Photoswitchable positive allosteric modulators of metabotropic glutamate receptor 4 to improve selectivity.

Metabotropic glutamate receptors (mGlu) regulate multiple functions in the nervous systems and are involved in several neurological disorders. However, selectively targeting individual mGlu subtypes with spatiotemporal precision is still an unmet need. Photopharmacology can address this concern through the utilization of photoswitchable compounds such as optogluram, which is a positive allosteric modulator (PAM) of mGlu that enables the precise control of physiological responses using light but does not have an optimal selectivity profile.

Optical Control of Adenosine A Receptor Using Istradefylline Photosensitivity.

In recent years, there has been growing interest in the potential therapeutic use of inhibitors of adenosine A receptors (AR) for the treatment of neurodegenerative diseases and cancer. Nevertheless, the widespread expression of AR 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.

Synthesis and pharmacological characterization of conformationally restricted 2-amino-Adipic acid analogs and carboxycyclopropyl glycines as selective metabotropic glutamate 2 receptor agonists.

The metabotropic glutamate (Glu) receptors (mGluRs) are G-protein coupled receptors, which play a central role in modulating excitatory neurotransmission in the central nervous system (CNS). Thus, the development of tool compounds thereto, continues to interest the scientific community. In this study, we report the design and synthesis of new conformationally restricted 2-aminoadipic acid (2AA) 2-4, and glutamic acid 5, 6 analogs, which share the cyclopropane ring as the restrictor.

Design, Synthesis, Pharmacology, and In Silico Studies of (1,2,3)-2-(()-Amino(carboxy)methyl)-3-(carboxymethyl)cyclopropane-1-carboxylic Acid (LBG30300): A Picomolar Potency Subtype-Selective mGlu Receptor Agonist.

Metabotropic glutamate (Glu) receptors (mGlu receptors) play a key role in modulating excitatory neurotransmission in the central nervous system (CNS). In this study, we report the structure-based design and pharmacological evaluation of densely functionalized, conformationally restricted glutamate analogue (1,2,3)-2-(()-amino(carboxy)methyl)-3-(carboxymethyl)cyclopropane-1-carboxylic acid (). was synthesized in a stereocontrolled fashion in nine steps from a commercially available optically active epoxide.

()-2-Mercaptohistidine: A First Selective Orthosteric GluK3 Antagonist.

The development of tool compounds for the ionotropic glutamate receptors (iGluRs) remains an important research objective, as these are essential for the study and understanding of the roles of these receptors in health and disease. Herein, we report on the pharmacological characterization of ()-2-hydroxyhistidine () and ()-2-mercaptohistidine () as mediators of glutamatergic neurotransmission. While displayed negligible binding affinity or activity at all glutamate receptors and transporters investigated, displayed selectivity for homomeric GluK3 with binding affinities in the low micromolar range ( = 6.

Agonists and allosteric modulators promote signaling from different metabotropic glutamate receptor 5 conformations.

Metabotropic glutamate receptors (mGluRs) are dimeric G-protein-coupled receptors activated by the main excitatory neurotransmitter, L-glutamate. mGluR activation by agonists binding in the venus flytrap domain is regulated by positive (PAM) or negative (NAM) allosteric modulators binding to the 7-transmembrane domain (7TM). We report the cryo-electron microscopy structures of fully inactive and intermediate-active conformations of mGlu receptor bound to an antagonist and a NAM or an agonist and a PAM, respectively, as well as the crystal structure of the 7TM bound to a photoswitchable NAM.

[Recent advances in the structural biology of the class C G protein-coupled receptors: The metabotropic Glutamate receptor 5].

Class C GPCRs, that include metabotropic glutamate receptors (mGlu), taste receptors, GABA receptor and Calcium-sensing receptor, are unusual in terms of their molecular architecture and allosteric regulation. They all form obligatory dimers, dimerization being fundamental for their function. More specifically, the mGlu are activated by the main excitatory neurotransmitter, L-glutamate.

Mechanistic Insights into Light-Driven Allosteric Control of GPCR Biological Activity.

G protein-coupled receptors (GPCR), including the metabotrobic glutamate 5 receptor (mGlu), 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.

Development and validation of a mass spectrometry binding assay for mGlu5 receptor.

Mass spectrometry (MS) binding assays are a label-free alternative to radioligand or fluorescence binding assays, so the readout is based on direct mass spectrometric detection of the test ligand. The study presented here describes the development and validation of a highly sensitive, rapid, and robust MS binding assay for the quantification of the binding of the metabotropic glutamate 5 (mGlu5) negative allosteric modulator (NAM), MPEP (2-methyl-6-phenylethynylpyridine) at the mGlu5 allosteric binding site. The LC-ESI-MS/MS (liquid chromatography-electrospray ionization-tandem mass spectrometric) analytical method was established and validated with a deuterated analogue of MPEP as an internal standard.

Chloride ions stabilize the glutamate-induced active state of the metabotropic glutamate receptor 3.

