scholarly journals Allosteric modulators enhance agonist efficacy by increasing the residence time of a GPCR in the active state

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Anne-Marinette Cao ◽  
Robert B. Quast ◽  
Fataneh Fatemi ◽  
Philippe Rondard ◽  
Jean-Philippe Pin ◽  
...  
Keyword(s):  
Single Molecule ◽  
Metabotropic Glutamate Receptors ◽  
Transmembrane Domain ◽  
Active State ◽  
Brain Diseases ◽  
Allosteric Modulators ◽  
Metabotropic Glutamate ◽  
Single Molecule Fret ◽  
Agonist Action ◽  
Subtype Selectivity

AbstractMuch hope in drug development comes from the discovery of positive allosteric modulators (PAM) that display target subtype selectivity and act by increasing agonist potency and efficacy. How such compounds can allosterically influence agonist action remains unclear. Metabotropic glutamate receptors (mGlu) are G protein-coupled receptors that represent promising targets for brain diseases, and for which PAMs acting in the transmembrane domain have been developed. Here, we explore the effect of a PAM on the structural dynamics of mGlu2 in optimized detergent micelles using single molecule FRET at submillisecond timescales. We show that glutamate only partially stabilizes the extracellular domains in the active state. Full activation is only observed in the presence of a PAM or the Gi protein. Our results provide important insights on the role of allosteric modulators in mGlu activation, by stabilizing the active state of a receptor that is otherwise rapidly oscillating between active and inactive states.

scholarly journals Single molecule analysis reveals positive allosteric modulators are required to stabilize the active state of a metabotropic glutamate receptor

2021 ◽  
Author(s):  
Anne-Marinette Cao ◽  
Robert B. Quast ◽  
Fataneh Fatemi ◽  
Philippe Rondard ◽  
Jean-Philippe Pin ◽  
...  
Keyword(s):  
Single Molecule ◽  
Metabotropic Glutamate Receptors ◽  
Metabotropic Glutamate Receptor ◽  
Brain Diseases ◽  
Allosteric Modulators ◽  
Fast Kinetics ◽  
Single Molecule Level ◽  
Metabotropic Glutamate ◽  
Subtype Selectivity ◽  
Positive Allosteric Modulators

AbstractMetabotropic glutamate receptors (mGlu) are G protein-coupled receptors that represent promising targets for brain diseases. Much hope in drug development come from the discovery of positive allosteric modulators that display subtype selectivity, and act by increasing agonist potency, as well as efficacy in most cases. How such compounds can influence agonist efficacy remains unclear. Here, we explore the structural dynamics of the full-length mGlu2 dimers at submillisecond timescales using single molecule FRET on diffusing receptors in optimized detergent micelles. We show that glutamate binding in the Venus flytrap extracellular domains does not stabilize fully the receptors in their active states. The full activation of all receptors can only be observed in the presence of either a positive allosteric modulator or the Gi protein. Our results provide important new insights on the fast kinetics and the action of the allosteric modulators on mGlu activation at the single molecule level.

scholarly journals Metabotropic glutamate receptors (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

2019 ◽  
Vol 2019 (4) ◽  
Author(s):  
Francine Acher ◽  
Giuseppe Battaglia ◽  
Hans Bräuner-Osborne ◽  
P. Jeffrey Conn ◽  
Robert Duvoisin ◽  
...  
Keyword(s):  
Glutamate Receptors ◽  
G Protein ◽  
Metabotropic Glutamate Receptors ◽  
Transmembrane Domain ◽  
Acid Group ◽  
Allosteric Modulators ◽  
Group Iii ◽  
Metabotropic Glutamate ◽  
Group I ◽  
Group Ii

