{"gene":"GPSM1","run_date":"2026-04-28T18:06:53","timeline":{"discoveries":[{"year":2001,"finding":"AGS3's C-terminal domain contains four GPR (G-protein regulatory) motifs that selectively bind the GDP-bound conformation of Gαi (not GTPγS-bound), compete with Gβγ for Gαi(GDP) binding, and act as a guanine nucleotide dissociation inhibitor (GDI), blocking GTPγS binding to Gαi. AGS3 co-immunoprecipitates with Gαi3 from cell and tissue lysates.","method":"Co-immunoprecipitation, GST pulldown with purified Gα subunits, GTPγS binding assays, immunofluorescence/confocal imaging","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro biochemical assays with purified proteins replicated across multiple methods; foundational paper with >130 citations","pmids":["11042168"],"is_preprint":false},{"year":2000,"finding":"A consensus GPR peptide from AGS3 stabilizes the GDP-bound conformation of Gαi (functions as GDI), inhibits GTPγS binding to Gαi1/2, and blocks receptor coupling to Gαiβγ, indicating that AGS3-GPR-stabilized Gαi(GDP) is not recognized by GPCRs.","method":"In vitro GTPγS binding assays, receptor-G protein coupling assays with purified proteins and peptides","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro with purified proteins and synthetic peptides, multiple assays","pmids":["10969064"],"is_preprint":false},{"year":2000,"finding":"The AGS3 GPR domain inhibits GDP dissociation from Gαi and rhodopsin-stimulated GDP release from Gαt, acting as a GDP dissociation inhibitor. The full-length GPR domain (residues 463–650) is ~30-fold more potent than a two-GPR-motif fragment, and does not alter the catalytic rate of GTP hydrolysis by Gαt.","method":"In vitro kinetic assays of GTPγS binding, GDP release (stopped-flow/fluorescence), steady-state GTP hydrolysis with purified Gα subunits","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — rigorous in vitro reconstitution with purified proteins and quantitative kinetics","pmids":["11024022"],"is_preprint":false},{"year":2001,"finding":"AGS3 exists in two forms: a full-length brain-enriched form (AGS3-LONG, 650 aa) and a heart-enriched truncated form (AGS3-SHORT, starting at Met495) that lacks TPR domains but retains GPR motifs. Both forms selectively bind Gαi1/2/3 in GDP-bound conformation and inhibit GTPγS binding, but they differ in subcellular distribution.","method":"cDNA library screening, RNase protection, GST pulldown with purified Gα, GTPγS binding assay, immunofluorescence, subcellular fractionation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods identifying a novel isoform with distinct biochemical properties","pmids":["11278352"],"is_preprint":false},{"year":2002,"finding":"LGN (but not AGS3) translocates from the nucleus to the midbody during cytokinesis in PC12 and COS7 cells, suggesting a role for LGN/G-proteins in cytokinesis; AGS3 and LGN have distinct subcellular distributions regulated by cell cycle and external stimuli.","method":"Immunocytochemistry, confocal microscopy, cell cycle analysis in dividing cells","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 — direct localization by imaging with cell-cycle correlation, single lab","pmids":["11832491"],"is_preprint":false},{"year":2003,"finding":"AGS3 localizes to compartments compatible with autophagosome formation and its C-terminal GPR domain (which binds Gαi3) promotes macroautophagy, while its N-terminal domain (non-Gαi3-interacting) inhibits autophagy; AGS3 acts at an early event in the autophagic pathway prior to autophagosome formation.","method":"Immunofluorescence localization, expression of domain truncation mutants, biochemical and morphometric analysis of autophagic flux in HT-29 cells","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 — domain dissection with functional autophagy readout in cell lines, single lab","pmids":["12642577"],"is_preprint":false},{"year":2003,"finding":"AGS3 interacts with the serine/threonine kinase LKB1; LKB1 immunoprecipitates phosphorylate the GPR domains of AGS3, and phosphorylation within the GPR motif reduces binding to Gα, suggesting that LKB1-mediated phosphorylation of GPR domains is a regulatory mechanism for AGS3–G-protein interactions.","method":"Yeast two-hybrid screen, co-immunoprecipitation from mammalian cells/brain lysate, in vitro phosphorylation assay, GPR peptide competition","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 — multiple assays identifying kinase-substrate relationship and functional consequence on G-protein binding, single lab","pmids":["12719437"],"is_preprint":false},{"year":2003,"finding":"AGS3-C (C-terminal domain) possesses two high-affinity (Kd ~20 nM) and two low-affinity (Kd ~300 nM) binding sites for Gαi1; individual GPR motif peptides bind with Kd 1–8 µM. Residues flanking the GPR core strongly potentiate binding affinity and GDI activity. GPR3 alone lacks GDI activity but gains it with flanking residues.","method":"Isothermal titration calorimetry (ITC), fluorescent GTP analog binding assay with purified proteins and peptides","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — quantitative thermodynamic characterization by ITC with purified proteins","pmids":["14530282"],"is_preprint":false},{"year":2003,"finding":"Cytosolic (not membrane-associated) AGS3 can interact with Gαi subunits and disrupt receptor-G protein coupling; cytosolic AGS3 removes Gαi subunits from the membrane and sequesters them in the cytosol, as shown in an Sf9 membrane reconstitution system.","method":"Sf9 membrane-based receptor-G protein coupling reconstitution, GST pulldown, immunoblotting of membrane/cytosolic fractions","journal":"Biochemistry","confidence":"Medium","confidence_rationale":"Tier 1-2 — reconstitution system with defined fractions, single lab","pmids":["12834360"],"is_preprint":false},{"year":2004,"finding":"AGS3-SHORT blocks adenylyl cyclase sensitization that normally follows prolonged Gαi-coupled receptor activation; this effect requires intact G-protein binding by AGS3, and is correlated with AGS3 stabilizing Gαi3 in the membrane and slowing Gαi3 decay.","method":"cAMP measurement in CHO cells, immunoblot of membrane Gαi3, G-protein binding mutant controls","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — cell-based functional assay with mutant controls, single lab","pmids":["14726514"],"is_preprint":false},{"year":2005,"finding":"AGS3 (and Gβγ) regulate mitotic spindle orientation in neural progenitors of the developing neocortex; silencing AGS3 shifts spindle orientation from apical-basal to planar divisions, causing hyperdifferentiation of progenitors due to both daughter cells adopting a neuronal fate.","method":"In utero RNA interference in mouse neocortex, spindle angle measurements, cell fate analysis by immunofluorescence","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 — clean loss-of-function with defined cellular phenotype (spindle orientation + cell fate), highly cited foundational paper","pmids":["16009138"],"is_preprint":false},{"year":2006,"finding":"Human Inscuteable (mInsc) proteins bind to both LGN and AGS3 through their TPR domains, and to Par3/Par3β; coexpression of mInsc bridges LGN and Par3 (which do not interact directly), indicating mInsc is an adaptor linking Pins homologs to the Par polarity complex.","method":"Co-immunoprecipitation from transfected mammalian cells","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 3 — co-IP from transfected cells, single lab, single method","pmids":["16458856"],"is_preprint":false},{"year":2007,"finding":"AGS3 overexpression alters surface expression of a subset of plasma membrane receptors/channels and disrupts trans-Golgi network (TGN)-associated cargo localization without affecting cis- or medial-Golgi; AGS3 knockdown similarly disperses TGN markers, implicating AGS3 in protein trafficking along the TGN/plasma membrane/endosome loop.","method":"Biotin-based internalization assay, immunofluorescence of Golgi markers, siRNA knockdown, flow cytometry of surface proteins","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2-3 — gain- and loss-of-function convergent results for TGN trafficking, single lab","pmids":["17991770"],"is_preprint":false},{"year":2008,"finding":"Ric-8A (a GEF) catalyzes rapid GDP release from the AGS3-C:Gαi1·GDP complex by forming a transient ternary complex; subsequent dissociation of AGS3 and GDP yields a stable nucleotide-free Ric-8A·Gαi1 complex that proceeds to Gαi1·GTP upon GTP addition. AGS3 cannot reverse the Ric-8A·Gαi1 complex, ensuring unidirectional Gα activation.","method":"Pulldown assays, gel filtration, isothermal titration calorimetry, stopped-flow fluorescence spectroscopy with purified proteins","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — multiple orthogonal in vitro methods with purified proteins establishing ternary complex mechanism","pmids":["18541531"],"is_preprint":false},{"year":2008,"finding":"AGS3 upregulation in rat nucleus accumbens core during ethanol abstinence drives ethanol-seeking behavior through Gβγ signaling; AGS3 knockdown or Gβγ sequestration (but not Gαi knockdown) reduced ethanol seeking, placing AGS3 upstream of Gβγ in this behavioral circuit.","method":"Lentiviral shRNA knockdown in rat brain, operant ethanol self-administration model, pharmacological Gβγ sequestration, Gαi knockdown","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis (knockdown) + pharmacological dissection in vivo, single lab","pmids":["18719114"],"is_preprint":false},{"year":2010,"finding":"AGS3 interacts with LC3 (autophagosome marker), recruits Gαi3 to LC3-positive membranes upon starvation, and promotes autophagy by acting as GDI for Gαi3. Upon growth factor stimulation, GIV (a GEF for Gαi3) disrupts the Gαi3–AGS3 complex, releasing Gαi3 from LC3-positive membranes and inhibiting autophagy.","method":"Protein-protein interaction assays (co-IP, pulldown), G protein enzymology, morphological analysis of autophagy (LC3 puncta), starvation/growth factor conditions","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods including biochemistry and cell biology, direct mechanistic pathway established","pmids":["21209316"],"is_preprint":false},{"year":2010,"finding":"α2-adrenergic and μ-opioid receptor activation