid of common systemic opioid-related undesired effects, namely, constipation, tolerance to the analgesic effects, rewarding effects and naloxone-induced withdrawal. Conclusion and Implications: Light-dependent opioid-based drugs may allow effective analgesia without the occurrence of tolerance or the associated and severe opioid-related undesired effects.

Microtubule dynamics can be inhibited with sub-second temporal resolution and cellular-scale spatial resolution, by using precise illuminations to optically pattern where and when photoswitchable microtubule-inhibiting chemical reagents exert their latent bioactivity. The recently available reagents (SBTub, PST, STEpo, AzTax, PHTub) now enable researchers to use light to reversibly modulate microtubule-dependent processes in eukaryotes, in 2D and 3D cell culture as well as in vivo, across a variety of model organisms: with applications in fields from cargo transport to cell migration, cell division, and embryonic development. Here we give an introduction to using these photoswitchable microtubule inhibitors in cells. We describe the theory of small molecule photoswitching, and the unique performance features, usage requirements, and limitations that photoswitchable chemical reagents have; then we summarize the major classes of photoswitchable microtubule inhibitors that are currently available, with the properties that suit them to different applications, and troubleshooting measures for avoiding common mistakes. We outline workflows to establish cellular assays where they are used to optically control microtubule dynamics in a temporally reversible fashion with spatial specificity down to a single selected cell within a field of view. The methods in this chapter also equip the reader to tackle advanced uses of photoswitchable chemical reagents, in 3D culture and in vivo.

Optical methods to modulate microtubule dynamics show promise for reaching the micron- and millisecond-scale resolution needed to decrypt the roles of the cytoskeleton in biology. However, optical microtubule stabilisers are under-developed. We introduce “STEpos” as GFP-orthogonal, light-responsive epothilone-based microtubule stabilisers. They use a novel styrylthiazole photoswitch in a design to modulate hydrogen-bonding and steric effects that control epothilone potency. STEpos photocontrol microtubule dynamics and cell division with micron- and second-scale spatiotemporal precision. They substantially improve potency, solubility, and ease-of-use compared to previous optical microtubule stabilisers, and the structure-photoswitching-activity relationship insights in this work will guide future optimisations. The STEpo reagents can contribute greatly to high-precision research in cytoskeleton biophysics, cargo transport, cell motility, cell division, development, and neuroscience.

Immer neu auftretende Virusvarianten oder die Entstehung multiresistenter Bakterien stellen eine enorme Herausforderung in der heutigen Medizin dar. Die Biodiversität der Natur bietet ein großes Reservoir für die Entdeckung neuer Naturstoffe mit biologischem Potential wie antibakteriellen, antiviralen oder antikanzerogenen Eigenschaften. Ein phänotypisches Selektionsverfahren kann zur Identifizierung potentieller Leitstrukturen zur Behandlung von beispielsweise bakteriellen oder viralen Infektionen dienen. Jedoch ist der Wirkmechanismus der identifizierten Leitstrukturen zunächst unbekannt. Die Charakterisierung der Wirkmechanismen kann durch eine Vielzahl unterschiedlicher Strategien durchgeführt werden. Omics-Studien reichen von Transkriptom- über Proteom- bis hin zu Metabolom- bzw. Lipidomanalysen und bieten somit eine hervorragende Möglichkeit sekundäre Zielstrukturen und Bindungsstellen an primäre Zielstrukturen zu identifizieren oder den Effekt von Zielstruktur-Abundanz auf die zelluläre Aktivität zu charakterisieren. Darüber hinaus bietet Photopharmakologie die Möglichkeit sowohl die Auswirkung einer Konfigurationsänderung auf die biologische Aktivität zu evaluieren als auch Informationen über die Struktur-Aktivitäts-Beziehung zu gewinnen. In dieser Arbeit wurden die Wirkmechanismen von Cystobactamiden und Labyrinthopeptinen unter Einsatz verschiedener Omic-Strategien charakterisiert. Cystobactamide zeigen antibakterielle Aktivität gegen sowohl Gram-negative als auch Gram-positive Bakterien der ESKAPE Pathogene. Die antibakterielle Aktivität wird durch die Inhibierung von Gyrase und Topoisomerase IV hervorgerufen. Zunächst wurden Cystobactamide kinetisch und biologisch charakterisiert, die einen oder mehrere sogenannte Photoschalter im Molekül haben. Die Konfigurationsänderung von trans nach cis resultiert in einem leichten Anstieg der biologischen Aktivität. Zusätzlich konnten die Resistenzmechanismen der Enzyme AlbA und AlbD durch die trans-Konfiguration vo

