{"gene":"GRM5","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":1995,"finding":"mGluR5 is a G-protein coupled receptor that couples to phosphatidylinositol hydrolysis and calcium mobilization via inositol triphosphate. Immunoelectron microscopy in rat brain showed it is predominantly localized on postsynaptic dendritic spines and shafts, with some presynaptic axon terminal labeling, suggesting a presynaptic autoreceptor role in addition to postsynaptic function.","method":"Western blot (receptor-specific antibody), immunocytochemistry, electron microscopy, transfection of nonneuronal cells","journal":"The Journal of comparative neurology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct subcellular localization by electron microscopy with receptor-specific antibody, replicated across hippocampus and cortex, confirmed by Western blot in multiple brain regions","pmids":["7636025"],"is_preprint":false},{"year":1995,"finding":"mGluR5 protein expression is dramatically higher during early hypothalamic development compared to adults (sixfold decrease in hypothalamus, threefold in cortex with maturation). Ultrastructurally, mGluR5 localizes to the cytoplasmic face of the plasma membrane on hypothalamic dendrites, dendritic spines, and perikarya, and is also expressed on astrocyte processes surrounding asymmetric synapses.","method":"Western blot, Northern blot, immunocytochemistry, electron microscopy","journal":"The Journal of comparative neurology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (Western, Northern, immunoEM) documenting developmental regulation and subcellular localization, single lab but comprehensive","pmids":["8576426"],"is_preprint":false},{"year":1997,"finding":"In native astrocytes expressing mGluR5 without mGluR1 interference, mGluR5 activation induces phosphoinositide (PI) hydrolysis without stimulating cAMP formation. Prolonged agonist exposure causes two-phase desensitization: an early phase (completed by 1 h) independent of receptor internalization or PKC/PKA phosphorylation, and a late phase (by 24 h) associated with receptor down-regulation. Resensitization after prolonged exposure requires new protein synthesis.","method":"Pharmacological assays (PI hydrolysis, cAMP measurement), phorbol ester treatment, receptor down-regulation assays in cultured astrocytes","journal":"Journal of neurochemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — native cell expression system with multiple orthogonal pharmacological approaches dissecting desensitization mechanisms, single lab","pmids":["9202306"],"is_preprint":false},{"year":2001,"finding":"Pharmacological activation of mGluR5 (but not mGluR1) by DHPG is sufficient to induce long-term depression (LTD) in hippocampal CA1. This mGluR5-LTD is saturable, mechanistically distinct from NMDAR-dependent LTD, and shares an expression mechanism with protein synthesis-dependent LTD induced by synaptic stimulation.","method":"Electrophysiology (field recordings in hippocampal slices), selective pharmacological tools (DHPG, mGluR5 antagonists), protein synthesis inhibitors","journal":"Journal of neurophysiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean electrophysiological loss-of-function with selective antagonists, replicated across multiple experimental conditions in the same study","pmids":["11431513"],"is_preprint":false},{"year":2001,"finding":"mGluR5 expressed on peripheral terminals of primary afferent neurons mediates inflammatory hyperalgesia. Intraplantar but not intracerebroventricular or intrathecal injection of the selective mGluR5 antagonist MPEP reduces Freund's complete adjuvant-induced hind paw hyperalgesia. Group I mGluR agonist-induced mechanical hyperalgesia was blocked by MPEP but not by the mGluR1 antagonist 4-CPG.","method":"In vivo pharmacology (intraplantar, i.c.v., intrathecal microinjection), behavioral pain testing, in vivo electrophysiology (dorsal horn WDR neuron recordings), double-label immunohistochemistry (mGluR5 + βIII-tubulin; mGluR5 + TRPV1)","journal":"Neuropharmacology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal in vivo approaches (behavioral, electrophysiological, anatomical) with receptor-specific pharmacology in a single study","pmids":["11077066"],"is_preprint":false},{"year":2001,"finding":"mGluR5 is required for spatial learning and context-dependent fear conditioning. mGluR5 knockout mice are deficient in Morris water maze performance and contextual fear conditioning, establishing a pathway linking mGluR5 → PKC → Src → enhanced NMDAR open probability → LTP of NMDAR, necessary for spatial memory.","method":"Genetic knockout (mGluR5 null mice), Morris water maze, fear conditioning, hippocampal slice electrophysiology (LTP recording)","journal":"Physiology & behavior","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — genetic KO with defined behavioral readout and proposed mechanistic pathway, but mechanistic details (PKC/Src pathway) cited as from other work rather than directly demonstrated in this paper","pmids":["11566212"],"is_preprint":false},{"year":2003,"finding":"mGluR5 endocytosis occurs via a clathrin-independent, dynamin-2-dependent pathway. mGluR5a and mGluR5b internalize constitutively in COS-7 cells and neurons (axons and dendrites) even without ligand activation or in the presence of an inverse agonist. Dominant-negative Eps15 (clathrin pathway blocker) does not prevent mGluR5 endocytosis, but dynamin-2 is required.","method":"Transfection in COS-7 cells and hippocampal neurons, immunocytochemistry, quantitative image analysis, biochemical endocytosis assay, dominant-negative Eps15 constructs","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — dominant-negative genetic approach combined with biochemical and imaging assays, multiple orthogonal methods in a single lab study","pmids":["12529370"],"is_preprint":false},{"year":2003,"finding":"mGluR5 potentiates adenosine A2A receptor-mediated DARPP-32 phosphorylation at Thr-34 in neostriatal neurons by stimulating A2A receptor-coupled cAMP formation in an ERK-dependent manner. The action of mGluR5 requires A2A receptor activation by endogenous adenosine. Coactivation of mGluR5 and A2A receptors synergistically increases DARPP-32 phosphorylation. The effect is not dependent on PLC activation.","method":"Neostriatal slice pharmacology, DARPP-32 phosphorylation assays, selective receptor antagonists, kinase inhibitors (ERK, PLC, p38, CK1, Cdk5)","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple receptor antagonists and kinase inhibitors used to dissect signaling pathway in native tissue, mechanistic specificity established with multiple pharmacological tools","pmids":["12538871"],"is_preprint":false},{"year":2004,"finding":"mGluR5 expressed in HEK293 cells can both inhibit and potentiate NMDA receptor responses through distinct mechanisms. The inhibitory influence depends on Ca2+ release from stores (thapsigargin-sensitive) and PKC activation. Removal of these processes reveals a tonic mGluR5- and protein tyrosine kinase (PTK)-dependent potentiation of NMDA receptors. Protein tyrosine phosphatase (PTP) inhibitors occlude DHPG-induced NMDAR potentiation.","method":"Ca2+ imaging in HEK293 cells co-transfected with NR1a, NR2A, and mGlu5a; pharmacological dissection with thapsigargin, staurosporine, PTK inhibitors (genistein, PP2), PTP inhibitors (orthovanadate, PAO)","journal":"British journal of pharmacology","confidence":"Medium","confidence_rationale":"Tier 1-2 / Weak — reconstituted receptor co-expression system with multiple pharmacological tools, but single lab in heterologous cells only","pmids":["15210575"],"is_preprint":false},{"year":2006,"finding":"The PDZ scaffold NHERF-2 directly and selectively interacts with mGluR5 (not mGluR1a) via the second PDZ domain of NHERF-2 binding to the C-terminus of mGluR5. A single point mutation in mGluR5-CT completely disrupts this interaction. NHERF-2 co-immunoprecipitates with full-length mGluR5 in cells, and co-expression of NHERF-2 prolongs mGluR5-mediated calcium mobilization and potentiates mGluR5-mediated cell death.","method":"PDZ domain proteomic array screening, reverse overlay assay, point mutagenesis, co-immunoprecipitation, confocal microscopy, functional calcium assays, cell death assays, immunohistochemistry in mouse brain","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — PDZ array + mutagenesis + reciprocal co-IP + functional assay, multiple orthogonal methods in one study","pmids":["16891310"],"is_preprint":false},{"year":2007,"finding":"FMRP binds to the coding region of APP mRNA at a guanine-rich, G-quartet-like sequence. Stimulation of cortical synaptoneurosomes or neurons with the mGluR5 agonist DHPG increases APP translation in wild-type but not fmr-1 knockout samples. APP mRNA co-immunoprecipitates with FMRP in resting synaptoneurosomes, but this interaction is lost shortly after DHPG treatment, indicating that mGluR5 activation releases FMRP repression of APP mRNA translation.","method":"RNA-protein binding assays, co-immunoprecipitation (FMRP-APP mRNA), DHPG stimulation of synaptoneurosomes and primary neurons, metabolic labeling, fmr-1 KO mouse comparison, ELISA (Aβ levels)","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP, KO comparison, and direct translation assay with multiple orthogonal approaches in one study","pmids":["17298186"],"is_preprint":false},{"year":2008,"finding":"mGluR5 functions as a presynaptic autoreceptor on glutamatergic cortical nerve terminals, facilitating evoked glutamate exocytosis. Low concentrations of DHPG (0.3 μM) potentiate depolarization-evoked [3H]D-aspartate release via mGluR5 (blocked by MPEP, not CPCCOEt), whereas high concentrations (50 μM) act via mGluR1. This mGluR5 presynaptic role was confirmed by absence of potentiation in mGluR5 knockout synaptosome preparations.","method":"Synaptosome [3H]D-aspartate release assay, selective pharmacological antagonists (MPEP, CPCCOEt), mGluR5 knockout mice, Western blot of subsynaptic fractions, immunocytochemistry","journal":"Neuropharmacology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO validation combined with selective pharmacology and biochemical fractionation, multiple orthogonal approaches","pmids":["18625255"],"is_preprint":false},{"year":2009,"finding":"Activation of cell surface versus intracellular mGluR5 produces distinct Ca2+ signatures and unique downstream signaling. Both pools activate JNK, CaMK, and CREB phosphorylation; however, only intracellular mGluR5 activates ERK1/2 and Elk-1 phosphorylation, resulting in upregulation of c-fos and egr1 but not c-jun. CaMK kinase mediates CREB phosphorylation downstream of mGluR5, while CaMKII is upstream of intracellular mGluR5-mediated Elk-1 phosphorylation. Intracellular mGluR5 is activated by glutamate transported into the cell.","method":"Pharmacological isolation of surface vs. intracellular receptor pools (cell-impermeable vs. cell-permeable ligands), Ca2+ imaging, phospho-protein assays (JNK, CaMK, CREB, ERK1/2, Elk-1), kinase inhibitors, gene expression analysis, genetic approaches","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — pharmacological and genetic dissection of distinct signaling pools with multiple orthogonal signaling readouts in a single study","pmids":["19840937"],"is_preprint":false},{"year":2012,"finding":"PKC phosphorylation of mGluR5 at Ser901 enhances binding of the E3 ligase Siah-1A by displacing calmodulin (CaM). Siah-1A binding to mGluR5 decreases receptor surface expression and increases lysosomal degradation via endosomal trafficking. CaM and Siah-1A compete for mGluR5 binding in a phosphorylation-dependent manner in rat hippocampal neurons.","method":"Co-immunoprecipitation in hippocampal neurons, site-directed mutagenesis (S901 phosphorylation site), surface biotinylation assay, lysosomal degradation assays","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Moderate — mutagenesis of phosphorylation site, co-IP in neurons, trafficking assays with multiple orthogonal methods, single lab","pmids":["23152621"],"is_preprint":false},{"year":2012,"finding":"mGluR5 constitutively internalizes in HEK293 cells in the absence of ligand. Following endocytosis, the receptor enters the recycling compartment and returns to the cell surface; no lysosomal localization is observed after constitutive internalization.","method":"Surface biotinylation assays, antibody feeding internalization assay, confocal microscopy with organelle markers in HEK293 cells","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 3 / Weak — biochemical and imaging assays in heterologous cells, single lab, limited mechanistic depth","pmids":["22995293"],"is_preprint":false},{"year":2014,"finding":"Intracellular mGluR5 is present on the endoplasmic reticulum and nucleus of hippocampal CA1 neurons, where it colocalizes with the glutamate transporter EAAT3. Inhibition of EAAT3 prevented accumulation of radiolabeled agonist at intracellular mGluR5. Both intracellular and cell surface mGluR5 induced oscillatory Ca2+ responses, but only intracellular mGluR5 triggered sustained high-amplitude Ca2+ rises in dendrites. Activation of intracellular mGluR5 alone mediated both electrically- and chemically-induced LTD but not LTP in acute hippocampal slices.","method":"Pharmacological isolation of intracellular vs. surface mGluR5 (cell-permeable vs. impermeable ligands), Ca2+ imaging, radiolabeled agonist uptake assays, EAAT3 inhibition, acute hippocampal slice electrophysiology","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (Ca2+ imaging, electrophysiology, transporter inhibition) to demonstrate intracellular receptor function, single lab","pmids":["24672004"],"is_preprint":false},{"year":2015,"finding":"p11 (S100A10) directly binds to the cytoplasmic tail of mGluR5. p11 and mGluR5 mutually facilitate their accumulation at the plasma membrane, and p11 increases cell-surface availability of mGluR5. Overexpression of p11 potentiates mGluR5 agonist-induced calcium responses. Knockout of mGluR5 or p11 specifically in glutamatergic neurons causes depression-like behaviors, while knockout in GABAergic neurons causes antidepressant-like behaviors.","method":"Co-immunoprecipitation, cell-surface biotinylation, calcium signaling assays, cell-type-specific conditional knockout (glutamatergic vs. GABAergic neurons), behavioral assays","journal":"Molecular psychiatry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct binding (co-IP), surface expression assay, functional signaling validation, and cell-type-specific KO phenotypic readout, multiple orthogonal methods","pmids":["26370144"],"is_preprint":false},{"year":2015,"finding":"Biased mGluR5 PAMs can selectively potentiate mGluR5 coupling to Gαq-mediated signaling without potentiating mGluR5 modulation of NMDAR currents or NMDAR-dependent synaptic plasticity. VU0409551 produced antipsychotic-like and cognition-enhancing activity in animal models despite not potentiating NMDAR function, demonstrating that NMDAR current modulation is not required for in vivo efficacy of mGluR5 PAMs.","method":"Electrophysiology (hippocampal slice NMDAR currents), calcium signaling assays (Gαq), behavioral models (psychosis, cognition), selective PAM pharmacology","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (electrophysiology, signaling assays, behavior) using biased pharmacological tool in both in vitro and in vivo systems","pmids":["25937172"],"is_preprint":false},{"year":2016,"finding":"In spinal dorsal horn neurons, >80% of mGluR5 is intracellular, with ~60% located on nuclear membranes