{"gene":"KCTD5","run_date":"2026-04-28T18:30:27","timeline":{"discoveries":[{"year":2008,"finding":"KCTD5 interacts specifically with Cullin3 via its BTB domain plus additional N-terminal residues, forms oligomers through its BTB domain, and binds ubiquitinated proteins, establishing it as a putative substrate-specific adaptor for Cullin3-based E3 ubiquitin ligases. KCTD5 localizes to the cytosol of cultured cell lines.","method":"Co-immunoprecipitation, protein binding assays, N-terminal deletion mutagenesis, subcellular fractionation","journal":"The FEBS journal","confidence":"High","confidence_rationale":"Tier 2 — reciprocal interactions demonstrated with mutagenesis, replicated by multiple subsequent studies","pmids":["18573101"],"is_preprint":false},{"year":2023,"finding":"KCTD5 in pentameric form engages symmetrically with five copies of Gβγ through its C-terminal domain; the pentameric KCTD5/Cul3 E3 ligase complex simultaneously ubiquitinates five Gβγ subunits, and this ubiquitination triggers degradation of free Gβγ to negatively regulate GPCR/cAMP signaling.","method":"Cryo-electron microscopy structure determination of KCTD5-Gβγ fusion complex and KCTD7-Cul3 complex; functional cAMP signaling assays","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structure with functional validation of ubiquitination and cAMP signaling","pmids":["37450587"],"is_preprint":false},{"year":2024,"finding":"CRL3KCTD5 engages the E3 ligase ARIH1 in an E3-E3 superassembly to ubiquitylate Gβγ; the cryo-EM structure of the 5:5:5 KCTD5/CUL3NTD/Gβ1γ2 assembly reveals >60° rotational dynamics between BTB/CUL3 and CTD/Gβγ moieties, with ARIH1~ubiquitin positioned within 10 Å of Lys-23 of Gβ in priming conformations.","method":"Cryo-EM structure of pentameric complex; BRET-based interaction assays; in vitro ubiquitylation assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 — high-resolution cryo-EM with multiple orthogonal functional assays","pmids":["38625940"],"is_preprint":false},{"year":2015,"finding":"KCTD5 interacts with MCM7, ZNF711, and FAM193B, forming trimeric complexes with Cullin3; however, KCTD5/Cullin3 did not induce degradation of these partners—overexpression of KCTD5 or Cullin3 instead increased ZNF711 protein stability, suggesting a role in protein stabilization rather than degradation for some substrates.","method":"Yeast two-hybrid, co-immunoprecipitation in mammalian cells, protein stability assays","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — two orthogonal interaction methods but single lab and unexpected result not yet replicated","pmids":["26188516"],"is_preprint":false},{"year":2018,"finding":"KCTD5 physically interacts with ΔNp63α and, together with Cullin3, induces monoubiquitination of ΔNp63α, impairing its DNA-binding affinity and both its transactivation and transinhibitory activities, and reducing its pro-proliferative function.","method":"Co-immunoprecipitation, in vivo ubiquitination assay, DNA-binding (EMSA), reporter assays, proliferation assays","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods in single lab study","pmids":["29782646"],"is_preprint":false},{"year":2020,"finding":"KCTD5 binds to RhoGDI1 and increases its interaction with Cullin3; ectopic KCTD5 expression increases polyubiquitination of RhoGDI1 while KCTD5 knockdown stabilizes RhoGDI1, establishing CUL3/KCTD5 as a ubiquitin ligase complex that promotes RhoGDI1 degradation.","method":"Co-immunoprecipitation, in vivo ubiquitination assay, RNA interference knockdown, protein stability assays","journal":"Journal of microbiology and biotechnology","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal gain/loss-of-function with ubiquitination assay, single lab","pmids":["32876072"],"is_preprint":false},{"year":2020,"finding":"KCTD5 depletion (CRISPR/Cas9 and shRNA) in B16-F10 cells increases cell migration and spreading and decreases focal adhesion area via increased focal adhesion disassembly; these effects are mediated through Rac1 activity (blocked by dominant-negative Rac1) and Ca2+ signaling (KCTD5 silencing decreases serum-induced Ca2+ response, and ionomycin rescue abolishes the focal adhesion phenotype).","method":"CRISPR/Cas9 and shRNA knockdown, live-cell imaging of focal adhesion dynamics, dominant-negative Rac1 expression, Ca2+ imaging, ionomycin rescue","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods with specific pathway rescue, single lab","pmids":["33053687"],"is_preprint":false},{"year":2015,"finding":"Molecular dynamics simulations of full-length KCTD5 reveal large interdomain twisting motions pivoted by Ser150 in the hinge region between the BTB and C-terminal domains; these motions are proposed to position substrates for ubiquitination relative to the E2/E3 machinery.","method":"Molecular dynamics simulation (120 ns) of pentameric KCTD5","journal":"Journal of biomolecular structure & dynamics","confidence":"Low","confidence_rationale":"Tier 4 — computational prediction only, no experimental validation of functional role of Ser150","pmids":["26336981"],"is_preprint":false},{"year":2017,"finding":"KCTD5 is itself ubiquitinated and degraded by the proteasome; H. pylori infection impairs KCTD5 ubiquitination, and reduced KCTD5 levels increase bacterial adherence, indicating that KCTD5 