reduces AGS3–Gαi1 BRET signal by >30% (pertussis toxin- and RGS4-sensitive), indicating that GPCR activation dissociates the AGS3·Gαi complex at the cell cortex. AGS3 also shows BRET with GPCRs, suggesting it is part of a larger receptor signaling complex.","method":"Bioluminescence resonance energy transfer (BRET) in live mammalian cells, pharmacological and genetic controls (pertussis toxin, RGS4, GRK2-ct)","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — BRET in living cells with multiple controls, single lab","pmids":["20716524"],"is_preprint":false},{"year":2010,"finding":"AGS3 enters the aggresome pathway; Gαi rescues AGS3 from the aggresome, whereas mInsc augments aggresome-like distribution. TPR domain integrity and a specific nonsynonymous SNP regulate AGS3 aggresome entry, revealing that Gαi and mInsc bidirectionally control AGS3 subcellular distribution under cellular stress.","method":"Immunofluorescence, confocal microscopy, co-expression with Gαi/mInsc, TPR domain mutant and SNP analysis in COS7 cells","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2-3 — domain mutagenesis + protein binding partners controlling localization, single lab","pmids":["20065032"],"is_preprint":false},{"year":2010,"finding":"AGS3 interacts with the deubiquitinating enzyme USP9x (interaction mediated through AGS3's C-terminal GPR domain); USP9x knockdown reduces AGS3 levels, while USP9x or its deubiquitinating domain UCH overexpression increases AGS3, indicating USP9x stabilizes a subpopulation of AGS3 through deubiquitination.","method":"Co-immunoprecipitation, USP9x knockdown, overexpression of catalytic domain mutants, immunofluorescence of Golgi markers","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2-3 — interaction + functional consequence on protein levels with catalytic mutant control, single lab","pmids":["20305814"],"is_preprint":false},{"year":2009,"finding":"Morphine withdrawal-induced cAMP superactivation requires AGS3 upregulation; elevated AGS3 binds Gαi and prevents its inhibition of adenylyl cyclase, while withdrawal-induced cAMP/PKA activates phospholipase C and εPKC to further stimulate AC5 and AC7.","method":"cAMP measurement in nucleus accumbens/striatal neurons, AGS3 knockdown, pharmacological dissection of Gβγ vs Gαi involvement, AC5/AC7 identification","journal":"Molecular pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — cell-based functional dissection with AGS3 knockdown and downstream pathway identification, single lab","pmids":["19549762"],"is_preprint":false},{"year":2011,"finding":"In C. elegans, AGS-3 (GPSM1 ortholog) activates Gαo signaling in ASH chemosensory neurons in response to food deprivation; genetic epistasis shows AGS-3 and the GEF RIC-8 act in ASH in a mutually dependent fashion to activate Gαo, requiring the GPR domain–Gαo interaction, and Gαo-GTP is the downstream signaling molecule.","method":"Genetic epistasis analysis in C. elegans (double mutants, tissue-specific rescue), behavioral assays (octanol aversion delay), biochemical fractionation","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with multiple alleles and tissue-specific experiments establishing pathway order","pmids":["21832186"],"is_preprint":false},{"year":2014,"finding":"AGS3 is required for proper chemokine receptor signaling in leukocytes; AGS3-null B and T lymphocytes and dendritic cells show defects in chemotaxis, reduced chemokine-stimulated calcium mobilization, and altered ERK and Akt activation.","method":"Characterization of Gpsm1-/- mice: chemotaxis assays, calcium flux measurements, ERK/Akt phosphorylation immunoblots in primary immune cells","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — clean knockout with defined signaling phenotypes in primary cells, single lab","pmids":["24573680"],"is_preprint":false},{"year":2017,"finding":"AGS3 is not recruited to the cell cortex in mouse neural progenitors and does not rescue LGN loss of function in oriented divisions; despite conserved in vitro interactions with NuMA and Gαi, AGS3 lacks spindle orientation function in vivo, revealing that species-specific modulation of interactions distinguishes LGN and AGS3 function.","method":"In utero electroporation (mouse neocortex), LGN rescue experiments, in vitro binding assays, spindle angle measurements","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 — loss-of-function + rescue experiments in vivo combined with in vitro binding, single lab","pmids":["28684399"],"is_preprint":false},{"year":2018,"finding":"Phosphorylation of AGS3 at a single threonine (T602) in the GPR domain regulates its subcellular distribution: AGS3-T602A localizes to cytosolic puncta instead of cortical/diffuse distribution, and this punctate localization is rescued by co-expression of Gαi or Gαo but not Gαs or Gαq, indicating that GPR phosphorylation controls G-protein-dependent subcellular positioning of AGS3.","method":"Site-directed mutagenesis, immunofluorescence in COS7 cells, alkaline phosphatase treatment + SDS-PAGE gel shift, co-expression with Gα subunits","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 — mutagenesis + rescue experiments linking specific phosphosite to subcellular distribution, single lab","pmids":["30404823"],"is_preprint":false},{"year":2020,"finding":"AGS3 regulates E-cadherin (Cdh1) transport to the plasma membrane via the trans-Golgi network in early mouse embryos; AGS3 knockout arrests embryo development after the 4-cell stage with decreased membrane Cdh1 accumulation and dispersal of TGN markers; Gαi1 overexpression rescues AGS3-overexpression phenotype, indicating Gαi1 acts downstream of AGS3 in TGN-to-membrane trafficking.","method":"CRISPR/Cas9 knockout in mouse embryos, fluorescent protein tagging of TGN markers (TGN46, TMED7), live imaging, Gαi1 rescue experiment","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 — genetic KO with rescue and live imaging in embryos, single lab","pmids":["33148610"],"is_preprint":false},{"year":2020,"finding":"AGS3 and Gαi3 are co-upregulated as part of the spindle orientation complex during human neural progenitor cell differentiation; co-immunoprecipitation shows AGS3 preferentially interacts with Gαi3 (not Gαi1/2) in differentiated cells, and this interaction is suppressed by GTPγS and pertussis toxin, indicating AGS3 recognizes the same Gα binding site as GPCRs.","method":"Co-immunoprecipitation, western blot from differentiating neural progenitor cell lines, GTPγS and pertussis toxin treatments","journal":"Molecules","confidence":"Medium","confidence_rationale":"Tier 3 — co-IP in cell lines with pharmacological controls, single lab","pmids":["33172018"],"is_preprint":false},{"year":2022,"finding":"Myeloid GPSM1 promotes metabolic inflammation; GPSM1 deficiency in macrophages mainly promotes TNFAIP3 transcription via the Gαi3/cAMP/PKA/CREB axis, thereby inhibiting TLR4-induced NF-κB signaling. USP9X prevents GPSM1 degradation through K63-polyubiquitination stabilization.","method":"Myeloid-specific GPSM1 knockout mice, high-fat diet metabolic phenotyping, ChIP-PCR, mass spectrometry, co-immunoprecipitation, macrophage signaling assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1-2 — in vivo KO + multiple mechanistic biochemical assays establishing Gαi3/cAMP/PKA/CREB→TNFAIP3 pathway","pmids":["36434066"],"is_preprint":false},{"year":2023,"finding":"AGS3 negatively regulates LGN to balance spindle orientation in mammalian epidermis; AGS3 overexpression displaces LGN from the apical cortex and increases planar divisions, AGS3 loss prolongs cortical LGN localization and biases toward perpendicular divisions; genetic epistasis in double mutants confirms AGS3 acts through LGN. Clonal lineage tracing shows AGS3 promotes symmetric fates and LGN promotes asymmetric fates.","method":"In vivo mouse epidermal genetic manipulation, static and ex vivo live imaging, genetic epistasis (double mutant analysis), clonal lineage tracing","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 — multiple in vivo approaches (imaging, epistasis, lineage tracing) establishing AGS3 as negative regulator of LGN-dependent spindle orientation","pmids":["37017303"],"is_preprint":false},{"year":2023,"finding":"GPSM1 deficiency in POMC neurons protects against diet-induced obesity by enhancing autophagy and improving leptin sensitivity through PI3K/AKT/mTOR signaling, increasing POMC/α-MSH production and sympathetic innervation of brown adipose tissue.","method":"POMC-neuron-specific GPSM1 knockout mice, high-fat diet metabolic phenotyping, immunofluorescence, immunohistochemistry, molecular pathway analysis (PI3K/AKT/mTOR)","journal":"Molecular metabolism","confidence":"Medium","confidence_rationale":"Tier 2 — cell-type-specific KO with mechanistic pathway analysis in vivo, single lab","pmids":["37979657"],"is_preprint":false},{"year":2025,"finding":"AGS3 binds NuMA and Gαi3·GDP in vitro similarly to LGN, but cannot form stable hetero-hexamers or higher-order oligomeric complexes with NuMA that are required for spindle orientation. The ~20 N-terminal residues preceding the conserved TPR motifs account for this difference. Insc disrupts the AGS3/NuMA oligomeric complex but not the LGN/NuMA complex, further distinguishing their spindle orientation functions.","method":"Biochemical reconstitution, gel filtration, pulldown assays, structural characterization of AGS3 vs LGN domain truncations","journal":"Journal of molecular cell biology","confidence":"Medium","confidence_rationale":"Tier 1-2 — in vitro reconstitution with domain mutants establishing molecular basis for AGS3/LGN functional difference, single lab","pmids":["39580365"],"is_preprint":false},{"year":2025,"finding":"GPSM1 is stabilized by USP9X via prevention of K63-polyubiquitination-dependent degradation; GPSM1 stabilization leads to MEIS3 nuclear translocation, activating CSF1 (macrophage colony-stimulating factor) expression, driving M2 macrophage polarization and anti-PD-1 resistance in colorectal cancer.","method":"ChIP-PCR, mass spectrometry, co-immunoprecipitation, single-cell RNA sequencing, orthotopic CRC model, macrophage polarization assays","journal":"Journal for immunotherapy of cancer","confidence":"Medium","confidence_rationale":"Tier 