where activation produces sustained Ca2+ responses. Nerve injury increases nuclear mGluR5 expression and receptor-mediated pERK1/2, Arc/Arg3.1, and c-fos. Spinal blockade of intracellular (but not cell surface) mGluR5 reduces neuropathic pain behaviors. Blocking EAAT-3 to reduce intracellular glutamate mimics the effects of intracellular mGluR5 antagonism.","method":"Immunofluorescence/confocal microscopy (subcellular fractionation), Ca2+ imaging, intrathecal drug delivery (cell-impermeable vs. permeable mGluR5 antagonists), EAAT-3 inhibition, behavioral pain testing, Western blot (pERK1/2, Arc, c-fos)","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — pharmacological dissection of intracellular vs. surface mGluR5 with multiple orthogonal in vitro and in vivo readouts, linking intracellular GPCR to behavioral outcome","pmids":["26837579"],"is_preprint":false},{"year":2016,"finding":"mGluR5 (postsynaptic) and CB1 (presynaptic) receptors work cooperatively to promote neuroprotection against glutamate insult. Pharmacological blockade or genetic ablation of either receptor abolishes both CB1- and mGluR5-mediated neuroprotection. The neuroprotective mechanism involves MEK/ERK1/2 and PI3K/AKT signaling pathways, rather than reduced glutamate release or diminished intracellular Ca2+.","method":"Primary corticostriatal neuron cultures, pharmacological receptor blockade, genetic ablation, cell death assays, kinase inhibitors, signaling assays (ERK1/2, AKT phosphorylation)","journal":"Molecular brain","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — genetic and pharmacological approaches in primary neurons with multiple signaling readouts, single lab study","pmids":["27543109"],"is_preprint":false},{"year":2017,"finding":"mGluR5 agonist CHPG treatment increases RANTES production and amplifies irradiation-induced NF-κB activation in T lymphocytes, while mGluR5 inhibition with MPEP decreases RANTES after irradiation. mGluR5 receptors cluster following irradiation in T cells.","method":"T lymphocyte cell line (Jurkat E6.1), mGluR5 agonist/antagonist treatment, ELISA (RANTES), NF-κB/GFP reporter assay, immunofluorescence (receptor clustering)","journal":"Translational psychiatry","confidence":"Medium","confidence_rationale":"Tier 3 / Weak — single cell line, pharmacological approach with reporter assay, single lab","pmids":["29849049"],"is_preprint":false},{"year":2017,"finding":"Peripheral mGluR5 signaling sensitizes TRPV1 and TRPA1 via PKCε phosphorylation to produce thermal and mechanical hypersensitivity. Continuous facial skin injection of mGluR5 agonist (CHPG) or glutamate decreased pain thresholds, which were reversed by mGluR5 antagonist MTEP, TRPA1 antagonist, TRPV1 antagonist, or PKCε translocation inhibitor applied peripherally. PKCε phosphorylation in trigeminal ganglion was enhanced by glutamate treatment.","method":"In vivo pain behavioral assays, intraplantar pharmacological injections, Western blot (PKCε phosphorylation), immunohistochemistry (co-expression of mGluR5, TRPV1, TRPA1, PKCε)","journal":"Pain","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — multiple pharmacological tools and in vivo behavioral assays, but mechanistic pathway established pharmacologically not biochemically, single lab","pmids":["28621704"],"is_preprint":false},{"year":2017,"finding":"Melatonin/MT2 receptor signaling reduces pain by impeding Tet1-dependent demethylation of the mGluR5 promoter in spinal dorsal horn neurons. Spinal Tet1 gene transfer induces Tet1-mGluR5 promoter coupling, demethylation, and mGluR5 upregulation. Melatonin reverses Tet1-dependent mGluR5 promoter demethylation and associated mGluR5 expression and pain hypersensitivity via MT2 receptor.","method":"Intrathecal vector-mediated gene transfer, chromatin immunoprecipitation (Tet1-mGluR5 promoter), bisulfite sequencing (promoter methylation), intrathecal drug injection, behavioral pain testing, Western blot","journal":"Journal of pineal research","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — multiple orthogonal methods (ChIP, bisulfite sequencing, behavior, pharmacology) in a single lab study identifying epigenetic regulation of mGluR5","pmids":["28718992"],"is_preprint":false},{"year":2018,"finding":"Patients' IgG antibodies against mGluR5 (primarily IgG1, ±IgG2/IgG3) cause a significant and specific decrease of cell-surface synaptic and extrasynaptic mGluR5 without altering PSD-95 levels, demonstrating pathogenic effects of anti-mGluR5 antibodies in encephalitis.","method":"Cell-based assays (antibody application to rat hippocampal neurons), immunohistochemistry (brain), IgG subclass determination, quantitative receptor cluster analysis","journal":"Neurology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct experimental demonstration of antibody-induced receptor loss in neurons across multiple patients, but single methodological approach","pmids":["29703767"],"is_preprint":false},{"year":2018,"finding":"mGluR5 hypofunction in schizophrenia postmortem DLPFC is characterized by decreased Gq/11 coupling, reduced mGluR5 association with PI3K and Homer, increased serine and tyrosine phosphorylation of mGluR5 (causing desensitization), and altered protein-protein interactions with RGS4, Norbin, Preso1, and Tamalin. Reduced mGluR5-GluN physical association provides a mechanistic basis for impaired reciprocal mGluR5-NMDA receptor facilitation in schizophrenia.","method":"Co-immunoprecipitation (mGluR5-Gq/11, mGluR5-PI3K, mGluR5-Homer, mGluR5-GluN, mGluR5-RGS4, mGluR5-Norbin, mGluR5-Preso1, mGluR5-Tamalin), phosphorylation assays, agonist-induced signaling assays in postmortem tissue","journal":"Molecular psychiatry","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — multiple co-IP experiments in postmortem human tissue, replicated across multiple interaction partners, but postmortem tissue limitations apply","pmids":["30214040"],"is_preprint":false},{"year":2019,"finding":"Homer1a induction enhances mGluR5 signaling, resulting in increased mTOR pathway phosphorylation and upregulation of synaptic AMPA receptor expression. The antidepressant action of sleep deprivation and Homer1a induction requires mGluR5 activation specifically in excitatory CaMK2a neurons and depends on enhanced AMPA receptor activity, translation, and trafficking.","method":"Cell-permeable TAT-Homer1a peptide injection, conditional knockout (mGluR5 in CaMK2a+ excitatory neurons), electrophysiology, Western blot (mTOR phosphorylation), AMPA receptor surface expression assays, behavioral antidepressant assays","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Moderate — cell-type-specific conditional KO with multiple signaling and behavioral readouts, mechanistic pathway from mGluR5 to AMPA receptor validated in vivo","pmids":["31420117"],"is_preprint":false},{"year":2020,"finding":"D1 dopamine receptor and mGluR5 form heteromeric receptor complexes on cell surfaces that couple to Gq proteins and produce synergistic PLC signaling and intracellular calcium release in response to either glutamate or dopamine. In dopamine-denervated striatum (Parkinson's disease model), D1-mGluR5 nanocomplexes are upregulated, leading to excessive ERK activation and dyskinesia.","method":"Co-immunoprecipitation, proximity ligation assay (nanoscale interaction), BRET/FRET (heteromer confirmation), calcium signaling assays, PLC assay, ERK phosphorylation assay in rodent PD models, behavioral dyskinesia testing","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods confirming heteromer formation (co-IP, PLA, BRET/FRET) plus functional signaling consequences and in vivo behavioral validation","pmids":["32039920"],"is_preprint":false},{"year":2020,"finding":"FMRP deficiency in astroglia cell-autonomously upregulates miR-128-3p, which suppresses developmental mGluR5 expression in astrocytes. Selective in vivo inhibition of miR-128-3p in FMRP-deficient astroglia rescues decreased astroglial mGluR5 function. This FMRP→miR-128-3p→mGluR5 pathway is selective to astroglia and operates at the posttranscriptional level.","method":"Astrocyte-selective FMRP conditional knockout in vivo, miR-128-3p inhibition in vivo, mGluR5 functional assays, transcriptome and proteome profiling, Western blot","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo genetic rescue experiment (miRNA inhibition) combined with multiple profiling approaches, cell-autonomous mechanism established","pmids":["32958647"],"is_preprint":false},{"year":2022,"finding":"Astrocytic mGluR5, which transiently reemerges in adult somatosensory cortex astrocytes after nerve injury, drives Ca2+ signals and upregulates synaptogenic molecules (Thrombospondin-1, Glypican-4, Hevin), causing excess excitatory synaptogenesis and persistent mechanical allodynia. Astrocyte-specific deletion of mGluR5 abolishes all these events, establishing a causal role for astrocytic mGluR5 in pain-associated synaptic plasticity.","method":"Astrocyte-specific conditional knockout of mGluR5, Ca2+ imaging, immunohistochemistry (synaptogenic molecules), synaptic density quantification, behavioral pain testing (mechanical allodynia)","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — astrocyte-specific genetic KO with multiple orthogonal readouts (Ca2+ signals, molecular markers, synaptogenesis, behavior), mechanistic pathway from mGluR5 to allodynia established","pmids":["35319723"],"is_preprint":false},{"year":2022,"finding":"Treatment with the mGluR5 silent allosteric modulator (SAM) BMS-984923 prevents Aβ oligomer-induced aberrant synaptic mGluR5 signaling while preserving physiological glutamate responses, restoring synaptic density in Alzheimer's disease mouse models. SAM treatment prevents synaptic localization of complement component C1Q and synaptic engulfment, and normalizes neuronal gene expression patterns.","method":"Oral SAM drug treatment in aged AD mouse models (APPswe/PS1ΔE9, App/hMapt knock-in), [18F]FPEB PET for brain mGluR5 occupancy, [18F]SynVesT-1 PET for synaptic density (SV2A), single-nuclei transcriptomics, C1Q immunohistochemistry, synaptic engulfment assay, behavioral testing","journal":"Science translational medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo PET receptor occupancy, multiple AD mouse models, transcriptomics, and mechanistic complement pathway assays in a single comprehensive study","pmids":["35648810"],"is_preprint":false},{"year":2023,"finding":"mGluR5 is dynamically organized in perisynaptic nanodomains positioned close to but excluded from the synapse. The C-terminal domain of mGluR5 critically controls perisynaptic confinement and prevents synaptic entry. Forced recruitment of mGluR5 to the synapse (via inducible interaction system) acutely increases synaptic calcium responses, demonstrating that perisynaptic localization shapes synaptic function.","method":"Live-cell super-resolution imaging (single-molecule localization microscopy), inducible chemogenetic interaction system to overcome synaptic exclusion, synaptic calcium imaging, C-terminal domain mutagenesis/truncation","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — super-resolution imaging plus molecular tool to acutely manipulate receptor localization with functional synaptic readout, multiple orthogonal approaches in single study","pmids":["36646691"],"is_preprint":false},{"year":2024,"finding":"The dimeric class C GPCR mGlu5 activates through an asymmetric, stepwise millisecond allosteric mechanism. Agonist binding induces dimeric ectodomain compaction amplified by cysteine-rich domain association, which loosely brings the 7TM domains into proximity establishing an asymmetric TM6-TM6 interface. Positive allosteric modulators stabilize the active inter-domain 7TM interface and an open ICL2 conformation, creating a pseudo-cavity (ICL2, ICL3, TM3, C-terminus) that facilitates G protein coordination.","method":"Markov state models (atomistic MD simulations), transition pathway generation, experimental signaling assays (validating simulation predictions)","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — computational structural modeling with experimental signaling validation, but experimental structural validation (cryo-EM/crystal structure) not performed; primarily computational with limited experimental confirmation","pmids":["39209876"],"is_preprint":false}],"current_model":"GRM5/mGluR5 is a class C GPCR that couples to Gq/phospholipase C to drive IP3-dependent Ca2+ release and downstream kinase cascades (ERK, CaMK, CREB, Elk-1); it is organized in perisynaptic nanodomains through C-terminal interactions, internalizes via a clathrin-independent, dynamin-2-dependent pathway with constitutive recycling, and signals distinctly from cell-surface versus intracellular (ER/nuclear) membranes—intracellular activation requiring EAAT3-mediated glutamate transport and selectively driving ERK/Elk-1 and LTD; its activity is regulated by PKC-mediated phosphorylation at Ser901 that enhances Siah-1A binding over calmodulin to promote lysosomal trafficking, by p11/S100A10 binding to its cytoplasmic tail promoting surface expression, and by NHERF-2 PDZ interaction prolonging Ca2+ signaling; it forms functional heteromers with D1 receptors engaging Gq/PLC, interacts with Homer scaffolds to control trafficking and plasticity, synergizes with adenosine A2A receptors to regulate DARPP-32/cAMP signaling, and acts presynaptically to facilitate glutamate release; in neurons mGluR5 mediates protein-synthesis-dependent mGluR-LTD in the hippocampus and controls FMRP-dependent APP mRNA translation, while in astrocytes transient re-expression of mGluR5 drives synaptogenesis and modulates glutamate transporter function; in pathological states aberrant mGluR5 signaling—including D1-mGlu5 heteromer upregulation in dopamine-denervated striatum and Aβ oligomer-mediated synaptotoxic signaling via PrPC-mGluR5-Fyn—contributes to dyskinesia and Alzheimer's disease synaptic loss."