{"gene":"KCNN4","run_date":"2026-06-10T02:59:49","timeline":{"discoveries":[{"year":1997,"finding":"hSK4 (KCNN4) encodes a calcium-activated potassium channel with ~12 pS conductance in physiological saline, very high Ca2+ affinity (EC50 ~95 nM), and contains a leucine zipper-like domain in its C terminus. It is predominantly expressed in nonexcitable tissues.","method":"Heterologous expression in CHO cells, patch-clamp electrophysiology","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct channel reconstitution with electrophysiological characterization, founding paper replicated by multiple subsequent studies","pmids":["9380751"],"is_preprint":false},{"year":1997,"finding":"hKCa4 (KCNN4) encodes an intermediate conductance (~33 pS in symmetrical K+), voltage-independent, inwardly rectifying Ca2+-activated K+ channel in human T lymphocytes, activated by intracellular Ca2+ (Kd ~270 nM) with ~3 Ca2+ ions per channel cooperativity; blocked by charybdotoxin and clotrimazole but resistant to apamin, iberiotoxin, and margatoxin.","method":"Heterologous expression in HEK293 cells, patch-clamp electrophysiology, pharmacological profiling","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct reconstitution with quantitative single-channel and pharmacological characterization, independently confirmed by multiple labs","pmids":["9407042"],"is_preprint":false},{"year":1999,"finding":"hSK4 (KCNN4) lacks intrinsic Ca2+-binding sites but contains a Ca2+-dependent calmodulin (CaM)-binding site mapped to the proximal C terminus (Ct1). Deletion of either Ct1 or the distal C terminus abolishes channel function. The channel regulates membrane potential, T cell proliferation, and volume regulation.","method":"CaM-binding domain mapping by deletion mutagenesis, stable CHO cell expression, patch-clamp, proliferation and volume assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — mutagenesis combined with functional patch-clamp readout, multiple orthogonal methods","pmids":["10329683"],"is_preprint":false},{"year":2006,"finding":"NDPK-B (nucleoside diphosphate kinase B), a mammalian histidine kinase, directly binds KCa3.1 and activates it by phosphorylating histidine 358 in the carboxyl terminus. This histidine phosphorylation is required for KCa3.1 channel activity and subsequent Ca2+ influx and CD4 T cell activation. NDPK-B functions downstream of PI(3)P.","method":"Co-immunoprecipitation, in vitro kinase assay, site-directed mutagenesis (H358), patch-clamp in T cells, siRNA knockdown","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct biochemical interaction plus mutagenesis of phosphorylation site plus functional readout, multiple orthogonal methods","pmids":["17157250"],"is_preprint":false},{"year":2008,"finding":"Protein histidine phosphatase 1 (PHPT-1) directly binds KCa3.1 and inhibits it by dephosphorylating histidine 358. Overexpression of wild-type but not phosphatase-dead PHPT-1 inhibited channel activity; siRNA knockdown of PHPT-1 increased KCa3.1 activity, Ca2+ influx, and T cell proliferation.","method":"Co-immunoprecipitation, phosphatase-dead mutant overexpression, siRNA knockdown, patch-clamp, Ca2+ imaging","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — reciprocal regulation demonstrated with mutagenesis, functional readout, and loss-of-function, multiple orthogonal methods","pmids":["18796614"],"is_preprint":false},{"year":2005,"finding":"Phosphatidylinositol 3-phosphate [PI(3)P] indirectly activates KCa3.1 via a stretch of 14 amino acids in the carboxy-terminal calmodulin binding domain. This 14-aa segment is sufficient to confer PI(3)P regulation when transferred to the related KCa2.3 channel, suggesting it recruits an accessory regulatory subunit required for Ca2+ gating.","method":"Chimeric channel construction between KCa3.1 and KCa2.3, patch-clamp, site-directed mutagenesis","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1 / Moderate — domain swap mutagenesis with functional electrophysiological readout, single lab but multiple channel constructs tested","pmids":["16251351"],"is_preprint":false},{"year":2016,"finding":"Histidine 358 phosphorylation activates KCa3.1 by antagonizing copper-mediated inhibition of the channel. CD4+ T cells deficient in intracellular copper show increased KCa3.1 histidine phosphorylation and channel activity, leading to increased Ca2+ flux and cytokine production.","method":"In vitro copper inhibition assays, H358 mutagenesis, patch-clamp, Ca2+ flux measurements in copper-deficient T cells","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mechanistic dissection with mutagenesis plus cellular validation, single lab but multiple orthogonal methods","pmids":["27542194"],"is_preprint":false},{"year":2003,"finding":"The KCNN4 (hSK4) isoform encodes the Gardos channel in human red blood cells. Only SK4 mRNA was detected in reticulocytes; SK4 protein was found in red blood cell ghost membranes; heterologously expressed SK4 recapitulates the Ko+-dependence behavior of the native Gardos channel, and temperature-dependent reduction of open probability is shared by native RBC and SK4-expressing CHO cells.","method":"RT-PCR, Northern blot, Western blot of RBC ghosts, inside-out patch-clamp, heterologous expression in CHO cells","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal identification methods plus functional recapitulation of native channel properties","pmids":["12773623"],"is_preprint":false},{"year":2004,"finding":"Genetic deletion of Kcnn4 in mice abolishes IK channel activity in red blood cells and T lymphocytes, severely impairing volume regulation in both cell types. Despite loss of IK in parotid acinar cells, fluid secretion and regulatory volume decrease remain normal, indicating Kcnn4 is dispensable for salivary gland secretion.","method":"Kcnn4 knockout mouse, patch-clamp, K+ permeability assays, fluid secretion measurements","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined cell-type-specific phenotypes confirmed across multiple tissues","pmids":["15347667"],"is_preprint":false},{"year":2008,"finding":"AMP-activated protein kinase (AMPK) inhibits KCa3.1 channel activity. The AMPK γ1-subunit directly interacts with a C-terminal region (Asp380–Ala400) of KCa3.1 as shown by two-hybrid screening and pull-down. Co-immunoprecipitation confirmed the KCa3.1/AMPK-γ1 complex at endogenous levels. AMPK activation with AICAR decreased KCa3.1-mediated short-circuit currents in bronchial epithelial cells.","method":"Two-hybrid screening, pull-down assay, co-immunoprecipitation in bronchial cells, inside-out patch-clamp, Ussing chamber short-circuit current","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal interaction shown by multiple methods plus functional epithelial readout, single lab","pmids":["19052260"],"is_preprint":false},{"year":2013,"finding":"CaM N-lobe binding to KCa3.1 controls gating: residues R362 and E363 (electrostatic) and M368 (hydrophobic) in the CaM-binding domain are key determinants of channel activation and open probability at saturating Ca2+, while S367 solvation energy controls the stability of the CaM–KCa3.1 complex and deactivation kinetics.","method":"Structural homology modeling based on rSK2 crystal structure, cross-linking mutagenesis (R362-K75 CaM), patch-clamp of mutant channels","journal":"The Journal of general physiology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — structure-guided mutagenesis with cross-linking validation and functional patch-clamp readout, single lab","pmids":["23797421"],"is_preprint":false},{"year":2014,"finding":"PKA phosphorylates Ser334 in the CaM-binding C terminus of KCa3.1, reducing CaM binding and channel open probability. Mutating S334A abolishes PKA-dependent regulation. PKA activation through the adenosine A2a receptor similarly reduces KCa3.1 current and subsequent CRAC-mediated Ca2+ entry in microglia.","method":"Site-directed mutagenesis (S334A), CaM-affinity chromatography, single-channel patch-clamp, Ca2+ imaging in microglia and HEK293 cells","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mutagenesis plus biochemical CaM-binding assay plus single-channel analysis, multiple orthogonal methods","pmids":["25274816"],"is_preprint":false},{"year":2010,"finding":"Plasma membrane KCa3.1 is internalized and targeted to lysosomes for degradation via a Rab7- and ESCRT-dependent pathway. TSG101 (ESCRT-I) co-immunoprecipitates with KCa3.1; dominant-negative TSG101, CHMP4, and VPS4 each inhibit KCa3.1 degradation rate.","method":"Immunofluorescence, electron microscopy, co-immunoprecipitation, dominant-negative constructs, siRNA knockdown of Rab7/ESCRT components","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple ESCRT components tested with reciprocal co-IP and dominant negatives, single lab","pmids":["20720181"],"is_preprint":false},{"year":2013,"finding":"Globotriaosylceramide (Gb3) triggers clathrin-dependent endocytosis and lysosomal degradation of endothelial KCa3.1. Knockdown of clathrin, Rab5, or lysosomal inhibitor treatment all rescue KCa3.1 expression and current; Rab5 knockdown also restores endothelium-dependent relaxation.","method":"Pharmacological inhibitors, siRNA knockdown of clathrin and Rab5, immunofluorescence, patch-clamp, vessel relaxation assay","journal":"Arteriosclerosis, thrombosis, and vascular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple genetic/pharmacological interventions with functional readout, single lab","pmids":["24158513"],"is_preprint":false},{"year":2010,"finding":"Three splice variants of KCNN4 (KCNN4a, KCNN4b, KCNN4c) are expressed in rat colon with tissue specificity: KCNN4a in smooth muscle, KCNN4b/c in epithelial cells. KCNN4b and KCNN4c encode basolateral and apical membrane proteins, respectively. KCNN4c, lacking the S2 transmembrane segment, requires coexpression of a large conductance K+ channel β-subunit for plasma membrane expression.","method":"RT-PCR, real-time qPCR, immunofluorescence, 86Rb efflux assay, heterologous coexpression","journal":"American journal of physiology. Cell physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — molecular cloning with functional expression and membrane localization, single lab","pmids":["20445171"],"is_preprint":false},{"year":2007,"finding":"KCNN4/KCa3.1 is expressed in rat microglia and contributes to microglial activation, inducible nitric oxide synthase upregulation, nitric oxide and peroxynitrite production, and p38 MAPK activation (but not NF-κB), leading to neurotoxicity. TRAM-34 treatment of microglia (not neurons) reduces neuronal killing, and intraocular TRAM-34 reduces retinal ganglion cell degeneration after optic nerve transection.","method":"Selective pharmacological blockade (TRAM-34), Transwell co-culture assay, fluorescence-based NO/peroxynitrite assays, in vivo optic nerve injury model","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pathway dissection with selective inhibitor in vitro and in vivo, single lab, multiple readouts","pmids":["17202491"],"is_preprint":false},{"year":2008,"finding":"KCa3.1 channels localize specifically to endothelial cell projections at myoendothelial gap junctions in mesenteric arteries, co-localizing with Na+/K+-ATPase α2/α3. PKA activation blocks KCa3.1 contribution to EDHF hyperpolarization independent of endothelial [Ca2+]i changes. KCa3.1-mediated hyperpolarization