The rise of antibiotic resistance causes a serious health care problem, and its counterfeit demands novel, innovative concepts. The combination of photopharmacology, enabling a light-controlled reversible modulation of drug activity, with antibiotic drug design has led to first photoswitchable antibiotic compounds derived from established scaffolds. In this study, we converted cystobactamids, gyrase-inhibiting natural products with an oligoaryl scaffold and highly potent antibacterial activities, into photoswitchable agents by inserting azobenzene in the N-terminal part and/or an acylhydrazone moiety near the C-terminus, yielding twenty analogs that contain mono- as well as double-switches. Antibiotic and gyrase inhibition properties could be modulated 3.4-fold and 5-fold by light, respectively. Notably, the sensitivity of photoswitchable cystobactamids towards two known resistance factors, the peptidase AlbD and the scavenger protein AlbA, was light-dependent. While irradiation of an analog with an N-terminal azobenzene with 365 nm light led to less degradation by AlbD, the AlbA-mediated inactivation was induced. This provides a proof-of-principle that resistance towards photoswitchable antibiotics can be optically controlled.

Neuropathic pain is a common health problem resulting in exacerbated response to noxious and non noxious stimuli, as well as impaired emotional and cognitive responses. Unfortunately, neuropathic pain is also one of the most difficult pain syndromes to manage, highlighting the importance of better understanding the brain regions and neuromodulatory mechanisms involved in its regulation. Among the many interconnected brain areas which process pain, the amygdala is known to play an important role in the integration of sensory and emotional pain signals. Here we questioned the ability of a recently identified neuromodulatory mechanism associated with the metabotropic glutamate receptors mGlu4 in the amygdala to modulate neuropathic pain. In a murine model of peripheral mononeuropathy, we demonstrate that pharmacological activation of amygdala mGlu4 efficiently alleviates sensory and depressive-like symptoms in both male and female mice. Moreover, we reveal a differential modulation of these symptoms. Activating mGlu4 in the contralateral amygdala relative to the side of the mononeuropathy, is necessary and sufficient to relieve both sensory and depressive-like symptoms, while ipsilateral activation solely reduces depressive-like symptoms. Furthermore, using photopharmacology, a recent strategy allowing precise photocontrol of endogenous proteins, we further demonstrate the dynamic alleviation of neuropathic pain through light-dependent facilitation of mGlu4 by a photoswitchable positive allosteric modulator. Finally, coupling photopharmacology and analgesic conditioned place preference, we show a significant pain-reducing effect of mGlu4 activation. Taken together, these data highlight the analgesic potential of enhancing amygdala mGlu4 activity to counteract neuropathy reinforcing its therapeutic interest for the treatment of pathological pain.

G-protein-coupled receptors (GPCRs) are a super-family of membrane proteins and major targets for drug development. However, many GPCRs drug candidates suffer from a lack of selectivity. Photopharmacology gives the possibility of modulating GPCR activity with an unprecedented local and temporal precision with the use of light. In this review, we compile and classify the different strategies in photopharmacology for GPCRs, we revise the different methods of analysis and characterization of light-regulated molecules used for GPCRs, and we give perspective of the impact of photopharmacology in research applications and in the development of new drugs.