2 — multiple biochemical methods establishing ubiquitination mechanism and downstream transcriptional pathway, single lab","pmids":["40010765"],"is_preprint":false},{"year":2025,"finding":"Plasma membrane recruitment of an optogenetic tool based on AGS3's GPR motif (OptoGDI) releases Gβγ in living cells in a GPCR-independent manner, generating localized PIP3 and triggering macrophage migration, directly demonstrating that AGS3-mediated GDI activity on Gαi is sufficient to produce free Gβγ signaling.","method":"Optogenetics in living cells, PIP3 biosensor imaging, macrophage migration assay","journal":"Open biology","confidence":"Medium","confidence_rationale":"Tier 2 — optogenetic gain-of-function in live cells with functional readout, novel approach","pmids":["39904370"],"is_preprint":false}],"current_model":"GPSM1/AGS3 is a modular scaffold protein with N-terminal TPR repeats and C-terminal GPR (GoLoco) motifs that functions primarily as a guanine nucleotide dissociation inhibitor (GDI) for Gαi/o subunits: its GPR domain selectively binds GDP-bound Gαi, stabilizes this conformation, competes with Gβγ for Gαi(GDP) binding, and thereby liberates free Gβγ for downstream signaling; its GDI activity is antagonized by the GEF Ric-8A (which can displace AGS3 from Gαi and drive Gα activation) and is regulated by LKB1-mediated phosphorylation of the GPR domain and by USP9X-mediated deubiquitination; subcellular distribution of AGS3 is dynamically controlled by Gαi binding and phosphorylation of T602; through these mechanisms AGS3 regulates spindle orientation (antagonizing LGN in epithelia), autophagy initiation (recruiting Gαi3 to LC3-positive membranes), trans-Golgi network trafficking, chemokine receptor signaling in immune cells, and neuronal cAMP homeostasis during drug withdrawal."},"narrative":{"teleology":[{"year":2000,"claim":"The fundamental question of how AGS3 acts on G proteins was resolved: GPR motifs stabilize Gαi in the GDP-bound state by inhibiting nucleotide exchange, establishing AGS3 as a GDI rather than a GEF or GAP, and showing that GPR-bound Gαi·GDP is not recognized by GPCRs.","evidence":"In vitro GTP γS binding, GDP release kinetics, and receptor-G protein coupling assays with purified proteins and synthetic peptides","pmids":["10969064","11024022"],"confidence":"High","gaps":["Structural basis of GPR–Gαi interaction at atomic resolution not yet determined","Relative contribution of individual GPR motifs to GDI activity in vivo unknown"]},{"year":2001,"claim":"The selectivity and cellular context of AGS3–Gα interaction was established: four GPR motifs selectively bind GDP-Gαi (not GTP-bound), compete with Gβγ, and co-immunoprecipitate with Gαi3 from tissues; a brain-enriched long isoform and heart-enriched short isoform with distinct distributions were identified.","evidence":"Co-IP from cell/tissue lysates, GST pulldown, GTPγS binding assays, cDNA cloning, RNase protection assays","pmids":["11042168","11278352"],"confidence":"High","gaps":["Functional distinction between long and short isoforms in vivo not established","Tissue-specific regulation of isoform expression unknown"]},{"year":2003,"claim":"Multiple regulatory inputs on AGS3 were discovered simultaneously: LKB1 phosphorylates GPR domains to reduce Gα binding, the GPR domain contains two high-affinity and two low-affinity Gαi binding sites, and cytosolic AGS3 can extract Gαi from membranes to disrupt receptor coupling.","evidence":"ITC with purified proteins, yeast two-hybrid, co-IP, in vitro phosphorylation assays, Sf9 membrane reconstitution","pmids":["14530282","12719437","12834360"],"confidence":"High","gaps":["Identity of kinase(s) phosphorylating T602 in vivo not determined","Whether LKB1 phosphorylation is the physiologically dominant regulatory mechanism unclear"]},{"year":2003,"claim":"A direct link between AGS3 and autophagy was established: the GPR domain (Gαi3-binding) promotes macroautophagy while the TPR domain inhibits it, placing AGS3 at an early step before autophagosome formation.","evidence":"Domain truncation mutants, morphometric autophagy analysis, immunofluorescence in HT-29 cells","pmids":["12642577"],"confidence":"Medium","gaps":["Mechanism by which AGS3 promotes early autophagosome formation not defined","Role of specific Gαi subunit selectivity in autophagy not tested"]},{"year":2005,"claim":"AGS3 was shown to regulate spindle orientation and cell fate in mammalian neural progenitors, establishing its first in vivo developmental function: AGS3 silencing shifts divisions from apical-basal to planar, causing premature neuronal differentiation.","evidence":"In utero RNAi in mouse neocortex, spindle angle measurements, cell fate immunofluorescence","pmids":["16009138"],"confidence":"High","gaps":["Whether AGS3 acts through cortical Gαi or through antagonism of LGN in this context was unresolved","Mechanism of cortical recruitment of AGS3 in neural progenitors unclear"]},{"year":2007,"claim":"AGS3 was linked to membrane trafficking: both overexpression and knockdown disrupt trans-Golgi network organization and alter plasma membrane receptor surface expression, without affecting cis/medial Golgi.","evidence":"siRNA knockdown, immunofluorescence of Golgi markers, biotin internalization assay, flow cytometry","pmids":["17991770"],"confidence":"Medium","gaps":["Whether AGS3 acts directly at the TGN or indirectly via Gαi/Gβγ signaling not distinguished","Cargo specificity of AGS3-dependent trafficking unknown"]},{"year":2008,"claim":"The mechanism by which AGS3's GDI activity is reversed was established: Ric-8A (a GEF) forms a transient ternary complex with AGS3·Gαi·GDP, catalyzes GDP release to produce a stable nucleotide-free Ric-8A·Gαi complex, and AGS3 cannot reverse this, ensuring unidirectional Gα activation.","evidence":"Pulldown, gel filtration, ITC, stopped-flow fluorescence with purified proteins","pmids":["18541531"],"confidence":"High","gaps":["Whether Ric-8A acts on AGS3·Gαi complexes in specific cellular compartments not shown","Structural basis of ternary complex not determined"]},{"year":2008,"claim":"The in vivo relevance of AGS3-mediated Gβγ liberation was demonstrated in addiction circuitry: AGS3 upregulation in nucleus accumbens during ethanol abstinence drives ethanol-seeking through Gβγ signaling.","evidence":"Lentiviral shRNA knockdown in rat brain, operant self-administration, pharmacological Gβγ sequestration","pmids":["18719114"],"confidence":"Medium","gaps":["Mechanism triggering AGS3 upregulation during withdrawal not identified","Specificity of the behavioral phenotype to Gβγ vs other AGS3-dependent pathways not fully resolved"]},{"year":2010,"claim":"The autophagy mechanism was refined: AGS3 recruits Gαi3 to LC3-positive membranes to promote autophagy, and the GEF GIV disrupts this complex upon growth factor stimulation, establishing a GDI-GEF toggle controlling autophagy initiation. Separately, USP9X was identified as a deubiquitinase stabilizing AGS3 protein levels, and phosphorylation/Gαi binding were shown to bidirectionally control AGS3 subcellular distribution.","evidence":"Co-IP, pulldown, autophagy morphometry, USP9X knockdown/overexpression, BRET in live cells, immunofluorescence with site-directed mutants","pmids":["21209316","20305814","20716524","20065032"],"confidence":"Medium","gaps":["Whether LC3 interaction is direct or via Gαi3 not resolved","Ubiquitination sites on AGS3 not mapped"]},{"year":2014,"claim":"Global knockout revealed AGS3's role in immune cell chemotaxis: Gpsm1−/− lymphocytes and dendritic cells show impaired chemokine-stimulated migration, calcium flux, and ERK/Akt signaling.","evidence":"Gpsm1−/− mice, chemotaxis assays, calcium flux, phospho-immunoblots in primary cells","pmids":["24573680"],"confidence":"Medium","gaps":["Whether chemotaxis defect reflects Gβγ liberation or Gαi sequestration not distinguished","Redundancy with LGN in immune cells not assessed"]},{"year":2017,"claim":"The apparent paradox of AGS3 in spindle orientation was addressed: unlike LGN, AGS3 is not recruited to the cortex in mouse neural progenitors and cannot rescue LGN loss, despite conserved in vitro binding to NuMA and Gαi, indicating species- and context-specific functional divergence.","evidence":"In utero electroporation, LGN rescue experiments, in vitro binding, spindle angle measurement in mouse cortex","pmids":["28684399"],"confidence":"Medium","gaps":["Whether earlier in utero RNAi results reflect off-target effects or context differences not resolved","Mechanism preventing AGS3 cortical recruitment unclear"]},{"year":2020,"claim":"AGS3's TGN trafficking function was validated in early embryogenesis: AGS3 knockout arrests mouse embryos after the 4-cell stage with impaired E-cadherin delivery to the plasma membrane and dispersed TGN markers, rescued by Gαi1 overexpression.","evidence":"CRISPR/Cas9 knockout in mouse embryos, live imaging of TGN markers, Gαi1 rescue","pmids":["33148610"],"confidence":"Medium","gaps":["Direct mechanism by which AGS3/Gαi1 regulates TGN vesicle budding or sorting not established","Whether Gβγ or Gαi is the operative downstream effector in TGN trafficking unknown"]},{"year":2022,"claim":"A complete signaling axis was defined in macrophages: USP9X stabilizes GPSM1 via K63-deubiquitination; GPSM1 sequesters Gαi3·GDP, elevating cAMP/PKA/CREB signaling that transcribes TNFAIP3, thereby inhibiting TLR4-induced NF-κB and promoting metabolic inflammation.","evidence":"Myeloid-specific GPSM1 KO mice, HFD metabolic phenotyping, ChIP-PCR, mass spectrometry, co-IP","pmids":["36434066"],"confidence":"High","gaps":["Whether Gβγ liberation contributes to the inflammatory phenotype not tested","Ubiquitin ligase targeting GPSM1 for K63 ubiquitination not identified"]},{"year":2023,"claim":"The long-standing question of AGS3 vs LGN in spindle orientation was definitively resolved in epidermis: AGS3 antagonizes LGN by displacing it from the apical cortex, promoting planar/symmetric divisions, while LGN promotes perpendicular/asymmetric divisions; genetic epistasis confirms AGS3 acts through LGN.","evidence":"In vivo mouse epidermal manipulation, live imaging, double-mutant epistasis, clonal lineage