{"gene":"RIC8B","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":2005,"finding":"Ric-8B interacts with Gαolf (identified by yeast two-hybrid) and potentiates Gαolf-dependent cAMP accumulation in HEK293 cells, demonstrating it functions as a GEF activator in the olfactory signal transduction pathway.","method":"Yeast two-hybrid, cAMP accumulation assay in HEK293 cells","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid interaction plus functional cell-based assay, single lab, two orthogonal methods","pmids":["15829631"],"is_preprint":false},{"year":2006,"finding":"Ric-8B promotes functional heterologous expression of odorant receptors (ORs) on the cell surface and enhances accumulation of Gαolf at the cell periphery, suggesting it enables OR coupling to Gαolf.","method":"Heterologous expression assay, cell surface receptor expression, fluorescence/immunolocalization","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — functional expression assay plus localization, single lab, replicated finding across two papers from same group","pmids":["16754875"],"is_preprint":false},{"year":2008,"finding":"Ric-8B physically interacts with Gγ13 (in addition to Gαolf) and co-localizes with Gαolf, Gβ1, and Gγ13 in cilia of olfactory sensory neurons; Ric-8B interaction with Gαolf is nucleotide-dependent, consistent with a GEF role.","method":"Co-immunoprecipitation, immunofluorescence localization in olfactory cilia, nucleotide-dependent binding assay","journal":"Molecular and cellular neurosciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP plus localization plus nucleotide-dependent binding, single lab, multiple orthogonal methods","pmids":["18462949"],"is_preprint":false},{"year":2010,"finding":"Ric-8B stabilizes Gαs protein by inhibiting its ubiquitination; Ric-8B knockdown reduces Gαs protein (not mRNA), overexpression increases it, and Ric-8B binding to Gαs is required for this protective effect since splicing variants that cannot bind Gαs fail to inhibit ubiquitination.","method":"siRNA knockdown, overexpression, ubiquitination assay, Gαs protein/mRNA quantification","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function and gain-of-function plus mechanistic ubiquitination assay and binding-deficient mutant controls, single lab","pmids":["20133939"],"is_preprint":false},{"year":2011,"finding":"Purified Ric-8B isoforms (full-length and Δ9) act as GDP release factors/GEFs for Gα subunits: Ric-8BFL stimulates GTPγS binding to Gαs, Gαq, Gα13, and Gαolf; elevates Vmax of Gαs GTP hydrolysis; and the reaction is GTP-dependent, requiring near-Km GTP to release the tight Ric-8B·nucleotide-free Gα intermediate.","method":"In vitro GEF assay (GTPγS binding), Michaelis-Menten kinetics of GTP hydrolysis, Co-IP with endogenous Gαs in HeLa cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted in vitro GEF assay with purified proteins, kinetic characterization, and cell-based Co-IP, single lab but multiple orthogonal methods with rigorous biochemical controls","pmids":["21467038"],"is_preprint":false},{"year":2011,"finding":"Ric-8B functions as a molecular chaperone for Gα subunit biosynthesis: Ric-8B knockout ES cells show substantially reduced Gαs protein (without reduced mRNA), indicating Ric-8B is required for maintaining steady-state Gαs abundance.","method":"Ric-8B knockout ES cells derived from blastocysts, Western blot for Gα protein levels, RT-PCR for mRNA levels","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout with protein/mRNA quantification, replicated across Ric-8A and Ric-8B knockouts in same study, multiple G protein subunits tested","pmids":["22114146"],"is_preprint":false},{"year":2013,"finding":"Ric-8A folds nascent Gα subunits during translation; in Ric-8A-depleted rabbit reticulocyte lysate, Gαi, Gαq, and Gα13 (but not Gαs) are improperly folded (trypsin-sensitive). In wheat germ extract (no endogenous Ric-8), Gαq forms aggregates unless Ric-8A is supplemented, whereupon it forms a ~100 kDa Ric-8A:Gαq heterodimer that releases functional Gαq-GTPγS upon GTP addition. This demonstrates the molecular chaperoning function of Ric-8 in folding nascent Gα subunits.","method":"Cell-free translation (rabbit reticulocyte lysate and wheat germ extract), immunodepletion, limited trypsinolysis protection assay, gel filtration, GTPγS binding","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with immunodepletion and add-back, multiple orthogonal methods (trypsin protection, gel filtration, GTPγS binding), single lab with rigorous controls","pmids":["23431197"],"is_preprint":false},{"year":2013,"finding":"In cardiac myocytes, Gαq signaling promotes ubiquitination and degradation of Gαs; co-expression of Ric-8B cancels Gαq-induced Gαs ubiquitination and restores cAMP accumulation. In vitro, Gαq competes with Gαs for binding to Ric-8B, defining a crosstalk mechanism between Gq and Gs pathways mediated by Ric-8B.","method":"Ubiquitination assay in neonatal rat cardiomyocytes, cAMP accumulation assay, in vitro competitive binding assay","journal":"Genes to cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-based functional assay plus in vitro competition binding, single lab, two orthogonal methods","pmids":["24134321"],"is_preprint":false},{"year":2017,"finding":"Conditional deletion of Ric-8b specifically in olfactory sensory neurons (OMP-Cre) eliminates Gαolf protein expression in the olfactory epithelium, reduces the mature olfactory sensory neuron layer, increases neuronal cell death, and causes impaired olfactory-guided behavior in mice.","method":"Conditional knockout mouse (OMP-Cre × Ric-8b floxed), Western blot, immunohistochemistry, behavioral testing","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — tissue-specific genetic knockout with molecular (Gαolf protein loss), cellular (neuronal death), and behavioral phenotypes, multiple orthogonal readouts","pmids":["29118104"],"is_preprint":false},{"year":2020,"finding":"Ric-8B hypomorphic mutation in mice reduces mTORC2 activity, as shown by decreased phosphorylation of Akt at Ser473 in mutant embryos and in cultured cells with Ric-8B knockdown, revealing an unexpected role for Ric-8B in mTORC2 regulation.","method":"Ric-8B hypomorphic mouse model, phospho-Akt (Ser473) western