},"narrative":{"mechanistic_narrative":"GRM5 (mGluR5) is a dimeric class C G-protein-coupled receptor that couples to Gq/phospholipase C to drive phosphoinositide hydrolysis and IP3-dependent Ca2+ mobilization, and is the principal group I metabotropic glutamate receptor controlling synaptic plasticity, sensory processing, and glial-neuronal signaling [PMID:7636025, PMID:9202306, PMID:39209876]. The receptor is concentrated postsynaptically on dendritic spines and shafts with presynaptic axon-terminal expression, and it acts as a perisynaptic autoreceptor whose C-terminal domain confines it to nanodomains adjacent to but excluded from the synapse, a localization that gates synaptic Ca2+ responses [PMID:7636025, PMID:18625255, PMID:36646691]. Activation of mGluR5 produces ERK, CaMK, and CREB signaling and is sufficient to induce protein-synthesis-dependent mGluR-LTD in hippocampal CA1 distinct from NMDAR-dependent LTD, while genetic loss impairs spatial learning and fear conditioning [PMID:11431513, PMID:11566212, PMID:19840937]. mGluR5 signals from both the plasma membrane and intracellular ER/nuclear membranes; the intracellular pool is supplied with glutamate by the transporter EAAT3 and selectively drives sustained Ca2+ rises, ERK1/2-Elk-1 signaling, immediate-early gene induction, and LTD, and underlies neuropathic pain behaviors [PMID:19840937, PMID:24672004, PMID:26837579]. Its surface availability and trafficking are tightly regulated: it internalizes constitutively via a clathrin-independent, dynamin-2-dependent route with recycling to the surface [PMID:12529370, PMID:22995293]; PKC phosphorylation at Ser901 displaces calmodulin to favor Siah-1A binding and lysosomal degradation [PMID:23152621]; and p11/S100A10 binding to the cytoplasmic tail and NHERF-2 PDZ interaction promote surface expression and prolong Ca2+ signaling, respectively [PMID:16891310, PMID:26370144]. mGluR5 is embedded in a wider receptor and scaffold network—forming Gq-coupled heteromers with D1 dopamine receptors, synergizing with adenosine A2A receptors to potentiate DARPP-32 phosphorylation, cooperating with CB1 receptors for neuroprotection, and engaging Homer scaffolds to drive mTOR-dependent AMPA receptor plasticity [PMID:12538871, PMID:27543109, PMID:31420117, PMID:32039920]. It links to translational control through FMRP, releasing FMRP repression of APP mRNA upon activation [PMID:17298186], and astrocytic mGluR5 transiently re-emerging after injury drives synaptogenesis and allodynia [PMID:35319723]. Aberrant mGluR5 signaling contributes to L-DOPA-induced dyskinesia via upregulated D1-mGlu5 nanocomplexes [PMID:32039920] and to Alzheimer's disease synaptic loss via Abeta-oligomer-driven aberrant signaling that allosteric modulators can normalize [PMID:35648810], and pathogenic anti-mGluR5 IgG antibodies cause receptor internalization in encephalitis [PMID:29703767].","teleology":[{"year":1995,"claim":"Established mGluR5 as a Gq-coupled receptor driving phosphoinositide hydrolysis and Ca2+ mobilization and mapped its predominantly postsynaptic, partly presynaptic and astroglial distribution, defining where it acts.","evidence":"Receptor-specific Western blot, immunocytochemistry, and immunoelectron microscopy in rat brain with transfection of nonneuronal cells","pmids":["7636025","8576426"],"confidence":"High","gaps":["Did not resolve functional differences between presynaptic and postsynaptic pools","Coupling partners beyond PI hydrolysis not addressed"]},{"year":1997,"claim":"Showed in native astrocytes that mGluR5 activation drives PI hydrolysis without cAMP and undergoes two-phase desensitization, distinguishing a phosphorylation-independent early phase from protein-synthesis-dependent resensitization.","evidence":"Pharmacological PI hydrolysis and cAMP assays with phorbol esters and down-regulation assays in cultured astrocytes","pmids":["9202306"],"confidence":"High","gaps":["Molecular mediators of early desensitization not identified","In vivo relevance not tested"]},{"year":2001,"claim":"Defined mGluR5 as both necessary and sufficient for protein-synthesis-dependent hippocampal LTD and for spatial/contextual memory, separating it mechanistically from NMDAR-dependent plasticity.","evidence":"Hippocampal slice electrophysiology with selective DHPG/antagonists and protein synthesis inhibitors; mGluR5 knockout mice in Morris water maze and fear conditioning","pmids":["11431513","11566212"],"confidence":"High","gaps":["Downstream PKC/Src pathway to memory was inferred not directly demonstrated","Subcellular site of LTD induction unresolved at this stage"]},{"year":2001,"claim":"Identified a peripheral pro-nociceptive role for mGluR5 on primary afferent terminals, localizing analgesic relevance to the periphery.","evidence":"Intraplantar/i.c.v./intrathecal MPEP, behavioral pain testing, dorsal-horn neuron recordings, and mGluR5/TRPV1 co-labeling","pmids":["11077066"],"confidence":"High","gaps":["Intracellular signaling linking peripheral mGluR5 to hyperalgesia not defined here"]},{"year":2003,"claim":"Revealed mGluR5 endocytoses constitutively through a clathrin-independent, dynamin-2-dependent route, redefining its trafficking distinct from canonical GPCR pathways.","evidence":"Imaging and biochemical endocytosis assays with dominant-negative Eps15 and dynamin-2 in COS-7 cells and neurons","pmids":["12529370"],"confidence":"High","gaps":["Post-endocytic fate (recycling vs degradation) not fully resolved","Adaptor proteins for the clathrin-independent route unknown"]},{"year":2003,"claim":"Showed mGluR5 cross-talks with adenosine A2A receptors to potentiate DARPP-32 phosphorylation via cAMP/ERK independently of PLC, establishing receptor synergy in striatum.","evidence":"Neostriatal slice pharmacology with receptor antagonists and kinase inhibitors, DARPP-32 phospho-assays","pmids":["12538871"],"confidence":"High","gaps":["Physical basis of mGluR5-A2A interaction not defined","In vivo behavioral consequence not tested here"]},{"year":2004,"claim":"Demonstrated bidirectional mGluR5 control of NMDAR responses—Ca2+/PKC-dependent inhibition versus tonic tyrosine-kinase-dependent potentiation—revealing context-dependent crosstalk.","evidence":"Ca2+ imaging in HEK293 cells co-expressing NMDAR subunits with thapsigargin, PKC, PTK, and PTP inhibitors","pmids":["15210575"],"confidence":"Medium","gaps":["Heterologous cells only","Native neuronal validation absent"]},{"year":2006,"claim":"Identified NHERF-2 as a selective C-terminal PDZ partner of mGluR5 that prolongs Ca2+ signaling and potentiates excitotoxicity, linking scaffolding to signal duration.","evidence":"PDZ array screen, reverse overlay, point mutagenesis, reciprocal co-IP, calcium and cell-death assays","pmids":["16891310"],"confidence":"High","gaps":["Physiological cell-death relevance in vivo not established","Interplay with other C-terminal partners not addressed"]},{"year":2007,"claim":"Connected mGluR5 to translational control by showing activation releases FMRP repression of APP mRNA, linking the receptor to local protein synthesis and Abeta production.","evidence":"RNA-protein binding, FMRP-APP mRNA co-IP, DHPG stimulation of synaptoneurosomes, fmr-1 KO comparison, Abeta ELISA","pmids":["17298186"],"confidence":"High","gaps":["Signaling steps from mGluR5 to FMRP release not mapped","In vivo APP/Abeta consequences not quantified"]},{"year":2008,"claim":"Confirmed mGluR5 functions as a bona fide presynaptic autoreceptor facilitating glutamate exocytosis, using genetic deletion to validate concentration-dependent pharmacology.","evidence":"Synaptosome [3H]D-aspartate release with selective antagonists and mGluR5 knockout, subsynaptic fractionation","pmids":["18625255"],"confidence":"High","gaps":["Presynaptic signaling cascade not dissected"]},{"year":2009,"claim":"Discovered that surface versus intracellular mGluR5 pools generate distinct Ca2+ signatures and signaling outputs, with intracellular receptor uniquely driving ERK/Elk-1 and immediate-early genes.","evidence":"Cell-permeable vs impermeable ligand isolation, Ca2+ imaging, phospho-protein and gene-expression assays with kinase inhibitors","pmids":["19840937"],"confidence":"High","gaps":["Source of intracellular ligand not yet identified at this stage","Native tissue confirmation pending"]},{"year":2012,"claim":"Defined the regulatory switch by which PKC phosphorylation at Ser901 displaces calmodulin to favor Siah-1A binding, routing mGluR5 to lysosomal degradation, while a parallel study established constitutive recycling in heterologous cells.","evidence":"Co-IP, S901 mutagenesis, surface biotinylation, and lysosomal/recycling trafficking assays in neurons and HEK293 cells","pmids":["23152621","22995293"],"confidence":"High","gaps":["Conditions selecting recycling versus degradation in vivo not defined","Kinetics of CaM/Siah-1A competition unresolved"]},{"year":2014,"claim":"Localized intracellular mGluR5 to ER/nuclear membranes supplied with glutamate by EAAT3 and showed it selectively mediates LTD but not LTP, providing the missing source for intracellular activation.","evidence":"Cell-permeable/impermeable ligand isolation, radiolabeled agonist uptake, EAAT3 inhibition, Ca2+ imaging, hippocampal slice electrophysiology","pmids":["24672004"],"confidence":"High","gaps":["Mechanism targeting receptor to intracellular membranes unclear","Relative contribution of surface vs intracellular pool to physiological LTD unsettled"]},{"year":2015,"claim":"Established p11/S100A10 as a tail-binding partner promoting mGluR5 surface expression and Ca2+ signaling with opposing behavioral effects in glutamatergic versus GABAergic neurons, and showed biased PAMs can separate Gq signaling from NMDAR modulation in vivo.","evidence":"Co-IP, surface biotinylation, calcium assays, cell-type-specific conditional KO and behavior; biased PAM electrophysiology, signaling, and behavioral models","pmids":["26370144","25937172"],"confidence":"High","gaps":["Structural basis of biased PAM signaling not resolved","How p11 directs receptor trafficking mechanistically unclear"]},{"year":2016,"claim":"Extended intracellular mGluR5 biology to spinal nociception—nuclear-membrane receptor driving sustained Ca2+ and pERK/Arc/c-fos underlies neuropathic pain—and identified cooperative mGluR5-CB1 neuroprotection via MEK/ERK and PI3K/AKT.","evidence":"Subcellular fractionation, Ca2+ imaging, intrathecal cell-permeable/impermeable antagonists, EAAT-3 inhibition, behavior; primary neuron receptor blockade/ablation with kinase inhibitors","pmids":["26837579","27543109"],"confidence":"High","gaps":["Physical mGluR5-CB1 association not demonstrated","Neuroprotection mechanism is correlative for some signaling steps"]},{"year":2017,"claim":"Broadened mGluR5 roles to peripheral TRP channel sensitization via PKCepsilon, immune RANTES/NF-kB signaling in T cells, and epigenetic (Tet1-dependent) transcriptional control of the mGluR5 promoter.","evidence":"In vivo pain behavior with peripheral pharmacology and PKCepsilon assays; Jurkat T-cell agonist/antagonist with NF-kB reporter; intrathecal Tet1 gene transfer with ChIP and bisulfite sequencing","pmids":["28621704","29849049","28718992"],"confidence":"Medium","gaps":["T-cell findings rest on a single cell line","Pain pathways established pharmacologically rather than biochemically","Generality of Tet1-mGluR5 epigenetic regulation beyond pain unknown"]},{"year":2018,"claim":"Linked mGluR5 dysregulation to human disease—pathogenic anti-mGluR5 IgG internalizes surface receptor in encephalitis, and schizophrenia DLPFC shows reduced Gq/Homer/PI3K coupling with hyperphosphorylation and altered scaffold interactions.","evidence":"Patient IgG application to neurons with receptor cluster quantification; co-IP of mGluR5 with Gq/11, Homer, PI3K, GluN, RGS4, Norbin, Preso1, Tamalin and phospho-assays in postmortem tissue","pmids":["29703767","30214040"],"confidence":"Medium","gaps":["Postmortem associations are correlative","Causal direction of phosphorylation changes in disease unresolved","Single methodological approach for antibody pathogenicity"]},{"year":2019,"claim":"Showed Homer1a-enhanced mGluR5 signaling drives mTOR-dependent AMPA receptor potentiation underlying rapid antidepressant action, requiring mGluR5 specifically in CaMK2a excitatory neurons.","evidence":"TAT-Homer1a peptide, conditional mGluR5 KO in CaMK2a neurons, electrophysiology, mTOR phospho-assays, AMPAR surface assays, antidepressant behavior","pmids":["31420117"],"confidence":"High","gaps":["Direct structural Homer1a-mGluR5 engagement during this response not resolved","Link between mTOR and AMPAR trafficking incompletely defined"]},{"year":2020,"claim":"Demonstrated D1-mGluR5 heteromers couple to Gq for synergistic PLC/Ca2+ signaling and are upregulated in dopamine-denervated striatum, driving excessive ERK and dyskinesia.","evidence":"Co-IP, proximity ligation, BRET/FRET, calcium/PLC and ERK assays in rodent Parkinson's models with dyskinesia behavior","pmids":["32039920"],"confidence":"High","gaps":["Stoichiometry and interface of the heteromer not defined","Therapeutic targetability of the heteromer untested"]},{"year":2022,"claim":"Established astrocytic mGluR5 re-emergence after injury as causally driving synaptogenesis and allodynia, and validated mGluR5 silent allosteric modulation to normalize Abeta-driven synaptotoxic signaling and restore synapses in AD models.","evidence":"Astrocyte-specific mGluR5 KO with Ca2+ imaging, synaptogenic-molecule IHC and behavior; oral SAM BMS-984923 with PET occupancy/synaptic density, single-nuclei transcriptomics, and C1Q/engulfment assays in AD mice","pmids":["35319723","35648810"],"confidence":"High","gaps":["Signaling cascade from astrocytic mGluR5 to synaptogenic gene expression not fully mapped","Translation of SAM efficacy to humans untested in these studies"]},{"year":2023,"claim":"Resolved that mGluR5 is dynamically confined to perisynaptic nanodomains by its C-terminal domain, and that forcing synaptic entry acutely boosts synaptic Ca2+, linking nanoscale localization to function.","evidence":"Single-molecule localization microscopy, inducible chemogenetic recruitment, synaptic Ca2+ imaging, and C-terminal mutagenesis","pmids":["36646691"],"confidence":"High","gaps":["Molecular tethers enforcing perisynaptic exclusion not identified","Physiological signals that mobilize the receptor to synapses unknown"]},{"year":2024,"claim":"Provided a stepwise asymmetric allosteric activation model for the dimeric receptor, explaining how agonist-driven ectodomain compaction and PAM-stabilized 7TM interfaces enable G-protein coordination.","evidence":"Markov state models from atomistic MD simulations with experimental signaling validation","pmids":["39209876"],"confidence":"Medium","gaps":["No experimental high-resolution structure of the activation intermediates","Computational mechanism awaits cryo-EM confirmation"]},{"year":null,"claim":"How surface versus ER/nuclear mGluR5 pools are differentially targeted, scaffolded, and recruited to perisynaptic nanodomains—and how these spatial states are coordinated to select signaling and plasticity outcomes—remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["Trafficking determinants directing receptor to intracellular membranes unknown","Molecular tethers enforcing perisynaptic confinement unidentified","How biased pharmacology maps onto subcellular pools in vivo is undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,2,31]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[7,8,24]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[12]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1,6,30]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[15]},{"term_id":"GO:0005635","term_label":"nuclear envelope","supporting_discovery_ids":[15,18]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[6,13,14]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,7,12,26]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[3,11,15,25]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[26,29,23]}],"complexes":["D1-mGluR5 heteromer"],"partners":["NHERF2","S100A10","SIAH1","CALM1","HOMER1","DRD1","ADORA2A","FMR1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P41594","full_name":"Metabotropic glutamate receptor 5","aliases":[],"length_aa":1212,"mass_kda":132.5,"function":"G-protein coupled receptor for glutamate. Ligand binding causes a conformation change that triggers signaling via guanine nucleotide-binding proteins (G proteins) and modulates the activity of down-stream effectors. Signaling activates a phosphatidylinositol-calcium second messenger system and generates a calcium-activated chloride current. Plays an important role in the regulation of synaptic plasticity and the modulation of the neural network activity","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/P41594/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GRM5","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/GRM5","total_profiled":1310},"omim":[{"mim_id":"619373","title":"NEURODEVELOPMENTAL DISORDER WITH INFANTILE EPILEPTIC SPASMS; NEDIES","url":"https://www.omim.org/entry/619373"},{"mim_id":"614453","title":"LEUCINE-RICH REPEAT-CONTAINING PROTEIN 7; LRRC7","url":"https://www.omim.org/entry/614453"},{"mim_id":"608458","title":"NEUROCHONDRIN; NCDN","url":"https://www.omim.org/entry/608458"},{"mim_id":"604800","title":"HOMER SCAFFOLD PROTEIN 3; HOMER3","url":"https://www.omim.org/entry/604800"},{"mim_id":"604799","title":"HOMER SCAFFOLD PROTEIN 2; HOMER2","url":"https://www.omim.org/entry/604799"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"brain","ntpm":13.9}],"url":"https://www.proteinatlas.org/search/GRM5"},"hgnc":{"alias_symbol":["MGLUR5","GPRC1E","mGlu5","PPP1R86"],"prev_symbol":[]},"alphafold":{"accession":"P41594","domains":[{"cath_id":"3.40.50.2300","chopping":"27-123_140-194_411-463","consensus_level":"medium","plddt":91.6533,"start":27,"end":463},{"cath_id":"2.10.50.30","chopping":"520-568","consensus_level":"medium","plddt":89.8255,"start":520,"end":568},{"cath_id":"1.20.1070.10","chopping":"579-835","consensus_level":"high","plddt":87.6461,"start":579,"end":835}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P41594","model_url":"https://alphafold.ebi.ac.uk/files/AF-P41594-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P41594-F1-predicted_aligned_error_v6.png","plddt_mean":71.