G Protein-coupled receptors (GPCRs) are transmembrane proteins that represent a highly important class of drug targets, being the primary target of about 35% of all marketed drugs. A prime family of GPCRs is the family of histamine receptors consisting of four distinct members named histamine H1 – H4 receptor (H1R-H4R). For further study of the role of localized activation of histamine receptors in pathophysiology, the development of photoswitchable ligands may be of aid. Photoswitchable ligands are ligands that combine pharmacophore features of known histamine receptor ligands with a photoswitchable moiety. A number of photoswitchable moieties have been discovered over the course of history. However, we focused on the azobenzene moiety throughout this thesis due to its robustness and structural simplicity. Moreover, when illuminated the azobenzene moiety isomerizes from trans to cis, considerably altering the shape and polarity. One may imagine, that these difference in shape, end-to-end distance and polarity, the trans isomer and cis isomer can have different pharmacological outcomes. These different pharmacological outcomes can present itself in differences in binding affinity, efficacy and potency for the histamine receptor of interest between the two isomers. In Chapter 2 the photopharmacology concept was applied to the H3R where key compounds VUF14862 and VUF14738 were identified, showing respectively a 11.2-fold decrease or 13.5-fold increase in affinity upon illumination. In two-electrode voltage clamp (TEVC) experiments using Xenopus laevis oocytes expressing H3R and G protein-coupled inward-rectifying potassium channels (GIRK) it was shown that VUF14862 and VUF14738 were able to reversibly modulate their affinity for H3R upon illumination on a second-timescale. In Chapter 3, VUF15000 was identified as a key compound based on its high absolute potency as well as its full agonism in [35S]-GTPS assays for the H3R. When VUF15000 was applied in TEVC experiment

We report the first cellular application of the emerging near-quantitative photoswitch pyrrole hemithioindigo, by rationally designing photopharmaceutical PHTub inhibitors of the cytoskeletal protein tubulin. PHTubs allow simultaneous visible-light imaging and photoswitching in live cells, delivering cell-precise photomodulation of microtubule dynamics, and photocontrol over cell cycle progression and cell death. This is the first acute use of a hemithioindigo photopharmaceutical for high-spatiotemporal-resolution biological control in live cells. It additionally demonstrates the utility of near-quantitative photoswitches, by enabling a dark-active design to overcome residual background activity during cellular photopatterning. This work opens up new horizons for high-precision microtubule research using PHTubs and shows the cellular applicability of pyrrole hemithioindigo as a valuable scaffold for photocontrol of a range of other biological targets.

Photocontrollable reagents have unique potential as high spatiotemporal precision modulators of biological systems. Here, Gao et al. demonstrate a GFP-orthogonal and metabolically stable photoswitch that allows optical control over microtubule dynamics and architecture with subcellular resolution. The photoswitch scaffold also offers new possibilities for photopharmaceutical design against other targets.

Background and Purpose: Opioid-based drugs are the gold standard medicines for pain relief. However, tolerance and several side effects (i.e. constipation and dependence) may occur upon chronic opioid administration. Photopharmacology is a promising approach to improve the benefit/risk profiles of these drugs. Thus, opioids can be locally activated with high spatiotemporal resolution, potentially minimizing systemic-mediated adverse effects. Here, we aimed at developing a morphine photo-derivative (photocaged morphine), which can be activated upon light irradiation both in vitro and in vivo. Experimental Approach: Light-dependent activity of pc-morphine was assessed in cell-based assays (intracellular calcium accumulation and electrophysiology) and in mice (formalin animal model of pain). In addition, tolerance, constipation and dependence were investigated in vivo using experimental paradigms. Key results: In mice, pc-morphine was able to elicit antinociceptive effects, both using external light-irradiation (hind paw) and spinal cord implanted fibre-optics. In addition, remote morphine photoactivation was devoid of common systemic opioid-related undesired effects, namely, constipation, tolerance to the analgesic effects, rewarding effects and naloxone-induced withdrawal. Conclusion and Implications: Light-dependent opioid-based drugs may allow effective analgesia without the occurrence of tolerance or the associated and severe opioid-related undesired effects.

