{"gene":"GNB4","run_date":"2026-04-28T18:06:53","timeline":{"discoveries":[{"year":1999,"finding":"GNB4 (Gβ4) belongs to the G protein β subunit gene family, which encodes WD40 repeat-containing proteins that form obligate dimers with Gγ subunits and serve as scaffolds for heterotrimeric G protein signaling; the family members share conserved domain architecture and genomic organization.","method":"Genomic sequence analysis and phylogenetic characterization of the G protein subunit gene families","journal":"Genomics","confidence":"Medium","confidence_rationale":"Tier 3 — foundational family characterization, single study, descriptive genomic analysis","pmids":["10644457"],"is_preprint":false},{"year":2002,"finding":"Gβ subunits (including Gβ1 and by extension other Gβ isoforms) can be phosphorylated at His-266 by nucleoside diphosphate kinase B (NDPK B), which forms a complex with Gβγ dimers; this high-energy phosphate transfer from GTP can be relayed to GDP to generate GTP, providing a non-canonical mechanism for G protein activation independent of GPCRs.","method":"Biochemical enrichment of Gβ-phosphorylating activity, co-immunoprecipitation, thiophosphorylation with radiolabeled GTPγS, peptide sequencing to identify His-266 in Gβ1; reconstitution with purified Gβγ","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with purified proteins, site-specific phosphorylation identified by peptide sequencing and mutagenesis-compatible mapping, multiple orthogonal methods","pmids":["12486123"],"is_preprint":false},{"year":2005,"finding":"Gβ4 (along with Gβ1 and Gβ2) can couple with Gαi1, Gαi2, or Gαi3 to form heterotrimers that are activated by α2-adrenergic receptors; the degree of G protein activation is determined by the specific combination of Gαi and Gβ subunit isoforms rather than by the identity of either subunit alone, establishing combinatorial selectivity in GPCR signaling.","method":"FRET between Gαi-YFP and CFP-Gβ chimeras in live HeLa cells; siRNA knockdown of α2-adrenergic receptor subtypes; radiolabeled antagonist binding; RT-PCR","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — live-cell FRET with reciprocal siRNA knockdown controls and multiple Gβ/Gα combinations tested, rigorous quantitative readout","pmids":["16371464"],"is_preprint":false},{"year":2013,"finding":"Missense mutations in GNB4 (p.Gly53Asp and p.Lys89Glu) cause dominant intermediate Charcot-Marie-Tooth disease (CMTDIF); Gβ4 is expressed in axons and Schwann cells of peripheral nerves, and both mutant proteins impair bradykinin-induced GPCR signaling that is normally facilitated by wild-type Gβ4, while p.Gly53Asp also causes significantly reduced Gβ4 protein expression in sural nerve.","method":"Genome-wide linkage mapping; exome sequencing; Sanger sequencing for segregation; immunohistochemistry on sural nerve biopsy; in vitro GPCR signaling assay (bradykinin-induced signaling) with wild-type vs. mutant Gβ4","journal":"American Journal of Human Genetics","confidence":"High","confidence_rationale":"Tier 2 — genetic segregation in family plus functional in vitro assay demonstrating loss-of-function of GPCR signaling for both independent mutations, with IHC localization data","pmids":["23434117"],"is_preprint":false},{"year":2016,"finding":"A de novo GNB4 mutation p.Lys57Glu (not present in parents or unaffected sibling) causes severe CMT neuropathy, further confirming that GNB4 is a causative CMT gene and that de novo mutations in this gene are pathogenic.","method":"Whole exome sequencing; Sanger sequencing for segregation analysis in family trio","journal":"Neuromuscular Disorders","confidence":"Medium","confidence_rationale":"Tier 3 — genetic confirmation by segregation analysis, no new functional mechanistic experiments beyond prior work","pmids":["27908631"],"is_preprint":false},{"year":2017,"finding":"A novel GNB4 missense variant p.Gln220Arg in exon 8 causes autosomal dominant CMT neuropathy; the affected residue lies in the highly conserved WD40 domain of GNB4, establishing that the WD40 repeat domain is critical for Gβ4 function in peripheral nerves.","method":"Exome sequencing; Sanger sequencing for familial segregation; absence confirmed in 502 Japanese controls and ExAC database","journal":"European Journal of Medical Genetics","confidence":"Medium","confidence_rationale":"Tier 3 — genetic evidence placing pathogenic variants in WD40 domain; no in vitro functional assay performed","pmids":["28642160"],"is_preprint":false},{"year":2021,"finding":"GNB4 mutations (p.Gly77Arg and p.Lys89Glu) cause not only intermediate-type but also demyelinating-type CMT neuropathy; sural nerve biopsy of p.Lys89Glu patients showed severe loss of myelinated axons with onion bulb formation, indicating that specific GNB4 mutations differentially affect the demyelinating vs. axonal disease mechanism.","method":"Whole-exome sequencing; nerve conduction studies; sural nerve biopsy with histopathology; lower extremity MRI for muscle fat infiltration","journal":"Life (Basel)","confidence":"Medium","confidence_rationale":"Tier 3 — histopathological characterization with electrophysiology extends phenotypic/pathological understanding; no new in vitro mechanistic experiments","pmids":["34071515"],"is_preprint":false},{"year":2021,"finding":"GNB4 is a target of miR-133b in osteoblasts; miR-133b overexpression promotes osteoblast viability and differentiation (increased ALP, Runx2, Osterix, OPN expression), and these effects are reversed by GNB4 overexpression, placing GNB4 as a negative regulator of osteoblast differentiation downstream of miR-133b.","method":"miRNA target validation; qRT-PCR and Western blot for GNB4 expression; CCK-8 viability assay; flow cytometry apoptosis assay; Western blot for osteoblast differentiation markers; gain- and loss-of-function in hFOB 1.19 cells","journal":"Biochemical Genetics","confidence":"Medium","confidence_rationale":"Tier 3 — cell-based gain/loss-of-function with defined phenotypic readout; miRNA-target relationship established; single lab, single cell line","pmids":["33687637"],"is_preprint":false},{"year":2023,"finding":"H. pylori infection promotes GNB4 expression in gastric cancer cells via an NF-κB–TET1–GNB4 promoter demethylation axis; elevated GNB4 in turn activates the Hippo-YAP1 pathway to drive oncogenic proliferation, invasion, and metastasis both in vitro and in vivo.","method":"Methylation-specific PCR; pyrosequencing; mass spectrometry for methylation; chromatin immunoprecipitation (ChIP) of TET1 on GNB4 promoter; co-immunoprecipitation; CCK-8, EdU, colony formation, transwell assays; xenograft mouse model; Western blot, immunofluorescence, immunohistochemistry; siRNA knockdown and overexpression","journal":"BMC Medicine","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (ChIP, Co-IP, in vivo xenograft, gain/loss-of-function) in a single study establishing the mechanistic pathway from H. pylori to GNB4 to YAP1","pmids":["37016382"],"is_preprint":false},{"year":2024,"finding":"GNB4 silencing in glioma cells promotes pyroptosis and inhibits proliferation, migration, and invasion by activating the cGAS-STING pathway; pharmacological inhibition of cGAS-STING reverses the anti-tumor effects of GNB4 silencing and downregulates pyroptosis-related proteins, establishing GNB4 as an upstream suppressor of cGAS-STING-mediated pyroptosis in glioma.","method":"siRNA-mediated GNB4 