Due to the essential roles of glutamate, detection and response to a large range of extracellular concentrations of this excitatory amino acid are necessary for the fine-tuning of brain functions. Metabotropic glutamate receptors (mGluRs) are implicated in shaping the activity of many synapses in the central nervous system. Among the eight mGluR subtypes, there is increasing interest in studying the mGlu receptor which has recently been linked to various diseases, including psychiatric disorders.

Optical control of pain with a photoactive mGlu receptor negative allosteric modulator.

Light-operated drugs constitute a major target in drug discovery, since they may provide spatiotemporal resolution for the treatment of complex diseases (i.e. chronic pain).

Shining Light on an mGlu5 Photoswitchable NAM: A Theoretical Perspective.

Metabotropic glutamate receptors (mGluRs) are important drug targets because of their involvement in several neurological diseases. Among mGluRs, mGlu5 is a particularly high-profile target because its positive or negative allosteric modulation can potentially treat schizophrenia or anxiety and chronic pain, respectively. Here, we computationally and experimentally probe the functional binding of a novel photoswitchable mGlu5 NAM, termed alloswitch-1, which loses its NAM functionality under violet light.

Overlapping binding sites drive allosteric agonism and positive cooperativity in type 4 metabotropic glutamate receptors.

Type 4 metabotropic glutamate (mGlu4) receptors are emerging targets for the treatment of various disorders. Accordingly, numerous mGlu4-positive allosteric modulators (PAMs) have been identified, some of which also display agonist activity. To identify the structural bases for their allosteric action, we explored the relationship between the binding pockets of mGlu4 PAMs with different chemical scaffolds and their functional properties.

Exploring the active conformation of cyclohexane carboxylate positive allosteric modulators of the type 4 metabotropic glutamate receptor.

The active conformation of a family of metabotropic glutamate receptor subtype 4 (mGlu4 ) positive allosteric modulators (PAMs) with the cyclohexane 1,2-dicarboxylic scaffold present in cis-2-(3,5-dichlorophenylcarbamoyl)cyclohexanecarboxylic acid (VU0155041) was investigated by testing structurally similar six-membered ring compounds that have a locked conformation. The norbornane and cyclohexane molecules designed as mGlu4 conformational probes and the enantiomers of the trans diastereomer were computationally characterized and tested in mGlu4 pharmacological assays. The results support a VU0155041 active conformation, with the chair cyclohexane having the aromatic amide substituent in an axial position and the carboxylate in an equatorial position.

Alleviating pain hypersensitivity through activation of type 4 metabotropic glutamate receptor.

Hyperactivity of the glutamatergic system is involved in the development of central sensitization in the pain neuraxis, associated with allodynia and hyperalgesia observed in patients with chronic pain. Herein we study the ability of type 4 metabotropic glutamate receptors (mGlu4) to regulate spinal glutamate signaling and alleviate chronic pain. We show that mGlu4 are located both on unmyelinated C-fibers and spinal neurons terminals in the inner lamina II of the spinal cord where they inhibit glutamatergic transmission through coupling to Cav2.

Integrated synthetic, pharmacological, and computational investigation of cis-2-(3,5-dichlorophenylcarbamoyl)cyclohexanecarboxylic acid enantiomers as positive allosteric modulators of metabotropic glutamate receptor subtype 4.

2-(3,5-Dichlorophenylcarbamoyl)cyclohexanecarboxylic acid (1) is a potent and selective positive allosteric modulator of metabotropic glutamate receptor subtype 4 (mGluR4). The activity of 1 was reported to reside in the cis diastereomer with equal potency between its enantiomeric forms (Niswender et al., Mol.

D-myo-inositol 1-phosphate as a surrogate of D-myo-inositol 1,4,5-tris phosphate to monitor G protein-coupled receptor activation.

Phospholipase C beta (PLC-beta)-coupled G protein-coupled receptor (GPCR) activities traditionally are assessed by measuring Ca2+ triggered by D-myo-inositol 1,4,5-trisphosphate (IP3), a PLC-beta hydrolysis product, or by measuring the production of inositol phosphate using cumbersome radioactive assays. A specific detection of IP3 production was also established using IP3 binding proteins. The short lifetime of IP3 makes this detection very challenging in measuring GPCR responses.

Coupling of agonist binding to effector domain activation in metabotropic glutamate-like receptors.

Many membrane receptors are made of a ligand binding domain and an effector domain mediating intracellular signaling. This is the case for the metabotropic glutamate-like G-protein-coupled receptors. How ligand binding leads to the active conformation of the effector domain in such receptors is largely unknown.

Asymmetric functioning of dimeric metabotropic glutamate receptors disclosed by positive allosteric modulators.

The recent discovery of positive allosteric modulators (PAMs) for G-protein-coupled receptors open new possibilities to control a number of physiological and pathological processes. Understanding the mechanism of action of such compounds will provide new information on the activation process of these important receptors. Within the last 10 years, a number of studies indicate that G-protein-coupled receptors can form dimers, but the functional significance of this phenomenon remains elusive.