links to arterial relaxation primarily through Na+/K+-ATPase (K+ acting as EDHF), distinct from KCa2.3 pathways.","method":"Confocal z-stack immunofluorescence of pressurized arteries, pharmacological blockade (forskolin, TRAM-34), electrophysiology, Ca2+ imaging","journal":"Circulation research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct subcellular localization linked to functional EDHF pathway dissection, single lab","pmids":["18403729"],"is_preprint":false},{"year":2010,"finding":"KCa3.1 knockout CD4 T cells show decreased TCR-stimulated Ca2+ influx and IL-2 production. KCa3.1 loss impairs Ca2+ influx and cytokine production in Th1 and Th2 cells but not in T-regulatory or Th17 cells. KCa3.1-/- mice are protected from T-cell-mediated colitis in two IBD models.","method":"KCa3.1 knockout mouse, adoptive transfer colitis model, TNBS colitis model, Ca2+ flux measurements, cytokine assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined Ca2+ signaling and cytokine defects across multiple T cell subsets and two in vivo models","pmids":["20080610"],"is_preprint":false},{"year":2012,"finding":"KCa3.1 localizes to the uropod of migrating activated human T lymphocytes (not the leading edge), and co-localizes with TRPM7. Blockade of KCa3.1 (TRAM-34) but not Kv1.3, CRAC, or TRPM4 inhibits T cell migration on ICAM-1 surfaces; Ca2+ oscillations are detected at the uropod where KCa3.1 and TRPM7 accumulate.","method":"Confocal microscopy on ICAM-1 polymer surfaces, Ca2+ imaging, pharmacological blockade, T cell migration assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization linked to migration function, multiple channel blockers as controls, single lab","pmids":["22952790"],"is_preprint":false},{"year":2013,"finding":"KCa3.1 is selectively coupled to P2Y2 receptor (UTP) activation in rat microglia. KCa3.1 current is activated by Ca2+ entry through CRAC/Orai1 channels; both channels facilitate Ca2+ store refilling and are physically associated. Blocking either KCa3.1 or CRAC/Orai1 inhibits microglial migration stimulated by UTP.","method":"Whole-cell patch-clamp, Ca2+ imaging, pharmacological blockade, co-immunoprecipitation (implied close association), migration assay","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional coupling demonstrated electrophysiologically with pharmacological dissection plus migration readout, single lab","pmids":["23620825"],"is_preprint":false},{"year":2013,"finding":"Bradykinin raises [Ca2+]i in glioma cells, which activates KCa3.1 channels and Ca2+-dependent Cl- channels (ClC-3, activated via CaMKII) in a coordinated manner to drive a biphasic voltage response that mediates chemotactic migration. Inhibition of either KCa3.1 or ClC-3 abolishes bradykinin-induced chemotaxis and reduces tumor expansion in brain slices.","method":"Simultaneous fura-2 Ca2+ imaging and perforated patch-clamp, pharmacological blockade (TRAM-34, DIDS), CaMKII inhibition, shRNA knockdown of ClC-3, brain slice migration assay","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — simultaneous electrophysiology and Ca2+ imaging plus genetic knockdown and pharmacology, multiple orthogonal methods","pmids":["23345219"],"is_preprint":false},{"year":2014,"finding":"Kcnn4 is required for osteoclast and multinucleate giant cell (MGC) formation in rodents and humans. Genetic deletion of Kcnn4 reduces macrophage multinucleation through modulation of Ca2+ signaling, increases bone mass, and improves clinical outcome in arthritis models. Kcnn4 was identified as the most significantly trans-regulated gene in a macrophage multinucleation network.","method":"Systems genetics in rat macrophages, Kcnn4 knockout mouse (osteoclast/MGC formation, bone mass, arthritis model), Ca2+ signaling assays","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic deletion with defined cellular and in vivo phenotypes across multiple models","pmids":["25131209"],"is_preprint":false},{"year":2013,"finding":"KCNN4 channels mediate EMT induced by PRL-3 in colorectal cancer by increasing intracellular Ca2+, activating CaM-kinase II and GSK-3β, increasing Snail expression, and downregulating E-cadherin. KCNN4 siRNA or TRAM-34 restores E-cadherin and inhibits Snail.","method":"siRNA knockdown, pharmacological blockade (TRAM-34), intracellular Ca2+ measurements, Western blot for CaMKII, GSK-3β, Snail, E-cadherin","journal":"Medical oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic and pharmacological loss-of-function with defined signaling cascade, single lab","pmids":["23572150"],"is_preprint":false},{"year":2019,"finding":"GABRP physically interacts with KCNN4 (co-immunoprecipitation, proximity ligation assay) to induce Ca2+ entry, which activates NF-κB signaling and induces CXCL5 and CCL20 expression in pancreatic cancer cells, facilitating macrophage infiltration in a GABA-independent manner.","method":"Co-immunoprecipitation, proximity ligation assay, electrophysiology, NF-κB reporter assay, transwell and orthotopic xenograft models","journal":"Gut","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct protein interaction confirmed by two methods plus functional Ca2+/NF-κB signaling readout, single lab","pmids":["30826748"],"is_preprint":false},{"year":2019,"finding":"Junctophilin proteins (JPH3 and JPH4) tether a Cav1.3–RyR2–KCa3.1 tripartite complex at the plasma membrane–ER junction in CA1 hippocampal neurons. shRNA knockdown of JPH3/4 dissociates the complex and reduces the slow afterhyperpolarization current (IsAHP). Infusing JPH3/4 antibodies intracellularly also reduces IsAHP and spike accommodation, confirming functional coupling.","method":"dSTORM super-resolution microscopy, FRET imaging, shRNA knockdown, intracellular antibody infusion, whole-cell patch-clamp","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — super-resolution structural data plus FRET plus genetic and antibody disruption with electrophysiological functional readout, single lab but multiple orthogonal approaches","pmids":["31461656"],"is_preprint":false},{"year":2017,"finding":"CaV1.3 channels exhibit long-duration calcium-dependent facilitation (L-CDF, up to 8 s) when coexpressed with densin and CaMKII, and this prolonged Ca2+ influx strongly activates KCa3.1 to generate a slow afterhyperpolarization tail current in CA1 pyramidal cells. CaV1.3 L-CDF and KCa3.1 coupling is reduced by CaMKII blockade and densin siRNA knockdown.","method":"Heterologous coexpression (tsA-201 cells), whole-cell patch-clamp, CaMKII inhibitor, siRNA knockdown of densin, pharmacological block of CaV1 (isradipine)","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional coupling demonstrated in two cell systems with pharmacological and genetic dissection, single lab","pmids":["29038242"],"is_preprint":false},{"year":2013,"finding":"KCa3.1 is expressed in neuroblasts of the SVZ and RMS but absent in olfactory bulb neurons. Pharmacological inhibition of KCa3.1 prolongs the stationary phase of saltatory neuroblast migration, reducing migration speed by >50%. TRAM-34 injection in vivo significantly reduced the number of neuroblasts reaching the olfactory bulb. KCa3.1 activity depends on Ca2+ influx through TRPC channels (likely TRPC1).","method":"Patch-clamp of neuroblasts in situ, time-lapse confocal microscopy, pharmacological inhibition (TRAM-34, clotrimazole), in vivo injection of TRAM-34, immunolabeling","journal":"Cerebral cortex","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro electrophysiology and migration measurement confirmed in vivo, single lab","pmids":["23585521"],"is_preprint":false},{"year":2019,"finding":"PKA-mediated downregulation of KCa3.1 channels reduces the slow afterhyperpolarization (KCa-sAHP component) in epileptic hippocampal neurons, contributing to hyperexcitability. Acute application of PKA inhibitors reverses KCa3.1 downregulation and normalizes neuronal spike output.","method":"Whole-cell patch-clamp of rat CA1 neurons, PKA inhibitors, pilocarpine epilepsy model","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct electrophysiological dissection of sAHP components with pharmacological rescue, single lab","pmids":["31672789"],"is_preprint":false},{"year":2023,"finding":"PIEZO1 activation triggers Ca2+ influx that activates KCNN4 (KCa3.1), leading to K+ efflux and NLRP3 inflammasome activation. Myeloid-specific deletion of PIEZO1/2 protects mice from gouty arthritis. Pharmacological inhibition of KCNN4 alleviates autoinflammation in CAPS patient cells and CAPS-mutation mice.","method":"Genetic deletion (myeloid-specific Piezo1/2 KO), pharmacological PIEZO1 agonist (Yoda1), KCNN4 inhibition, inflammasome activation assays, Ca2+ flux measurements, in vivo arthritis model","journal":"Science immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — mechanistic pathway (PIEZO1→Ca2+→KCNN4→K+ efflux→NLRP3) established with genetic and pharmacological tools in vitro and in vivo, multiple models","pmids":["38134241"],"is_preprint":false},{"year":2022,"finding":"DSS potentiates NLRP3 inflammasome activation in macrophages by augmenting KCa3.1-mediated K+ efflux. Pharmacological blockade (TRAM-34) or genetic deletion of Kcnn4 attenuates NLRP3 inflammasome assembly in vivo and ameliorates DSS-induced colitis severity.","method":"Kcnn4 knockout mouse, TRAM-34 pharmacological blockade, inflammasome assembly assays, in vitro macrophage stimulation, DSS colitis model","journal":"Cellular & molecular immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic and pharmacological loss-of-function with defined inflammasome readout in vitro and in vivo, single lab","pmids":["35799057"],"is_preprint":false},{"year":2015,"finding":"Mutations in KCNN4 (Gardos channel) at a highly conserved residue are associated with hereditary xerocytosis. Both identified mutations are predicted to cause delayed channel inactivation, consistent with a gain-of-function mechanism causing erythrocyte dehydration.","method":"Whole-exome sequencing, segregation analysis in two HX kindreds, mutation effect prediction algorithms","journal":"Blood","confidence":"Low","confidence_rationale":"Tier 3 / Weak — genetic association with disease-linked mutations but no direct functional channel assay performed in this study","pmids":["26198474"],"is_preprint":false},{"year":2014,"finding":"IL-4 upregulates KCNN4 mRNA and KCa3.1 current in alternative-activated rat microglia via the type I IL-4 receptor, requiring JAK3, Ras/MEK/ERK signaling, and the AP-1 transcription factor (not JAK2, STAT6, or PI3K). The increased KCa3.1 is required for IL-4-enhanced microglial migration.","method":"Real-time PCR, patch-clamp, protein synthesis inhibition, kinase inhibitor panel, migration assay (TRAM-34 blockade)","journal":"Frontiers in cellular neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — signaling pathway dissected with inhibitor panel plus functional migration readout, single lab","pmids":["25071444"],"is_preprint":false},{"year":2015,"finding":"PKG elevates KCa3.1 current in microglia through a ROS-dependent, CaMKII-mediated pathway; H2O2 mimics and ROS scavengers/CaMKII inhibitors block the PKG effect. However, direct application of cGMP, PKG, or H2O2 to inside-out patches does not affect single-channel activity or Ca2+ dependence, indicating the regulation is indirect and requires intact intracellular signaling.","method":"Perforated-patch