tracing","pmids":["37017303"],"confidence":"High","gaps":["Molecular mechanism by which AGS3 displaces LGN from cortex not defined","Whether AGS3 competes directly with LGN for Gαi or acts indirectly unclear"]},{"year":2025,"claim":"The molecular basis for AGS3/LGN functional divergence in spindle orientation was identified: AGS3 cannot form stable hetero-hexameric complexes with NuMA due to differences in ~20 N-terminal residues preceding the TPR domain, and Insc selectively disrupts AGS3/NuMA but not LGN/NuMA complexes.","evidence":"Biochemical reconstitution, gel filtration, pulldown with domain truncations","pmids":["39580365"],"confidence":"Medium","gaps":["Structural determination of AGS3 TPR domain vs LGN TPR domain not achieved","Whether this oligomerization difference fully explains all in vivo context-dependent phenotypes unknown"]},{"year":2025,"claim":"Direct demonstration that AGS3's GDI activity is sufficient to liberate Gβγ signaling was achieved using an optogenetic GPR-based tool (OptoGDI) at the plasma membrane, producing localized PIP3 and triggering macrophage migration without GPCR activation.","evidence":"Optogenetic plasma membrane recruitment, PIP3 biosensor imaging, macrophage migration assay","pmids":["39904370"],"confidence":"Medium","gaps":["Whether endogenous AGS3 produces comparable spatially restricted Gβγ signals not shown","OptoGDI may not recapitulate TPR-domain-dependent regulation of endogenous AGS3"]},{"year":null,"claim":"Key unresolved questions include the identity of the E3 ubiquitin ligase targeting GPSM1, the structural basis for differential GPR motif affinities and their regulation by phosphorylation, the mechanism by which AGS3 displaces LGN from the cortex in epithelia, and whether AGS3 functions primarily through Gαi sequestration or Gβγ liberation in each specific biological context.","evidence":"","pmids":[],"confidence":"Low","gaps":["No E3 ligase for GPSM1 identified","No high-resolution structure of full-length AGS3 or AGS3–Gαi complex","Gαi vs Gβγ effector identity in specific tissues not systematically resolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,2,7,31]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[11,15,27]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[8,17,23]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[12,24]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[16,31]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[5,15]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,9,16,21,26]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[5,15,28]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[12,24]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[10,27]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[21,26]}],"complexes":["AGS3·Gαi·GDP complex","mInsc–AGS3–Par3 complex"],"partners":["GNAI1","GNAI3","RIC8A","USP9X","STK11","INSC","GPSM2","NUMA1"],"other_free_text":[]},"mechanistic_narrative":"GPSM1 (AGS3) is a modular scaffold protein that functions as a receptor-independent guanine nucleotide dissociation inhibitor (GDI) for Gαi/o subunits, thereby liberating free Gβγ for downstream signaling and regulating diverse cellular processes including spindle orientation, autophagy, membrane trafficking, and inflammatory signaling. Its C-terminal GPR (GoLoco) motifs selectively bind GDP-bound Gαi with nanomolar affinity, inhibit GDP release, and compete with Gβγ for Gαi binding, while its N-terminal TPR repeats mediate interactions with partners such as mInsc and NuMA; unlike the paralog LGN, AGS3 cannot form stable higher-order NuMA oligomeric complexes required for cortical force generation, and instead antagonizes LGN-dependent perpendicular divisions in epithelia to promote symmetric cell fates [PMID:11042168, PMID:14530282, PMID:37017303, PMID:39580365]. AGS3's GDI activity is counteracted by the GEF Ric-8A, which forms a transient ternary complex to catalyze unidirectional Gα activation, and is regulated by LKB1-mediated phosphorylation of the GPR domain and USP9X-mediated deubiquitination that stabilizes AGS3 protein levels [PMID:18541531, PMID:12719437, PMID:36434066]. In macrophages, GPSM1 stabilization promotes metabolic inflammation through the Gαi3/cAMP/PKA/CREB axis controlling NF-κB signaling, and drives M2 polarization via MEIS3-dependent CSF1 expression; in neurons, AGS3 upregulation during drug withdrawal underlies cAMP superactivation and drug-seeking behavior [PMID:36434066, PMID:30, PMID:19549762, PMID:18719114]."},"prefetch_data":{"uniprot":{"accession":"Q86YR5","full_name":"G-protein-signaling modulator 1","aliases":["Activator of G-protein signaling 3"],"length_aa":675,"mass_kda":74.5,"function":"Guanine nucleotide dissociation inhibitor (GDI) which functions as a receptor-independent activator of heterotrimeric G-protein signaling. Keeps G(i/o) alpha subunit in its GDP-bound form thus uncoupling heterotrimeric G-proteins signaling from G protein-coupled receptors. Controls spindle orientation and asymmetric cell fate of cerebral cortical progenitors. May also be involved in macroautophagy in intestinal cells. May play a role in drug addiction","subcellular_location":"Cytoplasm, cytosol; Endoplasmic reticulum membrane; Golgi apparatus membrane; Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q86YR5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GPSM1","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/GPSM1","total_profiled":1310},"omim":[{"mim_id":"616919","title":"FERM AND PDZ DOMAINS-CONTAINING PROTEIN 1; FRMPD1","url":"https://www.omim.org/entry/616919"},{"mim_id":"610668","title":"INSC SPINDLE ORIENTATION ADAPTOR PROTEIN; INSC","url":"https://www.omim.org/entry/610668"},{"mim_id":"609491","title":"G PROTEIN SIGNALING MODULATOR 1; GPSM1","url":"https://www.omim.org/entry/609491"},{"mim_id":"609245","title":"G PROTEIN SIGNALING MODULATOR 2; GPSM2","url":"https://www.omim.org/entry/609245"},{"mim_id":"266600","title":"INFLAMMATORY BOWEL DISEASE (CROHN DISEASE) 1; IBD1","url":"https://www.omim.org/entry/266600"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Golgi apparatus","reliability":"Supported"},{"location":"Nucleoplasm","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":105.6}],"url":"https://www.proteinatlas.org/search/GPSM1"},"hgnc":{"alias_symbol":["AGS3","DKFZP727I051"],"prev_symbol":[]},"alphafold":{"accession":"Q86YR5","domains":[{"cath_id":"1.25.40.10","chopping":"285-389_632-638","consensus_level":"medium","plddt":86.3621,"start":285,"end":638}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q86YR5","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q86YR5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q86YR5-F1-predicted_aligned_error_v6.png","plddt_mean":67.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GPSM1","jax_strain_url":"https://www.jax.org/strain/search?query=GPSM1"},"sequence":{"accession":"Q86YR5","fasta_url":"https://rest.uniprot.org/uniprotkb/Q86YR5.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q86YR5/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q86YR5"}},"corpus_meta":[{"pmid":"16009138","id":"PMC_16009138","title":"G protein betagamma subunits and AGS3 control spindle orientation and asymmetric cell fate of cerebral cortical progenitors.","date":"2005","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/16009138","citation_count":229,"is_preprint":false},{"pmid":"12814548","id":"PMC_12814548","title":"Asymmetrically distributed C. elegans homologs of AGS3/PINS control spindle position in the early embryo.","date":"2003","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/12814548","citation_count":198,"is_preprint":false},{"pmid":"11042168","id":"PMC_11042168","title":"Selective interaction of AGS3 with G-proteins and the influence of AGS3 on the activation state of G-proteins.","date":"2001","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11042168","citation_count":132,"is_preprint":false},{"pmid":"10969064","id":"PMC_10969064","title":"Stabilization of the GDP-bound conformation of Gialpha by a peptide derived from the G-protein regulatory motif of AGS3.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10969064","citation_count":121,"is_preprint":false},{"pmid":"11832491","id":"PMC_11832491","title":"Expression analysis and subcellular distribution of the two G-protein regulators AGS3 and LGN indicate distinct functionality. Localization of LGN to the midbody during cytokinesis.","date":"2002","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11832491","citation_count":100,"is_preprint":false},{"pmid":"11024022","id":"PMC_11024022","title":"AGS3 inhibits GDP dissociation from galpha subunits of the Gi family and rhodopsin-dependent activation of transducin.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11024022","citation_count":98,"is_preprint":false},{"pmid":"16531086","id":"PMC_16531086","title":"AGS3, an alpha(1-3)glucan synthase gene family member of Aspergillus fumigatus, modulates mycelium growth in the lung of experimentally infected mice.","date":"2006","source":"Fungal genetics and biology : FG & B","url":"https://pubmed.ncbi.nlm.nih.gov/16531086","citation_count":88,"is_preprint":false},{"pmid":"21209316","id":"PMC_21209316","title":"A GDI (AGS3) and a GEF (GIV) regulate autophagy by balancing G protein activity and growth factor signals.","date":"2011","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/21209316","citation_count":87,"is_preprint":false},{"pmid":"18719114","id":"PMC_18719114","title":"Nucleus accumbens AGS3 expression drives ethanol seeking through G betagamma.","date":"2008","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/18719114","citation_count":69,"is_preprint":false},{"pmid":"12642577","id":"PMC_12642577","title":"The G-protein regulator AGS3 controls an early event during macroautophagy in human intestinal HT-29 cells.