{"gene":"KCNK1","run_date":"2026-04-28T18:30:27","timeline":{"discoveries":[{"year":1996,"finding":"TWIK-1 (KCNK1) is a K+ channel with four transmembrane domains and two pore-forming P domains; it produces time-independent, weakly inward-rectifying currents in Xenopus oocytes; inward rectification requires internal Mg2+; the channel has a unitary conductance of 34 pS; activity is up-regulated by PKC activation and down-regulated by internal acidification; it is blocked by Ba2+, quinine, and quinidine.","method":"Heterologous expression in Xenopus oocytes, patch-clamp electrophysiology, pharmacology","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 — original channel characterization with in vitro electrophysiology, multiple pharmacological probes, and mutagenesis-level mechanistic detail; foundational paper >400 citations","pmids":["8605869"],"is_preprint":false},{"year":1996,"finding":"TWIK-1 subunits self-associate into homodimers via an interchain disulfide bridge involving Cys69 in the extracellular M1P1 linker loop; mutation of C69 to serine abolishes functional K+ channel expression.","method":"Biochemical dimerization assay, site-directed mutagenesis (C69S), functional expression in Xenopus oocytes","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis + biochemical assay with direct functional consequence; replicated by multiple subsequent studies; >140 citations","pmids":["8978667"],"is_preprint":false},{"year":1997,"finding":"Mouse TWIK-1 (mTWIK-1) has an apparent native molecular weight of ~81 kDa; treatment with reducing agent reveals a ~40 kDa form, confirming native dimerization via a disulfide bridge; mTWIK-1 currents in oocytes are K+-selective, instantaneous, and weakly inward-rectifying; blocked by Ba2+ and quinine; decreased by PKC and increased by internal acidification.","method":"Western blot with/without reducing agent, heterologous expression in Xenopus oocytes, electrophysiology","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1–2 — biochemical confirmation of disulfide-linked dimer in native brain tissue plus electrophysiology; independent replication of human TWIK-1 findings","pmids":["9013852"],"is_preprint":false},{"year":2009,"finding":"TWIK-1 contributes to the background passive K+ conductance of mature hippocampal astrocytes; cloned rat TWIK-1 in CHO cells conducts Cs+ currents (PCs/PK = 0.10); astrocytic passive conductance is inhibited ~58% by 200 µM quinine (IC50 for TWIK-1 = 85 µM); TWIK-1 protein co-localizes with astrocytic markers GLAST and GFAP in hippocampal stratum radiatum.","method":"Patch-clamp electrophysiology in CHO cells and hippocampal slices, pharmacology, immunocytochemistry","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (electrophysiology, pharmacology, immunolocalization) in native tissue and heterologous system; >140 citations","pmids":["19571146"],"is_preprint":false},{"year":2011,"finding":"TWIK-1 changes ion selectivity from K+-selective to Na+-permeable under subphysiological extracellular K+ (hypokalemia), conducting inward leak Na+ currents; Thr118 within the selectivity filter sequence TxGYG is required for this altered selectivity; TWIK-1 knockdown in human primary cardiac myocytes eliminates paradoxical depolarization in low [K+]o.","method":"Patch-clamp electrophysiology, site-directed mutagenesis (T118 variants), siRNA knockdown in human spherical primary cardiac myocytes, ectopic expression in HL-1 and CHO cells","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis identifies critical residue; loss-of-function in human primary cells confirms physiological role; multiple orthogonal approaches","pmids":["21653227"],"is_preprint":false},{"year":2013,"finding":"TWIK-1 is primarily localized in intracellular cytoplasmic compartments (~55%) and mildly hydrophobic internal compartment fractions (~41%), with only ~5% at the plasma membrane of hippocampal astrocytes, limiting its contribution to whole-cell passive conductance; TWIK-1 knockout astrocytes show more negative resting potential and reduced inward rectification and Cs+ permeability without global change in passive conductance.","method":"Subcellular fractionation, TWIK-1 knockout mice, whole-cell patch-clamp in hippocampal slices","journal":"Frontiers in cellular neuroscience","confidence":"High","confidence_rationale":"Tier 2 — fractionation plus genetic knockout with defined electrophysiological phenotype; multiple orthogonal methods","pmids":["24368895"],"is_preprint":false},{"year":2014,"finding":"Native TWIK-1 forms a functional heterodimeric channel with TREK-1 at the plasma membrane of astrocytes via a disulfide bridge between Cys69 of TWIK-1 and Cys93 of TREK-1; surface expression of TWIK-1 and TREK-1 are interdependent; TWIK-1/TREK-1 heterodimers mediate astrocytic passive conductance and cannabinoid-induced glutamate release from astrocytes.","method":"Co-immunoprecipitation, gene silencing (shRNA), disulfide bond identification by mutagenesis, surface biotinylation, patch-clamp electrophysiology in native astrocytes","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1–2 — reciprocal Co-IP, mutagenesis identifying disulfide bond, gene silencing with functional readouts; >120 citations","pmids":["24496152"],"is_preprint":false},{"year":2014,"finding":"TWIK-1 is expressed and localized mainly in soma and proximal dendrites of dentate gyrus granule cells (DGGCs); gene silencing of TWIK-1 reduces outwardly rectifying K+ current density, causes depolarizing shift in resting membrane potential, enhances firing rate, increases EPSP amplitude, and impairs EPSP-spike coupling in perforant path synaptic transmission.","method":"shRNA gene silencing, whole-cell patch-clamp in mouse hippocampal DGGCs, immunofluorescence","journal":"Molecular brain","confidence":"High","confidence_rationale":"Tier 2 — clean gene silencing with multiple defined electrophysiological phenotypes plus localization data","pmids":["25406588"],"is_preprint":false},{"year":2015,"finding":"Lipid tails from both membrane leaflets can occupy fenestrations in the TWIK-1 pore and partially penetrate into the inner pore cavity; there is an inverse correlation between lipid tail occupancy and water content within the hydrophobic barrier, but dewetting (pore closure) also occurs in the absence of lipid tails, indicating that hydrophobic side chains lining the pore cavity are the primary determinant of the hydrophobic barrier.","method":"Molecular dynamics (MD) simulations based on TWIK-1 crystal structure","journal":"Channels (Austin, Tex.)","confidence":"Medium","confidence_rationale":"Tier 4 — computational MD study; no direct experimental mutagenesis validation in this paper","pmids":["25487004"],"is_preprint":false},{"year":2015,"finding":"mGluR3 activation (Gi/Go-coupled) triggers translocation of TWIK-1 channels from cytoplasm to the plasma membrane of hippocampal astrocytes via a Rab-mediated recycling endosome trafficking pathway; this membrane recruitment is associated with membrane depolarization and enhanced NH4+ uptake (~30% potentiation), a process absent in TWIK-1 knockout astrocytes.","method":"Live-cell imaging of TWIK-1 trafficking, electrophysiology (VM response to NH4Cl), TWIK-1 knockout comparison, pharmacological mGluR3 activation","journal":"Molecular neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 — KO controls plus imaging of translocation plus functional electrophysiology; single lab","pmids":["26553349"],"is_preprint":false},{"year":2015,"finding":"KCNK1 