whole-cell recordings in microglia, inside-out single-channel patch-clamp in HEK293, selective PKG inhibitor (KT5823), ROS scavenger, CaMKII inhibitor, H2O2","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — intact-cell and single-channel dissection with multiple selective inhibitors, single lab","pmids":["25904916"],"is_preprint":false},{"year":2015,"finding":"Orai1 co-immunoprecipitates with KCa3.1 (but not Orai2) when coexpressed in HEK293 cells, and both channels co-localize at the plasma membrane. In human lung mast cells, KCa3.1 activation is highly dependent on Ca2+ influx through Orai1; Orai1 E106Q dominant-negative mutant ablates KCa3.1 currents.","method":"Co-immunoprecipitation, confocal co-localization, dominant-negative Orai1 E106Q mutant, patch-clamp","journal":"Cell communication and signaling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct protein interaction plus functional epistasis with dominant negative, single lab","pmids":["26177720"],"is_preprint":false},{"year":2015,"finding":"KCa3.1 co-immunoprecipitates and co-distributes with β1-integrin in alveolar epithelial cells on fibronectin matrix. KCa3.1 inhibition/silencing impairs fibronectin-stimulated wound healing, cell migration, and proliferation. KCa3.1 and TRPC4 have additive inhibitory effects on alveolar repair.","method":"Co-immunoprecipitation, immunofluorescence co-localization, siRNA knockdown, wound-healing assays, KCa3.1 blocker","journal":"Respiratory research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct protein interaction plus functional loss-of-function with migration readout, single lab","pmids":["26335442"],"is_preprint":false},{"year":2013,"finding":"Adenosine selectively inhibits KCa3.1 (not Kv1.3 or TRPM7) in activated human T cells via A2A receptor and cAMP/PKAI signaling pathway. This inhibition reduces T cell motility on ICAM-1 surfaces and IL-2 secretion; the adenosine effect on migration is abolished by pre-exposure to TRAM-34, placing KCa3.1 downstream of A2A/PKAI.","method":"Patch-clamp, selective receptor agonists/antagonists, adenylyl cyclase and PKAI inhibitors, T cell migration assay on ICAM-1 surfaces","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological pathway dissection with multiple selective tools plus epistasis via channel blockade, single lab","pmids":["24227782"],"is_preprint":false},{"year":2022,"finding":"KCa3.1 is present in the inner mitochondrial membrane (mitoKCa3.1) in cancer cells. Mitochondria-targeted TRAM-34 derivatives that block mitoKCa3.1 induce mitochondrial ROS release, membrane depolarization, and mitochondrial network fragmentation, triggering cancer cell death. Plasma-membrane-impermeant Maurotoxin has no effect, confirming the mitochondrial channel is the relevant target. At sub-lethal concentrations, mitoKCa3.1 inhibition reduces cancer cell migration via NF-κB activation, BNIP-3 downregulation, and CDC-42-mediated cytoskeletal reorganization.","method":"Mitochondria-targeted drug synthesis, Maurotoxin (membrane-impermeant blocker), mitochondrial membrane potential assay, ROS measurement, NF-κB reporter, BNIP-3/CDC-42 manipulation, orthotopic in vivo cancer models","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — compartment-specific pharmacological dissection with mechanistic pathway follow-up and in vivo confirmation, single lab","pmids":["36539400"],"is_preprint":false},{"year":2014,"finding":"NOX5-derived ROS are required for bFGF-induced upregulation of KCNN4 mRNA and protein in porcine coronary smooth muscle cells. NOX5 knockdown prevents KCNN4 upregulation and CSMC migration; the mechanism involves NOX5→superoxide→AP-1 transcriptional activation.","method":"siRNA knockdown of individual NOX isoforms, dihydroethidium fluorography, AP-1 luciferase reporter, qRT-PCR, immunohistochemistry, patch-clamp, migration assay","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — selective NOX5 knockdown with mechanistic AP-1 reporter and functional migration readout, single lab","pmids":["25144362"],"is_preprint":false},{"year":2017,"finding":"KCa3.1 regulates Ca2+-dependent NFATc1 expression during osteoclastogenesis via the CaMKIV/CREB/c-fos pathway. KCa3.1-/- and TRAM-34 treatment reduce RANKL-induced Ca2+ transient amplitudes (~50%), prevent CaMKIV phosphorylation, decrease CREB and c-fos, and reduce NFATc1 expression and osteoclast formation.","method":"KCa3.1 knockout BMMs, TRAM-34, live-cell Ca2+ imaging, Western blot (CaMKIV, CREB, c-fos, NFATc1), osteoclast differentiation assay","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic and pharmacological KO/inhibition with defined Ca2+ signaling cascade, single lab","pmids":["29246953"],"is_preprint":false}],"current_model":"KCNN4/KCa3.1 is an intermediate-conductance, voltage-independent K+ channel gated by Ca2+-bound calmodulin constitutively associated with its C-terminal CaM-binding domain; channel activity is uniquely regulated by histidine 358 phosphorylation (activated by NDPK-B, inhibited by PHPT-1) through a mechanism that relieves copper-mediated inhibition, and is further modulated by PKA (inhibitory, via Ser334 reducing CaM binding), PKG/ROS/CaMKII, AMPK-γ1 interaction, and PI(3)P via a 14-aa C-terminal motif; at the plasma membrane it couples functionally to Orai1/CRAC channels, is scaffolded to Cav1.3–RyR2 complexes by junctophilins in neurons, and is targeted for lysosomal degradation via clathrin/Rab7/ESCRT machinery; the channel drives K+ efflux to hyperpolarize the membrane and amplify Ca2+ influx, thereby regulating T cell activation, microglia-mediated neuroinflammation (via p38 MAPK), macrophage multinucleation/osteoclastogenesis (via CaMKIV/NFATc1), NLRP3 inflammasome activation downstream of PIEZO1, erythrocyte volume homeostasis (Gardos channel), and cell migration across many cell types including T lymphocytes, microglia, glioma, mast cells, and neuroblasts."},"narrative":{"mechanistic_narrative":"KCNN4 (KCa3.1/hSK4/hKCa4) is an intermediate-conductance, voltage-independent, inwardly rectifying Ca2+-activated K+ channel that drives K+ efflux to hyperpolarize the membrane and thereby amplify Ca2+ influx in nonexcitable cells, coupling cellular Ca2+ signaling to immune activation, cell volume control, and migration [PMID:9407042, PMID:12773623, PMID:20080610]. The channel has no intrinsic Ca2+-binding sites; instead it is constitutively associated with calmodulin at a C-terminal CaM-binding domain, and Ca2+-loaded CaM N-lobe binding gates the channel through defined residues that set open probability and deactivation kinetics [PMID:10329683, PMID:23797421]. Channel activity is set by a distinctive C-terminal regulatory hub: NDPK-B directly phosphorylates histidine 358 to activate the channel by relieving copper-mediated inhibition, while protein histidine phosphatase PHPT-1 dephosphorylates H358 to inhibit it, and PKA phosphorylation of Ser334 reduces CaM binding and open probability [PMID:17157250, PMID:18796614, PMID:27542194, PMID:25274816]. Additional inputs converge on the C terminus, including direct AMPK-γ1 binding that inhibits the channel and a 14-amino-acid motif conferring PI(3)P-dependent activation [PMID:16251351, PMID:19052260]. At the plasma membrane the channel is functionally coupled to Orai1/CRAC channels that supply its activating Ca2+ and is scaffolded by junctophilins into Cav1.3–RyR2 complexes to generate the neuronal slow afterhyperpolarization current [PMID:31461656, PMID:26177720]; surface levels are controlled by clathrin/Rab5 endocytosis and Rab7/ESCRT-dependent lysosomal degradation [PMID:20720181, PMID:24158513]. Through this Ca2+-amplifying role KCa3.1 governs CD4 T-cell activation and cytokine production, microglial neuroinflammation via p38 MAPK, osteoclast/multinucleate-giant-cell formation via CaMKIV/NFATc1, and NLRP3 inflammasome activation downstream of PIEZO1-mediated Ca2+ entry [PMID:17202491, PMID:20080610, PMID:38134241, PMID:29246953]. In erythrocytes KCa3.1 is the Gardos channel that mediates K+ efflux for volume homeostasis, and gain-of-function KCNN4 mutations are associated with hereditary xerocytosis [PMID:12773623, PMID:26198474].","teleology":[{"year":1997,"claim":"Established the molecular identity of an intermediate-conductance, voltage-independent Ca2+-activated K+ channel with very high Ca2+ sensitivity, defining a distinct channel class enriched in nonexcitable tissues.","evidence":"Heterologous expression in CHO/HEK293 cells with patch-clamp and pharmacological profiling","pmids":["9380751","9407042"],"confidence":"High","gaps":["Did not define the Ca2+-sensing mechanism","No structural basis for gating"]},{"year":1999,"claim":"Resolved how a channel lacking intrinsic Ca2+ sites senses Ca2+ — a constitutively bound calmodulin at the proximal C terminus confers Ca2+ gating and links the channel to T-cell proliferation and volume regulation.","evidence":"Deletion mutagenesis mapping of the CaM-binding domain with patch-clamp and functional assays","pmids":["10329683"],"confidence":"High","gaps":["Did not define which CaM residues drive gating","Distal C-terminal requirement unexplained"]},{"year":2013,"claim":"Defined the structural determinants of CaM-dependent gating, identifying specific CaM-binding-domain residues controlling open probability versus complex stability/deactivation.","evidence":"Structure-guided cross-linking mutagenesis with patch-clamp of mutant channels","pmids":["23797421"],"confidence":"High","gaps":["Based on homology modeling, not a KCa3.1 structure","Single lab"]},{"year":2005,"claim":"Identified a 14-aa C-terminal motif conferring PI(3)P-dependent activation, implying recruitment of an accessory regulatory subunit required for Ca2+ gating.","evidence":"Chimeric KCa3.1/KCa2.3 channels and site-directed mutagenesis with patch-clamp","pmids":["16251351"],"confidence":"High","gaps":["Proposed accessory subunit not identified","Indirect regulation mechanism unresolved"]},{"year":2006,"claim":"Discovered histidine-358 phosphorylation as a unique activating regulatory mechanism, with NDPK-B directly binding and phosphorylating the C terminus to enable channel-driven Ca2+ influx and T-cell activation.","evidence":"Co-IP, in vitro kinase assay, H358 mutagenesis, T-cell patch-clamp and siRNA","pmids":["17157250"],"confidence":"High","gaps":["Did not identify the opposing phosphatase","Molecular consequence of H358 phosphorylation on gating unclear"]},{"year":2008,"claim":"Completed the histidine phospho-switch by identifying PHPT-1 as the phosphatase that dephosphorylates H358 to inhibit the channel, establishing reciprocal kinase/phosphatase control.","evidence":"Co-IP, phosphatase-dead mutant, siRNA, patch-clamp and Ca2+ imaging","pmids":["18796614"],"confidence":"High","gaps":["Did not explain why H358 phosphorylation gates the channel"]},{"year":2016,"claim":"Provided the mechanistic basis of the H358 switch — phosphorylation activates the channel by antagonizing copper-mediated inhibition, linking intracellular copper status to T-cell Ca2+ signaling.","evidence":"In vitro copper inhibition assays, H358 mutagenesis, patch-clamp and Ca2+ flux in copper-deficient T cells","pmids":["27542194"],"confidence":"High","gaps":["Copper-binding site on the channel not defined","Physiological source of inhibitory copper unclear"]},{"year":2008,"claim":"Identified