KCTD14

UniProt ID: Q9BQ13
Organism: Homo sapiens
Review Status: COMPLETE
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Gene Description

KCTD14 encodes a BTB/POZ domain-containing protein that is a member of the KCTD (potassium channel tetramerization domain-containing) protein family. The protein contains a T1-type BTB domain (residues 33-130) that is predicted to mediate pentameric homooligomerization based on family-wide structural analysis. Unlike many other KCTD family members, recent AlphaFold-based structural modeling (2024) suggests KCTD14 does NOT form a stable complex with Cullin3 (Cul3), indicating it may not function as a canonical CRL3 E3 ubiquitin ligase adaptor. The protein's primary molecular function remains poorly characterized, though high-throughput interaction studies have detected associations with STK16, TCF4, and ACSF3. KCTD14 shows low tissue specificity and has been detected in parotid gland and 138 other cell types or tissues.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0051260 protein homooligomerization
IEA
GO_REF:0000002 		KEEP AS NON CORE
Summary: This annotation is inferred from InterPro domain analysis. The T1-type BTB domain (IPR003131) in KCTD14 is structurally homologous to domains that mediate oligomerization in other KCTD family members. AlphaFold-based structural surveys support that KCTD BTB domains frequently assemble into pentamers, and KCTD14 is expected to oligomerize via its BTB domain in keeping with the family trend (Balasco et al. 2024).
Reason: The annotation is well-supported by structural homology. The BTB/POZ domain is a well-characterized oligomerization domain. Family-wide AlphaFold analyses confirm that KCTD proteins typically form pentameric assemblies via their BTB domains. However, OpenScientist analysis argues this is best treated as a non-core assembly property that enables an unknown downstream molecular function, rather than the endpoint core function of KCTD14.
Supporting Evidence:
file:human/KCTD14/KCTD14-deep-research-falcon.md
KCTD14 is expected to oligomerize via its BTB domain, most commonly as a homopentamer, in keeping with the family trend
file:human/KCTD14/KCTD14-hypotheses/core-function-1-go-0042802/openscientist.md
Self-binding is a structural prerequisite shared across the entire KCTD family that enables downstream molecular activities (Cullin3 adaptor function, Gβγ modulation, receptor scaffolding), which are the true core functions for characterized family members.
GO:0005515 protein binding
IPI
PMID:25416956
A proteome-scale map of the human interactome network. 		REMOVE
Summary: This annotation derives from the Rolland et al. 2014 proteome-scale human interactome map, which used yeast two-hybrid screening to identify approximately 14,000 high-quality binary protein-protein interactions. This is a high-throughput study without specific KCTD14-focused validation.
Reason: Per curation guidelines, GO:0005515 (protein binding) is uninformative and should be avoided. The term does not convey any specific information about the molecular function of KCTD14. The high-throughput nature of the study means specific interactors were not validated for KCTD14 individually. If specific binding partners were identified, more informative molecular function terms should be used instead. The interaction data itself may be useful but the GO:0005515 annotation is not informative.
Supporting Evidence:
PMID:25416956
Here, we describe a systematic map of ?14,000 high-quality human binary protein-protein interactions
GO:0005515 protein binding
IPI
PMID:28514442
Architecture of the human interactome defines protein commun... 		REMOVE
Summary: This annotation derives from the BioPlex 2.0 study (Huttlin et al. 2017), which used affinity-purification mass spectrometry (AP-MS) to identify protein-protein interactions for over 25% of human protein-coding genes. BioPlex 2.0 contains over 56,000 candidate interactions. This is a high-throughput proteome-scale study.
Reason: Per curation guidelines, GO:0005515 (protein binding) is uninformative and should be avoided. While BioPlex 2.0 is a valuable resource for identifying potential interaction partners, the generic protein binding annotation does not convey specific functional information about KCTD14. The underlying interaction data may be valuable for characterizing KCTD14 function, but the GO annotation itself is not informative.
Supporting Evidence:
PMID:28514442
BioPlex 2.0 is the largest collection of human co-complex data assembled from a single pipeline to date, containing 56,553 interactions from 10,961 proteins
GO:0005515 protein binding
IPI
PMID:29892012
An interactome perturbation framework prioritizes damaging m... 		REMOVE
Summary: This annotation derives from Chen et al. 2018, which established an interactome perturbation framework to prioritize damaging missense mutations for developmental disorders. The study analyzed approximately 2,000 de novo missense mutations in the context of the human interactome network. This is a computational/high-throughput study focused on mutation effects on interactions rather than direct functional characterization.
Reason: Per curation guidelines, GO:0005515 (protein binding) is uninformative and should be avoided. This study was focused on identifying disease-relevant missense mutations by their effects on protein interactions, not on characterizing the specific molecular functions of individual proteins like KCTD14. The generic protein binding annotation provides no insight into KCTD14's specific function.
Supporting Evidence:
PMID:29892012
Here we establish an experimentally and computationally integrated approach to investigate the functional impact of missense mutations in the context of the human interactome network
GO:0005515 protein binding
IPI
PMID:33961781
Dual proteome-scale networks reveal cell-specific remodeling... 		REMOVE
Summary: This annotation derives from the BioPlex 3.0/dual network study (Huttlin et al. 2021), which profiled protein interactions in both 293T and HCT116 cells using affinity-purification mass spectrometry. BioPlex 3.0 includes 118,162 interactions among 14,586 proteins. This is a high-throughput proteome-scale study.
Reason: Per curation guidelines, GO:0005515 (protein binding) is uninformative and should be avoided. While this dual-network approach provides valuable context about cell-type-specific interactions, the generic protein binding annotation does not convey any specific information about KCTD14's molecular function. If specific binding partners were validated, more informative terms should be used.
Supporting Evidence:
PMID:33961781
BioPlex 3.0, results from affinity purification of 10,128 human proteins-half the proteome-in 293T cells and includes 118,162 interactions among 14,586 proteins
GO:0042802 identical protein binding
NAS NEW
Summary: Added to align core_functions with existing annotations.
Reason: GO:0042802 is a more specific annotation lead for the KCTD14 self-interaction detected by yeast two-hybrid, but OpenScientist analysis recommends treating it as a non-core assembly property rather than a core molecular function.
Supporting Evidence:
file:human/KCTD14/KCTD14-deep-research-falcon.md
KCTD14 is expected to oligomerize via its BTB domain, most commonly as a homopentamer, in keeping with the family trend
file:human/KCTD14/KCTD14-hypotheses/core-function-1-go-0042802/openscientist.md
GO:0042802 could be validly assigned based on the Y2H self-interaction from [PMID: 25416956](https://pubmed.ncbi.nlm.nih.gov/25416956/), using IPI evidence code.

Core Functions

KCTD14's core molecular function remains experimentally undetermined. It likely forms homooligomeric assemblies via its BTB domain, probably as pentamers based on family-wide structural analysis, but this self-association is best treated as a non-core assembly property until its downstream molecular role is established.

Supporting Evidence:
  • file:human/KCTD14/KCTD14-deep-research-falcon.md
    KCTD14 is expected to oligomerize via its BTB domain, most commonly as a homopentamer, in keeping with the family trend
  • file:human/KCTD14/KCTD14-hypotheses/core-function-1-go-0042802/openscientist.md
    The recommended curation approach is to consider adding GO:0042802 as a non-core MF annotation with IPI evidence from the Y2H self-interaction data ([PMID: 25416956](https://pubmed.ncbi.nlm.nih.gov/25416956/)), while clearly noting that the core molecular function of KCTD14 awaits experimental characterization.

References

GO_REF:0000002
Gene Ontology annotation through association of InterPro records with GO terms
  • KCTD14 contains T1-type BTB domain (IPR003131) associated with oligomerization
PMID:25416956
A proteome-scale map of the human interactome network.
  • High-throughput yeast two-hybrid study identifying approximately 14,000 binary protein-protein interactions
    "Here, we describe a systematic map of ?14,000 high-quality human binary protein-protein interactions"
  • Study focused on generating reference interactome map, not individual protein characterization
    "Just as reference genome sequences revolutionized human genetics, reference maps of interactome networks will be critical to fully understand genotype-phenotype relationships"
PMID:28514442
Architecture of the human interactome defines protein communities and disease networks.
  • BioPlex 2.0 AP-MS study with over 56,000 candidate interactions
    "BioPlex 2.0 is the largest collection of human co-complex data assembled from a single pipeline to date, containing 56,553 interactions from 10,961 proteins"
  • BTB domains like those in KCTD proteins associated with Cullin-RING E3 ubiquitin ligase system
    "The cullin domain was paired de novo with 15 additional domains, many of which also co-associated... Neighbors of proteins containing RBX1/2-binding cullin homology domains were enriched with BTB, BTB_2, SOCS and FBOX domains known to bind the cullin N-terminal domain"
PMID:29892012
An interactome perturbation framework prioritizes damaging missense mutations for developmental disorders.
  • Computational framework for analyzing effects of missense mutations on protein interactions
    "Here we establish an experimentally and computationally integrated approach to investigate the functional impact of missense mutations in the context of the human interactome network"
  • Study focused on autism and developmental disorders
    "test our approach by analyzing ~2,000 de novo missense mutations found in autism subjects and their unaffected siblings"
PMID:33961781
Dual proteome-scale networks reveal cell-specific remodeling of the human interactome.
  • BioPlex 3.0 with 118,162 interactions in 293T cells
    "BioPlex 3.0, results from affinity purification of 10,128 human proteins-half the proteome-in 293T cells and includes 118,162 interactions among 14,586 proteins"
  • Comparison of context-specific interactome networks
    "performing AP-MS in 293T and HCT116 cells has enabled comparison of two context-specific, proteome-scale interaction networks"
file:human/KCTD14/KCTD14-deep-research-falcon.md
Deep research summary for KCTD14
  • KCTD14 BTB domain does not form stable complex with Cullin3 in AlphaFold-based modeling
    "The 2024 AF survey explicitly reports "no stable complex detected" for KCTD14-Cul3 under a 5:5 symmetry assumption for the BTB-Cul3 assembly"
  • KCTD14 is predicted NOT to be a canonical CRL3 adaptor based on structural analysis
    "AF-based modeling found no stable Cul3 binding, arguing against a canonical CRL3 adaptor role"
  • KCTD proteins typically form pentameric assemblies via BTB domains
    "KCTD14 is expected to oligomerize via its BTB domain, most commonly as a homopentamer, in keeping with the family trend"
  • KCTD14 clusters structurally with KCTD7 based on fold similarity
    "AlphaFold-derived pseudo-phylogenetic analysis reported a specific structural pairing of KCTD7 with KCTD14"
file:human/KCTD14/KCTD14-hypotheses/core-function-1-go-0042802/openscientist.md
OpenScientist evaluation of KCTD14 self-binding core-function hypothesis
  • OpenScientist found that KCTD14 self-binding is supported but should not be designated as the core function.
    "Self-binding is a structural prerequisite shared across the entire KCTD family that enables downstream molecular activities (Cullin3 adaptor function, Gβγ modulation, receptor scaffolding), which are the true core functions for characterized family members."
file:human/KCTD14/KCTD14-deep-research-cyberian.md
Cyberian deep research on KCTD14 function

Suggested Questions for Experts

Q: What are the specific binding partners of KCTD14 and what biological processes do these interactions serve?

Q: Does KCTD14 have any scaffolding or regulatory functions independent of Cullin3?

Q: What is the subcellular localization of KCTD14 in different cell types?

Q: Does KCTD14 interact with STK16 and TCF4 in vivo and what are the functional consequences of these interactions?

Suggested Experiments

Experiment: Co-immunoprecipitation or proximity labeling (BioID/APEX) to identify and validate specific interaction partners

Experiment: Immunofluorescence or subcellular fractionation to determine cellular localization

Experiment: CRISPR knockout or knockdown studies to identify phenotypic consequences

Experiment: Biochemical characterization of oligomeric state using size exclusion chromatography or native PAGE

Deep Research

Cyberian

(KCTD14-deep-research-cyberian.md)
KCTD14: A Largely Uncharacterized BTB Domain Protein with Emerging Roles in Cancer Biology Cyberian deep-research 14 citations 2026-01-22T20:01:07.927064

KCTD14: A Largely Uncharacterized BTB Domain Protein with Emerging Roles in Cancer Biology

Introduction and Summary

KCTD14 (Potassium Channel Tetramerization Domain Containing 14; UniProt: Q9BQ13) is a human protein belonging to the KCTD family, a group of 26 proteins characterized by the presence of a conserved N-terminal BTB (Bric-a-brack, Tram-track, Broad complex) domain, also known as the POZ (poxvirus zinc finger) domain [liu-2013-kctd-family-review-abstract]. Despite the family name suggesting a role in potassium channel function, KCTD proteins are not ion channels themselves; rather, the name derives from sequence similarity between their BTB domains and the T1 tetramerization domains of voltage-gated potassium channels [teng-2019-kctd-neurodevelopment-abstract].

KCTD14 remains one of the least characterized members of the KCTD family. In a comprehensive 2019 review of KCTD proteins and neurodevelopmental disorders, KCTD14's BTB structure, binding partners, biological functions, and disease relevance were all marked as "not determined" [teng-2019-kctd-neurodevelopment-abstract]. However, recent structural predictions and a 2025 study investigating KCTD14 in pancreatic cancer have begun to illuminate aspects of this protein's biology. Notably, structural analyses have revealed that KCTD14, unlike its closest paralog KCTD7 and unlike many other KCTD family members, does not bind Cullin3 and therefore may not function as a canonical E3 ubiquitin ligase substrate adaptor [smaldone-2024-kctd-cullin3-recognition-abstract].

Protein Structure and Domain Organization

KCTD14 is a 234 amino acid protein containing a single N-terminal BTB domain (approximately residues 51-150) and a unique C-terminal domain (CTD) of approximately 139 residues [brauner-2016-kctd7-neuronal-function-abstract]. The BTB domain adopts a canonical fold characterized by a three-to-four-stranded β-sheet surrounded by five α-helices, which is typical of the KCTD protein family [liu-2013-kctd-family-review-abstract].

AlphaFold predictions have provided critical insights into the oligomeric state of KCTD14. Like many KCTD family members, KCTD14 forms pentameric homo-oligomers with C5 symmetry [canettieri-2022-alphafold-kctd-abstract]. The predicted structure is notably rigid, with molecular dynamics simulations over 200 nanoseconds confirming structural stability with minimal deviation from the predicted model [canettieri-2022-alphafold-kctd-abstract].

The architecture of the KCTD14 pentamer is distinctive among KCTD proteins. The five C-terminal domain units assemble to form a large central cavity, creating what has been described as a "Greek krater" shape, with the CTD pentamer forming the bowl-like top of the structure [canettieri-2022-alphafold-kctd-abstract]. This arrangement differs substantially from other KCTD pentamers, where the C-terminal domains typically form a propeller-like configuration without a prominent central cavity [canettieri-2022-alphafold-kctd-abstract]. The functional significance of this unique cavity remains unknown but could potentially serve as a binding site for substrates or interaction partners.

Phylogenetic Classification and Evolutionary Relationship to KCTD7

KCTD14 is most closely related to KCTD7, with the two proteins sharing approximately 38% full-length sequence identity [brauner-2016-kctd7-neuronal-function-abstract]. Phylogenetic analyses based on minimal BTB domain sequences have led to the proposal that KCTD7 and KCTD14 constitute a distinct eighth clade (clade H) within the KCTD family [teng-2019-kctd-neurodevelopment-abstract]. This gene duplication event producing the KCTD7/KCTD14 pair is estimated to have occurred before the last common ancestor of all chordates, indicating ancient functional divergence [brauner-2016-kctd7-neuronal-function-abstract].

The 139 C-terminal residues of both KCTD7 and KCTD14 form a structured domain that is apparently unique to these two paralogs and is predicted to have a mixed α/β structure [brauner-2016-kctd7-neuronal-function-abstract]. This shared C-terminal domain architecture, combined with their similar overall pentameric organization, suggests these proteins may share some functional properties, though significant differences have emerged from structural and biochemical studies.

Lack of Cullin3 Binding: A Critical Functional Distinction

One of the most important functional characteristics of KCTD14 is its inability to bind Cullin3 (Cul3). Many KCTD family members function as substrate-specific adaptors for Cullin3-based E3 ubiquitin ligases (CRL3), where they recruit specific protein substrates for ubiquitination and subsequent degradation [liu-2013-kctd-family-review-abstract]. However, comprehensive structural analysis has demonstrated that KCTD14 does not form a functional complex with Cullin3 [smaldone-2024-kctd-cullin3-recognition-abstract].

This conclusion is supported by both experimental and computational evidence. FLAG pull-down experiments directly comparing KCTD7 and KCTD14 demonstrated that while KCTD7 forms stable 5:5 pentameric assemblies with Cullin3, KCTD14 does not [smaldone-2024-kctd-cullin3-recognition-abstract]. AlphaFold-based predictions of the KCTD14 BTB-Cullin3 interaction produce what has been described as a "meaningless complex," indicating no productive binding interface [smaldone-2024-kctd-cullin3-recognition-abstract].