overexpression inhibits RANKL-induced osteoclast differentiation by attenuating Ca2+ oscillations and suppressing JNK activation and NFATc1 expression; conversely, KCNK1 knockdown enhances osteoclastogenesis, JNK activation and NFATc1 expression, placing KCNK1 as a negative regulator upstream of the Ca2+/JNK-NFATc1 axis.","method":"Overexpression and siRNA knockdown of KCNK1 in osteoclast precursors, Ca2+ imaging, immunoblotting for JNK/NFATc1, osteoclast differentiation assay","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2–3 — bidirectional genetic manipulation (OE and KD) with multiple molecular readouts; single lab","pmids":["26208638"],"is_preprint":false},{"year":2016,"finding":"MD simulations reveal that the TWIK-1 selectivity filter (SF) diverges from canonical K+ channel structure due to non-conserved residues T118 (pore domain 1) and L228 (pore domain 2); T118 behavior is linked to dynamic selectivity enabling Na+ influx at subphysiological K+ concentrations, consistent with inactivation-like SF gating.","method":"Molecular dynamics simulations (~1 µs cumulative) based on TWIK-1 crystal structure","journal":"Biophysical journal","confidence":"Medium","confidence_rationale":"Tier 4 — computational only, but consistent with experimental mutagenesis data from other papers (T118)","pmids":["27558721"],"is_preprint":false},{"year":2016,"finding":"TWIK-1 is required for normal heart rate and atrial morphology in zebrafish; knockdown of kcnk1a or kcnk1b causes bradycardia and atrial dilation; the phenotype is partially rescued by wild-type human KCNK1 mRNA but not by a dominant-negative variant; zebrafish and human TWIK-1 channels show predominant localization in the endosomal compartment and produce K+ currents sensitive to external K+ concentration and acidic pH.","method":"Morpholino knockdown in zebrafish, mRNA rescue, two-electrode voltage-clamp in Xenopus oocytes, cellular localization by microscopy","journal":"Journal of molecular and cellular cardiology","confidence":"High","confidence_rationale":"Tier 2 — genetic knockdown + mRNA rescue in vertebrate model with defined cardiac phenotypes + electrophysiology; multiple orthogonal approaches","pmids":["27103460"],"is_preprint":false},{"year":2018,"finding":"TWIK-1 associates with TASK-3 to form a heterodimeric channel in dentate gyrus granule cells (DGGCs) and in COS-7 cells; TWIK-1/TASK-3 heterodimers display outwardly rectifying currents and contribute to intrinsic excitability of DGGCs; neurotensin-neurotensin receptor 1 (NT-NTSR1) signaling depolarizes DGGCs by inhibiting TWIK-1/TASK-3 heterodimeric channels.","method":"Co-immunoprecipitation in hippocampal tissue and COS-7 cells, shRNA gene silencing, patch-clamp electrophysiology in DGGCs, pharmacological activation of NTSR1","journal":"Experimental & molecular medicine","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP in native tissue and heterologous system, gene silencing with defined electrophysiological phenotype, receptor-mediated pathway placement","pmids":["30416196"],"is_preprint":false},{"year":2019,"finding":"The low intrinsic functional activity of TWIK-1 is dominated by instability of the conductive conformation of the selectivity filter (SF gate) in the presence of K+; Rb+, NH4+, and Cs+ promote a pH-dependent activated SF conformation; intracellular K+ potently inhibits TWIK-1 Rb+ currents (IC50 = 2.8 mM); voltage-dependent activation of TWIK-1 requires non-physiological strong depolarization.","method":"Patch-clamp electrophysiology with various permeant ions, systematic evaluation of proposed silencing mechanisms (sumoylation, internalization, hydrophobic barrier) using mutagenesis and pharmacology","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — systematic in vitro electrophysiology with multiple ion species, mutagenesis, and pharmacological dissection of competing mechanisms","pmids":["31806709"],"is_preprint":false},{"year":2013,"finding":"Nuclear receptor CAR directly binds a 97-bp response element (-2441/-2345) within the Kcnk1 promoter to drive male-specific transcription of Kcnk1 in mouse liver upon phenobarbital treatment; this activation requires the pituitary gland (abrogated by hypophysectomy); Kcnk1 knockout mice show enhanced phenobarbital-induced hepatic hyperplasia, establishing KCNK1 as a CAR-induced anti-hyperplasia factor.","method":"ChIP (CAR binding to Kcnk1 promoter), hypophysectomy experiment, Kcnk1 knockout mice with phenobarbital treatment, promoter reporter assay","journal":"Toxicological sciences","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP identifies direct transcriptional mechanism; KO mice provide functional evidence; single lab","pmids":["23291559"],"is_preprint":false},{"year":2020,"finding":"Spadin (a TREK-1 inhibitor) dramatically reduces astrocytic passive conductance in brain slices; gene silencing demonstrates that spadin-sensitive currents are mediated by TWIK-1/TREK-1 heterodimeric channels in cultured astrocytes and hippocampal astrocytes from brain slices.","method":"Patch-clamp electrophysiology in brain slices and cultured astrocytes, shRNA gene silencing of TWIK-1 and/or TREK-1, pharmacology with spadin","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2–3 — pharmacology combined with bidirectional gene silencing; confirms TWIK-1/TREK-1 heterodimer as passive conductance machinery","pmids":["33348878"],"is_preprint":false},{"year":2021,"finding":"AEG-1 (MTDH) binds directly to TWIK-1 mRNA and stabilizes it, thereby regulating TWIK-1 protein expression and TWIK-1-mediated K+ currents in astrocytes; AEG-1 knockdown downregulates TWIK-1 mRNA and protein, and reduces TWIK-1-mediated currents.","method":"RNA immunoprecipitation (AEG-1 binding to TWIK-1 mRNA), shRNA knockdown, qPCR, immunocytochemistry, patch-clamp electrophysiology","journal":"Brain sciences","confidence":"Medium","confidence_rationale":"Tier 2–3 — RNA-IP plus functional electrophysiology; single lab","pmids":["33440655"],"is_preprint":false},{"year":2023,"finding":"In the dorsal spinal horn, ciRNA-Kat6b acts as a sponge for miRNA-26a; nerve injury downregulates ciRNA-Kat6b, increasing free miRNA-26a which binds the 3'UTR of Kcnk1 mRNA and promotes its degradation, reducing KCNK1 protein and contributing to neuropathic pain; rescuing ciRNA-Kat6b restores KCNK1 and alleviates pain hypersensitivity.","method":"Luciferase reporter assay (miRNA-26a targeting Kcnk1 3'UTR), RNA immunoprecipitation (ciRNA-Kat6b/miRNA-26a interaction), Western blot, immunofluorescence, behavioral pain assays, CCI neuropathic pain model","journal":"CNS neuroscience & therapeutics","confidence":"Medium","confidence_rationale":"Tier 2–3 — luciferase validation of miRNA-mRNA interaction + in vivo rescue experiments; single lab","pmids":["37144575"],"is_preprint":false},{"year":2024,"finding":"KCNK1 promotes glycolysis and lactate production in breast cancer cells by directly binding to and activating LDHA; elevated LDHA activity promotes H3K18 lactylation and transcription of downstream genes including LDHA itself (positive feedback); this axis reduces tumor cell stiffness and adhesion, facilitating proliferation, invasion, and metastasis.","method":"Co-immunoprecipitation (KCNK1-LDHA binding), glycolysis/lactate assays, histone lactylation analysis (H3K18), in vitro invasion/proliferation assays, in vivo xenograft models","journal":"PLoS biology","confidence":"Medium","confidence_rationale":"Tier 