silencing; CCK-8 proliferation assay; wound-healing and transwell migration/invasion assays; Western blot for pyroptosis-related proteins; ELISA for inflammatory factors; cGAS-STING pathway inhibitor rescue experiments","journal":"Molecular Biotechnology","confidence":"Medium","confidence_rationale":"Tier 2-3 — loss-of-function with defined cellular phenotype and pathway placement via inhibitor rescue; single lab, single study","pmids":["38814382"],"is_preprint":false},{"year":2024,"finding":"CircRREB1 directly interacts with GNB4 protein in breast cancer cells and this interaction activates Erk1/2 signaling, promoting tumor cell proliferation, migration, and invasion; knockdown of circRREB1 phenocopies GNB4 pathway inhibition and rescue experiments confirm the circRREB1-GNB4-Erk1/2 axis.","method":"RNA pull-down; mass spectrometry; Western blot; RNA immunoprecipitation (RIP); fluorescence in situ hybridization (FISH); rescue experiments with GNB4 modulation; in vivo tumor models","journal":"Heliyon","confidence":"Medium","confidence_rationale":"Tier 2-3 — RNA pull-down with MS identifies GNB4 as circRREB1 interactor, confirmed by RIP; rescue experiments establish functional epistasis; single study","pmids":["38617926"],"is_preprint":false},{"year":2025,"finding":"Pathogenic GNB4 variants associated with CMT cluster spatially on the 3D structure of the GNB4 protein, and GNB4-associated neuropathy presents with mixed axonal and demyelinating features; a novel variant p.Ile80Thr was identified and classified as likely pathogenic.","method":"Whole exome sequencing; segregation analysis; neurological and electrophysiological assessment; 3D protein structural mapping of variant positions; literature review and ACMG variant reclassification","journal":"Neurology: Genetics","confidence":"Medium","confidence_rationale":"Tier 3 — structural clustering of pathogenic variants provides spatial mechanistic insight; no new in vitro functional experiments","pmids":["41164122"],"is_preprint":false}],"current_model":"GNB4 encodes guanine nucleotide-binding protein subunit beta-4 (Gβ4), a WD40 repeat-containing scaffold that forms obligate Gβγ dimers and couples with multiple Gαi subunits to mediate GPCR signaling (including α2-adrenergic and bradykinin receptors) with combinatorial selectivity; pathogenic missense mutations in the WD40 domain (clustering in 3D space) impair this GPCR signaling capacity and cause dominant intermediate/demyelinating Charcot-Marie-Tooth neuropathy, while in non-neuronal contexts GNB4 acts downstream of H. pylori-induced NF-κB–TET1 demethylation to activate Hippo-YAP1 oncogenic signaling in gastric cancer, upstream of cGAS-STING-mediated pyroptosis suppression in glioma, and as a negative regulator of osteoblast differentiation targeted by miR-133b."},"narrative":{"teleology":[{"year":1999,"claim":"Establishing that GNB4 belongs to the Gβ gene family encoding conserved WD40-repeat scaffolds provided the foundational framework for understanding its role in heterotrimeric G protein signaling.","evidence":"Genomic sequence and phylogenetic analysis of the G protein subunit gene families","pmids":["10644457"],"confidence":"Medium","gaps":["No isoform-specific functional data for Gβ4 itself","Expression pattern of GNB4 across tissues not determined"]},{"year":2002,"claim":"Demonstrating that Gβ subunits can be phosphorylated at His-266 by NDPK B to relay high-energy phosphate to GDP revealed a non-canonical, GPCR-independent mechanism of G protein activation potentially applicable to Gβ4.","evidence":"Biochemical enrichment, co-immunoprecipitation, thiophosphorylation with radiolabeled GTPγS, and peptide sequencing on purified Gβγ; primarily shown for Gβ1","pmids":["12486123"],"confidence":"High","gaps":["Direct demonstration on Gβ4 specifically was not performed","Physiological relevance of His-266 phosphorylation in vivo remains unresolved"]},{"year":2005,"claim":"Live-cell FRET experiments revealed that Gβ4 couples with Gαi1, Gαi2, or Gαi3 to form functionally distinct heterotrimers at α2-adrenergic receptors, establishing that GPCR signaling specificity arises from combinatorial Gα–Gβ pairing rather than individual subunit identity.","evidence":"FRET between Gαi-YFP and CFP-Gβ chimeras in HeLa cells with siRNA knockdown of receptor subtypes","pmids":["16371464"],"confidence":"High","gaps":["Whether combinatorial selectivity extends to other GPCR families was not tested","Downstream effector specificity of Gβ4-containing heterotrimers not characterized"]},{"year":2013,"claim":"The discovery that GNB4 missense mutations (p.Gly53Asp, p.Lys89Glu) cause dominant intermediate CMT neuropathy and impair bradykinin-induced GPCR signaling established GNB4 as a disease gene and linked its WD40-mediated signaling function to peripheral nerve biology.","evidence":"Genome-wide linkage, exome sequencing, familial segregation, in vitro GPCR signaling assays with wild-type vs. mutant Gβ4, immunohistochemistry on sural nerve","pmids":["23434117"],"confidence":"High","gaps":["Mechanism by which impaired Gβ4 signaling leads to neuropathy (axonal vs. Schwann cell-autonomous) not resolved","Crystal structure of mutant Gβ4 not available"]},{"year":2016,"claim":"Identification of a de novo GNB4 mutation (p.Lys57Glu) in severe CMT confirmed that pathogenic GNB4 variants arise independently and are not merely inherited segregating variants.","evidence":"Whole exome sequencing with Sanger validation in a family trio","pmids":["27908631"],"confidence":"Medium","gaps":["No functional assay performed for this specific variant","Genotype-phenotype correlations for disease severity remain poorly defined"]},{"year":2017,"claim":"A novel pathogenic variant (p.Gln220Arg) in exon 8 placed the disease-associated mutation spectrum firmly within the WD40 repeat domain, reinforcing the structural importance of this domain for Gβ4 function.","evidence":"Exome sequencing with familial segregation; absence in 502 controls and ExAC","pmids":["28642160"],"confidence":"Medium","gaps":["No in vitro functional validation of p.Gln220Arg","Structure-function relationship of specific WD40 blades to signaling not dissected"]},{"year":2021,"claim":"Demonstrating that certain GNB4 mutations produce demyelinating rather than purely intermediate neuropathy, with sural nerve histopathology showing onion bulb formation, resolved that the disease mechanism involves a prominent Schwann cell-autonomous demyelinating component.","evidence":"Whole exome sequencing, nerve conduction studies, sural nerve biopsy with histopathology, and lower extremity MRI","pmids":["34071515"],"confidence":"Medium","gaps":["Mechanism by which Gβ4 loss-of-function specifically causes demyelination not elucidated","Animal model recapitulating GNB4-CMT not established"]},{"year":2021,"claim":"Identifying GNB4 as a direct target of miR-133b whose overexpression reverses osteoblast differentiation revealed a non-neuronal, non-canonical role for Gβ4 as a negative regulator of osteogenic commitment.","evidence":"miRNA target validation, gain/loss-of-function experiments, Western blot and qRT-PCR for differentiation markers in hFOB 1.19 cells","pmids":["33687637"],"confidence":"Medium","gaps":["Downstream signaling pathway by which GNB4 suppresses osteoblast differentiation unknown","Single cell line, no in vivo bone formation data"]},{"year":2023,"claim":"Tracing GNB4 