Affinage

KCTD5

BTB/POZ domain-containing protein KCTD5 · UniProt Q9NXV2

Length
234 aa
Mass
26.1 kDa
Annotated
2026-06-10
16 papers in source corpus 14 papers cited in narrative 14 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 7/7 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

KCTD5 is a pentameric BTB-domain protein that serves as a substrate-specific adaptor for Cullin3-RING E3 ubiquitin ligase complexes, coupling substrate recognition to ubiquitin transfer (PMID:18573101, PMID:37450587). It oligomerizes through its BTB domain and engages Cullin3 via the BTB plus additional N-terminal residues, while its C-terminal domain captures substrate (PMID:18573101, PMID:37450587). Its best-characterized substrate is the heterotrimeric G protein Gβγ dimer: cryo-EM of the symmetric 5:5:5 KCTD5/CUL3/Gβγ assembly shows five Gβγ engaged simultaneously, and CRL3KCTD5 recruits the RING-between-RING ligase ARIH1 in an E3-E3 superassembly that primes ubiquitin transfer onto Gβ, thereby negatively regulating cAMP signaling downstream of GPCRs (PMID:37450587, PMID:38625940). In vivo, conditional deletion of Kctd5 in striatal neurons produces a dystonic, motor-incoordinate phenotype with augmented dopaminergic cAMP responses that is rescued by a Gβγ-scavenging nanobody, establishing KCTD5 as a physiological brake on Gβγ-mediated cAMP signaling in striatal circuits (PMID:40233107). Beyond Gβγ, KCTD5/CUL3 acts on additional substrates with distinct outcomes: degradative ubiquitination of RhoGDI1 (PMID:32876072), monoubiquitination of ΔNp63α that reduces its DNA binding and proliferative activity (PMID:29782646), and stabilization rather than degradation of partners including ZNF711 and the Ikaros transcription factor (PMID:26188516, PMID:38424700). KCTD5 also regulates the actin cytoskeleton and cell migration through Rac1 activity, focal adhesion dynamics, and Ca2+ signaling (PMID:33053687), and positively regulates TRPM4 channel Ca2+ sensitivity through a defined protein-protein interface that promotes cell invasion (PMID:42214084). It forms hetero-oligomers with other KCTD family members, and its own levels are controlled by proteasomal turnover (PMID:29114497, PMID:37762619).

Mechanistic history

Synthesis pass · year-by-year structured walk · 13 steps
  1. 2008 Medium

    Established the founding hypothesis that KCTD5 is a Cullin3 substrate adaptor rather than a passive BTB protein, defining the structural determinants of the interaction.

    Evidence Co-IP, binding assays, and BTB/N-terminal mutagenesis in cultured cells

    PMID:18573101

    Open questions at the time
    • No substrate identified at this stage
    • Ubiquitination activity not directly demonstrated
    • Single-lab reciprocal Co-IP
  2. 2015 Medium

    Showed that not all KCTD5/Cullin3 partners are degraded, revealing a non-degradative, stabilizing mode of action for some substrates.

    Evidence Yeast two-hybrid, Co-IP, and proteasome inhibitor/overexpression assays identifying MCM7, ZNF711, FAM193B

    PMID:26188516

    Open questions at the time
    • Mechanism of stabilization not defined
    • Physiological relevance of these partners unclear
    • No ubiquitination observed despite complex formation
  3. 2015 Low

    Proposed how the pentameric assembly could position substrates by modeling interdomain motion, framing a structural basis for catalysis.

    Evidence 120 ns molecular dynamics simulation of full-length KCTD5 pentamer identifying Ser150 hinge

    PMID:26336981

    Open questions at the time
    • Computational only; Ser150 role not experimentally validated
    • No substrate present in simulation
  4. 2017 Medium

    Demonstrated that KCTD5 levels are themselves regulated by ubiquitin-proteasome turnover and that a pathogen exploits this to aid colonization.