ubiquitin ligase activity limits H. pylori adherence to gastric epithelial cells.","method":"shRNA knockdown, proteasome inhibitor treatment, infection adherence assays, ubiquitination assays in AGS cells","journal":"Frontiers in cellular and infection microbiology","confidence":"Medium","confidence_rationale":"Tier 2 — genetic knockdown with specific bacterial adherence phenotype and ubiquitination assays, single lab","pmids":["29114497"],"is_preprint":false},{"year":2023,"finding":"KCTD5 forms hetero-oligomeric complexes with multiple KCTD family members (including KCTD2 and KCTD17) through distinct regions of KCTD5; different regions of KCTD5 are responsible for interactions with different KCTD partners.","method":"Co-immunoprecipitation, live-cell BRET, IP-luminescence domain mapping","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2–3 — two orthogonal interaction methods with domain mapping, single lab","pmids":["37762619"],"is_preprint":false},{"year":2024,"finding":"KCTD5 stabilizes Ikaros transcription factor isoforms (IK1, IK2, IK4) by direct protein interaction; etoposide treatment decreases the KCTD5-Ikaros interaction, leading to accelerated Ikaros protein degradation in leukemic cells.","method":"Immunoprecipitation coupled with LC-MS/MS proteomics, co-immunoprecipitation, protein stability assays, siRNA knockdown","journal":"Biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — MS-identified interaction with co-IP validation and functional protein stability readout, single lab","pmids":["38424700"],"is_preprint":false},{"year":2025,"finding":"Conditional knockout of Kctd5 in striatal neurons causes a dystonic phenotype, coordination deficits, and augmented dopamine-evoked cAMP responses in striatal circuits; KCTD5 acts as a brake on Gβγ-mediated cAMP signaling, as rescue by a Gβγ-scavenging nanobody restores normal cAMP levels and pharmacological antagonism of the indirect striatal pathway partially rescues motor deficits.","method":"Conditional Kctd5 knockout mouse, 2-photon imaging of cAMP biosensor, Gβγ-scavenging nanobody rescue, pharmacological rescue, behavioral assays","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 2 — conditional KO with live imaging, mechanistic rescue with nanobody and pharmacology, multiple orthogonal approaches","pmids":["40233107"],"is_preprint":false},{"year":2025,"finding":"Homozygous Kctd5 knockout is embryonic lethal in mice; heterozygous Kctd5 knockout mice show abnormal lipid metabolism (elevated cholesterol and triglycerides), and transcriptome analysis implicates the PPAR signaling pathway and Apolipoprotein family gene expression as downstream effectors.","method":"CRISPR/Cas9 Kctd5 knockout mice, metabolic phenotyping, genome-wide gene expression analysis","journal":"The international journal of biochemistry & cell biology","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo KO with metabolic phenotype and transcriptomic pathway analysis, but pathway link is correlative","pmids":["40846050"],"is_preprint":false}],"current_model":"KCTD5 is a pentameric BTB-domain protein that functions as the substrate receptor of a CRL3KCTD5 E3 ubiquitin ligase complex: its BTB domain engages CUL3 while its C-terminal domain symmetrically binds five Gβγ subunits for ubiquitination via an ARIH1 E3-E3 superassembly, thereby limiting free Gβγ availability to dampen GPCR/cAMP signaling in neurons; it additionally ubiquitinates or modulates stability of other substrates (RhoGDI1, ΔNp63α, Ikaros) and regulates cell migration through Rac1 and Ca2+ signaling."},"narrative":{"teleology":[{"year":2008,"claim":"Establishing KCTD5 as a Cullin3 adaptor resolved its molecular identity: the BTB domain plus flanking residues bind CUL3, and KCTD5 oligomerizes and associates with ubiquitinated proteins, framing it as a substrate receptor for CRL3 complexes.","evidence":"Co-immunoprecipitation with N-terminal deletion mutagenesis and subcellular fractionation in cultured cells","pmids":["18573101"],"confidence":"High","gaps":["No physiological substrate was identified","Oligomeric stoichiometry was not determined","No in vivo functional consequence of CUL3 interaction was tested"]},{"year":2015,"claim":"Identification of MCM7, ZNF711, and FAM193B as KCTD5/CUL3-interacting proteins expanded the potential substrate repertoire but revealed an unexpected stabilization function for ZNF711, complicating a simple degradation model.","evidence":"Yeast two-hybrid and co-immunoprecipitation with protein stability assays in mammalian cells","pmids":["26188516"],"confidence":"Medium","gaps":["Stabilization mechanism is unexplained and not independently replicated","Whether these partners are bona fide ubiquitination substrates remains unresolved"]},{"year":2018,"claim":"Demonstrating that CUL3/KCTD5 monoubiquitinates ΔNp63α—impairing its DNA binding, transactivation, and pro-proliferative function—established the first substrate with a defined functional outcome and showed KCTD5 can modulate transcription factor activity without promoting degradation.","evidence":"Co-immunoprecipitation, in vivo ubiquitination assay, EMSA, reporter and proliferation assays","pmids":["29782646"],"confidence":"Medium","gaps":["Not independently replicated","In vivo relevance of ΔNp63α regulation by KCTD5 is untested","The