Affinage

KCTD7

BTB/POZ domain-containing protein KCTD7 · UniProt Q96MP8

Length
289 aa
Mass
33.1 kDa
Annotated
2026-04-28
24 papers in source corpus 10 papers cited in narrative 11 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

KCTD7 is a neuronal potassium conductance regulator and CUL3-RBX1 E3 ubiquitin ligase adaptor whose loss causes progressive myoclonic epilepsy and neuronal ceroid lipofuscinosis. It hyperpolarizes neuronal membranes in a K⁺-dependent manner and modulates the glutamine transporter SAT2 (SLC38A2), with disease-causing mutations impairing both K⁺ flux and SAT2-mediated glutamine transport (PMID:21710140, PMID:27742667). As a substrate adaptor within the CRL3-KCTD7 complex, it directs non-degradative (K6/K27/K29/K63-linked) ubiquitination of calpains 1 and 2 to suppress their hyperactivation, and degradative ubiquitination of CLN5 to maintain CLN6/8-dependent ER-to-Golgi trafficking of lysosomal enzymes (PMID:35921411, PMID:36964131). Kctd7 knockout mice develop myoclonic seizures, Purkinje cell degeneration, retinal neurovascular patterning defects, and calpain-driven neurodegeneration that is largely rescued by calpain inhibition (PMID:36964131, PMID:35972048, PMID:31175897).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 2011 High

    Establishing that KCTD7 regulates neuronal excitability answered the question of how loss-of-function mutations cause epilepsy: KCTD7 expression hyperpolarizes neurons via potassium conductance and physically interacts with Cullin-3.

    Evidence Patch-clamp electrophysiology in transfected neurons; co-immunoprecipitation

    PMID:21710140

    Open questions at the time
    • Identity of the potassium channel(s) directly modulated by KCTD7 remains unknown
    • Mechanism linking CUL3 interaction to potassium conductance was not established
  2. 2012 Medium

    Demonstrating that the patient R184C mutation abrogates CUL3 binding while KCTD7 localizes to the cytosol of neurons established that disrupted CUL3 interaction is a direct disease mechanism.

    Evidence Co-immunoprecipitation with patient mutant; immunofluorescence in cells and mouse brain

    PMID:22693283 PMID:22748208

    Open questions at the time
    • How loss of CUL3 binding mechanistically leads to neurodegeneration was not resolved
    • Different subcellular localization findings between two labs not fully reconciled
  3. 2016 High

    Reconstitution in Xenopus oocytes revealed that KCTD7 drives K⁺-dependent hyperpolarization and regulates the glutamine transporter SAT2, broadening the functional scope beyond ion channels to amino acid transport — with multiple patient variants ablating both functions.

    Evidence Heterologous expression in Xenopus oocytes; electrophysiology; glutamine transport assays with five patient variants

    PMID:27742667

    Open questions at the time
    • Whether SAT2 regulation is direct or secondary to membrane potential changes was not resolved
    • Relevance of glutamine transport deficiency to neurodegeneration in vivo was not tested
  4. 2018 Medium

    Patient fibroblasts and yeast lacking KCTD7-homolog Whi2 revealed impaired autophagy, establishing a conserved autophagy-lysosome axis as a disease mechanism.

    Evidence Cell-based autophagy assays in patient fibroblasts; yeast Whi2 knockout; electron microscopy

    PMID:30295347

    Open questions at the time
    • Molecular target through which KCTD7 controls autophagy was not identified
    • Yeast Whi2 functional equivalence to human KCTD7 not rigorously demonstrated
  5. 2019 Medium

    Kctd7 knockout mice revealed that neuronal KCTD7 non-cell-autonomously drives retinal vascular patterning and deep layer formation, extending its roles beyond excitability to neurovascular development.