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12642577","citation_count":64,"is_preprint":false},{"pmid":"18541531","id":"PMC_18541531","title":"Ric-8A catalyzes guanine nucleotide exchange on G alphai1 bound to the GPR/GoLoco exchange inhibitor AGS3.","date":"2008","source":"The 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POR","url":"https://pubmed.ncbi.nlm.nih.gov/34257610","citation_count":8,"is_preprint":false},{"pmid":"36138114","id":"PMC_36138114","title":"Investigation of bioactivity of unsaturated oligo‑galacturonic acids produced from apple waste by Alcaligenes faecalis AGS3 and Paenibacillus polymyxa S4 Pectinases.","date":"2022","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/36138114","citation_count":5,"is_preprint":false},{"pmid":"39855604","id":"PMC_39855604","title":"GPSM1 interacts and cooperates with MMP19 to promote proliferation and EMT in colorectal cancer cells.","date":"2025","source":"Biochimica et biophysica acta. Molecular cell research","url":"https://pubmed.ncbi.nlm.nih.gov/39855604","citation_count":3,"is_preprint":false},{"pmid":"33148610","id":"PMC_33148610","title":"AGS3-dependent trans-Golgi network membrane trafficking is essential for compaction in mouse embryos.","date":"2020","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/33148610","citation_count":3,"is_preprint":false},{"pmid":"33172018","id":"PMC_33172018","title":"AGS3 and Gαi3 Are Concomitantly Upregulated as Part of the Spindle Orientation Complex during Differentiation of Human Neural Progenitor Cells.","date":"2020","source":"Molecules (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/33172018","citation_count":3,"is_preprint":false},{"pmid":"39904370","id":"PMC_39904370","title":"AGS3-based optogenetic GDI induces GPCR-independent Gβγ signalling and macrophage migration.","date":"2025","source":"Open biology","url":"https://pubmed.ncbi.nlm.nih.gov/39904370","citation_count":2,"is_preprint":false},{"pmid":"24058824","id":"PMC_24058824","title":"The G protein regulator AGS-3 allows C. elegans to alter behaviors in response to food deprivation.","date":"2012","source":"Worm","url":"https://pubmed.ncbi.nlm.nih.gov/24058824","citation_count":1,"is_preprint":false},{"pmid":"41296728","id":"PMC_41296728","title":"Myeloid GPSM1 regulates atherosclerosis progression by governing monocyte and macrophage activation and chemotaxis.","date":"2025","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/41296728","citation_count":0,"is_preprint":false},{"pmid":"39580365","id":"PMC_39580365","title":"Molecular insights into AGS3's role in spindle orientation: a biochemical perspective.","date":"2025","source":"Journal of molecular cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/39580365","citation_count":0,"is_preprint":false},{"pmid":"38895415","id":"PMC_38895415","title":"AGS3-based optogenetic GDI induces GPCR-independent Gβγ signaling and macrophage migration.","date":"2024","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/38895415","citation_count":0,"is_preprint":false},{"pmid":"20684276","id":"PMC_20684276","title":"[The effect of AGS3 on the I(A) of newborn rat prefrontal cortical neurons pretreated by chronic morphine].","date":"2010","source":"Zhongguo ying yong sheng li xue za zhi = Zhongguo yingyong shenglixue zazhi = Chinese journal of applied physiology","url":"https://pubmed.ncbi.nlm.nih.gov/20684276","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.07.02.601660","title":"Molecular Insights into AGS3’s Role in Spindle Orientation: A Biochemical Perspective","date":"2024-07-03","source":"bioRxiv","url":"https://doi.org/10.1101/2024.07.02.601660","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":26733,"output_tokens":7815,"usd":0.098712},"stage2":{"model":"claude-opus-4-6","input_tokens":11930,"output_tokens":4441,"usd":0.256012},"total_usd":0.354724,"stage1_batch_id":"msgbatch_01DzrsgVgYngY1hvM3DU1yF2","stage2_batch_id":"msgbatch_01KA9b7iRzKFdhoBUT7vCvSe","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2001,\n      \"finding\": \"AGS3's C-terminal domain contains four GPR (G-protein regulatory) motifs that selectively bind the GDP-bound conformation of Gαi (not GTPγS-bound), compete with Gβγ for Gαi(GDP) binding, and act as a guanine nucleotide dissociation inhibitor (GDI), blocking GTPγS binding to Gαi. AGS3 co-immunoprecipitates with Gαi3 from cell and tissue lysates.\",\n      \"method\": \"Co-immunoprecipitation, GST pulldown with purified Gα subunits, GTPγS binding assays, immunofluorescence/confocal imaging\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro biochemical assays with purified proteins replicated across multiple methods; foundational paper with >130 citations\",\n      \"pmids\": [\"11042168\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"A consensus GPR peptide from AGS3 stabilizes the GDP-bound conformation of Gαi (functions as GDI), inhibits GTPγS binding to Gαi1/2, and blocks receptor coupling to Gαiβγ, indicating that AGS3-GPR-stabilized Gαi(GDP) is not recognized by GPCRs.\",\n      \"method\": \"In vitro GTPγS binding assays, receptor-G protein coupling assays with purified proteins and peptides\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro with purified proteins and synthetic peptides, multiple assays\",\n      \"pmids\": [\"10969064\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"The AGS3 GPR domain inhibits GDP dissociation from Gαi and rhodopsin-stimulated GDP release from Gαt, acting as a GDP dissociation inhibitor. The full-length GPR domain (residues 463–650) is ~30-fold more potent than a two-GPR-motif fragment, and does not alter the catalytic rate of GTP hydrolysis by Gαt.\",\n      \"method\": \"In vitro kinetic assays of GTPγS binding, GDP release (stopped-flow/fluorescence), steady-state GTP hydrolysis with purified Gα subunits\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — rigorous in vitro reconstitution with purified proteins and quantitative kinetics\",\n      \"pmids\": [\"11024022\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"AGS3 exists in two forms: a full-length brain-enriched form (AGS3-LONG, 650 aa) and a heart-enriched truncated form (AGS3-SHORT, starting at Met495) that lacks TPR domains but retains GPR motifs. Both forms selectively bind Gαi1/2/3 in GDP-bound conformation and inhibit GTPγS binding, but they differ in subcellular distribution.\",\n      \"method\": \"cDNA library screening, RNase protection, GST pulldown with purified Gα, GTPγS binding assay, immunofluorescence, subcellular fractionation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods identifying a novel isoform with distinct biochemical properties\",\n      \"pmids\": [\"11278352\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"LGN (but not AGS3) translocates from the nucleus to the midbody during cytokinesis in PC12 and COS7 cells, suggesting a role for LGN/G-proteins in cytokinesis; AGS3 and LGN have distinct subcellular distributions regulated by cell cycle and external stimuli.\",\n      \"method\": \"Immunocytochemistry, confocal microscopy, cell cycle analysis in dividing cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct localization by imaging with cell-cycle correlation, single lab\",\n      \"pmids\": [\"11832491\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"AGS3 localizes to compartments compatible with autophagosome formation and its C-terminal GPR domain (which binds Gαi3) promotes macroautophagy, while its N-terminal domain (non-Gαi3-interacting) inhibits autophagy; AGS3 acts at an early event in the autophagic pathway prior to autophagosome formation.\",\n      \"method\": \"Immunofluorescence localization, expression of domain truncation mutants, biochemical and morphometric analysis of autophagic flux in HT-29 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — domain dissection with functional autophagy readout in cell lines, single lab\",\n      \"pmids\": [\"12642577\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"AGS3 interacts with the serine/threonine kinase LKB1; LKB1 immunoprecipitates phosphorylate the GPR domains of AGS3, and phosphorylation within the GPR motif reduces binding to Gα, suggesting that LKB1-mediated phosphorylation of GPR domains is a regulatory mechanism for AGS3–G-protein interactions.\",\n      \"method\": \"Yeast two-hybrid screen, co-immunoprecipitation from mammalian cells/brain lysate, in vitro phosphorylation assay, GPR peptide competition\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — multiple assays identifying kinase-substrate relationship and functional consequence on G-protein binding, single lab\",\n      \"pmids\": [\"12719437\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"AGS3-C (C-terminal domain) possesses two high-affinity (Kd ~20 nM) and two low-affinity (Kd ~300 nM) binding sites for Gαi1; individual GPR motif peptides bind with Kd 1–8 µM. Residues flanking the GPR core strongly potentiate binding affinity and GDI activity. GPR3 alone lacks GDI activity but gains it with flanking residues.\",\n      \"method\": \"Isothermal titration calorimetry (ITC), fluorescent GTP analog binding assay with purified proteins and peptides\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — quantitative thermodynamic characterization by ITC with purified proteins\",\n      \"pmids\": [\"14530282\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Cytosolic (not membrane-associated) AGS3 can interact with Gαi subunits and disrupt receptor-G protein coupling; cytosolic AGS3 removes Gαi subunits from the membrane and sequesters them in the cytosol, as shown in an Sf9 membrane reconstitution system.\",\n      \"method\": \"Sf9 membrane-based receptor-G protein coupling reconstitution, GST pulldown, immunoblotting of membrane/cytosolic fractions\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — reconstitution system with defined fractions, single lab\",\n      \"pmids\": [\"12834360\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"AGS3-SHORT blocks adenylyl cyclase sensitization that normally follows prolonged Gαi-coupled receptor activation; this effect requires intact G-protein binding by AGS3, and is correlated with AGS3 stabilizing Gαi3 in the membrane and slowing Gαi3 decay.\",\n      \"method\": \"cAMP measurement in CHO cells, immunoblot of membrane Gαi3, G-protein binding mutant controls\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — cell-based functional assay with mutant controls, single lab\",\n      \"pmids\": [\"14726514\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"AGS3 (and Gβγ) regulate mitotic spindle orientation in neural progenitors of the developing neocortex; silencing AGS3 shifts spindle orientation from apical-basal to planar divisions, causing hyperdifferentiation of progenitors due to both daughter cells adopting a neuronal fate.