ubiquitin chain type or modification site on ΔNp63α was not mapped"]},{"year":2020,"claim":"Identification of RhoGDI1 as a CUL3/KCTD5 degradation substrate, together with cell migration and Rac1/Ca²⁺ signaling phenotypes upon KCTD5 loss, connected the ligase to cytoskeletal regulation and focal adhesion dynamics.","evidence":"Co-IP and ubiquitination assays for RhoGDI1 degradation; CRISPR/shRNA knockdown with live-cell focal adhesion imaging, dominant-negative Rac1, Ca²⁺ imaging, and ionomycin rescue in B16-F10 cells","pmids":["32876072","33053687"],"confidence":"Medium","gaps":["Whether RhoGDI1 degradation directly causes the migration phenotype was not tested","Migration phenotype studied only in melanoma cells; generalizability unknown","Ubiquitination site(s) on RhoGDI1 not mapped"]},{"year":2023,"claim":"Cryo-EM resolution of the pentameric KCTD5–Gβγ architecture demonstrated that five C-terminal domains symmetrically capture five Gβγ copies for simultaneous CRL3-mediated ubiquitination, establishing Gβγ as a major physiological substrate and linking KCTD5 to GPCR/cAMP signal attenuation.","evidence":"Cryo-EM structure of KCTD5–Gβγ fusion complex; cAMP signaling assays","pmids":["37450587"],"confidence":"High","gaps":["Structure used a fusion construct; native complex architecture awaited confirmation","In vivo neuronal relevance was not yet shown"]},{"year":2023,"claim":"Discovery that KCTD5 forms hetero-oligomeric complexes with other KCTD family members (KCTD2, KCTD17) via distinct regions raised the possibility of combinatorial substrate recognition or regulation among KCTD paralogs.","evidence":"Co-immunoprecipitation, live-cell BRET, and domain-mapping luminescence assays","pmids":["37762619"],"confidence":"Medium","gaps":["Functional consequence of hetero-oligomerization is unknown","Stoichiometry of heteromeric assemblies not determined","Not independently confirmed"]},{"year":2024,"claim":"Structural and biochemical characterization of the full CRL3KCTD5–ARIH1 E3-E3 superassembly showed how >60° rotational dynamics between BTB/CUL3 and CTD/Gβγ moieties position ARIH1~ubiquitin for priming ubiquitination at Gβ Lys-23, providing the catalytic mechanism for substrate ubiquitylation.","evidence":"Cryo-EM of pentameric KCTD5/CUL3NTD/Gβ1γ2 complex; BRET interaction assays; in vitro ubiquitylation assays","pmids":["38625940"],"confidence":"High","gaps":["Whether ARIH1 involvement generalizes to other KCTD5 substrates (RhoGDI1, ΔNp63α) is unknown","Dynamics were inferred from conformational heterogeneity in cryo-EM; real-time kinetics not measured"]},{"year":2024,"claim":"Identification of Ikaros transcription factor isoforms as KCTD5-stabilized interactors—whose association is disrupted by etoposide—expanded KCTD5 function beyond ubiquitin-mediated degradation to include context-dependent protein stabilization in leukemic cells.","evidence":"IP-LC-MS/MS proteomics, co-immunoprecipitation, protein stability and siRNA knockdown assays in leukemic cells","pmids":["38424700"],"confidence":"Medium","gaps":["Mechanism of stabilization (e.g., whether CUL3 is involved) is unknown","Not independently replicated","In vivo relevance in leukemia untested"]},{"year":2025,"claim":"Conditional Kctd5 knockout in striatal neurons produced dystonia and augmented dopamine-evoked cAMP, rescued by a Gβγ-scavenging nanobody, providing the first in vivo proof that KCTD5 functions as a physiological brake on Gβγ/cAMP signaling in the basal ganglia.","evidence":"Conditional KO mouse, 2-photon cAMP biosensor imaging, Gβγ-scavenging nanobody and pharmacological rescue, behavioral assays","pmids":["40233107"],"confidence":"High","gaps":["Whether the dystonic phenotype reflects striatal-specific or broader CNS KCTD5 function is unclear","Contribution of non-Gβγ substrates to the neuronal phenotype was not dissected"]},{"year":2025,"claim":"Demonstrating that homozygous Kctd5 knockout is embryonic lethal and heterozygotes show dyslipidemia with elevated cholesterol/triglycerides revealed an essential developmental role and an unanticipated function in lipid homeostasis.","evidence":"CRISPR/Cas9 global Kctd5 KO mice, metabolic phenotyping, genome-wide expression analysis","pmids":["40846050"],"confidence":"Medium","gaps":["The lipid phenotype link to PPAR signaling is correlative; direct KCTD5 substrates in lipid metabolism are unidentified","Cause of embryonic lethality not determined","Whether the dyslipidemia is Gβγ-dependent or reflects a distinct substrate axis is unknown"]},{"year":null,"claim":"A major unresolved question is how KCTD5 selects among its diverse substrates (Gβγ, RhoGDI1, ΔNp63α, Ikaros) and determines whether a given interaction leads to degradative ubiquitination, non-degradative ubiquitination, or protein stabilization.","evidence":"","pmids":[],"confidence":"High","gaps":["No unified substrate-selection model exists","Role of KCTD hetero-oligomerization in substrate specificity is unexplored","Tissue-specific substrate hierarchy in vivo is undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,2,4,5]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,1,2]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,1,2,4,5]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,2,11]}],"complexes":["CRL3-KCTD5","CRL3-KCTD5-ARIH1"],"partners":["CUL3","GNB1","GNG2","ARIH1","ARHGDIA","KCTD2","KCTD17","IKZF1"],"other_free_text":[]},"mechanistic_narrative":"KCTD5 