2–3 — Co-IP identifies direct KCNK1-LDHA interaction; functional in vitro and in vivo readouts; single lab; unusual non-channel mechanism","pmids":["38905316"],"is_preprint":false},{"year":2024,"finding":"siRNA knockdown of KCNK1 in IPAH-PASMCs causes membrane depolarization, decreases cytosolic Ca2+, and suppresses proliferation and migration; elevated KCNK1 expression in IPAH-PASMCs facilitates proliferation and migration via enhanced Ca2+ signaling and elevated JNK phosphorylation.","method":"siRNA knockdown of KCNK1, patch-clamp electrophysiology, Ca2+ imaging, proliferation/migration assays, Western blot for pJNK, in IPAH patient-derived PASMCs and experimental PH animal models","journal":"Frontiers in cardiovascular medicine","confidence":"Medium","confidence_rationale":"Tier 2 — siRNA knockdown with multiple molecular and functional readouts; validated in multiple animal models; single lab","pmids":["38410243"],"is_preprint":false},{"year":2024,"finding":"TWIK-1 (KCNK1) mediates K+ currents responsible for background passive conductance in astrocytes; TWIK-1 deficiency (exon 1 CRISPR-Cas9 knockout) increases susceptibility to kainic acid-induced seizures, demonstrating that TWIK-1-mediated astrocytic passive conductance has a neuroprotective role in seizure threshold.","method":"CRISPR-Cas9 exon 1 knockout mice, patch-clamp electrophysiology in astrocytes, kainic acid seizure model, comparison with exon 2-deleted (partial) KO","journal":"iScience","confidence":"High","confidence_rationale":"Tier 2 — clean genetic KO with defined electrophysiological and behavioral phenotypes; resolves prior KO artifact","pmids":["39811670"],"is_preprint":false}],"current_model":"KCNK1/TWIK-1 is a homodimeric (via C69 disulfide) or heterodimeric (with TREK-1 via C69–C93 disulfide, or with TASK-3) two-pore domain background K+ channel that is constitutively retained in intracellular compartments and trafficked to the plasma membrane by mGluR3/Rab-dependent signaling; at the surface its selectivity filter gate is intrinsically unstable in physiological K+, but switches to Na+ permeability under hypokalemia (requiring selectivity filter residue T118); it sets resting membrane potential in hippocampal astrocytes (where its passive conductance guards against seizures) and dentate granule neurons, is regulated transcriptionally by nuclear receptor CAR and post-transcriptionally by AEG-1/miRNA-26a, and in non-channel contexts can directly bind and activate LDHA to promote histone lactylation in cancer cells."},"narrative":{"teleology":[{"year":1996,"claim":"Establishing KCNK1 as the founding two-pore-domain K+ channel resolved its basic biophysical identity: a time-independent, weakly inward-rectifying K+ conductance modulated by PKC and intracellular pH, with a defined pharmacological profile (Ba2+, quinine blockade).","evidence":"Heterologous expression and patch-clamp in Xenopus oocytes","pmids":["8605869"],"confidence":"High","gaps":["Physiological context unknown","Mechanism of PKC up-regulation not delineated","Gating mechanism at molecular level unresolved"]},{"year":1996,"claim":"Demonstrating that TWIK-1 assembles as a disulfide-linked homodimer via Cys69 established the structural basis for channel formation and showed that dimerization is required for function.","evidence":"Site-directed mutagenesis (C69S) and biochemical dimerization assay in oocytes, confirmed by Western blot of native mouse brain protein","pmids":["8978667","9013852"],"confidence":"High","gaps":["Whether heterodimers form in vivo unknown","Structure beyond dimerization interface unresolved"]},{"year":2009,"claim":"Identifying TWIK-1 as a major contributor to background passive conductance in hippocampal astrocytes placed the channel in a defined physiological context and explained its role in setting astrocytic resting membrane potential.","evidence":"Patch-clamp in CHO cells and hippocampal slices with quinine pharmacology and immunocytochemistry","pmids":["19571146"],"confidence":"High","gaps":["Relative contribution versus other K2P channels not fully dissected","Mechanism of intracellular retention unclear"]},{"year":2011,"claim":"Discovering that TWIK-1 switches from K+- to Na+-permeable under hypokalemia, dependent on selectivity filter residue Thr118, revealed a dynamic ion selectivity mechanism with direct pathophysiological relevance for cardiac depolarization.","evidence":"Site-directed mutagenesis of T118, siRNA knockdown in human primary cardiac myocytes, patch-clamp","pmids":["21653227"],"confidence":"High","gaps":["Structural basis of selectivity switch not experimentally determined","In vivo cardiac phenotype in mammals not established"]},{"year":2013,"claim":"Subcellular fractionation and knockout studies showed that ~95% of TWIK-1 is retained intracellularly, explaining its low functional surface activity and reconciling the discrepancy between high transcript abundance and modest whole-cell current.","evidence":"Subcellular fractionation of astrocytes, TWIK-1 knockout mice with electrophysiology","pmids":["24368895"],"confidence":"High","gaps":["Molecular machinery mediating intracellular retention not identified","Whether retention is constitutive or dynamically regulated was unclear"]},{"year":2014,"claim":"Identification of TWIK-1/TREK-1 heterodimers linked by a Cys69–Cys93 disulfide bridge established that TWIK-1 forms obligate heteromeric channels at the astrocyte surface, mediating passive conductance and cannabinoid-induced glutamate release, and later confirmed as spadin-sensitive channels.","evidence":"Reciprocal Co-IP, mutagenesis, surface biotinylation, gene silencing, patch-clamp in astrocytes; pharmacology with spadin","pmids":["24496152","33348878"],"confidence":"High","gaps":["Stoichiometry and structure of heterodimer not resolved","Whether TWIK-1 homodimers also contribute at the surface remains debated"]},{"year":2014,"claim":"Gene silencing in dentate granule cells revealed that TWIK-1 carries outwardly rectifying currents that maintain hyperpolarized resting potential and modulate synaptic integration at the perforant path, establishing a neuronal (not only glial) role.","evidence":"shRNA in mouse hippocampal DGGCs with patch-clamp electrophysiology","pmids":["25406588"],"confidence":"High","gaps":["Whether the neuronal current is homodimeric or heterodimeric unresolved at this point"]},{"year":2015,"claim":"Demonstrating that mGluR3 activation drives Rab-dependent translocation of TWIK-1 from cytoplasm to plasma membrane identified a receptor-mediated trafficking mechanism that dynamically regulates astrocytic TWIK-1 surface expression.","evidence":"Live-cell imaging, electrophysiology, pharmacological mGluR3 activation, TWIK-1 KO comparison in astrocytes","pmids":["26553349"],"confidence":"Medium","gaps":["Specific Rab isoform not identified","Signaling intermediates between Gi/Go and Rab machinery not mapped","Single-lab finding"]},{"year":2016,"claim":"Zebrafish knockdown of kcnk1a/b causing bradycardia and atrial dilation, rescuable by human KCNK1, established a conserved cardiac pacemaking role and confirmed predominant endosomal localization across species.","evidence":"Morpholino knockdown in zebrafish with human mRNA rescue, electrophysiology in oocytes","pmids":["27103460"],"confidence":"High","gaps":["Mammalian in vivo cardiac phenotype not confirmed","Channel composition in cardiomyocytes (homo- vs heterodimer) unknown"]},{"year":2018,"claim":"Identification