Metabotropic glutamate (mGlu) receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Metabotropic Glutamate Receptors [334]) are a family of G protein-coupled receptors activated by the neurotransmitter glutamate. The mGlu family is composed of eight members (named mGlu1 to mGlu8) which are divided in three groups based on similarities of agonist pharmacology, primary sequence and G protein coupling to effector: Group-I (mGlu1 and mGlu5), Group-II (mGlu2 and mGlu3) and Group-III (mGlu4, mGlu6, mGlu7 and mGlu8) (see Further reading).Structurally, mGlu are composed of three juxtaposed domains: a core G protein-activating seven-transmembrane domain (TM), common to all GPCRs, is linked via a rigid cysteine-rich domain (CRD) to the Venus Flytrap domain (VFTD), a large bi-lobed extracellular domain where glutamate binds. The structures of the VFTD of mGlu1, mGlu2, mGlu3, mGlu5 and mGlu7 have been solved [190, 262, 255, 386]. The structure of the 7 transmembrane (TM) domains of both mGlu1 and mGlu5 have been solved, and confirm a general helical organization similar to that of other GPCRs, although the helices appear more compacted [85, 415, 59]. mGlu form constitutive dimers crosslinked by a disulfide bridge. Recent studies revealed the possible formation of heterodimers between either group-I receptors, or within and between group-II and -III receptors [86]. Although well characterized in transfected cells, co-localization and specific pharmacological properties also suggest the existence of such heterodimers in the brain [422, 257]. The endogenous ligands of mGlu are L-glutamic acid, L-serine-O-phosphate, N-acetylaspartylglutamate (NAAG) and L-cysteine sulphinic acid. Group-I mGlu receptors may be activated by 3,5-DHPG and (S)-3HPG [29] and antagonized by (S)-hexylhomoibotenic acid [223]. Group-II mGlu receptors may be activated by LY389795 [256], LY379268 [256], eglumegad [337, 416], DCG-IV and (2R,3R)-APDC [338], and antagonised by eGlu [161] and LY307452 [408, 100]. Group-III mGlu receptors may be activated by L-AP4 and (R,S)-4-PPG [125]. An example of an antagonist selective for mGlu receptors is LY341495, which blocks mGlu2 and mGlu3 at low nanomolar concentrations, mGlu8 at high nanomolar concentrations, and mGlu4, mGlu5, and mGlu7 in the micromolar range [176]. In addition to orthosteric ligands that directly interact with the glutamate recognition site, allosteric modulators that bind within the TM domain have been described. Negative allosteric modulators are listed separately. The positive allosteric modulators most often act as ‘potentiators’ of an orthosteric agonist response, without significantly activating the receptor in the absence of agonist.

Allosteric modulators of metabotropic glutamate receptors: lessons learnt from mGlu1, mGlu2 and mGlu5 potentiators and antagonists

2004 ◽  
Vol 32 (5) ◽  
pp. 881-887 ◽  
Author(s):  
M.P. Johnson ◽  
E.S. Nisenbaum ◽  
T.H. Large ◽  
R. Emkey ◽  
M. Baez ◽  
...  
Keyword(s):  
Glutamate Receptors ◽  
G Protein ◽  
Metabotropic Glutamate Receptors ◽  
Focal Point ◽  
Glutamate Release ◽  
Pharmacological Properties ◽  
Allosteric Modulators ◽  
Metabotropic Glutamate ◽  
Subtype Selectivity ◽  
Mglu2 Receptor

Although relatively few G-protein-coupled receptors are Class C, in recent years, this small family of receptors has become a focal point for the discovery of new and exciting allosteric modulators. The mGlu (metabotropic glutamate) receptors are illustrative in the discovery of both positive and/or negative allosteric modulators with unique pharmacological properties. For instance, allosteric modulators of the mGlu2 receptor act as potentiators of glutamate responses in clonal expression systems and in native tissue assays. These potentiators act to increase the affinity of orthosteric agonists for the mGlu2 receptor and shift potency curves for the agonist to the left. In electrophysiological experiments, the potentiators show a unique activation-state-dependent presynaptic inhibition of glutamate release and significantly enhance the receptor-mediated increase in G-protein binding, as seen with autoradiography. Similarly, potentiators of mGlu5 have been described, as well as allosteric antagonists or inverse agonists of mGlu1 and mGlu5. Binding and activity of the modulators have recently indicated that positive and negative allosteric sites can be, but are not necessarily, overlapping. Compared with orthosteric ligands, these modulators display a unique degree of subtype selectivity within the highly conserved mGlu family of receptors and can have very distinct pharmacological properties, such as neuronal frequency-dependent activity. This short review describes some of the unique features of these mGlu1, mGlu2 and mGlu5 allosteric modulators.