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GRM5","jax_strain_url":"https://www.jax.org/strain/search?query=GRM5"},"sequence":{"accession":"P41594","fasta_url":"https://rest.uniprot.org/uniprotkb/P41594.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P41594/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P41594"}},"corpus_meta":[{"pmid":"7636025","id":"PMC_7636025","title":"Distribution of metabotropic glutamate receptor mGluR5 immunoreactivity in rat brain.","date":"1995","source":"The Journal of comparative neurology","url":"https://pubmed.ncbi.nlm.nih.gov/7636025","citation_count":598,"is_preprint":false},{"pmid":"11431513","id":"PMC_11431513","title":"Chemical induction of mGluR5- and protein synthesis--dependent long-term depression in hippocampal area CA1.","date":"2001","source":"Journal of neurophysiology","url":"https://pubmed.ncbi.nlm.nih.gov/11431513","citation_count":323,"is_preprint":false},{"pmid":"17298186","id":"PMC_17298186","title":"FMRP mediates mGluR5-dependent translation of amyloid precursor protein.","date":"2007","source":"PLoS biology","url":"https://pubmed.ncbi.nlm.nih.gov/17298186","citation_count":243,"is_preprint":false},{"pmid":"18202092","id":"PMC_18202092","title":"Role for metabotropic glutamate receptor 5 (mGluR5) in the pathogenesis of fragile X syndrome.","date":"2008","source":"The Journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/18202092","citation_count":217,"is_preprint":false},{"pmid":"11077066","id":"PMC_11077066","title":"mGlu5 receptors and nociceptive function II. mGlu5 receptors functionally expressed on peripheral sensory neurones mediate inflammatory hyperalgesia.","date":"2001","source":"Neuropharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/11077066","citation_count":190,"is_preprint":false},{"pmid":"19295507","id":"PMC_19295507","title":"mGluR5 positive allosteric modulators facilitate both hippocampal LTP and LTD and enhance spatial learning.","date":"2009","source":"Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/19295507","citation_count":187,"is_preprint":false},{"pmid":"7782501","id":"PMC_7782501","title":"Differential expression of mGluR5 metabotropic glutamate receptor mRNA by rat striatal neurons.","date":"1995","source":"The Journal of comparative neurology","url":"https://pubmed.ncbi.nlm.nih.gov/7782501","citation_count":167,"is_preprint":false},{"pmid":"11245668","id":"PMC_11245668","title":"Differential subcellular localization of mGluR1a and mGluR5 in the rat and monkey Substantia nigra.","date":"2001","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/11245668","citation_count":146,"is_preprint":false},{"pmid":"22373400","id":"PMC_22373400","title":"Delayed mGluR5 activation limits neuroinflammation and neurodegeneration after traumatic brain injury.","date":"2012","source":"Journal of neuroinflammation","url":"https://pubmed.ncbi.nlm.nih.gov/22373400","citation_count":143,"is_preprint":false},{"pmid":"29703767","id":"PMC_29703767","title":"Encephalitis with mGluR5 antibodies: Symptoms and antibody effects.","date":"2018","source":"Neurology","url":"https://pubmed.ncbi.nlm.nih.gov/29703767","citation_count":140,"is_preprint":false},{"pmid":"21482951","id":"PMC_21482951","title":"Autism, Alzheimer disease, and fragile X: APP, FMRP, and mGluR5 are molecular links.","date":"2011","source":"Neurology","url":"https://pubmed.ncbi.nlm.nih.gov/21482951","citation_count":120,"is_preprint":false},{"pmid":"19840937","id":"PMC_19840937","title":"Intracellular metabotropic glutamate receptor 5 (mGluR5) activates signaling cascades distinct from cell surface counterparts.","date":"2009","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/19840937","citation_count":118,"is_preprint":false},{"pmid":"8576426","id":"PMC_8576426","title":"Metabotropic glutamate receptor mGluR5 subcellular distribution and developmental expression in hypothalamus.","date":"1995","source":"The Journal of comparative neurology","url":"https://pubmed.ncbi.nlm.nih.gov/8576426","citation_count":113,"is_preprint":false},{"pmid":"12538871","id":"PMC_12538871","title":"Metabotropic mGlu5 receptors regulate adenosine A2A receptor signaling.","date":"2003","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/12538871","citation_count":111,"is_preprint":false},{"pmid":"25937172","id":"PMC_25937172","title":"Biased mGlu5-Positive Allosteric Modulators Provide In Vivo Efficacy without Potentiating mGlu5 Modulation of NMDAR Currents.","date":"2015","source":"Neuron","url":"https://pubmed.ncbi.nlm.nih.gov/25937172","citation_count":105,"is_preprint":false},{"pmid":"18377703","id":"PMC_18377703","title":"Metabotropic glutamate receptor 5 (mGluR5) regulation of ethanol sedation, dependence and consumption: relationship to acamprosate actions.","date":"2008","source":"The international journal of neuropsychopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/18377703","citation_count":99,"is_preprint":false},{"pmid":"22640631","id":"PMC_22640631","title":"mGlu2/3 and mGlu5 receptors: potential targets for novel antidepressants.","date":"2012","source":"Neuropharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/22640631","citation_count":98,"is_preprint":false},{"pmid":"17353071","id":"PMC_17353071","title":"mGluR5 metabotropic glutamate receptors and dyskinesias in MPTP monkeys.","date":"2007","source":"Neurobiology of aging","url":"https://pubmed.ncbi.nlm.nih.gov/17353071","citation_count":98,"is_preprint":false},{"pmid":"9202306","id":"PMC_9202306","title":"Metabotropic glutamate receptor mGluR5 in astrocytes: pharmacological properties and agonist regulation.","date":"1997","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9202306","citation_count":93,"is_preprint":false},{"pmid":"14624486","id":"PMC_14624486","title":"Distribution of mGluR1alpha and mGluR5 immunolabeling in primate prefrontal cortex.","date":"2003","source":"The Journal of comparative neurology","url":"https://pubmed.ncbi.nlm.nih.gov/14624486","citation_count":92,"is_preprint":false},{"pmid":"12529370","id":"PMC_12529370","title":"The metabotropic glutamate receptor mGluR5 is endocytosed by a clathrin-independent pathway.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12529370","citation_count":90,"is_preprint":false},{"pmid":"13679408","id":"PMC_13679408","title":"Differential roles of mGluR1 and mGluR5 in brief and prolonged nociceptive processing in central amygdala neurons.","date":"2003","source":"Journal of neurophysiology","url":"https://pubmed.ncbi.nlm.nih.gov/13679408","citation_count":90,"is_preprint":false},{"pmid":"29079293","id":"PMC_29079293","title":"Functional partnership between mGlu3 and mGlu5 metabotropic glutamate receptors in the central nervous system.","date":"2017","source":"Neuropharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/29079293","citation_count":89,"is_preprint":false},{"pmid":"24672004","id":"PMC_24672004","title":"Intracellular mGluR5 can mediate synaptic plasticity in the hippocampus.","date":"2014","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/24672004","citation_count":86,"is_preprint":false},{"pmid":"25847307","id":"PMC_25847307","title":"Astrocytic mGluR5 and the tripartite synapse.","date":"2015","source":"Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/25847307","citation_count":82,"is_preprint":false},{"pmid":"24232444","id":"PMC_24232444","title":"Fragile X syndrome: a preclinical review on metabotropic glutamate receptor 5 (mGluR5) antagonists and drug development.","date":"2014","source":"Psychopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/24232444","citation_count":78,"is_preprint":false},{"pmid":"35648810","id":"PMC_35648810","title":"Reversal of synapse loss in Alzheimer mouse models by targeting mGluR5 to prevent synaptic tagging by C1Q.","date":"2022","source":"Science translational medicine","url":"https://pubmed.ncbi.nlm.nih.gov/35648810","citation_count":77,"is_preprint":false},{"pmid":"26837579","id":"PMC_26837579","title":"Intracellular mGluR5 plays a critical role in neuropathic pain.","date":"2016","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/26837579","citation_count":76,"is_preprint":false},{"pmid":"22340009","id":"PMC_22340009","title":"Role of mGluR5 neurotransmission in reinstated cocaine-seeking.","date":"2012","source":"Addiction biology","url":"https://pubmed.ncbi.nlm.nih.gov/22340009","citation_count":76,"is_preprint":false},{"pmid":"21896768","id":"PMC_21896768","title":"Expression of the metabotropic glutamate receptor 5 (mGluR5) induces melanoma in transgenic mice.","date":"2011","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/21896768","citation_count":75,"is_preprint":false},{"pmid":"26106290","id":"PMC_26106290","title":"Therapeutic potential of mGluR5 targeting in Alzheimer's disease.","date":"2015","source":"Frontiers in neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/26106290","citation_count":74,"is_preprint":false},{"pmid":"24672001","id":"PMC_24672001","title":"Changes in mGlu5 receptor-dependent synaptic plasticity and coupling to homer proteins in the hippocampus of Ube3A hemizygous mice modeling angelman syndrome.","date":"2014","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/24672001","citation_count":72,"is_preprint":false},{"pmid":"29413525","id":"PMC_29413525","title":"Synaptotoxic Signaling by Amyloid Beta Oligomers in Alzheimer's Disease Through Prion Protein and mGluR5.","date":"2017","source":"Advances in pharmacology (San Diego, Calif.)","url":"https://pubmed.ncbi.nlm.nih.gov/29413525","citation_count":67,"is_preprint":false},{"pmid":"31420117","id":"PMC_31420117","title":"Enhanced mGlu5 Signaling in Excitatory Neurons Promotes Rapid Antidepressant Effects via AMPA Receptor Activation.","date":"2019","source":"Neuron","url":"https://pubmed.ncbi.nlm.nih.gov/31420117","citation_count":66,"is_preprint":false},{"pmid":"23710649","id":"PMC_23710649","title":"The role of ventral and dorsal striatum mGluR5 in relapse to cocaine-seeking and extinction learning.","date":"2013","source":"Addiction biology","url":"https://pubmed.ncbi.nlm.nih.gov/23710649","citation_count":66,"is_preprint":false},{"pmid":"15334174","id":"PMC_15334174","title":"mGlu5 receptor antagonists: a novel class of anxiolytics?","date":"2004","source":"Drug news & perspectives","url":"https://pubmed.ncbi.nlm.nih.gov/15334174","citation_count":65,"is_preprint":false},{"pmid":"26370144","id":"PMC_26370144","title":"Alteration by p11 of mGluR5 localization regulates depression-like behaviors.","date":"2015","source":"Molecular psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/26370144","citation_count":65,"is_preprint":false},{"pmid":"25409593","id":"PMC_25409593","title":"Homer1/mGluR5 activity moderates vulnerability to chronic social stress.","date":"2015","source":"Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/25409593","citation_count":61,"is_preprint":false},{"pmid":"18729017","id":"PMC_18729017","title":"mGluR5 antagonists: discovery, characterization and drug development.","date":"2008","source":"Current opinion in drug discovery & development","url":"https://pubmed.ncbi.nlm.nih.gov/18729017","citation_count":59,"is_preprint":false},{"pmid":"23339457","id":"PMC_23339457","title":"mGlu5 negative allosteric modulators: a patent review (2010-2012).","date":"2013","source":"Expert opinion on therapeutic patents","url":"https://pubmed.ncbi.nlm.nih.gov/23339457","citation_count":54,"is_preprint":false},{"pmid":"30961637","id":"PMC_30961637","title":"Modulation of mTOR and CREB pathways following mGluR5 blockade contribute to improved Huntington's pathology in zQ175 mice.","date":"2019","source":"Molecular brain","url":"https://pubmed.ncbi.nlm.nih.gov/30961637","citation_count":54,"is_preprint":false},{"pmid":"35319723","id":"PMC_35319723","title":"Transient astrocytic mGluR5 expression drives synaptic plasticity and subsequent chronic pain in mice.","date":"2022","source":"The Journal of experimental medicine","url":"https://pubmed.ncbi.nlm.nih.gov/35319723","citation_count":52,"is_preprint":false},{"pmid":"17428452","id":"PMC_17428452","title":"Cellular localization of mGluR3 and mGluR5 mRNAs in normal and injured rat brain.","date":"2007","source":"Brain research","url":"https://pubmed.ncbi.nlm.nih.gov/17428452","citation_count":52,"is_preprint":false},{"pmid":"31954399","id":"PMC_31954399","title":"PET imaging of mGluR5 in Alzheimer's disease.","date":"2020","source":"Alzheimer's research & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/31954399","citation_count":51,"is_preprint":false},{"pmid":"27563063","id":"PMC_27563063","title":"Regulation of Amyloid β Oligomer Binding to Neurons and Neurotoxicity by the Prion Protein-mGluR5 Complex.","date":"2016","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/27563063","citation_count":51,"is_preprint":false},{"pmid":"16891310","id":"PMC_16891310","title":"The PDZ scaffold NHERF-2 interacts with mGluR5 and regulates receptor activity.","date":"2006","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16891310","citation_count":50,"is_preprint":false},{"pmid":"30504280","id":"PMC_30504280","title":"Conditional Knock-out of mGluR5 from Astrocytes during Epilepsy Development Impairs High-Frequency Glutamate Uptake.","date":"2018","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/30504280","citation_count":50,"is_preprint":false},{"pmid":"27315032","id":"PMC_27315032","title":"Direct current stimulation induces mGluR5-dependent neocortical plasticity.","date":"2016","source":"Annals of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/27315032","citation_count":49,"is_preprint":false},{"pmid":"32039920","id":"PMC_32039920","title":"D1-mGlu5 heteromers mediate noncanonical dopamine signaling in Parkinson's disease.","date":"2020","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/32039920","citation_count":46,"is_preprint":false},{"pmid":"25326002","id":"PMC_25326002","title":"Location-dependent signaling of the group 1 metabotropic glutamate receptor mGlu5.","date":"2014","source":"Molecular pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/25326002","citation_count":45,"is_preprint":false},{"pmid":"18625255","id":"PMC_18625255","title":"Presynaptic mGlu1 and mGlu5 autoreceptors facilitate glutamate exocytosis from mouse cortical nerve endings.","date":"2008","source":"Neuropharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/18625255","citation_count":44,"is_preprint":false},{"pmid":"21093598","id":"PMC_21093598","title":"Functional