upregulation to H. pylori-driven NF-κB–TET1 promoter demethylation and its downstream activation of the Hippo-YAP1 pathway established a complete mechanistic axis through which GNB4 drives gastric cancer oncogenesis.","evidence":"Methylation-specific PCR, pyrosequencing, ChIP of TET1 on GNB4 promoter, Co-IP, functional assays (CCK-8, transwell, colony formation), xenograft mouse model","pmids":["37016382"],"confidence":"High","gaps":["How Gβ4 protein biochemically activates Hippo-YAP1 (direct interaction or intermediate effectors) not resolved","Whether this pathway operates in other H. pylori-associated malignancies untested"]},{"year":2024,"claim":"Showing that GNB4 silencing activates cGAS-STING-mediated pyroptosis in glioma, reversible by STING inhibition, placed Gβ4 as an upstream suppressor of innate immune sensing in a second cancer type.","evidence":"siRNA knockdown, CCK-8, transwell, Western blot for pyroptosis markers, ELISA, cGAS-STING inhibitor rescue in glioma cell lines","pmids":["38814382"],"confidence":"Medium","gaps":["Biochemical mechanism linking Gβ4 to cGAS-STING suppression unknown","No in vivo validation","Single study, not independently confirmed"]},{"year":2024,"claim":"Discovery that circRREB1 physically binds GNB4 protein to activate Erk1/2 signaling in breast cancer revealed a non-canonical RNA-protein interaction mode for Gβ4 distinct from classical Gβγ heterotrimer function.","evidence":"RNA pull-down with mass spectrometry, RIP, FISH, rescue experiments, in vivo tumor models in breast cancer cells","pmids":["38617926"],"confidence":"Medium","gaps":["Structural basis for circRREB1-Gβ4 interaction undetermined","Whether circRNA binding competes with Gγ dimerization unknown","Single study"]},{"year":2025,"claim":"3D structural mapping of all known pathogenic GNB4 variants demonstrated spatial clustering on the Gβ4 WD40 propeller, suggesting a shared structural mechanism of disruption at a functional interface.","evidence":"Whole exome sequencing, electrophysiology, ACMG reclassification, and 3D protein structural mapping","pmids":["41164122"],"confidence":"Medium","gaps":["No experimental structure of Gβ4 bound to Gα or GPCR with mutants modeled","Functional consequence of clustering (e.g., loss of Gα binding surface) not biochemically tested"]},{"year":null,"claim":"The biochemical mechanism by which Gβ4 WD40 domain mutations specifically cause peripheral nerve demyelination, and how Gβ4 activates Hippo-YAP1 or suppresses cGAS-STING in cancer, remain major unresolved questions.","evidence":"","pmids":[],"confidence":"High","gaps":["No Gβ4-specific crystal or cryo-EM structure available","No animal model recapitulating GNB4-CMT neuropathy","Biochemical link between Gβ4 and non-canonical signaling pathways (YAP1, cGAS-STING, Erk1/2 via circRNA) not mechanistically resolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,2,3]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[2,3,8,9]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[2,3]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[2,8]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,3,8,9,10]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[3,4,5,6,11]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[9]}],"complexes":["Heterotrimeric G protein (Gαβγ)"],"partners":["GNAI1","GNAI2","GNAI3","YAP1","TET1","CGAS","STING1"],"other_free_text":[]},"mechanistic_narrative":"GNB4 encodes guanine nucleotide-binding protein subunit beta-4 (Gβ4), a WD40 repeat-containing scaffold that forms obligate Gβγ dimers and participates in heterotrimeric G protein signaling with combinatorial selectivity determined by specific Gαi–Gβ pairings at GPCRs such as α2-adrenergic and bradykinin receptors [PMID:16371464, PMID:23434117]. Missense mutations clustering within the WD40 domain impair GPCR signaling and cause autosomal dominant Charcot-Marie-Tooth neuropathy with mixed demyelinating and axonal features [PMID:23434117, PMID:34071515, PMID:41164122]. In cancer contexts, GNB4 expression is upregulated by NF-κB–TET1-mediated promoter demethylation to activate Hippo-YAP1 oncogenic signaling in gastric cancer, suppresses cGAS-STING-dependent pyroptosis in glioma, and interacts with circRREB1 to drive Erk1/2 signaling in breast cancer [PMID:37016382, PMID:38814382, PMID:38617926]. GNB4 also functions as a negative regulator of osteoblast differentiation downstream of miR-133b [PMID:33687637]."},"prefetch_data":{"uniprot":{"accession":"Q9HAV0","full_name":"Guanine nucleotide-binding protein subunit beta-4","aliases":["Transducin beta chain 4"],"length_aa":340,"mass_kda":37.6,"function":"Guanine nucleotide-binding proteins (G proteins) are involved as a modulator or transducer in various transmembrane signaling systems. The beta and gamma chains are required for the GTPase activity, for replacement of GDP by GTP, and for G protein-effector interaction","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q9HAV0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GNB4","classification":"Not Classified","n_dependent_lines":7,"n_total_lines":1208,"dependency_fraction":0.005794701986754967},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"GNB1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/GNB4","total_profiled":1310},"omim":[{"mim_id":"615185","title":"CHARCOT-MARIE-TOOTH DISEASE, DOMINANT INTERMEDIATE F; CMTDIF","url":"https://www.omim.org/entry/615185"},{"mim_id":"610863","title":"GUANINE NUCLEOTIDE-BINDING PROTEIN, BETA-4; GNB4","url":"https://www.omim.org/entry/610863"},{"mim_id":"607298","title":"GUANINE NUCLEOTIDE-BINDING PROTEIN, GAMMA-13; GNG13","url":"https://www.omim.org/entry/607298"},{"mim_id":"606482","title":"CHARCOT-MARIE-TOOTH DISEASE, DOMINANT INTERMEDIATE B; CMTDIB","url":"https://www.omim.org/entry/606482"},{"mim_id":"139130","title":"GUANINE NUCLEOTIDE-BINDING PROTEIN, BETA-3; GNB3","url":"https://www.omim.org/entry/139130"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"},{"location":"Golgi apparatus","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/GNB4"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q9HAV0","domains":[{"cath_id":"2.130.10.10","chopping":"45-338","consensus_level":"high","plddt":97.3584,"start":45,"end":338},{"cath_id":"1.20.5","chopping":"1-35","consensus_level":"medium","plddt":95.6789,"start":1,"end":35}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9HAV0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9HAV0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9HAV0-F1-predicted_aligned_error_v6.png","plddt_mean":97.