Biology subjects

Llebaria, A.

Publications and source records attributed to Llebaria, A..

14 recordsLinked to original sources

bioRxiv2026

Tilted striatofugal balance and beneficial effects of facilitating mGlu4 receptor activity in the Fmr1-/- mouse model of Fragile X Syndrome

Fragile X Syndrome (FXS) is the leading monogenic cause of autism spectrum disorder (ASD). To date, no approved pharmacological treatment alleviates social impairments in patients with FXS. Since D1 and D2 dopamine receptor-expressing striatal projection neurons (SPNs) were shown to regulate ASD-sensitive behaviors, we explored whether the balance of activity between D1- and D2-SPNs would be biased in the Fmr1-/- mouse model of FXS. We evaluated striatal function in Fmr1-/- and Fmr1+/+ mice under pharmacological challenge and performed RNAscope(R) in situ hybridization following social interaction to assess the activity of SPNs in the nucleus accumbens (NAc) and dorsal striatum (DS). We evidenced a decrease in D1-SPN activity, biasing the D1/D2-SPN balance towards an excessive weight of D2-SPN outputs. We then evaluated the effects of compounds that repress D2-SPN activity on behavioral impairments in Fmr1-/- mice. Systemically facilitating mGlu4 or blocking A2A receptor activity relieved behavioral deficits in this model. Finally, we tested the hypothesis that a tilt of the D1/D2-SPN balance in Fmr1-/- mice may contribute to their social deficit by facilitating mGlu4 activity directly in the projection site of NAc D2-SPNs. Social interaction in Fmr1-/- mice was fully rescued by photopharmacological activation of mGlu4 in the ventral pallidum (VP), where NAc D2-SPNs project. This result supports our hypothesis of excessive D2-SPN outputs and highlights the contribution of the VP in controlling social behavior. In conclusion, pharmacological compounds that repress D2-SPN activity demonstrate a promising therapeutic potential to relieve ASD-like deficits in FXS.

neuroscience↗

bioRxiv2025

Photocaged chloroquine derivatives for the light-dependent inhibition of autophagy in cancer stem cells

Chloroquine (CQ) and hydroxychloroquine (HCQ) inhibit autophagy and have shown promise as adjuvant anticancer agents, particularly for targeting therapy-resistant cancer stem cells (CSCs). However, their clinical utility is limited by systemic toxicity and poor tumour selectivity. Here we report the design, synthesis, and photochemical evaluation of [7-(diethylamino)coumarin-4-yl]methyl (DEACM)-caged CQ and HCQ derivatives as visible-light-activated autophagy inhibitors. Selective caging of the aliphatic amine fully suppressed biological activity in the dark and enabled rapid, efficient release of the parent drugs upon illumination. The lead compound 1C displayed robust light-dependent cytotoxicity across multiple cancer cell lines and, upon photoactivation, recapitulated CQs effects on LC3-II accumulation. In CSC-enriched tumourspheres, illumination of 1C completely abolished spheroid formation, demonstrating precise spatiotemporal control of stemness suppression. Importantly, ex vivo and in vivo studies confirmed that visible light penetrates tumour tissue sufficiently to activate 1C and release CQ within the tumour. These findings establish the first proof of concept for light-controlled autophagy inhibition and provide a blueprint for spatiotemporally confined anticancer therapies based on photopharmacological modulation of CSCs.

cancer biology↗

bioRxiv2025

Shedding light on left hippocampal mGlu5 in Alzheimer's disease

Metabotropic glutamate receptor 5 (mGlu5) plays a central role in synaptic plasticity and memory, and has emerged as a potential therapeutic target in Alzheimers disease (AD). While asymmetries in hippocampal function have been observed in AD patients, the lateralized contribution of mGlu5 signaling to cognitive decline remains unclear. Here, we show the presence of a physiological left-right asymmetry in mGlu5 expression in the hippocampus of wild-type mice, with higher levels in the left hemisphere, consistent with previous observations. Importantly, we reveal that this asymmetry is lost in J20 AD model mice due to a selective reduction of mGlu5 in the left hippocampus. Then, using the light-controllable negative allosteric modulator Alloswitch-1, we demonstrate that selective inhibition of mGlu5 in the left, but not right, hippocampus is both necessary and sufficient to restore working and short-term memory in J20 mice. This left-specific modulation also reverses downstream pathological signaling, including aberrant Pyk2 and GSK3-{beta} activation and tau hyperphosphorylation, in both hippocampi. Our findings identify a functional lateralization of mGlu5 in hippocampal circuits and highlight the potential of spatially targeted photopharmacology for precise intervention in early AD pathology.