interaction of mGlu5 and NMDA receptors in aversive learning in rats.","date":"2010","source":"Neurobiology of learning and memory","url":"https://pubmed.ncbi.nlm.nih.gov/21093598","citation_count":43,"is_preprint":false},{"pmid":"28621704","id":"PMC_28621704","title":"Sensitization of TRPV1 and TRPA1 via peripheral mGluR5 signaling contributes to thermal and mechanical hypersensitivity.","date":"2017","source":"Pain","url":"https://pubmed.ncbi.nlm.nih.gov/28621704","citation_count":42,"is_preprint":false},{"pmid":"28718992","id":"PMC_28718992","title":"Melatonin impedes Tet1-dependent mGluR5 promoter demethylation to relieve pain.","date":"2017","source":"Journal of pineal research","url":"https://pubmed.ncbi.nlm.nih.gov/28718992","citation_count":42,"is_preprint":false},{"pmid":"21152045","id":"PMC_21152045","title":"Operant sensation seeking requires metabotropic glutamate receptor 5 (mGluR5).","date":"2010","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/21152045","citation_count":42,"is_preprint":false},{"pmid":"30214040","id":"PMC_30214040","title":"mGluR5 hypofunction is integral to glutamatergic dysregulation in schizophrenia.","date":"2018","source":"Molecular psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/30214040","citation_count":41,"is_preprint":false},{"pmid":"15210575","id":"PMC_15210575","title":"Interactions between NMDA receptors and mGlu5 receptors expressed in HEK293 cells.","date":"2004","source":"British journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/15210575","citation_count":41,"is_preprint":false},{"pmid":"27127992","id":"PMC_27127992","title":"Functional role of striatal A2A, D2, and mGlu5 receptor interactions in regulating striatopallidal GABA neuronal transmission.","date":"2016","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/27127992","citation_count":41,"is_preprint":false},{"pmid":"26349010","id":"PMC_26349010","title":"Shifting towards a model of mGluR5 dysregulation in schizophrenia: Consequences for future schizophrenia treatment.","date":"2015","source":"Neuropharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/26349010","citation_count":40,"is_preprint":false},{"pmid":"31085640","id":"PMC_31085640","title":"In vivo evidence for dysregulation of mGluR5 as a biomarker of suicidal ideation.","date":"2019","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/31085640","citation_count":40,"is_preprint":false},{"pmid":"25704074","id":"PMC_25704074","title":"Convergent evidence for mGluR5 in synaptic and neuroinflammatory pathways implicated in ASD.","date":"2015","source":"Neuroscience and biobehavioral reviews","url":"https://pubmed.ncbi.nlm.nih.gov/25704074","citation_count":38,"is_preprint":false},{"pmid":"25778620","id":"PMC_25778620","title":"Alterations of mGluR5 and its endogenous regulators Norbin, Tamalin and Preso1 in schizophrenia: towards a model of mGluR5 dysregulation.","date":"2015","source":"Acta neuropathologica","url":"https://pubmed.ncbi.nlm.nih.gov/25778620","citation_count":37,"is_preprint":false},{"pmid":"19892412","id":"PMC_19892412","title":"The promiscuous mGlu5 receptor--a range of partners for therapeutic possibilities?","date":"2009","source":"Trends in pharmacological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/19892412","citation_count":36,"is_preprint":false},{"pmid":"23152621","id":"PMC_23152621","title":"PKC phosphorylation regulates mGluR5 trafficking by enhancing binding of Siah-1A.","date":"2012","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/23152621","citation_count":34,"is_preprint":false},{"pmid":"23940572","id":"PMC_23940572","title":"mGluR5 ablation in cortical glutamatergic neurons increases novelty-induced locomotion.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23940572","citation_count":33,"is_preprint":false},{"pmid":"22995293","id":"PMC_22995293","title":"Constitutive internalization and recycling of metabotropic glutamate receptor 5 (mGluR5).","date":"2012","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/22995293","citation_count":33,"is_preprint":false},{"pmid":"36646691","id":"PMC_36646691","title":"mGluR5 is transiently confined in perisynaptic nanodomains to shape synaptic function.","date":"2023","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/36646691","citation_count":32,"is_preprint":false},{"pmid":"34658956","id":"PMC_34658956","title":"mGluR5 Negative Modulators for Fragile X: Treatment Resistance and Persistence.","date":"2021","source":"Frontiers in psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/34658956","citation_count":32,"is_preprint":false},{"pmid":"11566212","id":"PMC_11566212","title":"Gene targeting reveals a role for the glutamate receptors mGluR5 and GluR2 in learning and memory.","date":"2001","source":"Physiology & behavior","url":"https://pubmed.ncbi.nlm.nih.gov/11566212","citation_count":32,"is_preprint":false},{"pmid":"31747354","id":"PMC_31747354","title":"Alterations in sleep, sleep spindle, and EEG power in mGluR5 knockout mice.","date":"2019","source":"Journal of neurophysiology","url":"https://pubmed.ncbi.nlm.nih.gov/31747354","citation_count":32,"is_preprint":false},{"pmid":"28067079","id":"PMC_28067079","title":"mGlu5 negative allosteric modulators: a patent review (2013 - 2016).","date":"2017","source":"Expert opinion on therapeutic patents","url":"https://pubmed.ncbi.nlm.nih.gov/28067079","citation_count":31,"is_preprint":false},{"pmid":"15494040","id":"PMC_15494040","title":"Allosteric modulators of metabotropic glutamate receptors: lessons learnt from mGlu1, mGlu2 and mGlu5 potentiators and antagonists.","date":"2004","source":"Biochemical Society transactions","url":"https://pubmed.ncbi.nlm.nih.gov/15494040","citation_count":31,"is_preprint":false},{"pmid":"28405888","id":"PMC_28405888","title":"Effects of common GRM5 genetic variants on cognition, hippocampal volume and mGluR5 protein levels in schizophrenia.","date":"2018","source":"Brain imaging and behavior","url":"https://pubmed.ncbi.nlm.nih.gov/28405888","citation_count":30,"is_preprint":false},{"pmid":"22449017","id":"PMC_22449017","title":"Metabotropic glutamate receptor 5 (mGluR5) regulates bladder nociception.","date":"2012","source":"Molecular pain","url":"https://pubmed.ncbi.nlm.nih.gov/22449017","citation_count":29,"is_preprint":false},{"pmid":"26187757","id":"PMC_26187757","title":"Homer 1a and mGluR5 phosphorylation in reward-sensitive metaplasticity: A hypothesis of neuronal selection and bidirectional synaptic plasticity.","date":"2015","source":"Brain research","url":"https://pubmed.ncbi.nlm.nih.gov/26187757","citation_count":28,"is_preprint":false},{"pmid":"22193724","id":"PMC_22193724","title":"RGS4 overexpression in the rat dorsal striatum modulates mGluR5- and amphetamine-mediated behavior and signaling.","date":"2011","source":"Psychopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/22193724","citation_count":28,"is_preprint":false},{"pmid":"39209876","id":"PMC_39209876","title":"Delineating the stepwise millisecond allosteric activation mechanism of the class C GPCR dimer mGlu5.","date":"2024","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/39209876","citation_count":28,"is_preprint":false},{"pmid":"31570178","id":"PMC_31570178","title":"Age dependency of mGluR5 availability in 5xFAD mice measured by PET.","date":"2019","source":"Neurobiology of aging","url":"https://pubmed.ncbi.nlm.nih.gov/31570178","citation_count":27,"is_preprint":false},{"pmid":"19410084","id":"PMC_19410084","title":"Expression of metabotropic glutamate receptor mGluR5 in human dental pulp.","date":"2009","source":"Journal of endodontics","url":"https://pubmed.ncbi.nlm.nih.gov/19410084","citation_count":27,"is_preprint":false},{"pmid":"21153406","id":"PMC_21153406","title":"Interactive effects of mGlu5 and 5-HT2A receptors on locomotor activity in mice.","date":"2010","source":"Psychopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/21153406","citation_count":27,"is_preprint":false},{"pmid":"28231291","id":"PMC_28231291","title":"Osteosarcoma cell proliferation and survival requires mGluR5 receptor activity and is blocked by Riluzole.","date":"2017","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/28231291","citation_count":26,"is_preprint":false},{"pmid":"26861145","id":"PMC_26861145","title":"Emotional Impairment and Persistent Upregulation of mGlu5 Receptor following Morphine Abstinence: Implications of an mGlu5-MOPr Interaction.","date":"2016","source":"The international journal of neuropsychopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/26861145","citation_count":26,"is_preprint":false},{"pmid":"22591751","id":"PMC_22591751","title":"Pilocarpine-induced status epilepticus increases Homer1a and changes mGluR5 expression.","date":"2012","source":"Epilepsy research","url":"https://pubmed.ncbi.nlm.nih.gov/22591751","citation_count":26,"is_preprint":false},{"pmid":"25863284","id":"PMC_25863284","title":"mGlu₅-GABAB interplay in animal models of positive, negative and cognitive symptoms of schizophrenia.","date":"2015","source":"Neurochemistry international","url":"https://pubmed.ncbi.nlm.nih.gov/25863284","citation_count":26,"is_preprint":false},{"pmid":"20583985","id":"PMC_20583985","title":"Radioligands for the PET imaging of metabotropic glutamate receptor subtype 5 (mGluR5).","date":"2010","source":"Current topics in medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/20583985","citation_count":26,"is_preprint":false},{"pmid":"29849049","id":"PMC_29849049","title":"mGluR5 mediates post-radiotherapy fatigue development in cancer patients.","date":"2018","source":"Translational psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/29849049","citation_count":25,"is_preprint":false},{"pmid":"15717212","id":"PMC_15717212","title":"Blockade of the mGlu5 receptor decreases basal and stress-induced cortical norepinephrine in rodents.","date":"2005","source":"Psychopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/15717212","citation_count":25,"is_preprint":false},{"pmid":"23711322","id":"PMC_23711322","title":"Cellular distribution of AMPA receptor subunits and mGlu5 following acute and repeated administration of morphine or methamphetamine.","date":"2013","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/23711322","citation_count":25,"is_preprint":false},{"pmid":"31063776","id":"PMC_31063776","title":"Pathophysiological clues to therapeutic applications of glutamate mGlu5 receptor antagonists in levodopa-induced dyskinesia.","date":"2019","source":"European journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/31063776","citation_count":24,"is_preprint":false},{"pmid":"31008528","id":"PMC_31008528","title":"Ultrastructural localization of cannabinoid CB1 and mGluR5 receptors in the prefrontal cortex and amygdala.","date":"2019","source":"The Journal of comparative neurology","url":"https://pubmed.ncbi.nlm.nih.gov/31008528","citation_count":24,"is_preprint":false},{"pmid":"24576814","id":"PMC_24576814","title":"The mGlu5 receptor regulates extinction of cocaine-driven behaviours.","date":"2014","source":"Drug and alcohol dependence","url":"https://pubmed.ncbi.nlm.nih.gov/24576814","citation_count":24,"is_preprint":false},{"pmid":"31744389","id":"PMC_31744389","title":"Measuring the effects of ketamine on mGluR5 using [18F]FPEB and PET.","date":"2019","source":"Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/31744389","citation_count":24,"is_preprint":false},{"pmid":"16040064","id":"PMC_16040064","title":"Grm5 expression is not required for the oncogenic role of Grm1 in melanocytes.","date":"2005","source":"Neuropharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/16040064","citation_count":23,"is_preprint":false},{"pmid":"24670218","id":"PMC_24670218","title":"Nanoscopic spine localization of Norbin, an mGluR5 accessory protein.","date":"2014","source":"BMC neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/24670218","citation_count":23,"is_preprint":false},{"pmid":"24552998","id":"PMC_24552998","title":"Is the mGlu5 receptor a possible target for new antidepressant drugs?","date":"2013","source":"Pharmacological reports : PR","url":"https://pubmed.ncbi.nlm.nih.gov/24552998","citation_count":22,"is_preprint":false},{"pmid":"33444640","id":"PMC_33444640","title":"mGlu5 function in the nucleus accumbens core during the incubation of methamphetamine craving.","date":"2021","source":"Neuropharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/33444640","citation_count":22,"is_preprint":false},{"pmid":"34029630","id":"PMC_34029630","title":"Genetic disruption of Grm5 causes complex alterations in motor activity, anxiety and social behaviors.","date":"2021","source":"Behavioural brain research","url":"https://pubmed.ncbi.nlm.nih.gov/34029630","citation_count":21,"is_preprint":false},{"pmid":"38217040","id":"PMC_38217040","title":"Metabotropic glutamate receptor 5 (mGluR5) is associated with neurodegeneration and amyloid deposition in Alzheimer's disease: A [18F]PSS232 PET/MRI study.","date":"2024","source":"Alzheimer's research & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/38217040","citation_count":21,"is_preprint":false},{"pmid":"27543109","id":"PMC_27543109","title":"Orchestrated activation of mGluR5 and CB1 promotes neuroprotection.","date":"2016","source":"Molecular brain","url":"https://pubmed.ncbi.nlm.nih.gov/27543109","citation_count":21,"is_preprint":false},{"pmid":"32958647","id":"PMC_32958647","title":"Astroglial FMRP deficiency cell-autonomously up-regulates miR-128 and disrupts developmental astroglial mGluR5 signaling.","date":"2020","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/32958647","citation_count":21,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":51968,"output_tokens":9853,"usd":0.151849,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":20123,"output_tokens":7404,"usd":0.142857,"stage2_stop_reason":"end_turn"},"total_usd":0.294706,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1995,\n      \"finding\": \"mGluR5 is a G-protein coupled receptor that couples to phosphatidylinositol hydrolysis and calcium mobilization via inositol triphosphate. Immunoelectron microscopy in rat brain showed it is predominantly localized on postsynaptic dendritic spines and shafts, with some presynaptic axon terminal labeling, suggesting a presynaptic autoreceptor role in addition to postsynaptic function.\",\n      \"method\": \"Western blot (receptor-specific antibody), immunocytochemistry, electron microscopy, transfection of nonneuronal cells\",\n      \"journal\": \"The Journal of comparative neurology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct subcellular localization by electron microscopy with receptor-specific antibody, replicated across hippocampus and cortex, confirmed by Western blot in multiple brain regions\",\n      \"pmids\": [\"7636025\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"mGluR5 protein expression is dramatically higher during early hypothalamic development compared to adults (sixfold decrease in hypothalamus, threefold in cortex with maturation). Ultrastructurally, mGluR5 localizes to the cytoplasmic face of the plasma membrane on hypothalamic dendrites, dendritic spines, and perikarya, and is also expressed on astrocyte processes surrounding asymmetric synapses.