is a pentameric BTB-domain protein that serves as a substrate-specific adaptor for Cullin3-based E3 ubiquitin ligase complexes, with its best-characterized role being the ubiquitin-dependent degradation of free Gβγ subunits to restrain GPCR/cAMP signaling. Its C-terminal domain symmetrically engages five Gβγ copies while its BTB domain recruits CUL3, forming a CRL3–ARIH1 E3-E3 superassembly that positions ubiquitin transfer onto Gβ Lys-23; conditional Kctd5 knockout in striatal neurons causes augmented dopamine-evoked cAMP signaling and a dystonic motor phenotype rescued by a Gβγ-scavenging nanobody [PMID:37450587, PMID:38625940, PMID:40233107]. Beyond Gβγ, the CUL3/KCTD5 complex polyubiquitinates RhoGDI1 for degradation and monoubiquitinates ΔNp63α to impair its transcriptional activity, while KCTD5 also stabilizes Ikaros transcription factor isoforms through direct interaction, indicating substrate-dependent outcomes ranging from degradation to stabilization [PMID:32876072, PMID:29782646, PMID:38424700]. Homozygous Kctd5 knockout is embryonic lethal in mice, and heterozygous loss causes dyslipidemia with elevated cholesterol and triglycerides, implicating KCTD5 in lipid metabolic homeostasis [PMID:40846050]."},"prefetch_data":{"uniprot":{"accession":"Q9NXV2","full_name":"BTB/POZ domain-containing protein KCTD5","aliases":[],"length_aa":234,"mass_kda":26.1,"function":"Its interaction with CUL3 suggests that it may act as a substrate adapter in some E3 ligase complex (PubMed:18573101). Does not affect the function of Kv channel Kv2.1/KCNB1, Kv1.2/KCNA2, Kv4.2/KCND2 and Kv3.4/KCNC4 (PubMed:19361449)","subcellular_location":"Cytoplasm, cytosol; Cytoplasm; Nucleus","url":"https://www.uniprot.org/uniprotkb/Q9NXV2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KCTD5","classification":"Not Classified","n_dependent_lines":98,"n_total_lines":1208,"dependency_fraction":0.08112582781456953},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/KCTD5","total_profiled":1310},"omim":[{"mim_id":"611285","title":"POTASSIUM CHANNEL TETRAMERIZATION DOMAIN-CONTAINING PROTEIN 5; KCTD5","url":"https://www.omim.org/entry/611285"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/KCTD5"},"hgnc":{"alias_symbol":["FLJ20040"],"prev_symbol":[]},"alphafold":{"accession":"Q9NXV2","domains":[{"cath_id":"3.30.710.10","chopping":"46-150","consensus_level":"high","plddt":91.5983,"start":46,"end":150},{"cath_id":"3.30.70.2000","chopping":"153-191_198-212","consensus_level":"medium","plddt":86.9052,"start":153,"end":212}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NXV2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NXV2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NXV2-F1-predicted_aligned_error_v6.png","plddt_mean":77.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KCTD5","jax_strain_url":"https://www.jax.org/strain/search?query=KCTD5"},"sequence":{"accession":"Q9NXV2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NXV2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NXV2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NXV2"}},"corpus_meta":[{"pmid":"18573101","id":"PMC_18573101","title":"KCTD5, a putative substrate adaptor for cullin3 ubiquitin ligases.","date":"2008","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/18573101","citation_count":77,"is_preprint":false},{"pmid":"37450587","id":"PMC_37450587","title":"Structural basis for the ubiquitination of G protein βγ subunits by KCTD5/Cullin3 E3 ligase.","date":"2023","source":"Science advances","url":"https://pubmed.ncbi.nlm.nih.gov/37450587","citation_count":23,"is_preprint":false},{"pmid":"33053687","id":"PMC_33053687","title":"K+ Channel Tetramerization Domain 5 (KCTD5) Protein Regulates Cell Migration, Focal Adhesion Dynamics and Spreading through Modulation of Ca2+ Signaling and Rac1 Activity.","date":"2020","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/33053687","citation_count":14,"is_preprint":false},{"pmid":"26188516","id":"PMC_26188516","title":"Interactions of cullin3/KCTD5 complexes with both cytoplasmic and nuclear proteins: Evidence for a role in protein stabilization.","date":"2015","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/26188516","citation_count":13,"is_preprint":false},{"pmid":"29782646","id":"PMC_29782646","title":"Cullin3/KCTD5 induces monoubiquitination of ΔNp63α and impairs its activity.","date":"2018","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/29782646","citation_count":12,"is_preprint":false},{"pmid":"38625940","id":"PMC_38625940","title":"Structure and dynamics of a pentameric KCTD5/CUL3/Gβγ E3 ubiquitin ligase complex.","date":"2024","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/38625940","citation_count":11,"is_preprint":false},{"pmid":"37762619","id":"PMC_37762619","title":"KCTD5 Forms Hetero-Oligomeric Complexes with Various Members of the KCTD Protein Family.","date":"2023","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/37762619","citation_count":11,"is_preprint":false},{"pmid":"37149576","id":"PMC_37149576","title":"Identifies KCTD5 as a novel cancer biomarker associated with programmed cell death and chemotherapy drug