additional C-terminal regulatory inputs: direct AMPK-γ1 binding inhibits the channel, coupling metabolic state to K+ conductance in epithelia.","evidence":"Two-hybrid, pull-down, endogenous co-IP, inside-out patch-clamp and Ussing chamber currents","pmids":["19052260"],"confidence":"High","gaps":["Whether AMPK phosphorylates the channel directly not resolved","Single lab"]},{"year":2014,"claim":"Defined PKA inhibitory regulation through Ser334 phosphorylation that reduces CaM binding and open probability, linking GPCR/cAMP signaling to channel downregulation.","evidence":"S334A mutagenesis, CaM-affinity chromatography, single-channel patch-clamp, Ca2+ imaging in microglia","pmids":["25274816"],"confidence":"High","gaps":["Integration of PKA, NDPK-B/PHPT-1, and AMPK inputs not reconciled"]},{"year":2004,"claim":"Demonstrated in vivo physiological roles via clean genetic deletion: Kcnn4 loss abolishes IK in red cells and T lymphocytes and impairs their volume regulation, while sparing salivary secretion, establishing cell-type-specific requirement.","evidence":"Kcnn4 knockout mouse with patch-clamp, K+ permeability, and fluid secretion assays","pmids":["15347667"],"confidence":"High","gaps":["Did not address inflammatory or migratory roles","Compensation in unaffected tissues not explained"]},{"year":2003,"claim":"Identified KCa3.1 as the long-sought erythrocyte Gardos channel, providing molecular identity to a classic red-cell K+ pathway.","evidence":"RT-PCR, Northern/Western of RBC ghosts, inside-out patch-clamp, heterologous recapitulation of native channel behavior","pmids":["12773623"],"confidence":"High","gaps":["Did not address disease mutations affecting Gardos function"]},{"year":2015,"claim":"Linked KCNN4 to human disease, associating conserved-residue mutations with hereditary xerocytosis via a predicted gain-of-function (delayed inactivation) causing erythrocyte dehydration.","evidence":"Whole-exome sequencing, segregation in two kindreds, mutation-effect prediction","pmids":["26198474"],"confidence":"Low","gaps":["No direct functional channel assay performed in this study","Gating defect inferred computationally only"]},{"year":2010,"claim":"Established the immunological function of the channel in adaptive immunity: KCa3.1 supports TCR-driven Ca2+ influx and cytokine output selectively in Th1/Th2 cells and is required for T-cell-mediated colitis.","evidence":"Knockout CD4 T cells, Ca2+ flux/cytokine assays, two in vivo colitis models","pmids":["20080610"],"confidence":"High","gaps":["Mechanism of subset selectivity (Th1/2 vs Treg/Th17) not defined"]},{"year":2013,"claim":"Showed plasma-membrane KCa3.1 is functionally coupled to Orai1/CRAC channels that supply the Ca2+ for channel activation, integrating store-operated entry with K+ efflux to sustain Ca2+ signaling and migration.","evidence":"Co-IP, co-localization, Orai1 E106Q dominant negative, patch-clamp in mast cells and microglia","pmids":["26177720","23620825"],"confidence":"Medium","gaps":["Whether the KCa3.1–Orai1 association is direct vs scaffolded not resolved","Stoichiometry of the functional coupling unknown"]},{"year":2013,"claim":"Defined surface-level control of the channel through clathrin/Rab5 endocytosis and Rab7/ESCRT-dependent lysosomal degradation, a pathway exploited by Gb3 to suppress endothelial KCa3.1 and impair vasorelaxation.","evidence":"siRNA/dominant-negative of clathrin, Rab5, Rab7, TSG101/CHMP4/VPS4, co-IP, imaging, EM, vessel relaxation assay","pmids":["20720181","24158513"],"confidence":"Medium","gaps":["Trafficking signals on KCa3.1 directing endocytosis not mapped","Regulation of degradation rate by upstream signals unclear"]},{"year":2019,"claim":"Revealed neuronal scaffolding: junctophilins JPH3/4 tether a Cav1.3–RyR2–KCa3.1 tripartite complex at ER–PM junctions in hippocampal neurons, and densin/CaMKII-prolonged Cav1.3 Ca2+ influx drives KCa3.1 to generate the slow afterhyperpolarization.","evidence":"dSTORM/FRET, shRNA, intracellular antibody infusion, heterologous coexpression, whole-cell patch-clamp","pmids":["31461656","29038242"],"confidence":"High","gaps":["Direct KCa3.1–junctophilin contact not biochemically mapped","Generality across neuron types untested"]},{"year":2014,"claim":"Established KCa3.1 as a regulator of myeloid cell fusion and bone biology, where it controls Ca2+-dependent CaMKIV/CREB/c-fos/NFATc1 signaling driving osteoclast and multinucleate-giant-cell formation.","evidence":"Systems genetics, Kcnn4 knockout mouse, osteoclast/MGC and arthritis models, Ca2+ imaging, signaling Western blots","pmids":["25131209","29246953"],"confidence":"High","gaps":["How channel activity is gated specifically during fusion not defined"]},{"year":2007,"claim":"Implicated the channel in CNS innate immunity, showing microglial KCa3.1 drives activation, iNOS/NO/peroxynitrite production, and p38 MAPK-dependent neurotoxicity, with KCa3.1 expression itself shaped by IL-4 (JAK3/Ras/MEK/ERK/AP-1) and PKG/ROS/CaMKII inputs.","evidence":"TRAM-34 blockade, co-culture, NO/peroxynitrite assays, in vivo optic nerve injury, kinase-inhibitor panels, perforated/inside-out patch-clamp","pmids":["17202491","25071444","25904916"],"confidence":"Medium","gaps":["Direct molecular link between K+ efflux and p38 activation unresolved","PKG/ROS effect is indirect with no defined channel-proximal effector"]},{"year":2023,"claim":"Placed KCa3.1 within mechanotransductive innate immune signaling, where PIEZO1-triggered Ca2+ influx activates the channel and the resulting K+ efflux drives NLRP3 inflammasome activation in gout and CAPS models.","evidence":"Myeloid Piezo1/2 KO, Yoda1, KCNN4 inhibition, inflammasome and Ca2+ assays, in vivo arthritis models","pmids":["38134241","35799057"],"confidence":"High","gaps":["Whether K+ efflux directly senses or merely permits NLRP3 assembly not dissected","Coupling of PIEZO1 Ca2+ entry to channel activation not biochemically mapped"]},{"year":2022,"claim":"Identified a non-canonical mitochondrial pool (mitoKCa3.1) in the inner membrane of cancer cells whose inhibition triggers ROS, depolarization, and death, expanding the channel's role beyond the plasma membrane.","evidence":"Mitochondria-targeted vs impermeant blockers, membrane-potential/ROS assays, NF-κB/BNIP-3/CDC-42 manipulation, orthotopic models","pmids":["36539400"],"confidence":"Medium","gaps":["How the channel is imported/inserted into the inner mitochondrial membrane unknown","Single lab"]},{"year":null,"claim":"How the multiple convergent C-terminal regulatory inputs (H358 phospho-switch/copper, Ser334/PKA, AMPK-γ1, PI(3)P, CaM) are integrated in real time on a single channel, and the structural basis of gating, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No experimental KCa3.1 structure in the corpus","Crosstalk and hierarchy among regulatory inputs undefined","Mechanism of mitochondrial targeting unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,1,7]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[12,16,18,33]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[36]},{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[12,13]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[17,28,38]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[3,19,33]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[12,13]}],"complexes":["Cav1.3-RyR2-KCa3.1 junctophilin-tethered complex","KCa3.1-calmodulin complex"],"partners":["CALM1","NME2","PHPT1","PRKAA1/PRKAG1","ORAI1","JPH3","JPH4","GABRP"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O15554","full_name":"Intermediate conductance calcium-activated potassium channel protein 4","aliases":["Gardos channel","IKCa1","hIK1","KCa3.1","Putative Gardos channel","hKCa4"],"length_aa":427,"mass_kda":47.7,"function":"Intermediate conductance calcium-activated potassium channel that mediates the voltage-independent transmembrane transfer of potassium across the cell membrane through a constitutive interaction with calmodulin which binds the intracellular calcium allowing its opening (PubMed:10026195, PubMed:10961988, PubMed:11425865, PubMed:15831468, PubMed:17157250, PubMed:18796614, PubMed:26148990, PubMed:9326665, PubMed:9380751, PubMed:9407042). The current is characterized by a voltage-independent activation, an intracellular calcium concentration increase-dependent activation and a single-channel conductance of about 25 picosiemens (PubMed:9326665, PubMed:9380751, PubMed:9407042). Also presents an inwardly rectifying current, thus reducing its already small outward conductance of potassium ions, which is particularly the case when the membrane potential displays positive values, above + 20 mV (PubMed:9326665, PubMed:9380751, PubMed:9407042). Controls calcium influx during vascular contractility by being responsible of membrane hyperpolarization induced by vasoactive factors in proliferative vascular smooth muscle cell types (By similarity). Following calcium influx, the consecutive activation of KCNN4 channel leads to a hyperpolarization of the cell membrane potential and hence an increase of the electrical driving force for further calcium influx promoting sustained calcium entry in response to stimulation with chemotactic peptides (PubMed:26418693). Required for maximal calcium influx and proliferation during the reactivation of naive T-cells (PubMed:17157250, PubMed:18796614). Plays a role in the late stages of EGF-induced macropinocytosis through activation by PI(3)P (PubMed:24591580)","subcellular_location":"Cell membrane; Cell projection, ruffle membrane","url":"https://www.uniprot.org/uniprotkb/O15554/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KCNN4","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":[{"gene":"PRPF4B","stoichiometry":4.0},{"gene":"RAB8B","stoichiometry":0.2},{"gene":"SNRPA","stoichiometry":0.2},{"gene":"SNRPB","stoichiometry":0.2},{"gene":"SNRPC","stoichiometry":0.2},{"gene":"SNRPF","stoichiometry":0.2},{"gene":"TOP1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/KCNN4","total_profiled":1310},"omim":[{"mim_id":"619952","title":"TRANSMEMBRANE PROTEIN 63B; TMEM63B","url":"https://www.omim.org/entry/619952"},{"mim_id":"616689","title":"DEHYDRATED HEREDITARY STOMATOCYTOSIS 2; DHS2","url":"https://www.omim.org/entry/616689"},{"mim_id":"605879","title":"POTASSIUM CHANNEL, CALCIUM-ACTIVATED, INTERMEDIATE/SMALL CONDUCTANCE, SUBFAMILY N, MEMBER 2; KCNN2","url":"https://www.omim.org/entry/605879"},{"mim_id":"602983","title":"POTASSIUM CHANNEL, CALCIUM-ACTIVATED, INTERMEDIATE/SMALL CONDUCTANCE, SUBFAMILY N, MEMBER 3; KCNN3","url":"https://www.omim.org/entry/602983"},{"mim_id":"602754","title":"POTASSIUM CHANNEL, CALCIUM-ACTIVATED, INTERMEDIATE/SMALL CONDUCTANCE, SUBFAMILY N, MEMBER 4; KCNN4","url":"https://www.omim.org/entry/602754"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"salivary gland","ntpm":119.1}],"url":"https://www.proteinatlas.org/search/KCNN4"},"hgnc":{"alias_symbol":["KCa3.1","hSK4","hKCa4","hIKCa1","IK"],"prev_symbol":[]},"alphafold":{"accession":"O15554","domains":[{"cath_id":"1.10.287.70","chopping":"204-291","consensus_level":"medium","plddt":88.2993,"start":204,"end":291},{"cath_id":"1.10.287.70","chopping":"294-393","consensus_level":"high","plddt":93.4991,"start":294,"end":393},{"cath_id":"1.20.120","chopping":"2-123_147-172","consensus_level":"medium","plddt":86.0539,"start":2,"end":172}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O15554","model_url":"https://alphafold.ebi.ac.uk/files/AF-O15554-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O15554-F1-predicted_aligned_error_v6.png","plddt_mean":84.