neuroscience↗

bioRxiv2025

Time-resolved structures of β2-adrenergic receptor modulation by a photoswitchable beta-blocker

G protein-coupled receptors (GPCRs) regulate essential physiological responses and are important drug targets, yet their ligand-induced conformational dynamics remain poorly understood. The {beta}2-adrenergic receptor ({beta}2AR) is a prominent member of the GPCR family. It regulates bronchial and vascular function and is a significant drug target, particularly in respiratory and smooth muscle-related disorders. We employed time-resolved crystallography at X-ray free-electron lasers (XFELs) to capture the conformational dynamics of {beta}2AR bound to photoazolol-1, a beta-blocker derivative developed for photopharmacological applications. Structural snapshots of the receptor bound to trans-photoazolol-1 (pre-photoconversion), a strained intermediate, and the fully photoisomerized cis-photoazolol-1 reveal an intricate interplay between ligand chemistry and receptor plasticity. Isomerization of the azobenzene moiety induces distinct conformational changes within the orthosteric pocket, altering interactions with the extracellular loop 2 and transmembrane helices 5 and 6. Supported by functional assays, these structural shifts suggest that photoazolol-1 transitions from an inverse agonist to a neutral antagonist upon photoactivation. Our findings uncover a mechanism of GPCR modulation reminiscent of rhodopsin activation and offer a framework for designing ligands that harness light-driven transitions to achieve spatiotemporal control of receptor function.

biochemistry↗

bioRxiv2024

A photoswitchable positive allosteric modulator to control the activation of the metabotropic glutamate receptor 5 by light

1.The metabotropic glutamate receptor 5 (mGlu5) is widely expressed in the brain, where it plays an important role in synaptic plasticity, learning and memory, making it a therapeutic target of interest in various neurological disorders. In this study, we developed a photoswitchable positive allosteric modulator (PAM) of the mGlu5, as a novel tool for this clinically relevant drug target. To that aim, we used an azologisation strategy of the mGlu5 PAM agonist VU0424465 leading to the molecule azoglurax. We observed a reversible photoisomerization of azoglurax in solution with optimal wavelengths of 365 nm and 435 nm for trans to cis and cis to trans isomerization, respectively. In cell-based assays, azoglurax potentiates the agonist-induced activity of mGlu5 with a sub-micromolar potency in the dark. This potency is reduced under UV illumination. Similar to its parent molecule, azoglurax acts as an allosteric agonist of mGlu5, activating the receptor in absence of glutamate, as demonstrated on a glutamate-insensitive mutant receptor. Docking and site-directed mutagenesis experiments also suggest that azoglurax and VU0424465 bind the same pocket. In addition, molecular dynamics on cis-azoglurax-bound mGlu5 suggests that it azoglurax cis isomer does not bind stably in the receptor, in contrast to the trans-isomer, explaining the difference of activity between the two isomers. In conclusion, azoglurax is the first mGlu5 photoswitchable PAM agonist reported to date, retaining the properties and the binding mode of its parent in the dark, while the insertion of an azobenzene confers light-regulated activity. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=138 SRC="FIGDIR/small/629646v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@1e0c1f4org.highwire.dtl.DTLVardef@dd7e36org.highwire.dtl.DTLVardef@1892657org.highwire.dtl.DTLVardef@1343743_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstractC_FLOATNO C_FIG

pharmacology and toxicology↗

bioRxiv2024

A 'double-edged' role for type-5 metabotropic glutamate receptors in pain disclosed by light-sensitive drugs