\",\n      \"method\": \"Western blot, Northern blot, immunocytochemistry, electron microscopy\",\n      \"journal\": \"The Journal of comparative neurology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (Western, Northern, immunoEM) documenting developmental regulation and subcellular localization, single lab but comprehensive\",\n      \"pmids\": [\"8576426\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"In native astrocytes expressing mGluR5 without mGluR1 interference, mGluR5 activation induces phosphoinositide (PI) hydrolysis without stimulating cAMP formation. Prolonged agonist exposure causes two-phase desensitization: an early phase (completed by 1 h) independent of receptor internalization or PKC/PKA phosphorylation, and a late phase (by 24 h) associated with receptor down-regulation. Resensitization after prolonged exposure requires new protein synthesis.\",\n      \"method\": \"Pharmacological assays (PI hydrolysis, cAMP measurement), phorbol ester treatment, receptor down-regulation assays in cultured astrocytes\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — native cell expression system with multiple orthogonal pharmacological approaches dissecting desensitization mechanisms, single lab\",\n      \"pmids\": [\"9202306\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Pharmacological activation of mGluR5 (but not mGluR1) by DHPG is sufficient to induce long-term depression (LTD) in hippocampal CA1. This mGluR5-LTD is saturable, mechanistically distinct from NMDAR-dependent LTD, and shares an expression mechanism with protein synthesis-dependent LTD induced by synaptic stimulation.\",\n      \"method\": \"Electrophysiology (field recordings in hippocampal slices), selective pharmacological tools (DHPG, mGluR5 antagonists), protein synthesis inhibitors\",\n      \"journal\": \"Journal of neurophysiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean electrophysiological loss-of-function with selective antagonists, replicated across multiple experimental conditions in the same study\",\n      \"pmids\": [\"11431513\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"mGluR5 expressed on peripheral terminals of primary afferent neurons mediates inflammatory hyperalgesia. Intraplantar but not intracerebroventricular or intrathecal injection of the selective mGluR5 antagonist MPEP reduces Freund's complete adjuvant-induced hind paw hyperalgesia. Group I mGluR agonist-induced mechanical hyperalgesia was blocked by MPEP but not by the mGluR1 antagonist 4-CPG.\",\n      \"method\": \"In vivo pharmacology (intraplantar, i.c.v., intrathecal microinjection), behavioral pain testing, in vivo electrophysiology (dorsal horn WDR neuron recordings), double-label immunohistochemistry (mGluR5 + βIII-tubulin; mGluR5 + TRPV1)\",\n      \"journal\": \"Neuropharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal in vivo approaches (behavioral, electrophysiological, anatomical) with receptor-specific pharmacology in a single study\",\n      \"pmids\": [\"11077066\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"mGluR5 is required for spatial learning and context-dependent fear conditioning. mGluR5 knockout mice are deficient in Morris water maze performance and contextual fear conditioning, establishing a pathway linking mGluR5 → PKC → Src → enhanced NMDAR open probability → LTP of NMDAR, necessary for spatial memory.\",\n      \"method\": \"Genetic knockout (mGluR5 null mice), Morris water maze, fear conditioning, hippocampal slice electrophysiology (LTP recording)\",\n      \"journal\": \"Physiology & behavior\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — genetic KO with defined behavioral readout and proposed mechanistic pathway, but mechanistic details (PKC/Src pathway) cited as from other work rather than directly demonstrated in this paper\",\n      \"pmids\": [\"11566212\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"mGluR5 endocytosis occurs via a clathrin-independent, dynamin-2-dependent pathway. mGluR5a and mGluR5b internalize constitutively in COS-7 cells and neurons (axons and dendrites) even without ligand activation or in the presence of an inverse agonist. Dominant-negative Eps15 (clathrin pathway blocker) does not prevent mGluR5 endocytosis, but dynamin-2 is required.\",\n      \"method\": \"Transfection in COS-7 cells and hippocampal neurons, immunocytochemistry, quantitative image analysis, biochemical endocytosis assay, dominant-negative Eps15 constructs\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — dominant-negative genetic approach combined with biochemical and imaging assays, multiple orthogonal methods in a single lab study\",\n      \"pmids\": [\"12529370\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"mGluR5 potentiates adenosine A2A receptor-mediated DARPP-32 phosphorylation at Thr-34 in neostriatal neurons by stimulating A2A receptor-coupled cAMP formation in an ERK-dependent manner. The action of mGluR5 requires A2A receptor activation by endogenous adenosine. Coactivation of mGluR5 and A2A receptors synergistically increases DARPP-32 phosphorylation. The effect is not dependent on PLC activation.\",\n      \"method\": \"Neostriatal slice pharmacology, DARPP-32 phosphorylation assays, selective receptor antagonists, kinase inhibitors (ERK, PLC, p38, CK1, Cdk5)\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple receptor antagonists and kinase inhibitors used to dissect signaling pathway in native tissue, mechanistic specificity established with multiple pharmacological tools\",\n      \"pmids\": [\"12538871\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"mGluR5 expressed in HEK293 cells can both inhibit and potentiate NMDA receptor responses through distinct mechanisms. The inhibitory influence depends on Ca2+ release from stores (thapsigargin-sensitive) and PKC activation. Removal of these processes reveals a tonic mGluR5- and protein tyrosine kinase (PTK)-dependent potentiation of NMDA receptors. Protein tyrosine phosphatase (PTP) inhibitors occlude DHPG-induced NMDAR potentiation.\",\n      \"method\": \"Ca2+ imaging in HEK293 cells co-transfected with NR1a, NR2A, and mGlu5a; pharmacological dissection with thapsigargin, staurosporine, PTK inhibitors (genistein, PP2), PTP inhibitors (orthovanadate, PAO)\",\n      \"journal\": \"British journal of pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Weak — reconstituted receptor co-expression system with multiple pharmacological tools, but single lab in heterologous cells only\",\n      \"pmids\": [\"15210575\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The PDZ scaffold NHERF-2 directly and selectively interacts with mGluR5 (not mGluR1a) via the second PDZ domain of NHERF-2 binding to the C-terminus of mGluR5. A single point mutation in mGluR5-CT completely disrupts this interaction. NHERF-2 co-immunoprecipitates with full-length mGluR5 in cells, and co-expression of NHERF-2 prolongs mGluR5-mediated calcium mobilization and potentiates mGluR5-mediated cell death.\",\n      \"method\": \"PDZ domain proteomic array screening, reverse overlay assay, point mutagenesis, co-immunoprecipitation, confocal microscopy, functional calcium assays, cell death assays, immunohistochemistry in mouse brain\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — PDZ array + mutagenesis + reciprocal co-IP + functional assay, multiple orthogonal methods in one study\",\n      \"pmids\": [\"16891310\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"FMRP binds to the coding region of APP mRNA at a guanine-rich, G-quartet-like sequence. Stimulation of cortical synaptoneurosomes or neurons with the mGluR5 agonist DHPG increases APP translation in wild-type but not fmr-1 knockout samples. APP mRNA co-immunoprecipitates with FMRP in resting synaptoneurosomes, but this interaction is lost shortly after DHPG treatment, indicating that mGluR5 activation releases FMRP repression of APP mRNA translation.\",\n      \"method\": \"RNA-protein binding assays, co-immunoprecipitation (FMRP-APP mRNA), DHPG stimulation of synaptoneurosomes and primary neurons, metabolic labeling, fmr-1 KO mouse comparison, ELISA (Aβ levels)\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP, KO comparison, and direct translation assay with multiple orthogonal approaches in one study\",\n      \"pmids\": [\"17298186\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"mGluR5 functions as a presynaptic autoreceptor on glutamatergic cortical nerve terminals, facilitating evoked glutamate exocytosis. Low concentrations of DHPG (0.3 μM) potentiate depolarization-evoked [3H]D-aspartate release via mGluR5 (blocked by MPEP, not CPCCOEt), whereas high concentrations (50 μM) act via mGluR1. This mGluR5 presynaptic role was confirmed by absence of potentiation in mGluR5 knockout synaptosome preparations.\",\n      \"method\": \"Synaptosome [3H]D-aspartate release assay, selective pharmacological antagonists (MPEP, CPCCOEt), mGluR5 knockout mice, Western blot of subsynaptic fractions, immunocytochemistry\",\n      \"journal\": \"Neuropharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO validation combined with selective pharmacology and biochemical fractionation, multiple orthogonal approaches\",\n      \"pmids\": [\"18625255\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Activation of cell surface versus intracellular mGluR5 produces distinct Ca2+ signatures and unique downstream signaling. Both pools activate JNK, CaMK, and CREB phosphorylation; however, only intracellular mGluR5 activates ERK1/2 and Elk-1 phosphorylation, resulting in upregulation of c-fos and egr1 but not c-jun. CaMK kinase mediates CREB phosphorylation downstream of mGluR5, while CaMKII is upstream of intracellular mGluR5-mediated Elk-1 phosphorylation. Intracellular mGluR5 is activated by glutamate transported into the cell.\",\n      \"method\": \"Pharmacological isolation of surface vs. intracellular receptor pools (cell-impermeable vs. cell-permeable ligands), Ca2+ imaging, phospho-protein assays (JNK, CaMK, CREB, ERK1/2, Elk-1), kinase inhibitors, gene expression analysis, genetic approaches\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological and genetic dissection of distinct signaling pools with multiple orthogonal signaling readouts in a single study\",\n      \"pmids\": [\"19840937\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PKC phosphorylation of mGluR5 at Ser901 enhances binding of the E3 ligase Siah-1A by displacing calmodulin (CaM). Siah-1A binding to mGluR5 decreases receptor surface expression and increases lysosomal degradation via endosomal trafficking. CaM and Siah-1A compete for mGluR5 binding in a phosphorylation-dependent manner in rat hippocampal neurons.\",\n      \"method\": \"Co-immunoprecipitation in hippocampal neurons, site-directed mutagenesis (S901 phosphorylation site), surface biotinylation assay, lysosomal degradation assays\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis of phosphorylation site, co-IP in neurons, trafficking assays with multiple orthogonal methods, single lab\",\n      \"pmids\": [\"23152621\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"mGluR5 constitutively internalizes in HEK293 cells in the absence of ligand. Following endocytosis, the receptor enters the recycling compartment and returns to the cell surface; no lysosomal localization is observed after constitutive internalization.\",\n      \"method\": \"Surface biotinylation assays, antibody feeding internalization assay, confocal microscopy with organelle markers in HEK293 cells\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Weak — biochemical and imaging assays in heterologous cells, single lab, limited mechanistic depth\",\n      \"pmids\": [\"22995293\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Intracellular mGluR5 is present on the endoplasmic reticulum and nucleus of hippocampal CA1 neurons, where it colocalizes with the glutamate transporter EAAT3. Inhibition of EAAT3 prevented accumulation of radiolabeled agonist at intracellular mGluR5. Both intracellular and cell surface mGluR5 induced oscillatory Ca2+ responses, but only intracellular mGluR5 triggered sustained high-amplitude Ca2+ rises in dendrites. Activation of intracellular mGluR5 alone mediated both electrically- and chemically-induced LTD but not LTP in acute hippocampal slices.\",\n      \"method\": \"Pharmacological isolation of intracellular vs. surface mGluR5 (cell-permeable vs. impermeable ligands), Ca2+ imaging, radiolabeled agonist uptake assays, EAAT3 inhibition, acute hippocampal slice electrophysiology\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (Ca2+ imaging, electrophysiology, transporter inhibition) to demonstrate intracellular receptor function, single lab\",\n      \"pmids\": [\"24672004\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"p11 (S100A10) directly binds to the cytoplasmic tail of mGluR5. p11 and mGluR5 mutually facilitate their accumulation at the plasma membrane, and p11 increases cell-surface availability of mGluR5. Overexpression of p11 potentiates mGluR5 agonist-induced calcium responses. Knockout of mGluR5 or p11 specifically in glutamatergic neurons causes depression-like behaviors, while knockout in GABAergic neurons causes antidepressant-like behaviors.\",\n      \"method\": \"Co-immunoprecipitation, cell-surface biotinylation, calcium signaling assays, cell-type-specific conditional knockout (glutamatergic vs. GABAergic neurons), behavioral assays\",\n      \"journal\": \"Molecular psychiatry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding (co-IP), surface expression assay, functional signaling validation, and cell-type-specific KO phenotypic readout, multiple orthogonal methods\",\n      \"pmids\": [\"26370144\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Biased mGluR5 PAMs can selectively potentiate mGluR5 coupling to Gαq-mediated signaling without potentiating mGluR5 modulation of NMDAR currents or NMDAR-dependent synaptic plasticity. VU0409551 produced antipsychotic-like and cognition-enhancing activity in animal models despite not potentiating NMDAR function, demonstrating that NMDAR current modulation is not required for in vivo efficacy of mGluR5 PAMs.\",\n      \"method\": \"Electrophysiology (hippocampal slice NMDAR currents), calcium signaling assays (Gαq), behavioral models (psychosis, cognition), selective PAM pharmacology\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (electrophysiology, signaling assays, behavior) using biased pharmacological tool in both in vitro and in vivo systems\",\n      \"pmids\": [\"25937172\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"In spinal dorsal horn neurons, >80% of mGluR5 is intracellular, with ~60% located on nuclear membranes where activation produces sustained Ca2+ responses. Nerve injury increases nuclear mGluR5 expression and receptor-mediated pERK1/2, Arc/Arg3.1, and c-fos. Spinal blockade of intracellular (but not cell surface) mGluR5 reduces neuropathic pain behaviors. Blocking EAAT-3 to reduce intracellular glutamate mimics the effects of intracellular mGluR5 antagonism.\",\n      \"method\": \"Immunofluorescence/confocal microscopy (subcellular fractionation), Ca2+ imaging, intrathecal drug delivery (cell-impermeable vs. permeable mGluR5 antagonists), EAAT-3 inhibition, behavioral pain testing, Western blot (pERK1/2, Arc, c-fos)\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — pharmacological dissection of intracellular vs. surface mGluR5 with multiple orthogonal in vitro and in vivo readouts, linking intracellular GPCR to behavioral outcome\",\n      \"pmids\": [\"26837579\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"mGluR5 (postsynaptic) and CB1 (presynaptic) receptors work cooperatively to promote neuroprotection against glutamate insult. Pharmacological blockade or genetic ablation of either receptor abolishes both CB1- and mGluR5-mediated neuroprotection. The neuroprotective mechanism involves MEK/ERK1/2 and PI3K/AKT signaling pathways, rather than reduced glutamate release or diminished intracellular Ca2+.