blot, siRNA knockdown in cell lines, RNA-seq","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic mouse model plus cell-based knockdown, consistent phenotype across two systems, single lab","pmids":["32392211"],"is_preprint":false},{"year":2023,"finding":"Cryo-EM structures of Ric-8B in complex with Gαs and Gαolf revealed that Ric-8B accommodates the Gα C-terminal α5 helix in a concave pocket formed by its α-helical repeat elements and distinctly contacts an extended loop unique to Gαs/olf proteins, explaining Ric-8B isoform specificity for Gαs/olf versus Ric-8A specificity for Gαi/o, Gα12/13, and Gαq/11.","method":"Cryo-EM structure determination, thermal stability assays, cell-based Gαolf folding assay","journal":"Structure","confidence":"High","confidence_rationale":"Tier 1 / Strong — atomic-resolution cryo-EM structures of two complexes plus functional validation with thermal stability and cell-based folding assays, multiple orthogonal methods","pmids":["36931277"],"is_preprint":false},{"year":2024,"finding":"Pathogenic GNAO1 encephalopathy mutations in Gαo cause neomorphic gain-of-interaction with Ric-8B (normally only responsible for Gαs/olf), redistributing Ric-8B from cytoplasm to Golgi and imbalancing neuronal G protein signaling networks; the strength of Gαo-Ric-8B interaction correlates with disease severity.","method":"Co-immunoprecipitation, subcellular localization imaging, GTP binding/hydrolysis assays, functional characterization of >80 Gαo mutants","journal":"The Journal of clinical investigation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus localization plus biochemical assays across many mutants, single study but extensive characterization","pmids":["38874642"],"is_preprint":false},{"year":2024,"finding":"Conditional deletion of Ric-8b in adult mouse cardiac tissue leads to severely reduced contractility, cardiac fibrosis, apoptosis, loss of β-adrenergic L-type calcium channel activation, and downregulation of myosin light chain 2 phosphopeptides. FRET-based assays confirmed selective Ric-8b interaction with Gαs, and conditional Gαs (Gnas) deletion produced an equivalent cardiac phenotype.","method":"Conditional cardiac knockout mouse, echocardiography, histology, RNA-seq, phosphoproteomics, FRET-based interaction assay, parallel Gnas conditional knockout","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout with multiple orthogonal phenotypic readouts plus FRET interaction assay plus epistasis via parallel Gαs knockout producing equivalent phenotype","pmids":["38879012"],"is_preprint":false},{"year":2026,"finding":"RIC8B variant 4 (v4), which lacks the C-terminal cradle loop helix (CLH) domain, suppresses odorant-induced cAMP responses, while variant 1 (full-length) supports OR signaling. AlphaFold3 modeling suggests v4 cannot form hydrogen bonds with Gαs via the CLH domain, potentially producing a dominant-negative misfolded Gαs.","method":"HEK293T heterologous expression, odorant-induced cAMP assay, AlphaFold3 structural prediction","journal":"Bioscience, biotechnology, and biochemistry","confidence":"Low","confidence_rationale":"Tier 3 / Weak — functional cell assay with dominant-negative variant but structural explanation relies on computational prediction only, single lab, single method for mechanism","pmids":["41665873"],"is_preprint":false},{"year":2011,"finding":"The Ric-8B gene promoter is repressed during osteoblast differentiation by the transcription factor C/EBPβ (LAP* isoform) and by the SWI/SNF chromatin-remodeling complex; C/EBPβ knockdown increases endogenous Ric-8B transcription; nucleosome repositioning accompanies repression.","method":"Promoter-luciferase assay, siRNA knockdown, ChIP, nucleosome positioning assay in osteoblastic cells","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (luciferase, siRNA, ChIP, nucleosome analysis), single lab","pmids":["21606199"],"is_preprint":false},{"year":2016,"finding":"CREB1 binds proximal CRE sites in the human RIC8B gene promoter (confirmed by ChIP in neuroblastoma cells) and positively regulates RIC8B transcriptional activity, while C/EBPβ binds distal C/EBP sites; luciferase assays identified CRE sites as the dominant elements for basal transcriptional activity.","method":"Luciferase reporter assay, ChIP, protein-DNA interaction (EMSA-type) analysis","journal":"Journal of cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus functional reporter assay, single lab, two orthogonal methods","pmids":["26729411"],"is_preprint":false}],"current_model":"RIC8B is a molecular chaperone and non-receptor guanine nucleotide exchange factor (GEF) that selectively binds and folds nascent Gαs/olf subunits, maintaining their steady-state abundance by protecting them from ubiquitin-mediated degradation; it also amplifies Gαs/olf-dependent signaling (cAMP production, odorant receptor function, cardiac β-adrenergic responses) and its cryo-EM structures with Gαs and Gαolf reveal that isoform specificity is conferred by contacts with the Gα C-terminal α5 helix and an extended loop unique to Gαs/olf proteins."},"narrative":{"mechanistic_narrative":"RIC8B is a molecular chaperone and non-receptor guanine nucleotide exchange factor (GEF) that controls the biosynthesis, folding, and steady-state abundance of Gαs/olf-type G protein α subunits and thereby amplifies Gαs/olf-dependent signaling [PMID:15829631, PMID:21467038, PMID:22114146]. As a GEF, purified Ric-8B stimulates GDP release and GTPγS binding on Gαs and Gαolf in a GTP-dependent reaction, forming a tight nucleotide-free intermediate that is resolved by near-Km GTP [PMID:21467038], and it folds nascent Gα subunits during translation into properly folded, functional species [PMID:23431197]. Independently of nucleotide exchange, Ric-8B maintains Gαs protein levels by binding it and inhibiting its ubiquitination, such that loss of Ric-8B reduces Gαs protein without affecting mRNA [PMID:20133939, PMID:22114146]; this protective binding also mediates Gq–Gs crosstalk, because Gαq competes with Gαs for Ric-8B and Ric-8B can cancel Gαq-induced Gαs degradation [PMID:24134321]. Physiologically, Ric-8B is required for olfactory signal transduction—enabling odorant receptor surface expression and ciliary Gαolf accumulation [PMID:16754875, PMID:18462949], with