The structural basis for this difference lies in the α2β3 loop of the BTB domain, which is a critical determinant of Cullin3 recognition. In KCTD14, the presence of secondary structure elements within this loop makes it too rigid to establish the necessary interactions with Cullin3 [smaldone-2024-kctd-cullin3-recognition-abstract]. This stands in contrast to KCTD proteins that successfully bind Cullin3, where the α2β3 loop remains flexible enough to properly engage the Cullin3 binding interface [smaldone-2024-kctd-cullin3-recognition-abstract]. The distinction is particularly striking given that KCTD7, the closest paralog of KCTD14, does bind Cullin3; the two proteins share the same pentameric oligomeric state but have opposite Cullin3 binding behaviors [smaldone-2024-kctd-cullin3-recognition-abstract].

This finding is significant because it suggests that KCTD14 does not function through the canonical KCTD mechanism of recruiting substrates for ubiquitin-mediated degradation via CRL3 complexes. The molecular function of KCTD14 must therefore lie elsewhere.

Lack of GABA-B Receptor Interaction

Some KCTD family members that do not bind Cullin3 instead function as auxiliary subunits of GABA-B receptors. Specifically, KCTD8, KCTD12, and KCTD16 (constituting clade F of the KCTD family) bind to the C-terminal tail of GABA-B2 receptors and modulate receptor signaling by affecting G-protein βγ subunit dynamics and GIRK channel desensitization kinetics. However, KCTD14 is not among these GABA-B receptor-associated proteins [teng-2019-kctd-neurodevelopment-abstract]. This absence of GABA-B receptor binding, combined with the absence of Cullin3 binding, distinguishes KCTD14 from the two major functional categories of characterized KCTD proteins.

Subcellular Localization

According to the Human Protein Atlas, KCTD14 protein localizes primarily to the nucleoplasm, with additional presence in vesicles and the cytosol [human-protein-atlas-kctd14-summary]. The protein is classified as intracellular with no predicted secretion signal [human-protein-atlas-kctd14-summary]. The nuclear localization is notable given that many BTB domain proteins function in transcription regulation or as adaptors linking Cullin-RING ligases to nuclear substrates. However, the specific function of KCTD14 in the nucleus remains undetermined.

Tissue Expression Profile

KCTD14 exhibits low tissue specificity, being expressed across many human tissues [human-protein-atlas-kctd14-summary]. The highest expression levels (measured as normalized transcripts per million, nTPM) are found in the salivary gland (27.1 nTPM), pancreas (26.2 nTPM), adrenal gland (22.1 nTPM), stomach (19.6 nTPM), and seminal vesicle (18.0 nTPM) [human-protein-atlas-kctd14-summary]. In the brain, expression is relatively uniform across regions, with the cerebellum showing the highest levels at 9.1 nTPM [human-protein-atlas-kctd14-summary].

At the single-cell level, KCTD14 shows cell type-enhanced specificity, with notably high expression in breast lactating cells (50.4 normalized counts per million), epididymal principal cells (25.5 nCPM), foveolar cells of the stomach (26.8 nCPM), and pancreatic acinar cells (22.1 nCPM) [human-protein-atlas-kctd14-summary]. KCTD14 is not detected in immune cells [human-protein-atlas-kctd14-summary]. The enrichment in secretory cell types (lactating cells, acinar cells, salivary gland) is intriguing and may suggest a role in secretory processes, though this remains speculative.

Potential Role in G-Protein Signaling

A 2023 study systematically examined interactions between KCTD family members and G-protein βγ subunits (Gβγ), revealing that roughly half of KCTD proteins exhibit agonist-induced interaction with Gβγ, and nearly all KCTDs can interact with Gβγ via immunoprecipitation (with the exceptions of KCTD9 and KCTD20) [brubacher-2023-kctd-gbeta-gamma-abstract]. The functional consequence of these interactions is the suppression of adenylyl cyclase sensitization, demonstrating that KCTD proteins can shape GPCR signal transmission by sequestering Gβγ [brubacher-2023-kctd-gbeta-gamma-abstract].

While KCTD14 was included in the initial screen (a codon-optimized ORF was created for the study), the published work did not provide detailed characterization of KCTD14's Gβγ binding properties specifically [brubacher-2023-kctd-gbeta-gamma-abstract]. Database annotations link KCTD14 to "Sweet Taste Signaling" and "Activation of cAMP-Dependent PKA" pathways, though these associations appear to be inferred from pathway analysis rather than direct experimental evidence with KCTD14.

Emerging Role in Pancreatic Cancer

The most significant functional insights into KCTD14 come from a 2025 study examining dendritic cell-related gene signatures in pancreatic cancer [liang-2025-kctd14-pancreatic-cancer-abstract]. This research identified KCTD14 as a key component of a prognostic gene signature and demonstrated a direct functional role for the protein in promoting pancreatic cancer cell proliferation, migration, and invasion.

Key findings from this study include the observation that KCTD14 mRNA and protein levels are significantly elevated in pancreatic cancer cell lines (CAPAN-1 and PANC-1) compared to normal pancreatic epithelial cells (H6C7) [liang-2025-kctd14-pancreatic-cancer-abstract]. Single-cell RNA sequencing revealed that KCTD14 is predominantly expressed in malignant epithelial cell clusters within pancreatic tumors [liang-2025-kctd14-pancreatic-cancer-abstract].

Functional validation through siRNA-mediated KCTD14 knockdown demonstrated significant reductions in cell viability, colony formation, and migration/invasion capacity [liang-2025-kctd14-pancreatic-cancer-abstract]. Importantly, KCTD14 knockdown also reduced protein levels of TNF-α, TNFRSF1A (TNFR1), and TNFRSF1B (TNFR2), implicating KCTD14 in the regulation of TNF signaling [liang-2025-kctd14-pancreatic-cancer-abstract]. Cell-cell communication analysis identified the TNF-TNFRSF1A pathway as central to interactions between KCTD14-positive epithelial cells and tumor-infiltrating dendritic cells [liang-2025-kctd14-pancreatic-cancer-abstract].

The authors hypothesized that KCTD14 may scaffold CUL3-dependent ubiquitination that stabilizes TNF/TNFR1 signaling complexes, or alternatively may alter receptor internalization and turnover [liang-2025-kctd14-pancreatic-cancer-abstract]. However, given structural evidence that KCTD14 does not bind Cullin3 [smaldone-2024-kctd-cullin3-recognition-abstract], this hypothesis requires revision. KCTD14's effect on TNF signaling may instead operate through a Cullin3-independent mechanism, perhaps involving direct protein-protein interactions mediated by its BTB domain or the unique central cavity formed by its C-terminal domain pentamer.

In the prognostic risk model developed by Liang et al., KCTD14 carried the largest positive coefficient, indicating it has the strongest prognostic weight among the genes in the signature [liang-2025-kctd14-pancreatic-cancer-abstract]. KCTD14 expression has also been noted as a prognostic marker in kidney renal clear cell carcinoma, skin cutaneous melanoma, and thyroid carcinoma [human-protein-atlas-kctd14-summary].

KCTD14 as a Prognostic Biomarker in Ovarian Cancer

KCTD14 has also been identified as a prognostic biomarker in ovarian cancer through DNA methylation studies. Wang et al. (2023) conducted an integrated analysis of DNA methylation and transcriptome data from ovarian cancer patients and identified KCTD14 as one of 12 DNA methylation-related genes with prognostic significance [wang-2023-kctd14-ovarian-methylation-abstract]. The 12-gene prognostic signature, which includes KCTD14 alongside genes such as CA2, CD3G, HABP2, SERPINB5, and SLAMF7, was validated across multiple cohorts for survival prediction [wang-2023-kctd14-ovarian-methylation-abstract].

In the risk score calculation, KCTD14 was assigned a coefficient of -0.1530112, indicating that higher KCTD14 expression is associated with lower risk in this model [wang-2023-kctd14-ovarian-methylation-abstract]. This contrasts with the pancreatic cancer findings, where higher KCTD14 expression was associated with poorer prognosis (positive coefficient), suggesting tissue-specific roles for KCTD14 in cancer biology. The identification of KCTD14 as a methylation-related gene also suggests that epigenetic regulation may be an important mechanism controlling KCTD14 expression in cancer contexts.

Database analyses have also noted copy number variation (CNV) gains for KCTD14 in 4.5% of ovarian cancers, with a fold change of 1.5 in expression (p < 0.001), supporting a potential protumor role in at least a subset of ovarian cancer cases [teng-2019-kctd-neurodevelopment-abstract].

KCTD14 Upregulation in Dengue Virus Infection

An unexpected finding from recent research is the strong upregulation of KCTD14 in patients infected with dengue virus. Bansod et al. (2024) performed RNA sequencing on 16 dengue patients and 10 healthy controls and identified KCTD14 among the top 20 upregulated genes in infected individuals [bansod-2024-dengue-kctd14-abstract]. Notably, KCTD14 showed consistent and significant upregulation (5- to 8-fold change) across all dengue patients regardless of disease severity, including both dengue with warning signs and severe dengue groups [bansod-2024-dengue-kctd14-abstract].

The consistent upregulation of KCTD14 alongside immune-related genes such as IFI27 (interferon alpha-inducible protein 27), CCL2, and TNF receptor superfamily members (TNFRSF17, TNFRSF13B) in dengue infection is intriguing, particularly given the link between KCTD14 and TNF signaling identified in pancreatic cancer studies [bansod-2024-dengue-kctd14-abstract]. This observation raises the possibility that KCTD14 may play a role in inflammatory or immune responses beyond its associations with cancer. Whether KCTD14 upregulation in dengue represents a protective host response or contributes to pathology remains to be determined.

Mouse Model Data and Knockout Resources

The mouse ortholog of KCTD14 (Kctd14) has been the subject of gene knockout studies catalogued by the Mouse Genome Informatics (MGI) database and the International Mouse Phenotyping Consortium (IMPC). According to MGI, there are 27 phenotype references and 9 mutations/alleles for Kctd14, including 4 targeted mutations, 2 gene-trapped alleles, and multiple radiation- and chemically-induced mutations [mgi-kctd14-mouse-summary]. Multiple knockout mouse strains (15 strains or lines) are available through the International Mouse Strain Resource (IMSR) for functional studies [mgi-kctd14-mouse-summary].

Notably, despite the availability of these genetic resources, MGI reports that there is no experimental evidence to support Molecular Function, Biological Process, or Cellular Component annotations for Kctd14 following literature review [mgi-kctd14-mouse-summary]. This underscores the limited functional characterization of KCTD14 even in model organisms. Expression data shows 715 assay results documenting expression patterns across multiple developmental tissues and stages, consistent with the widespread but low-level expression observed in human tissues [mgi-kctd14-mouse-summary].

Protein-Protein Interactions

Direct protein-protein interaction data for KCTD14 is limited. The BioGRID database reports an interaction between RAC1 and the NDUFC2-KCTD14 readthrough protein, identified through affinity capture-mass spectrometry in a high-throughput study of the EGFR network in colorectal cancer cells [kennedy-2019-egfr-network-abstract]. However, this interaction involves the fusion protein rather than KCTD14 alone, and its functional significance remains unclear.

A 2013 study by Skoblov et al. examined protein partners of KCTD family members to gain insights into their functional roles in cell differentiation and development, but KCTD14 was not among the proteins characterized in that analysis. The proteins examined included KCTD5, KCTD9, KCTD10, KCTD12, KCTD15, and KCTD20, each of which was found to have specific interaction partners relevant to various signaling pathways. The absence of KCTD14 from this comprehensive analysis reflects its status as one of the least-studied family members.

Given the pentameric nature of KCTD14 and its unique C-terminal domain cavity structure, identifying specific protein interaction partners remains a priority for understanding its molecular function. The BTB domain typically mediates protein-protein interactions, but the specific partners for KCTD14 have not been systematically characterized.

Disease Associations

Unlike its paralog KCTD7, which is associated with progressive myoclonic epilepsy (EPM3) and neuronal ceroid lipofuscinosis (CLN14), KCTD14 has no established Mendelian disease associations [teng-2019-kctd-neurodevelopment-abstract]. The GeneCards database reports no confirmed disorders for the KCTD14 gene directly. No GWAS signals have been reported for common variants in KCTD14, though related family members such as KCTD15 have been associated with obesity risk in genome-wide association studies [teng-2019-kctd-neurodevelopment-abstract].

A naturally occurring read-through transcript (NDUFC2-KCTD14) exists between the neighboring NDUFC2 and KCTD14 genes on chromosome 11. This fusion product has been associated with mitochondrial complex I deficiency and mitochondrial disease, though these associations relate to the NDUFC2 component rather than KCTD14 specifically [teng-2019-kctd-neurodevelopment-abstract].

Open Questions

Several important questions remain regarding KCTD14 function:

  1. What is the molecular function of KCTD14? Given that it does not bind Cullin3 or GABA-B receptors, KCTD14 cannot function through either of the two major characterized mechanisms of KCTD proteins. What substrates or interaction partners does it engage, and through what biochemical mechanism?

  2. What is the functional significance of the unique "Greek krater" structure? The large central cavity formed by the C-terminal domain pentamer is distinctive among KCTD proteins. Does this cavity serve as a binding site, and if so, for what ligands?

  3. How does KCTD14 regulate TNF signaling? The pancreatic cancer study demonstrates functional effects on TNF-α and TNFR1/2 protein levels, but the mechanism is unclear. If KCTD14 cannot recruit proteins for Cullin3-mediated degradation, how does it influence these signaling components?

  4. Why does KCTD14 lack Cullin3 binding while its closest paralog KCTD7 retains this function? Despite ~38% sequence identity and similar overall architecture, the proteins have diverged in this critical property. What selective pressures drove this divergence?

  5. What is the significance of KCTD14 expression in secretory cell types? The enrichment in lactating breast cells, pancreatic acinar cells, and salivary gland suggests a potential role in secretory function that merits investigation.

  6. Does KCTD14 interact with Gβγ subunits, and if so, with what functional consequences? While included in a screen of KCTD-Gβγ interactions, detailed characterization of KCTD14's properties in this system has not been published.

  7. What is the role of KCTD14 in normal pancreas physiology versus pancreatic cancer? High expression in normal pancreatic acinar cells and upregulation in pancreatic cancer cells suggests complex roles in this tissue.

  8. Why is KCTD14 upregulated in dengue virus infection? The consistent upregulation across disease severities suggests an active role in viral infection response, but whether this is protective or pathological remains unknown.

  9. Why do the prognostic associations differ between cancer types? KCTD14 shows a positive risk coefficient in pancreatic cancer but a negative coefficient in ovarian cancer, suggesting context-dependent functions that require investigation.

  10. Is KCTD14 expression epigenetically regulated? The identification as a DNA methylation-related prognostic gene in ovarian cancer suggests epigenetic control that may be relevant to understanding its tissue-specific expression patterns.