sensitivity.","date":"2023","source":"BMC cancer","url":"https://pubmed.ncbi.nlm.nih.gov/37149576","citation_count":10,"is_preprint":false},{"pmid":"26336981","id":"PMC_26336981","title":"KCTD5 is endowed with large, functionally relevant, interdomain motions.","date":"2015","source":"Journal of biomolecular structure & dynamics","url":"https://pubmed.ncbi.nlm.nih.gov/26336981","citation_count":9,"is_preprint":false},{"pmid":"32876072","id":"PMC_32876072","title":"Cullin 3/KCTD5 Promotes the Ubiqutination of Rho Guanine Nucleotide Dissociation Inhibitor 1 and Regulates Its Stability.","date":"2020","source":"Journal of microbiology and biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/32876072","citation_count":8,"is_preprint":false},{"pmid":"29114497","id":"PMC_29114497","title":"KCTD5 and Ubiquitin Proteasome Signaling Are Required for Helicobacter pylori Adherence.","date":"2017","source":"Frontiers in cellular and infection microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/29114497","citation_count":7,"is_preprint":false},{"pmid":"39027992","id":"PMC_39027992","title":"CD8+ T cell‑related KCTD5 contributes to malignant progression and unfavorable clinical outcome of patients with triple‑negative breast cancer.","date":"2024","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/39027992","citation_count":2,"is_preprint":false},{"pmid":"40233107","id":"PMC_40233107","title":"The G protein modifier KCTD5 tunes the decoding of neuromodulatory signals necessary for motor function in striatal neurons.","date":"2025","source":"PLoS biology","url":"https://pubmed.ncbi.nlm.nih.gov/40233107","citation_count":2,"is_preprint":false},{"pmid":"40846050","id":"PMC_40846050","title":"Heterozygous Kctd5 knockout mice exhibit abnormal lipid metabolism.","date":"2025","source":"The international journal of biochemistry & cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/40846050","citation_count":0,"is_preprint":false},{"pmid":"38424700","id":"PMC_38424700","title":"KCTD5 regulates Ikaros degradation induced by chemotherapeutic drug etoposide in hematological cells.","date":"2024","source":"Biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/38424700","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8433,"output_tokens":3173,"usd":0.036447},"stage2":{"model":"claude-opus-4-6","input_tokens":6644,"output_tokens":3146,"usd":0.167805},"total_usd":0.204252,"stage1_batch_id":"msgbatch_01Mgbec4vM6c9vXht7JVJzss","stage2_batch_id":"msgbatch_01JkuuH5RB2BdJNsgnhjbC6s","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2008,\n      \"finding\": \"KCTD5 interacts specifically with Cullin3 via its BTB domain plus additional N-terminal residues, forms oligomers through its BTB domain, and binds ubiquitinated proteins, establishing it as a putative substrate-specific adaptor for Cullin3-based E3 ubiquitin ligases. KCTD5 localizes to the cytosol of cultured cell lines.\",\n      \"method\": \"Co-immunoprecipitation, protein binding assays, N-terminal deletion mutagenesis, subcellular fractionation\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal interactions demonstrated with mutagenesis, replicated by multiple subsequent studies\",\n      \"pmids\": [\"18573101\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"KCTD5 in pentameric form engages symmetrically with five copies of Gβγ through its C-terminal domain; the pentameric KCTD5/Cul3 E3 ligase complex simultaneously ubiquitinates five Gβγ subunits, and this ubiquitination triggers degradation of free Gβγ to negatively regulate GPCR/cAMP signaling.\",\n      \"method\": \"Cryo-electron microscopy structure determination of KCTD5-Gβγ fusion complex and KCTD7-Cul3 complex; functional cAMP signaling assays\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structure with functional validation of ubiquitination and cAMP signaling\",\n      \"pmids\": [\"37450587\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CRL3KCTD5 engages the E3 ligase ARIH1 in an E3-E3 superassembly to ubiquitylate Gβγ; the cryo-EM structure of the 5:5:5 KCTD5/CUL3NTD/Gβ1γ2 assembly reveals >60° rotational dynamics between BTB/CUL3 and CTD/Gβγ moieties, with ARIH1~ubiquitin positioned within 10 Å of Lys-23 of Gβ in priming conformations.\",\n      \"method\": \"Cryo-EM structure of pentameric complex; BRET-based interaction assays; in vitro ubiquitylation assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution cryo-EM with multiple orthogonal functional assays\",\n      \"pmids\": [\"38625940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"KCTD5 interacts with MCM7, ZNF711, and FAM193B, forming trimeric complexes with Cullin3; however, KCTD5/Cullin3 did not induce degradation of these partners—overexpression of KCTD5 or Cullin3 instead increased ZNF711 protein stability, suggesting a role in protein stabilization rather than degradation for some substrates.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation in mammalian cells, protein stability assays\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — two orthogonal interaction methods but single lab and unexpected result not yet replicated\",\n      \"pmids\": [\"26188516\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"KCTD5 physically interacts with ΔNp63α and, together with Cullin3, induces monoubiquitination of ΔNp63α, impairing its DNA-binding affinity and both its transactivation and transinhibitory activities, and reducing its pro-proliferative function.