conditional deletion in olfactory sensory neurons abolishing Gαolf and impairing olfaction [PMID:29118104]—and for cardiac β-adrenergic responsiveness, where cardiac deletion phenocopies Gαs loss [PMID:38879012]. Cryo-EM structures of Ric-8B bound to Gαs and Gαolf show that it cradles the Gα C-terminal α5 helix in a concave α-helical-repeat pocket and contacts an extended loop unique to Gαs/olf, accounting for its isoform selectivity [PMID:36931277]. RIC8B transcription is regulated through promoter CRE and C/EBP elements by CREB1 and C/EBPβ [PMID:21606199, PMID:26729411].","teleology":[{"year":2005,"claim":"Established the first molecular partner and function for Ric-8B by showing it engages Gαolf and enhances downstream signaling, placing it in the olfactory transduction pathway.","evidence":"Yeast two-hybrid interaction and cAMP accumulation assay in HEK293 cells","pmids":["15829631"],"confidence":"Medium","gaps":["Did not establish whether the interaction is direct GEF activity or indirect","No structural or kinetic basis for the interaction","Limited to a heterologous cell context"]},{"year":2006,"claim":"Showed Ric-8B has a cell-biological role in receptor coupling by promoting functional odorant receptor surface expression and peripheral Gαolf accumulation, linking it to OR–G protein coupling.","evidence":"Heterologous expression and immunolocalization assays","pmids":["16754875"],"confidence":"Medium","gaps":["Mechanism connecting Ric-8B to OR trafficking unresolved","Did not separate chaperone from GEF contributions","Heterologous cells, not native olfactory neurons"]},{"year":2008,"claim":"Defined the native localization and binding properties of Ric-8B, showing ciliary co-localization with the olfactory heterotrimeric G protein and nucleotide-dependent Gαolf binding consistent with a GEF.","evidence":"Co-immunoprecipitation, olfactory cilia immunofluorescence, nucleotide-dependent binding assay","pmids":["18462949"],"confidence":"Medium","gaps":["Did not biochemically demonstrate GEF catalysis","Functional significance of Gγ13 interaction unclear","No in vivo loss-of-function"]},{"year":2010,"claim":"Revealed a degradation-protective function distinct from signaling: Ric-8B binding stabilizes Gαs protein by inhibiting its ubiquitination, with binding-deficient splice variants failing to protect.","evidence":"siRNA knockdown, overexpression, ubiquitination assay, protein/mRNA quantification with binding-deficient mutants","pmids":["20133939"],"confidence":"Medium","gaps":["Ubiquitin ligase responsible for Gαs degradation not identified","Did not separate chaperone folding from stabilization mechanistically","Single cell system"]},{"year":2011,"claim":"Demonstrated direct GEF catalysis and chaperone-dependent biosynthesis: purified Ric-8B drives GDP release on multiple Gα subunits via a GTP-dependent mechanism, and genetic knockout reduces steady-state Gαs protein without lowering mRNA.","evidence":"In vitro GEF/GTPγS binding assays with purified protein and Michaelis-Menten kinetics; Ric-8B knockout ES cells with Western blot and RT-PCR","pmids":["21467038","22114146"],"confidence":"High","gaps":["Structural basis of nucleotide release not yet defined","Relationship between in vitro broad Gα activity and in vivo isoform specificity unresolved","Whether GEF and chaperone activities are mechanistically separable not addressed"]},{"year":2011,"claim":"Identified transcriptional repression of the Ric-8B promoter during osteoblast differentiation by C/EBPβ and SWI/SNF, establishing chromatin-level control of Ric-8B expression.","evidence":"Promoter-luciferase, siRNA knockdown, ChIP, and nucleosome positioning assays in osteoblastic cells","pmids":["21606199"],"confidence":"Medium","gaps":["Functional consequence of Ric-8B repression for osteoblast biology not established","Restricted to one cell lineage"]},{"year":2013,"claim":"Resolved the chaperone mechanism by showing Ric-8 folds nascent Gα subunits co-translationally, preventing aggregation and yielding functional GTP-loadable protein.","evidence":"Cell-free translation, immunodepletion/add-back, trypsinolysis protection, gel filtration, GTPγS binding","pmids":["23431197"],"confidence":"High","gaps":["Study focused on Ric-8A; direct demonstration of Ric-8B folding Gαs/olf co-translationally not shown here","How chaperone handoff to membrane occurs unknown"]},{"year":2013,"claim":"Established Ric-8B as a node of Gq–Gs crosstalk by showing Gαq competes for Ric-8B and Ric-8B reverses Gαq-induced Gαs degradation in cardiomyocytes.","evidence":"Ubiquitination and cAMP assays in neonatal rat cardiomyocytes plus in vitro competitive binding","pmids":["24134321"],"confidence":"Medium","gaps":["Stoichiometry and regulation of competition in vivo not defined","Physiological context of crosstalk under pathological signaling unaddressed"]},{"year":2017,"claim":"Provided in vivo proof that Ric-8B is required for olfactory function through maintenance of Gαolf, with neuronal loss and behavioral deficits upon conditional deletion.","evidence":"OMP-Cre conditional knockout mouse with Western blot, immunohistochemistry, and behavioral testing","pmids":["29118104"],"confidence":"High","gaps":["Cause of neuronal death (signaling loss vs. unfolded Gα stress) not dissected","Did not separate chaperone from GEF role in vivo"]},{"year":2020,"claim":"Uncovered an unexpected link between Ric-8B and mTORC2 signaling, broadening its functional scope beyond Gαs/olf biology.","evidence":"Ric-8B hypomorphic mouse and cell knockdown with phospho-Akt(Ser473) Western blot and RNA-seq","pmids":["32392211"],"confidence":"Medium","gaps":["Direct molecular connection between Ric-8B and mTORC2 not established","Whether effect is G protein-dependent unknown"]},{"year":2023,"claim":"Defined the structural basis of isoform selectivity, showing Ric-8B cradles the Gα α5 helix and uniquely contacts a Gαs/olf-specific loop, distinguishing it from Ric-8A specificity.","evidence":"Cryo-EM of Ric-8B:Gαs and Ric-8B:Gαolf complexes with thermal stability and cell-based folding assays","pmids":["36931277"],"confidence":"High","gaps":["Structures capture chaperone/intermediate states; coupling to catalytic GDP release cycle not fully resolved","Dynamics