{"gene":"KCNK6","run_date":"2026-06-10T02:59:49","timeline":{"discoveries":[{"year":1999,"finding":"TWIK-2 (KCNK6) was cloned from human brain cDNA and shown to function as a non-inactivating weak inward rectifier K+ channel with two pore-forming domains; it is inhibited by intracellular but not extracellular acidification, and is pharmacologically distinct from TWIK-1 in its responses to quinidine, quinine, and barium when expressed heterologously in Xenopus oocytes.","method":"Heterologous expression in Xenopus oocytes, electrophysiology, pharmacological profiling","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct electrophysiological characterization in heterologous expression system with pharmacological profiling; foundational characterization paper replicated by subsequent studies","pmids":["10075682"],"is_preprint":false},{"year":2000,"finding":"Human and rat TWIK-2 expressed in COS cells display outward rectification in physiological K+ gradient and mild inward rectification in symmetrical K+; currents inactivate at depolarized potentials with temperature-sensitive kinetics. Cysteine 53 in the M1P1 external loop is required for functional expression but not for subunit self-assembly. TWIK-2 has extremely low single-channel conductance.","method":"Heterologous expression in COS cells, whole-cell and single-channel patch clamp, site-directed mutagenesis (C53 mutant), temperature-dependent kinetic analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro electrophysiology with mutagenesis and multiple orthogonal methods confirming inactivation and rectification as intrinsic properties; replicated across human and rat isoforms","pmids":["10887187"],"is_preprint":false},{"year":2009,"finding":"Rat TWIK-2 cloned from the middle cerebral artery and expressed in CHO cells shows relatively linear currents at physiological K+ concentrations, mild inward rectification in symmetrical K+, insensitivity to TEA, 4-aminopyridine, and glibenclamide, inhibition by Ba2+ (IC50 ~80 µM), and 60% enhancement of activity by 100 µM arachidonic acid.","method":"Cloning from rat middle cerebral artery, heterologous expression in CHO cells, whole-cell patch clamp, pharmacological profiling","journal":"Experimental biology and medicine","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — direct electrophysiology in heterologous system but single lab, single study; arachidonic acid modulation is a novel finding not independently replicated","pmids":["19934370"],"is_preprint":false},{"year":2014,"finding":"TWIK-2 knockout mice develop pulmonary hypertension and pulmonary vascular remodeling by 20 weeks of age. Pulmonary artery branches from knockout mice show enhanced contractile response to thromboxane A2 mimetic U46619, which is abolished by the Rho-kinase inhibitor Y27632. Treatment with Rho-kinase inhibitor fasudil abolishes hypertension development, placing TWIK-2 upstream of Rho-kinase in vascular tone regulation.","method":"TWIK-2 knockout mouse model, hemodynamic measurements (right ventricular systolic pressure), vascular morphometry, ex vivo vasoconstriction assay, pharmacological rescue with Rho-kinase inhibitor (fasudil, Y27632)","journal":"Hypertension","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with defined hemodynamic and structural phenotype, pharmacological epistasis with Rho-kinase inhibitor rescue demonstrating pathway placement","pmids":["25245387"],"is_preprint":false},{"year":2004,"finding":"Twik-2 protein is expressed in the mouse cochlea, specifically localised predominantly within the stria vascularis as determined by immunohistochemistry and immunoblot, suggesting a role in potassium ion recycling into the endolymph. However, no causative mutations were found in KCNK6 in DFNA4 hearing loss families.","method":"RT-PCR, immunoblot (35 kDa band), immunohistochemistry of cochlear sections","journal":"Journal of neuroscience research","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct localization by immunohistochemistry and protein detection, single lab; functional implication is inferential, no functional KO or electrophysiology","pmids":["14689445"],"is_preprint":false},{"year":2024,"finding":"METTL3-mediated m6A modification increases KCNK6 mRNA stability in a YTHDF2-dependent manner; histone lactylation activates transcription of YTHDF2/Kcnk6. Loss of Kcnk6 in macrophages inhibits NLRP3 inflammasome activation and reduces inflammatory factors, while Kcnk6 accelerates potassium channel activity to induce NLRP3 inflammasome activation.","method":"Kcnk6 knockout mouse model, bone marrow-derived macrophages, AOM/DSS colitis-cancer model, in vitro cell lines (HCT116, Caco2), m6A modification assays, YTHDF2-binding studies, histone lactylation analysis","journal":"International reviews of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO with defined inflammatory phenotype, m6A/YTHDF2 mechanism supported by multiple assays in single lab; some mechanistic claims rely on abstract-level description without full methodological detail","pmids":["39269733"],"is_preprint":false},{"year":2025,"finding":"Cryo-EM structure of human TWIK-2 at 2.85 Å resolution reveals a unique 'up' conformation of Tyr111 in the selectivity filter and a SF1-P1 pocket behind the filter. Acyl chains occupy lateral fenestrations within the transmembrane region connecting the central cavity to the lipid membrane. Pimozide inhibits TWIK-2 by displacing acyl chains and binding below the selectivity filter to block ion conduction, potentially accessing its site via the membrane.","method":"Cryo-EM structure determination, electrophysiology (pimozide inhibition assay), structural comparison with other K2P channels","journal":"bioRxiv","confidence":"High","confidence_rationale":"Tier 1 / Moderate — high-resolution cryo-EM structure with pimozide-bound complex and electrophysiological validation; preprint not yet peer-reviewed but structural evidence is direct","pmids":["bio_10.1101_2025.02.24.639991"],"is_preprint":true},{"year":2025,"finding":"Cryo-EM structures of human TWIK-2 (K2P6.1) in nanodisc and detergent environments reveal an unusual SF1 conformation and a 'lipid plug' consisting of two-chain lipids in the channel cavity, with each lipid occupying two distinct binding sites (upper and lower fenestration legs). An R257A mutant that increases channel function alters lipid plug position, indicating R257 is key to lipid binding. A plasma-membrane-targeting mutant yielded both plugged and unplugged forms, suggesting lipid plug occupancy renders TWIK channels inactive and plug removal is required for ion-permeable pore formation.","method":"Cryo-EM structure determination (nanodisc and detergent conditions), site-directed mutagenesis (R257A and plasma-membrane-targeting mutant), structural comparison of plugged vs. unplugged conformations","journal":"bioRxiv","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct cryo-EM structures with mutagenesis validating lipid plug mechanism; preprint not yet peer-reviewed but uses multiple structural conditions and mutants as orthogonal evidence","pmids":["bio_10.1101_2025.06.11.659167"],"is_preprint":true},{"year":2026,"finding":"Cryo-EM structure of human TWIK-2 at 3.7 Å reveals conserved and distinctive structural features. Gating in TWIK-2 is voltage-dependent and insensitive to extracellular pH changes. Site-directed mutagenesis identified key residues influencing TWIK-2 activity, and lipid-mediated regulation is implicated as a mechanism of TWIK-2 modulation.","method":"Single particle cryo-EM (3.7 Å), automated whole-cell patch clamp, site-directed mutagenesis, high-throughput small molecule screening","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — peer-reviewed cryo-EM structure combined with mutagenesis and automated electrophysiology; voltage-dependence and pH-insensitivity established by direct functional assay","pmids":["41617707"],"is_preprint":false},{"year":2011,"finding":"Dexamethasone upregulates TWIK-2 (KCNK6) mRNA expression in human periodontal ligament fibroblasts in a dose- and time-dependent manner; this effect is abolished by a glucocorticoid receptor antagonist, indicating glucocorticoid receptor-mediated transcriptional regulation of TWIK-2.","method":"RT-PCR of mRNA expression in cultured human PDL fibroblasts, glucocorticoid receptor antagonist pharmacology","journal":"In vitro cellular & developmental biology. Animal","confidence":"Low","confidence_rationale":"Tier 3 / Weak — mRNA-level upregulation with pharmacological receptor blockade; no protein-level, electrophysiological, or functional downstream validation; single lab","pmids":["21359819"],"is_preprint":false}],"current_model":"TWIK-2 (KCNK6) is a two-pore domain K+ channel that forms a homodimer with extremely low conductance, voltage-dependent gating that is insensitive to extracellular pH, and inactivation at depolarized potentials; its cryo-EM structure reveals a unique SF1 conformation, a lipid plug in the channel cavity that renders it inactive, and lateral fenestrations through which lipids and hydrophobic drugs (including the inhibitor pimozide) access a binding site below the selectivity filter; functionally, TWIK-2 promotes K+ efflux to activate the NLRP3 inflammasome in macrophages (regulated transcriptionally by METTL3-mediated m6A modification via YTHDF2 and histone lactylation), and its loss in mice causes pulmonary hypertension through a Rho-kinase-dependent mechanism."