of TWIK-1/TASK-3 heterodimers in dentate granule cells, inhibited by neurotensin-NTSR1 signaling, resolved the composition of the neuronal TWIK-1 channel and linked it to a neuromodulatory pathway.","evidence":"Reciprocal Co-IP in hippocampal tissue and COS-7 cells, shRNA, patch-clamp, NTSR1 pharmacology","pmids":["30416196"],"confidence":"High","gaps":["Proportion of TWIK-1 in homodimer vs TASK-3 heterodimer in neurons not quantified","Downstream behavioral consequences of NTSR1-mediated inhibition unexplored"]},{"year":2019,"claim":"Systematic electrophysiological dissection showed that the primary mechanism underlying TWIK-1's low basal activity is instability of the selectivity filter conductive state in K+, rather than previously proposed sumoylation or internalization, resolving a long-standing debate.","evidence":"Patch-clamp with multiple permeant ions (Rb+, NH4+, Cs+), mutagenesis, pharmacology","pmids":["31806709"],"confidence":"High","gaps":["Structural dynamics of SF gating not captured experimentally","Whether SF instability is modulated by heterodimer partners unknown"]},{"year":2024,"claim":"CRISPR-Cas9 full knockout of TWIK-1 demonstrated that astrocytic TWIK-1 passive conductance is neuroprotective, as KO mice show heightened seizure susceptibility to kainic acid, resolving a prior artifact from partial exon-2 deletion.","evidence":"Exon 1 CRISPR-Cas9 KO mice, patch-clamp in astrocytes, kainic acid seizure model","pmids":["39811670"],"confidence":"High","gaps":["Whether seizure phenotype is astrocyte-autonomous vs includes neuronal TWIK-1 loss not distinguished","Rescue experiment not performed"]},{"year":2024,"claim":"An unexpected non-channel function was reported: KCNK1 directly binds and activates LDHA, promoting glycolysis, histone H3K18 lactylation, and a positive-feedback transcriptional loop that drives breast cancer proliferation and metastasis.","evidence":"Co-IP of KCNK1-LDHA, glycolysis/lactate assays, histone lactylation analysis, xenograft models","pmids":["38905316"],"confidence":"Medium","gaps":["Whether this function requires channel activity is untested","No independent replication","Structural basis of KCNK1-LDHA interaction unknown"]},{"year":null,"claim":"Key unresolved questions include the structural basis of selectivity filter gating and the Na+-permeability switch, how heterodimer partner choice (TREK-1 vs TASK-3) is determined in different cell types, the molecular machinery mediating constitutive intracellular retention, and whether the non-channel LDHA-activating function is physiologically relevant beyond cancer.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution structure of full-length TWIK-1 in active/inactive states","In vivo mammalian cardiac phenotype not established","Channel-independent functions lack independent replication"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,3,4,6,7,13,14,21]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[19]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,5,6,9]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[5,9,12]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[5]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[3,7,13,21]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,4,14]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[9,10,13]}],"complexes":["TWIK-1 homodimer","TWIK-1/TREK-1 heterodimer","TWIK-1/TASK-3 heterodimer"],"partners":["KCNK2","KCNK9","LDHA","MTDH"],"other_free_text":[]},"mechanistic_narrative":"KCNK1 (TWIK-1) is a two-pore-domain potassium channel that assembles as a disulfide-linked homodimer (via Cys69) or as heterodimers with TREK-1 (via Cys69–Cys93) or TASK-3, and sets resting membrane potential in hippocampal astrocytes and dentate granule neurons [PMID:8978667, PMID:24496152, PMID:30416196, PMID:25406588]. The channel is constitutively retained in intracellular compartments with only ~5% at the plasma membrane, and surface delivery is stimulated by mGluR3/Gi–Rab-dependent trafficking from recycling endosomes [PMID:24368895, PMID:26553349]. Its selectivity filter, which contains the non-canonical residue Thr118, is intrinsically unstable in physiological K+, accounting for low basal activity, but switches to Na+ permeability under hypokalemic conditions, contributing to paradoxical depolarization in cardiac myocytes [PMID:31806709, PMID:21653227]. Astrocytic TWIK-1-mediated passive conductance is neuroprotective, as TWIK-1 knockout mice show increased seizure susceptibility to kainic acid [PMID:39811670]."},"prefetch_data":{"uniprot":{"accession":"O00180","full_name":"Potassium channel subfamily K member 1","aliases":["Inward rectifying potassium channel protein TWIK-1","Potassium channel K2P1","Potassium channel KCNO1"],"length_aa":336,"mass_kda":38.1,"function":"Ion channel that contributes to passive transmembrane potassium transport and to the regulation of the resting membrane potential in brain astrocytes, but also in kidney and in other tissues (PubMed:15820677, PubMed:21653227). Forms dimeric channels through which potassium ions pass in accordance with their electrochemical gradient. The channel is selective for K(+) ions at physiological potassium concentrations and at neutral pH, but becomes permeable to Na(+) at subphysiological K(+) levels and upon acidification of the extracellular medium (PubMed:21653227, PubMed:22431633). The homodimer has very low potassium channel activity, when expressed in heterologous systems, and can function as weakly inward rectifying potassium channel (PubMed:15820677, PubMed:21653227, PubMed:22431633, PubMed:23169818, PubMed:25001086, PubMed:8605869, PubMed:8978667). Channel activity is modulated by activation of serotonin receptors (By similarity). Heterodimeric channels containing KCNK1 and KCNK2 have much higher activity, and may represent the predominant form in astrocytes (By similarity). Heterodimeric channels containing KCNK1 and KCNK3 or KCNK9 have much higher activity (PubMed:23169818). Heterodimeric channels formed by KCNK1 and KCNK9 may contribute to halothane-sensitive currents (PubMed:23169818). Mediates outward rectifying potassium currents in dentate gyrus granule cells and contributes to the regulation of their resting membrane potential (By similarity). Contributes to the regulation of action potential firing in dentate gyrus granule cells and down-regulates their intrinsic excitability (By similarity). In astrocytes, the heterodimer formed by KCNK1 and KCNK2 is required for rapid glutamate release in response to activation of G-protein coupled receptors, such as F2R and CNR1 (By similarity). Required for normal ion and water transport in the kidney (By similarity). Contributes to the regulation of the resting membrane potential of pancreatic beta cells (By similarity). The low channel activity of homodimeric KCNK1 may be due to sumoylation (PubMed:15820677, PubMed:20498050, PubMed:23169818). The low channel activity may be due to rapid internalization from the cell membrane and retention in recycling endosomes (PubMed:19959478). Permeable to monovalent cations with ion selectivity for K(+) > Rb(+) >> NH4(+) >> Cs(+) = Na(+) = Li(+)","subcellular_location":"Cell membrane; Recycling endosome; Synaptic cell membrane; Cytoplasmic vesicle; Perikaryon; Cell projection, dendrite; Cell projection; Apical cell membrane","url":"https://www.uniprot.org/uniprotkb/O00180/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KCNK1","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/KCNK1","total_profiled":1310},"omim":[{"mim_id":"613655","title":"POTASSIUM