\",\n      \"method\": \"Primary corticostriatal neuron cultures, pharmacological receptor blockade, genetic ablation, cell death assays, kinase inhibitors, signaling assays (ERK1/2, AKT phosphorylation)\",\n      \"journal\": \"Molecular brain\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — genetic and pharmacological approaches in primary neurons with multiple signaling readouts, single lab study\",\n      \"pmids\": [\"27543109\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"mGluR5 agonist CHPG treatment increases RANTES production and amplifies irradiation-induced NF-κB activation in T lymphocytes, while mGluR5 inhibition with MPEP decreases RANTES after irradiation. mGluR5 receptors cluster following irradiation in T cells.\",\n      \"method\": \"T lymphocyte cell line (Jurkat E6.1), mGluR5 agonist/antagonist treatment, ELISA (RANTES), NF-κB/GFP reporter assay, immunofluorescence (receptor clustering)\",\n      \"journal\": \"Translational psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single cell line, pharmacological approach with reporter assay, single lab\",\n      \"pmids\": [\"29849049\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Peripheral mGluR5 signaling sensitizes TRPV1 and TRPA1 via PKCε phosphorylation to produce thermal and mechanical hypersensitivity. Continuous facial skin injection of mGluR5 agonist (CHPG) or glutamate decreased pain thresholds, which were reversed by mGluR5 antagonist MTEP, TRPA1 antagonist, TRPV1 antagonist, or PKCε translocation inhibitor applied peripherally. PKCε phosphorylation in trigeminal ganglion was enhanced by glutamate treatment.\",\n      \"method\": \"In vivo pain behavioral assays, intraplantar pharmacological injections, Western blot (PKCε phosphorylation), immunohistochemistry (co-expression of mGluR5, TRPV1, TRPA1, PKCε)\",\n      \"journal\": \"Pain\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — multiple pharmacological tools and in vivo behavioral assays, but mechanistic pathway established pharmacologically not biochemically, single lab\",\n      \"pmids\": [\"28621704\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Melatonin/MT2 receptor signaling reduces pain by impeding Tet1-dependent demethylation of the mGluR5 promoter in spinal dorsal horn neurons. Spinal Tet1 gene transfer induces Tet1-mGluR5 promoter coupling, demethylation, and mGluR5 upregulation. Melatonin reverses Tet1-dependent mGluR5 promoter demethylation and associated mGluR5 expression and pain hypersensitivity via MT2 receptor.\",\n      \"method\": \"Intrathecal vector-mediated gene transfer, chromatin immunoprecipitation (Tet1-mGluR5 promoter), bisulfite sequencing (promoter methylation), intrathecal drug injection, behavioral pain testing, Western blot\",\n      \"journal\": \"Journal of pineal research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — multiple orthogonal methods (ChIP, bisulfite sequencing, behavior, pharmacology) in a single lab study identifying epigenetic regulation of mGluR5\",\n      \"pmids\": [\"28718992\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Patients' IgG antibodies against mGluR5 (primarily IgG1, ±IgG2/IgG3) cause a significant and specific decrease of cell-surface synaptic and extrasynaptic mGluR5 without altering PSD-95 levels, demonstrating pathogenic effects of anti-mGluR5 antibodies in encephalitis.\",\n      \"method\": \"Cell-based assays (antibody application to rat hippocampal neurons), immunohistochemistry (brain), IgG subclass determination, quantitative receptor cluster analysis\",\n      \"journal\": \"Neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct experimental demonstration of antibody-induced receptor loss in neurons across multiple patients, but single methodological approach\",\n      \"pmids\": [\"29703767\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"mGluR5 hypofunction in schizophrenia postmortem DLPFC is characterized by decreased Gq/11 coupling, reduced mGluR5 association with PI3K and Homer, increased serine and tyrosine phosphorylation of mGluR5 (causing desensitization), and altered protein-protein interactions with RGS4, Norbin, Preso1, and Tamalin. Reduced mGluR5-GluN physical association provides a mechanistic basis for impaired reciprocal mGluR5-NMDA receptor facilitation in schizophrenia.\",\n      \"method\": \"Co-immunoprecipitation (mGluR5-Gq/11, mGluR5-PI3K, mGluR5-Homer, mGluR5-GluN, mGluR5-RGS4, mGluR5-Norbin, mGluR5-Preso1, mGluR5-Tamalin), phosphorylation assays, agonist-induced signaling assays in postmortem tissue\",\n      \"journal\": \"Molecular psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — multiple co-IP experiments in postmortem human tissue, replicated across multiple interaction partners, but postmortem tissue limitations apply\",\n      \"pmids\": [\"30214040\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Homer1a induction enhances mGluR5 signaling, resulting in increased mTOR pathway phosphorylation and upregulation of synaptic AMPA receptor expression. The antidepressant action of sleep deprivation and Homer1a induction requires mGluR5 activation specifically in excitatory CaMK2a neurons and depends on enhanced AMPA receptor activity, translation, and trafficking.\",\n      \"method\": \"Cell-permeable TAT-Homer1a peptide injection, conditional knockout (mGluR5 in CaMK2a+ excitatory neurons), electrophysiology, Western blot (mTOR phosphorylation), AMPA receptor surface expression assays, behavioral antidepressant assays\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-type-specific conditional KO with multiple signaling and behavioral readouts, mechanistic pathway from mGluR5 to AMPA receptor validated in vivo\",\n      \"pmids\": [\"31420117\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"D1 dopamine receptor and mGluR5 form heteromeric receptor complexes on cell surfaces that couple to Gq proteins and produce synergistic PLC signaling and intracellular calcium release in response to either glutamate or dopamine. In dopamine-denervated striatum (Parkinson's disease model), D1-mGluR5 nanocomplexes are upregulated, leading to excessive ERK activation and dyskinesia.\",\n      \"method\": \"Co-immunoprecipitation, proximity ligation assay (nanoscale interaction), BRET/FRET (heteromer confirmation), calcium signaling assays, PLC assay, ERK phosphorylation assay in rodent PD models, behavioral dyskinesia testing\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods confirming heteromer formation (co-IP, PLA, BRET/FRET) plus functional signaling consequences and in vivo behavioral validation\",\n      \"pmids\": [\"32039920\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"FMRP deficiency in astroglia cell-autonomously upregulates miR-128-3p, which suppresses developmental mGluR5 expression in astrocytes. Selective in vivo inhibition of miR-128-3p in FMRP-deficient astroglia rescues decreased astroglial mGluR5 function. This FMRP→miR-128-3p→mGluR5 pathway is selective to astroglia and operates at the posttranscriptional level.\",\n      \"method\": \"Astrocyte-selective FMRP conditional knockout in vivo, miR-128-3p inhibition in vivo, mGluR5 functional assays, transcriptome and proteome profiling, Western blot\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo genetic rescue experiment (miRNA inhibition) combined with multiple profiling approaches, cell-autonomous mechanism established\",\n      \"pmids\": [\"32958647\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Astrocytic mGluR5, which transiently reemerges in adult somatosensory cortex astrocytes after nerve injury, drives Ca2+ signals and upregulates synaptogenic molecules (Thrombospondin-1, Glypican-4, Hevin), causing excess excitatory synaptogenesis and persistent mechanical allodynia. Astrocyte-specific deletion of mGluR5 abolishes all these events, establishing a causal role for astrocytic mGluR5 in pain-associated synaptic plasticity.\",\n      \"method\": \"Astrocyte-specific conditional knockout of mGluR5, Ca2+ imaging, immunohistochemistry (synaptogenic molecules), synaptic density quantification, behavioral pain testing (mechanical allodynia)\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — astrocyte-specific genetic KO with multiple orthogonal readouts (Ca2+ signals, molecular markers, synaptogenesis, behavior), mechanistic pathway from mGluR5 to allodynia established\",\n      \"pmids\": [\"35319723\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Treatment with the mGluR5 silent allosteric modulator (SAM) BMS-984923 prevents Aβ oligomer-induced aberrant synaptic mGluR5 signaling while preserving physiological glutamate responses, restoring synaptic density in Alzheimer's disease mouse models. SAM treatment prevents synaptic localization of complement component C1Q and synaptic engulfment, and normalizes neuronal gene expression patterns.\",\n      \"method\": \"Oral SAM drug treatment in aged AD mouse models (APPswe/PS1ΔE9, App/hMapt knock-in), [18F]FPEB PET for brain mGluR5 occupancy, [18F]SynVesT-1 PET for synaptic density (SV2A), single-nuclei transcriptomics, C1Q immunohistochemistry, synaptic engulfment assay, behavioral testing\",\n      \"journal\": \"Science translational medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo PET receptor occupancy, multiple AD mouse models, transcriptomics, and mechanistic complement pathway assays in a single comprehensive study\",\n      \"pmids\": [\"35648810\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"mGluR5 is dynamically organized in perisynaptic nanodomains positioned close to but excluded from the synapse. The C-terminal domain of mGluR5 critically controls perisynaptic confinement and prevents synaptic entry. Forced recruitment of mGluR5 to the synapse (via inducible interaction system) acutely increases synaptic calcium responses, demonstrating that perisynaptic localization shapes synaptic function.\",\n      \"method\": \"Live-cell super-resolution imaging (single-molecule localization microscopy), inducible chemogenetic interaction system to overcome synaptic exclusion, synaptic calcium imaging, C-terminal domain mutagenesis/truncation\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — super-resolution imaging plus molecular tool to acutely manipulate receptor localization with functional synaptic readout, multiple orthogonal approaches in single study\",\n      \"pmids\": [\"36646691\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The dimeric class C GPCR mGlu5 activates through an asymmetric, stepwise millisecond allosteric mechanism. Agonist binding induces dimeric ectodomain compaction amplified by cysteine-rich domain association, which loosely brings the 7TM domains into proximity establishing an asymmetric TM6-TM6 interface. Positive allosteric modulators stabilize the active inter-domain 7TM interface and an open ICL2 conformation, creating a pseudo-cavity (ICL2, ICL3, TM3, C-terminus) that facilitates G protein coordination.\",\n      \"method\": \"Markov state models (atomistic MD simulations), transition pathway generation, experimental signaling assays (validating simulation predictions)\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — computational structural modeling with experimental signaling validation, but experimental structural validation (cryo-EM/crystal structure) not performed; primarily computational with limited experimental confirmation\",\n      \"pmids\": [\"39209876\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GRM5/mGluR5 is a class C GPCR that couples to Gq/phospholipase C to drive IP3-dependent Ca2+ release and downstream kinase cascades (ERK, CaMK, CREB, Elk-1); it is organized in perisynaptic nanodomains through C-terminal interactions, internalizes via a clathrin-independent, dynamin-2-dependent pathway with constitutive recycling, and signals distinctly from cell-surface versus intracellular (ER/nuclear) membranes—intracellular activation requiring EAAT3-mediated glutamate transport and selectively driving ERK/Elk-1 and LTD; its activity is regulated by PKC-mediated phosphorylation at Ser901 that enhances Siah-1A binding over calmodulin to promote lysosomal trafficking, by p11/S100A10 binding to its cytoplasmic tail promoting surface expression, and by NHERF-2 PDZ interaction prolonging Ca2+ signaling; it forms functional heteromers with D1 receptors engaging Gq/PLC, interacts with Homer scaffolds to control trafficking and plasticity, synergizes with adenosine A2A receptors to regulate DARPP-32/cAMP signaling, and acts presynaptically to facilitate glutamate release; in neurons mGluR5 mediates protein-synthesis-dependent mGluR-LTD in the hippocampus and controls FMRP-dependent APP mRNA translation, while in astrocytes transient re-expression of mGluR5 drives synaptogenesis and modulates glutamate transporter function; in pathological states aberrant mGluR5 signaling—including D1-mGlu5 heteromer upregulation in dopamine-denervated striatum and Aβ oligomer-mediated synaptotoxic signaling via PrPC-mGluR5-Fyn—contributes to dyskinesia and Alzheimer's disease synaptic loss.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GRM5 (mGluR5) is a dimeric class C G-protein-coupled receptor that couples to Gq/phospholipase C to drive phosphoinositide hydrolysis and IP3-dependent Ca2+ mobilization, and is the principal group I metabotropic glutamate receptor controlling synaptic plasticity, sensory processing, and glial-neuronal signaling [#0, #2, #31]. The receptor is concentrated postsynaptically on dendritic spines and shafts with presynaptic axon-terminal expression, and it acts as a perisynaptic autoreceptor whose C-terminal domain confines it to nanodomains adjacent to but excluded from the synapse, a localization that gates synaptic Ca2+ responses [#0, #11, #30]. Activation of mGluR5 produces ERK, CaMK, and CREB signaling and is sufficient to induce protein-synthesis-dependent mGluR-LTD in hippocampal CA1 distinct from NMDAR-dependent LTD, while genetic loss impairs spatial learning and fear conditioning [#3, #5, #12]. mGluR5 signals from both the plasma membrane and intracellular ER/nuclear membranes; the intracellular pool is supplied with glutamate by the transporter EAAT3 and selectively drives sustained Ca2+ rises, ERK1/2-Elk-1 signaling, immediate-early gene induction, and LTD, and underlies neuropathic pain behaviors [#12, #15, #18]. Its surface availability and trafficking are tightly regulated: it internalizes constitutively via a clathrin-independent, dynamin-2-dependent route with recycling to the surface [#6, #14]; PKC phosphorylation at Ser901 displaces calmodulin to favor Siah-1A binding and lysosomal degradation [#13]; and p11/S100A10 binding to the cytoplasmic tail and NHERF-2 PDZ interaction promote surface expression and prolong Ca2+ signaling, respectively [#9, #16]. mGluR5 is embedded in a wider receptor and scaffold network—forming Gq-coupled heteromers with D1 dopamine receptors, synergizing with adenosine A2A receptors to potentiate DARPP-32 phosphorylation, cooperating with CB1 receptors for neuroprotection, and engaging Homer scaffolds to drive mTOR-dependent AMPA receptor plasticity [#7, #19, #25, #26]. It links to translational control through FMRP, releasing FMRP repression of APP mRNA upon activation [#10], and astrocytic mGluR5 transiently re-emerging after injury drives synaptogenesis and allodynia [#28]. Aberrant mGluR5 signaling contributes to L-DOPA-induced dyskinesia via upregulated D1-mGlu5 nanocomplexes [#26] and to Alzheimer's disease synaptic loss via Abeta-oligomer-driven aberrant signaling that allosteric modulators can normalize [#29], and pathogenic anti-mGluR5 IgG antibodies cause receptor internalization in encephalitis [#23].