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KCNN4","jax_strain_url":"https://www.jax.org/strain/search?query=KCNN4"},"sequence":{"accession":"O15554","fasta_url":"https://rest.uniprot.org/uniprotkb/O15554.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O15554/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O15554"}},"corpus_meta":[{"pmid":"9380751","id":"PMC_9380751","title":"hSK4, a member of a novel subfamily of calcium-activated potassium channels.","date":"1997","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/9380751","citation_count":315,"is_preprint":false},{"pmid":"9407042","id":"PMC_9407042","title":"A novel gene, hKCa4, encodes the calcium-activated potassium channel in human T lymphocytes.","date":"1997","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9407042","citation_count":250,"is_preprint":false},{"pmid":"18688283","id":"PMC_18688283","title":"The intermediate-conductance calcium-activated potassium channel KCa3.1 contributes to atherogenesis in mice and humans.","date":"2008","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/18688283","citation_count":203,"is_preprint":false},{"pmid":"10329683","id":"PMC_10329683","title":"hSK4/hIK1, a calmodulin-binding KCa channel in human T lymphocytes. 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It is predominantly expressed in nonexcitable tissues.\",\n      \"method\": \"Heterologous expression in CHO cells, patch-clamp electrophysiology\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct channel reconstitution with electrophysiological characterization, founding paper replicated by multiple subsequent studies\",\n      \"pmids\": [\"9380751\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"hKCa4 (KCNN4) encodes an intermediate conductance (~33 pS in symmetrical K+), voltage-independent, inwardly rectifying Ca2+-activated K+ channel in human T lymphocytes, activated by intracellular Ca2+ (Kd ~270 nM) with ~3 Ca2+ ions per channel cooperativity; blocked by charybdotoxin and clotrimazole but resistant to apamin, iberiotoxin, and margatoxin.\",\n      \"method\": \"Heterologous expression in HEK293 cells, patch-clamp electrophysiology, pharmacological profiling\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct reconstitution with quantitative single-channel and pharmacological characterization, independently confirmed by multiple labs\",\n      \"pmids\": [\"9407042\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"hSK4 (KCNN4) lacks intrinsic Ca2+-binding sites but contains a Ca2+-dependent calmodulin (CaM)-binding site mapped to the proximal C terminus (Ct1). Deletion of either Ct1 or the distal C terminus abolishes channel function. The channel regulates membrane potential, T cell proliferation, and volume regulation.\",\n      \"method\": \"CaM-binding domain mapping by deletion mutagenesis, stable CHO cell expression, patch-clamp, proliferation and volume assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mutagenesis combined with functional patch-clamp readout, multiple orthogonal methods\",\n      \"pmids\": [\"10329683\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"NDPK-B (nucleoside diphosphate kinase B), a mammalian histidine kinase, directly binds KCa3.1 and activates it by phosphorylating histidine 358 in the carboxyl terminus. This histidine phosphorylation is required for KCa3.1 channel activity and subsequent Ca2+ influx and CD4 T cell activation. NDPK-B functions downstream of PI(3)P.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay, site-directed mutagenesis (H358), patch-clamp in T cells, siRNA knockdown\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct biochemical interaction plus mutagenesis of phosphorylation site plus functional readout, multiple orthogonal methods\",\n      \"pmids\": [\"17157250\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Protein histidine phosphatase 1 (PHPT-1) directly binds KCa3.1 and inhibits it by dephosphorylating histidine 358. Overexpression of wild-type but not phosphatase-dead PHPT-1 inhibited channel activity; siRNA knockdown of PHPT-1 increased KCa3.1 activity, Ca2+ influx, and T cell proliferation.\",\n      \"method\": \"Co-immunoprecipitation, phosphatase-dead mutant overexpression, siRNA knockdown, patch-clamp, Ca2+ imaging\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reciprocal regulation demonstrated with mutagenesis, functional readout, and loss-of-function, multiple orthogonal methods\",\n      \"pmids\": [\"18796614\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Phosphatidylinositol 3-phosphate [PI(3)P] indirectly activates KCa3.1 via a stretch of 14 amino acids in the carboxy-terminal calmodulin binding domain. This 14-aa segment is sufficient to confer PI(3)P regulation when transferred to the related KCa2.3 channel, suggesting it recruits an accessory regulatory subunit required for Ca2+ gating.\",\n      \"method\": \"Chimeric channel construction between KCa3.1 and KCa2.3, patch-clamp, site-directed mutagenesis\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — domain swap mutagenesis with functional electrophysiological readout, single lab but multiple channel constructs tested\",\n      \"pmids\": [\"16251351\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Histidine 358 phosphorylation activates KCa3.1 by antagonizing copper-mediated inhibition of the channel. CD4+ T cells deficient in intracellular copper show increased KCa3.1 histidine phosphorylation and channel activity, leading to increased Ca2+ flux and cytokine production.\",\n      \"method\": \"In vitro copper inhibition assays, H358 mutagenesis, patch-clamp, Ca2+ flux measurements in copper-deficient T cells\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mechanistic dissection with mutagenesis plus cellular validation, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"27542194\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The KCNN4 (hSK4) isoform encodes the Gardos channel in human red blood cells. Only SK4 mRNA was detected in reticulocytes; SK4 protein was found in red blood cell ghost membranes; heterologously expressed SK4 recapitulates the Ko+-dependence behavior of the native Gardos channel, and temperature-dependent reduction of open probability is shared by native RBC and SK4-expressing CHO cells.\",\n      \"method\": \"RT-PCR, Northern blot, Western blot of RBC ghosts, inside-out patch-clamp, heterologous expression in CHO cells\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal identification methods plus functional recapitulation of native channel properties\",\n      \"pmids\": [\"12773623\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Genetic deletion of Kcnn4 in mice abolishes IK channel activity in red blood cells and T lymphocytes, severely impairing volume regulation in both cell types. Despite loss of IK in parotid acinar cells, fluid secretion and regulatory volume decrease remain normal, indicating Kcnn4 is dispensable for salivary gland secretion.\",\n      \"method\": \"Kcnn4 knockout mouse, patch-clamp, K+ permeability assays, fluid secretion measurements\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined cell-type-specific phenotypes confirmed across multiple tissues\",\n      \"pmids\": [\"15347667\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"AMP-activated protein kinase (AMPK) inhibits KCa3.1 channel activity. The AMPK γ1-subunit directly interacts with a C-terminal region (Asp380–Ala400) of KCa3.1 as shown by two-hybrid screening and pull-down. Co-immunoprecipitation confirmed the KCa3.1/AMPK-γ1 complex at endogenous levels. AMPK activation with AICAR decreased KCa3.1-mediated short-circuit currents in bronchial epithelial cells.\",\n      \"method\": \"Two-hybrid screening, pull-down assay, co-immunoprecipitation in bronchial cells, inside-out patch-clamp, Ussing chamber short-circuit current\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal interaction shown by multiple methods plus functional epithelial readout, single lab\",\n      \"pmids\": [\"19052260\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"CaM N-lobe binding to KCa3.1 controls gating: residues R362 and E363 (electrostatic) and M368 (hydrophobic) in the CaM-binding domain are key determinants of channel activation and open probability at saturating Ca2+, while S367 solvation energy controls the stability of the CaM–KCa3.1 complex and deactivation kinetics.\",\n      \"method\": \"Structural homology modeling based on rSK2 crystal structure, cross-linking mutagenesis (R362-K75 CaM), patch-clamp of mutant channels\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — structure-guided mutagenesis with cross-linking validation and functional patch-clamp readout, single lab\",\n      \"pmids\": [\"23797421\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PKA phosphorylates Ser334 in the CaM-binding C terminus of KCa3.1, reducing CaM binding and channel open probability. Mutating S334A abolishes PKA-dependent regulation. PKA activation through the adenosine A2a receptor similarly reduces KCa3.1 current and subsequent CRAC-mediated Ca2+ entry in microglia.\",\n      \"method\": \"Site-directed mutagenesis (S334A), CaM-affinity chromatography, single-channel patch-clamp, Ca2+ imaging in microglia and HEK293 cells\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis plus biochemical CaM-binding assay plus single-channel analysis, multiple orthogonal methods\",\n      \"pmids\": [\"25274816\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Plasma membrane KCa3.1 is internalized and targeted to lysosomes for degradation via a Rab7- and ESCRT-dependent pathway. TSG101 (ESCRT-I) co-immunoprecipitates with KCa3.1; dominant-negative TSG101, CHMP4, and VPS4 each inhibit KCa3.1 degradation rate.\",\n      \"method\": \"Immunofluorescence, electron microscopy, co-immunoprecipitation, dominant-negative constructs, siRNA knockdown of Rab7/ESCRT components\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple ESCRT components tested with reciprocal co-IP and dominant negatives, single lab\",\n      \"pmids\": [\"20720181\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Globotriaosylceramide (Gb3) triggers clathrin-dependent endocytosis and lysosomal degradation of endothelial KCa3.1. Knockdown of clathrin, Rab5, or lysosomal inhibitor treatment all rescue KCa3.1 expression and current; Rab5 knockdown also restores endothelium-dependent relaxation.\",\n      \"method\": \"Pharmacological inhibitors, siRNA knockdown of clathrin and Rab5, immunofluorescence, patch-clamp, vessel relaxation assay\",\n      \"journal\": \"Arteriosclerosis, thrombosis, and vascular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple genetic/pharmacological interventions with functional readout, single lab\",\n      \"pmids\": [\"24158513\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Three splice variants of KCNN4 (KCNN4a, KCNN4b, KCNN4c) are expressed in rat colon with tissue specificity: KCNN4a in smooth muscle, KCNN4b/c in epithelial cells. KCNN4b and KCNN4c encode basolateral and apical membrane proteins, respectively. KCNN4c, lacking the S2 transmembrane segment, requires coexpression of a large conductance K+ channel β-subunit for plasma membrane expression.