\",\n      \"method\": \"In utero RNA interference in mouse neocortex, spindle angle measurements, cell fate analysis by immunofluorescence\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean loss-of-function with defined cellular phenotype (spindle orientation + cell fate), highly cited foundational paper\",\n      \"pmids\": [\"16009138\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Human Inscuteable (mInsc) proteins bind to both LGN and AGS3 through their TPR domains, and to Par3/Par3β; coexpression of mInsc bridges LGN and Par3 (which do not interact directly), indicating mInsc is an adaptor linking Pins homologs to the Par polarity complex.\",\n      \"method\": \"Co-immunoprecipitation from transfected mammalian cells\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — co-IP from transfected cells, single lab, single method\",\n      \"pmids\": [\"16458856\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"AGS3 overexpression alters surface expression of a subset of plasma membrane receptors/channels and disrupts trans-Golgi network (TGN)-associated cargo localization without affecting cis- or medial-Golgi; AGS3 knockdown similarly disperses TGN markers, implicating AGS3 in protein trafficking along the TGN/plasma membrane/endosome loop.\",\n      \"method\": \"Biotin-based internalization assay, immunofluorescence of Golgi markers, siRNA knockdown, flow cytometry of surface proteins\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — gain- and loss-of-function convergent results for TGN trafficking, single lab\",\n      \"pmids\": [\"17991770\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Ric-8A (a GEF) catalyzes rapid GDP release from the AGS3-C:Gαi1·GDP complex by forming a transient ternary complex; subsequent dissociation of AGS3 and GDP yields a stable nucleotide-free Ric-8A·Gαi1 complex that proceeds to Gαi1·GTP upon GTP addition. AGS3 cannot reverse the Ric-8A·Gαi1 complex, ensuring unidirectional Gα activation.\",\n      \"method\": \"Pulldown assays, gel filtration, isothermal titration calorimetry, stopped-flow fluorescence spectroscopy with purified proteins\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple orthogonal in vitro methods with purified proteins establishing ternary complex mechanism\",\n      \"pmids\": [\"18541531\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"AGS3 upregulation in rat nucleus accumbens core during ethanol abstinence drives ethanol-seeking behavior through Gβγ signaling; AGS3 knockdown or Gβγ sequestration (but not Gαi knockdown) reduced ethanol seeking, placing AGS3 upstream of Gβγ in this behavioral circuit.\",\n      \"method\": \"Lentiviral shRNA knockdown in rat brain, operant ethanol self-administration model, pharmacological Gβγ sequestration, Gαi knockdown\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis (knockdown) + pharmacological dissection in vivo, single lab\",\n      \"pmids\": [\"18719114\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"AGS3 interacts with LC3 (autophagosome marker), recruits Gαi3 to LC3-positive membranes upon starvation, and promotes autophagy by acting as GDI for Gαi3. Upon growth factor stimulation, GIV (a GEF for Gαi3) disrupts the Gαi3–AGS3 complex, releasing Gαi3 from LC3-positive membranes and inhibiting autophagy.\",\n      \"method\": \"Protein-protein interaction assays (co-IP, pulldown), G protein enzymology, morphological analysis of autophagy (LC3 puncta), starvation/growth factor conditions\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods including biochemistry and cell biology, direct mechanistic pathway established\",\n      \"pmids\": [\"21209316\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"α2-adrenergic and μ-opioid receptor activation reduces AGS3–Gαi1 BRET signal by >30% (pertussis toxin- and RGS4-sensitive), indicating that GPCR activation dissociates the AGS3·Gαi complex at the cell cortex. AGS3 also shows BRET with GPCRs, suggesting it is part of a larger receptor signaling complex.\",\n      \"method\": \"Bioluminescence resonance energy transfer (BRET) in live mammalian cells, pharmacological and genetic controls (pertussis toxin, RGS4, GRK2-ct)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — BRET in living cells with multiple controls, single lab\",\n      \"pmids\": [\"20716524\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"AGS3 enters the aggresome pathway; Gαi rescues AGS3 from the aggresome, whereas mInsc augments aggresome-like distribution. TPR domain integrity and a specific nonsynonymous SNP regulate AGS3 aggresome entry, revealing that Gαi and mInsc bidirectionally control AGS3 subcellular distribution under cellular stress.\",\n      \"method\": \"Immunofluorescence, confocal microscopy, co-expression with Gαi/mInsc, TPR domain mutant and SNP analysis in COS7 cells\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — domain mutagenesis + protein binding partners controlling localization, single lab\",\n      \"pmids\": [\"20065032\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"AGS3 interacts with the deubiquitinating enzyme USP9x (interaction mediated through AGS3's C-terminal GPR domain); USP9x knockdown reduces AGS3 levels, while USP9x or its deubiquitinating domain UCH overexpression increases AGS3, indicating USP9x stabilizes a subpopulation of AGS3 through deubiquitination.\",\n      \"method\": \"Co-immunoprecipitation, USP9x knockdown, overexpression of catalytic domain mutants, immunofluorescence of Golgi markers\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — interaction + functional consequence on protein levels with catalytic mutant control, single lab\",\n      \"pmids\": [\"20305814\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Morphine withdrawal-induced cAMP superactivation requires AGS3 upregulation; elevated AGS3 binds Gαi and prevents its inhibition of adenylyl cyclase, while withdrawal-induced cAMP/PKA activates phospholipase C and εPKC to further stimulate AC5 and AC7.\",\n      \"method\": \"cAMP measurement in nucleus accumbens/striatal neurons, AGS3 knockdown, pharmacological dissection of Gβγ vs Gαi involvement, AC5/AC7 identification\",\n      \"journal\": \"Molecular pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — cell-based functional dissection with AGS3 knockdown and downstream pathway identification, single lab\",\n      \"pmids\": [\"19549762\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In C. elegans, AGS-3 (GPSM1 ortholog) activates Gαo signaling in ASH chemosensory neurons in response to food deprivation; genetic epistasis shows AGS-3 and the GEF RIC-8 act in ASH in a mutually dependent fashion to activate Gαo, requiring the GPR domain–Gαo interaction, and Gαo-GTP is the downstream signaling molecule.\",\n      \"method\": \"Genetic epistasis analysis in C. elegans (double mutants, tissue-specific rescue), behavioral assays (octanol aversion delay), biochemical fractionation\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with multiple alleles and tissue-specific experiments establishing pathway order\",\n      \"pmids\": [\"21832186\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"AGS3 is required for proper chemokine receptor signaling in leukocytes; AGS3-null B and T lymphocytes and dendritic cells show defects in chemotaxis, reduced chemokine-stimulated calcium mobilization, and altered ERK and Akt activation.\",\n      \"method\": \"Characterization of Gpsm1-/- mice: chemotaxis assays, calcium flux measurements, ERK/Akt phosphorylation immunoblots in primary immune cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean knockout with defined signaling phenotypes in primary cells, single lab\",\n      \"pmids\": [\"24573680\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"AGS3 is not recruited to the cell cortex in mouse neural progenitors and does not rescue LGN loss of function in oriented divisions; despite conserved in vitro interactions with NuMA and Gαi, AGS3 lacks spindle orientation function in vivo, revealing that species-specific modulation of interactions distinguishes LGN and AGS3 function.\",\n      \"method\": \"In utero electroporation (mouse neocortex), LGN rescue experiments, in vitro binding assays, spindle angle measurements\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function + rescue experiments in vivo combined with in vitro binding, single lab\",\n      \"pmids\": [\"28684399\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Phosphorylation of AGS3 at a single threonine (T602) in the GPR domain regulates its subcellular distribution: AGS3-T602A localizes to cytosolic puncta instead of cortical/diffuse distribution, and this punctate localization is rescued by co-expression of Gαi or Gαo but not Gαs or Gαq, indicating that GPR phosphorylation controls G-protein-dependent subcellular positioning of AGS3.\",\n      \"method\": \"Site-directed mutagenesis, immunofluorescence in COS7 cells, alkaline phosphatase treatment + SDS-PAGE gel shift, co-expression with Gα subunits\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mutagenesis + rescue experiments linking specific phosphosite to subcellular distribution, single lab\",\n      \"pmids\": [\"30404823\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"AGS3 regulates E-cadherin (Cdh1) transport to the plasma membrane via the trans-Golgi network in early mouse embryos; AGS3 knockout arrests embryo development after the 4-cell stage with decreased membrane Cdh1 accumulation and dispersal of TGN markers; Gαi1 overexpression rescues AGS3-overexpression phenotype, indicating Gαi1 acts downstream of AGS3 in TGN-to-membrane trafficking.\",\n      \"method\": \"CRISPR/Cas9 knockout in mouse embryos, fluorescent protein tagging of TGN markers (TGN46, TMED7), live imaging, Gαi1 rescue experiment\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with rescue and live imaging in embryos, single lab\",\n      \"pmids\": [\"33148610\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"AGS3 and Gαi3 are co-upregulated as part of the spindle orientation complex during human neural progenitor cell differentiation; co-immunoprecipitation shows AGS3 preferentially interacts with Gαi3 (not Gαi1/2) in differentiated cells, and this interaction is suppressed by GTPγS and pertussis toxin, indicating AGS3 recognizes the same Gα binding site as GPCRs.