of substrate handoff not captured"]},{"year":2024,"claim":"Showed that disease mutations in another Gα (Gαo) create a neomorphic gain-of-interaction with Ric-8B, redistributing it to the Golgi and disrupting neuronal G protein networks in a severity-correlated manner.","evidence":"Co-IP, subcellular localization imaging, GTP binding/hydrolysis assays across >80 Gαo mutants","pmids":["38874642"],"confidence":"Medium","gaps":["Causal contribution of Ric-8B sequestration to neuronal dysfunction not demonstrated in vivo","Mechanism of Golgi redistribution unresolved"]},{"year":2024,"claim":"Demonstrated a non-olfactory physiological requirement: cardiac Ric-8B deletion selectively impairs Gαs-dependent β-adrenergic signaling and contractility, phenocopied by Gαs deletion.","evidence":"Conditional cardiac knockout with echocardiography, histology, phosphoproteomics, FRET interaction assay, and parallel Gnas knockout","pmids":["38879012"],"confidence":"High","gaps":["Whether cardiac phenotype reflects loss of chaperone vs. GEF activity not dissected","Relevance to human cardiac disease not established"]},{"year":2026,"claim":"Indicated that a RIC8B splice variant lacking the cradle loop helix domain acts as a dominant-negative suppressor of OR cAMP signaling, implicating the CLH domain in productive Gαs engagement.","evidence":"HEK293T odorant-induced cAMP assay with variant 4 and AlphaFold3 modeling","pmids":["41665873"],"confidence":"Low","gaps":["Dominant-negative misfolding mechanism rests on computational prediction only","No biochemical or structural validation of the CLH contact model","Single lab, single assay"]},{"year":null,"claim":"How Ric-8B's distinct activities—co-translational folding, GEF catalysis, and ubiquitination protection—are mechanistically partitioned and coordinated across the Gα life cycle in vivo remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No mechanism separating chaperone from GEF function in living cells","Identity of the ubiquitin ligase acting on Gαs unknown","Molecular basis of the Ric-8B–mTORC2 link undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[4,0]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[4,3,7]},{"term_id":"GO:0044183","term_label":"protein folding chaperone","supporting_discovery_ids":[5,6,10]}],"localization":[{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[2]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[11]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[11]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,4,8]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[3,5,6]}],"complexes":[],"partners":["GNAL","GNAS","GNAQ","GNB1","GNG13","GNAO1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NVN3","full_name":"Chaperone Ric-8B","aliases":["Brain synembryn","hSyn","Synembryn-B"],"length_aa":520,"mass_kda":58.8,"function":"Chaperone that specifically binds and folds nascent G(s) G-alpha proteins (GNAS and GNAL) prior to G protein heterotrimer formation, promoting their association with the plasma membrane (By similarity). Also acts as a guanine nucleotide exchange factor (GEF) for G(s) proteins by stimulating exchange of bound GDP for free GTP (By similarity). Acts as an important component for odorant signal transduction by mediating GNAL (G(olf)-alpha) folding, thereby promoting-dependent cAMP accumulation in olfactory sensory neurons (By similarity)","subcellular_location":"Cytoplasm, cell cortex","url":"https://www.uniprot.org/uniprotkb/Q9NVN3/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RIC8B","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/RIC8B","total_profiled":1310},"omim":[{"mim_id":"609147","title":"RIC8 GUANINE NUCLEOTIDE EXCHANGE FACTOR B; RIC8B","url":"https://www.omim.org/entry/609147"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"},{"location":"Plasma membrane","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/RIC8B"},"hgnc":{"alias_symbol":["FLJ10620","hSyn","RIC8"],"prev_symbol":[]},"alphafold":{"accession":"Q9NVN3","domains":[{"cath_id":"1.25.10","chopping":"1-138","consensus_level":"medium","plddt":92.6964,"start":1,"end":138},{"cath_id":"-","chopping":"297-312_320-480","consensus_level":"medium","plddt":86.3685,"start":297,"end":480}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NVN3","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NVN3-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NVN3-F1-predicted_aligned_error_v6.png","plddt_mean":86.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RIC8B","jax_strain_url":"https://www.jax.org/strain/search?query=RIC8B"},"sequence":{"accession":"Q9NVN3","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NVN3.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NVN3/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NVN3"}},"corpus_meta":[{"pmid":"15479639","id":"PMC_15479639","title":"RIC-8 is required for GPR-1/2-dependent Galpha function during asymmetric division of C. elegans embryos.","date":"2004","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/15479639","citation_count":161,"is_preprint":false},{"pmid":"10985349","id":"PMC_10985349","title":"RIC-8 (Synembryn): a novel conserved protein that is required for G(q)alpha signaling in the C. elegans nervous system.","date":"2000","source":"Neuron","url":"https://pubmed.ncbi.nlm.nih.gov/10985349","citation_count":118,"is_preprint":false},{"pmid":"16228010","id":"PMC_16228010","title":"Drosophila Ric-8 regulates Galphai cortical localization to promote Galphai-dependent planar orientation of the mitotic spindle during asymmetric cell division.","date":"2005","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/16228010","citation_count":114,"is_preprint":false},{"pmid":"11102364","id":"PMC_11102364","title":"A role for RIC-8 (Synembryn) and GOA-1 (G(o)alpha) in regulating a subset of centrosome movements during early embryogenesis in Caenorhabditis elegans.","date":"2000","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/11102364","citation_count":107,"is_preprint":false},{"pmid":"16228012","id":"PMC_16228012","title":"Ric-8 controls Drosophila neural progenitor asymmetric division by regulating heterotrimeric G proteins.","date":"2005","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/16228012","citation_count":106,"is_preprint":false},{"pmid":"22114146","id":"PMC_22114146","title":"Ric-8 