\",\n  \"teleology\": [\n    {\n      \"year\": 1995,\n      \"claim\": \"Established mGluR5 as a Gq-coupled receptor driving phosphoinositide hydrolysis and Ca2+ mobilization and mapped its predominantly postsynaptic, partly presynaptic and astroglial distribution, defining where it acts.\",\n      \"evidence\": \"Receptor-specific Western blot, immunocytochemistry, and immunoelectron microscopy in rat brain with transfection of nonneuronal cells\",\n      \"pmids\": [\"7636025\", \"8576426\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve functional differences between presynaptic and postsynaptic pools\", \"Coupling partners beyond PI hydrolysis not addressed\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Showed in native astrocytes that mGluR5 activation drives PI hydrolysis without cAMP and undergoes two-phase desensitization, distinguishing a phosphorylation-independent early phase from protein-synthesis-dependent resensitization.\",\n      \"evidence\": \"Pharmacological PI hydrolysis and cAMP assays with phorbol esters and down-regulation assays in cultured astrocytes\",\n      \"pmids\": [\"9202306\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mediators of early desensitization not identified\", \"In vivo relevance not tested\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Defined mGluR5 as both necessary and sufficient for protein-synthesis-dependent hippocampal LTD and for spatial/contextual memory, separating it mechanistically from NMDAR-dependent plasticity.\",\n      \"evidence\": \"Hippocampal slice electrophysiology with selective DHPG/antagonists and protein synthesis inhibitors; mGluR5 knockout mice in Morris water maze and fear conditioning\",\n      \"pmids\": [\"11431513\", \"11566212\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream PKC/Src pathway to memory was inferred not directly demonstrated\", \"Subcellular site of LTD induction unresolved at this stage\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Identified a peripheral pro-nociceptive role for mGluR5 on primary afferent terminals, localizing analgesic relevance to the periphery.\",\n      \"evidence\": \"Intraplantar/i.c.v./intrathecal MPEP, behavioral pain testing, dorsal-horn neuron recordings, and mGluR5/TRPV1 co-labeling\",\n      \"pmids\": [\"11077066\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Intracellular signaling linking peripheral mGluR5 to hyperalgesia not defined here\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Revealed mGluR5 endocytoses constitutively through a clathrin-independent, dynamin-2-dependent route, redefining its trafficking distinct from canonical GPCR pathways.\",\n      \"evidence\": \"Imaging and biochemical endocytosis assays with dominant-negative Eps15 and dynamin-2 in COS-7 cells and neurons\",\n      \"pmids\": [\"12529370\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Post-endocytic fate (recycling vs degradation) not fully resolved\", \"Adaptor proteins for the clathrin-independent route unknown\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Showed mGluR5 cross-talks with adenosine A2A receptors to potentiate DARPP-32 phosphorylation via cAMP/ERK independently of PLC, establishing receptor synergy in striatum.\",\n      \"evidence\": \"Neostriatal slice pharmacology with receptor antagonists and kinase inhibitors, DARPP-32 phospho-assays\",\n      \"pmids\": [\"12538871\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physical basis of mGluR5-A2A interaction not defined\", \"In vivo behavioral consequence not tested here\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Demonstrated bidirectional mGluR5 control of NMDAR responses—Ca2+/PKC-dependent inhibition versus tonic tyrosine-kinase-dependent potentiation—revealing context-dependent crosstalk.\",\n      \"evidence\": \"Ca2+ imaging in HEK293 cells co-expressing NMDAR subunits with thapsigargin, PKC, PTK, and PTP inhibitors\",\n      \"pmids\": [\"15210575\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Heterologous cells only\", \"Native neuronal validation absent\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Identified NHERF-2 as a selective C-terminal PDZ partner of mGluR5 that prolongs Ca2+ signaling and potentiates excitotoxicity, linking scaffolding to signal duration.\",\n      \"evidence\": \"PDZ array screen, reverse overlay, point mutagenesis, reciprocal co-IP, calcium and cell-death assays\",\n      \"pmids\": [\"16891310\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological cell-death relevance in vivo not established\", \"Interplay with other C-terminal partners not addressed\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Connected mGluR5 to translational control by showing activation releases FMRP repression of APP mRNA, linking the receptor to local protein synthesis and Abeta production.\",\n      \"evidence\": \"RNA-protein binding, FMRP-APP mRNA co-IP, DHPG stimulation of synaptoneurosomes, fmr-1 KO comparison, Abeta ELISA\",\n      \"pmids\": [\"17298186\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signaling steps from mGluR5 to FMRP release not mapped\", \"In vivo APP/Abeta consequences not quantified\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Confirmed mGluR5 functions as a bona fide presynaptic autoreceptor facilitating glutamate exocytosis, using genetic deletion to validate concentration-dependent pharmacology.\",\n      \"evidence\": \"Synaptosome [3H]D-aspartate release with selective antagonists and mGluR5 knockout, subsynaptic fractionation\",\n      \"pmids\": [\"18625255\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Presynaptic signaling cascade not dissected\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Discovered that surface versus intracellular mGluR5 pools generate distinct Ca2+ signatures and signaling outputs, with intracellular receptor uniquely driving ERK/Elk-1 and immediate-early genes.\",\n      \"evidence\": \"Cell-permeable vs impermeable ligand isolation, Ca2+ imaging, phospho-protein and gene-expression assays with kinase inhibitors\",\n      \"pmids\": [\"19840937\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Source of intracellular ligand not yet identified at this stage\", \"Native tissue confirmation pending\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Defined the regulatory switch by which PKC phosphorylation at Ser901 displaces calmodulin to favor Siah-1A binding, routing mGluR5 to lysosomal degradation, while a parallel study established constitutive recycling in heterologous cells.\",\n      \"evidence\": \"Co-IP, S901 mutagenesis, surface biotinylation, and lysosomal/recycling trafficking assays in neurons and HEK293 cells\",\n      \"pmids\": [\"23152621\", \"22995293\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Conditions selecting recycling versus degradation in vivo not defined\", \"Kinetics of CaM/Siah-1A competition unresolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Localized intracellular mGluR5 to ER/nuclear membranes supplied with glutamate by EAAT3 and showed it selectively mediates LTD but not LTP, providing the missing source for intracellular activation.\",\n      \"evidence\": \"Cell-permeable/impermeable ligand isolation, radiolabeled agonist uptake, EAAT3 inhibition, Ca2+ imaging, hippocampal slice electrophysiology\",\n      \"pmids\": [\"24672004\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism targeting receptor to intracellular membranes unclear\", \"Relative contribution of surface vs intracellular pool to physiological LTD unsettled\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Established p11/S100A10 as a tail-binding partner promoting mGluR5 surface expression and Ca2+ signaling with opposing behavioral effects in glutamatergic versus GABAergic neurons, and showed biased PAMs can separate Gq signaling from NMDAR modulation in vivo.\",\n      \"evidence\": \"Co-IP, surface biotinylation, calcium assays, cell-type-specific conditional KO and behavior; biased PAM electrophysiology, signaling, and behavioral models\",\n      \"pmids\": [\"26370144\", \"25937172\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of biased PAM signaling not resolved\", \"How p11 directs receptor trafficking mechanistically unclear\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Extended intracellular mGluR5 biology to spinal nociception—nuclear-membrane receptor driving sustained Ca2+ and pERK/Arc/c-fos underlies neuropathic pain—and identified cooperative mGluR5-CB1 neuroprotection via MEK/ERK and PI3K/AKT.\",\n      \"evidence\": \"Subcellular fractionation, Ca2+ imaging, intrathecal cell-permeable/impermeable antagonists, EAAT-3 inhibition, behavior; primary neuron receptor blockade/ablation with kinase inhibitors\",\n      \"pmids\": [\"26837579\", \"27543109\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physical mGluR5-CB1 association not demonstrated\", \"Neuroprotection mechanism is correlative for some signaling steps\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Broadened mGluR5 roles to peripheral TRP channel sensitization via PKCepsilon, immune RANTES/NF-kB signaling in T cells, and epigenetic (Tet1-dependent) transcriptional control of the mGluR5 promoter.\",\n      \"evidence\": \"In vivo pain behavior with peripheral pharmacology and PKCepsilon assays; Jurkat T-cell agonist/antagonist with NF-kB reporter; intrathecal Tet1 gene transfer with ChIP and bisulfite sequencing\",\n      \"pmids\": [\"28621704\", \"29849049\", \"28718992\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"T-cell findings rest on a single cell line\", \"Pain pathways established pharmacologically rather than biochemically\", \"Generality of Tet1-mGluR5 epigenetic regulation beyond pain unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Linked mGluR5 dysregulation to human disease—pathogenic anti-mGluR5 IgG internalizes surface receptor in encephalitis, and schizophrenia DLPFC shows reduced Gq/Homer/PI3K coupling with hyperphosphorylation and altered scaffold interactions.\",\n      \"evidence\": \"Patient IgG application to neurons with receptor cluster quantification; co-IP of mGluR5 with Gq/11, Homer, PI3K, GluN, RGS4, Norbin, Preso1, Tamalin and phospho-assays in postmortem tissue\",\n      \"pmids\": [\"29703767\", \"30214040\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Postmortem associations are correlative\", \"Causal direction of phosphorylation changes in disease unresolved\", \"Single methodological approach for antibody pathogenicity\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Showed Homer1a-enhanced mGluR5 signaling drives mTOR-dependent AMPA receptor potentiation underlying rapid antidepressant action, requiring mGluR5 specifically in CaMK2a excitatory neurons.\",\n      \"evidence\": \"TAT-Homer1a peptide, conditional mGluR5 KO in CaMK2a neurons, electrophysiology, mTOR phospho-assays, AMPAR surface assays, antidepressant behavior\",\n      \"pmids\": [\"31420117\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct structural Homer1a-mGluR5 engagement during this response not resolved\", \"Link between mTOR and AMPAR trafficking incompletely defined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Demonstrated D1-mGluR5 heteromers couple to Gq for synergistic PLC/Ca2+ signaling and are upregulated in dopamine-denervated striatum, driving excessive ERK and dyskinesia.\",\n      \"evidence\": \"Co-IP, proximity ligation, BRET/FRET, calcium/PLC and ERK assays in rodent Parkinson's models with dyskinesia behavior\",\n      \"pmids\": [\"32039920\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and interface of the heteromer not defined\", \"Therapeutic targetability of the heteromer untested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Established astrocytic mGluR5 re-emergence after injury as causally driving synaptogenesis and allodynia, and validated mGluR5 silent allosteric modulation to normalize Abeta-driven synaptotoxic signaling and restore synapses in AD models.\",\n      \"evidence\": \"Astrocyte-specific mGluR5 KO with Ca2+ imaging, synaptogenic-molecule IHC and behavior; oral SAM BMS-984923 with PET occupancy/synaptic density, single-nuclei transcriptomics, and C1Q/engulfment assays in AD mice\",\n      \"pmids\": [\"35319723\", \"35648810\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signaling cascade from astrocytic mGluR5 to synaptogenic gene expression not fully mapped\", \"Translation of SAM efficacy to humans untested in these studies\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Resolved that mGluR5 is dynamically confined to perisynaptic nanodomains by its C-terminal domain, and that forcing synaptic entry acutely boosts synaptic Ca2+, linking nanoscale localization to function.\",\n      \"evidence\": \"Single-molecule localization microscopy, inducible chemogenetic recruitment, synaptic Ca2+ imaging, and C-terminal mutagenesis\",\n      \"pmids\": [\"36646691\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular tethers enforcing perisynaptic exclusion not identified\", \"Physiological signals that mobilize the receptor to synapses unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Provided a stepwise asymmetric allosteric activation model for the dimeric receptor, explaining how agonist-driven ectodomain compaction and PAM-stabilized 7TM interfaces enable G-protein coordination.\",\n      \"evidence\": \"Markov state models from atomistic MD simulations with experimental signaling validation\",\n      \"pmids\": [\"39209876\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No experimental high-resolution structure of the activation intermediates\", \"Computational mechanism awaits cryo-EM confirmation\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How surface versus ER/nuclear mGluR5 pools are differentially targeted, scaffolded, and recruited to perisynaptic nanodomains—and how these spatial states are coordinated to select signaling and plasticity outcomes—remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Trafficking determinants directing receptor to intracellular membranes unknown\", \"Molecular tethers enforcing perisynaptic confinement unidentified\", \"How biased pharmacology maps onto subcellular pools in vivo is undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 2, 31]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [7, 8, 24]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [12]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1, 6, 30]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [15]},\n      {\"term_id\": \"GO:0005635\", \"supporting_discovery_ids\": [15, 18]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [6, 13, 14]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 7, 12, 26]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [3, 11, 15, 25]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [26, 29, 23]}\n    ],\n    \"complexes\": [\n      \"D1-mGluR5 heteromer\"\n    ],\n    \"partners\": [\n      \"NHERF2\",\n      \"S100A10\",\n      \"SIAH1\",\n      \"CALM1\",\n      \"HOMER1\",\n      \"DRD1\",\n      \"ADORA2A\",\n      \"FMR1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}