    Evidence Conditional Kctd7 mouse knockout; retinal immunohistochemistry; vessel imaging; ERG

    PMID:31175897

    Open questions at the time
    • Signaling intermediates between neuronal KCTD7 and vascular patterning are unknown
    • Single lab finding; independent replication lacking
  6. 2021 Medium

    Patient KCTD7 variants confirmed to impair potassium regulation by patch clamp, and kctd7 knockout zebrafish showed global transcriptional dysregulation and elevated seizure marker c-fos, validating the excitability phenotype across species.

    Evidence Patch-clamp in neuroblastoma cells; zinc-finger nuclease zebrafish knockout; RNA-seq

    PMID:33970744

    Open questions at the time
    • Direct target genes versus secondary transcriptional changes not distinguished
    • Zebrafish phenotype not deeply characterized at the cellular or circuit level
  7. 2022 High

    Two key advances resolved KCTD7's dual ubiquitin ligase substrates and in vivo neurodegeneration: CRL3-KCTD7 ubiquitinates CLN5 for proteasomal degradation to maintain ER-to-Golgi lysosomal enzyme trafficking, and Kctd7 KO mice develop myoclonic seizures and Purkinje cell degeneration.

    Evidence Ubiquitination assays and ER trafficking studies in KCTD7-deficient cells; Kctd7 KO mouse with EEG and histology

    PMID:35921411 PMID:35972048

    Open questions at the time
    • Whether CLN5 accumulation alone is sufficient to cause neurodegeneration was not tested
    • Relationship between Purkinje cell death and cerebellar microvascular disorganization is correlative
  8. 2023 High

    Identification of calpains 1 and 2 as non-degradative ubiquitination substrates of CRL3-KCTD7, with specific lysine sites and chain types mapped, established that calpain hyperactivation is a central neurodegenerative mechanism — validated by pharmacological rescue in KO mice.

    Evidence In vitro ubiquitination with single-lysine ubiquitin mutants; CRISPR Kctd7 KO mouse; calpain inhibitor rescue; behavioral and neuropathological analysis

    PMID:36964131

    Open questions at the time
    • Relative contributions of calpain hyperactivation versus CLN5 accumulation to disease remain unclear
    • Whether non-degradative ubiquitination of calpains suppresses activity directly or via altered localization is not determined

Open questions

Synthesis pass · forward-looking unresolved questions
  • The identity of the potassium channel(s) directly modulated by KCTD7, the mechanistic link between K⁺ conductance and CUL3-mediated ubiquitination, and the relative pathogenic contribution of each substrate arm (calpain versus CLN5 versus SAT2) remain unresolved.
  • No potassium channel subunit has been identified as a direct KCTD7 binding partner
  • Whether CUL3-dependent and K⁺-conductance functions are mechanistically coupled or independent is unknown
  • Therapeutic relevance of calpain inhibition in human patients not established

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0060090 molecular adaptor activity 4 GO:0098772 molecular function regulator activity 2 GO:0140096 catalytic activity, acting on a protein 2
Localization
GO:0005829 cytosol 1
Pathway
R-HSA-112316 Neuronal System 3 R-HSA-392499 Metabolism of proteins 2 R-HSA-9609507 Protein localization 1 R-HSA-9612973 Autophagy 1
Partners
CAPN1CAPN2CLN5CUL3RBX1SLC38A2
Complex memberships
CRL3-KCTD7 (CUL3-KCTD7-RBX1)