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GNB4","jax_strain_url":"https://www.jax.org/strain/search?query=GNB4"},"sequence":{"accession":"Q9HAV0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9HAV0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9HAV0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9HAV0"}},"corpus_meta":[{"pmid":"23434117","id":"PMC_23434117","title":"Exome 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missense variant (Gln220Arg) of GNB4 encoding guanine nucleotide-binding protein, subunit beta-4 in a Japanese family with autosomal dominant motor and sensory neuropathy.","date":"2017","source":"European journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/28642160","citation_count":12,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"27908631","id":"PMC_27908631","title":"Confirmation of the GNB4 gene as causal for Charcot-Marie-Tooth disease by a novel de novo mutation in a Czech patient.","date":"2016","source":"Neuromuscular disorders : NMD","url":"https://pubmed.ncbi.nlm.nih.gov/27908631","citation_count":11,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"34071515","id":"PMC_34071515","title":"Clinical and Neuroimaging Features in Charcot-Marie-Tooth Patients with GNB4 Mutations.","date":"2021","source":"Life (Basel, 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Ubiquitylation.","date":"2016","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/27565346","citation_count":188,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"23602568","id":"PMC_23602568","title":"The protein interaction landscape of the human CMGC kinase group.","date":"2013","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/23602568","citation_count":174,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"17897319","id":"PMC_17897319","title":"Integral and associated lysosomal membrane proteins.","date":"2007","source":"Traffic (Copenhagen, Denmark)","url":"https://pubmed.ncbi.nlm.nih.gov/17897319","citation_count":163,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"32877691","id":"PMC_32877691","title":"A High-Density Human Mitochondrial Proximity Interaction Network.","date":"2020","source":"Cell 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communications","url":"https://pubmed.ncbi.nlm.nih.gov/30425250","citation_count":123,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"35140242","id":"PMC_35140242","title":"Human transcription factor protein interaction networks.","date":"2022","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/35140242","citation_count":123,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"12486123","id":"PMC_12486123","title":"Activation of heterotrimeric G proteins by a high energy phosphate transfer via nucleoside diphosphate kinase (NDPK) B and Gbeta subunits. Complex formation of NDPK B with Gbeta gamma dimers and phosphorylation of His-266 IN Gbeta.","date":"2002","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12486123","citation_count":118,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"16371464","id":"PMC_16371464","title":"Gialpha and Gbeta subunits both define selectivity of G protein activation by alpha2-adrenergic receptors.","date":"2005","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/16371464","citation_count":113,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"30442662","id":"PMC_30442662","title":"Ubiquilin 2 modulates ALS/FTD-linked FUS-RNA complex dynamics and stress granule formation.","date":"2018","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/30442662","citation_count":108,"is_preprint":false,"source_track":"gene2pubmed"}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7801,"output_tokens":1522,"usd":0.023117},"stage2":{"model":"claude-opus-4-6","input_tokens":4764,"output_tokens":1844,"usd":0.10488},"total_usd":0.363693,"stage1_batch_id":"msgbatch_01DzrsgVgYngY1hvM3DU1yF2","stage2_batch_id":"msgbatch_01KA9b7iRzKFdhoBUT7vCvSe","note":"batch pricing = 50% of standard","round2_stage1":{"model":"claude-sonnet-4-6","input_tokens":19356,"output_tokens":4467,"usd":0.062536},"round2_rules_fired":"R3","round2_stage2":{"model":"claude-opus-4-6","input_tokens":7093,"output_tokens":3199,"usd":0.17316}},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2013,\n      \"finding\": \"GNB4 (Gβ4) facilitates bradykinin-induced G-protein-coupled receptor (GPCR) signaling; missense mutations p.Gly53Asp and p.Lys89Glu impair this signaling activity in vitro, and Gβ4 is localized to axons and Schwann cells of peripheral nerves by immunohistochemistry.\",\n      \"method\": \"In vitro GPCR signaling assay with mutant vs. wild-type Gβ4; immunohistochemistry of sural nerve tissue\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct in vitro functional assay demonstrating loss of GPCR signaling with defined mutations, supported by localization data; single lab\",\n      \"pmids\": [\"23434117\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"GNB4 promotes gastric carcinogenesis via the Hippo-YAP1 pathway; H. pylori infection activates NF-κB, upregulating TET1, which demethylates the GNB4 promoter (CpG#5 site), inducing GNB4 expression that drives oncogenic behaviors through YAP1 activation. Co-immunoprecipitation was used to confirm pathway interactions.\",\n      \"method\": \"Co-immunoprecipitation, chromatin immunoprecipitation, gain- and loss-of-function experiments (CCK-8, EdU, colony formation, transwell), xenograft mouse model, methylation-specific PCR, pyrosequencing\",\n      \"journal\": \"BMC medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods in a single lab including co-IP, ChIP, in vivo xenograft, and functional rescue experiments\",\n      \"pmids\": [\"37016382\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"circRREB1 directly interacts with GNB4 protein, and this interaction activates Erk1/2 signaling to promote breast cancer progression; knockdown of circRREB1 suppresses proliferation, migration, and invasion.\",\n      \"method\": \"RNA pull-down, mass spectrometry, RNA immunoprecipitation (RIP), Western blot, FISH, rescue experiments\",\n      \"journal\": \"Heliyon\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct interaction established by RNA pull-down and RIP with multiple orthogonal methods; single lab\",\n      \"pmids\": [\"38617926\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"miR-133b targets GNB4 (confirmed by downstream validation); overexpression of miR-133b promotes osteoblast viability and differentiation (increased ALP, Runx2, Osterix, OPN), and this effect is reversed by GNB4 overexpression, placing GNB4 as a negative regulator of osteoblast differentiation downstream of miR-133b.\",\n      \"method\": \"miRNA target validation, gain- and loss-of-function in hFOB 1.19 cells, Western blot, CCK-8, flow cytometry\",\n      \"journal\": \"Biochemical genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — functional epistasis shown by rescue experiment, but no direct luciferase or CLIP confirmation of miR-133b/GNB4 interaction shown in this paper; single lab\",\n      \"pmids\": [\"33687637\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Silencing GNB4 in glioma cells promotes pyroptosis and inhibits proliferation, migration, and invasion by activating the cGAS-STING pathway; pyroptosis inhibitors and cGAS-STING pathway inhibitors reverse these effects, placing GNB4 upstream of cGAS-STING-mediated pyroptosis.\",\n      \"method\": \"siRNA knockdown, Western blot (pyroptosis-related proteins), ELISA (inflammatory factors), cell viability/wound-healing/transwell assays, pathway inhibitor rescue experiments\",\n      \"journal\": \"Molecular biotechnology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — pathway placement via pharmacological inhibitor rescue without genetic epistasis or direct biochemical interaction; single lab\",\n      \"pmids\": [\"38814382\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Pathogenic GNB4 variants in CMT patients cluster in 3D space on the GNB4 protein structure, and the WD40 domain is a critical functional region; the protein's role is in peripheral nerve function consistent with GPCR signaling.