scholarly journals Conformational pathway provides unique sensitivity to a synaptic mGluR

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Chris H. Habrian ◽  
Joshua Levitz ◽  
Vojtech Vyklicky ◽  
Zhu Fu ◽  
Adam Hoagland ◽  
...  
Keyword(s):  
Single Molecule ◽  
Metabotropic Glutamate Receptors ◽  
Dynamic Range ◽  
High Sensitivity ◽  
G Protein Coupled Receptors ◽  
Metabotropic Glutamate ◽  
Single Molecule Fret ◽  
Broad Dynamic Range ◽  
Maximal Activation ◽  
G Protein Coupled

AbstractMetabotropic glutamate receptors (mGluRs) are dimeric G-protein–coupled receptors that operate at synapses. Macroscopic and single molecule FRET to monitor structural rearrangements in the ligand binding domain (LBD) of the mGluR7/7 homodimer revealed it to have an apparent affinity ~4000-fold lower than other mGluRs and a maximal activation of only ~10%, seemingly too low for activation at synapses. However, mGluR7 heterodimerizes, and we find it to associate with mGluR2 in the hippocampus. Strikingly, the mGluR2/7 heterodimer has high affinity and efficacy. mGluR2/7 shows cooperativity in which an unliganded subunit greatly enhances activation by agonist bound to its heteromeric partner, and a unique conformational pathway to activation, in which mGluR2/7 partially activates in the Apo state, even when its LBDs are held open by antagonist. High sensitivity and an unusually broad dynamic range should enable mGluR2/7 to respond to both glutamate transients from nearby release and spillover from distant synapses.

scholarly journals Differences in interactions between transmembrane domains tune the activation of metabotropic glutamate receptors

2021 ◽  
Author(s):  
Jordana K. Thibado ◽  
Jean-Yves Tano ◽  
Joon Lee ◽  
Leslie Salas-Estrada ◽  
Davide Provasi ◽  
...  
Keyword(s):  
Glutamate Receptors ◽  
Single Molecule ◽  
Metabotropic Glutamate Receptors ◽  
Transmembrane Domain ◽  
Critical Role ◽  
Transmembrane Helix ◽  
Variable Region ◽  
Metabotropic Glutamate ◽  
Initial Activation ◽  
G Protein Coupled

AbstractThe metabotropic glutamate receptors (mGluRs) form a family of neuromodulatory G protein-coupled receptors that contain both a seven-helix transmembrane domain (TMD) and a large extracellular ligand-binding domain (LBD) which enables stable dimerization. While numerous studies have revealed variability across subtypes in the initial activation steps at the level of LBD dimers, an understanding of inter-TMD interaction and rearrangement remains limited. Here we use a combination of single molecule fluorescence, molecular dynamics, functional assays, and conformational sensors to reveal that distinct TMD assembly properties drive differences between mGluR subtypes. We uncover a variable region within transmembrane helix 4 (TM4) that contributes to homo- and heterodimerization in a subtype-specific manner and tunes orthosteric, allosteric and basal activation. We also confirm a critical role for a conserved inter-TM6 interface in stabilizing the active state during orthosteric or allosteric activation. Together this study informs a working model of inter-TMD rearrangement that drives mGluR function.

scholarly journals Structural Dynamics of the Full-Length Metabotropic Glutamate Receptors by Single-Molecule FRET