Knowing the site of drug action is important to optimize effectiveness and address any side effects. We used light-sensitive drugs to identify the brain region-specific role of mGlu5 metabotropic glutamate receptors in the control of pain. Optical activation of systemic JF-NP-26, a caged, normally inactive, negative allosteric modulator (NAM) of mGlu5 receptors, in cingulate, prelimbic and infralimbic cortices and thalamus inhibited neuropathic pain hypersensitivity. Systemic treatment of alloswitch-1, an intrinsically active mGlu5 receptor NAM, caused analgesia, and the effect was reversed by light-induced drug inactivation in in the prelimbic and infralimbic cortices, and thalamus. This demonstrates that mGlu5 receptor blockade in the medial prefrontal cortex and thalamus is both sufficient and necessary for the analgesic activity of mGlu5 receptor antagonists. Surprisingly, when light was delivered in the basolateral amygdala, local activation of systemic JF-NP-26 reduced pain thresholds, whereas inactivation of alloswitch-1 enhanced analgesia. Electrophysiological analysis showed that alloswitch-1 increased excitatory synaptic responses in prelimbic pyramidal neurons evoked by stimulation of BLA input, and decreased feedforward inhibition of amygdala output neurons by BLA. Both effects were reversed by optical silencing and reinstated by optical reactivation of alloswitch-1. These findings demonstrate for the first time that the action of mGlu5 receptors in the pain neuraxis is not homogenous, and suggest that blockade of mGlu5 receptors in the BLA may limit the overall analgesic activity of mGlu5 receptor antagonists. This could explain the suboptimal effect of mGlu5 NAMs on pain in human studies and validate photopharmacology as an important tool to determine ideal target sites for systemic drugs.

neuroscience↗

bioRxiv2023

Conformational diversity in class C GPCR positive allosteric modulation

The metabotropic glutamate receptors (mGlus) are class C G protein coupled receptors (GPCR) that form obligate dimers activated by the major excitatory neurotransmitter L-glutamate1,2. The architecture of mGlu receptor comprises an extracellular Venus-Fly Trap domain (VFT) connected to a transmembrane domain (7TM) through a Cysteine-Rich Domain (CRD). The binding of L-glutamate in the VFTs and subsequent conformational change results in the signal being transmitted to the 7TM inducing G-protein binding and activation 3-6. The mGlu receptors signal transduction can be allosterically potentiated by positive allosteric modulators (PAMs) binding to the 7TMs, which are of therapeutic interest in various neurological disorders7-9. Here, we report the cryoEM structures of metabotropic glutamate receptor 5 (mGlu5) purified with three chemically and pharmacologically distinct PAMs. We find that PAMs modulate the receptor equilibrium through their different binding modes, revealing how their interactions in the 7TMs impact the mGlu5 receptor conformational landscape and function. In addition, we identified a PAM-free but agonist-bound intermediate state that is stabilised by interactions mediated by intracellular loop 2. The activation of mGlu5 receptor is a multi-step sequential process in which the binding of the PAMs in the 7TM modulates the equilibrium towards the active state.

biochemistry↗

bioRxiv2023

Design of a low-cost photomodulator for in vivo photoactivation of a mGluR5 inhibitor

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. 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, producing raseglurant, a mGluR5 inhibitor shown to have antinociceptive effects in animal models. We show our photomodulator produces a significant reduction in pain response in the formalin model by photoreleasing raseglurant, indicating our photomodulator can successfully drive in vivo photopharmacology. We demonstrate modifications which enable the photomodulator to operate wirelessly. By documenting our photomodulator development, we hope to introduce researchers to a simple solution which significantly lowers the engineering barriers to photopharmacology research.

pharmacology and toxicology↗

bioRxiv2022

Identification of differential polypharmacology between the PARP inhibitor rucaparib and its major metabolite

The (poly)pharmacology of drug metabolites is seldom comprehensively characterized in drug discovery and development. However, some drug metabolites can reach high plasma concentrations and display relevant in vivo activity, which can be distinct from its parent drug. Here, we use computational and experimental methods to comprehensively characterise the kinase polypharmacology of M324, the major metabolite of the FDA-approved PARP inhibitor rucaparib. We experimentally demonstrate that M324 displays a distinct in vitro kinome profile from its parent drug, characterized by potent in vitro inhibition of GSK3A and PLK2 at clinically-relevant concentrations. These confirmed kinase activities of M324 could have potential implications for the efficacy and safety of rucaparib and therefore warrant further clinical investigation. The study reported here highlights the importance of thoroughly characterizing the activity of significant drug metabolites to better understanding drug responses in the clinic and maximally exploit the current drug arsenal in personalized and precision medicine.

pharmacology and toxicology↗

bioRxiv2022

Differential reduction of neuropathic pain symptoms by mGlu4-mediated neuromodulation of amygdala circuits