\",\n      \"method\": \"Variant mapping onto GNB4 3D protein structure; clinical segregation analysis; electrophysiological assessment\",\n      \"journal\": \"Neurology. Genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — structural clustering is computational/observational without in vitro functional validation of the new variant\",\n      \"pmids\": [\"41164122\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GNB4 (Gβ4) is a G-protein beta subunit that facilitates bradykinin-induced GPCR signaling in peripheral nerves (where it localizes to axons and Schwann cells), and disease-causing missense mutations in its WD40 domain impair this signaling; in cancer contexts, GNB4 acts downstream of promoter demethylation to activate Hippo-YAP1 and Erk1/2 pathways, and upstream of the cGAS-STING pyroptosis pathway.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\nI'll classify each paper first, then extract discoveries from KEPT papers.\n\n**Classification:**\n\nRetrieved papers:\n1. PMID:23434117 — KEEP (GNB4 mutations in CMT, GPCR signaling experiments)\n2. PMID:37016382 — KEEP (GNB4 protein in gastric cancer, mechanistic pathway studies)\n3. PMID:38154055 — EXCLUDE (methylation biomarker study, no mechanism)\n4. PMID:28642160 — KEEP (novel GNB4 variant in CMT, WD40 domain)\n5. PMID:27908631 — KEEP (GNB4 variant confirmation in CMT)\n6. PMID:34071515 — KEEP (GNB4 mutations, clinical/electrophysiological characterization)\n7. PMID:38617926 — KEEP (circRREB1 interacts with GNB4 protein, Erk1/2 signaling — describes GNB4 protein function)\n8. PMID:33687637 — KEEP (miR-133b targets GNB4, osteoblast differentiation)\n9. PMID:38814382 — KEEP (GNB4 silencing, pyroptosis, cGAS-STING pathway)\n10. PMID:35170486 — EXCLUDE (case B: alt-locus product — circ-GNB4 circular RNA, not canonical GNB4 protein; also RETRACTED)\n11. PMID:41164122 — KEEP (GNB4 variants in CMT, 3D clustering of pathogenic variants)\n\nGene2pubmed curated papers:\n- PMID:12477932 — EXCLUDE (general cDNA resource)\n- PMID:26186194 — EXCLUDE (general interactome resource)\n- PMID:28514442 — EXCLUDE (general interactome resource)\n- PMID:26496610 — EXCLUDE (general interactome resource)\n- PMID:14702039 — EXCLUDE (general cDNA resource)\n- PMID:21873635 — EXCLUDE (GO annotation methods)\n- PMID:12626323 — EXCLUDE (glucagon/glucose metabolism, no GNB4)\n- PMID:15489334 — EXCLUDE (general cDNA resource)\n- PMID:35271311 — EXCLUDE (general proteome resource)\n- PMID:20360068 — EXCLUDE (general complex analysis)\n- PMID:26344197 — EXCLUDE (general metazoan complexes)\n- PMID:10570481 — EXCLUDE (Ggamma13/gustducin, not GNB4)\n- PMID:23583979 — EXCLUDE (GWAS heart rate, no GNB4 mechanism)\n- PMID:10644457 — KEEP (G protein subunit gene families — foundational characterization)\n- PMID:17207965 — EXCLUDE (ORFeome resource)\n- PMID:25281560 — EXCLUDE (BioID methods)\n- PMID:29568061 — EXCLUDE (MAC-tag methods)\n- PMID:26673895 — EXCLUDE (CRM1 export)\n- PMID:27565346 — EXCLUDE (E3 ligase mechanism)\n- PMID:23602568 — EXCLUDE (CMGC kinase interactions)\n- PMID:17897319 — EXCLUDE (lysosomal membrane proteomics)\n- PMID:32877691 — EXCLUDE (mitochondrial proximity network)\n- PMID:23533145 — EXCLUDE (prostate exosome proteomics)\n- PMID:31871319 — EXCLUDE (Rho GTPase network)\n- PMID:30425250 — EXCLUDE (USP14 substrates)\n- PMID:35140242 — EXCLUDE (TF interaction networks)\n- PMID:12486123 — KEEP (NDPK B phosphorylation of Gbeta subunits including His-266 — mechanistic)\n- PMID:16371464 — KEEP (Gbeta4 selectivity in alpha2-adrenergic receptor signaling)\n- PMID:30442662 — EXCLUDE (UBQLN2/FUS, no GNB4)\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"GNB4 (Gβ4) belongs to the G protein β subunit gene family, which encodes WD40 repeat-containing proteins that form obligate dimers with Gγ subunits and serve as scaffolds for heterotrimeric G protein signaling; the family members share conserved domain architecture and genomic organization.\",\n      \"method\": \"Genomic sequence analysis and phylogenetic characterization of the G protein subunit gene families\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — foundational family characterization, single study, descriptive genomic analysis\",\n      \"pmids\": [\"10644457\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Gβ subunits (including Gβ1 and by extension other Gβ isoforms) can be phosphorylated at His-266 by nucleoside diphosphate kinase B (NDPK B), which forms a complex with Gβγ dimers; this high-energy phosphate transfer from GTP can be relayed to GDP to generate GTP, providing a non-canonical mechanism for G protein activation independent of GPCRs.\",\n      \"method\": \"Biochemical enrichment of Gβ-phosphorylating activity, co-immunoprecipitation, thiophosphorylation with radiolabeled GTPγS, peptide sequencing to identify His-266 in Gβ1; reconstitution with purified Gβγ\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with purified proteins, site-specific phosphorylation identified by peptide sequencing and mutagenesis-compatible mapping, multiple orthogonal methods\",\n      \"pmids\": [\"12486123\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Gβ4 (along with Gβ1 and Gβ2) can couple with Gαi1, Gαi2, or Gαi3 to form heterotrimers that are activated by α2-adrenergic receptors; the degree of G protein activation is determined by the specific combination of Gαi and Gβ subunit isoforms rather than by the identity of either subunit alone, establishing combinatorial selectivity in GPCR signaling.\",\n      \"method\": \"FRET between Gαi-YFP and CFP-Gβ chimeras in live HeLa cells; siRNA knockdown of α2-adrenergic receptor subtypes; radiolabeled antagonist binding; RT-PCR\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — live-cell FRET with reciprocal siRNA knockdown controls and multiple Gβ/Gα combinations tested, rigorous quantitative readout\",\n      \"pmids\": [\"16371464\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Missense mutations in GNB4 (p.Gly53Asp and p.Lys89Glu) cause dominant intermediate Charcot-Marie-Tooth disease (CMTDIF); Gβ4 is expressed in axons and Schwann cells of peripheral nerves, and both mutant proteins impair bradykinin-induced GPCR signaling that is normally facilitated by wild-type Gβ4, while p.Gly53Asp also causes significantly reduced Gβ4 protein expression in sural nerve.\",\n      \"method\": \"Genome-wide linkage mapping; exome sequencing; Sanger sequencing for segregation; immunohistochemistry on sural nerve biopsy; in vitro GPCR signaling assay (bradykinin-induced signaling) with wild-type vs. mutant Gβ4\",\n      \"journal\": \"American Journal of Human Genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic segregation in family plus functional in vitro assay demonstrating loss-of-function of GPCR signaling for both independent mutations, with IHC localization data\",\n      \"pmids\": [\"23434117\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"A de novo GNB4 mutation p.Lys57Glu (not present in parents or unaffected sibling) causes severe CMT neuropathy, further confirming that GNB4 is a causative CMT gene and that de novo mutations in this gene are pathogenic.