    Evidence Ubiquitination/proteasome inhibitor assays, knockdown, and H. pylori adherence assays in gastric epithelial cells

    PMID:29114497

    Open questions at the time
    • E3 ligase responsible for KCTD5 turnover not identified
    • Mechanism linking KCTD5 loss to adherence not resolved
  5. 2018 Medium

    Identified ΔNp63α as a substrate and showed KCTD5 imposes a regulatory monoubiquitination that tunes transcription factor activity rather than destroying it.

    Evidence Co-IP, ubiquitination, DNA-binding, transactivation reporter, and proliferation assays

    PMID:29782646

    Open questions at the time
    • Monoubiquitination site not mapped
    • Single-lab functional readouts
  6. 2020 Medium

    Expanded the degradative substrate set to RhoGDI1 and connected KCTD5 to cytoskeletal regulation via Rac1 and Ca2+ signaling in migration.

    Evidence Co-IP, ubiquitination, KD/dominant-negative rescue, and CRISPR KO with live-cell imaging and Ca2+ imaging

    PMID:32876072 PMID:33053687

    Open questions at the time
    • Direct link between RhoGDI1 degradation and the migration phenotype not fully established
    • Mechanism of KCTD5 effect on Ca2+ entry undefined
  7. 2023 High

    Resolved the central mechanistic question of how KCTD5 acts catalytically, showing a pentameric CRL3KCTD5 engages five Gβγ symmetrically to ubiquitinate them and suppress cAMP signaling.

    Evidence Cryo-EM structure with ubiquitination and cAMP signaling assays

    PMID:37450587

    Open questions at the time
    • In vivo physiological role not yet tested at this stage
    • How E2 delivery is coordinated across five sites not detailed
  8. 2023 Medium

    Demonstrated KCTD5 forms hetero-oligomers with other KCTD family members, implying combinatorial adaptor assemblies.

    Evidence Co-IP, live-cell BRET, and IP-luminescence domain mapping

    PMID:37762619

    Open questions at the time
    • Functional consequence of heteromerization for substrate selection unknown
    • Stoichiometry of mixed oligomers not defined
  9. 2024 High

    Defined the catalytic geometry by showing CRL3KCTD5 recruits ARIH1 in an E3-E3 superassembly that positions the ubiquitin thioester near Gβ Lys-23, explaining priming of transfer.

    Evidence Cryo-EM of the dynamic 5:5:5 assembly with ubiquitylation assays and modeling of CUL3/RBX1/ARIH1~ubiquitin

    PMID:38625940

    Open questions at the time
    • Processivity and chain-type specificity not fully resolved
    • Role of >60° interdomain dynamics in turnover not directly tested
  10. 2024 Medium

    Established a stabilizing role in leukemic cells by identifying KCTD5 as a factor that protects Ikaros isoforms from degradation under genotoxic stress.

    Evidence IP-LC-MS/MS, Co-IP, and protein stability assays with etoposide treatment

    PMID:38424700

    Open questions at the time
    • Molecular basis of stabilization versus degradation choice unresolved
    • Isoform selectivity mechanism unknown
  11. 2025 High

    Provided in vivo validation that KCTD5 is a physiological brake on Gβγ-mediated cAMP signaling required for motor coordination.

    Evidence Striatal conditional KO mice with 2-photon cAMP imaging, Gβγ-scavenging nanobody rescue, pharmacological rescue, and behavior

    PMID:40233107

    Open questions at the time
    • Cell-type-specific substrate scope in vivo beyond Gβγ untested
    • Link to dystonia mechanism only partially defined
  12. 2025 Low

    Indicated a developmental and metabolic role, with embryonic lethality of full knockout and lipid-metabolism abnormalities in heterozygotes.