CHANNEL, SUBFAMILY K, MEMBER 18; KCNK18","url":"https://www.omim.org/entry/613655"},{"mim_id":"611741","title":"ACID-SENSING ION CHANNEL, SUBUNIT 3; ASIC3","url":"https://www.omim.org/entry/611741"},{"mim_id":"611549","title":"SODIUM LEAK CHANNEL, NONSELECTIVE; NALCN","url":"https://www.omim.org/entry/611549"},{"mim_id":"607370","title":"POTASSIUM CHANNEL, SUBFAMILY K, MEMBER 17; KCNK17","url":"https://www.omim.org/entry/607370"},{"mim_id":"606554","title":"EPISODIC ATAXIA, TYPE 3; EA3","url":"https://www.omim.org/entry/606554"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":108.6},{"tissue":"choroid plexus","ntpm":70.0}],"url":"https://www.proteinatlas.org/search/KCNK1"},"hgnc":{"alias_symbol":["K2p1.1","DPK","TWIK-1"],"prev_symbol":[]},"alphafold":{"accession":"O00180","domains":[{"cath_id":"-","chopping":"15-88","consensus_level":"medium","plddt":92.0632,"start":15,"end":88},{"cath_id":"1.10.287.70","chopping":"99-281","consensus_level":"medium","plddt":91.8478,"start":99,"end":281}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O00180","model_url":"https://alphafold.ebi.ac.uk/files/AF-O00180-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O00180-F1-predicted_aligned_error_v6.png","plddt_mean":82.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KCNK1","jax_strain_url":"https://www.jax.org/strain/search?query=KCNK1"},"sequence":{"accession":"O00180","fasta_url":"https://rest.uniprot.org/uniprotkb/O00180.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O00180/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O00180"}},"corpus_meta":[{"pmid":"8605869","id":"PMC_8605869","title":"TWIK-1, 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Ba2+, quinine, and quinidine.\",\n      \"method\": \"Heterologous expression in Xenopus oocytes, patch-clamp electrophysiology, pharmacology\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — original channel characterization with in vitro electrophysiology, multiple pharmacological probes, and mutagenesis-level mechanistic detail; foundational paper >400 citations\",\n      \"pmids\": [\"8605869\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"TWIK-1 subunits self-associate into homodimers via an interchain disulfide bridge involving Cys69 in the extracellular M1P1 linker loop; mutation of C69 to serine abolishes functional K+ channel expression.\",\n      \"method\": \"Biochemical dimerization assay, site-directed mutagenesis (C69S), functional expression in Xenopus oocytes\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis + biochemical assay with direct functional consequence; replicated by multiple subsequent studies; >140 citations\",\n      \"pmids\": [\"8978667\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Mouse TWIK-1 (mTWIK-1) has an apparent native molecular weight of ~81 kDa; treatment with reducing agent reveals a ~40 kDa form, confirming native dimerization via a disulfide bridge; mTWIK-1 currents in oocytes are K+-selective, instantaneous, and weakly inward-rectifying; blocked by Ba2+ and quinine; decreased by PKC and increased by internal acidification.\",\n      \"method\": \"Western blot with/without reducing agent, heterologous expression in Xenopus oocytes, electrophysiology\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — biochemical confirmation of disulfide-linked dimer in native brain tissue plus electrophysiology; independent replication of human TWIK-1 findings\",\n      \"pmids\": [\"9013852\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"TWIK-1 contributes to the background passive K+ conductance of mature hippocampal astrocytes; cloned rat TWIK-1 in CHO cells conducts Cs+ currents (PCs/PK = 0.10); astrocytic passive conductance is inhibited ~58% by 200 µM quinine (IC50 for TWIK-1 = 85 µM); TWIK-1 protein co-localizes with astrocytic markers GLAST and GFAP in hippocampal stratum radiatum.\",\n      \"method\": \"Patch-clamp electrophysiology in CHO cells and hippocampal slices, pharmacology, immunocytochemistry\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (electrophysiology, pharmacology, immunolocalization) in native tissue and heterologous system; >140 citations\",\n      \"pmids\": [\"19571146\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"TWIK-1 changes ion selectivity from K+-selective to Na+-permeable under subphysiological extracellular K+ (hypokalemia), conducting inward leak Na+ currents; Thr118 within the selectivity filter sequence TxGYG is required for this altered selectivity; TWIK-1 knockdown in human primary cardiac myocytes eliminates paradoxical depolarization in low [K+]o.\",\n      \"method\": \"Patch-clamp electrophysiology, site-directed mutagenesis (T118 variants), siRNA knockdown in human spherical primary cardiac myocytes, ectopic expression in HL-1 and CHO cells\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis identifies critical residue; loss-of-function in human primary cells confirms physiological role; multiple orthogonal approaches\",\n      \"pmids\": [\"21653227\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"TWIK-1 is primarily localized in intracellular cytoplasmic compartments (~55%) and mildly hydrophobic internal compartment fractions (~41%), with only ~5% at the plasma membrane of hippocampal astrocytes, limiting its contribution to whole-cell passive conductance; TWIK-1 knockout astrocytes show more negative resting potential and reduced inward rectification and Cs+ permeability without global change in passive conductance.\",\n      \"method\": \"Subcellular fractionation, TWIK-1 knockout mice, whole-cell patch-clamp in hippocampal slices\",\n      \"journal\": \"Frontiers in cellular neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — fractionation plus genetic knockout with defined electrophysiological phenotype; multiple orthogonal methods\",\n      \"pmids\": [\"24368895\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Native TWIK-1 forms a functional heterodimeric channel with TREK-1 at the plasma membrane of astrocytes via a disulfide bridge between Cys69 of TWIK-1 and Cys93 of TREK-1; surface expression of TWIK-1 and TREK-1 are interdependent; TWIK-1/TREK-1 heterodimers mediate astrocytic passive conductance and cannabinoid-induced glutamate release from astrocytes.\",\n      \"method\": \"Co-immunoprecipitation, gene silencing (shRNA), disulfide bond identification by mutagenesis, surface biotinylation, patch-clamp electrophysiology in native astrocytes\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — reciprocal Co-IP, mutagenesis identifying disulfide bond, gene silencing with functional readouts; >120 citations\",\n      \"pmids\": [\"24496152\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TWIK-1 is expressed and localized mainly in soma and proximal dendrites of dentate gyrus granule cells (DGGCs); gene silencing of TWIK-1 reduces outwardly rectifying K+ current density, causes depolarizing shift in resting membrane potential, enhances firing rate, increases EPSP amplitude, and impairs EPSP-spike coupling in perforant path synaptic transmission.