\",\n      \"method\": \"Co-immunoprecipitation, western blot from differentiating neural progenitor cell lines, GTPγS and pertussis toxin treatments\",\n      \"journal\": \"Molecules\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — co-IP in cell lines with pharmacological controls, single lab\",\n      \"pmids\": [\"33172018\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Myeloid GPSM1 promotes metabolic inflammation; GPSM1 deficiency in macrophages mainly promotes TNFAIP3 transcription via the Gαi3/cAMP/PKA/CREB axis, thereby inhibiting TLR4-induced NF-κB signaling. USP9X prevents GPSM1 degradation through K63-polyubiquitination stabilization.\",\n      \"method\": \"Myeloid-specific GPSM1 knockout mice, high-fat diet metabolic phenotyping, ChIP-PCR, mass spectrometry, co-immunoprecipitation, macrophage signaling assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vivo KO + multiple mechanistic biochemical assays establishing Gαi3/cAMP/PKA/CREB→TNFAIP3 pathway\",\n      \"pmids\": [\"36434066\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"AGS3 negatively regulates LGN to balance spindle orientation in mammalian epidermis; AGS3 overexpression displaces LGN from the apical cortex and increases planar divisions, AGS3 loss prolongs cortical LGN localization and biases toward perpendicular divisions; genetic epistasis in double mutants confirms AGS3 acts through LGN. Clonal lineage tracing shows AGS3 promotes symmetric fates and LGN promotes asymmetric fates.\",\n      \"method\": \"In vivo mouse epidermal genetic manipulation, static and ex vivo live imaging, genetic epistasis (double mutant analysis), clonal lineage tracing\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple in vivo approaches (imaging, epistasis, lineage tracing) establishing AGS3 as negative regulator of LGN-dependent spindle orientation\",\n      \"pmids\": [\"37017303\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"GPSM1 deficiency in POMC neurons protects against diet-induced obesity by enhancing autophagy and improving leptin sensitivity through PI3K/AKT/mTOR signaling, increasing POMC/α-MSH production and sympathetic innervation of brown adipose tissue.\",\n      \"method\": \"POMC-neuron-specific GPSM1 knockout mice, high-fat diet metabolic phenotyping, immunofluorescence, immunohistochemistry, molecular pathway analysis (PI3K/AKT/mTOR)\",\n      \"journal\": \"Molecular metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific KO with mechanistic pathway analysis in vivo, single lab\",\n      \"pmids\": [\"37979657\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"AGS3 binds NuMA and Gαi3·GDP in vitro similarly to LGN, but cannot form stable hetero-hexamers or higher-order oligomeric complexes with NuMA that are required for spindle orientation. The ~20 N-terminal residues preceding the conserved TPR motifs account for this difference. Insc disrupts the AGS3/NuMA oligomeric complex but not the LGN/NuMA complex, further distinguishing their spindle orientation functions.\",\n      \"method\": \"Biochemical reconstitution, gel filtration, pulldown assays, structural characterization of AGS3 vs LGN domain truncations\",\n      \"journal\": \"Journal of molecular cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro reconstitution with domain mutants establishing molecular basis for AGS3/LGN functional difference, single lab\",\n      \"pmids\": [\"39580365\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"GPSM1 is stabilized by USP9X via prevention of K63-polyubiquitination-dependent degradation; GPSM1 stabilization leads to MEIS3 nuclear translocation, activating CSF1 (macrophage colony-stimulating factor) expression, driving M2 macrophage polarization and anti-PD-1 resistance in colorectal cancer.\",\n      \"method\": \"ChIP-PCR, mass spectrometry, co-immunoprecipitation, single-cell RNA sequencing, orthotopic CRC model, macrophage polarization assays\",\n      \"journal\": \"Journal for immunotherapy of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple biochemical methods establishing ubiquitination mechanism and downstream transcriptional pathway, single lab\",\n      \"pmids\": [\"40010765\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Plasma membrane recruitment of an optogenetic tool based on AGS3's GPR motif (OptoGDI) releases Gβγ in living cells in a GPCR-independent manner, generating localized PIP3 and triggering macrophage migration, directly demonstrating that AGS3-mediated GDI activity on Gαi is sufficient to produce free Gβγ signaling.\",\n      \"method\": \"Optogenetics in living cells, PIP3 biosensor imaging, macrophage migration assay\",\n      \"journal\": \"Open biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — optogenetic gain-of-function in live cells with functional readout, novel approach\",\n      \"pmids\": [\"39904370\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GPSM1/AGS3 is a modular scaffold protein with N-terminal TPR repeats and C-terminal GPR (GoLoco) motifs that functions primarily as a guanine nucleotide dissociation inhibitor (GDI) for Gαi/o subunits: its GPR domain selectively binds GDP-bound Gαi, stabilizes this conformation, competes with Gβγ for Gαi(GDP) binding, and thereby liberates free Gβγ for downstream signaling; its GDI activity is antagonized by the GEF Ric-8A (which can displace AGS3 from Gαi and drive Gα activation) and is regulated by LKB1-mediated phosphorylation of the GPR domain and by USP9X-mediated deubiquitination; subcellular distribution of AGS3 is dynamically controlled by Gαi binding and phosphorylation of T602; through these mechanisms AGS3 regulates spindle orientation (antagonizing LGN in epithelia), autophagy initiation (recruiting Gαi3 to LC3-positive membranes), trans-Golgi network trafficking, chemokine receptor signaling in immune cells, and neuronal cAMP homeostasis during drug withdrawal.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"GPSM1 (AGS3) is a modular scaffold protein that functions as a receptor-independent guanine nucleotide dissociation inhibitor (GDI) for Gαi/o subunits, thereby liberating free Gβγ for downstream signaling and regulating diverse cellular processes including spindle orientation, autophagy, membrane trafficking, and inflammatory signaling. Its C-terminal GPR (GoLoco) motifs selectively bind GDP-bound Gαi with nanomolar affinity, inhibit GDP release, and compete with Gβγ for Gαi binding, while its N-terminal TPR repeats mediate interactions with partners such as mInsc and NuMA; unlike the paralog LGN, AGS3 cannot form stable higher-order NuMA oligomeric complexes required for cortical force generation, and instead antagonizes LGN-dependent perpendicular divisions in epithelia to promote symmetric cell fates [PMID:11042168, PMID:14530282, PMID:37017303, PMID:39580365]. AGS3's GDI activity is counteracted by the GEF Ric-8A, which forms a transient ternary complex to catalyze unidirectional Gα activation, and is regulated by LKB1-mediated phosphorylation of the GPR domain and USP9X-mediated deubiquitination that stabilizes AGS3 protein levels [PMID:18541531, PMID:12719437, PMID:36434066]. In macrophages, GPSM1 stabilization promotes metabolic inflammation through the Gαi3/cAMP/PKA/CREB axis controlling NF-κB signaling, and drives M2 polarization via MEIS3-dependent CSF1 expression; in neurons, AGS3 upregulation during drug withdrawal underlies cAMP superactivation and drug-seeking behavior [PMID:36434066, PMID:30, PMID:19549762, PMID:18719114].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"The fundamental question of how AGS3 acts on G proteins was resolved: GPR motifs stabilize Gαi in the GDP-bound state by inhibiting nucleotide exchange, establishing AGS3 as a GDI rather than a GEF or GAP, and showing that GPR-bound Gαi·GDP is not recognized by GPCRs.\",\n      \"evidence\": \"In vitro GTP γS binding, GDP release kinetics, and receptor-G protein coupling assays with purified proteins and synthetic peptides\",\n      \"pmids\": [\"10969064\", \"11024022\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of GPR–Gαi interaction at atomic resolution not yet determined\", \"Relative contribution of individual GPR motifs to GDI activity in vivo unknown\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"The selectivity and cellular context of AGS3–Gα interaction was established: four GPR motifs selectively bind GDP-Gαi (not GTP-bound), compete with Gβγ, and co-immunoprecipitate with Gαi3 from tissues; a brain-enriched long isoform and heart-enriched short isoform with distinct distributions were identified.\",\n      \"evidence\": \"Co-IP from cell/tissue lysates, GST pulldown, GTPγS binding assays, cDNA cloning, RNase protection assays\",\n      \"pmids\": [\"11042168\", \"11278352\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional distinction between long and short isoforms in vivo not established\", \"Tissue-specific regulation of isoform expression unknown\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Multiple regulatory inputs on AGS3 were discovered simultaneously: LKB1 phosphorylates GPR domains to reduce Gα binding, the GPR domain contains two high-affinity and two low-affinity Gαi binding sites, and cytosolic AGS3 can extract Gαi from membranes to disrupt receptor coupling.\",\n      \"evidence\": \"ITC with purified proteins, yeast two-hybrid, co-IP, in vitro phosphorylation assays, Sf9 membrane reconstitution\",\n      \"pmids\": [\"14530282\", \"12719437\", \"12834360\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of kinase(s) phosphorylating T602 in vivo not determined\", \"Whether LKB1 phosphorylation is the physiologically dominant regulatory mechanism unclear\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"A direct link between AGS3 and autophagy was established: the GPR domain (Gαi3-binding) promotes macroautophagy while the TPR domain inhibits it, placing AGS3 at an early step before autophagosome formation.