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assay, DNA-binding (EMSA), reporter assays, proliferation assays\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods in single lab study\",\n      \"pmids\": [\"29782646\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"KCTD5 binds to RhoGDI1 and increases its interaction with Cullin3; ectopic KCTD5 expression increases polyubiquitination of RhoGDI1 while KCTD5 knockdown stabilizes RhoGDI1, establishing CUL3/KCTD5 as a ubiquitin ligase complex that promotes RhoGDI1 degradation.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assay, RNA interference knockdown, protein stability assays\",\n      \"journal\": \"Journal of microbiology and biotechnology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal gain/loss-of-function with ubiquitination assay, single lab\",\n      \"pmids\": [\"32876072\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"KCTD5 depletion (CRISPR/Cas9 and shRNA) in B16-F10 cells increases cell migration and spreading and decreases focal adhesion area via increased focal adhesion disassembly; these effects are mediated through Rac1 activity (blocked by dominant-negative Rac1) and Ca2+ signaling (KCTD5 silencing decreases serum-induced Ca2+ response, and ionomycin rescue abolishes the focal adhesion phenotype).\",\n      \"method\": \"CRISPR/Cas9 and shRNA knockdown, live-cell imaging of focal adhesion dynamics, dominant-negative Rac1 expression, Ca2+ imaging, ionomycin rescue\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods with specific pathway rescue, single lab\",\n      \"pmids\": [\"33053687\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Molecular dynamics simulations of full-length KCTD5 reveal large interdomain twisting motions pivoted by Ser150 in the hinge region between the BTB and C-terminal domains; these motions are proposed to position substrates for ubiquitination relative to the E2/E3 machinery.\",\n      \"method\": \"Molecular dynamics simulation (120 ns) of pentameric KCTD5\",\n      \"journal\": \"Journal of biomolecular structure & dynamics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 — computational prediction only, no experimental validation of functional role of Ser150\",\n      \"pmids\": [\"26336981\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"KCTD5 is itself ubiquitinated and degraded by the proteasome; H. pylori infection impairs KCTD5 ubiquitination, and reduced KCTD5 levels increase bacterial adherence, indicating that KCTD5 ubiquitin ligase activity limits H. pylori adherence to gastric epithelial cells.\",\n      \"method\": \"shRNA knockdown, proteasome inhibitor treatment, infection adherence assays, ubiquitination assays in AGS cells\",\n      \"journal\": \"Frontiers in cellular and infection microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic knockdown with specific bacterial adherence phenotype and ubiquitination assays, single lab\",\n      \"pmids\": [\"29114497\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"KCTD5 forms hetero-oligomeric complexes with multiple KCTD family members (including KCTD2 and KCTD17) through distinct regions of KCTD5; different regions of KCTD5 are responsible for interactions with different KCTD partners.\",\n      \"method\": \"Co-immunoprecipitation, live-cell BRET, IP-luminescence domain mapping\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — two orthogonal interaction methods with domain mapping, single lab\",\n      \"pmids\": [\"37762619\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"KCTD5 stabilizes Ikaros transcription factor isoforms (IK1, IK2, IK4) by direct protein interaction; etoposide treatment decreases the KCTD5-Ikaros interaction, leading to accelerated Ikaros protein degradation in leukemic cells.\",\n      \"method\": \"Immunoprecipitation coupled with LC-MS/MS proteomics, co-immunoprecipitation, protein stability assays, siRNA knockdown\",\n      \"journal\": \"Biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — MS-identified interaction with co-IP validation and functional protein stability readout, single lab\",\n      \"pmids\": [\"38424700\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Conditional knockout of Kctd5 in striatal neurons causes a dystonic phenotype, coordination deficits, and augmented dopamine-evoked cAMP responses in striatal circuits; KCTD5 acts as a brake on Gβγ-mediated cAMP signaling, as rescue by a Gβγ-scavenging nanobody restores normal cAMP levels and pharmacological antagonism of the indirect striatal pathway partially rescues motor deficits.\",\n      \"method\": \"Conditional Kctd5 knockout mouse, 2-photon imaging of cAMP biosensor, Gβγ-scavenging nanobody rescue, pharmacological rescue, behavioral assays\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — conditional KO with live imaging, mechanistic rescue with nanobody and pharmacology, multiple orthogonal approaches\",\n      \"pmids\": [\"40233107\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Homozygous Kctd5 knockout is embryonic lethal in mice; heterozygous Kctd5 knockout mice show abnormal lipid metabolism (elevated cholesterol and triglycerides), and transcriptome analysis implicates the PPAR signaling pathway and Apolipoprotein family gene expression as downstream effectors.