},"narrative":{"mechanistic_narrative":"KCNK6 (TWIK-2/K2P6.1) is a two-pore-domain potassium channel that forms a homodimer with extremely low single-channel conductance and contributes to background K+ flux that shapes cellular excitability and tone [PMID:10075682, PMID:10887187]. Heterologous expression established it as a weak inward rectifier that inactivates at depolarized potentials with temperature-sensitive kinetics, is inhibited by intracellular but not extracellular acidification, and depends on an external-loop cysteine (C53) for functional surface expression [PMID:10075682, PMID:10887187]; subsequent functional work confirmed voltage-dependent gating that is insensitive to extracellular pH [PMID:41617707]. Cryo-EM structures of the human channel reveal a distinctive selectivity-filter (SF1) conformation and a 'lipid plug' of two-chain lipids occupying the central cavity and lateral fenestrations, which renders the channel inactive; an R257A mutation repositions this plug and increases channel function, and removal of the plug is required to form an ion-permeable pore [PMID:bio_10.1101_2025.06.11.659167]. These fenestrations also serve as the access route for hydrophobic inhibitors: the antipsychotic pimozide displaces the acyl chains and binds below the selectivity filter to block ion conduction [PMID:bio_10.1101_2025.02.24.639991]. Physiologically, TWIK-2 promotes K+ efflux that activates the NLRP3 inflammasome in macrophages, with its expression controlled by METTL3-mediated m6A modification acting through YTHDF2 and by histone lactylation [PMID:39269733], and its genetic loss in mice causes pulmonary hypertension and vascular remodeling through a Rho-kinase-dependent mechanism [PMID:25245387].","teleology":[{"year":1999,"claim":"Established the molecular identity and basic biophysical class of KCNK6, defining it as a two-pore-domain weak inward rectifier K+ channel distinct from TWIK-1.","evidence":"Cloning from human brain cDNA and electrophysiology/pharmacological profiling in Xenopus oocytes","pmids":["10075682"],"confidence":"High","gaps":["Native cell type and physiological function not addressed","No structural basis for gating","pH sensitivity restricted to heterologous context"]},{"year":2000,"claim":"Defined inactivation, rectification, and low conductance as intrinsic channel properties and identified a residue (C53) required for functional expression but not subunit assembly.","evidence":"Whole-cell and single-channel patch clamp with site-directed mutagenesis in COS cells across human and rat isoforms","pmids":["10887187"],"confidence":"High","gaps":["Mechanism linking C53 to surface trafficking unresolved","Physiological role still unknown","Endogenous modulators not identified"]},{"year":2004,"claim":"Provided the first tissue localization, placing TWIK-2 protein in the cochlear stria vascularis and implicating it in potassium recycling, while excluding it as a DFNA4 disease gene.","evidence":"RT-PCR, immunoblot, and immunohistochemistry of mouse cochlea plus mutation screening of DFNA4 families","pmids":["14689445"],"confidence":"Medium","gaps":["Functional contribution to endolymph K+ inferential, no KO or electrophysiology in cochlea","No causative human disease mutation found"]},{"year":2009,"claim":"Extended characterization to vascular tissue, showing arachidonic acid enhances TWIK-2 currents and defining its pharmacological insensitivity profile.","evidence":"Cloning from rat middle cerebral artery and whole-cell patch clamp in CHO cells","pmids":["19934370"],"confidence":"Medium","gaps":["Arachidonic acid modulation not independently replicated","Single lab, single study","Mechanism of lipid enhancement undefined"]},{"year":2014,"claim":"Connected channel loss to a whole-organism cardiovascular phenotype, placing TWIK-2 upstream of Rho-kinase in regulating pulmonary vascular tone.","evidence":"TWIK-2 knockout mice with hemodynamic and morphometric phenotyping and pharmacological epistasis using Rho-kinase inhibitors","pmids":["25245387"],"confidence":"High","gaps":["Molecular link between K+ flux and Rho-kinase activation not defined","Cell-autonomous site of action in vasculature unresolved"]},{"year":2024,"claim":"Assigned TWIK-2 a role in innate immune signaling, showing its K+ efflux drives NLRP3 inflammasome activation and that its expression is controlled by m6A and histone lactylation.","evidence":"Kcnk6 knockout macrophages, AOM/DSS colitis-cancer model, m6A and YTHDF2-binding assays, histone lactylation analysis","pmids":["39269733"],"confidence":"Medium","gaps":["Some mechanistic claims rely on abstract-level description","Direct demonstration that channel-mediated efflux is the trigger not fully detailed","Link to TWIK-2 biophysics not integrated"]},{"year":2026,"claim":"Resolved the molecular architecture and gating logic of TWIK-2, revealing a lipid plug that inactivates the channel, a route for hydrophobic drug access through fenestrations, and pH-insensitive voltage-dependent gating.","evidence":"Cryo-EM structures (peer-reviewed and preprint, including pimozide-bound and R257A/plasma-membrane-targeting mutants) with automated patch clamp and mutagenesis","pmids":["41617707","bio_10.1101_2025.02.24.639991","bio_10.1101_2025.06.11.659167"],"confidence":"High","gaps":["Physiological trigger for lipid plug removal in vivo unknown","Whether lipid gating links to NLRP3 or vascular roles not tested","Endogenous regulators that open the channel undefined"]},{"year":null,"claim":"It remains unknown how the structurally defined lipid-plug gating mechanism is physiologically controlled and how it mechanistically connects K+ efflux to NLRP3 inflammasome activation and Rho-kinase-dependent vascular tone.","evidence":"No discovery in the corpus bridges the structural gating model with the immune and cardiovascular phenotypes","pmids":[],"confidence":"Low","gaps":["Endogenous signal that displaces the lipid plug unidentified","Molecular intermediates between channel activity and Rho-kinase unknown","Cell-type-specific contributions not dissected"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,1,2,8]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[4,7]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[5]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,1]}],"complexes":[],"partners":[],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9Y257","full_name":"Potassium channel subfamily K member 6","aliases":["Inward rectifying potassium channel protein TWIK-2","TWIK-originated similarity sequence"],"length_aa":313,"mass_kda":33.7,"function":"K(+) channel that conducts outward rectifying currents at the membranes of the endolysosomal system (PubMed:10887187, PubMed:28381826). Active in lysosomes where it regulates lysosome numbers and size (PubMed:28381826). In macrophages, enables K(+) efflux coupled to ATP-induced NLRP3 inflammasome activation upon bacterial infection. Cooperates with ATP-gated P2RX7 channels to activate NLRP3 inflammasome, with P2RX7 conducting Ca(2+) and Na(+) influx that sets the membrane potential for K(+) efflux (By similarity) Does not display channel activity","subcellular_location":"Late endosome membrane; Lysosome membrane","url":"https://www.uniprot.org/uniprotkb/Q9Y257/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KCNK6","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/KCNK6","total_profiled":1310},"omim":[{"mim_id":"603940","title":"POTASSIUM CHANNEL, SUBFAMILY K, MEMBER 7; KCNK7","url":"https://www.omim.org/entry/603940"},{"mim_id":"603939","title":"POTASSIUM CHANNEL, SUBFAMILY K, MEMBER 6; KCNK6","url":"https://www.omim.org/entry/603939"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"},{"location":"Actin filaments","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/KCNK6"},"hgnc":{"alias_symbol":["K2p6.1","TWIK-2"],"prev_symbol":[]},"alphafold":{"accession":"Q9Y257","domains":[{"cath_id":"-","chopping":"1-74","consensus_level":"medium","plddt":90.5207,"start":1,"end":74},{"cath_id":"1.10.287.70","chopping":"90-270","consensus_level":"medium","plddt":89.9886,"start":90,"end":270}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y257","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y257-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y257-F1-predicted_aligned_error_v6.png","plddt_mean":82.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KCNK6","jax_strain_url":"https://www.jax.org/strain/search?query=KCNK6"},"sequence":{"accession":"Q9Y257","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9Y257.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9Y257/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y257"}},"corpus_meta":[{"pmid":"10075682","id":"PMC_10075682","title":"TWIK-2, a new weak inward rectifying member of the tandem pore domain potassium channel family.","date":"1999","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10075682","citation_count":124,"is_preprint":false},{"pmid":"10887187","id":"PMC_10887187","title":"TWIK-2, an inactivating 2P domain K+ channel.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10887187","citation_count":107,"is_preprint":false},{"pmid":"25245387","id":"PMC_25245387","title":"TWIK-2 channel deficiency leads to pulmonary hypertension through a rho-kinase-mediated process.","date":"2014","source":"Hypertension (Dallas, Tex. : 1979)","url":"https://pubmed.ncbi.nlm.nih.gov/25245387","citation_count":44,"is_preprint":false},{"pmid":"34195184","id":"PMC_34195184","title":"Potassium Channel Protein KCNK6 Promotes Breast Cancer Cell Proliferation, Invasion, and Migration.","date":"2021","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/34195184","citation_count":24,"is_preprint":false},{"pmid":"39269733","id":"PMC_39269733","title":"The m6A methyltransferase METTL3 modifies Kcnk6 promoting on inflammation associated carcinogenesis is essential for colon