\",\n      \"method\": \"shRNA gene silencing, whole-cell patch-clamp in mouse hippocampal DGGCs, immunofluorescence\",\n      \"journal\": \"Molecular brain\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean gene silencing with multiple defined electrophysiological phenotypes plus localization data\",\n      \"pmids\": [\"25406588\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Lipid tails from both membrane leaflets can occupy fenestrations in the TWIK-1 pore and partially penetrate into the inner pore cavity; there is an inverse correlation between lipid tail occupancy and water content within the hydrophobic barrier, but dewetting (pore closure) also occurs in the absence of lipid tails, indicating that hydrophobic side chains lining the pore cavity are the primary determinant of the hydrophobic barrier.\",\n      \"method\": \"Molecular dynamics (MD) simulations based on TWIK-1 crystal structure\",\n      \"journal\": \"Channels (Austin, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 4 — computational MD study; no direct experimental mutagenesis validation in this paper\",\n      \"pmids\": [\"25487004\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"mGluR3 activation (Gi/Go-coupled) triggers translocation of TWIK-1 channels from cytoplasm to the plasma membrane of hippocampal astrocytes via a Rab-mediated recycling endosome trafficking pathway; this membrane recruitment is associated with membrane depolarization and enhanced NH4+ uptake (~30% potentiation), a process absent in TWIK-1 knockout astrocytes.\",\n      \"method\": \"Live-cell imaging of TWIK-1 trafficking, electrophysiology (VM response to NH4Cl), TWIK-1 knockout comparison, pharmacological mGluR3 activation\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO controls plus imaging of translocation plus functional electrophysiology; single lab\",\n      \"pmids\": [\"26553349\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"KCNK1 overexpression inhibits RANKL-induced osteoclast differentiation by attenuating Ca2+ oscillations and suppressing JNK activation and NFATc1 expression; conversely, KCNK1 knockdown enhances osteoclastogenesis, JNK activation and NFATc1 expression, placing KCNK1 as a negative regulator upstream of the Ca2+/JNK-NFATc1 axis.\",\n      \"method\": \"Overexpression and siRNA knockdown of KCNK1 in osteoclast precursors, Ca2+ imaging, immunoblotting for JNK/NFATc1, osteoclast differentiation assay\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — bidirectional genetic manipulation (OE and KD) with multiple molecular readouts; single lab\",\n      \"pmids\": [\"26208638\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"MD simulations reveal that the TWIK-1 selectivity filter (SF) diverges from canonical K+ channel structure due to non-conserved residues T118 (pore domain 1) and L228 (pore domain 2); T118 behavior is linked to dynamic selectivity enabling Na+ influx at subphysiological K+ concentrations, consistent with inactivation-like SF gating.\",\n      \"method\": \"Molecular dynamics simulations (~1 µs cumulative) based on TWIK-1 crystal structure\",\n      \"journal\": \"Biophysical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 4 — computational only, but consistent with experimental mutagenesis data from other papers (T118)\",\n      \"pmids\": [\"27558721\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"TWIK-1 is required for normal heart rate and atrial morphology in zebrafish; knockdown of kcnk1a or kcnk1b causes bradycardia and atrial dilation; the phenotype is partially rescued by wild-type human KCNK1 mRNA but not by a dominant-negative variant; zebrafish and human TWIK-1 channels show predominant localization in the endosomal compartment and produce K+ currents sensitive to external K+ concentration and acidic pH.\",\n      \"method\": \"Morpholino knockdown in zebrafish, mRNA rescue, two-electrode voltage-clamp in Xenopus oocytes, cellular localization by microscopy\",\n      \"journal\": \"Journal of molecular and cellular cardiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic knockdown + mRNA rescue in vertebrate model with defined cardiac phenotypes + electrophysiology; multiple orthogonal approaches\",\n      \"pmids\": [\"27103460\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TWIK-1 associates with TASK-3 to form a heterodimeric channel in dentate gyrus granule cells (DGGCs) and in COS-7 cells; TWIK-1/TASK-3 heterodimers display outwardly rectifying currents and contribute to intrinsic excitability of DGGCs; neurotensin-neurotensin receptor 1 (NT-NTSR1) signaling depolarizes DGGCs by inhibiting TWIK-1/TASK-3 heterodimeric channels.\",\n      \"method\": \"Co-immunoprecipitation in hippocampal tissue and COS-7 cells, shRNA gene silencing, patch-clamp electrophysiology in DGGCs, pharmacological activation of NTSR1\",\n      \"journal\": \"Experimental & molecular medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP in native tissue and heterologous system, gene silencing with defined electrophysiological phenotype, receptor-mediated pathway placement\",\n      \"pmids\": [\"30416196\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The low intrinsic functional activity of TWIK-1 is dominated by instability of the conductive conformation of the selectivity filter (SF gate) in the presence of K+; Rb+, NH4+, and Cs+ promote a pH-dependent activated SF conformation; intracellular K+ potently inhibits TWIK-1 Rb+ currents (IC50 = 2.8 mM); voltage-dependent activation of TWIK-1 requires non-physiological strong depolarization.\",\n      \"method\": \"Patch-clamp electrophysiology with various permeant ions, systematic evaluation of proposed silencing mechanisms (sumoylation, internalization, hydrophobic barrier) using mutagenesis and pharmacology\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic in vitro electrophysiology with multiple ion species, mutagenesis, and pharmacological dissection of competing mechanisms\",\n      \"pmids\": [\"31806709\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Nuclear receptor CAR directly binds a 97-bp response element (-2441/-2345) within the Kcnk1 promoter to drive male-specific transcription of Kcnk1 in mouse liver upon phenobarbital treatment; this activation requires the pituitary gland (abrogated by hypophysectomy); Kcnk1 knockout mice show enhanced phenobarbital-induced hepatic hyperplasia, establishing KCNK1 as a CAR-induced anti-hyperplasia factor.\",\n      \"method\": \"ChIP (CAR binding to Kcnk1 promoter), hypophysectomy experiment, Kcnk1 knockout mice with phenobarbital treatment, promoter reporter assay\",\n      \"journal\": \"Toxicological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP identifies direct transcriptional mechanism; KO mice provide functional evidence; single lab\",\n      \"pmids\": [\"23291559\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Spadin (a TREK-1 inhibitor) dramatically reduces astrocytic passive conductance in brain slices; gene silencing demonstrates that spadin-sensitive currents are mediated by TWIK-1/TREK-1 heterodimeric channels in cultured astrocytes and hippocampal astrocytes from brain slices.\",\n      \"method\": \"Patch-clamp electrophysiology in brain slices and cultured astrocytes, shRNA gene silencing of TWIK-1 and/or TREK-1, pharmacology with spadin\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — pharmacology combined with bidirectional gene silencing; confirms TWIK-1/TREK-1 heterodimer as passive conductance machinery\",\n      \"pmids\": [\"33348878\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"AEG-1 (MTDH) binds directly to TWIK-1 mRNA and stabilizes it, thereby regulating TWIK-1 protein expression and TWIK-1-mediated K+ currents in astrocytes; AEG-1 knockdown downregulates TWIK-1 mRNA and protein, and reduces TWIK-1-mediated currents.