Affinage

KCTD7

BTB/POZ domain-containing protein KCTD7 · UniProt Q96MP8

Length
289 aa
Mass
33.1 kDa
Annotated
2026-06-10
24 papers in source corpus 11 papers cited in narrative 11 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

KCTD7 is a cytosolic substrate-adaptor subunit of a CUL3-RBX1 (CRL3) E3 ubiquitin ligase that governs neuronal proteostasis and excitability, and its loss-of-function causes progressive myoclonic epilepsy and neuronal ceroid lipofuscinosis (PMID:21710140, PMID:22748208, PMID:30295347, PMID:35921411, PMID:36964131). KCTD7 binds Cullin-3 directly, an interaction abrogated by the disease-causing p.Arg184Cys mutation (PMID:21710140, PMID:22748208, PMID:30295347, PMID:35921411, PMID:36964131). As the adaptor of this complex, KCTD7 directs two distinct ubiquitination programs: it executes atypical, non-degradative ubiquitination of the ubiquitous calpains—modifying calpain 1 at K398 with K6/K27/K29/K63 chains and calpain 2 with K6 chains—so that loss of KCTD7 drives calpain hyperactivation, aberrant substrate cleavage, and caspase-3 activation (PMID:36964131); and it targets CLN5 for proteasomal degradation, with patient mutations that disrupt KCTD7-CUL3 or KCTD7-CLN5 binding causing CLN5 to accumulate in the ER, disrupting CLN6/8-dependent lysosomal enzyme trafficking from ER to Golgi (PMID:35921411, PMID:36368077). Consistent with these proteostatic roles, KCTD7-deficient cells exhibit impaired autophagy (PMID:30295347). Independently, KCTD7 hyperpolarizes the resting membrane potential and lowers neuronal excitability through K+ conductance, and regulates the glutamine transporter SAT2, with multiple patient variants impairing K+ flux and glutamine transport (PMID:21710140, PMID:27742667). In vivo, Kctd7 is required for Purkinje cell survival, cerebellar and retinal microvascular patterning, and normal neuronal function, and pharmacological calpain inhibition largely prevents the neurodegenerative phenotype of Kctd7 knockout mice (PMID:35972048, PMID:31175897, PMID:36964131).

Mechanistic history

Synthesis pass · year-by-year structured walk · 10 steps
  1. 2011 High

    Established that KCTD7 is functionally an ion-conductance modulator and physically an E3-ligase adaptor, answering what molecular activities the protein carries.

    Evidence Patch clamp in transfected neurons plus Co-IP with Cullin-3

    PMID:21710140

    Open questions at the time
    • Whether K+ effect is direct channel modulation or indirect was not resolved
    • No structural basis for the CUL3 interaction
  2. 2012 Medium

    Linked disease pathogenesis to loss of the KCTD7-CUL3 interaction, connecting a clinical mutation to a defined molecular lesion.

    Evidence Co-IP and localization imaging of p.Arg184Cys vs wild-type KCTD7

    PMID:22748208

    Open questions at the time
    • Did not identify the ubiquitination substrate downstream of CUL3 binding
    • Single lab, cell-based system
  3. 2012 Medium

    Showed that several patient mutations do not perturb cytosolic localization, indicating mislocalization is not the universal disease mechanism.

    Evidence Subcellular localization imaging of mutant KCTD7 in culture

    PMID:22693283

    Open questions at the time
    • Negative result; functional consequence of these mutations not tested
    • No biochemical readout
  4. 2016 High

    Reconstituted KCTD7's K+-dependent hyperpolarization and SAT2/glutamine-transport regulation and demonstrated multiple patient variants impair these functions, tying excitability defects to disease.

    Evidence Heterologous expression and electrophysiology/transport assays in Xenopus oocytes with multiple variant alleles

    PMID:27742667

    Open questions at the time
    • Molecular mechanism by which KCTD7 affects K+ flux and SAT2 not defined
    • Relationship to its E3-adaptor role unclear
  5. 2018 Medium

    Implicated KCTD7 in the autophagy-lysosome pathway across species, broadening its role from excitability to proteostasis.