homeostasis and defense system through histone lactylation dependent YTHDF2 binding.","date":"2024","source":"International reviews of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/39269733","citation_count":24,"is_preprint":false},{"pmid":"19934370","id":"PMC_19934370","title":"Characterization of TWIK-2, a two-pore domain K+ channel, cloned from the rat middle cerebral artery.","date":"2009","source":"Experimental biology and medicine (Maywood, N.J.)","url":"https://pubmed.ncbi.nlm.nih.gov/19934370","citation_count":16,"is_preprint":false},{"pmid":"14689445","id":"PMC_14689445","title":"Genomic structure, cochlear expression, and mutation screening of KCNK6, a candidate gene for DFNA4.","date":"2004","source":"Journal of neuroscience research","url":"https://pubmed.ncbi.nlm.nih.gov/14689445","citation_count":11,"is_preprint":false},{"pmid":"21359819","id":"PMC_21359819","title":"Dexamethasone-induced up-regulation of two-pore domain K+ channel genes, TASK-1 and TWIK-2, in cultured human periodontal ligament fibroblasts.","date":"2011","source":"In vitro cellular & developmental biology. Animal","url":"https://pubmed.ncbi.nlm.nih.gov/21359819","citation_count":4,"is_preprint":false},{"pmid":"41617707","id":"PMC_41617707","title":"Insights into the structure and modulation of human TWIK-2.","date":"2026","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/41617707","citation_count":0,"is_preprint":false},{"pmid":"40161613","id":"PMC_40161613","title":"Insights into the structure and modulation of human TWIK-2.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/40161613","citation_count":0,"is_preprint":false},{"pmid":"10894943","id":"PMC_10894943","title":"Genomic sequencing reveals the structure of the Kcnk6 and map3k11 genes and their close vicinity to the sipa1 gene on mouse chromosome 19.","date":"2000","source":"Cytogenetics and cell genetics","url":"https://pubmed.ncbi.nlm.nih.gov/10894943","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.02.24.639991","title":"Structure of the human TWIK-2 potassium channel and its inhibition by pimozide","date":"2025-02-27","source":"bioRxiv","url":"https://doi.org/10.1101/2025.02.24.639991","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.06.11.659167","title":"A lipid plug affects K  <sub>2P</sub>  6.1(TWIK-2) function","date":"2025-06-15","source":"bioRxiv","url":"https://doi.org/10.1101/2025.06.11.659167","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8574,"output_tokens":2977,"usd":0.035188,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10329,"output_tokens":2723,"usd":0.05986,"stage2_stop_reason":"end_turn"},"total_usd":0.095048,"stage1_batch_id":"msgbatch_01BbTCMyrRPyhtEq6b1MdwCN","stage2_batch_id":"msgbatch_011dEed5bbxYvTAaQWKJevxu","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"TWIK-2 (KCNK6) was cloned from human brain cDNA and shown to function as a non-inactivating weak inward rectifier K+ channel with two pore-forming domains; it is inhibited by intracellular but not extracellular acidification, and is pharmacologically distinct from TWIK-1 in its responses to quinidine, quinine, and barium when expressed heterologously in Xenopus oocytes.\",\n      \"method\": \"Heterologous expression in Xenopus oocytes, electrophysiology, pharmacological profiling\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct electrophysiological characterization in heterologous expression system with pharmacological profiling; foundational characterization paper replicated by subsequent studies\",\n      \"pmids\": [\"10075682\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Human and rat TWIK-2 expressed in COS cells display outward rectification in physiological K+ gradient and mild inward rectification in symmetrical K+; currents inactivate at depolarized potentials with temperature-sensitive kinetics. Cysteine 53 in the M1P1 external loop is required for functional expression but not for subunit self-assembly. TWIK-2 has extremely low single-channel conductance.\",\n      \"method\": \"Heterologous expression in COS cells, whole-cell and single-channel patch clamp, site-directed mutagenesis (C53 mutant), temperature-dependent kinetic analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro electrophysiology with mutagenesis and multiple orthogonal methods confirming inactivation and rectification as intrinsic properties; replicated across human and rat isoforms\",\n      \"pmids\": [\"10887187\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Rat TWIK-2 cloned from the middle cerebral artery and expressed in CHO cells shows relatively linear currents at physiological K+ concentrations, mild inward rectification in symmetrical K+, insensitivity to TEA, 4-aminopyridine, and glibenclamide, inhibition by Ba2+ (IC50 ~80 µM), and 60% enhancement of activity by 100 µM arachidonic acid.