    Evidence CRISPR heterozygous KO mice, metabolic profiling, genome-wide expression analysis

    PMID:40846050

    Open questions at the time
    • PPAR/Apolipoprotein pathway link is transcriptomic inference without mechanistic validation
    • Direct substrate driving the lipid phenotype not identified
  13. 2026 Medium

    Showed KCTD5 acts as a positive regulator of an ion channel, increasing TRPM4 Ca2+ sensitivity through a definable interface that promotes invasion.

    Evidence BiFC, patch clamp, intracellular Na+ recordings, CRISPR KO cells, interface-disrupting peptides, and invasion assays

    PMID:42214084

    Open questions at the time
    • Whether regulation is ubiquitination-dependent unclear
    • Structural basis of the TRPM4-KCTD5 interface not solved

Open questions

Synthesis pass · forward-looking unresolved questions
  • How KCTD5 chooses between degradative polyubiquitination, regulatory monoubiquitination, substrate stabilization, and ubiquitination-independent channel modulation across its diverse partners remains unresolved.
  • No unifying rule distinguishes degraded versus stabilized substrates
  • Contribution of KCTD heteromerization to substrate choice unknown
  • Tissue-specific substrate repertoire largely uncharacterized

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140096 catalytic activity, acting on a protein 4 GO:0016874 ligase activity 3 GO:0060090 molecular adaptor activity 2 GO:0098772 molecular function regulator activity 2
Localization
GO:0005829 cytosol 1
Pathway
R-HSA-392499 Metabolism of proteins 3 R-HSA-162582 Signal Transduction 2
Complex memberships
CRL3KCTD5 (Cullin3-RING E3 ligase)CRL3KCTD5-ARIH1 E3-E3 superassembly