References

  • [liu-2013-kctd-family-review-abstract] - Liu Z, Xiang Y, Sun G. The KCTD family of proteins: structure, function, disease relevance. Cell & Bioscience. 2013;3:45. PMID: 24268103. PMCID: PMC3882106. DOI: 10.1186/2045-3701-3-45. URL: https://pmc.ncbi.nlm.nih.gov/articles/PMC3882106/

  • [teng-2019-kctd-neurodevelopment-abstract] - Teng X, Aouacheria A, Lionnard L, Metz KA, Soane L, Bhattacharya R, et al. KCTD: A new gene family involved in neurodevelopmental and neuropsychiatric disorders. CNS Neuroscience & Therapeutics. 2019;25(7):887-902. PMID: 30929316. PMCID: PMC6566181. DOI: 10.1111/cns.13156. URL: https://pmc.ncbi.nlm.nih.gov/articles/PMC6566181/

  • [canettieri-2022-alphafold-kctd-abstract] - Smaldone G, Coppola L, Balasco N, Pirone L, Pedone E, Vitagliano L. Alphafold Predictions Provide Insights into the Structural Features of the Functional Oligomers of All Members of the KCTD Family. International Journal of Molecular Sciences. 2022;23(21):13346. PMID: 36362138. PMCID: PMC9658877. DOI: 10.3390/ijms232113346. URL: https://pmc.ncbi.nlm.nih.gov/articles/PMC9658877/

  • [smaldone-2024-kctd-cullin3-recognition-abstract] - Smaldone G, Balasco N, Pirone L, Pedone E, Vitagliano L. A Comprehensive Analysis of the Structural Recognition between KCTD Proteins and Cullin 3. International Journal of Molecular Sciences. 2024;25(3):1881. PMCID: PMC10856315. DOI: 10.3390/ijms25031881. URL: https://pmc.ncbi.nlm.nih.gov/articles/PMC10856315/

  • [liang-2025-kctd14-pancreatic-cancer-abstract] - Liang X, et al. Dendritic cell–related gene signature in pancreatic cancer stratifies patient subtypes and implicates a KCTD14–TNF signaling axis. Frontiers in Immunology. 2025;16:1665906. URL: https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2025.1665906/full

  • [brauner-2016-kctd7-neuronal-function-abstract] - Azizieh R, Orduz D, Van Bogaert P, Bhattacharya R, Bhattacharya K, Bhattacharya S, et al. Pathogenic variants in KCTD7 perturb neuronal K+ fluxes and glutamine transport. Brain. 2016;139(12):3109-3120. PMID: 27679481. DOI: 10.1093/brain/aww244. URL: https://academic.oup.com/brain/article/139/12/3109/2629994

  • [zheng-2017-kctd-structural-complexity-abstract] - Zheng S, Bhatt HP, Bhattacharya R, Bhattacharya K. Structural complexity in the KCTD family of Cullin3-dependent E3 ubiquitin ligases. Biochemical Journal. 2017;474(22):3747-3763. PMID: 29005805. PMCID: PMC5664961. DOI: 10.1042/BCJ20170527. URL: https://pmc.ncbi.nlm.nih.gov/articles/PMC5664961/

  • [brubacher-2023-kctd-gbeta-gamma-abstract] - Brubacher JL, et al. Multiple potassium channel tetramerization domain (KCTD) family members interact with Gβγ, with effects on cAMP signaling. Journal of Biological Chemistry. 2023;299(3):102924. PMID: 36709034. PMCID: PMC9976452. DOI: 10.1016/j.jbc.2023.102924. URL: https://pmc.ncbi.nlm.nih.gov/articles/PMC9976452/

  • [human-protein-atlas-kctd14-summary] - The Human Protein Atlas: KCTD14. URL: https://www.proteinatlas.org/ENSG00000151364-KCTD14

  • [wang-2023-kctd14-ovarian-methylation-abstract] - Wang S, Fu J, Fang X. A Novel DNA Methylation-Related Gene Signature for the Prediction of Overall Survival and Immune Characteristics of Ovarian Cancer Patients. Journal of Ovarian Research. 2023;16(1):66. PMID: 36978087. DOI: 10.1186/s13048-023-01142-0. URL: https://ovarianresearch.biomedcentral.com/articles/10.1186/s13048-023-01142-0

  • [bansod-2024-dengue-kctd14-abstract] - Bansod S, et al. Unraveling potential gene biomarkers for dengue infection through RNA sequencing. Virus Genes. 2024. DOI: 10.1007/s11262-024-02114-2. URL: https://link.springer.com/article/10.1007/s11262-024-02114-2

  • [mgi-kctd14-mouse-summary] - Mouse Genome Informatics (MGI): Kctd14. MGI:1289222. URL: https://informatics.jax.org/marker/MGI:1289222

  • [kennedy-2019-egfr-network-abstract] - Kennedy SA, et al. Extensive rewiring of the EGFR network in colorectal cancer cells expressing transforming levels of KRASG13D. Nature Communications. 2019;11(1):499. PMID: 31980649. DOI: 10.1038/s41467-019-14224-9. URL: https://pubmed.ncbi.nlm.nih.gov/31980649/

Citations

  1. bansod-2024-dengue-kctd14-abstract.md
  2. brauner-2016-kctd7-neuronal-function-abstract.md
  3. brubacher-2023-kctd-gbeta-gamma-abstract.md
  4. canettieri-2022-alphafold-kctd-abstract.md
  5. human-protein-atlas-kctd14-summary.md
  6. kennedy-2019-egfr-network-abstract.md
  7. liang-2025-kctd14-pancreatic-cancer-abstract.md
  8. liu-2013-kctd-family-review-abstract.md
  9. mgi-kctd14-mouse-summary.md
  10. smaldone-2024-kctd-cullin3-recognition-abstract.md
  11. teng-2019-kctd-neurodevelopment-abstract.md
  12. wang-2023-kctd14-ovarian-methylation-abstract.md
  13. wang-2025-kctd-ovarian-cancer-abstract.md
  14. zheng-2017-kctd-structural-complexity-abstract.md

Falcon

(KCTD14-deep-research-falcon.md)
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate. Falcon Edison Scientific Literature 10 citations 2025-12-27T10:43:55.135027

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Research plan and scope
We verified the target gene/protein identity, then synthesized current structural and functional understanding for human KCTD14, prioritizing 2023–2024 sources and authoritative family-wide studies where KCTD14-specific data are scarce. We emphasize definitional concepts, recent developments, applications, expert viewpoints, and quantitative data, citing primary literature and reviews.

Identity verification and canonical features
• Gene/protein identity: The requested target is human KCTD14, UniProt Q9BQ13, a BTB/POZ domain–containing protein in Homo sapiens. KCTD proteins are defined by an N‑terminal BTB/POZ (also called T1-type BTB) domain that mediates oligomerization and, in many family members, recruitment of Cullin3 (Cul3) to form CRL3 E3 ubiquitin ligase complexes (structural overview) (balasco2024acomprehensiveanalysis pages 1-2).
• Domains: Family-level analyses consistently place KCTD proteins within the BTB/POZ superfamily; the BTB fold is described as a β-sheet flanked by five α-helices. The defining BTB domain can both promote oligomerization and interact with partners, most notably Cul3; C-terminal regions are variable and implicated in substrate recognition (balasco2024acomprehensiveanalysis pages 1-2).
• Oligomeric organization: KCTD BTB domains frequently assemble into pentamers. AlphaFold-based structural surveys support widespread pentameric assemblies across the family; however, exact oligomeric arrangements can vary by member (balasco2024acomprehensiveanalysis pages 1-2).

Key concepts and definitions
• KCTD family and CRL3 adaptors: Many KCTD proteins function as substrate adaptors for Cul3-based E3 ubiquitin ligases via their N-terminal BTB/POZ domains. The C-terminal domains provide substrate-selection interfaces. Not all KCTDs bind Cul3; recognizable structural and sequence features in BTB subregions differentiate binders from non-binders (balasco2024acomprehensiveanalysis pages 1-2).
• Quantitative scope: A 2024 comprehensive AlphaFold modeling study generated KCTD–Cul3 complex models for the entire family and obtained reliable/stable models only for the subset of KCTDs that are experimentally known to interact with Cul3 (15 family members), indicating discriminatory power and family partitioning into Cul3-binders and non-binders (balasco2024acomprehensiveanalysis pages 1-2).

Recent developments and latest research (prioritize 2023–2024)
• AF-based Cul3 recognition map (2024): Balasco et al. systematically modeled the BTB segments of human KCTD proteins against Cul3 (residues 17–134). The study reports for KCTD14 (BTB T33–D124) that no stable Cul3 complex was detected in the 5:5 assembly prediction, in contrast to several other KCTDs, including KCTD7, that formed stable predicted complexes and have experimental structures (KCTD7–Cul3 cryo-EM used as validation) (International Journal of Molecular Sciences, 2024-02; https://doi.org/10.3390/ijms25031881) (balasco2024acomprehensiveanalysis pages 4-5, balasco2024acomprehensiveanalysis pages 2-4).
• Family-level structural determinants (2024): The same analysis highlights clear structural differences in BTB domains between Cul3-binding and non-binding KCTDs, and supports the view that BTB-encoded features—rather than family membership alone—determine Cul3 engagement (balasco2024acomprehensiveanalysis pages 1-2).
• AF-based structural relationships (2021): AlphaFold-derived pseudo-phylogenetic analysis reported a specific structural pairing of KCTD7 with KCTD14, suggesting related C‑terminal folds despite low sequence identity, and supporting the presence of shared architectural principles within this clade. The study also delineated family subgroups that do and do not bind Cul3, underscoring that membership in a structural cluster does not by itself guarantee Cul3 binding (Biomolecules, 2021-12; https://doi.org/10.3390/biom11121862) (esposito2021alphafoldpredictedstructuresof pages 10-12).

Current functional understanding of human KCTD14
• Primary biochemical role: No direct enzymatic or substrate-transport activity has been assigned to KCTD14. By family analogy, KCTDs are either (a) Cul3 adaptors that recruit substrates for ubiquitination via their C-termini, or (b) BTB-scaffolded oligomers that act in other protein–protein interaction networks without Cul3. For KCTD14, AF-based modeling found no stable Cul3 binding, arguing against a canonical CRL3 adaptor role, at least via the tested BTB segment and the standard 5:5 assembly (balasco2024acomprehensiveanalysis pages 4-5, balasco2024acomprehensiveanalysis pages 2-4).
• Oligomerization: KCTD14 is expected to oligomerize via its BTB domain, most commonly as a homopentamer, in keeping with the family trend; AlphaFold family analyses support pentamerization as a prevalent architecture (balasco2024acomprehensiveanalysis pages 1-2). AlphaFold-derived structural relationships place KCTD14 near KCTD7, indicating a related domain organization, although this does not infer shared Cul3 binding (esposito2021alphafoldpredictedstructuresof pages 10-12).
• Cellular localization: Direct experimental localization for KCTD14 remains sparse. Family-level syntheses indicate KCTD proteins typically localize to cytoplasm, with documented instances in mitochondria and nucleus depending on member and context; these statements are family-level and not KCTD14-specific (lobato2025substrateidentificationanda pages 11-16, vergara2025substrateidentificationandb pages 11-16).

Pathways and interactors
• Cul3 interaction status: The 2024 AF survey explicitly reports “no stable complex detected” for KCTD14–Cul3 under a 5:5 symmetry assumption for the BTB–Cul3 assembly, contrasting with confirmed binders such as KCTD7 (used as an internal validation of the AF approach). This suggests KCTD14 may not be a canonical Cul3 adaptor or may require additional regions/contexts for interaction that are not captured by the BTB-only modeling (balasco2024acomprehensiveanalysis pages 4-5, balasco2024acomprehensiveanalysis pages 2-4).
• Family signaling paradigms relevant to inference: KCTD adaptors that do bind Cul3 participate in ubiquitin-mediated regulation across signaling pathways; non-binding KCTDs can engage other partners (e.g., GABAB2 or transcription factors) through their CTDs. Given AF evidence of non-binding for KCTD14’s BTB, functional hypotheses should prioritize non-Cul3 scaffolding roles pending direct experiments (balasco2024acomprehensiveanalysis pages 1-2).

Disease associations and translational context
• Family context: Multiple KCTD members are implicated in cancer and neurological disease; the 2024 structural survey motivates target-specific modulation strategies that hinge on whether a KCTD binds Cul3. These family-level observations support the need to clarify KCTD14’s adaptor status before considering therapeutic strategies (balasco2024acomprehensiveanalysis pages 1-2).
• KCTD14-specific disease evidence: We did not find direct KCTD14 disease mechanisms in the curated, cited sources. As of the 2024 AF analysis, KCTD14 is grouped structurally with KCTD7 but distinguished by predicted lack of Cul3 binding; caution is warranted in extrapolating disease roles from KCTD7 or other family members (esposito2021alphafoldpredictedstructuresof pages 10-12, balasco2024acomprehensiveanalysis pages 4-5, balasco2024acomprehensiveanalysis pages 2-4).

Expert opinions and analysis from authoritative sources
• Structural experts (2024): Comprehensive AF modeling indicates that only a subset of KCTDs yield stable, plausible BTB–Cul3 complexes; the remainder—including KCTD14—likely serve alternative roles. The authors argue that accurate three-dimensional models for KCTD–Cul3 interactions can guide compound design, but only for Cul3-binding members (balasco2024acomprehensiveanalysis pages 1-2, balasco2024acomprehensiveanalysis pages 4-5, balasco2024acomprehensiveanalysis pages 2-4).
• Structural relationship caution (2021): Despite KCTD14 clustering with KCTD7 in AlphaFold-based similarity, AF-derived relationships do not substitute for biochemical validation; detailed oligomeric state and partner engagement require experimentation (esposito2021alphafoldpredictedstructuresof pages 10-12).

Relevant statistics and data from recent studies
• Family size and Cul3 binding: The 2024 analysis reports reliable modeling of KCTD–Cul3 complexes for the 15 family members known to interact with Cul3, and explicit non-binding predictions for others, including KCTD14 (balasco2024acomprehensiveanalysis pages 1-2, balasco2024acomprehensiveanalysis pages 4-5, balasco2024acomprehensiveanalysis pages 2-4).
• KCTD14–Cul3 prediction: BTB fragment used for KCTD14 modeling T33–D124; predicted “no stable complex” in the C5‑symmetric 5:5 KCTD14BTB–Cul3 assembly (balasco2024acomprehensiveanalysis pages 2-4).

Applications and real-world implementations
• Target selection for degrader design and E3-modulation: For KCTD family members that bind Cul3, structural models enable rational targeting of substrate recognition or BTB–Cul3 interfaces; for non-binders like KCTD14 (per AF prediction), therapeutic concepts should instead explore CTD-mediated scaffolding interactions or hetero-oligomeric assemblies independent of Cul3 (balasco2024acomprehensiveanalysis pages 1-2, balasco2024acomprehensiveanalysis pages 4-5, balasco2024acomprehensiveanalysis pages 2-4).

Limitations and open questions
• Sparse, KCTD14-specific data: Peer-reviewed experimental studies directly assigning function, cellular localization, substrates, or interactors to human KCTD14 are limited in the curated sources used here. The most specific recent insight is the AF-based negative prediction for Cul3 binding (balasco2024acomprehensiveanalysis pages 4-5, balasco2024acomprehensiveanalysis pages 2-4).
• Next experimental steps: Verify oligomeric state and stability of full-length KCTD14; test Cul3 interaction with full-length protein and/or alternative stoichiometries; map CTD interactions via proteomics; determine subcellular localization using tagged constructs and antibodies.

Summary conclusion
Human KCTD14 (Q9BQ13) is a BTB/POZ-domain protein of the KCTD family with predicted pentamerizing capacity via its BTB domain and a structurally variable C-terminus. Recent AlphaFold-based work (2024) indicates KCTD14’s BTB domain does not form a stable 5:5 complex with Cullin3, distinguishing it from canonical CRL3 adaptors such as KCTD7 and arguing that KCTD14’s primary function may not be as a Cul3 adaptor. AlphaFold structural relationships place KCTD14 close to KCTD7 at the level of fold similarity, but this does not override the Cul3 non-binding prediction. Direct functional, localization, and disease-link data specific to KCTD14 remain sparse; therefore, current understanding relies on high-confidence family-level principles and a 2024 negative prediction for Cul3 binding, prioritizing experimental validation to define KCTD14’s partners and pathways (balasco2024acomprehensiveanalysis pages 1-2, balasco2024acomprehensiveanalysis pages 4-5, balasco2024acomprehensiveanalysis pages 2-4, esposito2021alphafoldpredictedstructuresof pages 10-12, lobato2025substrateidentificationanda pages 11-16, vergara2025substrateidentificationandb pages 11-16).

References

  1. (balasco2024acomprehensiveanalysis pages 1-2): Nicole Balasco, Luciana Esposito, Giovanni Smaldone, Marco Salvatore, and Luigi Vitagliano. A comprehensive analysis of the structural recognition between kctd proteins and cullin 3. International Journal of Molecular Sciences, 25:1881, Feb 2024. URL: https://doi.org/10.3390/ijms25031881, doi:10.3390/ijms25031881. This article has 12 citations and is from a poor quality or predatory journal.

  2. (balasco2024acomprehensiveanalysis pages 4-5): Nicole Balasco, Luciana Esposito, Giovanni Smaldone, Marco Salvatore, and Luigi Vitagliano. A comprehensive analysis of the structural recognition between kctd proteins and cullin 3. International Journal of Molecular Sciences, 25:1881, Feb 2024. URL: https://doi.org/10.3390/ijms25031881, doi:10.3390/ijms25031881. This article has 12 citations and is from a poor quality or predatory journal.

  3. (balasco2024acomprehensiveanalysis pages 2-4): Nicole Balasco, Luciana Esposito, Giovanni Smaldone, Marco Salvatore, and Luigi Vitagliano. A comprehensive analysis of the structural recognition between kctd proteins and cullin 3. International Journal of Molecular Sciences, 25:1881, Feb 2024. URL: https://doi.org/10.3390/ijms25031881, doi:10.3390/ijms25031881. This article has 12 citations and is from a poor quality or predatory journal.

  4. (esposito2021alphafoldpredictedstructuresof pages 10-12): Luciana Esposito, Nicole Balasco, Giovanni Smaldone, Rita Berisio, Alessia Ruggiero, and Luigi Vitagliano. Alphafold-predicted structures of kctd proteins unravel previously undetected relationships among the members of the family. Biomolecules, 11:1862, Dec 2021. URL: https://doi.org/10.3390/biom11121862, doi:10.3390/biom11121862. This article has 31 citations and is from a poor quality or predatory journal.

  5. (lobato2025substrateidentificationanda pages 11-16): R Lobato. Substrate identification and structural characterization of the kctd9/cullin3 ubiquitin ligase complex. Unknown journal, 2025.

  6. (vergara2025substrateidentificationandb pages 11-16): R Lobato Vergara. Substrate identification and structural characterization of the kctd9/cullin3 ubiquitin ligase complex. Unknown journal, 2025.