\",\n      \"method\": \"Whole exome sequencing; Sanger sequencing for segregation analysis in family trio\",\n      \"journal\": \"Neuromuscular Disorders\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — genetic confirmation by segregation analysis, no new functional mechanistic experiments beyond prior work\",\n      \"pmids\": [\"27908631\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"A novel GNB4 missense variant p.Gln220Arg in exon 8 causes autosomal dominant CMT neuropathy; the affected residue lies in the highly conserved WD40 domain of GNB4, establishing that the WD40 repeat domain is critical for Gβ4 function in peripheral nerves.\",\n      \"method\": \"Exome sequencing; Sanger sequencing for familial segregation; absence confirmed in 502 Japanese controls and ExAC database\",\n      \"journal\": \"European Journal of Medical Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — genetic evidence placing pathogenic variants in WD40 domain; no in vitro functional assay performed\",\n      \"pmids\": [\"28642160\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"GNB4 mutations (p.Gly77Arg and p.Lys89Glu) cause not only intermediate-type but also demyelinating-type CMT neuropathy; sural nerve biopsy of p.Lys89Glu patients showed severe loss of myelinated axons with onion bulb formation, indicating that specific GNB4 mutations differentially affect the demyelinating vs. axonal disease mechanism.\",\n      \"method\": \"Whole-exome sequencing; nerve conduction studies; sural nerve biopsy with histopathology; lower extremity MRI for muscle fat infiltration\",\n      \"journal\": \"Life (Basel)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — histopathological characterization with electrophysiology extends phenotypic/pathological understanding; no new in vitro mechanistic experiments\",\n      \"pmids\": [\"34071515\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"GNB4 is a target of miR-133b in osteoblasts; miR-133b overexpression promotes osteoblast viability and differentiation (increased ALP, Runx2, Osterix, OPN expression), and these effects are reversed by GNB4 overexpression, placing GNB4 as a negative regulator of osteoblast differentiation downstream of miR-133b.\",\n      \"method\": \"miRNA target validation; qRT-PCR and Western blot for GNB4 expression; CCK-8 viability assay; flow cytometry apoptosis assay; Western blot for osteoblast differentiation markers; gain- and loss-of-function in hFOB 1.19 cells\",\n      \"journal\": \"Biochemical Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — cell-based gain/loss-of-function with defined phenotypic readout; miRNA-target relationship established; single lab, single cell line\",\n      \"pmids\": [\"33687637\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"H. pylori infection promotes GNB4 expression in gastric cancer cells via an NF-κB–TET1–GNB4 promoter demethylation axis; elevated GNB4 in turn activates the Hippo-YAP1 pathway to drive oncogenic proliferation, invasion, and metastasis both in vitro and in vivo.\",\n      \"method\": \"Methylation-specific PCR; pyrosequencing; mass spectrometry for methylation; chromatin immunoprecipitation (ChIP) of TET1 on GNB4 promoter; co-immunoprecipitation; CCK-8, EdU, colony formation, transwell assays; xenograft mouse model; Western blot, immunofluorescence, immunohistochemistry; siRNA knockdown and overexpression\",\n      \"journal\": \"BMC Medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (ChIP, Co-IP, in vivo xenograft, gain/loss-of-function) in a single study establishing the mechanistic pathway from H. pylori to GNB4 to YAP1\",\n      \"pmids\": [\"37016382\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"GNB4 silencing in glioma cells promotes pyroptosis and inhibits proliferation, migration, and invasion by activating the cGAS-STING pathway; pharmacological inhibition of cGAS-STING reverses the anti-tumor effects of GNB4 silencing and downregulates pyroptosis-related proteins, establishing GNB4 as an upstream suppressor of cGAS-STING-mediated pyroptosis in glioma.\",\n      \"method\": \"siRNA-mediated GNB4 silencing; CCK-8 proliferation assay; wound-healing and transwell migration/invasion assays; Western blot for pyroptosis-related proteins; ELISA for inflammatory factors; cGAS-STING pathway inhibitor rescue experiments\",\n      \"journal\": \"Molecular Biotechnology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — loss-of-function with defined cellular phenotype and pathway placement via inhibitor rescue; single lab, single study\",\n      \"pmids\": [\"38814382\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CircRREB1 directly interacts with GNB4 protein in breast cancer cells and this interaction activates Erk1/2 signaling, promoting tumor cell proliferation, migration, and invasion; knockdown of circRREB1 phenocopies GNB4 pathway inhibition and rescue experiments confirm the circRREB1-GNB4-Erk1/2 axis.\",\n      \"method\": \"RNA pull-down; mass spectrometry; Western blot; RNA immunoprecipitation (RIP); fluorescence in situ hybridization (FISH); rescue experiments with GNB4 modulation; in vivo tumor models\",\n      \"journal\": \"Heliyon\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — RNA pull-down with MS identifies GNB4 as circRREB1 interactor, confirmed by RIP; rescue experiments establish functional epistasis; single study\",\n      \"pmids\": [\"38617926\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Pathogenic GNB4 variants associated with CMT cluster spatially on the 3D structure of the GNB4 protein, and GNB4-associated neuropathy presents with mixed axonal and demyelinating features; a novel variant p.Ile80Thr was identified and classified as likely pathogenic.\",\n      \"method\": \"Whole exome sequencing; segregation analysis; neurological and electrophysiological assessment; 3D protein structural mapping of variant positions; literature review and ACMG variant reclassification\",\n      \"journal\": \"Neurology: Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — structural clustering of pathogenic variants provides spatial mechanistic insight; no new in vitro functional experiments\",\n      \"pmids\": [\"41164122\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GNB4 encodes guanine nucleotide-binding protein subunit beta-4 (Gβ4), a WD40 repeat-containing scaffold that forms obligate Gβγ dimers and couples with multiple Gαi subunits to mediate GPCR signaling (including α2-adrenergic and bradykinin receptors) with combinatorial selectivity; pathogenic missense mutations in the WD40 domain (clustering in 3D space) impair this GPCR signaling capacity and cause dominant intermediate/demyelinating Charcot-Marie-Tooth neuropathy, while in non-neuronal contexts GNB4 acts downstream of H. pylori-induced NF-κB–TET1 demethylation to activate Hippo-YAP1 oncogenic signaling in gastric cancer, upstream of cGAS-STING-mediated pyroptosis suppression in glioma, and as a negative regulator of osteoblast differentiation targeted by miR-133b.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"GNB4 encodes the G-protein β4 subunit, which participates in heterotrimeric G-protein signaling downstream of GPCRs and localizes to axons and Schwann cells in peripheral nerves, where it facilitates bradykinin-induced signaling; missense mutations in its WD40 domain (e.g., p.Gly53Asp, p.Lys89Glu) impair this activity and cause Charcot-Marie-Tooth disease [PMID:23434117, PMID:41164122]. In cancer contexts, GNB4 expression is induced by NF-κB/TET1-mediated promoter demethylation following H. pylori infection and drives gastric carcinogenesis through Hippo-YAP1 pathway activation [PMID:37016382]. GNB4 also interacts with the circular RNA circRREB1 to activate Erk1/2 signaling in breast cancer [PMID:38617926], and its silencing in glioma cells triggers cGAS-STING-dependent pyroptosis [PMID:38814382].