Photopharmacological tools enable the precise spatiotemporal control of small molecule drugs. Amongst them, caged compounds incorporate a photolabile moiety which is released under illumination, thus liberating the active molecule. Caging groups have long been known and many chemical scaffolds have already been used in different applications. However, most of the initial examples are cleaved with UV light, which suffers from low tissue permeability and cell damage. Recently, caging groups that are released under visible light have been reported, which expand their utility. In this review, we outline the chemical strategies that have been used to increase the absorption wavelengths; we compare their photophysical properties, discuss their synthetic accessibility, and exemplify some of their biological applications.

G protein-coupled receptors (GPCR), including the metabotrobic glutamate 5 receptor (mGlu5), are important therapeutic targets and the development of allosteric ligands for targeting GPCRs has become a desirable approach toward modulating receptor activity. Traditional pharmacological approaches toward modulating GPCR activity are still limited since precise spatiotemporal control of a ligand is lost as soon as it is administered. Photopharmacology proposes the use of photoswitchable ligands to overcome this limitation, since their activity can be reversibly controlled by light with high precision. As this is still a growing field, our understanding of the molecular mechanisms underlying the light-induced changes of different photoswitchable ligand pharmacology is suboptimal. For this reason, we have studied the mechanisms of action of alloswitch-1 and MCS0331; two freely diffusible, mGlu5 phenylazopyridine photoswitchable negative allosteric modulators. We combined photochemical, cell-based, and in vivo photopharmacological approaches to investigate the effects of trans–cis azobenzene photoisomerization on the functional activity and binding ability of these ligands to the mGlu5 allosteric pocket. From these results, we conclude that photoisomerization can take place inside and outside the ligand binding pocket, and this leads to a reversible loss in affinity, in part, due to changes in dissociation rates from the receptor. Ligand activity for both photoswitchable ligands deviates from high-affinity mGlu5 negative allosteric modulation (in the trans configuration) to reduced affinity for the mGlu5 in their cis configuration. Importantly, this mechanism translates to dynamic and reversible control over pain following local injection and illumination of negative allosteric modulators into a brain region implicated in pain control.

The physiological activity of proteins is often studied with loss-of-function genetic approaches, but the corresponding phenotypes develop slowly and can be confounding. Photopharmacology allows direct, fast, and reversible control of endogenous protein activity, with spatiotemporal resolution set by the illumination method. Here, we combine a photoswitchable allosteric modulator (alloswitch) and 2-photon excitation using pulsed near-infrared lasers to reversibly silence metabotropic glutamate 5 (mGlu5) receptor activity in intact brain tissue. Endogenous receptors can be photoactivated in neurons and astrocytes with pharmacological selectivity and with an axial resolution between 5 and 10 µm. Thus, 2-photon pharmacology using alloswitch allows investigating mGlu5-dependent processes in wild-type animals, including synaptic formation and plasticity, and signaling pathways from intracellular organelles.

The physiological activity of proteins is often studied with loss-of-function genetic approaches, but the corresponding phenotypes develop slowly and can be confounding. Photopharmacology allows direct, fast, and reversible control of endogenous protein activity, with spatiotemporal resolution set by the illumination method. Here, we combine a photoswitchable allosteric modulator (alloswitch) and 2-photon excitation using pulsed near-infrared lasers to reversibly silence metabotropic glutamate 5 (mGlu5) receptor activity in intact brain tissue. Endogenous receptors can be photoactivated in neurons and astrocytes with pharmacological selectivity and with an axial resolution between 5 and 10 µm. Thus, 2-photon pharmacology using alloswitch allows investigating mGlu5-dependent processes in wild-type animals, including synaptic formation and plasticity, and signaling pathways from intracellular organelles.