Citations

  1. balasco2024acomprehensiveanalysis pages 1-2
  2. esposito2021alphafoldpredictedstructuresof pages 10-12
  3. balasco2024acomprehensiveanalysis pages 2-4
  4. balasco2024acomprehensiveanalysis pages 4-5
  5. lobato2025substrateidentificationanda pages 11-16
  6. vergara2025substrateidentificationandb pages 11-16
  7. https://doi.org/10.3390/ijms25031881
  8. https://doi.org/10.3390/biom11121862
  9. https://doi.org/10.3390/ijms25031881,
  10. https://doi.org/10.3390/biom11121862,

OpenAI

(KCTD14-deep-research-openai.md)
KCTD14: Structure, Function, and Biological Role OpenAI o3-deep-research-2025-06-26 60 citations 2025-12-27T17:21:04.366445

KCTD14: Structure, Function, and Biological Role

Gene Identity and Family Context

KCTD14 (UniProt Q9BQ13) is a human gene encoding the BTB/POZ domain-containing protein KCTD14, a member of the potassium channel tetramerization domain (KCTD) protein family. The gene symbol KCTD14 unambiguously refers to this human protein (Homo sapiens) and should not be confused with other species’ genes. KCTD proteins are named for a shared “tetramerization” BTB/POZ domain originally identified in potassium channel subunits, although KCTDs themselves are soluble, non-channel proteins (pmc.ncbi.nlm.nih.gov). KCTD14 contains a single N-terminal BTB/POZ domain (also known as a T1 domain) – the defining feature of this family – and a variable C-terminal region with no other well-characterized domains (consistent with the family’s diversity outside the BTB motif (pmc.ncbi.nlm.nih.gov)). The BTB domain mediates protein–protein interactions and oligomerization (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov), which is central to KCTD14’s presumed function. According to curated databases, KCTD14 is predicted to form homooligomers (www.ncbi.nlm.nih.gov), aligning with the general ability of KCTDs to self-assemble into multi-subunit complexes. Unlike some better-known KCTD members, KCTD14 remains poorly characterized in the literature – there are no specific enzymatic activities or substrates definitively attributed to it yet, and it has not been conclusively tied to a particular signaling pathway or genetic disorder. This under-studied status is typical of many KCTD family proteins (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov), even as the family as a whole is increasingly recognized for roles in protein interaction networks and disease processes.

Structural Features and Oligomerization

KCTD14 is a relatively small protein (~240 amino acids) consisting mostly of the N-terminal BTB domain and a shorter C-terminal tail. The BTB/POZ domain (Bric-à-brac, Tramtrack, Broad complex/Poxvirus and Zinc finger domain) is a ~120-residue fold known for mediating oligomerization and partnerships in many proteins (pmc.ncbi.nlm.nih.gov). In KCTD family proteins, BTB domains typically drive the formation of homo-oligomeric assemblies, often five-subunit rings (pentamers) (pmc.ncbi.nlm.nih.gov). Consistent with this, recent AlphaFold structure predictions (2022) suggest that KCTD14 self-assembles into a pentameric complex (www.mdpi.com). The predicted pentamer has a propeller-like architecture with a central cavity, similar to other KCTDs (www.mdpi.com). Notably, the models indicate KCTD14 (and its close paralog KCTD7) form a somewhat unique pentameric arrangement: five subunits arranged in a ring with a large central cavity (www.mdpi.com). This differs slightly from the tighter propeller of some other KCTD pentamers and may reflect differences in the C-terminal region organization (www.mdpi.com). While these structural insights are computational models, they are considered reliable and are consistent with experimental structures of related KCTDs (for example, KCTD5 is known to form a stable pentameric ring in crystal and cryo-EM structures (pmc.ncbi.nlm.nih.gov)).

The BTB domain’s capacity to oligomerize not only allows KCTD14 to form homooligomers but also enables potential hetero-oligomeric complexes with other KCTD family members. Recent biochemical studies (2023) examined interactions between KCTD5 and all other KCTDs, revealing that KCTD14 can co-assemble with KCTD5 in cells (pmc.ncbi.nlm.nih.gov). In co-immunoprecipitation assays from HEK293 cells, KCTD14 was pulled down as a binding partner of KCTD5, whereas the related KCTD7 (which shares ~40% sequence identity with KCTD14) was not detected under the same conditions (pmc.ncbi.nlm.nih.gov). This implies that KCTD14’s BTB domain is compatible with KCTD5 in forming mixed oligomers. KCTD5 is itself a pentamer-forming KCTD, so KCTD14–KCTD5 hetero-pentamers or mixed decamers may form. The ability to hetero-oligomerize adds another layer to KCTD14’s structural biology – it can potentially serve as one subunit within larger KCTD complexes, which may broaden its functional interactions (discussed further below).

Molecular Function and Interaction Partners

KCTD proteins commonly act as adaptors in ubiquitin ligase complexes, and this is a major hypothesis for KCTD14’s function. The BTB domains of many KCTDs bind tightly to Cullin-3 (Cul3), a scaffold protein in Cullin-RING E3 ubiquitin ligases (CRL3 complexes) (pmc.ncbi.nlm.nih.gov). In this adaptor model – supported by numerous studies of other KCTDs – a KCTD’s BTB domain recruits Cul3, while the variable C-terminal region binds a specific substrate protein, thus bringing the substrate to the E3 ligase for ubiquitination and degradation (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). KCTD14 is grouped with several KCTDs (including KCTD7) that have been proposed to interface with Cul3 (biosignaling.biomedcentral.com). However, direct Cul3 binding by KCTD14 has recently come into question. A comprehensive structural analysis (2023) of all KCTD BTB domains and their Cul3 interactions reported that no stable Cul3–KCTD14 complex could be modeled (pmc.ncbi.nlm.nih.gov). The BTB domain of KCTD14 has a distinctive loop region that appears to form secondary structure, making it too rigid to accommodate the Cul3 interface (pmc.ncbi.nlm.nih.gov). In other words, unlike many KCTDs, KCTD14 may fail to bind Cul3 on its own, or bind only very weakly. This finding suggests that KCTD14’s biological role might diverge from the classic CRL3-adaptor paradigm, or that it might require partnership with another protein to engage Cul3.

Importantly, KCTD14’s demonstrated interaction with KCTD5 could provide a workaround to participate in ubiquitination pathways. KCTD5 is a confirmed Cullin-3 adaptor (part of a Cul3 E3 ligase complex) (pmc.ncbi.nlm.nih.gov). In fact, hetero-oligomerization can allow non-Cul3-binding KCTDs to indirectly associate with Cul3: for example, KCTD5 forming a complex with KCTD2 enabled the latter to bind Cul3 and target substrates (pmc.ncbi.nlm.nih.gov). By analogy, when KCTD14 binds to KCTD5, KCTD14 might be brought into Cullin-3 ligase complexes via KCTD5. This implies KCTD14 could function as a co-adaptor or substrate-specific subunit in a larger ubiquitin ligase assembly, even if it doesn’t directly touch the Cul3 protein. Currently, the specific substrate proteins (if any) that KCTD14 targets for ubiquitination remain unknown. Yet, emerging proteomic data provide clues to KCTD14’s cellular partners, which might be its substrates or binding targets:

  • ACSF3 (Acyl-CoA synthetase family member 3) – an enzyme involved in mitochondrial fatty acid metabolism – was identified as a high-confidence interactor of KCTD14 in a large-scale affinity purification study. In the BioPlex human interactome project (HEK293T cells), KCTD14 pulled down ACSF3 with a very high quantitative score (CompPASS ~0.99, well above significance threshold) (thebiogrid.org) (thebiogrid.org). This interaction was consistently observed across multiple dataset versions (BioPlex 1.0, 2.0, 3.0) (thebiogrid.org), suggesting a robust association. ACSF3 is a mitochondrial matrix enzyme; if KCTD14 binds ACSF3, it could hint at a role in regulating metabolic enzymes (for instance, by ubiquitination or localization).

  • TUBGCP6 (Tubulin gamma complex-associated protein 6) – a component of the γ-tubulin ring complex involved in microtubule nucleation at centrosomes – was also co-purified with KCTD14 in the BioPlex screen, with a similarly high interaction score (~0.98) (thebiogrid.org). This suggests KCTD14 might associate with centrosomal or cytoskeletal structures, possibly influencing cell cycle or mitotic spindle organization if the interaction is functional.

These partners are notable because they point toward disparate cellular processes (mitochondrial metabolism and microtubule organization). It is not yet confirmed whether KCTD14 directly regulates these proteins, but such protein–protein interaction data provide testable hypotheses. At minimum, they reinforce that KCTD14 is engaged in protein networks inside the cell rather than acting alone. In addition to these interactions, KCTD14 is presumed to partake in broader protein complexes by virtue of its oligomerization and possible co-adaptor behavior. Overall, while KCTD14’s primary molecular function has not been definitively demonstrated, the current understanding is that it likely serves as a scaffold or adaptor protein, potentially in ubiquitin-mediated proteostasis pathways or other multi-protein complexes. This is supported by the consensus that KCTD family members “use their C-termini to bind and recruit diverse cellular proteins destined for degradation” in partnership with Cullin3 complexes (pmc.ncbi.nlm.nih.gov) (a model that KCTD14 may partially follow, albeit in an atypical way).

Localization and Expression Profile

Knowing where a protein is expressed and localized can provide insight into its function. KCTD14 is an intracellular protein with a broad tissue distribution. It has no signal peptide or transmembrane segment, and experiments confirm it resides inside cells (not secreted) (www.proteinatlas.org). In immunohistochemistry/immunofluorescence analyses, KCTD14 protein shows cytosolic and nucleoplasmic localization (www.proteinatlas.org). Specifically, the Human Protein Atlas reports KCTD14 concentrated in the nucleoplasm (nuclear interior) and also in the cytosol and vesicle-like structures (www.proteinatlas.org). The vesicular staining could indicate presence on or near certain organelles or protein complexes (for example, it might associate with vesicular bodies or mitochondria, consistent with its interaction with a mitochondrial enzyme). The nucleoplasmic presence suggests KCTD14 might shuttle to the nucleus or interact with nuclear proteins, though its role there is undefined. It is not known to bind DNA directly (no DNA-binding domains), but it could influence nuclear processes indirectly via protein interactions.

At the tissue level, KCTD14 mRNA is expressed in many tissues without extreme specificity. RNA profiling (NCBI and GTEx data) shows broad expression: for instance, moderate levels in adrenal gland (RPKM ~10) and stomach (RPKM ~9.5), among at least 17 tissues examined (www.ncbi.nlm.nih.gov). The expression is “low tissue specificity”, meaning KCTD14 is fairly ubiquitously expressed rather than restricted to a particular organ or cell type (www.proteinatlas.org). Nonetheless, some enrichment has been noted in certain cell types: single-cell RNA data indicate higher expression in epithelial secretory cells (e.g. breast glandular cells, stomach foveolar cells, epididymal cells, alveolar type II lung cells) (www.proteinatlas.org). This clustering in secretory/glandular cell types could be a clue to function – perhaps KCTD14 is involved in protein processing or vesicle trafficking, as those cells have high secretory activity. In fact, KCTD14’s expression pattern groups with a cluster of genes related to “protein processing” in the Human Protein Atlas analysis (www.proteinatlas.org). It is not detected in blood plasma and shows no enrichment in immune cells (www.proteinatlas.org), aligning with it being a intracellular, ubiquitously expressed regulator rather than a secreted factor or cytokine.

In summary, the subcellular localization and expression data suggest KCTD14 operates in the general cellular machinery present in many cell types. Its presence in both the nucleus and cytosol indicates a potentially shuttling or multi-functional protein. Given these locations, KCTD14 could influence processes ranging from protein degradation (often cytosolic) to cell cycle or gene expression (nuclear) – consistent with the diverse identities of its candidate interacting partners (mitochondrial enzyme vs. centrosomal protein). However, pinpointing the exact cellular process requires more targeted studies.

Biological Significance and Current Research Directions

Because KCTD14 has only recently begun to attract research interest, its precise biological role is not fully established. Unlike some KCTD family members (e.g. KCTD13 implicated in neurodevelopmental disorders, KCTD7 in epilepsy, KCTD11 in cancer (pmc.ncbi.nlm.nih.gov)), KCTD14 has not yet been definitively linked to a specific disease or phenotype. There are no known inherited mutations in KCTD14 causing a human genetic syndrome, and KCTD14 knockout mouse phenotypes have not been reported in the literature as of 2023. This suggests that KCTD14’s functions might be somewhat redundant or subtle, or simply that it has been under-investigated. However, emerging data hints at some clinical correlations: cancer genomics studies have found that KCTD14 expression levels correlate with patient outcomes in certain cancers. According to the Human Protein Atlas analysis of tumor datasets, KCTD14 is a prognostic marker in at least four cancer types – including kidney renal clear cell carcinoma, pancreatic adenocarcinoma, skin melanoma, and thyroid carcinoma (www.proteinatlas.org). Specifically, differential expression of KCTD14 in these tumors is statistically associated with survival rates (though the direction of risk isn’t specified in the snippet). This association suggests that KCTD14 could play a role in tumor biology, perhaps through its putative function in protein degradation pathways or cell cycle regulation. It’s important to note that being a prognostic marker does not necessarily mean KCTD14 drives cancer progression; it might be part of a broader expression program in tumors. Nonetheless, such findings make KCTD14 a candidate for further research in oncology – understanding how its expression is regulated in cancers and whether it contributes to processes like cell proliferation or stress responses could be valuable.

From a research standpoint, expert opinions highlight the need to characterize proteins like KCTD14 to fill gaps in our understanding of cellular regulation. A 2019 review on the KCTD family pointed out that many KCTDs “remain relatively uncharacterized” and called for deeper investigation into their molecular mechanisms (pmc.ncbi.nlm.nih.gov). The same review and others have pointed out that diverse functions have been proposed for KCTDs, including roles in apoptosis, metabolism, and neural signaling (pmc.ncbi.nlm.nih.gov) (biosignaling.biomedcentral.com). It is thought that the adaptor/scaffold function of KCTDs could underlie these varied roles – by selecting specific protein targets for ubiquitination or by assembling signaling complexes, KCTDs can impact various pathways (pmc.ncbi.nlm.nih.gov). In the case of KCTD14, current hypotheses (drawing from the family context and preliminary data) include:

  • Proteostasis Regulation: KCTD14 may help target certain proteins (like the ACSF3 enzyme or other yet-unknown substrates) for ubiquitin-mediated degradation. This could affect metabolic enzyme turnover or the stability of proteins involved in cell structure (e.g. tubulin complex components). Supporting this, KCTD14’s close homolog KCTD7 has been linked to the ubiquitin–proteasome system in neurons (pubmed.ncbi.nlm.nih.gov), and loss of KCTD7 causes accumulation of proteins in a neurodegenerative context. It’s conceivable KCTD14 performs a similar function in other cell types.

  • Cell Cycle or Signaling Scaffold: If the interaction with TUBGCP6 is biologically relevant, KCTD14 might localize to centrosomes or mitotic structures and influence cell division. Alternatively, KCTD14 could have unidentified interactions with signaling proteins (e.g., kinases or receptors) given that some KCTDs modulate G-protein-coupled receptor signaling (notably KCTD12, -16 modulate GABA_B receptors ). No direct evidence yet ties KCTD14 to a specific signaling pathway, but ongoing interactome studies and phenotypic screens (such as CRISPR knockouts in cell lines) may soon illuminate its role. Notably, large-scale screens (DepMap) have not flagged KCTD14 as an essential gene for cell viability in cancer cell lines, but subtler phenotypes are possible.

  • Compensatory/Redundant Functions: It’s also possible KCTD14 has overlapping function with another KCTD. Given its ability to bind KCTD5, one theory is that KCTD14 could modulate the activity of the Cul3–KCTD5 ubiquitin ligase complex. For example, a KCTD14 subunit in a KCTD5 pentamer might alter which substrate is ubiquitinated or the timing of ubiquitin transfer. Such regulatory crosstalk between KCTD family members is an emerging theme – a recent study showed KCTD12 and KCTD16 form hetero-oligomers that fine-tune GABA_B receptor signaling kinetics (pmc.ncbi.nlm.nih.gov). Similarly, KCTD5’s interplay with other KCTDs influenced their ability to recruit Cul3 (pmc.ncbi.nlm.nih.gov). Investigating whether KCTD14 alters KCTD5’s function (or vice versa) is a current research question.