\",\n      \"method\": \"RNA immunoprecipitation (AEG-1 binding to TWIK-1 mRNA), shRNA knockdown, qPCR, immunocytochemistry, patch-clamp electrophysiology\",\n      \"journal\": \"Brain sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — RNA-IP plus functional electrophysiology; single lab\",\n      \"pmids\": [\"33440655\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"In the dorsal spinal horn, ciRNA-Kat6b acts as a sponge for miRNA-26a; nerve injury downregulates ciRNA-Kat6b, increasing free miRNA-26a which binds the 3'UTR of Kcnk1 mRNA and promotes its degradation, reducing KCNK1 protein and contributing to neuropathic pain; rescuing ciRNA-Kat6b restores KCNK1 and alleviates pain hypersensitivity.\",\n      \"method\": \"Luciferase reporter assay (miRNA-26a targeting Kcnk1 3'UTR), RNA immunoprecipitation (ciRNA-Kat6b/miRNA-26a interaction), Western blot, immunofluorescence, behavioral pain assays, CCI neuropathic pain model\",\n      \"journal\": \"CNS neuroscience & therapeutics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — luciferase validation of miRNA-mRNA interaction + in vivo rescue experiments; single lab\",\n      \"pmids\": [\"37144575\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"KCNK1 promotes glycolysis and lactate production in breast cancer cells by directly binding to and activating LDHA; elevated LDHA activity promotes H3K18 lactylation and transcription of downstream genes including LDHA itself (positive feedback); this axis reduces tumor cell stiffness and adhesion, facilitating proliferation, invasion, and metastasis.\",\n      \"method\": \"Co-immunoprecipitation (KCNK1-LDHA binding), glycolysis/lactate assays, histone lactylation analysis (H3K18), in vitro invasion/proliferation assays, in vivo xenograft models\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — Co-IP identifies direct KCNK1-LDHA interaction; functional in vitro and in vivo readouts; single lab; unusual non-channel mechanism\",\n      \"pmids\": [\"38905316\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"siRNA knockdown of KCNK1 in IPAH-PASMCs causes membrane depolarization, decreases cytosolic Ca2+, and suppresses proliferation and migration; elevated KCNK1 expression in IPAH-PASMCs facilitates proliferation and migration via enhanced Ca2+ signaling and elevated JNK phosphorylation.\",\n      \"method\": \"siRNA knockdown of KCNK1, patch-clamp electrophysiology, Ca2+ imaging, proliferation/migration assays, Western blot for pJNK, in IPAH patient-derived PASMCs and experimental PH animal models\",\n      \"journal\": \"Frontiers in cardiovascular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — siRNA knockdown with multiple molecular and functional readouts; validated in multiple animal models; single lab\",\n      \"pmids\": [\"38410243\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"TWIK-1 (KCNK1) mediates K+ currents responsible for background passive conductance in astrocytes; TWIK-1 deficiency (exon 1 CRISPR-Cas9 knockout) increases susceptibility to kainic acid-induced seizures, demonstrating that TWIK-1-mediated astrocytic passive conductance has a neuroprotective role in seizure threshold.\",\n      \"method\": \"CRISPR-Cas9 exon 1 knockout mice, patch-clamp electrophysiology in astrocytes, kainic acid seizure model, comparison with exon 2-deleted (partial) KO\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic KO with defined electrophysiological and behavioral phenotypes; resolves prior KO artifact\",\n      \"pmids\": [\"39811670\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KCNK1/TWIK-1 is a homodimeric (via C69 disulfide) or heterodimeric (with TREK-1 via C69–C93 disulfide, or with TASK-3) two-pore domain background K+ channel that is constitutively retained in intracellular compartments and trafficked to the plasma membrane by mGluR3/Rab-dependent signaling; at the surface its selectivity filter gate is intrinsically unstable in physiological K+, but switches to Na+ permeability under hypokalemia (requiring selectivity filter residue T118); it sets resting membrane potential in hippocampal astrocytes (where its passive conductance guards against seizures) and dentate granule neurons, is regulated transcriptionally by nuclear receptor CAR and post-transcriptionally by AEG-1/miRNA-26a, and in non-channel contexts can directly bind and activate LDHA to promote histone lactylation in cancer cells.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"KCNK1 (TWIK-1) is a two-pore-domain potassium channel that assembles as a disulfide-linked homodimer (via Cys69) or as heterodimers with TREK-1 (via Cys69–Cys93) or TASK-3, and sets resting membrane potential in hippocampal astrocytes and dentate granule neurons [PMID:8978667, PMID:24496152, PMID:30416196, PMID:25406588]. The channel is constitutively retained in intracellular compartments with only ~5% at the plasma membrane, and surface delivery is stimulated by mGluR3/Gi–Rab-dependent trafficking from recycling endosomes [PMID:24368895, PMID:26553349]. Its selectivity filter, which contains the non-canonical residue Thr118, is intrinsically unstable in physiological K+, accounting for low basal activity, but switches to Na+ permeability under hypokalemic conditions, contributing to paradoxical depolarization in cardiac myocytes [PMID:31806709, PMID:21653227]. Astrocytic TWIK-1-mediated passive conductance is neuroprotective, as TWIK-1 knockout mice show increased seizure susceptibility to kainic acid [PMID:39811670].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Establishing KCNK1 as the founding two-pore-domain K+ channel resolved its basic biophysical identity: a time-independent, weakly inward-rectifying K+ conductance modulated by PKC and intracellular pH, with a defined pharmacological profile (Ba2+, quinine blockade).\",\n      \"evidence\": \"Heterologous expression and patch-clamp in Xenopus oocytes\",\n      \"pmids\": [\"8605869\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological context unknown\", \"Mechanism of PKC up-regulation not delineated\", \"Gating mechanism at molecular level unresolved\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Demonstrating that TWIK-1 assembles as a disulfide-linked homodimer via Cys69 established the structural basis for channel formation and showed that dimerization is required for function.\",\n      \"evidence\": \"Site-directed mutagenesis (C69S) and biochemical dimerization assay in oocytes, confirmed by Western blot of native mouse brain protein\",\n      \"pmids\": [\"8978667\", \"9013852\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether heterodimers form in vivo unknown\", \"Structure beyond dimerization interface unresolved\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identifying TWIK-1 as a major contributor to background passive conductance in hippocampal astrocytes placed the channel in a defined physiological context and explained its role in setting astrocytic resting membrane potential.\",\n      \"evidence\": \"Patch-clamp in CHO cells and hippocampal slices with quinine pharmacology and immunocytochemistry\",\n      \"pmids\": [\"19571146\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contribution versus other K2P channels not fully dissected\", \"Mechanism of intracellular retention unclear\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Discovering that TWIK-1 switches from K+- to Na+-permeable under hypokalemia, dependent on selectivity filter residue Thr118, revealed a dynamic ion selectivity mechanism with direct pathophysiological relevance for cardiac depolarization.