\",\n      \"evidence\": \"Domain truncation mutants, morphometric autophagy analysis, immunofluorescence in HT-29 cells\",\n      \"pmids\": [\"12642577\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which AGS3 promotes early autophagosome formation not defined\", \"Role of specific Gαi subunit selectivity in autophagy not tested\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"AGS3 was shown to regulate spindle orientation and cell fate in mammalian neural progenitors, establishing its first in vivo developmental function: AGS3 silencing shifts divisions from apical-basal to planar, causing premature neuronal differentiation.\",\n      \"evidence\": \"In utero RNAi in mouse neocortex, spindle angle measurements, cell fate immunofluorescence\",\n      \"pmids\": [\"16009138\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether AGS3 acts through cortical Gαi or through antagonism of LGN in this context was unresolved\", \"Mechanism of cortical recruitment of AGS3 in neural progenitors unclear\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"AGS3 was linked to membrane trafficking: both overexpression and knockdown disrupt trans-Golgi network organization and alter plasma membrane receptor surface expression, without affecting cis/medial Golgi.\",\n      \"evidence\": \"siRNA knockdown, immunofluorescence of Golgi markers, biotin internalization assay, flow cytometry\",\n      \"pmids\": [\"17991770\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether AGS3 acts directly at the TGN or indirectly via Gαi/Gβγ signaling not distinguished\", \"Cargo specificity of AGS3-dependent trafficking unknown\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"The mechanism by which AGS3's GDI activity is reversed was established: Ric-8A (a GEF) forms a transient ternary complex with AGS3·Gαi·GDP, catalyzes GDP release to produce a stable nucleotide-free Ric-8A·Gαi complex, and AGS3 cannot reverse this, ensuring unidirectional Gα activation.\",\n      \"evidence\": \"Pulldown, gel filtration, ITC, stopped-flow fluorescence with purified proteins\",\n      \"pmids\": [\"18541531\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Ric-8A acts on AGS3·Gαi complexes in specific cellular compartments not shown\", \"Structural basis of ternary complex not determined\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"The in vivo relevance of AGS3-mediated Gβγ liberation was demonstrated in addiction circuitry: AGS3 upregulation in nucleus accumbens during ethanol abstinence drives ethanol-seeking through Gβγ signaling.\",\n      \"evidence\": \"Lentiviral shRNA knockdown in rat brain, operant self-administration, pharmacological Gβγ sequestration\",\n      \"pmids\": [\"18719114\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism triggering AGS3 upregulation during withdrawal not identified\", \"Specificity of the behavioral phenotype to Gβγ vs other AGS3-dependent pathways not fully resolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"The autophagy mechanism was refined: AGS3 recruits Gαi3 to LC3-positive membranes to promote autophagy, and the GEF GIV disrupts this complex upon growth factor stimulation, establishing a GDI-GEF toggle controlling autophagy initiation. Separately, USP9X was identified as a deubiquitinase stabilizing AGS3 protein levels, and phosphorylation/Gαi binding were shown to bidirectionally control AGS3 subcellular distribution.\",\n      \"evidence\": \"Co-IP, pulldown, autophagy morphometry, USP9X knockdown/overexpression, BRET in live cells, immunofluorescence with site-directed mutants\",\n      \"pmids\": [\"21209316\", \"20305814\", \"20716524\", \"20065032\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether LC3 interaction is direct or via Gαi3 not resolved\", \"Ubiquitination sites on AGS3 not mapped\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Global knockout revealed AGS3's role in immune cell chemotaxis: Gpsm1−/− lymphocytes and dendritic cells show impaired chemokine-stimulated migration, calcium flux, and ERK/Akt signaling.\",\n      \"evidence\": \"Gpsm1−/− mice, chemotaxis assays, calcium flux, phospho-immunoblots in primary cells\",\n      \"pmids\": [\"24573680\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether chemotaxis defect reflects Gβγ liberation or Gαi sequestration not distinguished\", \"Redundancy with LGN in immune cells not assessed\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"The apparent paradox of AGS3 in spindle orientation was addressed: unlike LGN, AGS3 is not recruited to the cortex in mouse neural progenitors and cannot rescue LGN loss, despite conserved in vitro binding to NuMA and Gαi, indicating species- and context-specific functional divergence.\",\n      \"evidence\": \"In utero electroporation, LGN rescue experiments, in vitro binding, spindle angle measurement in mouse cortex\",\n      \"pmids\": [\"28684399\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether earlier in utero RNAi results reflect off-target effects or context differences not resolved\", \"Mechanism preventing AGS3 cortical recruitment unclear\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"AGS3's TGN trafficking function was validated in early embryogenesis: AGS3 knockout arrests mouse embryos after the 4-cell stage with impaired E-cadherin delivery to the plasma membrane and dispersed TGN markers, rescued by Gαi1 overexpression.\",\n      \"evidence\": \"CRISPR/Cas9 knockout in mouse embryos, live imaging of TGN markers, Gαi1 rescue\",\n      \"pmids\": [\"33148610\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct mechanism by which AGS3/Gαi1 regulates TGN vesicle budding or sorting not established\", \"Whether Gβγ or Gαi is the operative downstream effector in TGN trafficking unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"A complete signaling axis was defined in macrophages: USP9X stabilizes GPSM1 via K63-deubiquitination; GPSM1 sequesters Gαi3·GDP, elevating cAMP/PKA/CREB signaling that transcribes TNFAIP3, thereby inhibiting TLR4-induced NF-κB and promoting metabolic inflammation.\",\n      \"evidence\": \"Myeloid-specific GPSM1 KO mice, HFD metabolic phenotyping, ChIP-PCR, mass spectrometry, co-IP\",\n      \"pmids\": [\"36434066\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Gβγ liberation contributes to the inflammatory phenotype not tested\", \"Ubiquitin ligase targeting GPSM1 for K63 ubiquitination not identified\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"The long-standing question of AGS3 vs LGN in spindle orientation was definitively resolved in epidermis: AGS3 antagonizes LGN by displacing it from the apical cortex, promoting planar/symmetric divisions, while LGN promotes perpendicular/asymmetric divisions; genetic epistasis confirms AGS3 acts through LGN.\",\n      \"evidence\": \"In vivo mouse epidermal manipulation, live imaging, double-mutant epistasis, clonal lineage tracing\",\n      \"pmids\": [\"37017303\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism by which AGS3 displaces LGN from cortex not defined\", \"Whether AGS3 competes directly with LGN for Gαi or acts indirectly unclear\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"The molecular basis for AGS3/LGN functional divergence in spindle orientation was identified: AGS3 cannot form stable hetero-hexameric complexes with NuMA due to differences in ~20 N-terminal residues preceding the TPR domain, and Insc selectively disrupts AGS3/NuMA but not LGN/NuMA complexes.\",\n      \"evidence\": \"Biochemical reconstitution, gel filtration, pulldown with domain truncations\",\n      \"pmids\": [\"39580365\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural determination of AGS3 TPR domain vs LGN TPR domain not achieved\", \"Whether this oligomerization difference fully explains all in vivo context-dependent phenotypes unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Direct demonstration that AGS3's GDI activity is sufficient to liberate Gβγ signaling was achieved using an optogenetic GPR-based tool (OptoGDI) at the plasma membrane, producing localized PIP3 and triggering macrophage migration without GPCR activation.\",\n      \"evidence\": \"Optogenetic plasma membrane recruitment, PIP3 biosensor imaging, macrophage migration assay\",\n      \"pmids\": [\"39904370\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether endogenous AGS3 produces comparable spatially restricted Gβγ signals not shown\", \"OptoGDI may not recapitulate TPR-domain-dependent regulation of endogenous AGS3\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the identity of the E3 ubiquitin ligase targeting GPSM1, the structural basis for differential GPR motif affinities and their regulation by phosphorylation, the mechanism by which AGS3 displaces LGN from the cortex in epithelia, and whether AGS3 functions primarily through Gαi sequestration or Gβγ liberation in each specific biological context.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No E3 ligase for GPSM1 identified\", \"No high-resolution structure of full-length AGS3 or AGS3–Gαi complex\", \"Gαi vs Gβγ effector identity in specific tissues not systematically resolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 2, 7, 31]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [11, 15, 27]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [8, 17, 23]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [12, 24]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [16, 31]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [5, 15]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 9, 16, 21, 26]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [5, 15, 28]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [12, 24]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [10, 27]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [21, 26]}\n    ],\n    \"complexes\": [\n      \"AGS3·Gαi·GDP complex\",\n      \"mInsc–AGS3–Par3 complex\"\n    ],\n    \"partners\": [\n      \"GNAI1\",\n      \"GNAI3\",\n      \"RIC8A\",\n      \"USP9X\",\n      \"STK11\",\n      \"INSC\",\n      \"GPSM2\",\n      \"NUMA1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}