New technologies for spatial and temporal remote control of G protein-coupled receptors (GPCRs) are necessary to unravel the complexity of GPCR signalling in cells, tissues and living organisms. An effective approach, recently developed, consists on the design of light-operated ligands whereby light-dependent GPCR activity regulation can be achieved. In this context, the use of light provides an advantage as it combines safety, easy delivery, high resolution and it does not interfere with most cellular processes. In this review we summarize the most relevant successful achievements in GPCR photopharmacology. These recent findings constitute a significant advance in research studies on the molecular dynamics of receptor activation and their physiological roles in vivo. Moreover, these molecules hold potential toward clinical uses as light-operated drugs, which can overcome some of the problems of conventional pharmacology. © 2019 Elsevier B.V.

For optical control of GPCR function, we set out to develop small-molecule ligands with photoswitchable efficacy in which both configurations bind the target protein but exert distinct pharmacological effects, that is, stimulate or antagonize GPCR activation. Our design was based on a previously identified efficacy hotspot for the peptidergic chemokine receptor CXCR3 and resulted in the synthesis and characterization of five new azobenzene-containing CXCR3 ligands. G protein activation assays and real-time electrophysiology experiments demonstrated photoswitching from antagonism to partial agonism and even to full agonism (compound VUF16216). SAR evaluation suggests that the size and electron-donating properties of the substituents on the inner aromatic ring are important for the efficacy photoswitching. These compounds are the first GPCR azo ligands with a nearly full efficacy photoswitch and may become valuable pharmacological tools for the optical control of peptidergic GPCR signaling.

For optical control of GPCR function, we set out to develop small-molecule ligands with photoswitchable efficacy in which both configurations bind the target protein but exert distinct pharmacological effects, that is, stimulate or antagonize GPCR activation. Our design was based on a previously identified efficacy hotspot for the peptidergic chemokine receptor CXCR3 and resulted in the synthesis and characterization of five new azobenzene-containing CXCR3 ligands. G protein activation assays and real-time electrophysiology experiments demonstrated photoswitching from antagonism to partial agonism and even to full agonism (compound VUF16216). SAR evaluation suggests that the size and electron-donating properties of the substituents on the inner aromatic ring are important for the efficacy photoswitching. These compounds are the first GPCR azo ligands with a nearly full efficacy photoswitch and may become valuable pharmacological tools for the optical control of peptidergic GPCR signaling.

G protein-coupled receptor (GPCR) signaling occurs in complex spatiotemporal patterns that are difficult to probe using standard pharmacological and genetic approaches. A powerful approach for dissecting GPCRs is to use light-controlled pharmacological agents that are tethered covalently and specifically to genetically engineered receptors. However, deficits in our understanding of the mechanism of such photoswitches have limited application of this approach and its extension to other GPCRs. In this study, we have harnessed the power of bioorthogonal tethering to SNAP and CLIP protein tags to create a family of light-gated metabotropic glutamate receptors (mGluRs). We define the mechanistic determinants of photoswitch efficacy, including labeling efficiency, dependence on photoswitch structure, length dependence of the linker between the protein tag and the glutamate ligand, effective local concentration of the glutamate moiety, and affinity of the receptor for the ligand. We improve the scheme for photoswitch synthesis as well as photoswitch efficiency, and generate seven light-gated group II/III mGluRs, including variants of mGluR2, 3, 6, 7, and 8. Members of this family of light-controlled receptors can be used singly or in specifically labeled, independently light-controlled pairs for multiplexed control of receptor populations.

Small molecules that interfere with microtubule dynamics, such as Taxol and the Vinca alkaloids, are widely used in cell biology research and as clinical anticancer drugs. However, their activity cannot be restricted to specific target cells, which also causes severe side effects in chemotherapy. Here, we introduce the photostatins, inhibitors that can be switched on and off in vivo by visible light, to optically control microtubule dynamics. Photostatins modulate microtubule dynamics with a subsecond response time and control mitosis in living organisms with single-cell spatial precision. In longer-term applications in cell culture, photostatins are up to 250 times more cytotoxic when switched on with blue light than when kept in the dark. Therefore, photostatins are both valuable tools for cell biology, and are promising as a new class of precision chemotherapeutics whose toxicity may be spatiotemporally constrained using light., info:eu-repo/semantics/published