\",\n  \"teleology\": [\n    {\n      \"year\": 2013,\n      \"claim\": \"Establishing GNB4 as a functional GPCR signaling component in peripheral nerves resolved the question of which Gβ subunit operates in Schwann cell/axon signaling and linked its dysfunction to inherited neuropathy.\",\n      \"evidence\": \"In vitro GPCR signaling assays comparing wild-type and mutant Gβ4, plus immunohistochemistry on sural nerve tissue\",\n      \"pmids\": [\"23434117\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Downstream effectors of Gβ4 in peripheral nerve GPCR signaling are not defined\",\n        \"Whether Gβ4 partners with specific Gγ subunits in Schwann cells is unknown\",\n        \"Only two missense mutations tested functionally\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Rescue experiments placed GNB4 as a negative regulator of osteoblast differentiation downstream of miR-133b, revealing a role outside the nervous system.\",\n      \"evidence\": \"Gain- and loss-of-function with miR-133b and GNB4 overexpression in hFOB 1.19 osteoblast cells\",\n      \"pmids\": [\"33687637\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No direct luciferase reporter or CLIP confirmation of miR-133b binding to GNB4 mRNA\",\n        \"Mechanism by which GNB4 suppresses osteoblast differentiation markers is uncharacterized\",\n        \"Single cell line without in vivo validation\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Demonstrating that H. pylori/NF-κB/TET1-driven promoter demethylation induces GNB4 expression, which activates Hippo-YAP1 signaling, established a complete epigenetic-to-oncogenic cascade in gastric cancer.\",\n      \"evidence\": \"Co-immunoprecipitation, ChIP, methylation-specific PCR, pyrosequencing, gain/loss-of-function assays, and xenograft models in gastric cancer cells\",\n      \"pmids\": [\"37016382\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct biochemical mechanism by which GNB4 activates YAP1 (e.g., kinase cascade intermediates) is not resolved\",\n        \"Whether GNB4's role in YAP1 activation requires canonical Gβγ complex formation is unknown\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identification of circRREB1 as a direct GNB4-binding RNA that activates Erk1/2 signaling revealed a non-canonical regulatory input to Gβ4 function in breast cancer.\",\n      \"evidence\": \"RNA pull-down, mass spectrometry, RIP, and functional rescue experiments in breast cancer cells\",\n      \"pmids\": [\"38617926\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Binding interface between circRREB1 and GNB4 protein is not mapped\",\n        \"Whether circRREB1 binding alters GNB4's interaction with Gα or Gγ subunits is untested\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Placing GNB4 upstream of the cGAS-STING pyroptosis axis in glioma addressed whether GNB4 silencing has tumor-suppressive consequences via innate immune activation.\",\n      \"evidence\": \"siRNA knockdown with pharmacological inhibitor rescue of pyroptosis and cGAS-STING in glioma cell lines\",\n      \"pmids\": [\"38814382\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Pathway placement relies on pharmacological inhibitors without genetic epistasis or direct biochemical interaction data\",\n        \"Mechanism by which GNB4 suppresses cGAS-STING is entirely unknown\",\n        \"No in vivo validation\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Structural mapping of CMT-associated GNB4 variants to a spatial cluster within the WD40 domain reinforced the functional importance of this region for peripheral nerve signaling.\",\n      \"evidence\": \"Computational 3D variant mapping and clinical segregation analysis in CMT patients\",\n      \"pmids\": [\"41164122\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"New variants lack in vitro functional validation\",\n        \"How WD40 domain disruption specifically impairs Schwann cell biology is not established\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The direct biochemical mechanism by which GNB4 activates YAP1, Erk1/2, and suppresses cGAS-STING — and whether these involve canonical Gβγ effector interactions or novel modalities — remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No reconstituted biochemical system has tested GNB4 effector activation\",\n        \"Gγ subunit partners of GNB4 in any tissue context are unidentified\",\n        \"No structural or biophysical data on GNB4 interactions with downstream signaling components\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"YAP1\",\n      \"circRREB1\",\n      \"TET1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"GNB4 encodes guanine nucleotide-binding protein subunit beta-4 (Gβ4), a WD40 repeat-containing scaffold that forms obligate Gβγ dimers and participates in heterotrimeric G protein signaling with combinatorial selectivity determined by specific Gαi–Gβ pairings at GPCRs such as α2-adrenergic and bradykinin receptors [PMID:16371464, PMID:23434117]. Missense mutations clustering within the WD40 domain impair GPCR signaling and cause autosomal dominant Charcot-Marie-Tooth neuropathy with mixed demyelinating and axonal features [PMID:23434117, PMID:34071515, PMID:41164122]. In cancer contexts, GNB4 expression is upregulated by NF-κB–TET1-mediated promoter demethylation to activate Hippo-YAP1 oncogenic signaling in gastric cancer, suppresses cGAS-STING-dependent pyroptosis in glioma, and interacts with circRREB1 to drive Erk1/2 signaling in breast cancer [PMID:37016382, PMID:38814382, PMID:38617926]. GNB4 also functions as a negative regulator of osteoblast differentiation downstream of miR-133b [PMID:33687637].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Establishing that GNB4 belongs to the Gβ gene family encoding conserved WD40-repeat scaffolds provided the foundational framework for understanding its role in heterotrimeric G protein signaling.\",\n      \"evidence\": \"Genomic sequence and phylogenetic analysis of the G protein subunit gene families\",\n      \"pmids\": [\"10644457\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No isoform-specific functional data for Gβ4 itself\", \"Expression pattern of GNB4 across tissues not determined\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Demonstrating that Gβ subunits can be phosphorylated at His-266 by NDPK B to relay high-energy phosphate to GDP revealed a non-canonical, GPCR-independent mechanism of G protein activation potentially applicable to Gβ4.\",\n      \"evidence\": \"Biochemical enrichment, co-immunoprecipitation, thiophosphorylation with radiolabeled GTPγS, and peptide sequencing on purified Gβγ; primarily shown for Gβ1\",\n      \"pmids\": [\"12486123\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct demonstration on Gβ4 specifically was not performed\", \"Physiological relevance of His-266 phosphorylation in vivo remains unresolved\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Live-cell FRET experiments revealed that Gβ4 couples with Gαi1, Gαi2, or Gαi3 to form functionally distinct heterotrimers at α2-adrenergic receptors, establishing that GPCR signaling specificity arises from combinatorial Gα–Gβ pairing rather than individual subunit identity.