    Evidence Functional assays and EM in patient fibroblasts and Whi2-deficient yeast

    PMID:30295347

    Open questions at the time
    • Molecular target linking KCTD7 to autophagy not identified
    • Yeast Whi2 similarity is suggestive, not mechanistic
  6. 2019 Medium

    Demonstrated a non-cell-autonomous developmental role, showing neuronal Kctd7 drives retinal vascular patterning.

    Evidence Kctd7 knockout mouse with IHC, electroretinography, and vascular imaging

    PMID:31175897

    Open questions at the time
    • Signal mediating neuron-to-vessel communication unknown
    • Connection to ubiquitination/K+ activities not established
  7. 2021 Medium

    Confirmed in a neuronal cell type that disease variants impair K+ regulation and that Kctd7 loss produces seizure-correlated transcriptional changes in vivo.

    Evidence Whole-cell patch-clamp in neuroblastoma cells and kctd7 knockout zebrafish transcriptomics

    PMID:33970744

    Open questions at the time
    • Transcriptomic changes are downstream and non-specific
    • Direct channel target not identified
  8. 2022 High

    Defined a substrate of the CRL3-KCTD7 ligase, showing it degrades CLN5 to maintain lysosomal enzyme trafficking, mechanistically connecting KCTD7 loss to lysosomal dysfunction.

    Evidence Co-IP, ubiquitination and trafficking assays in KCTD7-deficient cells with patient mutations

    PMID:35921411 PMID:36368077

    Open questions at the time
    • Whether CLN5 turnover defects fully account for disease versus calpain effects unresolved
    • Single lab
  9. 2022 Medium

    Established a required role for Kctd7 in Purkinje cell survival and recapitulated the human neurodegenerative and seizure phenotype in mice.

    Evidence Kctd7 knockout mouse with histology, EEG, and behavioral assays

    PMID:35972048

    Open questions at the time
    • Cause of selective Purkinje vulnerability not defined
    • Molecular driver of degeneration not pinned down in this study
  10. 2023 High

    Identified calpains as direct substrates and showed KCTD7 mediates atypical non-degradative ubiquitination restraining calpain activity, with calpain inhibition rescuing the knockout phenotype—establishing a treatable mechanistic axis.

    Evidence In vitro ubiquitination with single-lysine mutants, proteomics, CRISPR/Cas9 KO mice, and pharmacological calpain-inhibitor rescue

    PMID:36964131

    Open questions at the time
    • How the non-degradative ubiquitin chains restrain calpain activity mechanistically is unresolved
    • Relative contribution of calpain versus CLN5 axes to disease not quantified

Open questions

Synthesis pass · forward-looking unresolved questions
  • How KCTD7's E3-adaptor activity, its K+/SAT2 regulatory function, and its autophagy and vascular-patterning roles are mechanistically integrated remains unresolved.
  • No structural model of the KCTD7-CUL3 complex or substrate engagement
  • Mechanism coupling KCTD7 to K+ conductance and SAT2 unknown
  • Whether ion-conductance and ubiquitination roles are independent or linked

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0060090 molecular adaptor activity 3 GO:0098772 molecular function regulator activity 3 GO:0140096 catalytic activity, acting on a protein 2
Localization
GO:0005829 cytosol 2
Pathway
R-HSA-112316 Neuronal System 2 R-HSA-392499 Metabolism of proteins 2 R-HSA-9612973 Autophagy 1
Partners
CAPN1CAPN2CLN5CUL3RBX1SLC38A2
Complex memberships
CRL3 (CUL3-RBX1-KCTD7) E3 ubiquitin ligase