In latest research (2022–2024), the focus has been on understanding structure and interactions:
- The AlphaFold-based structural analyses (2021–2022) of the entire KCTD family provided a framework for KCTD14’s pentameric structure and highlighted its unusual BTB loop, raising the question about Cul3 binding (www.mdpi.com) (pmc.ncbi.nlm.nih.gov). These computational studies by Esposito et al. and by Balasco et al. (Int. J. Mol. Sci. 2022; Biomolecules 2021) are guiding experimentalists to which aspects of KCTD14’s structure to validate.
- The protein–protein interaction studies (2023), such as Liao et al. (Int. J. Mol. Sci. 2023), systematically probing KCTD5 interactions, have for the first time shown KCTD14 in complex with another family member (pmc.ncbi.nlm.nih.gov). This provides concrete evidence that KCTD14 does not function in isolation and can integrate into known pathways (Cul3 ubiquitination via KCTD5).
- Ongoing high-throughput proteomics (BioPlex 3.0 released in 2021 (thebiogrid.org)) has expanded the list of KCTD14’s candidate partners, which researchers can now follow up individually to test if, for example, KCTD14 regulates the stability or activity of ACSF3 or TUBGCP6 in cells.

In conclusion, KCTD14 is a scaffold-like protein whose known attributes (BTB domain oligomerization, broad expression, intracellular localization) align with a role in orchestrating protein complexes, possibly in ubiquitin-mediated protein turnover. Current evidence points to it forming pentamers and interacting with key cellular proteins, though it may be unique among KCTDs in how it engages the Cul3 ubiquitin ligase pathway. As a relatively uncharted gene, KCTD14’s function is being pieced together from bioinformatic predictions and initial protein-interaction maps. The next steps in research will likely involve targeted experiments: e.g. creating KCTD14-knockout cell lines or animals to see what physiological processes are affected, and biochemical assays to confirm if it directs ubiquitination of specific substrates. Given its emerging links to cancer prognosis and potential partnerships in critical cellular machinery (metabolism and microtubule organization), KCTD14 represents a fascinating example of a “dark” gene now coming to light. Continued investigation, supported by the recent structural and interactome data, should clarify the biological processes governed by KCTD14 and whether it can be leveraged in biomedical contexts (for instance, as a biomarker or a therapeutic target in pathways it regulates). The current understanding, while limited, establishes KCTD14 as an intracellular adaptor protein with a probable role in maintaining protein homeostasis and cellular signaling integrity, operating at the intersection of the ubiquitin-proteasome system and other cellular networks.

References: Recent authoritative sources and data supporting this summary include structural biology analyses of KCTD oligomers (www.mdpi.com) (pmc.ncbi.nlm.nih.gov), reviews on KCTD family functions (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov), interaction studies (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov), expression/localization databases (www.proteinatlas.org) (www.ncbi.nlm.nih.gov), and bioinformatic protein network findings (thebiogrid.org) (thebiogrid.org) (referenced in-line above). These up-to-date sources (2019–2023) provide the foundation for the current model of KCTD14 function and will serve as a guide for future experimental exploration.

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  38. AnnotationURLCitation(end_index=17494, start_index=17352, title='KCTD: A new gene family involved in neurodevelopmental and neuropsychiatric disorders - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC6566181/#:~:text=into%20mechanisms%20of%20the%20poorly,Recent%20biochemical')
  39. AnnotationURLCitation(end_index=18469, start_index=18299, title='KCTD14 protein expression summary - The Human Protein Atlas', type='url_citation', url='https://www.proteinatlas.org/ENSG00000151364-KCTD14#:~:text=expression%20cluster%5E%7Bi%7D%20Not%20detected%20,i%7D%20Low%20cancer%20specificity')
  40. AnnotationURLCitation(end_index=19718, start_index=19566, title='KCTD5 Forms Hetero-Oligomeric Complexes with Various Members of the KCTD Protein Family - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10531988/#:~:text=two%20dozen%20proteins%20,roles%20that%20underly%20disease%20states')
  41. AnnotationURLCitation(end_index=20018, start_index=19882, title='KCTD: A new gene family involved in neurodevelopmental and neuropsychiatric disorders - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC6566181/#:~:text=underlie%20the%20diverse%20biological%20processes,30')
  42. AnnotationURLCitation(end_index=20213, start_index=20019, title='The emerging role of the KCTD proteins in cancer | Cell Communication and Signaling | Full Text', type='url_citation', url='https://biosignaling.biomedcentral.com/articles/10.1186/s12964-021-00737-8#:~:text=So%20far%2C%20KCTD%20genes%20have,cancer%20appears%20far%20from%20completed')
  43. AnnotationURLCitation(end_index=20624, start_index=20442, title='KCTD: A new gene family involved in neurodevelopmental and neuropsychiatric disorders - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC6566181/#:~:text=molecules%20that%20use%20their%20C%E2%80%90termini,reported%20for%20KCTD%20proteins%2C%20including')
  44. AnnotationURLCitation(end_index=21309, start_index=21140, title='A homozygous mutation in KCTD7 links neuronal ceroid lipofuscinosis to the ubiquitin-proteasome system - PubMed', type='url_citation', url='https://pubmed.ncbi.nlm.nih.gov/22748208/#:~:text=A%20homozygous%20mutation%20in%20KCTD7,identified%20variant%20altered%20the%20localization')
  45. AnnotationURLCitation(end_index=22966, start_index=22802, title='KCTD5 Forms Hetero-Oligomeric Complexes with Various Members of the KCTD Protein Family - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10531988/#:~:text=association%20with%20a%20GIRK%20channel%2C,the%20ability%20to%20interact%20with')
  46. AnnotationURLCitation(end_index=23219, start_index=23055, title='KCTD5 Forms Hetero-Oligomeric Complexes with Various Members of the KCTD Protein Family - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10531988/#:~:text=%28Cul3%29%20ubiquitin%20ligase%20adapter%20,a%20major%20role%20in%20regulating')
  47. AnnotationURLCitation(end_index=23789, start_index=23640, title='Alphafold Predictions Provide Insights into the Structural Features of the Functional Oligomers of All Members of the KCTD Family', type='url_citation', url='https://www.mdpi.com/1422-0067/23/21/13346#:~:text=members%20of%20the%20KCTD%20protein,although%20pentameric%2C%20appears%20to%20be')
  48. AnnotationURLCitation(end_index=23965, start_index=23790, title='A Comprehensive Analysis of the Structural Recognition between KCTD Proteins and Cullin 3 - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10856315/#:~:text=while%20a%20meaningless%20complex%20is,BTB%7D%E2%80%93Cul3%20partnership%20%28Figure%20S10')
  49. AnnotationURLCitation(end_index=24554, start_index=24388, title='KCTD5 Forms Hetero-Oligomeric Complexes with Various Members of the KCTD Protein Family - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10531988/#:~:text=exhibit%20differential%20affinity%20for%20KCTD5,KCTD10%20and%20KCTD13%20similarly')
  50. AnnotationURLCitation(end_index=24879, start_index=24774, title='KCTD14 - TUBGCP6 Interaction Summary | BioGRID', type='url_citation', url='https://thebiogrid.org/interaction/1175988#:~:text=,should%20be%20compared%20directly')
  51. AnnotationURLCitation(end_index=26994, start_index=26845, title='Alphafold Predictions Provide Insights into the Structural Features of the Functional Oligomers of All Members of the KCTD Family', type='url_citation', url='https://www.mdpi.com/1422-0067/23/21/13346#:~:text=members%20of%20the%20KCTD%20protein,although%20pentameric%2C%20appears%20to%20be')
  52. AnnotationURLCitation(end_index=27170, start_index=26995, title='A Comprehensive Analysis of the Structural Recognition between KCTD Proteins and Cullin 3 - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10856315/#:~:text=while%20a%20meaningless%20complex%20is,BTB%7D%E2%80%93Cul3%20partnership%20%28Figure%20S10')
  53. AnnotationURLCitation(end_index=27368, start_index=27205, title='KCTD: A new gene family involved in neurodevelopmental and neuropsychiatric disorders - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC6566181/#:~:text=An%20unusual%20feature%20of%20this,the%20delicate%20balance%20between%20protein')
  54. AnnotationURLCitation(end_index=27532, start_index=27369, title='A Comprehensive Analysis of the Structural Recognition between KCTD Proteins and Cullin 3 - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10856315/#:~:text=functionalities%20of%20these%20proteins,BTB%20domain%2C%20thus%20helping%20the')
  55. AnnotationURLCitation(end_index=27720, start_index=27554, title='KCTD5 Forms Hetero-Oligomeric Complexes with Various Members of the KCTD Protein Family - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10531988/#:~:text=exhibit%20differential%20affinity%20for%20KCTD5,KCTD10%20and%20KCTD13%20similarly')
  56. AnnotationURLCitation(end_index=27853, start_index=27721, title='KCTD5 Forms Hetero-Oligomeric Complexes with Various Members of the KCTD Protein Family - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10531988/#:~:text=GABA_%7BB%7D,a%20major%20role%20in%20regulating')
  57. AnnotationURLCitation(end_index=28059, start_index=27889, title='KCTD14 protein expression summary - The Human Protein Atlas', type='url_citation', url='https://www.proteinatlas.org/ENSG00000151364-KCTD14#:~:text=PROTEIN%20EXPRESSION%20AND%20LOCALIZATION%20Tissue,i%7D%20Low%20tissue%20specificity')
  58. AnnotationURLCitation(end_index=28193, start_index=28060, title='KCTD14 potassium channel tetramerization domain containing 14 [Homo sapiens (human)] - Gene - NCBI', type='url_citation', url='https://www.ncbi.nlm.nih.gov/gene/65987#:~:text=Predicted%20to%20be%20involved%20in,Orthologs%20%2012%20all')
  59. AnnotationURLCitation(end_index=28309, start_index=28238, title='KCTD14 - ACSF3 Interaction Summary | BioGRID', type='url_citation', url='https://thebiogrid.org/interaction/1175987#:~:text=')
  60. AnnotationURLCitation(end_index=28415, start_index=28310, title='KCTD14 - TUBGCP6 Interaction Summary | BioGRID', type='url_citation', url='https://thebiogrid.org/interaction/1175988#:~:text=,should%20be%20compared%20directly')

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KCTD14 Core Function Hypothesis: Identical Protein Binding (GO:0042802) OpenScientist openscientist-autonomous 17 citations 2 artifacts 2026-07-04T16:55:38.393344 citations file
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KCTD14 Core Function Hypothesis: Identical Protein Binding (GO:0042802)

Executive Judgment

Verdict: Partially supported — valid annotation lead but should not be designated as core function

The hypothesis that identical protein binding (GO:0042802) is a core function of KCTD14 is partially supported as a factual description of what KCTD14 likely does, but weakly supported as a core function designation. Two lines of evidence confirm KCTD14 self-association: (1) yeast two-hybrid self-interaction data from the proteome-scale HI-II-14 interactome (PMID: 25416956), and (2) AlphaFold multimer predictions yielding reliable pentameric models with a distinctive circle-like CTD organization (PMID: 36362127). Family-wide structural studies using electron microscopy and X-ray crystallography corroborate that BTB-mediated pentamerization is the norm across the KCTD family (PMID: 27152988; PMID: 26334369).

However, the critical curation issue is whether self-binding constitutes a "core function" or merely a structural prerequisite that enables core function. For every experimentally characterized KCTD family member, oligomerization is the assembly step that enables the protein's primary molecular activity — serving as a Cullin3 E3 ubiquitin ligase adaptor, modulating Gβγ signaling, or scaffolding receptor complexes. Treating the scaffold assembly as the core function is analogous to designating "protein folding" as the core function of a kinase. GO:0042802 is a valid annotation lead with IPI evidence, but it should be treated as non-core; KCTD14's primary molecular function beyond oligomerization remains experimentally undetermined.

Two additional caveats sharpen this assessment. First, GO:0042802 is not currently annotated for KCTD14 in QuickGO — only GO:0051260 (protein homooligomerization, IEA) and GO:0005515 (protein binding, IPI) exist — so the hypothesis proposes both a new annotation and its elevation to core status simultaneously. Second, the Y2H evidence comes from a single high-throughput study with moderate confidence (MI-score 0.37, 3/4 replicas), without independent biochemical validation of the interaction or its stoichiometry.

Summary

KCTD14 (UniProt: Q9BQ13) is a member of the 25-member potassium channel tetramerization domain (KCTD) protein family in humans. Like most family members, it contains an N-terminal BTB (bric-à-brac, tramtrack, broad complex) domain that mediates oligomerization, and a C-terminal domain (CTD) of less-well-characterized function. The seed hypothesis proposes that identical protein binding (GO:0042802) — the capacity to bind copies of itself — represents a core molecular function of KCTD14, based on its predicted pentameric assembly via the BTB domain.

Our investigation confirmed the self-interaction through direct evidence (Y2H) and computational prediction (AlphaFold pentameric modeling), supplemented by extensive family-wide structural data showing pentamerization as the default state for KCTD BTB domains. However, for every characterized KCTD family member, BTB-mediated oligomerization enables downstream molecular activities: Cullin3 E3 ubiquitin ligase adaptor function (KCTD5, KCTD6, KCTD9, KCTD11, KCTD17), Gβγ modulation (KCTD2, KCTD5, KCTD12, KCTD16), GABAB receptor regulation (KCTD8, KCTD12, KCTD16), or developmental pathway control (KCTD1, KCTD11). For KCTD14 specifically, none of these downstream functions have been experimentally confirmed, and the protein remains one of the least-characterized members of the family.

The most informative action for curators is to consider adding GO:0042802 as a non-core MF annotation with IPI evidence from PMID:25416956, while explicitly noting that the core molecular function remains undetermined. Candidate core functions to monitor include Cullin3 adaptor activity (by closest-paralog KCTD7 analogy), Gβγ subunit modulation (by family-wide screen data), and a potential immunomodulatory role via the TNF-TNFR1 axis (recently proposed computationally for pancreatic cancer).

Key Findings

Finding 1: KCTD14 Self-Interaction Detected by Yeast Two-Hybrid

The most direct experimental evidence for KCTD14 identical protein binding comes from the HI-II-14 proteome-scale human binary interactome map (PMID: 25416956). Rolland et al. (2014) systematically mapped approximately 14,000 high-quality human binary protein-protein interactions using a yeast two-hybrid (Y2H) array approach. Their study, described as providing "reference maps of interactome networks [that] will be critical to fully understand genotype-phenotype relationships," detected KCTD14 (Q9BQ13) self-interaction in 3 out of 4 replicas (IntAct accession: EBI-10487331, MI-score: 0.37, MI method: MI:0397 — two-hybrid array).

This Y2H self-interaction constitutes the experimental basis for any potential GO:0042802 annotation. The evidence is genuine but has important limitations: Y2H operates in yeast, not in human cells; it detects binary interactions between fusion proteins that may not reflect full-length protein behavior or native oligomeric context; and the MI-score of 0.37 is moderate, consistent with high-throughput detection rather than focused biochemical validation. Notably, the self-interaction data exists in IntAct but has been annotated to the broader GO:0005515 (protein binding) rather than the more specific GO:0042802 (identical protein binding), suggesting GO curators have not yet propagated this evidence to the more specific term.

Finding 2: AlphaFold Predicts KCTD14 Pentameric Assembly with Distinctive CTD Organization

Esposito et al. (2022) applied AlphaFold multimer predictions to model oligomeric states of all KCTD family members (PMID: 36362127). Their approach "led to the identification of reliable three-dimensional models for the pentameric states of KCNRG, KCTD6, KCTD4, KCTD7, KCTD9, and KCTD14 and possibly for KCTD11 and KCTD21 that are involved in key biological processes and that were previously uncharacterized from a structural point of view." Critically, the study revealed a distinctive structural signature for the KCTD7/14 subclade: "the structure of the related proteins KCTD7 and KCTD14, although pentameric, appears to be characterized by a different organization of the CTD region, with the five chains forming a circle-like structure with a large cavity." This contrasts with the propeller-like CTD arrangement seen in other KCTD family members.

The AlphaFold monomer model for KCTD14 (AF-Q9BQ13-F1) has a mean pLDDT of 85.88, indicating high overall confidence. The pentameric prediction provides specific structural context for the self-interaction — predicting not just that KCTD14 self-associates but that it does so as a specific pentameric ring with an unusual CTD architecture. However, these remain computational predictions; no crystal structure, cryo-EM structure, or solution biophysics data exist for KCTD14 itself.

The structural basis for KCTD self-interaction is robustly established at the family level through converging experimental approaches:

  • Electron microscopy: Smaldone et al. (2016) examined BTB domains from 7 KCTD members spanning 5 major phylogenetic clades and found that their "present electron microscopy data highlight the occurrence of well-defined pentameric states for all domains" (PMID: 27152988).

  • X-ray crystallography: Ji et al. (2016) reported pentameric crystal structures of the KCTD1 and KCTD9 BTB domains and demonstrated that Cul3 binding affinity varies — "KCTD proteins 5, 6, 9 and 17 bind to Cul3 with high affinity, while the KCTD proteins 1 and 16 do not have detectable binding" (PMID: 26334369). Pinkas et al. (2017) added crystal structures for additional members, noting that "Members of the potassium channel tetramerization domain (KCTD) family are soluble non-channel proteins that commonly function as Cullin3 (Cul3)-dependent E3 ligases" (PMID: 28963344).

  • Molecular dynamics simulations: Balasco et al. (2019) demonstrated that "KCTD-BTB domains are stable in the simulation timescales, even in their monomeric forms" and that open pentameric states relate to functional roles (PMID: 31370201).