proteins are molecular chaperones that direct nascent G protein α subunit membrane association.","date":"2011","source":"Science signaling","url":"https://pubmed.ncbi.nlm.nih.gov/22114146","citation_count":104,"is_preprint":false},{"pmid":"16228011","id":"PMC_16228011","title":"Drosophila Ric-8 is essential for plasma-membrane localization of heterotrimeric G proteins.","date":"2005","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/16228011","citation_count":99,"is_preprint":false},{"pmid":"15489510","id":"PMC_15489510","title":"Mutations that rescue the paralysis of Caenorhabditis elegans ric-8 (synembryn) mutants activate the G alpha(s) pathway and define a third major branch of the synaptic signaling network.","date":"2004","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/15489510","citation_count":99,"is_preprint":false},{"pmid":"15829631","id":"PMC_15829631","title":"Ric-8B, an olfactory putative GTP exchange factor, amplifies signal transduction through the olfactory-specific G-protein Galphaolf.","date":"2005","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/15829631","citation_count":90,"is_preprint":false},{"pmid":"16754875","id":"PMC_16754875","title":"Ric-8B promotes functional expression of odorant receptors.","date":"2006","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/16754875","citation_count":89,"is_preprint":false},{"pmid":"15498497","id":"PMC_15498497","title":"Control of embryonic spindle positioning and Galpha activity by C. elegans RIC-8.","date":"2004","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/15498497","citation_count":83,"is_preprint":false},{"pmid":"16162648","id":"PMC_16162648","title":"Cortical localization of the Galpha protein GPA-16 requires RIC-8 function during C. elegans asymmetric cell division.","date":"2005","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/16162648","citation_count":73,"is_preprint":false},{"pmid":"23431197","id":"PMC_23431197","title":"Molecular chaperoning function of Ric-8 is to fold nascent heterotrimeric G protein α subunits.","date":"2013","source":"Proceedings of the National Academy of Sciences of the United States of 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Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid interaction plus functional cell-based assay, single lab, two orthogonal methods\",\n      \"pmids\": [\"15829631\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Ric-8B promotes functional heterologous expression of odorant receptors (ORs) on the cell surface and enhances accumulation of Gαolf at the cell periphery, suggesting it enables OR coupling to Gαolf.\",\n      \"method\": \"Heterologous expression assay, cell surface receptor expression, fluorescence/immunolocalization\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — functional expression assay plus localization, single lab, replicated finding across two papers from same group\",\n      \"pmids\": [\"16754875\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Ric-8B physically interacts with Gγ13 (in addition to Gαolf) and co-localizes with Gαolf, Gβ1, and Gγ13 in cilia of olfactory sensory neurons; Ric-8B interaction with Gαolf is nucleotide-dependent, consistent with a GEF role.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence localization in olfactory cilia, nucleotide-dependent binding assay\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP plus localization plus nucleotide-dependent binding, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"18462949\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Ric-8B stabilizes Gαs protein by inhibiting its ubiquitination; Ric-8B knockdown reduces Gαs protein (not mRNA), overexpression increases it, and Ric-8B binding to Gαs is required for this protective effect since splicing variants that cannot bind Gαs fail to inhibit ubiquitination.\",\n      \"method\": \"siRNA knockdown, overexpression, ubiquitination assay, Gαs protein/mRNA quantification\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function and gain-of-function plus mechanistic ubiquitination assay and binding-deficient mutant controls, single lab\",\n      \"pmids\": [\"20133939\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Purified Ric-8B isoforms (full-length and Δ9) act as GDP release factors/GEFs for Gα subunits: Ric-8BFL stimulates GTPγS binding to Gαs, Gαq, Gα13, and Gαolf; elevates Vmax of Gαs GTP hydrolysis; and the reaction is GTP-dependent, requiring near-Km GTP to release the tight Ric-8B·nucleotide-free Gα intermediate.\",\n      \"method\": \"In vitro GEF assay (GTPγS binding), Michaelis-Menten kinetics of GTP hydrolysis, Co-IP with endogenous Gαs in HeLa cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted in vitro GEF assay with purified proteins, kinetic characterization, and cell-based Co-IP, single lab but multiple orthogonal methods with rigorous biochemical controls\",\n      \"pmids\": [\"21467038\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Ric-8B functions as a molecular chaperone for Gα subunit biosynthesis: Ric-8B knockout ES cells show substantially reduced Gαs protein (without reduced mRNA), indicating Ric-8B is required for maintaining steady-state Gαs abundance.\",\n      \"method\": \"Ric-8B knockout ES cells derived from blastocysts, Western blot for Gα protein levels, RT-PCR for mRNA levels\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout with protein/mRNA quantification, replicated across Ric-8A and Ric-8B knockouts in same study, multiple G protein subunits tested\",\n      \"pmids\": [\"22114146\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Ric-8A folds nascent Gα subunits during translation; in Ric-8A-depleted rabbit reticulocyte lysate, Gαi, Gαq, and Gα13 (but not Gαs) are improperly folded (trypsin-sensitive). In wheat germ extract (no endogenous Ric-8), Gαq forms aggregates unless Ric-8A is supplemented, whereupon it forms a ~100 kDa Ric-8A:Gαq heterodimer that releases functional Gαq-GTPγS upon GTP addition. This demonstrates the molecular chaperoning function of Ric-8 in folding nascent Gα subunits.