Molecular Determinants of High Affinity Binding to Group III Metabotropic Glutamate Receptors

Rosemond, Erica; Peltekova, Vanya; Naples, Mark; Thøgersen, Henning; Hampson, David R.

doi:10.1074/jbc.m110476200

Cited by 48 publications

(52 citation statements)

References 30 publications

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“…The microenvironment within the mGluR4 binding pocket encompasses several positively charged amino acids that recognize the negatively charged phosphonate group of group III selective compounds such as L-AP4 and L-SOP. Our finding that the mGluR4 residues, K74, E287, and K317, contribute collectively to subgroupselective ligand binding are in agreement with previous mutagenesis studies on mGluR4 (14) and analogous mutations in other mGluR subtypes (15)(16)(17). The Ser-313 residue has not previously been identified as important for ligand binding and subtype selectivity, and even though it was not as effective as the others, it still showed a clear increase in affinity, especially in the case of quisqualic acid.…”

Section: Discussionsupporting

confidence: 79%

“…The rationale by which mutations were chosen was based on sequence alignment of the mGluR ATDs (Table I) (14) and by comparing the homology model of mGluR4 with the crystal structure of mGluR1. The non-conserved residues, Lys-74 in lobe I and Glu-287, Ser-313, and Lys-317 in lobe II (see Table I), were chosen for this study on the grounds that they lie within the glutamate binding pocket and are oriented toward the distal carboxylate of glutamate, which is presumably supplanted by the heterocyclic rings of quisqualic acid and ibotenic acid (see Fig.…”

Section: Resultsmentioning

confidence: 99%

“…In addition, certain amino acid residues involved in selectivity might be overlooked if a shift in ligand binding mode or hydrogen bonding architecture allowed the change to alanine to be accommodated. For example, Rosemond et al (14) showed that the mGluR4 K74A mutant displayed no (32)); mGluR1, quisqualic acid docked to experimental structure (Protein Data Bank accession number 1EWK (7)); mGluR4 and mutants, (5R)-and (5S)-quasidiasteromers of (S)-quisqualic acid docked to homology built models (Glide) and co-minimized (Macromodel). Emodel in Glide (final column) was used to predict the most favorable binding pose at each receptor.…”

Section: Discussionmentioning

confidence: 99%

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Mutation-induced Quisqualic Acid and Ibotenic Acid Affinity at the Metabotropic Glutamate Receptor Subtype 4

Hermit

Greenwood

Bräuner‐Osborne

2004

Journal of Biological Chemistry

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The metabotropic glutamate receptors (mGluRs) are key modulators of excitatory neurotransmission in the central nervous system. The eight mGluR subtypes are seven trans-membrane-spanning proteins that possess a large extracellular amino-terminal domain in which the endogenous ligand binding pocket resides. In this study, we have identified four non-conserved amino acid residues that are essential for differentiating mGluR1 from mGluR4. Our approach has been to increase the affinity of the classic mGluR1 agonists, quisqualic acid and ibotenic acid, at mGluR4 by making various point mutations that mimicked mGluR1 residues. Based on ligand docking to homology models, the non-conserved residues, Lys-74, Glu-287, Ser-313, and Lys-317, were chosen for the mutational studies and all of the mutations proved capable of partially or completely restoring the affinities of the ligands. In particular, the mutations K74Y and K317R induced dramatic triple-order-of-magnitude increases in the affinity of ibotenic acid at mGluR4, making the affinity equivalent to that of mGluR1. Furthermore, the affinity of quisqualic acid at mGluR4 was increased to the same level as mGluR1 by the two double mutations, K74Y/K317R and K74Y/E287G. Advanced analysis of ligand conformation and docking procedures were used for the interpretation of these results. The study shows that mGluR subtype selectivity results from a complex interplay of residues shaping the binding pocket, rather than being attributable to a single specific ligand-receptor interaction.The excitatory neurotransmitter glutamate elicits and modulates synaptic responses in the central nervous systems by activating two families of receptors: ligand-gated cation channels termed ionotropic glutamate receptors (iGluRs) 1 and Gprotein-coupled receptors termed metabotropic glutamate receptors (mGluRs). To date, the use of cloning techniques has led to the identification of eight mGluR subtypes and multiple splice variants, which have been subdivided into three groups (I-III) based on their sequence homology, signal transduction mechanisms, and pharmacological properties (1). The stimulatory group I receptors (mGluR1 and mGluR5) give rise to postsynaptic increases in cytoplasmic calcium and/or presynaptic increases in neurotransmitter release, whereas groups II (mGlu2 and mGlu3) and III (mGlu4, mGlu6, mGlu7, and mGlu8) are primarily localized presynaptically and typically inhibit neurotransmission as autoreceptors either at glutamatergic synapses or at other neurotransmitter-releasing synapses (2). mGluRs are seven trans-membrane-spanning proteins that possess a large extracellular amino-terminal domain (ATD), characteristic of the family C G-protein coupled receptors to which they belong. The binding site of the endogenous ligand is contained within the ATD (3, 4), which is composed of two lobes connected by a hinge region, giving rise to a closed and an open form. The two lobes are thought to close upon binding the agonist such as a Venus flytrap when touched by an insect (5, 6). Recen...