2016 ◽  
Vol 110 (3) ◽  
pp. 637a
Author(s):  
Anne-Marinette Cao ◽  
Fataneh Fatemi ◽  
Philippe Rondard ◽  
Jean-Philippe Pin ◽  
Emmanuel Margeat
Keyword(s):  
Glutamate Receptors ◽  
Structural Dynamics ◽  
Single Molecule ◽  
Metabotropic Glutamate Receptors ◽  
Full Length ◽  
Metabotropic Glutamate ◽  
Single Molecule Fret

scholarly journals Differences in interactions between transmembrane domains tune the activation of metabotropic glutamate receptors

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Jordana K Thibado ◽  
Jean-Yves Tano ◽  
Joon Lee ◽  
Leslie Salas-Estrada ◽  
Davide Provasi ◽  
...  
Keyword(s):  
Glutamate Receptors ◽  
Single Molecule ◽  
Metabotropic Glutamate Receptors ◽  
Transmembrane Domain ◽  
Critical Role ◽  
Transmembrane Helix ◽  
Variable Region ◽  
Metabotropic Glutamate ◽  
Initial Activation ◽  
G Protein Coupled

The metabotropic glutamate receptors (mGluRs) form a family of neuromodulatory G protein-coupled receptors that contain both a seven-helix transmembrane domain (TMD) and a large extracellular ligand-binding domain (LBD) which enables stable dimerization. While numerous studies have revealed variability across subtypes in the initial activation steps at the level of LBD dimers, an understanding of inter-TMD interaction and rearrangement remains limited. Here we use a combination of single molecule fluorescence, molecular dynamics, functional assays, and conformational sensors to reveal that distinct TMD assembly properties drive differences between mGluR subtypes. We uncover a variable region within transmembrane helix 4 (TM4) that contributes to homo- and heterodimerization in a subtype-specific manner and tunes orthosteric, allosteric and basal activation. We also confirm a critical role for a conserved inter-TM6 interface in stabilizing the active state during orthosteric or allosteric activation. Together this study shows that inter-TMD assembly and dynamic rearrangement drive mGluR function with distinct properties between subtypes.

Biased agonism and allosteric modulation of metabotropic glutamate receptor 5

2018 ◽  
Vol 132 (21) ◽  
pp. 2323-2338 ◽  
Author(s):  
Phuc N.H. Trinh ◽  
Lauren T. May ◽  
Katie Leach ◽  
Karen J. Gregory
Keyword(s):  
Glutamate Receptor ◽  
Metabotropic Glutamate Receptors ◽  
Metabotropic Glutamate Receptor ◽  
Allosteric Modulation ◽  
Receptor Subtype ◽  
Allosteric Modulators ◽  
Biased Agonism ◽  
Metabotropic Glutamate ◽  
Promising Target ◽  
The Central Nervous System

Metabotropic glutamate receptors belong to class C G-protein-coupled receptors and consist of eight subtypes that are ubiquitously expressed throughout the central nervous system. In recent years, the metabotropic glutamate receptor subtype 5 (mGlu5) has emerged as a promising target for a broad range of psychiatric and neurological disorders. Drug discovery programs targetting mGlu5 are primarily focused on development of allosteric modulators that interact with sites distinct from the endogenous agonist glutamate. Significant efforts have seen mGlu5 allosteric modulators progress into clinical trials; however, recent failures due to lack of efficacy or adverse effects indicate a need for a better understanding of the functional consequences of mGlu5 allosteric modulation. Biased agonism is an interrelated phenomenon to allosterism, describing how different ligands acting through the same receptor can differentially influence signaling to distinct transducers and pathways. Emerging evidence demonstrates that allosteric modulators can induce biased pharmacology at the level of intrinsic agonism as well as through differential modulation of orthosteric agonist-signaling pathways. Here, we present key considerations in the discovery and development of mGlu5 allosteric modulators and the opportunities and pitfalls offered by biased agonism and modulation.

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