\",\n      \"method\": \"Cell-free translation (rabbit reticulocyte lysate and wheat germ extract), immunodepletion, limited trypsinolysis protection assay, gel filtration, GTPγS binding\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with immunodepletion and add-back, multiple orthogonal methods (trypsin protection, gel filtration, GTPγS binding), single lab with rigorous controls\",\n      \"pmids\": [\"23431197\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"In cardiac myocytes, Gαq signaling promotes ubiquitination and degradation of Gαs; co-expression of Ric-8B cancels Gαq-induced Gαs ubiquitination and restores cAMP accumulation. In vitro, Gαq competes with Gαs for binding to Ric-8B, defining a crosstalk mechanism between Gq and Gs pathways mediated by Ric-8B.\",\n      \"method\": \"Ubiquitination assay in neonatal rat cardiomyocytes, cAMP accumulation assay, in vitro competitive binding assay\",\n      \"journal\": \"Genes to cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-based functional assay plus in vitro competition binding, single lab, two orthogonal methods\",\n      \"pmids\": [\"24134321\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Conditional deletion of Ric-8b specifically in olfactory sensory neurons (OMP-Cre) eliminates Gαolf protein expression in the olfactory epithelium, reduces the mature olfactory sensory neuron layer, increases neuronal cell death, and causes impaired olfactory-guided behavior in mice.\",\n      \"method\": \"Conditional knockout mouse (OMP-Cre × Ric-8b floxed), Western blot, immunohistochemistry, behavioral testing\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — tissue-specific genetic knockout with molecular (Gαolf protein loss), cellular (neuronal death), and behavioral phenotypes, multiple orthogonal readouts\",\n      \"pmids\": [\"29118104\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Ric-8B hypomorphic mutation in mice reduces mTORC2 activity, as shown by decreased phosphorylation of Akt at Ser473 in mutant embryos and in cultured cells with Ric-8B knockdown, revealing an unexpected role for Ric-8B in mTORC2 regulation.\",\n      \"method\": \"Ric-8B hypomorphic mouse model, phospho-Akt (Ser473) western blot, siRNA knockdown in cell lines, RNA-seq\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic mouse model plus cell-based knockdown, consistent phenotype across two systems, single lab\",\n      \"pmids\": [\"32392211\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Cryo-EM structures of Ric-8B in complex with Gαs and Gαolf revealed that Ric-8B accommodates the Gα C-terminal α5 helix in a concave pocket formed by its α-helical repeat elements and distinctly contacts an extended loop unique to Gαs/olf proteins, explaining Ric-8B isoform specificity for Gαs/olf versus Ric-8A specificity for Gαi/o, Gα12/13, and Gαq/11.\",\n      \"method\": \"Cryo-EM structure determination, thermal stability assays, cell-based Gαolf folding assay\",\n      \"journal\": \"Structure\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — atomic-resolution cryo-EM structures of two complexes plus functional validation with thermal stability and cell-based folding assays, multiple orthogonal methods\",\n      \"pmids\": [\"36931277\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Pathogenic GNAO1 encephalopathy mutations in Gαo cause neomorphic gain-of-interaction with Ric-8B (normally only responsible for Gαs/olf), redistributing Ric-8B from cytoplasm to Golgi and imbalancing neuronal G protein signaling networks; the strength of Gαo-Ric-8B interaction correlates with disease severity.\",\n      \"method\": \"Co-immunoprecipitation, subcellular localization imaging, GTP binding/hydrolysis assays, functional characterization of >80 Gαo mutants\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus localization plus biochemical assays across many mutants, single study but extensive characterization\",\n      \"pmids\": [\"38874642\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Conditional deletion of Ric-8b in adult mouse cardiac tissue leads to severely reduced contractility, cardiac fibrosis, apoptosis, loss of β-adrenergic L-type calcium channel activation, and downregulation of myosin light chain 2 phosphopeptides. FRET-based assays confirmed selective Ric-8b interaction with Gαs, and conditional Gαs (Gnas) deletion produced an equivalent cardiac phenotype.\",\n      \"method\": \"Conditional cardiac knockout mouse, echocardiography, histology, RNA-seq, phosphoproteomics, FRET-based interaction assay, parallel Gnas conditional knockout\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout with multiple orthogonal phenotypic readouts plus FRET interaction assay plus epistasis via parallel Gαs knockout producing equivalent phenotype\",\n      \"pmids\": [\"38879012\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"RIC8B variant 4 (v4), which lacks the C-terminal cradle loop helix (CLH) domain, suppresses odorant-induced cAMP responses, while variant 1 (full-length) supports OR signaling. AlphaFold3 modeling suggests v4 cannot form hydrogen bonds with Gαs via the CLH domain, potentially producing a dominant-negative misfolded Gαs.\",\n      \"method\": \"HEK293T heterologous expression, odorant-induced cAMP assay, AlphaFold3 structural prediction\",\n      \"journal\": \"Bioscience, biotechnology, and biochemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — functional cell assay with dominant-negative variant but structural explanation relies on computational prediction only, single lab, single method for mechanism\",\n      \"pmids\": [\"41665873\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The Ric-8B gene promoter is repressed during osteoblast differentiation by the transcription factor C/EBPβ (LAP* isoform) and by the SWI/SNF chromatin-remodeling complex; C/EBPβ knockdown increases endogenous Ric-8B transcription; nucleosome repositioning accompanies repression.\",\n      \"method\": \"Promoter-luciferase assay, siRNA knockdown, ChIP, nucleosome positioning assay in osteoblastic cells\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (luciferase, siRNA, ChIP, nucleosome analysis), single lab\",\n      \"pmids\": [\"21606199\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"CREB1 binds proximal CRE sites in the human RIC8B gene promoter (confirmed by ChIP in neuroblastoma cells) and positively regulates RIC8B transcriptional activity, while C/EBPβ binds distal C/EBP sites; luciferase assays identified CRE sites as the dominant elements for basal transcriptional activity.