\",\n      \"method\": \"Cloning from rat middle cerebral artery, heterologous expression in CHO cells, whole-cell patch clamp, pharmacological profiling\",\n      \"journal\": \"Experimental biology and medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — direct electrophysiology in heterologous system but single lab, single study; arachidonic acid modulation is a novel finding not independently replicated\",\n      \"pmids\": [\"19934370\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TWIK-2 knockout mice develop pulmonary hypertension and pulmonary vascular remodeling by 20 weeks of age. Pulmonary artery branches from knockout mice show enhanced contractile response to thromboxane A2 mimetic U46619, which is abolished by the Rho-kinase inhibitor Y27632. Treatment with Rho-kinase inhibitor fasudil abolishes hypertension development, placing TWIK-2 upstream of Rho-kinase in vascular tone regulation.\",\n      \"method\": \"TWIK-2 knockout mouse model, hemodynamic measurements (right ventricular systolic pressure), vascular morphometry, ex vivo vasoconstriction assay, pharmacological rescue with Rho-kinase inhibitor (fasudil, Y27632)\",\n      \"journal\": \"Hypertension\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with defined hemodynamic and structural phenotype, pharmacological epistasis with Rho-kinase inhibitor rescue demonstrating pathway placement\",\n      \"pmids\": [\"25245387\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Twik-2 protein is expressed in the mouse cochlea, specifically localised predominantly within the stria vascularis as determined by immunohistochemistry and immunoblot, suggesting a role in potassium ion recycling into the endolymph. However, no causative mutations were found in KCNK6 in DFNA4 hearing loss families.\",\n      \"method\": \"RT-PCR, immunoblot (35 kDa band), immunohistochemistry of cochlear sections\",\n      \"journal\": \"Journal of neuroscience research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct localization by immunohistochemistry and protein detection, single lab; functional implication is inferential, no functional KO or electrophysiology\",\n      \"pmids\": [\"14689445\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL3-mediated m6A modification increases KCNK6 mRNA stability in a YTHDF2-dependent manner; histone lactylation activates transcription of YTHDF2/Kcnk6. Loss of Kcnk6 in macrophages inhibits NLRP3 inflammasome activation and reduces inflammatory factors, while Kcnk6 accelerates potassium channel activity to induce NLRP3 inflammasome activation.\",\n      \"method\": \"Kcnk6 knockout mouse model, bone marrow-derived macrophages, AOM/DSS colitis-cancer model, in vitro cell lines (HCT116, Caco2), m6A modification assays, YTHDF2-binding studies, histone lactylation analysis\",\n      \"journal\": \"International reviews of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with defined inflammatory phenotype, m6A/YTHDF2 mechanism supported by multiple assays in single lab; some mechanistic claims rely on abstract-level description without full methodological detail\",\n      \"pmids\": [\"39269733\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cryo-EM structure of human TWIK-2 at 2.85 Å resolution reveals a unique 'up' conformation of Tyr111 in the selectivity filter and a SF1-P1 pocket behind the filter. Acyl chains occupy lateral fenestrations within the transmembrane region connecting the central cavity to the lipid membrane. Pimozide inhibits TWIK-2 by displacing acyl chains and binding below the selectivity filter to block ion conduction, potentially accessing its site via the membrane.\",\n      \"method\": \"Cryo-EM structure determination, electrophysiology (pimozide inhibition assay), structural comparison with other K2P channels\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — high-resolution cryo-EM structure with pimozide-bound complex and electrophysiological validation; preprint not yet peer-reviewed but structural evidence is direct\",\n      \"pmids\": [\"bio_10.1101_2025.02.24.639991\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cryo-EM structures of human TWIK-2 (K2P6.1) in nanodisc and detergent environments reveal an unusual SF1 conformation and a 'lipid plug' consisting of two-chain lipids in the channel cavity, with each lipid occupying two distinct binding sites (upper and lower fenestration legs). An R257A mutant that increases channel function alters lipid plug position, indicating R257 is key to lipid binding. A plasma-membrane-targeting mutant yielded both plugged and unplugged forms, suggesting lipid plug occupancy renders TWIK channels inactive and plug removal is required for ion-permeable pore formation.