Evidence

Reading pass · 11 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2011 KCTD7 expression hyperpolarizes the cell membrane and reduces the excitability of transfected neurons, as demonstrated by patch clamp experiments. The effect on resting membrane potential is mediated through K+ conductance changes. Patch clamp electrophysiology in transfected neurons Molecular neurobiology Medium 21710140
2011 KCTD7 directly interacts with Cullin-3 (a ubiquitin-ligase component), as demonstrated by co-immunoprecipitation assays. Co-immunoprecipitation Molecular neurobiology High 21710140 22748208 30295347 35921411 36964131
2012 The disease-causing missense mutation p.Arg184Cys in KCTD7 alters its subcellular localization and abrogates interaction with Cullin-3, linking loss of this interaction to NCL pathogenesis. Co-immunoprecipitation and subcellular localization imaging of mutant vs wild-type KCTD7 American journal of human genetics Medium 22748208
2012 Three patient missense mutations in KCTD7 did not affect its cytosolic subcellular distribution, indicating that these mutations do not alter localization. Subcellular localization imaging of mutant KCTD7 in cellular cultures Journal of medical genetics Medium 22693283
2016 Wild-type KCTD7 hyperpolarizes cells in a K+-dependent manner and regulates activity of the neuronal glutamine transporter SAT2 (Slc38a2) when expressed in Xenopus laevis oocytes. The disease-causing frameshift variant F232fs impairs K+ fluxes and obliterates SAT2-dependent glutamine transport. Four additional disease variants (R94W, R184C, N273I, Y276C) also showed impaired K+ flux regulation. Heterologous expression and electrophysiology/transport assays in Xenopus laevis oocytes Brain : a journal of neurology High 27742667
2018 Patient-derived KCTD7-deficient fibroblasts and yeast lacking Whi2 (a protein with sequence similarity to KCTD7) both exhibit impaired autophagy, consistent with brain pathology, suggesting KCTD7 has a conserved role in the autophagy-lysosome pathway. Cell-based functional assays in patient fibroblasts and knockout yeast, electron microscopy Annals of neurology Medium 30295347
2019 Neuronal Kctd7 (absent from vessels) is required for proper retinal vascular patterning; deletion of Kctd7 in mice causes defective superficial and deep vascular layer development, increased bipolar cell number, and retinal function deficits, demonstrating that neuronal Kctd7 drives vascular growth and patterning. Kctd7 knockout mouse, immunohistochemistry, electroretinography, vascular imaging Neurochemistry international Medium 31175897
2022 The CRL3-KCTD7 E3 ubiquitin ligase complex ubiquitinates CLN5 and targets it for proteasomal degradation. Patient-derived KCTD7 mutations disrupt either KCTD7-CUL3 or KCTD7-CLN5 interactions, leading to CLN5 accumulation in the ER, which in turn disrupts the CLN6/8-lysosomal enzyme interaction and impairs ER-to-Golgi trafficking of lysosomal enzymes. Co-immunoprecipitation, ubiquitination assays, subcellular fractionation/trafficking assays in KCTD7-deficient cells with patient-derived mutations Science advances High 35921411 36368077
2022 Kctd7 is required for Purkinje cell survival in the cerebellum; Kctd7-deficient mice develop seizures, locomotor defects, selective Purkinje cell degeneration, and cerebellar microvascular disorganization. Kctd7 knockout mouse, histology, EEG, behavioral assays Disease models & mechanisms Medium 35972048
2023 KCTD7 works in complex with Cullin-3 and Rbx1 to execute atypical, non-degradative ubiquitination of calpain 1 (at K398) and calpain 2 (at K280 and K674). KCTD7 mediates K6-, K27-, K29-, and K63-linked ubiquitin chains on calpain 1, and K6-linked chains on calpain 2. Loss of this ubiquitination leads to calpain hyperactivation, aberrant substrate cleavage, and caspase-3 activation. Kctd7 CRISPR/Cas9 knockout mice recapitulate human disease, and pharmacological calpain inhibition largely prevents behavioral and neurodegenerative phenotypes in these mice. CUL3-KCTD7 mediates ubiquitination of all ubiquitous calpains. In vitro ubiquitination assays, single-lysine ubiquitin mutants, Co-IP, CRISPR/Cas9 KO mice, pharmacological rescue, caspase-3 activity assay, proteomics (mass spectrometry) Cell discovery High 36964131
2021 Whole-cell patch-clamp analysis of neuroblastoma cells overexpressing patient KCTD7 variant alleles demonstrated aberrant potassium regulation, confirming that disease variants impair K+ conductance. Kctd7 knockout zebrafish showed global dysregulation of gene expression and increased c-fos transcription (correlated with seizure activity). Whole-cell patch-clamp in neuroblastoma cells, kctd7 knockout zebrafish with transcriptomic analysis Journal of neurogenetics Medium 33970744