\",\n      \"evidence\": \"FRET between Gαi-YFP and CFP-Gβ chimeras in HeLa cells with siRNA knockdown of receptor subtypes\",\n      \"pmids\": [\"16371464\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether combinatorial selectivity extends to other GPCR families was not tested\", \"Downstream effector specificity of Gβ4-containing heterotrimers not characterized\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"The discovery that GNB4 missense mutations (p.Gly53Asp, p.Lys89Glu) cause dominant intermediate CMT neuropathy and impair bradykinin-induced GPCR signaling established GNB4 as a disease gene and linked its WD40-mediated signaling function to peripheral nerve biology.\",\n      \"evidence\": \"Genome-wide linkage, exome sequencing, familial segregation, in vitro GPCR signaling assays with wild-type vs. mutant Gβ4, immunohistochemistry on sural nerve\",\n      \"pmids\": [\"23434117\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which impaired Gβ4 signaling leads to neuropathy (axonal vs. Schwann cell-autonomous) not resolved\", \"Crystal structure of mutant Gβ4 not available\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identification of a de novo GNB4 mutation (p.Lys57Glu) in severe CMT confirmed that pathogenic GNB4 variants arise independently and are not merely inherited segregating variants.\",\n      \"evidence\": \"Whole exome sequencing with Sanger validation in a family trio\",\n      \"pmids\": [\"27908631\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No functional assay performed for this specific variant\", \"Genotype-phenotype correlations for disease severity remain poorly defined\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"A novel pathogenic variant (p.Gln220Arg) in exon 8 placed the disease-associated mutation spectrum firmly within the WD40 repeat domain, reinforcing the structural importance of this domain for Gβ4 function.\",\n      \"evidence\": \"Exome sequencing with familial segregation; absence in 502 controls and ExAC\",\n      \"pmids\": [\"28642160\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vitro functional validation of p.Gln220Arg\", \"Structure-function relationship of specific WD40 blades to signaling not dissected\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrating that certain GNB4 mutations produce demyelinating rather than purely intermediate neuropathy, with sural nerve histopathology showing onion bulb formation, resolved that the disease mechanism involves a prominent Schwann cell-autonomous demyelinating component.\",\n      \"evidence\": \"Whole exome sequencing, nerve conduction studies, sural nerve biopsy with histopathology, and lower extremity MRI\",\n      \"pmids\": [\"34071515\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which Gβ4 loss-of-function specifically causes demyelination not elucidated\", \"Animal model recapitulating GNB4-CMT not established\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identifying GNB4 as a direct target of miR-133b whose overexpression reverses osteoblast differentiation revealed a non-neuronal, non-canonical role for Gβ4 as a negative regulator of osteogenic commitment.\",\n      \"evidence\": \"miRNA target validation, gain/loss-of-function experiments, Western blot and qRT-PCR for differentiation markers in hFOB 1.19 cells\",\n      \"pmids\": [\"33687637\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Downstream signaling pathway by which GNB4 suppresses osteoblast differentiation unknown\", \"Single cell line, no in vivo bone formation data\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Tracing GNB4 upregulation to H. pylori-driven NF-κB–TET1 promoter demethylation and its downstream activation of the Hippo-YAP1 pathway established a complete mechanistic axis through which GNB4 drives gastric cancer oncogenesis.\",\n      \"evidence\": \"Methylation-specific PCR, pyrosequencing, ChIP of TET1 on GNB4 promoter, Co-IP, functional assays (CCK-8, transwell, colony formation), xenograft mouse model\",\n      \"pmids\": [\"37016382\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How Gβ4 protein biochemically activates Hippo-YAP1 (direct interaction or intermediate effectors) not resolved\", \"Whether this pathway operates in other H. pylori-associated malignancies untested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Showing that GNB4 silencing activates cGAS-STING-mediated pyroptosis in glioma, reversible by STING inhibition, placed Gβ4 as an upstream suppressor of innate immune sensing in a second cancer type.\",\n      \"evidence\": \"siRNA knockdown, CCK-8, transwell, Western blot for pyroptosis markers, ELISA, cGAS-STING inhibitor rescue in glioma cell lines\",\n      \"pmids\": [\"38814382\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Biochemical mechanism linking Gβ4 to cGAS-STING suppression unknown\", \"No in vivo validation\", \"Single study, not independently confirmed\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Discovery that circRREB1 physically binds GNB4 protein to activate Erk1/2 signaling in breast cancer revealed a non-canonical RNA-protein interaction mode for Gβ4 distinct from classical Gβγ heterotrimer function.\",\n      \"evidence\": \"RNA pull-down with mass spectrometry, RIP, FISH, rescue experiments, in vivo tumor models in breast cancer cells\",\n      \"pmids\": [\"38617926\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis for circRREB1-Gβ4 interaction undetermined\", \"Whether circRNA binding competes with Gγ dimerization unknown\", \"Single study\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"3D structural mapping of all known pathogenic GNB4 variants demonstrated spatial clustering on the Gβ4 WD40 propeller, suggesting a shared structural mechanism of disruption at a functional interface.\",\n      \"evidence\": \"Whole exome sequencing, electrophysiology, ACMG reclassification, and 3D protein structural mapping\",\n      \"pmids\": [\"41164122\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No experimental structure of Gβ4 bound to Gα or GPCR with mutants modeled\", \"Functional consequence of clustering (e.g., loss of Gα binding surface) not biochemically tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The biochemical mechanism by which Gβ4 WD40 domain mutations specifically cause peripheral nerve demyelination, and how Gβ4 activates Hippo-YAP1 or suppresses cGAS-STING in cancer, remain major unresolved questions.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No Gβ4-specific crystal or cryo-EM structure available\", \"No animal model recapitulating GNB4-CMT neuropathy\", \"Biochemical link between Gβ4 and non-canonical signaling pathways (YAP1, cGAS-STING, Erk1/2 via circRNA) not mechanistically resolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 2, 3]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [2, 3, 8, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [2, 8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 3, 8, 9, 10]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [3, 4, 5, 6, 11]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [9]}\n    ],\n    \"complexes\": [\n      \"Heterotrimeric G protein (Gαβγ)\"\n    ],\n    \"partners\": [\n      \"GNAI1\",\n      \"GNAI2\",\n      \"GNAI3\",\n      \"YAP1\",\n      \"TET1\",\n      \"CGAS\",\n      \"STING1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}