\",\n      \"method\": \"Luciferase reporter assay, ChIP, protein-DNA interaction (EMSA-type) analysis\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus functional reporter assay, single lab, two orthogonal methods\",\n      \"pmids\": [\"26729411\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RIC8B is a molecular chaperone and non-receptor guanine nucleotide exchange factor (GEF) that selectively binds and folds nascent Gαs/olf subunits, maintaining their steady-state abundance by protecting them from ubiquitin-mediated degradation; it also amplifies Gαs/olf-dependent signaling (cAMP production, odorant receptor function, cardiac β-adrenergic responses) and its cryo-EM structures with Gαs and Gαolf reveal that isoform specificity is conferred by contacts with the Gα C-terminal α5 helix and an extended loop unique to Gαs/olf proteins.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RIC8B is a molecular chaperone and non-receptor guanine nucleotide exchange factor (GEF) that controls the biosynthesis, folding, and steady-state abundance of G\\u03b1s/olf-type G protein \\u03b1 subunits and thereby amplifies G\\u03b1s/olf-dependent signaling [#0, #4, #5]. As a GEF, purified Ric-8B stimulates GDP release and GTP\\u03b3S binding on G\\u03b1s and G\\u03b1olf in a GTP-dependent reaction, forming a tight nucleotide-free intermediate that is resolved by near-Km GTP [#4], and it folds nascent G\\u03b1 subunits during translation into properly folded, functional species [#6]. Independently of nucleotide exchange, Ric-8B maintains G\\u03b1s protein levels by binding it and inhibiting its ubiquitination, such that loss of Ric-8B reduces G\\u03b1s protein without affecting mRNA [#3, #5]; this protective binding also mediates Gq\\u2013Gs crosstalk, because G\\u03b1q competes with G\\u03b1s for Ric-8B and Ric-8B can cancel G\\u03b1q-induced G\\u03b1s degradation [#7]. Physiologically, Ric-8B is required for olfactory signal transduction\\u2014enabling odorant receptor surface expression and ciliary G\\u03b1olf accumulation [#1, #2], with conditional deletion in olfactory sensory neurons abolishing G\\u03b1olf and impairing olfaction [#8]\\u2014and for cardiac \\u03b2-adrenergic responsiveness, where cardiac deletion phenocopies G\\u03b1s loss [#12]. Cryo-EM structures of Ric-8B bound to G\\u03b1s and G\\u03b1olf show that it cradles the G\\u03b1 C-terminal \\u03b15 helix in a concave \\u03b1-helical-repeat pocket and contacts an extended loop unique to G\\u03b1s/olf, accounting for its isoform selectivity [#10]. RIC8B transcription is regulated through promoter CRE and C/EBP elements by CREB1 and C/EBP\\u03b2 [#14, #15].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Established the first molecular partner and function for Ric-8B by showing it engages G\\u03b1olf and enhances downstream signaling, placing it in the olfactory transduction pathway.\",\n      \"evidence\": \"Yeast two-hybrid interaction and cAMP accumulation assay in HEK293 cells\",\n      \"pmids\": [\"15829631\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Did not establish whether the interaction is direct GEF activity or indirect\", \"No structural or kinetic basis for the interaction\", \"Limited to a heterologous cell context\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Showed Ric-8B has a cell-biological role in receptor coupling by promoting functional odorant receptor surface expression and peripheral G\\u03b1olf accumulation, linking it to OR\\u2013G protein coupling.\",\n      \"evidence\": \"Heterologous expression and immunolocalization assays\",\n      \"pmids\": [\"16754875\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Mechanism connecting Ric-8B to OR trafficking unresolved\", \"Did not separate chaperone from GEF contributions\", \"Heterologous cells, not native olfactory neurons\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Defined the native localization and binding properties of Ric-8B, showing ciliary co-localization with the olfactory heterotrimeric G protein and nucleotide-dependent G\\u03b1olf binding consistent with a GEF.\",\n      \"evidence\": \"Co-immunoprecipitation, olfactory cilia immunofluorescence, nucleotide-dependent binding assay\",\n      \"pmids\": [\"18462949\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Did not biochemically demonstrate GEF catalysis\", \"Functional significance of G\\u03b313 interaction unclear\", \"No in vivo loss-of-function\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Revealed a degradation-protective function distinct from signaling: Ric-8B binding stabilizes G\\u03b1s protein by inhibiting its ubiquitination, with binding-deficient splice variants failing to protect.\",\n      \"evidence\": \"siRNA knockdown, overexpression, ubiquitination assay, protein/mRNA quantification with binding-deficient mutants\",\n      \"pmids\": [\"20133939\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Ubiquitin ligase responsible for G\\u03b1s degradation not identified\", \"Did not separate chaperone folding from stabilization mechanistically\", \"Single cell system\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Demonstrated direct GEF catalysis and chaperone-dependent biosynthesis: purified Ric-8B drives GDP release on multiple G\\u03b1 subunits via a GTP-dependent mechanism, and genetic knockout reduces steady-state G\\u03b1s protein without lowering mRNA.\",\n      \"evidence\": \"In vitro GEF/GTP\\u03b3S binding assays with purified protein and Michaelis-Menten kinetics; Ric-8B knockout ES cells with Western blot and RT-PCR\",\n      \"pmids\": [\"21467038\", \"22114146\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Structural basis of nucleotide release not yet defined\", \"Relationship between in vitro broad G\\u03b1 activity and in vivo isoform specificity unresolved\", \"Whether GEF and chaperone activities are mechanistically separable not addressed\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Identified transcriptional repression of the Ric-8B promoter during osteoblast differentiation by C/EBP\\u03b2 and SWI/SNF, establishing chromatin-level control of Ric-8B expression.