\",\n      \"method\": \"RT-PCR, real-time qPCR, immunofluorescence, 86Rb efflux assay, heterologous coexpression\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — molecular cloning with functional expression and membrane localization, single lab\",\n      \"pmids\": [\"20445171\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"KCNN4/KCa3.1 is expressed in rat microglia and contributes to microglial activation, inducible nitric oxide synthase upregulation, nitric oxide and peroxynitrite production, and p38 MAPK activation (but not NF-κB), leading to neurotoxicity. TRAM-34 treatment of microglia (not neurons) reduces neuronal killing, and intraocular TRAM-34 reduces retinal ganglion cell degeneration after optic nerve transection.\",\n      \"method\": \"Selective pharmacological blockade (TRAM-34), Transwell co-culture assay, fluorescence-based NO/peroxynitrite assays, in vivo optic nerve injury model\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pathway dissection with selective inhibitor in vitro and in vivo, single lab, multiple readouts\",\n      \"pmids\": [\"17202491\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"KCa3.1 channels localize specifically to endothelial cell projections at myoendothelial gap junctions in mesenteric arteries, co-localizing with Na+/K+-ATPase α2/α3. PKA activation blocks KCa3.1 contribution to EDHF hyperpolarization independent of endothelial [Ca2+]i changes. KCa3.1-mediated hyperpolarization links to arterial relaxation primarily through Na+/K+-ATPase (K+ acting as EDHF), distinct from KCa2.3 pathways.\",\n      \"method\": \"Confocal z-stack immunofluorescence of pressurized arteries, pharmacological blockade (forskolin, TRAM-34), electrophysiology, Ca2+ imaging\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct subcellular localization linked to functional EDHF pathway dissection, single lab\",\n      \"pmids\": [\"18403729\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"KCa3.1 knockout CD4 T cells show decreased TCR-stimulated Ca2+ influx and IL-2 production. KCa3.1 loss impairs Ca2+ influx and cytokine production in Th1 and Th2 cells but not in T-regulatory or Th17 cells. KCa3.1-/- mice are protected from T-cell-mediated colitis in two IBD models.\",\n      \"method\": \"KCa3.1 knockout mouse, adoptive transfer colitis model, TNBS colitis model, Ca2+ flux measurements, cytokine assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined Ca2+ signaling and cytokine defects across multiple T cell subsets and two in vivo models\",\n      \"pmids\": [\"20080610\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"KCa3.1 localizes to the uropod of migrating activated human T lymphocytes (not the leading edge), and co-localizes with TRPM7. Blockade of KCa3.1 (TRAM-34) but not Kv1.3, CRAC, or TRPM4 inhibits T cell migration on ICAM-1 surfaces; Ca2+ oscillations are detected at the uropod where KCa3.1 and TRPM7 accumulate.\",\n      \"method\": \"Confocal microscopy on ICAM-1 polymer surfaces, Ca2+ imaging, pharmacological blockade, T cell migration assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization linked to migration function, multiple channel blockers as controls, single lab\",\n      \"pmids\": [\"22952790\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"KCa3.1 is selectively coupled to P2Y2 receptor (UTP) activation in rat microglia. KCa3.1 current is activated by Ca2+ entry through CRAC/Orai1 channels; both channels facilitate Ca2+ store refilling and are physically associated. Blocking either KCa3.1 or CRAC/Orai1 inhibits microglial migration stimulated by UTP.\",\n      \"method\": \"Whole-cell patch-clamp, Ca2+ imaging, pharmacological blockade, co-immunoprecipitation (implied close association), migration assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional coupling demonstrated electrophysiologically with pharmacological dissection plus migration readout, single lab\",\n      \"pmids\": [\"23620825\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Bradykinin raises [Ca2+]i in glioma cells, which activates KCa3.1 channels and Ca2+-dependent Cl- channels (ClC-3, activated via CaMKII) in a coordinated manner to drive a biphasic voltage response that mediates chemotactic migration. Inhibition of either KCa3.1 or ClC-3 abolishes bradykinin-induced chemotaxis and reduces tumor expansion in brain slices.\",\n      \"method\": \"Simultaneous fura-2 Ca2+ imaging and perforated patch-clamp, pharmacological blockade (TRAM-34, DIDS), CaMKII inhibition, shRNA knockdown of ClC-3, brain slice migration assay\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — simultaneous electrophysiology and Ca2+ imaging plus genetic knockdown and pharmacology, multiple orthogonal methods\",\n      \"pmids\": [\"23345219\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Kcnn4 is required for osteoclast and multinucleate giant cell (MGC) formation in rodents and humans. Genetic deletion of Kcnn4 reduces macrophage multinucleation through modulation of Ca2+ signaling, increases bone mass, and improves clinical outcome in arthritis models. Kcnn4 was identified as the most significantly trans-regulated gene in a macrophage multinucleation network.\",\n      \"method\": \"Systems genetics in rat macrophages, Kcnn4 knockout mouse (osteoclast/MGC formation, bone mass, arthritis model), Ca2+ signaling assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic deletion with defined cellular and in vivo phenotypes across multiple models\",\n      \"pmids\": [\"25131209\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"KCNN4 channels mediate EMT induced by PRL-3 in colorectal cancer by increasing intracellular Ca2+, activating CaM-kinase II and GSK-3β, increasing Snail expression, and downregulating E-cadherin. KCNN4 siRNA or TRAM-34 restores E-cadherin and inhibits Snail.\",\n      \"method\": \"siRNA knockdown, pharmacological blockade (TRAM-34), intracellular Ca2+ measurements, Western blot for CaMKII, GSK-3β, Snail, E-cadherin\",\n      \"journal\": \"Medical oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic and pharmacological loss-of-function with defined signaling cascade, single lab\",\n      \"pmids\": [\"23572150\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"GABRP physically interacts with KCNN4 (co-immunoprecipitation, proximity ligation assay) to induce Ca2+ entry, which activates NF-κB signaling and induces CXCL5 and CCL20 expression in pancreatic cancer cells, facilitating macrophage infiltration in a GABA-independent manner.\",\n      \"method\": \"Co-immunoprecipitation, proximity ligation assay, electrophysiology, NF-κB reporter assay, transwell and orthotopic xenograft models\",\n      \"journal\": \"Gut\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct protein interaction confirmed by two methods plus functional Ca2+/NF-κB signaling readout, single lab\",\n      \"pmids\": [\"30826748\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Junctophilin proteins (JPH3 and JPH4) tether a Cav1.3–RyR2–KCa3.1 tripartite complex at the plasma membrane–ER junction in CA1 hippocampal neurons. shRNA knockdown of JPH3/4 dissociates the complex and reduces the slow afterhyperpolarization current (IsAHP). Infusing JPH3/4 antibodies intracellularly also reduces IsAHP and spike accommodation, confirming functional coupling.\",\n      \"method\": \"dSTORM super-resolution microscopy, FRET imaging, shRNA knockdown, intracellular antibody infusion, whole-cell patch-clamp\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — super-resolution structural data plus FRET plus genetic and antibody disruption with electrophysiological functional readout, single lab but multiple orthogonal approaches\",\n      \"pmids\": [\"31461656\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"CaV1.3 channels exhibit long-duration calcium-dependent facilitation (L-CDF, up to 8 s) when coexpressed with densin and CaMKII, and this prolonged Ca2+ influx strongly activates KCa3.1 to generate a slow afterhyperpolarization tail current in CA1 pyramidal cells. CaV1.3 L-CDF and KCa3.1 coupling is reduced by CaMKII blockade and densin siRNA knockdown.\",\n      \"method\": \"Heterologous coexpression (tsA-201 cells), whole-cell patch-clamp, CaMKII inhibitor, siRNA knockdown of densin, pharmacological block of CaV1 (isradipine)\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional coupling demonstrated in two cell systems with pharmacological and genetic dissection, single lab\",\n      \"pmids\": [\"29038242\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"KCa3.1 is expressed in neuroblasts of the SVZ and RMS but absent in olfactory bulb neurons. Pharmacological inhibition of KCa3.1 prolongs the stationary phase of saltatory neuroblast migration, reducing migration speed by >50%. TRAM-34 injection in vivo significantly reduced the number of neuroblasts reaching the olfactory bulb. KCa3.1 activity depends on Ca2+ influx through TRPC channels (likely TRPC1).\",\n      \"method\": \"Patch-clamp of neuroblasts in situ, time-lapse confocal microscopy, pharmacological inhibition (TRAM-34, clotrimazole), in vivo injection of TRAM-34, immunolabeling\",\n      \"journal\": \"Cerebral cortex\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro electrophysiology and migration measurement confirmed in vivo, single lab\",\n      \"pmids\": [\"23585521\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PKA-mediated downregulation of KCa3.1 channels reduces the slow afterhyperpolarization (KCa-sAHP component) in epileptic hippocampal neurons, contributing to hyperexcitability. Acute application of PKA inhibitors reverses KCa3.1 downregulation and normalizes neuronal spike output.\",\n      \"method\": \"Whole-cell patch-clamp of rat CA1 neurons, PKA inhibitors, pilocarpine epilepsy model\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct electrophysiological dissection of sAHP components with pharmacological rescue, single lab\",\n      \"pmids\": [\"31672789\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PIEZO1 activation triggers Ca2+ influx that activates KCNN4 (KCa3.1), leading to K+ efflux and NLRP3 inflammasome activation. Myeloid-specific deletion of PIEZO1/2 protects mice from gouty arthritis. Pharmacological inhibition of KCNN4 alleviates autoinflammation in CAPS patient cells and CAPS-mutation mice.\",\n      \"method\": \"Genetic deletion (myeloid-specific Piezo1/2 KO), pharmacological PIEZO1 agonist (Yoda1), KCNN4 inhibition, inflammasome activation assays, Ca2+ flux measurements, in vivo arthritis model\",\n      \"journal\": \"Science immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mechanistic pathway (PIEZO1→Ca2+→KCNN4→K+ efflux→NLRP3) established with genetic and pharmacological tools in vitro and in vivo, multiple models\",\n      \"pmids\": [\"38134241\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"DSS potentiates NLRP3 inflammasome activation in macrophages by augmenting KCa3.1-mediated K+ efflux. Pharmacological blockade (TRAM-34) or genetic deletion of Kcnn4 attenuates NLRP3 inflammasome assembly in vivo and ameliorates DSS-induced colitis severity.