\",\n      \"evidence\": \"Site-directed mutagenesis of T118, siRNA knockdown in human primary cardiac myocytes, patch-clamp\",\n      \"pmids\": [\"21653227\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of selectivity switch not experimentally determined\", \"In vivo cardiac phenotype in mammals not established\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Subcellular fractionation and knockout studies showed that ~95% of TWIK-1 is retained intracellularly, explaining its low functional surface activity and reconciling the discrepancy between high transcript abundance and modest whole-cell current.\",\n      \"evidence\": \"Subcellular fractionation of astrocytes, TWIK-1 knockout mice with electrophysiology\",\n      \"pmids\": [\"24368895\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular machinery mediating intracellular retention not identified\", \"Whether retention is constitutive or dynamically regulated was unclear\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identification of TWIK-1/TREK-1 heterodimers linked by a Cys69–Cys93 disulfide bridge established that TWIK-1 forms obligate heteromeric channels at the astrocyte surface, mediating passive conductance and cannabinoid-induced glutamate release, and later confirmed as spadin-sensitive channels.\",\n      \"evidence\": \"Reciprocal Co-IP, mutagenesis, surface biotinylation, gene silencing, patch-clamp in astrocytes; pharmacology with spadin\",\n      \"pmids\": [\"24496152\", \"33348878\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and structure of heterodimer not resolved\", \"Whether TWIK-1 homodimers also contribute at the surface remains debated\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Gene silencing in dentate granule cells revealed that TWIK-1 carries outwardly rectifying currents that maintain hyperpolarized resting potential and modulate synaptic integration at the perforant path, establishing a neuronal (not only glial) role.\",\n      \"evidence\": \"shRNA in mouse hippocampal DGGCs with patch-clamp electrophysiology\",\n      \"pmids\": [\"25406588\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the neuronal current is homodimeric or heterodimeric unresolved at this point\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Demonstrating that mGluR3 activation drives Rab-dependent translocation of TWIK-1 from cytoplasm to plasma membrane identified a receptor-mediated trafficking mechanism that dynamically regulates astrocytic TWIK-1 surface expression.\",\n      \"evidence\": \"Live-cell imaging, electrophysiology, pharmacological mGluR3 activation, TWIK-1 KO comparison in astrocytes\",\n      \"pmids\": [\"26553349\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific Rab isoform not identified\", \"Signaling intermediates between Gi/Go and Rab machinery not mapped\", \"Single-lab finding\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Zebrafish knockdown of kcnk1a/b causing bradycardia and atrial dilation, rescuable by human KCNK1, established a conserved cardiac pacemaking role and confirmed predominant endosomal localization across species.\",\n      \"evidence\": \"Morpholino knockdown in zebrafish with human mRNA rescue, electrophysiology in oocytes\",\n      \"pmids\": [\"27103460\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mammalian in vivo cardiac phenotype not confirmed\", \"Channel composition in cardiomyocytes (homo- vs heterodimer) unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identification of TWIK-1/TASK-3 heterodimers in dentate granule cells, inhibited by neurotensin-NTSR1 signaling, resolved the composition of the neuronal TWIK-1 channel and linked it to a neuromodulatory pathway.\",\n      \"evidence\": \"Reciprocal Co-IP in hippocampal tissue and COS-7 cells, shRNA, patch-clamp, NTSR1 pharmacology\",\n      \"pmids\": [\"30416196\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Proportion of TWIK-1 in homodimer vs TASK-3 heterodimer in neurons not quantified\", \"Downstream behavioral consequences of NTSR1-mediated inhibition unexplored\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Systematic electrophysiological dissection showed that the primary mechanism underlying TWIK-1's low basal activity is instability of the selectivity filter conductive state in K+, rather than previously proposed sumoylation or internalization, resolving a long-standing debate.\",\n      \"evidence\": \"Patch-clamp with multiple permeant ions (Rb+, NH4+, Cs+), mutagenesis, pharmacology\",\n      \"pmids\": [\"31806709\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural dynamics of SF gating not captured experimentally\", \"Whether SF instability is modulated by heterodimer partners unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"CRISPR-Cas9 full knockout of TWIK-1 demonstrated that astrocytic TWIK-1 passive conductance is neuroprotective, as KO mice show heightened seizure susceptibility to kainic acid, resolving a prior artifact from partial exon-2 deletion.\",\n      \"evidence\": \"Exon 1 CRISPR-Cas9 KO mice, patch-clamp in astrocytes, kainic acid seizure model\",\n      \"pmids\": [\"39811670\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether seizure phenotype is astrocyte-autonomous vs includes neuronal TWIK-1 loss not distinguished\", \"Rescue experiment not performed\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"An unexpected non-channel function was reported: KCNK1 directly binds and activates LDHA, promoting glycolysis, histone H3K18 lactylation, and a positive-feedback transcriptional loop that drives breast cancer proliferation and metastasis.\",\n      \"evidence\": \"Co-IP of KCNK1-LDHA, glycolysis/lactate assays, histone lactylation analysis, xenograft models\",\n      \"pmids\": [\"38905316\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether this function requires channel activity is untested\", \"No independent replication\", \"Structural basis of KCNK1-LDHA interaction unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis of selectivity filter gating and the Na+-permeability switch, how heterodimer partner choice (TREK-1 vs TASK-3) is determined in different cell types, the molecular machinery mediating constitutive intracellular retention, and whether the non-channel LDHA-activating function is physiologically relevant beyond cancer.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No high-resolution structure of full-length TWIK-1 in active/inactive states\", \"In vivo mammalian cardiac phenotype not established\", \"Channel-independent functions lack independent replication\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 3, 4, 6, 7, 13, 14, 21]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [19]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 5, 6, 9]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [5, 9, 12]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [3, 7, 13, 21]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 4, 14]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [9, 10, 13]}\n    ],\n    \"complexes\": [\n      \"TWIK-1 homodimer\",\n      \"TWIK-1/TREK-1 heterodimer\",\n      \"TWIK-1/TASK-3 heterodimer\"\n    ],\n    \"partners\": [\n      \"KCNK2\",\n      \"KCNK9\",\n      \"LDHA\",\n      \"MTDH\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}