\",\n      \"method\": \"Cryo-EM structure determination (nanodisc and detergent conditions), site-directed mutagenesis (R257A and plasma-membrane-targeting mutant), structural comparison of plugged vs. unplugged conformations\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct cryo-EM structures with mutagenesis validating lipid plug mechanism; preprint not yet peer-reviewed but uses multiple structural conditions and mutants as orthogonal evidence\",\n      \"pmids\": [\"bio_10.1101_2025.06.11.659167\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Cryo-EM structure of human TWIK-2 at 3.7 Å reveals conserved and distinctive structural features. Gating in TWIK-2 is voltage-dependent and insensitive to extracellular pH changes. Site-directed mutagenesis identified key residues influencing TWIK-2 activity, and lipid-mediated regulation is implicated as a mechanism of TWIK-2 modulation.\",\n      \"method\": \"Single particle cryo-EM (3.7 Å), automated whole-cell patch clamp, site-directed mutagenesis, high-throughput small molecule screening\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — peer-reviewed cryo-EM structure combined with mutagenesis and automated electrophysiology; voltage-dependence and pH-insensitivity established by direct functional assay\",\n      \"pmids\": [\"41617707\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Dexamethasone upregulates TWIK-2 (KCNK6) mRNA expression in human periodontal ligament fibroblasts in a dose- and time-dependent manner; this effect is abolished by a glucocorticoid receptor antagonist, indicating glucocorticoid receptor-mediated transcriptional regulation of TWIK-2.\",\n      \"method\": \"RT-PCR of mRNA expression in cultured human PDL fibroblasts, glucocorticoid receptor antagonist pharmacology\",\n      \"journal\": \"In vitro cellular & developmental biology. Animal\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — mRNA-level upregulation with pharmacological receptor blockade; no protein-level, electrophysiological, or functional downstream validation; single lab\",\n      \"pmids\": [\"21359819\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TWIK-2 (KCNK6) is a two-pore domain K+ channel that forms a homodimer with extremely low conductance, voltage-dependent gating that is insensitive to extracellular pH, and inactivation at depolarized potentials; its cryo-EM structure reveals a unique SF1 conformation, a lipid plug in the channel cavity that renders it inactive, and lateral fenestrations through which lipids and hydrophobic drugs (including the inhibitor pimozide) access a binding site below the selectivity filter; functionally, TWIK-2 promotes K+ efflux to activate the NLRP3 inflammasome in macrophages (regulated transcriptionally by METTL3-mediated m6A modification via YTHDF2 and histone lactylation), and its loss in mice causes pulmonary hypertension through a Rho-kinase-dependent mechanism.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"KCNK6 (TWIK-2/K2P6.1) is a two-pore-domain potassium channel that forms a homodimer with extremely low single-channel conductance and contributes to background K+ flux that shapes cellular excitability and tone [#0, #1]. Heterologous expression established it as a weak inward rectifier that inactivates at depolarized potentials with temperature-sensitive kinetics, is inhibited by intracellular but not extracellular acidification, and depends on an external-loop cysteine (C53) for functional surface expression [#0, #1]; subsequent functional work confirmed voltage-dependent gating that is insensitive to extracellular pH [#8]. Cryo-EM structures of the human channel reveal a distinctive selectivity-filter (SF1) conformation and a 'lipid plug' of two-chain lipids occupying the central cavity and lateral fenestrations, which renders the channel inactive; an R257A mutation repositions this plug and increases channel function, and removal of the plug is required to form an ion-permeable pore [#7]. These fenestrations also serve as the access route for hydrophobic inhibitors: the antipsychotic pimozide displaces the acyl chains and binds below the selectivity filter to block ion conduction [#6]. Physiologically, TWIK-2 promotes K+ efflux that activates the NLRP3 inflammasome in macrophages, with its expression controlled by METTL3-mediated m6A modification acting through YTHDF2 and by histone lactylation [#5], and its genetic loss in mice causes pulmonary hypertension and vascular remodeling through a Rho-kinase-dependent mechanism [#3].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Established the molecular identity and basic biophysical class of KCNK6, defining it as a two-pore-domain weak inward rectifier K+ channel distinct from TWIK-1.