\",\n      \"method\": \"Kcnn4 knockout mouse, TRAM-34 pharmacological blockade, inflammasome assembly assays, in vitro macrophage stimulation, DSS colitis model\",\n      \"journal\": \"Cellular & molecular immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic and pharmacological loss-of-function with defined inflammasome readout in vitro and in vivo, single lab\",\n      \"pmids\": [\"35799057\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Mutations in KCNN4 (Gardos channel) at a highly conserved residue are associated with hereditary xerocytosis. Both identified mutations are predicted to cause delayed channel inactivation, consistent with a gain-of-function mechanism causing erythrocyte dehydration.\",\n      \"method\": \"Whole-exome sequencing, segregation analysis in two HX kindreds, mutation effect prediction algorithms\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — genetic association with disease-linked mutations but no direct functional channel assay performed in this study\",\n      \"pmids\": [\"26198474\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"IL-4 upregulates KCNN4 mRNA and KCa3.1 current in alternative-activated rat microglia via the type I IL-4 receptor, requiring JAK3, Ras/MEK/ERK signaling, and the AP-1 transcription factor (not JAK2, STAT6, or PI3K). The increased KCa3.1 is required for IL-4-enhanced microglial migration.\",\n      \"method\": \"Real-time PCR, patch-clamp, protein synthesis inhibition, kinase inhibitor panel, migration assay (TRAM-34 blockade)\",\n      \"journal\": \"Frontiers in cellular neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — signaling pathway dissected with inhibitor panel plus functional migration readout, single lab\",\n      \"pmids\": [\"25071444\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PKG elevates KCa3.1 current in microglia through a ROS-dependent, CaMKII-mediated pathway; H2O2 mimics and ROS scavengers/CaMKII inhibitors block the PKG effect. However, direct application of cGMP, PKG, or H2O2 to inside-out patches does not affect single-channel activity or Ca2+ dependence, indicating the regulation is indirect and requires intact intracellular signaling.\",\n      \"method\": \"Perforated-patch whole-cell recordings in microglia, inside-out single-channel patch-clamp in HEK293, selective PKG inhibitor (KT5823), ROS scavenger, CaMKII inhibitor, H2O2\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — intact-cell and single-channel dissection with multiple selective inhibitors, single lab\",\n      \"pmids\": [\"25904916\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Orai1 co-immunoprecipitates with KCa3.1 (but not Orai2) when coexpressed in HEK293 cells, and both channels co-localize at the plasma membrane. In human lung mast cells, KCa3.1 activation is highly dependent on Ca2+ influx through Orai1; Orai1 E106Q dominant-negative mutant ablates KCa3.1 currents.\",\n      \"method\": \"Co-immunoprecipitation, confocal co-localization, dominant-negative Orai1 E106Q mutant, patch-clamp\",\n      \"journal\": \"Cell communication and signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct protein interaction plus functional epistasis with dominant negative, single lab\",\n      \"pmids\": [\"26177720\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"KCa3.1 co-immunoprecipitates and co-distributes with β1-integrin in alveolar epithelial cells on fibronectin matrix. KCa3.1 inhibition/silencing impairs fibronectin-stimulated wound healing, cell migration, and proliferation. KCa3.1 and TRPC4 have additive inhibitory effects on alveolar repair.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence co-localization, siRNA knockdown, wound-healing assays, KCa3.1 blocker\",\n      \"journal\": \"Respiratory research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct protein interaction plus functional loss-of-function with migration readout, single lab\",\n      \"pmids\": [\"26335442\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Adenosine selectively inhibits KCa3.1 (not Kv1.3 or TRPM7) in activated human T cells via A2A receptor and cAMP/PKAI signaling pathway. This inhibition reduces T cell motility on ICAM-1 surfaces and IL-2 secretion; the adenosine effect on migration is abolished by pre-exposure to TRAM-34, placing KCa3.1 downstream of A2A/PKAI.\",\n      \"method\": \"Patch-clamp, selective receptor agonists/antagonists, adenylyl cyclase and PKAI inhibitors, T cell migration assay on ICAM-1 surfaces\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological pathway dissection with multiple selective tools plus epistasis via channel blockade, single lab\",\n      \"pmids\": [\"24227782\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"KCa3.1 is present in the inner mitochondrial membrane (mitoKCa3.1) in cancer cells. Mitochondria-targeted TRAM-34 derivatives that block mitoKCa3.1 induce mitochondrial ROS release, membrane depolarization, and mitochondrial network fragmentation, triggering cancer cell death. Plasma-membrane-impermeant Maurotoxin has no effect, confirming the mitochondrial channel is the relevant target. At sub-lethal concentrations, mitoKCa3.1 inhibition reduces cancer cell migration via NF-κB activation, BNIP-3 downregulation, and CDC-42-mediated cytoskeletal reorganization.\",\n      \"method\": \"Mitochondria-targeted drug synthesis, Maurotoxin (membrane-impermeant blocker), mitochondrial membrane potential assay, ROS measurement, NF-κB reporter, BNIP-3/CDC-42 manipulation, orthotopic in vivo cancer models\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — compartment-specific pharmacological dissection with mechanistic pathway follow-up and in vivo confirmation, single lab\",\n      \"pmids\": [\"36539400\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"NOX5-derived ROS are required for bFGF-induced upregulation of KCNN4 mRNA and protein in porcine coronary smooth muscle cells. NOX5 knockdown prevents KCNN4 upregulation and CSMC migration; the mechanism involves NOX5→superoxide→AP-1 transcriptional activation.\",\n      \"method\": \"siRNA knockdown of individual NOX isoforms, dihydroethidium fluorography, AP-1 luciferase reporter, qRT-PCR, immunohistochemistry, patch-clamp, migration assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — selective NOX5 knockdown with mechanistic AP-1 reporter and functional migration readout, single lab\",\n      \"pmids\": [\"25144362\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"KCa3.1 regulates Ca2+-dependent NFATc1 expression during osteoclastogenesis via the CaMKIV/CREB/c-fos pathway. KCa3.1-/- and TRAM-34 treatment reduce RANKL-induced Ca2+ transient amplitudes (~50%), prevent CaMKIV phosphorylation, decrease CREB and c-fos, and reduce NFATc1 expression and osteoclast formation.\",\n      \"method\": \"KCa3.1 knockout BMMs, TRAM-34, live-cell Ca2+ imaging, Western blot (CaMKIV, CREB, c-fos, NFATc1), osteoclast differentiation assay\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic and pharmacological KO/inhibition with defined Ca2+ signaling cascade, single lab\",\n      \"pmids\": [\"29246953\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KCNN4/KCa3.1 is an intermediate-conductance, voltage-independent K+ channel gated by Ca2+-bound calmodulin constitutively associated with its C-terminal CaM-binding domain; channel activity is uniquely regulated by histidine 358 phosphorylation (activated by NDPK-B, inhibited by PHPT-1) through a mechanism that relieves copper-mediated inhibition, and is further modulated by PKA (inhibitory, via Ser334 reducing CaM binding), PKG/ROS/CaMKII, AMPK-γ1 interaction, and PI(3)P via a 14-aa C-terminal motif; at the plasma membrane it couples functionally to Orai1/CRAC channels, is scaffolded to Cav1.3–RyR2 complexes by junctophilins in neurons, and is targeted for lysosomal degradation via clathrin/Rab7/ESCRT machinery; the channel drives K+ efflux to hyperpolarize the membrane and amplify Ca2+ influx, thereby regulating T cell activation, microglia-mediated neuroinflammation (via p38 MAPK), macrophage multinucleation/osteoclastogenesis (via CaMKIV/NFATc1), NLRP3 inflammasome activation downstream of PIEZO1, erythrocyte volume homeostasis (Gardos channel), and cell migration across many cell types including T lymphocytes, microglia, glioma, mast cells, and neuroblasts.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"KCNN4 (KCa3.1/hSK4/hKCa4) is an intermediate-conductance, voltage-independent, inwardly rectifying Ca2+-activated K+ channel that drives K+ efflux to hyperpolarize the membrane and thereby amplify Ca2+ influx in nonexcitable cells, coupling cellular Ca2+ signaling to immune activation, cell volume control, and migration [#1, #7, #17]. The channel has no intrinsic Ca2+-binding sites; instead it is constitutively associated with calmodulin at a C-terminal CaM-binding domain, and Ca2+-loaded CaM N-lobe binding gates the channel through defined residues that set open probability and deactivation kinetics [#2, #10]. Channel activity is set by a distinctive C-terminal regulatory hub: NDPK-B directly phosphorylates histidine 358 to activate the channel by relieving copper-mediated inhibition, while protein histidine phosphatase PHPT-1 dephosphorylates H358 to inhibit it, and PKA phosphorylation of Ser334 reduces CaM binding and open probability [#3, #4, #6, #11]. Additional inputs converge on the C terminus, including direct AMPK-\\u03b31 binding that inhibits the channel and a 14-amino-acid motif conferring PI(3)P-dependent activation [#5, #9]. At the plasma membrane the channel is functionally coupled to Orai1/CRAC channels that supply its activating Ca2+ and is scaffolded by junctophilins into Cav1.3\\u2013RyR2 complexes to generate the neuronal slow afterhyperpolarization current [#24, #33]; surface levels are controlled by clathrin/Rab5 endocytosis and Rab7/ESCRT-dependent lysosomal degradation [#12, #13]. Through this Ca2+-amplifying role KCa3.1 governs CD4 T-cell activation and cytokine production, microglial neuroinflammation via p38 MAPK, osteoclast/multinucleate-giant-cell formation via CaMKIV/NFATc1, and NLRP3 inflammasome activation downstream of PIEZO1-mediated Ca2+ entry [#15, #17, #28, #38]. In erythrocytes KCa3.1 is the Gardos channel that mediates K+ efflux for volume homeostasis, and gain-of-function KCNN4 mutations are associated with hereditary xerocytosis [#7, #30].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Established the molecular identity of an intermediate-conductance, voltage-independent Ca2+-activated K+ channel with very high Ca2+ sensitivity, defining a distinct channel class enriched in nonexcitable tissues.\",\n      \"evidence\": \"Heterologous expression in CHO/HEK293 cells with patch-clamp and pharmacological profiling\",\n      \"pmids\": [\"9380751\", \"9407042\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the Ca2+-sensing mechanism\", \"No structural basis for gating\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Resolved how a channel lacking intrinsic Ca2+ sites senses Ca2+ \\u2014 a constitutively bound calmodulin at the proximal C terminus confers Ca2+ gating and links the channel to T-cell proliferation and volume regulation.