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 of 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 mechanisms associated to the metabotropic glutamate receptors mGlu4 in the amygdala to modulate neuropathic pain. In a murine model of peripheral mononeuropathy induced by a chronic constriction of the sciatic nerve, we demonstrate that pharmacological activation of amygdala mGlu4 receptors efficiently alleviates sensory and depressive-like symptoms in both male and female mice. Moreover, we reveal a differential modulation of those symptoms, activating mGlu4 receptors in the controlateral amygdala, relatively 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 a precise spatiotemporal photocontrol of deep brain endogenous targets, we further demonstrate the rapid and reversible action of mGlu4-mediated neuromodulation on neuropathic pain symptoms. Finally, coupling photopharmacology and analgesic conditioned place preference, we show an important pain-reducing effect of mGlu4 activation. Taken together, these data highlight the analgesic potential of enhancing amygdala mGlu4 activity to counteract neuropathy in the hope of improving existing treatments.

neuroscience↗

bioRxiv2022

Design and validation of the first family of photo-activatable ligands for melatonin receptors

Melatonin is a neurohormone released in a circadian manner with peak levels during the night. In mammals, melatonin mediates its effects mainly through G protein-coupled MT1 and MT2 receptors. Drugs acting on melatonin receptors are indicated for circadian rhythm- and sleep-related disorders and major depression. Pharmacological tools to study the activation of these receptors with high temporal resolution are lacking. Here, we synthesized a family of light-activatable caged melatonin compounds by covalently attaching o-nitrobenzyl (o-NB) or coumarin photocleavable groups to the N-position of melatonin. All caged compounds showed the expected decrease in binding affinity for MT1 and MT2. Among them, the o-NB derivative MCS-0382 showed the best uncaging and biological properties upon light activation with a significant increase (2.5 log left-shift) in affinity and potency in melatonin receptor binding and signaling, respectively. Generation of biologically active melatonin from MCS-0382 was further demonstrated by its ability to modulate the excitation of SCN neurons in rat brain slices. MCS-0382 is now available to study melatonin effects in a temporally controlled manner in cellular and physiological settings.

pharmacology and toxicology↗

bioRxiv2022

A photoswitchable ligand targeting β1-adrenoceptor enables light-control of the cardiac rhythm

Catecholamine-triggered {beta}-adrenoceptor ({beta}-AR) signaling is essential for the correct functioning of the heart. Although both {beta}1- and {beta}2-AR subtypes are expressed in cardiomyocytes, drugs selectively targeting {beta}1-AR have proven this receptor as the main target for the therapeutic effects of beta blockers in heart. Here, we report a new strategy for the spatiotemporal control of {beta}1-AR activation by means of light-regulated drugs with a high level of {beta}1-/{beta}2-AR selectivity. All reported molecules allow for an efficient real time optical control of receptor function in vitro. Moreover, using confocal microscopy we demonstrate that the binding of our best hit, pAzo-2, can be reversibly photocontrolled. Strikingly, pAzo-2 also enables a dynamic cardiac rhythm management on alive zebrafish larvae using light, thus highlighting the therapeutic and research potential of the developed photoswitches. Overall, this work provides the first proof of precise control of the therapeutic target {beta}1-AR in native environments using light.

pharmacology and toxicology↗

bioRxiv2021

Fast photoswitchable molecular prosthetics control neuronal activity in the cochlea

Artificial control of neuronal activity enables studies of neural circuits and restoration of neural function. Direct, rapid, and sustained photocontrol of intact neurons could overcome shortcomings of established electrical stimulation such as poor selectivity. We have developed fast photoswitchable ligands of glutamate receptors to establish such control in the auditory system. The new photoswitchable ligands produced photocurrents in untransfected neurons upon covalently tethering to endogenous glutamate receptors and activating them reversibly with visible light pulses of few milliseconds. As a proof of concept of these molecular prostheses, we apply them to the ultrafast synapses of auditory neurons of the cochlea that encode sound and provide auditory input to the brain. This drug-based method affords kilohertz rate stimulation of auditory neurons of adult gerbils without genetic manipulation that would be required for their optogenetic control. The new photoswitchable ligands are also broadly applicable to spatiotemporally control fast spiking interneurons in the brain.

neuroscience↗

bioRxiv2019

Reversible silencing of endogenous receptors in intact brain tissue using two-photon pharmacology

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 two-photon excitation (2PE) using pulsed near-infrared lasers to reversibly silence 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 m. Thus, two-photon pharmacology (2PP) using alloswitch allows investigating mGlu5-dependent processes in wild type animals, including synaptic formation and plasticity, and signaling pathways from intracellular organelles.

pharmacology and toxicology↗