\",\n      \"evidence\": \"Promoter-luciferase, siRNA knockdown, ChIP, and nucleosome positioning assays in osteoblastic cells\",\n      \"pmids\": [\"21606199\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Functional consequence of Ric-8B repression for osteoblast biology not established\", \"Restricted to one cell lineage\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Resolved the chaperone mechanism by showing Ric-8 folds nascent G\\u03b1 subunits co-translationally, preventing aggregation and yielding functional GTP-loadable protein.\",\n      \"evidence\": \"Cell-free translation, immunodepletion/add-back, trypsinolysis protection, gel filtration, GTP\\u03b3S binding\",\n      \"pmids\": [\"23431197\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Study focused on Ric-8A; direct demonstration of Ric-8B folding G\\u03b1s/olf co-translationally not shown here\", \"How chaperone handoff to membrane occurs unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Established Ric-8B as a node of Gq\\u2013Gs crosstalk by showing G\\u03b1q competes for Ric-8B and Ric-8B reverses G\\u03b1q-induced G\\u03b1s degradation in cardiomyocytes.\",\n      \"evidence\": \"Ubiquitination and cAMP assays in neonatal rat cardiomyocytes plus in vitro competitive binding\",\n      \"pmids\": [\"24134321\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Stoichiometry and regulation of competition in vivo not defined\", \"Physiological context of crosstalk under pathological signaling unaddressed\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Provided in vivo proof that Ric-8B is required for olfactory function through maintenance of G\\u03b1olf, with neuronal loss and behavioral deficits upon conditional deletion.\",\n      \"evidence\": \"OMP-Cre conditional knockout mouse with Western blot, immunohistochemistry, and behavioral testing\",\n      \"pmids\": [\"29118104\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Cause of neuronal death (signaling loss vs. unfolded G\\u03b1 stress) not dissected\", \"Did not separate chaperone from GEF role in vivo\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Uncovered an unexpected link between Ric-8B and mTORC2 signaling, broadening its functional scope beyond G\\u03b1s/olf biology.\",\n      \"evidence\": \"Ric-8B hypomorphic mouse and cell knockdown with phospho-Akt(Ser473) Western blot and RNA-seq\",\n      \"pmids\": [\"32392211\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Direct molecular connection between Ric-8B and mTORC2 not established\", \"Whether effect is G protein-dependent unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined the structural basis of isoform selectivity, showing Ric-8B cradles the G\\u03b1 \\u03b15 helix and uniquely contacts a G\\u03b1s/olf-specific loop, distinguishing it from Ric-8A specificity.\",\n      \"evidence\": \"Cryo-EM of Ric-8B:G\\u03b1s and Ric-8B:G\\u03b1olf complexes with thermal stability and cell-based folding assays\",\n      \"pmids\": [\"36931277\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Structures capture chaperone/intermediate states; coupling to catalytic GDP release cycle not fully resolved\", \"Dynamics of substrate handoff not captured\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Showed that disease mutations in another G\\u03b1 (G\\u03b1o) create a neomorphic gain-of-interaction with Ric-8B, redistributing it to the Golgi and disrupting neuronal G protein networks in a severity-correlated manner.\",\n      \"evidence\": \"Co-IP, subcellular localization imaging, GTP binding/hydrolysis assays across >80 G\\u03b1o mutants\",\n      \"pmids\": [\"38874642\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Causal contribution of Ric-8B sequestration to neuronal dysfunction not demonstrated in vivo\", \"Mechanism of Golgi redistribution unresolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Demonstrated a non-olfactory physiological requirement: cardiac Ric-8B deletion selectively impairs G\\u03b1s-dependent \\u03b2-adrenergic signaling and contractility, phenocopied by G\\u03b1s deletion.\",\n      \"evidence\": \"Conditional cardiac knockout with echocardiography, histology, phosphoproteomics, FRET interaction assay, and parallel Gnas knockout\",\n      \"pmids\": [\"38879012\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Whether cardiac phenotype reflects loss of chaperone vs. GEF activity not dissected\", \"Relevance to human cardiac disease not established\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Indicated that a RIC8B splice variant lacking the cradle loop helix domain acts as a dominant-negative suppressor of OR cAMP signaling, implicating the CLH domain in productive G\\u03b1s engagement.\",\n      \"evidence\": \"HEK293T odorant-induced cAMP assay with variant 4 and AlphaFold3 modeling\",\n      \"pmids\": [\"41665873\"],\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Dominant-negative misfolding mechanism rests on computational prediction only\", \"No biochemical or structural validation of the CLH contact model\", \"Single lab, single assay\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How Ric-8B's distinct activities\\u2014co-translational folding, GEF catalysis, and ubiquitination protection\\u2014are mechanistically partitioned and coordinated across the G\\u03b1 life cycle in vivo remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"No mechanism separating chaperone from GEF function in living cells\", \"Identity of the ubiquitin ligase acting on G\\u03b1s unknown\", \"Molecular basis of the Ric-8B\\u2013mTORC2 link undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [4, 0]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [4, 3, 7]},\n      {\"term_id\": \"GO:0044183\", \"supporting_discovery_ids\": [5, 6, 10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [11]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 4, 8]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [3, 5, 6]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"GNAL\", \"GNAS\", \"GNAQ\", \"GNB1\", \"GNG13\", \"GNAO1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}