\",\n      \"evidence\": \"Deletion mutagenesis mapping of the CaM-binding domain with patch-clamp and functional assays\",\n      \"pmids\": [\"10329683\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define which CaM residues drive gating\", \"Distal C-terminal requirement unexplained\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined the structural determinants of CaM-dependent gating, identifying specific CaM-binding-domain residues controlling open probability versus complex stability/deactivation.\",\n      \"evidence\": \"Structure-guided cross-linking mutagenesis with patch-clamp of mutant channels\",\n      \"pmids\": [\"23797421\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Based on homology modeling, not a KCa3.1 structure\", \"Single lab\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identified a 14-aa C-terminal motif conferring PI(3)P-dependent activation, implying recruitment of an accessory regulatory subunit required for Ca2+ gating.\",\n      \"evidence\": \"Chimeric KCa3.1/KCa2.3 channels and site-directed mutagenesis with patch-clamp\",\n      \"pmids\": [\"16251351\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Proposed accessory subunit not identified\", \"Indirect regulation mechanism unresolved\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Discovered histidine-358 phosphorylation as a unique activating regulatory mechanism, with NDPK-B directly binding and phosphorylating the C terminus to enable channel-driven Ca2+ influx and T-cell activation.\",\n      \"evidence\": \"Co-IP, in vitro kinase assay, H358 mutagenesis, T-cell patch-clamp and siRNA\",\n      \"pmids\": [\"17157250\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the opposing phosphatase\", \"Molecular consequence of H358 phosphorylation on gating unclear\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Completed the histidine phospho-switch by identifying PHPT-1 as the phosphatase that dephosphorylates H358 to inhibit the channel, establishing reciprocal kinase/phosphatase control.\",\n      \"evidence\": \"Co-IP, phosphatase-dead mutant, siRNA, patch-clamp and Ca2+ imaging\",\n      \"pmids\": [\"18796614\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not explain why H358 phosphorylation gates the channel\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Provided the mechanistic basis of the H358 switch \\u2014 phosphorylation activates the channel by antagonizing copper-mediated inhibition, linking intracellular copper status to T-cell Ca2+ signaling.\",\n      \"evidence\": \"In vitro copper inhibition assays, H358 mutagenesis, patch-clamp and Ca2+ flux in copper-deficient T cells\",\n      \"pmids\": [\"27542194\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Copper-binding site on the channel not defined\", \"Physiological source of inhibitory copper unclear\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Identified additional C-terminal regulatory inputs: direct AMPK-\\u03b31 binding inhibits the channel, coupling metabolic state to K+ conductance in epithelia.\",\n      \"evidence\": \"Two-hybrid, pull-down, endogenous co-IP, inside-out patch-clamp and Ussing chamber currents\",\n      \"pmids\": [\"19052260\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether AMPK phosphorylates the channel directly not resolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined PKA inhibitory regulation through Ser334 phosphorylation that reduces CaM binding and open probability, linking GPCR/cAMP signaling to channel downregulation.\",\n      \"evidence\": \"S334A mutagenesis, CaM-affinity chromatography, single-channel patch-clamp, Ca2+ imaging in microglia\",\n      \"pmids\": [\"25274816\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Integration of PKA, NDPK-B/PHPT-1, and AMPK inputs not reconciled\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Demonstrated in vivo physiological roles via clean genetic deletion: Kcnn4 loss abolishes IK in red cells and T lymphocytes and impairs their volume regulation, while sparing salivary secretion, establishing cell-type-specific requirement.\",\n      \"evidence\": \"Kcnn4 knockout mouse with patch-clamp, K+ permeability, and fluid secretion assays\",\n      \"pmids\": [\"15347667\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address inflammatory or migratory roles\", \"Compensation in unaffected tissues not explained\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Identified KCa3.1 as the long-sought erythrocyte Gardos channel, providing molecular identity to a classic red-cell K+ pathway.\",\n      \"evidence\": \"RT-PCR, Northern/Western of RBC ghosts, inside-out patch-clamp, heterologous recapitulation of native channel behavior\",\n      \"pmids\": [\"12773623\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address disease mutations affecting Gardos function\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Linked KCNN4 to human disease, associating conserved-residue mutations with hereditary xerocytosis via a predicted gain-of-function (delayed inactivation) causing erythrocyte dehydration.\",\n      \"evidence\": \"Whole-exome sequencing, segregation in two kindreds, mutation-effect prediction\",\n      \"pmids\": [\"26198474\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No direct functional channel assay performed in this study\", \"Gating defect inferred computationally only\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Established the immunological function of the channel in adaptive immunity: KCa3.1 supports TCR-driven Ca2+ influx and cytokine output selectively in Th1/Th2 cells and is required for T-cell-mediated colitis.\",\n      \"evidence\": \"Knockout CD4 T cells, Ca2+ flux/cytokine assays, two in vivo colitis models\",\n      \"pmids\": [\"20080610\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of subset selectivity (Th1/2 vs Treg/Th17) not defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Showed plasma-membrane KCa3.1 is functionally coupled to Orai1/CRAC channels that supply the Ca2+ for channel activation, integrating store-operated entry with K+ efflux to sustain Ca2+ signaling and migration.\",\n      \"evidence\": \"Co-IP, co-localization, Orai1 E106Q dominant negative, patch-clamp in mast cells and microglia\",\n      \"pmids\": [\"26177720\", \"23620825\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether the KCa3.1\\u2013Orai1 association is direct vs scaffolded not resolved\", \"Stoichiometry of the functional coupling unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined surface-level control of the channel through clathrin/Rab5 endocytosis and Rab7/ESCRT-dependent lysosomal degradation, a pathway exploited by Gb3 to suppress endothelial KCa3.1 and impair vasorelaxation.\",\n      \"evidence\": \"siRNA/dominant-negative of clathrin, Rab5, Rab7, TSG101/CHMP4/VPS4, co-IP, imaging, EM, vessel relaxation assay\",\n      \"pmids\": [\"20720181\", \"24158513\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Trafficking signals on KCa3.1 directing endocytosis not mapped\", \"Regulation of degradation rate by upstream signals unclear\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Revealed neuronal scaffolding: junctophilins JPH3/4 tether a Cav1.3\\u2013RyR2\\u2013KCa3.1 tripartite complex at ER\\u2013PM junctions in hippocampal neurons, and densin/CaMKII-prolonged Cav1.3 Ca2+ influx drives KCa3.1 to generate the slow afterhyperpolarization.\",\n      \"evidence\": \"dSTORM/FRET, shRNA, intracellular antibody infusion, heterologous coexpression, whole-cell patch-clamp\",\n      \"pmids\": [\"31461656\", \"29038242\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct KCa3.1\\u2013junctophilin contact not biochemically mapped\", \"Generality across neuron types untested\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Established KCa3.1 as a regulator of myeloid cell fusion and bone biology, where it controls Ca2+-dependent CaMKIV/CREB/c-fos/NFATc1 signaling driving osteoclast and multinucleate-giant-cell formation.\",\n      \"evidence\": \"Systems genetics, Kcnn4 knockout mouse, osteoclast/MGC and arthritis models, Ca2+ imaging, signaling Western blots\",\n      \"pmids\": [\"25131209\", \"29246953\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How channel activity is gated specifically during fusion not defined\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Implicated the channel in CNS innate immunity, showing microglial KCa3.1 drives activation, iNOS/NO/peroxynitrite production, and p38 MAPK-dependent neurotoxicity, with KCa3.1 expression itself shaped by IL-4 (JAK3/Ras/MEK/ERK/AP-1) and PKG/ROS/CaMKII inputs.\",\n      \"evidence\": \"TRAM-34 blockade, co-culture, NO/peroxynitrite assays, in vivo optic nerve injury, kinase-inhibitor panels, perforated/inside-out patch-clamp\",\n      \"pmids\": [\"17202491\", \"25071444\", \"25904916\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct molecular link between K+ efflux and p38 activation unresolved\", \"PKG/ROS effect is indirect with no defined channel-proximal effector\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Placed KCa3.1 within mechanotransductive innate immune signaling, where PIEZO1-triggered Ca2+ influx activates the channel and the resulting K+ efflux drives NLRP3 inflammasome activation in gout and CAPS models.\",\n      \"evidence\": \"Myeloid Piezo1/2 KO, Yoda1, KCNN4 inhibition, inflammasome and Ca2+ assays, in vivo arthritis models\",\n      \"pmids\": [\"38134241\", \"35799057\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether K+ efflux directly senses or merely permits NLRP3 assembly not dissected\", \"Coupling of PIEZO1 Ca2+ entry to channel activation not biochemically mapped\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified a non-canonical mitochondrial pool (mitoKCa3.1) in the inner membrane of cancer cells whose inhibition triggers ROS, depolarization, and death, expanding the channel's role beyond the plasma membrane.\",\n      \"evidence\": \"Mitochondria-targeted vs impermeant blockers, membrane-potential/ROS assays, NF-\\u03baB/BNIP-3/CDC-42 manipulation, orthotopic models\",\n      \"pmids\": [\"36539400\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How the channel is imported/inserted into the inner mitochondrial membrane unknown\", \"Single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the multiple convergent C-terminal regulatory inputs (H358 phospho-switch/copper, Ser334/PKA, AMPK-\\u03b31, PI(3)P, CaM) are integrated in real time on a single channel, and the structural basis of gating, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No experimental KCa3.1 structure in the corpus\", \"Crosstalk and hierarchy among regulatory inputs undefined\", \"Mechanism of mitochondrial targeting unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 1, 7]},\n      {\"term_id\": \"GO:0005216\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [12, 16, 18, 33]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [36]},\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [12, 13]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [17, 28, 38]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3, 19, 33]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [12, 13]}\n    ],\n    \"complexes\": [\n      \"Cav1.3-RyR2-KCa3.1 junctophilin-tethered complex\",\n      \"KCa3.1-calmodulin complex\"\n    ],\n    \"partners\": [\n      \"CALM1\",\n      \"NME2\",\n      \"PHPT1\",\n      \"PRKAA1/PRKAG1\",\n      \"ORAI1\",\n      \"JPH3\",\n      \"JPH4\",\n      \"GABRP\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}