One important exception is KCTD11, which forms tetramers rather than pentamers (PMID: 21237243), demonstrating that the oligomeric state is not invariant across the family and cannot be automatically assumed for unstudied members.

Finding 4: GO:0042802 Is Not Currently Annotated for KCTD14 in QuickGO

Examination of the current GO annotation status for Q9BQ13 revealed that GO:0042802 (identical protein binding) is not currently assigned. The existing annotations are:

GO Term GO ID Evidence Code Source
protein homooligomerization GO:0051260 IEA InterPro IPR003131
protein binding GO:0005515 IPI IntAct (PMIDs: 25416956, 28514442, 29892012, 33961781)

The IPI-supported GO:0005515 annotation encompasses interactions with STK16, TCF4, and ACSF3 in addition to the self-interaction. The Y2H self-interaction data from PMID:25416956 exists in IntAct but has not been propagated to GO:0042802. This means the seed hypothesis proposes both a new annotation and its elevation to core status — a step requiring stronger justification than is currently available.

Evidence Matrix

# Citation Evidence Type Direction Claim Tested Key Finding Context Confidence & Limitations
1 PMID: 25416956 (Rolland et al. 2014) Direct assay (Y2H) Supports KCTD14 binds itself Self-interaction detected in 3/4 replicas; MI-score 0.37 Human proteins in yeast Y2H; HI-II-14 systematic screen Moderate. Single method, HT screen, no biochemical validation
2 PMID: 36362127 (Esposito et al. 2022) Computational (AlphaFold) Supports KCTD14 forms pentamers Reliable pentameric model with distinctive circle-like CTD In silico (AlphaFold2-multimer) Moderate. Prediction, not experimental; validated for other KCTDs
3 PMID: 27152988 (Smaldone et al. 2016) Structural/evolutionary (EM) Supports (by analogy) KCTD BTB domains pentamerize Pentameric states for all 7 tested BTB domains across 5 clades In vitro EM, recombinant BTB domains High for family; KCTD14 not directly tested
4 PMID: 26334369 (Ji et al. 2016) Structural (X-ray, cryo-EM) Supports (by analogy) KCTD proteins form pentameric rings Crystal structures of KCTD1 and KCTD9 BTB pentamers; Cul3 binding varies In vitro High for family; demonstrates Cul3-binding variability
5 PMID: 28963344 (Pinkas et al. 2017) Structural (X-ray) Supports (by analogy) KCTDs are pentameric Cul3 adaptors Crystal structures confirm pentameric assemblies; KCTDs commonly function as Cul3 E3 ligases In vitro High for family; inferential for KCTD14
6 PMID: 31370201 (Balasco et al. 2019) Computational (MD) Supports (by analogy) BTB domain stability in oligomeric states MD simulations show stability in various oligomeric states including pentamers In silico Moderate. KCTD14 not specifically modeled
7 PMID: 36736897 (Barthet/Sloan et al. 2023) Direct assay (co-IP, BRET) Qualifies KCTDs interact with Gβγ Nearly all 25 KCTDs interact with Gβγ; functional consequence on cAMP signaling HEK293 cells; family-wide screen Moderate. Suggests alternative core function beyond self-binding
8 PMID: 37762619 (Bhatt/Liao et al. 2023) Direct assay (co-IP, BRET) Qualifies KCTDs form hetero-oligomers KCTD5 forms hetero-oligomeric complexes with various family members HEK293 cells Moderate. Complicates "identical protein binding" as sole interaction mode
9 PMID: 22748208 (Staropoli et al. 2012) Direct assay (paralog KCTD7) Qualifies KCTD7-Cullin3 interaction KCTD7 R184C mutation abrogated Cullin3 interaction Human KCTD7 in cell-based assays High for KCTD7. Suggests Cul3 adaptor is the core function for the clade
10 PMID: 30295347 (Metz et al. 2018) Direct assay (paralog KCTD7) Qualifies KCTD7 disease mechanism KCTD7 mutations impair Cul3 binding and autophagy Patient fibroblasts, yeast High for KCTD7. Core function is Cul3-dependent, not just self-binding
11 PMID: 41080575 (Liang et al. 2025) Computational/functional Competing KCTD14 immunomodulatory function KCTD14 implicated as immunomodulatory oncogene via TNF-TNFR1 axis in PC Computational + scRNA-seq Low. Indirect, computational, requires experimental validation
12 PMID: 21237243 (Dementieva et al. 2011) Structural (biophysical) Qualifies All KCTDs pentamerize KCTD11 forms tetramers, not pentamers In vitro (gel filtration, light scattering) High. Demonstrates that pentamerization is not universal in the family
13 QuickGO/UniProt (database) Database/computational Qualifies Current annotation status GO:0042802 not annotated despite Y2H evidence in IntAct Database records 2026-07 High. Confirms this is a proposed new annotation, not an existing one

GO Curation Implications

Current Annotation Status

KCTD14 (Q9BQ13) has a minimal GO annotation profile:

  • GO:0051260 (protein homooligomerization, BP) — IEA from InterPro IPR003131. Appropriately assigned based on the BTB domain, which is the canonical oligomerization motif for this family.
  • GO:0005515 (protein binding, MF) — IPI from IntAct, supported by multiple PMIDs. This covers both the self-interaction and heteromeric interactions with STK16, TCF4, and ACSF3.
  • GO:0042802 (identical protein binding, MF) — Not currently annotated, despite the Y2H self-interaction evidence existing in IntAct.

Assessment of GO:0042802 as Core Function

The proposed annotation GO:0042802 is technically justifiable as an MF annotation but should NOT be treated as a core function. The reasoning is threefold:

  1. As a GO MF annotation: GO:0042802 could be validly assigned based on the Y2H self-interaction from PMID: 25416956, using IPI evidence code. This would represent a more specific annotation than the currently assigned GO:0005515 and would accurately capture the observed self-interaction. This is a legitimate annotation lead.

  2. As a core function: Identical protein binding is a prerequisite activity shared across virtually all KCTD family members. It enables the protein's actual downstream function but is not itself the endpoint activity. For characterized family members, the core molecular function is typically Cullin3 E3 ubiquitin ligase adaptor activity, Gβγ binding and GPCR signal modulation, or receptor scaffolding. Designating self-binding as the core function for KCTD14 is premature and mechanistically superficial.

  3. Comparison with paralogs: For KCTD7 (the closest paralog), disease-causing mutations disrupt Cullin3 binding and autophagy-lysosome function — not oligomerization per se (PMID: 30295347; PMID: 22748208). This strongly suggests that the core function of the KCTD7/14 subclade lies downstream of self-assembly.

  • Retain GO:0051260 (protein homooligomerization, BP) — well-supported by domain architecture and family-wide evidence
  • Consider adding GO:0042802 (identical protein binding, MF) with IPI evidence from PMID: 25416956 — but flag as non-core
  • Do not designate GO:0042802 as core MF — the true core molecular function is undetermined
  • Monitor Cullin3 adaptor activity, Gβγ modulation, and TNF-TNFR1 axis involvement as candidate core functions pending experimental data

Mechanistic Scope

Direct Gene-Product Activity

The immediate molecular activity under evaluation is self-binding — the ability of KCTD14 monomers to associate into homo-oligomeric (likely pentameric) complexes via the BTB domain. This is a well-supported structural property, but it is mechanistically upstream of the protein's biological role. The assembly hierarchy can be represented as:

KCTD14 monomer
    ↓ BTB domain-mediated self-association
Pentameric BTB ring (predicted)
    ↓ CTD region forms circle-like structure with large cavity
Full-length pentameric assembly
    ↓ [UNKNOWN — no experimental data for KCTD14]
    ├── Cullin3 binding? → E3 ubiquitin ligase complex → substrate ubiquitination
    ├── Gβγ binding? → GPCR signal modulation → cAMP pathway effects
    ├── TNF-TNFR1 axis? → immunomodulation (computational evidence only)
    └── Novel function? → unknown biological process

What Self-Binding Enables — Family Analogies

For characterized KCTD family members, the pentameric BTB ring serves as a platform for three main classes of molecular activity:

KCTD Member(s) Downstream Function Core MF Evidence Level
KCTD5, KCTD6, KCTD9, KCTD11, KCTD17 Cullin3 E3 ubiquitin ligase adaptor Ubiquitin ligase complex component Crystal structures, biochemistry
KCTD2, KCTD5, KCTD12, KCTD16 Gβγ binding → GPCR modulation G protein modulator Co-IP, BRET, functional assays
KCTD8, KCTD12, KCTD12b, KCTD16 GABAB receptor regulation Receptor auxiliary subunit Co-IP, electrophysiology
KCTD7 (closest paralog) Cul3-dependent autophagy-lysosome regulation Cul3 adaptor Genetics, cell biology
KCTD14 Unknown Unknown —

Separation of Direct Activity from Downstream Phenotypes

KCTD14 has been identified in several transcriptomic and computational disease studies, but these represent expression-level associations that do not inform molecular function:

  • Dengue infection: KCTD14 upregulated in dengue patients regardless of severity (PMID: 39397194; PMID: 35220956) — transcriptomic correlation, not MF evidence
  • Pancreatic cancer: KCTD14 identified as potential immunomodulatory oncogene via TNF-TNFR1 axis (PMID: 41080575) — computational/scRNA-seq inference, not validated
  • Ovarian cancer: KCTD14 included in DNA methylation-related prognostic signature (PMID: 36978087) — statistical association only
  • Diabetes: KCTD14 transcript altered in diabetic rat colon (PMID: 34806320) — rat model, low fold-change

None of these disease-context findings should influence GO MF annotation for KCTD14.

Conflicts and Alternatives

1. Hetero-Oligomerization Complicates "Identical Protein Binding"

Bhatt et al. (2023) demonstrated that KCTD5 forms hetero-oligomeric complexes with various KCTD family members, with "different regions on KCTD5 responsible for uniquely contributing to interactions with other KCTD proteins" (PMID: 37762619). The authors concluded that "KCTD hetero-oligomeric interactions may occur throughout the KCTD family." If KCTD14 preferentially forms hetero-oligomers in vivo (e.g., with KCTD7 or other family members), then GO:0042802 (identical protein binding) would be an incomplete or misleading annotation. The Y2H self-interaction assay cannot distinguish between a protein that exclusively forms homo-oligomers and one that can also form hetero-oligomers.

2. Cullin3 Adaptor Activity as the True Core Function

The closest paralog, KCTD7, has well-established Cullin3 interaction: Staropoli et al. (2012) showed that the R184C mutation "abrogated interaction with cullin-3, a ubiquitin-ligase component and known KCTD7 interactor" (PMID: 22748208), and Metz et al. (2018) demonstrated that KCTD7 mutations impair autophagy through Cul3-dependent pathways (PMID: 30295347). If KCTD14 similarly functions as a Cul3 adaptor, then its core MF would be related to ubiquitin ligase activity, not self-binding.

However, not all KCTDs bind Cul3. Ji et al. (2016) found that "KCTD proteins 1 and 16 do not have detectable binding" to Cul3 despite having functional BTB domains (PMID: 26334369). Whether KCTD14 falls in the Cul3-binding or non-binding subgroup has not been tested.

3. Gβγ Modulation as an Alternative Core Function

The family-wide screen by Sloan/Barthet et al. (2023) demonstrated that "nearly all the 25 KCTD proteins interact with Gβγ" with functional consequences for adenylyl cyclase-cAMP signaling (PMID: 36736897). KCTD14 was included in this screen. If Gβγ binding proves to be KCTD14's primary signaling role, the core MF would shift toward G-protein modulation rather than self-binding.

4. Paralog Confusion Risk with KCTD7

KCTD14 and KCTD7 form a distinct subclade with shared structural features (circle-like CTD, large cavity) (PMID: 36362127). KCTD7 is well-characterized as a disease gene (progressive myoclonic epilepsy EPM3/CLN14) with Cul3 interaction and autophagy-lysosome involvement. There is a risk of inappropriately transferring KCTD7 annotations to KCTD14 without direct experimental evidence. KCTD14 may have distinct substrates, tissue expression, and biological roles despite sharing structural organization with KCTD7.

5. Oligomeric State Exceptions

KCTD11 forms tetramers rather than pentamers (PMID: 21237243), showing that the oligomeric state cannot be automatically assumed for untested members. While the AlphaFold prediction for KCTD14 specifically indicates a pentameric state, this has not been experimentally validated.

Knowledge Gaps

Gap What Was Checked Why It Matters Resolving Evidence
No direct biochemical characterization of KCTD14 PubMed literature, UniProt, IntAct Cannot confirm oligomeric state, binding affinity, or stoichiometry Recombinant expression + SEC-MALS, analytical ultracentrifugation, or native MS
No experimental structure PDB search (no entries); AlphaFold DB (monomer model, pLDDT 85.88) Pentameric prediction is computational only; circle-like CTD cavity is unverified X-ray crystallography or cryo-EM of KCTD14 BTB domain and/or full-length protein
Cullin3 binding status unknown Literature on KCTD-Cul3 interactions; KCTD14 not tested in any study Determines whether E3 ligase adaptor is a candidate core function Co-IP or ITC of KCTD14 with Cul3 N-terminal domain
Gβγ binding specifics unknown Family-wide screen (PMID: 36736897) included KCTD14 but individual data not reported in detail If confirmed, would suggest GPCR modulation as core function Focused BRET/co-IP with domain deletions
Substrate identity unknown No data available If KCTD14 is a Cul3 adaptor, the substrate defines its specific biological role Proximity labeling (BioID/TurboID) or ubiquitin remnant profiling
In vivo oligomeric state unknown Y2H detects binary interactions only Actual stoichiometry in human cells may differ from predictions BRET titration, cross-linking MS, or fluorescence fluctuation spectroscopy
Hetero-oligomerization partners unknown KCTD5 hetero-oligomers studied (PMID: 37762619); KCTD14 not specifically tested If KCTD14 preferentially hetero-oligomerizes, GO:0042802 may be secondary Co-IP screen with all KCTD family members
Tissue/cell expression context Disease transcriptomics mention KCTD14 in dengue, cancer, diabetes Expression pattern constrains which functions are physiologically relevant GTEx/HPA queries, single-cell atlas data

Discriminating Tests

Priority 1: Confirm Self-Interaction and Determine Stoichiometry

  • Recombinant KCTD14 BTB domain expression followed by size-exclusion chromatography coupled with multi-angle light scattering (SEC-MALS) to determine native oligomeric state
  • Analytical ultracentrifugation (AUC) to confirm or refute the pentameric stoichiometry predicted by AlphaFold
  • Co-immunoprecipitation with differentially epitope-tagged constructs in human cells (e.g., FLAG-KCTD14 + HA-KCTD14) to validate Y2H self-interaction in a mammalian context

Priority 2: Test Cullin3 Adaptor Activity

  • Co-immunoprecipitation or pull-down of KCTD14 with the Cul3 N-terminal domain, following the approach used for KCTD5, KCTD9, and KCTD7
  • Isothermal titration calorimetry (ITC) to measure binding affinity, as performed for KCTD5-Cul3 (Kd = 59 nM; PMID: 24747150)
  • If Cul3 binding confirmed: in vitro ubiquitination assay with candidate substrates

Priority 3: Characterize Gβγ Interaction

  • Focused BRET assay with KCTD14 and Gβγ subunits, including agonist-dependence testing
  • Domain deletion mapping to identify whether the BTB, CTD, or both regions mediate Gβγ binding
  • Functional readout: adenylyl cyclase 5 sensitization assay to test whether KCTD14 blunts Gβγ-mediated cAMP signaling, as shown for other KCTDs (PMID: 36736897)

Priority 4: Structural Determination

  • Cryo-EM of full-length KCTD14 pentamer to verify the distinctive circle-like CTD cavity predicted by AlphaFold
  • X-ray crystallography of the BTB domain to compare with other family members
  • These would definitively resolve the oligomeric state and provide a structural basis for understanding specificity

Priority 5: Identify Biological Context and Substrates

  • BioID/TurboID proximity labeling with KCTD14 as bait in relevant cell types to identify the in vivo interactome
  • CRISPR knockout followed by transcriptomic and proteomic profiling to identify downstream effects
  • Tissue expression profiling using GTEx, Human Protein Atlas, and single-cell atlas data to identify primary sites of function

Curation Leads

All items below are leads requiring curator verification.

Lead 1: Add GO:0042802 as Non-Core MF Annotation

  • Action: Consider annotating GO:0042802 (identical protein binding) for Q9BQ13 with IPI evidence code
  • Reference: PMID: 25416956 (Rolland et al. 2014)
  • Snippet to verify: "Just as reference genome sequences revolutionized human genetics, reference maps of interactome networks will be critical to fully understand genotype-phenotype relationships. Here, we describe a systematic map of ~14,000 high-quality human binary protein-protein interactions."
  • IntAct accession: EBI-10487331 (KCTD14 self-interaction, Q9BQ13-Q9BQ13)
  • Caveat: Y2H detects binary interactions; does not confirm oligomeric stoichiometry. Should be flagged as non-core function.