\",\n      \"evidence\": \"Cloning from human brain cDNA and electrophysiology/pharmacological profiling in Xenopus oocytes\",\n      \"pmids\": [\"10075682\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Native cell type and physiological function not addressed\", \"No structural basis for gating\", \"pH sensitivity restricted to heterologous context\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Defined inactivation, rectification, and low conductance as intrinsic channel properties and identified a residue (C53) required for functional expression but not subunit assembly.\",\n      \"evidence\": \"Whole-cell and single-channel patch clamp with site-directed mutagenesis in COS cells across human and rat isoforms\",\n      \"pmids\": [\"10887187\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism linking C53 to surface trafficking unresolved\", \"Physiological role still unknown\", \"Endogenous modulators not identified\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Provided the first tissue localization, placing TWIK-2 protein in the cochlear stria vascularis and implicating it in potassium recycling, while excluding it as a DFNA4 disease gene.\",\n      \"evidence\": \"RT-PCR, immunoblot, and immunohistochemistry of mouse cochlea plus mutation screening of DFNA4 families\",\n      \"pmids\": [\"14689445\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional contribution to endolymph K+ inferential, no KO or electrophysiology in cochlea\", \"No causative human disease mutation found\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Extended characterization to vascular tissue, showing arachidonic acid enhances TWIK-2 currents and defining its pharmacological insensitivity profile.\",\n      \"evidence\": \"Cloning from rat middle cerebral artery and whole-cell patch clamp in CHO cells\",\n      \"pmids\": [\"19934370\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Arachidonic acid modulation not independently replicated\", \"Single lab, single study\", \"Mechanism of lipid enhancement undefined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Connected channel loss to a whole-organism cardiovascular phenotype, placing TWIK-2 upstream of Rho-kinase in regulating pulmonary vascular tone.\",\n      \"evidence\": \"TWIK-2 knockout mice with hemodynamic and morphometric phenotyping and pharmacological epistasis using Rho-kinase inhibitors\",\n      \"pmids\": [\"25245387\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link between K+ flux and Rho-kinase activation not defined\", \"Cell-autonomous site of action in vasculature unresolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Assigned TWIK-2 a role in innate immune signaling, showing its K+ efflux drives NLRP3 inflammasome activation and that its expression is controlled by m6A and histone lactylation.\",\n      \"evidence\": \"Kcnk6 knockout macrophages, AOM/DSS colitis-cancer model, m6A and YTHDF2-binding assays, histone lactylation analysis\",\n      \"pmids\": [\"39269733\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Some mechanistic claims rely on abstract-level description\", \"Direct demonstration that channel-mediated efflux is the trigger not fully detailed\", \"Link to TWIK-2 biophysics not integrated\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Resolved the molecular architecture and gating logic of TWIK-2, revealing a lipid plug that inactivates the channel, a route for hydrophobic drug access through fenestrations, and pH-insensitive voltage-dependent gating.\",\n      \"evidence\": \"Cryo-EM structures (peer-reviewed and preprint, including pimozide-bound and R257A/plasma-membrane-targeting mutants) with automated patch clamp and mutagenesis\",\n      \"pmids\": [\"41617707\", \"bio_10.1101_2025.02.24.639991\", \"bio_10.1101_2025.06.11.659167\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological trigger for lipid plug removal in vivo unknown\", \"Whether lipid gating links to NLRP3 or vascular roles not tested\", \"Endogenous regulators that open the channel undefined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unknown how the structurally defined lipid-plug gating mechanism is physiologically controlled and how it mechanistically connects K+ efflux to NLRP3 inflammasome activation and Rho-kinase-dependent vascular tone.\",\n      \"evidence\": \"No discovery in the corpus bridges the structural gating model with the immune and cardiovascular phenotypes\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Endogenous signal that displaces the lipid plug unidentified\", \"Molecular intermediates between channel activity and Rho-kinase unknown\", \"Cell-type-specific contributions not dissected\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 1, 2, 8]},\n      {\"term_id\": \"GO:0005216\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [4, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"complexes\": [],\n    \"partners\": [],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":3,"faith_total":3,"faith_pct":100.0}}