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 measured by patch clamp experiments, indicating KCTD7 is a regulator of potassium conductance in neurons. Patch clamp electrophysiology in transfected neurons; co-immunoprecipitation Molecular neurobiology High 21710140
2011 KCTD7 directly interacts with Cullin-3 (a ubiquitin-ligase component), as demonstrated by co-immunoprecipitation, suggesting the effect of KCTD7 on membrane resting potential is mediated through Cullin-3. Co-immunoprecipitation Molecular neurobiology High 21710140 22748208
2012 The KCTD7 p.Arg184Cys patient mutation alters the subcellular localization pattern of KCTD7 and abrogates its interaction with Cullin-3, linking this loss of Cullin-3 interaction to NCL pathogenesis. Cell-based localization assay; co-immunoprecipitation with patient-derived mutant American journal of human genetics Medium 22748208
2012 KCTD7 shows cytosolic localization and predominant neuronal expression throughout the mouse brain; patient missense mutations do not affect subcellular distribution of KCTD7. Immunofluorescence in cellular cultures and mouse brain tissue Journal of medical genetics Medium 22693283
2016 Wild-type KCTD7 expressed in Xenopus laevis oocytes hyperpolarizes cells in a K+-dependent manner and regulates activity of the neuronal glutamine transporter SAT2 (Slc38a2); the frameshift variant F232fs impairs K+ fluxes and obliterates SAT2-dependent glutamine transport. Four additional disease-causing variants (R94W, R184C, N273I, Y276C) also impair these functions. Heterologous expression in Xenopus oocytes; electrophysiology; glutamine transport assays; structure modeling Brain : a journal of neurology High 27742667
2018 Patient-derived fibroblasts with KCTD7 mutations and yeast lacking Whi2 (a KCTD7 sequence-similar protein) show impaired autophagy, establishing a conserved autophagy-lysosome defect as a disease mechanism in KCTD7 deficiency. Cell-based functional assays of patient fibroblasts; knockout yeast; electron microscopy Annals of neurology Medium 30295347
2022 The CRL3-KCTD7 E3 ubiquitin ligase complex (comprising CUL3, KCTD7, and Rbx1) targets CLN5 for ubiquitination and proteasomal degradation; patient KCTD7 mutations disrupt KCTD7-CUL3 or KCTD7-CLN5 interactions, causing CLN5 accumulation in the ER, which impairs CLN6/8-mediated ER-to-Golgi trafficking of lysosomal enzymes. Co-immunoprecipitation; ubiquitination assays; KCTD7-deficient cell lines; ER trafficking assays; protein interaction studies with patient-derived variants Science advances High 35921411
2023 KCTD7 works in complex with Cullin-3 and Rbx1 to execute 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. CRISPR/Cas9 Kctd7 knockout mice recapitulate human disease and calpain inhibition largely prevents neurodegeneration. In vitro ubiquitination assays; single-lysine ubiquitin mutants; co-immunoprecipitation; CRISPR/Cas9 mouse knockout; pharmacological calpain inhibition; behavioral and neuropathological analysis Cell discovery High 36964131
2019 Kctd7 is expressed in inner retina neurons (not vessels) and its deletion in mice induces defective retinal vascular patterning (increased branching, vessel length, lacunarity) and delays emergence of superficial and deep vascular layers, accompanied by increased bipolar cell number and retinal function deficits, demonstrating neuronal Kctd7 drives neurovascular patterning. Kctd7 conditional mouse knockout; retinal immunohistochemistry; retinal vessel imaging; ERG functional assessment Neurochemistry international Medium 31175897
2022 Kctd7-deficient mice develop myoclonic seizures, locomotor defects, Purkinje cell degeneration in the cerebellum, and cerebellar microvascular disorganization, establishing Kctd7 as required for Purkinje cell survival and modulator of neuron excitability linked to microvascular integrity. Kctd7 knockout mouse; EEG seizure monitoring; histological analysis; immunofluorescence; behavioral testing Disease models & mechanisms Medium 35972048
2021 Whole-cell patch-clamp analysis of neuroblastoma cells overexpressing patient KCTD7 variant alleles demonstrated aberrant potassium regulation, and kctd7 knockout zebrafish showed global dysregulation of gene expression and increased c-fos transcription (a seizure activity marker). Patch-clamp electrophysiology; zinc finger nuclease zebrafish knockout; RNA-seq 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 50 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 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
2022 Kctd7 deficiency induces myoclonic seizures associated with Purkinje cell death and microvascular defects. Disease models & mechanisms 8 35972048
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