Lead 2: Retain GO:0051260 but Consider Evidence Upgrade

  • Action: Retain GO:0051260 (protein homooligomerization) and consider whether AlphaFold pentamer predictions warrant ISS or IC evidence upgrade from IEA
  • Reference: PMID: 36362127 (Esposito et al. 2022)
  • Snippet to verify: "our approach led to the identification of reliable three-dimensional models for the pentameric states of KCNRG, KCTD6, KCTD4, KCTD7, KCTD9, and KCTD14 and possibly for KCTD11 and KCTD21 that are involved in key biological processes and that were previously uncharacterized from a structural point of view"
  • Question for curator: Does the combination of Y2H self-interaction + AlphaFold pentamer prediction + family-wide EM data warrant upgrading from IEA to a manually assigned evidence code?

Lead 3: Do Not Designate Self-Binding as Core Function

  • Rationale: For every experimentally characterized KCTD family member, BTB-mediated oligomerization enables the protein's downstream molecular activity — it is the assembly step, not the functional output. The KCTD7/14 subclade data specifically suggest Cullin3 adaptor activity as the likely core function. Until KCTD14's primary molecular activity is determined, the core MF slot should remain open.
  • Suggested action: Annotate GO:0042802 but note it as a structural/assembly property rather than core function. Add a curator note that the primary molecular function beyond oligomerization is experimentally undetermined.

Lead 4: Monitor Emerging Functional Evidence

  • Gβγ binding: PMID: 36736897 — "we report that nearly all the 25 KCTD proteins interact with Gβγ" — family-wide screen suggesting alternative core function
  • TNF-TNFR1 axis: PMID: 41080575 — "highlights KCTD14 as a novel immunomodulatory oncogene acting through the TNF-TNFR1 axis" — computational evidence in pancreatic cancer
  • Autophagy/lysosome connection: If KCTD14 shares functional parallels with KCTD7 (PMID: 30295347), autophagy-related GO terms may become relevant

Lead 5: Candidate GO Terms for Future Consideration

If downstream function is experimentally established, consider:

Candidate GO Term GO ID Ontology Condition
Cul3-RING ubiquitin ligase complex GO:0031463 CC If Cul3 binding confirmed
ubiquitin protein ligase binding GO:0031625 MF If Cul3 binding confirmed
Gβγ-subunit complex binding GO:0002058 (or related) MF If Gβγ interaction confirmed as primary activity
ubiquitin-dependent protein catabolic process GO:0006511 BP If E3 ligase substrate adaptor role confirmed

Lead 6: Relationship Between GO:0042802 and GO:0051260

  • GO:0042802 (identical protein binding) is an MF term describing the binding activity itself
  • GO:0051260 (protein homooligomerization) is a BP term describing the process outcome
  • These are complementary, not redundant — if GO:0042802 is added as MF, it should complement rather than replace GO:0051260
  • For a gene with minimal experimental characterization, the BP term GO:0051260 may be more informative because it specifies the outcome (homo-oligomeric assembly) rather than just the binding activity

Evidence Base: Key Literature

Primary Evidence for KCTD14

Rolland et al. (2014) — A proteome-scale map of the human interactome network. PMID: 25416956
The HI-II-14 interactome provides the only direct experimental evidence for KCTD14 self-interaction. This systematic Y2H study detected KCTD14 self-binding in 3 of 4 replicas (MI-score 0.37). This is the foundation for any potential GO:0042802 annotation and represents the most important primary evidence for this hypothesis.

Esposito et al. (2022) — AlphaFold Predictions Provide Insights into the Structural Features of the Functional Oligomers of All Members of the KCTD Family. PMID: 36362127
Used AlphaFold multimer to predict oligomeric states for all KCTD members. Identified reliable pentameric models for KCTD14 and revealed its distinctive circle-like CTD architecture shared with KCTD7. This is the most detailed structural information available for KCTD14, albeit computational.

Family-Wide Structural Evidence

Smaldone et al. (2016) — The BTB domains of the potassium channel tetramerization domain proteins prevalently assume pentameric states. PMID: 27152988
EM data establishing pentamerization as the norm for KCTD BTB domains across multiple phylogenetic clades.

Ji et al. (2016) — Structural Insights into KCTD Protein Assembly and Cullin3 Recognition. PMID: 26334369
Crystal structures of KCTD1 and KCTD9 BTB pentamers. Crucially demonstrated that Cul3 binding affinity varies across the family — KCTD1 and KCTD16 do not detectably bind Cul3, challenging the assumption that all KCTDs are Cul3 adaptors.

Pinkas et al. (2017) — Structural complexity in the KCTD family of Cullin3-dependent E3 ubiquitin ligases. PMID: 28963344
Additional crystal structures establishing that KCTDs "commonly function as Cullin3 (Cul3)-dependent E3 ligases." Provides the structural framework for understanding KCTD oligomerization as a means to Cul3 binding.

Balasco et al. (2019) — The Structural Versatility of the BTB Domains of KCTD Proteins. PMID: 31370201
MD simulations showing BTB domain stability across oligomeric states and demonstrating that open pentameric conformations relate to functional roles, not structural instability.

Closest Paralog KCTD7

Staropoli et al. (2012) — A homozygous mutation in KCTD7 links neuronal ceroid lipofuscinosis to the ubiquitin-proteasome system. PMID: 22748208
Demonstrated that KCTD7 mutations can abrogate Cullin3 interaction, linking the KCTD7/14 subclade to the ubiquitin-proteasome system. The R184C mutation "abrogated interaction with cullin-3."

Metz et al. (2018) — KCTD7 deficiency defines a distinct neurodegenerative disorder with a conserved autophagy-lysosome defect. PMID: 30295347)
Showed that KCTD7 mutations cause impaired autophagy through Cul3-dependent mechanisms, establishing that the core function of KCTD7 is Cul3-dependent — not merely self-binding.

Family-Wide Functional Studies

Sloan/Barthet et al. (2023) — Multiple potassium channel tetramerization domain (KCTD) family members interact with Gβγ, with effects on cAMP signaling. PMID: 36736897
Family-wide screen showing nearly all KCTDs interact with Gβγ, with functional consequences for cAMP signaling. Raises the possibility that Gβγ modulation, not self-binding, is a more informative core function annotation for KCTD14.

Bhatt/Liao et al. (2023) — KCTD5 Forms Hetero-Oligomeric Complexes with Various Members of the KCTD Protein Family. PMID: 37762619
Demonstrated that KCTD hetero-oligomerization is widespread, suggesting KCTD14 may form mixed complexes in vivo — complicating the exclusive "identical protein binding" annotation.

Disease Context (Not MF Evidence)

Liang et al. (2025) — Dendritic cell-related gene signature in pancreatic cancer stratifies patient subtypes and implicates a KCTD14-TNF signaling axis. PMID: 41080575
Computational/scRNA-seq study proposing KCTD14 as an immunomodulatory oncogene acting through TNF-TNFR1 in pancreatic cancer. While not direct MF evidence, this is the most specific functional claim about KCTD14 in the current literature and warrants monitoring.

Limitations

  1. No direct biochemical characterization of KCTD14 exists. All functional inferences are based on family analogy, one Y2H result, and computational predictions. KCTD14 remains one of the least-characterized members of the KCTD family.

  2. The Y2H evidence is from a single high-throughput study. While the HI-II-14 interactome is well-validated at the dataset level, the individual KCTD14 self-interaction has not been independently confirmed by co-immunoprecipitation, BRET, or other orthogonal methods.

  3. AlphaFold predictions are not experimental evidence. The pentameric model and circle-like CTD cavity, while plausible and consistent with family trends, require experimental validation.

  4. Family-wide functional data cannot be directly transferred to KCTD14. The KCTD family shows considerable functional diversity: some are Cul3 adaptors, some are GABAB receptor modulators, some bind Gβγ, some do not bind Cul3 at all, and substrate specificity varies widely. Shared BTB domain architecture does not guarantee shared molecular function.

  5. Disease-context transcriptomic associations are not MF evidence. The recurring identification of KCTD14 in dengue, cancer, and diabetes transcriptomic studies reflects expression changes, not molecular function.

  6. The closely related KCTD7 has strong disease genetics, but even KCTD7's molecular function is incompletely characterized. While KCTD7 binds Cullin3 and regulates autophagy, the specific substrates and detailed mechanism remain under investigation, limiting knowledge transfer to KCTD14.

  7. This analysis could not programmatically access certain bioinformatics resources (e.g., live QuickGO API queries, tissue expression data from GTEx/HPA, PDB structure search). Annotation status and expression data were derived from literature and database records available in the knowledge base.

Conclusion

The seed hypothesis that identical protein binding (GO:0042802) is a core function of KCTD14 is partially supported as a factual claim about what KCTD14 likely does — it almost certainly self-associates via its BTB domain to form homo-oligomeric assemblies — but is not justified as a core function designation. Self-binding is a structural prerequisite shared across the entire KCTD family that enables downstream molecular activities (Cullin3 adaptor function, Gβγ modulation, receptor scaffolding), which are the true core functions for characterized family members. For KCTD14, the downstream molecular function remains experimentally undetermined.

The recommended curation approach is to consider adding GO:0042802 as a non-core MF annotation with IPI evidence from the Y2H self-interaction data (PMID: 25416956), while clearly noting that the core molecular function of KCTD14 awaits experimental characterization. The most promising leads for future core function identification are Cullin3 adaptor activity (by KCTD7 analogy), Gβγ modulation (by family-wide screen data), and the computationally proposed TNF-TNFR1 axis involvement.

Artifacts

KCTD14: CUL3 Substrate-Adaptor or Alternative Function?

(KCTD14-hypotheses/kgap-kctd14-cul3-adaptor-or-other/openscientist.md)
citations file

KCTD14: CUL3 Substrate-Adaptor or Alternative Function?

Research question: What is the evidence for human KCTD14 molecular function—specifically, does it act as a CUL3‑RING ubiquitin ligase (CRL3) substrate adaptor like several KCTD paralogs, or does it have another activity? What GO‑style curation posture is justified?

Date: 2026‑07‑07 · Iteration 1 (literature synthesis; no primary data files provided)

1. Summary (answer)

There is no direct experimental evidence that human KCTD14 binds CUL3, oligomerizes (beyond prediction), recognizes a substrate, or participates in a CRL3 complex. The entire KCTD14 primary literature is transcriptomic/biomarker work with no biochemical characterization. Its BTB/T1 fold and its close relationship to the validated Cul3 adaptor KCTD7 make a CRL3 substrate‑adaptor role a plausible, high‑priority hypothesis, but family membership is not sufficient to assert it, because Cul3 binding is demonstrably not universal among KCTDs (KCTD1 and KCTD16 do not bind Cul3). The only functionally defensible molecular‑function annotation today is protein homo‑oligomerization via the BTB/T1 domain, and even that rests on AlphaFold prediction plus family‑level inference rather than KCTD14‑specific experiment. KCTD14 should remain largely MF‑dark: keep non‑core "protein binding," optionally add homo‑oligomerization at an inferred (IBA/computational) evidence level, and do not annotate a specific adaptor/substrate‑recognition function.

2. Key findings and evidence

2.1 The KCTD14 primary literature is functionally empty

A systematic PubMed search returns only ~9 records mentioning KCTD14. All are transcriptomic signature / prognostic‑biomarker studies:
- Pancreatic‑cancer DC signature, "KCTD14–TNF axis" (correlative, not mechanistic) — PMID 41080575 (2025).
- Ovarian‑cancer methylation prognostic panel — PMID 36978087 (2023).
- Prostate‑cancer CAF signature — PMID 36195908 (2022).
- Dengue transcriptome biomarkers — PMIDs 39397194 (2025), 35220956 (2022).
- Diabetic rat ileal/colon transcriptome — PMID 34806320 (2021).
- Mouse oocyte/follicle expression — PMID 40044995 (2025).
- Incidental co‑regulation in a Znf230‑KO transcriptome — PMID 25505846 (2014).

None report protein interactions, enzymatic activity, oligomerization, or a CUL3 relationship. → KCTD14 is MF‑dark.

2.2 No KCTD14–CUL3 binding has ever been tested

The definitive family binding survey — Ji, Chu, Nielsen, Benlekbir, Rubinstein & Privé, "Structural Insights into KCTD Protein Assembly and Cullin3 Recognition" (PMID 26334369, 2016) — measured Cul3 binding for KCTD1, 5, 6, 9, 16, 17 but did not include KCTD14. No pulldown, ITC, cryo‑EM, or proteomic study places KCTD14 in a CRL3 complex.

2.3 Cul3 binding is member‑specific → family transfer is unreliable

From the same study (PMID 26334369): "the KCTD proteins 5, 6, 9 and 17 bind to Cul3 with high affinity, while the KCTD proteins 1 and 16 do not have detectable binding," and KCTDs "do not share many of the previously identified determinants for Cul3 binding." Because two tested KCTDs (KCTD1, KCTD16) fail to bind Cul3 despite the shared BTB fold, homology‑based inference of adaptor function to the untested KCTD14 is not safe.

2.4 KCTD14 oligomerization is predicted, not observed

Esposito, Balasco & Vitagliano, "AlphaFold Predictions Provide Insights into the Structural Features of the Functional Oligomers of All Members of the KCTD Family" (PMID 36362127, 2022) predict a reliable pentameric KCTD14 assembly, but with an atypical CTD: "the structure of the related proteins KCTD7 and KCTD14, although pentameric, appears to be characterized by a different organization of the CTD region, with the five chains forming a circle‑like structure with a large cavity." Family‑wide negative‑stain EM (Smaldone et al., PMID 27152988, 2016) shows KCTD BTB domains across five clades "prevalently assume pentameric states." Together these support homo‑oligomerization as an inherited fold property, but there is no KCTD14‑specific experimental oligomerization data, and the atypical CTD hints KCTD14/KCTD7 may engage partners non‑canonically.

2.5 The closest paralog KCTD7 is a validated Cul3 partner (hypothesis, not proof)

  • Staropoli et al. (PMID 22748208, 2012): an NCL/PME disease mutation "abrogated interaction with cullin‑3, a ubiquitin‑ligase component and known KCTD7 interactor."
  • Jiang, Wang, Kong & Zheng (PMID 37450587, 2023): cryo‑EM structures of the "KCTD5–Gβγ fusion complex and the KCTD7–Cul3 complex."

Because AlphaFold groups KCTD14 with KCTD7 by CTD architecture, KCTD7's proven Cul3 partnership makes a CRL3 role for KCTD14 a strong, testable prediction — but strictly a prediction, especially given §2.3.

2.6 Reliability of high‑throughput "protein binding" interactors

Reported KCTD14 GO "protein binding" annotations trace to high‑throughput/curated PPI compilations (e.g., Skoblov et al., PMID 23592240, 2013, which explicitly notes "The value of manual curation of PPIs and analysis of existing high‑throughput data should not be underestimated" but offers only hypotheses). Such Y2H/AP‑MS hits for a low‑expression, uncharacterized protein are prone to false positives, are non‑reciprocated, and none has been validated as a physiological KCTD14 substrate or partner. They justify only a non‑core, low‑confidence "protein binding" annotation, not a substrate‑recognition function.

3. Hypotheses: supported vs. refuted

Hypothesis Verdict Basis
KCTD14 is a proven CUL3/CRL3 substrate adaptor Not supported (no evidence) No KCTD14–CUL3 data exist (§2.2)
KCTD14 homo‑oligomerizes (BTB/T1 pentamer) Provisionally supported (computational + family IBA) AlphaFold pentamer + family EM (§2.4)
Family membership alone proves adaptor function Refuted KCTD1/KCTD16 don't bind Cul3 (§2.3)
CRL3 adaptor role is a worthwhile hypothesis to test Supported as hypothesis KCTD7 paralogy (§2.5)
Reported HT "protein binding" partners are physiological substrates Not supported Unvalidated HT hits (§2.6)
  1. Keep KCTD14 essentially MF‑dark. Retain only non‑core, low‑confidence protein binding (GO:0005515) from HT data, clearly flagged as unvalidated.
  2. Best‑justified positive annotation: protein homo‑oligomerization (GO:0051260) / identical protein binding, at an inferred/computational evidence level (AlphaFold prediction + family IBA), not IDA.
  3. Do NOT annotate Cul3‑RING ubiquitin ligase binding, ubiquitin‑protein transferase/ligase adaptor activity, or any specific substrate‑recognition MF. These are unsupported and would over‑annotate.
  4. Record the CRL3 substrate‑adaptor role as an open hypothesis (paralogy to KCTD7), pending direct experiment.

5. Limitations and future directions

Limitations. This is a literature‑only synthesis (no primary data). PMIDs below were confirmed to resolve via the PubMed search tool; DOIs are supplied from model knowledge and should be independently verified before publication‑grade use (flagged). Absence of evidence for KCTD14 reflects the field's neglect of this gene, not a demonstrated negative.