Source papers

Stage 0 corpus · 24 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2012 A homozygous mutation in KCTD7 links neuronal ceroid lipofuscinosis to the ubiquitin-proteasome system. American journal of human genetics 89 22748208
2012 Novel mutations consolidate KCTD7 as a progressive myoclonus epilepsy gene. Journal of medical genetics 61 22693283
2011 Progressive myoclonic epilepsy-associated gene KCTD7 is a regulator of potassium conductance in neurons. Molecular neurobiology 59 21710140
2018 KCTD7 deficiency defines a distinct neurodegenerative disorder with a conserved autophagy-lysosome defect. Annals of neurology 51 30295347
2012 A compound heterozygous missense mutation and a large deletion in the KCTD7 gene presenting as an opsoclonus-myoclonus ataxia-like syndrome. Journal of neurology 45 22638565
2012 Novel mutation in potassium channel related gene KCTD7 and progressive myoclonic epilepsy. Annals of human genetics 32 22606975
2016 Pathogenic variants in KCTD7 perturb neuronal K+ fluxes and glutamine transport. Brain : a journal of neurology 30 27742667
2014 Linkage analysis and exome sequencing identify a novel mutation in KCTD7 in patients with progressive myoclonus epilepsy with ataxia. Epilepsia 28 25060828
2016 KCTD7-related progressive myoclonus epilepsy. Epileptic disorders : international epilepsy journal with videotape 24 27629772
2022 KCTD7 mutations impair the trafficking of lysosomal enzymes through CLN5 accumulation to cause neuronal ceroid lipofuscinoses. Science advances 22 35921411
2018 Progressive myoclonus epilepsy and ceroidolipofuscinosis 14: The multifaceted phenotypic spectrum of KCTD7-related disorders. European journal of medical genetics 18 30500434
2023 Calpain activity is negatively regulated by a KCTD7-Cullin-3 complex via non-degradative ubiquitination. Cell discovery 11 36964131
2024 KCTD7-related progressive myoclonic epilepsy: Report of 42 cases and review of literature. Epilepsia 9 38231304
2022 Kctd7 deficiency induces myoclonic seizures associated with Purkinje cell death and microvascular defects. Disease models & mechanisms 9 35972048
2022 Lysosomal dysfunction, autophagic defects, and CLN5 accumulation underlie the pathogenesis of KCTD7-mutated neuronal ceroid lipofuscinoses. Autophagy 9 36368077
2019 Progressive myoclonic epilepsy-associated gene Kctd7 regulates retinal neurovascular patterning and function. Neurochemistry international 9 31175897
2022 KCTD7-related progressive myoclonic epilepsy: report of three Indian families and review of literature. Clinical dysmorphology 8 34866617
2019 Exome sequencing identifies compound heterozygous KCTD7 mutations in a girl with progressivemyoclonus epilepsy. Clinica chimica acta; international journal of clinical chemistry 8 30825425
2021 Compound heterozygous KCTD7 variants in progressive myoclonus epilepsy. Journal of neurogenetics 7 33970744
2021 Nonsyndromic Early-Onset Epileptic Encephalopathies: Two Novel KCTD7 Pathogenic Variants and a Literature Review. Developmental neuroscience 3 34469883
2024 A novel pathogenic variant in the KCTD7 gene in a patient with neuronal ceroid lipofuscinosis (CLN14): a case report and review of the literature. BMC neurology 2 39350080
2025 Genetic insights into progressive myoclonic epilepsies: A case study of KCTD7 mutation in an Iranian-Azeri-Turkish family. Epilepsy & behavior reports 0 40123863
2025 Expanding Insights into <italic>KCTD7-</italic>Related Drug-Resistant Epilepsy: Three Novel Mutations in a Cohort of Iranian Pediatric Patients. Developmental neuroscience 0 40996926
2025 Case Report: Compound heterozygous KCTD7 variants in two siblings presenting with myoclonic epilepsy and ataxia. Frontiers in neuroscience 0 41311698

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