\",\n      \"method\": \"CRISPR/Cas9 Kctd5 knockout mice, metabolic phenotyping, genome-wide gene expression analysis\",\n      \"journal\": \"The international journal of biochemistry & cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo KO with metabolic phenotype and transcriptomic pathway analysis, but pathway link is correlative\",\n      \"pmids\": [\"40846050\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KCTD5 is a pentameric BTB-domain protein that functions as the substrate receptor of a CRL3KCTD5 E3 ubiquitin ligase complex: its BTB domain engages CUL3 while its C-terminal domain symmetrically binds five Gβγ subunits for ubiquitination via an ARIH1 E3-E3 superassembly, thereby limiting free Gβγ availability to dampen GPCR/cAMP signaling in neurons; it additionally ubiquitinates or modulates stability of other substrates (RhoGDI1, ΔNp63α, Ikaros) and regulates cell migration through Rac1 and Ca2+ signaling.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"KCTD5 is a pentameric BTB-domain protein that serves as a substrate-specific adaptor for Cullin3-based E3 ubiquitin ligase complexes, with its best-characterized role being the ubiquitin-dependent degradation of free Gβγ subunits to restrain GPCR/cAMP signaling. Its C-terminal domain symmetrically engages five Gβγ copies while its BTB domain recruits CUL3, forming a CRL3–ARIH1 E3-E3 superassembly that positions ubiquitin transfer onto Gβ Lys-23; conditional Kctd5 knockout in striatal neurons causes augmented dopamine-evoked cAMP signaling and a dystonic motor phenotype rescued by a Gβγ-scavenging nanobody [PMID:37450587, PMID:38625940, PMID:40233107]. Beyond Gβγ, the CUL3/KCTD5 complex polyubiquitinates RhoGDI1 for degradation and monoubiquitinates ΔNp63α to impair its transcriptional activity, while KCTD5 also stabilizes Ikaros transcription factor isoforms through direct interaction, indicating substrate-dependent outcomes ranging from degradation to stabilization [PMID:32876072, PMID:29782646, PMID:38424700]. Homozygous Kctd5 knockout is embryonic lethal in mice, and heterozygous loss causes dyslipidemia with elevated cholesterol and triglycerides, implicating KCTD5 in lipid metabolic homeostasis [PMID:40846050].\",\n  \"teleology\": [\n    {\n      \"year\": 2008,\n      \"claim\": \"Establishing KCTD5 as a Cullin3 adaptor resolved its molecular identity: the BTB domain plus flanking residues bind CUL3, and KCTD5 oligomerizes and associates with ubiquitinated proteins, framing it as a substrate receptor for CRL3 complexes.\",\n      \"evidence\": \"Co-immunoprecipitation with N-terminal deletion mutagenesis and subcellular fractionation in cultured cells\",\n      \"pmids\": [\"18573101\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No physiological substrate was identified\",\n        \"Oligomeric stoichiometry was not determined\",\n        \"No in vivo functional consequence of CUL3 interaction was tested\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identification of MCM7, ZNF711, and FAM193B as KCTD5/CUL3-interacting proteins expanded the potential substrate repertoire but revealed an unexpected stabilization function for ZNF711, complicating a simple degradation model.\",\n      \"evidence\": \"Yeast two-hybrid and co-immunoprecipitation with protein stability assays in mammalian cells\",\n      \"pmids\": [\"26188516\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Stabilization mechanism is unexplained and not independently replicated\",\n        \"Whether these partners are bona fide ubiquitination substrates remains unresolved\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrating that CUL3/KCTD5 monoubiquitinates ΔNp63α—impairing its DNA binding, transactivation, and pro-proliferative function—established the first substrate with a defined functional outcome and showed KCTD5 can modulate transcription factor activity without promoting degradation.\",\n      \"evidence\": \"Co-immunoprecipitation, in vivo ubiquitination assay, EMSA, reporter and proliferation assays\",\n      \"pmids\": [\"29782646\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Not independently replicated\",\n        \"In vivo relevance of ΔNp63α regulation by KCTD5 is untested\",\n        \"The ubiquitin chain type or modification site on ΔNp63α was not mapped\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identification of RhoGDI1 as a CUL3/KCTD5 degradation substrate, together with cell migration and Rac1/Ca²⁺ signaling phenotypes upon KCTD5 loss, connected the ligase to cytoskeletal regulation and focal adhesion dynamics.\",\n      \"evidence\": \"Co-IP and ubiquitination assays for RhoGDI1 degradation; CRISPR/shRNA knockdown with live-cell focal adhesion imaging, dominant-negative Rac1, Ca²⁺ imaging, and ionomycin rescue in B16-F10 cells\",\n      \"pmids\": [\"32876072\", \"33053687\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether RhoGDI1 degradation directly causes the migration phenotype was not tested\",\n        \"Migration phenotype studied only in melanoma cells; generalizability unknown\",\n        \"Ubiquitination site(s) on RhoGDI1 not mapped\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Cryo-EM resolution of the pentameric KCTD5–Gβγ architecture demonstrated that five C-terminal domains symmetrically capture five Gβγ copies for simultaneous CRL3-mediated ubiquitination, establishing Gβγ as a major physiological substrate and linking KCTD5 to GPCR/cAMP signal attenuation.