Experiments that would resolve the question.
- Co‑IP / ITC / AP‑MS of tagged KCTD14 vs. CUL3 (± the BTB determinants mutated) — the exact assay Ji 2016 applied to other KCTDs.
- Reconstituted in‑vitro ubiquitination with CUL3–RBX1–E2 to test ligase‑adaptor activity.
- SEC‑MALS/native‑MS/cryo‑EM to confirm the predicted pentamer and the atypical CTD cavity.
- Unbiased BioID/TurboID interactome in a physiologically relevant tissue to identify candidate substrates and test whether any HT "protein binding" hits reciprocate.

6. Citations (PMIDs confirmed via PubMed; DOIs to be verified)

  • PMID 26334369 — Ji et al. 2016, J Biol Chem — KCTD assembly & Cul3 recognition; member‑specific binding. DOI (verify): 10.1074/jbc.M115.669580.
  • PMID 36362127 — Esposito, Balasco, Vitagliano 2022, Int J Mol Sci — AlphaFold oligomers of all KCTDs incl. KCTD14. DOI (verify): 10.3390/ijms232113346.
  • PMID 27152988 — Smaldone et al. 2016, Biochim Biophys Acta Mol Cell Res — KCTD BTB domains are pentameric; KCTD6–Cul3 pinwheel. DOI (verify): 10.1016/j.bbamcr.2016.04.023.
  • PMID 22748208 — Staropoli et al. 2012, Am J Hum Genet — KCTD7–cullin‑3 interaction; NCL/PME. DOI (verify): 10.1016/j.ajhg.2012.05.023.
  • PMID 37450587 — Jiang, Wang, Kong, Zheng 2023, Sci Adv — cryo‑EM KCTD5–Gβγ and KCTD7–Cul3. DOI (verify): 10.1126/sciadv.adg8369.
  • PMID 24747150 — Balasco et al. 2014, PLoS One — KCTD5–Cul3 5:5 heterodecamer, Kd ≈ 59 nM. DOI (verify): 10.1371/journal.pone.0091093.
  • PMID 23592240 — Skoblov et al. 2013, BioEssays — KCTD PPI curation (hypothesis‑generating). DOI (verify): 10.1002/bies.201200169.
  • PMID 24268103 — Liu, Xiang, Sun 2013 — KCTD family review (structure/function/disease). DOI (verify): 10.1007/s12035‑013‑8555‑y.
  • PMID 34001146 — Angrisani et al. 2021, Semin Cancer Biol — KCTDs in cancer review. DOI (verify): 10.1016/j.semcancer.2021.05.019.
  • PMID 40925965 — Jiang & Zheng 2026 — KCTDs as regulators of GPCR biased signaling (Gβγ degradation). DOI: not confirmed (flag as uncached).
  • KCTD14 transcriptomic references: PMIDs 41080575, 40044995, 39397194, 36978087, 36195908, 35220956, 34806320, 25505846.

Suspect/uncached flags: All DOIs above are reconstructed from model knowledge and must be verified against CrossRef/PubMed. PMID 40925965 (2026) and PMID 41080575 (2025) are recent; treat their DOIs as unconfirmed. No previously reported KCTD14 citation was accepted without re‑confirmation in this PubMed session; any claim of a direct KCTD14–CUL3 experiment in secondary sources should be treated as suspect because none was found here.

OpenScientist prompt: KCTD14 CUL3 substrate-adaptor or alternative function

(KCTD14-hypotheses/kgap-kctd14-cul3-adaptor-or-other/prompt.md)

OpenScientist prompt: KCTD14 CUL3 substrate-adaptor or alternative function

Investigate the evidence for human KCTD14 molecular function, especially whether it acts as a CUL3-RING ubiquitin ligase substrate adaptor like several KCTD paralogs or instead has another activity.

Focus on:

  • direct evidence for KCTD14 binding to CUL3, oligomerization, substrates, ubiquitination, degradation, or CRL3 complex membership;
  • the reliability of reported high-throughput KCTD14 protein binding interactors and whether any are plausible physiological substrates or partners;
  • family-level KCTD/BTB evidence that can or cannot be transferred to KCTD14;
  • whether current GO-style curation should remain MF-dark/non-core binding only, support protein homooligomerization, or support a specific adaptor/substrate-recognition function.

Please include PMIDs and DOIs, flag uncached or suspect citations, and avoid relying on previously reported KCTD14 citations unless they resolve correctly in PubMed.

📄 View Raw YAML

 
id: Q9BQ13
gene_symbol: KCTD14
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: KCTD14 encodes a BTB/POZ domain-containing protein that is a member
  of the KCTD (potassium channel tetramerization domain-containing) protein
  family. The protein contains a T1-type BTB domain (residues 33-130) that is
  predicted to mediate pentameric homooligomerization based on family-wide
  structural analysis. Unlike many other KCTD family members, recent
  AlphaFold-based structural modeling (2024) suggests KCTD14 does NOT form a
  stable complex with Cullin3 (Cul3), indicating it may not function as a
  canonical CRL3 E3 ubiquitin ligase adaptor. The protein's primary molecular
  function remains poorly characterized, though high-throughput interaction
  studies have detected associations with STK16, TCF4, and ACSF3. KCTD14 shows
  low tissue specificity and has been detected in parotid gland and 138 other
  cell types or tissues.
existing_annotations:
- term:
    id: GO:0051260
    label: protein homooligomerization
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  review:
    summary: This annotation is inferred from InterPro domain analysis. The
      T1-type BTB domain (IPR003131) in KCTD14 is structurally homologous to
      domains that mediate oligomerization in other KCTD family members.
      AlphaFold-based structural surveys support that KCTD BTB domains
      frequently assemble into pentamers, and KCTD14 is expected to oligomerize
      via its BTB domain in keeping with the family trend (Balasco et al. 2024).
    action: KEEP_AS_NON_CORE
    reason: The annotation is well-supported by structural homology. The BTB/POZ
      domain is a well-characterized oligomerization domain. Family-wide
      AlphaFold analyses confirm that KCTD proteins typically form pentameric
      assemblies via their BTB domains. However, OpenScientist analysis argues
      this is best treated as a non-core assembly property that enables an
      unknown downstream molecular function, rather than the endpoint core
      function of KCTD14.
    supported_by:
    - reference_id: file:human/KCTD14/KCTD14-deep-research-falcon.md
      supporting_text: KCTD14 is expected to oligomerize via its BTB domain,
        most commonly as a homopentamer, in keeping with the family trend
    - reference_id: file:human/KCTD14/KCTD14-hypotheses/core-function-1-go-0042802/openscientist.md
      supporting_text: >-
        Self-binding is a structural prerequisite shared across the entire KCTD family that enables downstream molecular
        activities (Cullin3 adaptor function, Gβγ modulation, receptor scaffolding), which are the true core functions
        for characterized family members.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:25416956
  review:
    summary: This annotation derives from the Rolland et al. 2014 proteome-scale
      human interactome map, which used yeast two-hybrid screening to identify
      approximately 14,000 high-quality binary protein-protein interactions.
      This is a high-throughput study without specific KCTD14-focused
      validation.
    action: REMOVE
    reason: Per curation guidelines, GO:0005515 (protein binding) is
      uninformative and should be avoided. The term does not convey any specific
      information about the molecular function of KCTD14. The high-throughput
      nature of the study means specific interactors were not validated for
      KCTD14 individually. If specific binding partners were identified, more
      informative molecular function terms should be used instead. The
      interaction data itself may be useful but the GO:0005515 annotation is not
      informative.
    supported_by:
    - reference_id: PMID:25416956
      supporting_text: Here, we describe a systematic map of ?14,000
        high-quality human binary protein-protein interactions
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:28514442
  review:
    summary: This annotation derives from the BioPlex 2.0 study (Huttlin et al.
      2017), which used affinity-purification mass spectrometry (AP-MS) to
      identify protein-protein interactions for over 25% of human protein-coding
      genes. BioPlex 2.0 contains over 56,000 candidate interactions. This is a
      high-throughput proteome-scale study.
    action: REMOVE
    reason: Per curation guidelines, GO:0005515 (protein binding) is
      uninformative and should be avoided. While BioPlex 2.0 is a valuable
      resource for identifying potential interaction partners, the generic
      protein binding annotation does not convey specific functional information
      about KCTD14. The underlying interaction data may be valuable for
      characterizing KCTD14 function, but the GO annotation itself is not
      informative.
    supported_by:
    - reference_id: PMID:28514442
      supporting_text: BioPlex 2.0 is the largest collection of human co-complex
        data assembled from a single pipeline to date, containing 56,553
        interactions from 10,961 proteins
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:29892012
  review:
    summary: This annotation derives from Chen et al. 2018, which established an
      interactome perturbation framework to prioritize damaging missense
      mutations for developmental disorders. The study analyzed approximately
      2,000 de novo missense mutations in the context of the human interactome
      network. This is a computational/high-throughput study focused on mutation
      effects on interactions rather than direct functional characterization.
    action: REMOVE
    reason: Per curation guidelines, GO:0005515 (protein binding) is
      uninformative and should be avoided. This study was focused on identifying
      disease-relevant missense mutations by their effects on protein
      interactions, not on characterizing the specific molecular functions of
      individual proteins like KCTD14. The generic protein binding annotation
      provides no insight into KCTD14's specific function.
    supported_by:
    - reference_id: PMID:29892012
      supporting_text: Here we establish an experimentally and computationally
        integrated approach to investigate the functional impact of missense
        mutations in the context of the human interactome network
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:33961781
  review:
    summary: This annotation derives from the BioPlex 3.0/dual network study
      (Huttlin et al. 2021), which profiled protein interactions in both 293T
      and HCT116 cells using affinity-purification mass spectrometry. BioPlex
      3.0 includes 118,162 interactions among 14,586 proteins. This is a
      high-throughput proteome-scale study.
    action: REMOVE
    reason: Per curation guidelines, GO:0005515 (protein binding) is
      uninformative and should be avoided. While this dual-network approach
      provides valuable context about cell-type-specific interactions, the
      generic protein binding annotation does not convey any specific
      information about KCTD14's molecular function. If specific binding
      partners were validated, more informative terms should be used.
    supported_by:
    - reference_id: PMID:33961781
      supporting_text: BioPlex 3.0, results from affinity purification of 10,128
        human proteins-half the proteome-in 293T cells and includes 118,162
        interactions among 14,586 proteins
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: NAS
  review:
    summary: Added to align core_functions with existing annotations.
    action: NEW
    reason: >-
      GO:0042802 is a more specific annotation lead for the KCTD14 self-interaction
      detected by yeast two-hybrid, but OpenScientist analysis recommends treating
      it as a non-core assembly property rather than a core molecular function.
    supported_by:
    - reference_id: file:human/KCTD14/KCTD14-deep-research-falcon.md
      supporting_text: KCTD14 is expected to oligomerize via its BTB domain,
        most commonly as a homopentamer, in keeping with the family trend
    - reference_id: file:human/KCTD14/KCTD14-hypotheses/core-function-1-go-0042802/openscientist.md
      supporting_text: >-
        GO:0042802 could be validly assigned based on the Y2H self-interaction from [PMID: 25416956](https://pubmed.ncbi.nlm.nih.gov/25416956/),
        using IPI evidence code.
references:
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with
    GO terms
  findings:
  - statement: KCTD14 contains T1-type BTB domain (IPR003131) associated with
      oligomerization
- id: PMID:25416956
  title: A proteome-scale map of the human interactome network.
  findings:
  - statement: High-throughput yeast two-hybrid study identifying approximately
      14,000 binary protein-protein interactions
    supporting_text: Here, we describe a systematic map of ?14,000 high-quality
      human binary protein-protein interactions
  - statement: Study focused on generating reference interactome map, not
      individual protein characterization
    supporting_text: Just as reference genome sequences revolutionized human
      genetics, reference maps of interactome networks will be critical to fully
      understand genotype-phenotype relationships
- id: PMID:28514442
  title: Architecture of the human interactome defines protein communities and
    disease networks.
  findings:
  - statement: BioPlex 2.0 AP-MS study with over 56,000 candidate interactions
    supporting_text: BioPlex 2.0 is the largest collection of human co-complex
      data assembled from a single pipeline to date, containing 56,553
      interactions from 10,961 proteins
  - statement: BTB domains like those in KCTD proteins associated with
      Cullin-RING E3 ubiquitin ligase system
    supporting_text: The cullin domain was paired de novo with 15 additional
      domains, many of which also co-associated... Neighbors of proteins
      containing RBX1/2-binding cullin homology domains were enriched with BTB,
      BTB_2, SOCS and FBOX domains known to bind the cullin N-terminal domain
- id: PMID:29892012
  title: An interactome perturbation framework prioritizes damaging missense
    mutations for developmental disorders.
  findings:
  - statement: Computational framework for analyzing effects of missense
      mutations on protein interactions
    supporting_text: Here we establish an experimentally and computationally
      integrated approach to investigate the functional impact of missense
      mutations in the context of the human interactome network
  - statement: Study focused on autism and developmental disorders
    supporting_text: test our approach by analyzing ~2,000 de novo missense
      mutations found in autism subjects and their unaffected siblings
- id: PMID:33961781
  title: Dual proteome-scale networks reveal cell-specific remodeling of the
    human interactome.
  findings:
  - statement: BioPlex 3.0 with 118,162 interactions in 293T cells
    supporting_text: BioPlex 3.0, results from affinity purification of 10,128
      human proteins-half the proteome-in 293T cells and includes 118,162
      interactions among 14,586 proteins
  - statement: Comparison of context-specific interactome networks
    supporting_text: performing AP-MS in 293T and HCT116 cells has enabled
      comparison of two context-specific, proteome-scale interaction networks
- id: file:human/KCTD14/KCTD14-deep-research-falcon.md
  title: Deep research summary for KCTD14
  findings:
  - statement: KCTD14 BTB domain does not form stable complex with Cullin3 in
      AlphaFold-based modeling
    supporting_text: The 2024 AF survey explicitly reports "no stable complex
      detected" for KCTD14-Cul3 under a 5:5 symmetry assumption for the BTB-Cul3
      assembly
  - statement: KCTD14 is predicted NOT to be a canonical CRL3 adaptor based on
      structural analysis
    supporting_text: AF-based modeling found no stable Cul3 binding, arguing
      against a canonical CRL3 adaptor role
  - statement: KCTD proteins typically form pentameric assemblies via BTB
      domains
    supporting_text: KCTD14 is expected to oligomerize via its BTB domain, most
      commonly as a homopentamer, in keeping with the family trend
  - statement: KCTD14 clusters structurally with KCTD7 based on fold similarity
    supporting_text: AlphaFold-derived pseudo-phylogenetic analysis reported a
      specific structural pairing of KCTD7 with KCTD14
- id: file:human/KCTD14/KCTD14-hypotheses/core-function-1-go-0042802/openscientist.md
  title: OpenScientist evaluation of KCTD14 self-binding core-function hypothesis
  findings:
  - statement: OpenScientist found that KCTD14 self-binding is supported but should not be designated as the core function.
    supporting_text: >-
      Self-binding is a structural prerequisite shared across the entire KCTD family that enables downstream molecular
      activities (Cullin3 adaptor function, Gβγ modulation, receptor scaffolding), which are the true core functions
      for characterized family members.
- id: file:human/KCTD14/KCTD14-deep-research-cyberian.md
  title: Cyberian deep research on KCTD14 function
  findings: []
core_functions:
- description: >-
    KCTD14's core molecular function remains experimentally undetermined. It likely forms homooligomeric assemblies via its
    BTB domain, probably as pentamers based on family-wide structural analysis, but this self-association is best treated as
    a non-core assembly property until its downstream molecular role is established.
  supported_by:
  - reference_id: file:human/KCTD14/KCTD14-deep-research-falcon.md
    supporting_text: KCTD14 is expected to oligomerize via its BTB domain, most
      commonly as a homopentamer, in keeping with the family trend
  - reference_id: file:human/KCTD14/KCTD14-hypotheses/core-function-1-go-0042802/openscientist.md
    supporting_text: >-
      The recommended curation approach is to consider adding GO:0042802 as a non-core MF annotation with IPI evidence from
      the Y2H self-interaction data ([PMID: 25416956](https://pubmed.ncbi.nlm.nih.gov/25416956/)), while clearly noting
      that the core molecular function of KCTD14 awaits experimental characterization.
suggested_questions:
- question: What are the specific binding partners of KCTD14 and what biological
    processes do these interactions serve?
- question: Does KCTD14 have any scaffolding or regulatory functions independent
    of Cullin3?
- question: What is the subcellular localization of KCTD14 in different cell
    types?
- question: Does KCTD14 interact with STK16 and TCF4 in vivo and what are the
    functional consequences of these interactions?
suggested_experiments:
- description: Co-immunoprecipitation or proximity labeling (BioID/APEX) to
    identify and validate specific interaction partners
- description: Immunofluorescence or subcellular fractionation to determine
    cellular localization
- description: CRISPR knockout or knockdown studies to identify phenotypic
    consequences
- description: Biochemical characterization of oligomeric state using size
    exclusion chromatography or native PAGE