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Section: Discussionsupporting

confidence: 79%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Mutation-induced Quisqualic Acid and Ibotenic Acid Affinity at the Metabotropic Glutamate Receptor Subtype 4

Hermit

Greenwood

Bräuner‐Osborne

2004

Journal of Biological Chemistry

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“…These studies revealed two major conformational changes resulting from agonist binding. A first one is the closure of at least one VFTM in the dimer, as expected from modeling studies of other family 3 GPCRs (6,(8)(9)(10)20). Indeed, glutamate binds to lobe I within the cleft that separates both lobes and also can interact with residues from lobe II leading to the stabilization of a closed state.…”

mentioning

confidence: 73%

“…As other GPCRs, family 3 receptors have a heptahelical domain (HD) responsible for G protein activation (2). However, they possess a large, extracellular domain structurally similar to bacterial periplasmic-binding proteins that contain the agonist-binding site (3)(4)(5)(6)(7)(8)(9)(10). As clearly shown by the solved x-ray structure of the glutamate-binding domain of the metabotropic glutamate receptor type 1 (mGlu1 receptor) (11), this domain is constituted of two lobes separated by a large cleft on which agonists bind and is called a Venus flytrap module (VFTM).…”

mentioning

confidence: 99%

Closure of the Venus flytrap module of mGlu8 receptor and the activation process: Insights from mutations converting antagonists into agonists

Bessis

Rondard

Gaven

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

110

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Ca 2؉ , pheromones, sweet taste compounds, and the main neurotransmitters glutamate and ␥-aminobutyric acid activate G proteincoupled receptors (GPCRs) that constitute the GPCR family 3. These receptors are dimers, and each subunit has a large extracellular domain called a Venus flytrap module (VFTM), where agonists bind. This module is connected to a heptahelical domain that activates G proteins. Recently, the structure of the dimer of mGlu1 VFTMs revealed two important conformational changes resulting from glutamate binding. First, agonists can stabilize a closed state of at least one VFTM in the dimer. Second, the relative orientation of the two VFTMs in the dimer is different in the presence of glutamate, such that their C-terminal ends (which are connected to the G protein-activating heptahelical domain) become closer by more than 20 Å. This latter change in orientation has been proposed to play a key role in receptor activation. To elucidate the respective role of VFTM closure and the change in orientation of the VFTMs in family 3 GPCR activation, we analyzed the mechanism of action of the mGlu8 receptor antagonists ACPT-II and MAP4. Molecular modeling studies suggest that these two compounds prevent the closure of the mGlu8 VFTM because of ionic and steric hindrance, respectively. We show here that the replacement of the residues responsible for these hindrances (Asp-309 and Tyr-227, respectively) by Ala allows ACPT-II or MAP4 to fully activate the receptors. These data are consistent with the requirement of the VFTM closure for family 3 GPCR activation.

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Night blindness-associated mutations in the ligand-binding, cysteine-rich, and intracellular domains of the metabotropic glutamate receptor 6 abolish protein trafficking

et al. 2007

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Mutations in the GRM6 gene, which encodes the metabotropic glutamate receptor 6 (mGluR6), lead to autosomal recessive congenital stationary night blindness (CSNB), which is characterized by loss of night vision due to a defect in signal transmission from photoreceptor to the adjacent ON-bipolar cells in the retina. So far, the sequence variations that have been described in six different families include nonsense, frameshift, and missense mutations. Here we investigated the impact of missense mutations in the ligand-binding domain, a conserved cysteine-rich domain, and the intracellular domain on the localization of the protein. We visualized and discriminated between surface and intracellular protein. Here we demonstrate that the wild-type (wt) protein localizes to the cell surface, and to endoplasmic reticulum (ER) and Golgi compartments. This also holds true for a mGluR6 variant containing a polymorphic, nondisease-associated amino acid exchange in the ligand-binding domain. In contrast, all disease-associated missense mutations lead to retention of the protein in the ER, while dimerization seems not to be affected. This is the first report that shows that CSNB-associated mutations in three different domains of mGluR6 abolish proper protein trafficking. We propose that the ligand-binding and the poorly characterized cysteine-rich domains, in addition to the intracellular domains, have a pivotal role in correct trafficking of metabotropic glutamate receptors to the cell surface.

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Molecular Determinants of High Affinity Binding to Group III Metabotropic Glutamate Receptors

Cited by 48 publications

References 30 publications

Mutation-induced Quisqualic Acid and Ibotenic Acid Affinity at the Metabotropic Glutamate Receptor Subtype 4

Mutation-induced Quisqualic Acid and Ibotenic Acid Affinity at the Metabotropic Glutamate Receptor Subtype 4

Closure of the Venus flytrap module of mGlu8 receptor and the activation process: Insights from mutations converting antagonists into agonists

Night blindness-associated mutations in the ligand-binding, cysteine-rich, and intracellular domains of the metabotropic glutamate receptor 6 abolish protein trafficking

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