Evidence

Reading pass · 14 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2008 KCTD5 interacts specifically with Cullin3 via its BTB domain plus additional N-terminal residues, binds ubiquitinated proteins, and forms oligomers through its BTB domain, establishing it as a putative substrate-specific adaptor for Cullin3-based E3 ligases. KCTD5 was found in the cytosol of cultured cell lines. Co-immunoprecipitation, binding assays, mutagenesis of BTB/N-terminal residues, subcellular fractionation The FEBS journal Medium 18573101
2023 KCTD5 assembles as a pentamer and, in complex with Cullin3, ubiquitinates Gβγ subunits; cryo-EM structure shows five copies of Gβγ engaged symmetrically through KCTD5's C-terminal domain, enabling simultaneous ubiquitin transfer from the E2 enzyme to five Gβγ subunits. KCTD5-mediated Gβγ ubiquitination negatively regulates cAMP signaling downstream of GPCRs. Cryo-electron microscopy structure determination, ubiquitination assays, cAMP signaling assays Science advances High 37450587
2024 Cryo-EM structure of the 5:5:5 KCTD5/CUL3NTD/Gβ1γ2 assembly reveals a highly dynamic complex with >60° rotational freedom between BTB and CTD moieties; CRL3KCTD5 engages the E3 ligase ARIH1 in an E3-E3 superassembly to ubiquitylate Gβγ, with conformational states positioning the ARIH1~ubiquitin thioester bond within ~10 Å of Lys-23 of Gβ as likely priming complexes. Cryo-EM structure determination, ubiquitylation assays, structural modeling of full-length CUL3/RBX1/ARIH1~ubiquitin conjugate Proceedings of the National Academy of Sciences of the United States of America High 38625940
2015 KCTD5 interacts with MCM7, ZNF711, and FAM193B, forming trimeric complexes with Cullin3; however, KCTD5/Cullin3 did not induce polyubiquitylation or proteasome-dependent degradation of these partners. Instead, KCTD5 or Cullin3 overexpression increased ZNF711 protein stability, suggesting a role in protein stabilization rather than degradation for some substrates. Yeast two-hybrid, co-immunoprecipitation in mammalian cells, proteasome inhibitor assays, overexpression experiments Biochemical and biophysical research communications Medium 26188516
2015 Molecular dynamics simulations of KCTD5 reveal that the pentameric CTD assembly is intrinsically stable, and that large interdomain twisting motions between the BTB and CTD domains are pivoted by a single hinge residue (Ser150), potentially positioning substrates for ubiquitination. Molecular dynamics simulations (120 ns) of full-length KCTD5 pentamer Journal of biomolecular structure & dynamics Low 26336981
2018 KCTD5 physically interacts with ΔNp63α, and the Cullin3/KCTD5 complex induces monoubiquitination (not polyubiquitination) of ΔNp63α, reducing its DNA-binding affinity and impairing both its transactivation and transinhibitory activities, thereby attenuating ΔNp63α-driven cell proliferation. Co-immunoprecipitation, ubiquitination assays, DNA-binding assays, reporter/transactivation assays, cell proliferation assays FEBS letters Medium 29782646
2020 KCTD5 binds RhoGDI1 and increases its interaction with CUL3; ectopic KCTD5 expression increases RhoGDI1 ubiquitination, whereas KCTD5 knockdown stabilizes RhoGDI1 and reduces its ubiquitination, establishing CUL3/KCTD5 as an E3 ligase complex that targets RhoGDI1 for degradation. Co-immunoprecipitation, ubiquitination assays, RNA interference knockdown, dominant-negative CUL3 expression, stability assays Journal of microbiology and biotechnology Medium 32876072
2020 CRISPR/Cas9 and shRNA depletion of KCTD5 in B16-F10 cells increases cell migration, cell spreading, and focal adhesion disassembly rate. These effects are mediated through Rac1 GTPase activity (dominant-negative Rac1 rescues spreading) and Ca2+ signaling (KCTD5 loss decreases serum-induced Ca2+ response; ionomycin reversal restores focal adhesion size). CRISPR/Cas9 knockout, shRNA knockdown, live-cell imaging, dominant-negative Rac1 expression, Ca2+ imaging, focal adhesion dynamics assays Cells Medium 33053687
2017 KCTD5 itself is ubiquitinated and degraded by the proteasome in AGS gastric epithelial cells; H. pylori infection impairs KCTD5 ubiquitination, reducing KCTD5 levels. Decreased KCTD5 (an adaptor of Cullin-3) increases H. pylori adherence, indicating KCTD5 proteasomal turnover is exploited by the pathogen to facilitate colonization. Ubiquitination assays, proteasome inhibitor experiments, H. pylori infection assays, RNA interference knockdown, adherence assays Frontiers in cellular and infection microbiology Medium 29114497
2023 KCTD5 forms hetero-oligomeric complexes with numerous other KCTD family members (including KCTD2, KCTD17, and others); different regions of KCTD5 contribute distinctly to interactions with different KCTD partners. Co-immunoprecipitation, BRET (bioluminescence resonance energy transfer) in live cells, IP-luminescence domain-mapping assays International journal of molecular sciences Medium 37762619
2024 KCTD5 is identified as a key stabilizing factor for Ikaros transcription factor; etoposide treatment decreases the KCTD5-Ikaros interaction, leading to accelerated Ikaros protein degradation (affecting IK1, IK2, IK4 isoforms but not IK6/IK7) in leukemic cells. Immunoprecipitation coupled with LC-MS/MS, co-immunoprecipitation, protein stability/degradation assays, etoposide treatment experiments Biological chemistry Medium 38424700
2025 Conditional knockout of Kctd5 in striatal neurons in mice leads to dystonic phenotype, coordination deficits, and augmented electrically evoked cAMP responses to dopaminergic stimulation. Rescue by a Gβγ-scavenging nanobody confirms KCTD5 acts as a brake on Gβγ-mediated cAMP signaling in striatal circuits, and motor deficits are partially rescued by pharmacological antagonism of the indirect striatal cAMP pathway. Conditional knockout mouse (Cre-lox), 2-photon cAMP biosensor imaging, Gβγ-scavenging nanobody rescue, pharmacological rescue, behavioral assays PLoS biology High 40233107
2025 Heterozygous Kctd5 knockout mice (Kctd5-/- embryos are lethal in early embryonic development) exhibit abnormal lipid metabolism including elevated cholesterol and triglycerides; genome-wide expression analysis suggests KCTD5 affects the PPAR signaling pathway and expression of Apolipoprotein family genes to regulate lipid metabolism. CRISPR/Cas9 heterozygous knockout mice, metabolic profiling, genome-wide gene expression analysis The international journal of biochemistry & cell biology Low 40846050
2026 KCTD5 acts as a positive regulator of TRPM4 channel activity, increasing Ca2+ sensitivity; peptides designed to disrupt the TRPM4-KCTD5 protein-protein interface reduce TRPM4-dependent Na+ influx and currents and decrease cell invasion in MDA-MB-231 cells, confirming the functional importance of this interaction. BiFC (bimolecular fluorescent complementation), patch clamp electrophysiology, intracellular Na+ recordings, CRISPR KCTD5 knockout cells (HEK293KCTD5-/-), cell invasion assays Journal of chemical information and modeling Medium 42214084