\",\n      \"evidence\": \"Cryo-EM structure of KCTD5–Gβγ fusion complex; cAMP signaling assays\",\n      \"pmids\": [\"37450587\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structure used a fusion construct; native complex architecture awaited confirmation\",\n        \"In vivo neuronal relevance was not yet shown\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Discovery that KCTD5 forms hetero-oligomeric complexes with other KCTD family members (KCTD2, KCTD17) via distinct regions raised the possibility of combinatorial substrate recognition or regulation among KCTD paralogs.\",\n      \"evidence\": \"Co-immunoprecipitation, live-cell BRET, and domain-mapping luminescence assays\",\n      \"pmids\": [\"37762619\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Functional consequence of hetero-oligomerization is unknown\",\n        \"Stoichiometry of heteromeric assemblies not determined\",\n        \"Not independently confirmed\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Structural and biochemical characterization of the full CRL3KCTD5–ARIH1 E3-E3 superassembly showed how >60° rotational dynamics between BTB/CUL3 and CTD/Gβγ moieties position ARIH1~ubiquitin for priming ubiquitination at Gβ Lys-23, providing the catalytic mechanism for substrate ubiquitylation.\",\n      \"evidence\": \"Cryo-EM of pentameric KCTD5/CUL3NTD/Gβ1γ2 complex; BRET interaction assays; in vitro ubiquitylation assays\",\n      \"pmids\": [\"38625940\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether ARIH1 involvement generalizes to other KCTD5 substrates (RhoGDI1, ΔNp63α) is unknown\",\n        \"Dynamics were inferred from conformational heterogeneity in cryo-EM; real-time kinetics not measured\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identification of Ikaros transcription factor isoforms as KCTD5-stabilized interactors—whose association is disrupted by etoposide—expanded KCTD5 function beyond ubiquitin-mediated degradation to include context-dependent protein stabilization in leukemic cells.\",\n      \"evidence\": \"IP-LC-MS/MS proteomics, co-immunoprecipitation, protein stability and siRNA knockdown assays in leukemic cells\",\n      \"pmids\": [\"38424700\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism of stabilization (e.g., whether CUL3 is involved) is unknown\",\n        \"Not independently replicated\",\n        \"In vivo relevance in leukemia untested\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Conditional Kctd5 knockout in striatal neurons produced dystonia and augmented dopamine-evoked cAMP, rescued by a Gβγ-scavenging nanobody, providing the first in vivo proof that KCTD5 functions as a physiological brake on Gβγ/cAMP signaling in the basal ganglia.\",\n      \"evidence\": \"Conditional KO mouse, 2-photon cAMP biosensor imaging, Gβγ-scavenging nanobody and pharmacological rescue, behavioral assays\",\n      \"pmids\": [\"40233107\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether the dystonic phenotype reflects striatal-specific or broader CNS KCTD5 function is unclear\",\n        \"Contribution of non-Gβγ substrates to the neuronal phenotype was not dissected\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Demonstrating that homozygous Kctd5 knockout is embryonic lethal and heterozygotes show dyslipidemia with elevated cholesterol/triglycerides revealed an essential developmental role and an unanticipated function in lipid homeostasis.\",\n      \"evidence\": \"CRISPR/Cas9 global Kctd5 KO mice, metabolic phenotyping, genome-wide expression analysis\",\n      \"pmids\": [\"40846050\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"The lipid phenotype link to PPAR signaling is correlative; direct KCTD5 substrates in lipid metabolism are unidentified\",\n        \"Cause of embryonic lethality not determined\",\n        \"Whether the dyslipidemia is Gβγ-dependent or reflects a distinct substrate axis is unknown\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A major unresolved question is how KCTD5 selects among its diverse substrates (Gβγ, RhoGDI1, ΔNp63α, Ikaros) and determines whether a given interaction leads to degradative ubiquitination, non-degradative ubiquitination, or protein stabilization.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No unified substrate-selection model exists\",\n        \"Role of KCTD hetero-oligomerization in substrate specificity is unexplored\",\n        \"Tissue-specific substrate hierarchy in vivo is undefined\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 2, 4, 5]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 1, 2, 4, 5]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 2, 11]}\n    ],\n    \"complexes\": [\n      \"CRL3-KCTD5\",\n      \"CRL3-KCTD5-ARIH1\"\n    ],\n    \"partners\": [\n      \"CUL3\",\n      \"GNB1\",\n      \"GNG2\",\n      \"ARIH1\",\n      \"ARHGDIA\",\n      \"KCTD2\",\n      \"KCTD17\",\n      \"IKZF1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}