Source papers

Stage 0 corpus · 16 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2008 KCTD5, a putative substrate adaptor for cullin3 ubiquitin ligases. The FEBS journal 77 18573101
2023 Structural basis for the ubiquitination of G protein βγ subunits by KCTD5/Cullin3 E3 ligase. Science advances 24 37450587
2020 K+ Channel Tetramerization Domain 5 (KCTD5) Protein Regulates Cell Migration, Focal Adhesion Dynamics and Spreading through Modulation of Ca2+ Signaling and Rac1 Activity. Cells 14 33053687
2024 Structure and dynamics of a pentameric KCTD5/CUL3/Gβγ E3 ubiquitin ligase complex. Proceedings of the National Academy of Sciences of the United States of America 13 38625940
2015 Interactions of cullin3/KCTD5 complexes with both cytoplasmic and nuclear proteins: Evidence for a role in protein stabilization. Biochemical and biophysical research communications 13 26188516
2018 Cullin3/KCTD5 induces monoubiquitination of ΔNp63α and impairs its activity. FEBS letters 12 29782646
2023 Identifies KCTD5 as a novel cancer biomarker associated with programmed cell death and chemotherapy drug sensitivity. BMC cancer 11 37149576
2023 KCTD5 Forms Hetero-Oligomeric Complexes with Various Members of the KCTD Protein Family. International journal of molecular sciences 11 37762619
2015 KCTD5 is endowed with large, functionally relevant, interdomain motions. Journal of biomolecular structure & dynamics 9 26336981
2020 Cullin 3/KCTD5 Promotes the Ubiqutination of Rho Guanine Nucleotide Dissociation Inhibitor 1 and Regulates Its Stability. Journal of microbiology and biotechnology 8 32876072
2017 KCTD5 and Ubiquitin Proteasome Signaling Are Required for Helicobacter pylori Adherence. Frontiers in cellular and infection microbiology 7 29114497
2025 The G protein modifier KCTD5 tunes the decoding of neuromodulatory signals necessary for motor function in striatal neurons. PLoS biology 2 40233107
2024 CD8+ T cell‑related KCTD5 contributes to malignant progression and unfavorable clinical outcome of patients with triple‑negative breast cancer. Molecular medicine reports 2 39027992
2026 Design of Inhibitory Peptides Based on TRPM4-KCTD5 Interaction. Journal of chemical information and modeling 0 42214084
2025 Heterozygous Kctd5 knockout mice exhibit abnormal lipid metabolism. The international journal of biochemistry & cell biology 0 40846050
2024 KCTD5 regulates Ikaros degradation induced by chemotherapeutic drug etoposide in hematological cells. Biological chemistry 0 38424700

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