{"gene":"SLC12A2","run_date":"2026-04-28T20:42:07","timeline":{"discoveries":[{"year":2019,"finding":"Cryo-EM structure of zebrafish NKCC1 defines the architecture of the CCC family, reveals the ion-translocation pathway, ion-binding sites (Na+, K+, 2Cl-), key residues for transport activity, and how cytosolic and transmembrane domains communicate; structural analyses combined with functional characterizations and computational studies establish mechanisms of ion selectivity, coupling, and translocation.","method":"Single-particle cryo-EM, functional transport assays, computational (MD) simulations, mutagenesis","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structure + functional validation + computational studies in one study","pmids":["31367042"],"is_preprint":false},{"year":2020,"finding":"Cryo-EM structure of human NKCC1 in a partially loaded, inward-open state reveals a dimeric assembly; TM1 and TM6 helices break α-helical geometry at ion-binding sites; multiple extracellular entryways and intracellular exits are identified, suggesting K+, Na+, and Cl- may traverse along distinct routes.","method":"Single-particle cryo-EM","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 — high-resolution cryo-EM structure of human protein","pmids":["32081947"],"is_preprint":false},{"year":2021,"finding":"Cryo-EM structures of human NKCC1 and mouse KCC2 at near-atomic resolution identify essential residues for ion transport and reveal mechanisms by which N-terminal phosphorylation regulates transport activity.","method":"Cryo-EM, computational analysis, functional characterization","journal":"Communications biology","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM + functional + computational in one study","pmids":["33597714"],"is_preprint":false},{"year":2022,"finding":"Cryo-EM structure of NKCC1 in an outward-facing conformation shows bumetanide wedged into a pocket in the extracellular ion translocation pathway; comparison with inward-facing structures defines the translocation pathway and conformational changes for ion translocation; an N-terminal phosphoregulatory domain interacts with the C-terminal domain, suggesting (de)phosphorylation regulates NKCC1 by tuning this domain association.","method":"Single-particle cryo-EM, functional studies, mutagenesis","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structures in multiple conformations + functional validation","pmids":["35585053"],"is_preprint":false},{"year":2022,"finding":"2.6 Å cryo-EM structure of human NKCC1 in substrate-loaded, occluded inward-facing state reveals Cl- binding at Cl1 site bridges scaffold and bundle domains via K+; Cl- at Cl2 site plays a structural role analogous to conserved glutamate in SLC6 transporters; a putative Na+ release pathway along TM5 coupled to the Cl2 site is identified and supported by functional studies and MD simulations.","method":"Cryo-EM (2.6 Å), functional assays in mammalian cells, MD simulations","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 — high-resolution structure + functional + computational, orthogonal methods","pmids":["36239040"],"is_preprint":false},{"year":2022,"finding":"Four cryo-EM structures of human NKCC1 (apo and bound to bumetanide or furosemide) reveal two drug-binding sites at transmembrane and cytosolic C-terminal domains; an inhibition mechanism involving coupled movement between cytosolic and transmembrane domains is delineated; the C-terminal domain is implicated in long-range conformational coupling.","method":"Single-particle cryo-EM, functional studies","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1 — multiple structures with and without inhibitors + functional studies","pmids":["36306358"],"is_preprint":false},{"year":2003,"finding":"PASK/SPAK kinase directly phosphorylates two regulatory threonines on the N-terminal domain of NKCC1 and activates cotransport; dominant-negative PASK markedly reduces NKCC1 phosphorylation and activity; co-immunoprecipitation confirms constitutive PASK–NKCC1 binding in HEK cells; phosphatase inhibitor calyculin A rescues activity, indicating kinase/phosphatase balance controls NKCC1.","method":"Dominant-negative overexpression, co-immunoprecipitation, 32Pi phosphorylation assay, ion transport assay (86Rb uptake)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP + functional assay + phosphorylation assay, multiple orthogonal methods","pmids":["12740379"],"is_preprint":false},{"year":2012,"finding":"SPAK and OSR1 are essential upstream kinases for NKCC1 phosphorylation and activation; double-knockin ES cells where SPAK/OSR1 cannot be activated by WNK1 show complete loss of NKCC1 phosphorylation and activation; SPAK/OSR1 activity also significantly influences WNK kinase activity (feedback).","method":"Double-knockin ES cells (loss-of-function genetic approach), phospho-specific antibodies, ion transport assay","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 2 — clean genetic knockin with defined molecular and functional phenotype, replicated across conditions","pmids":["22032326"],"is_preprint":false},{"year":2012,"finding":"Estradiol increases protein levels of SPAK and OSR1 in the neonatal hypothalamus in a transcription-dependent manner; SPAK/OSR1 upregulation mediates estradiol-enhanced NKCC1 phosphorylation; antisense knockdown of SPAK (and to a lesser extent OSR1) blocks estradiol-enhanced NKCC1 phosphorylation and GABA-induced Ca2+ influx.","method":"In vivo antisense oligonucleotide knockdown, Western blot with phospho-specific antibodies, calcium imaging","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — in vivo knockdown + phosphorylation assay + functional Ca2+ imaging, multiple methods","pmids":["22238094"],"is_preprint":false},{"year":2011,"finding":"IL-6 autocrine signaling in axotomized sensory neurons activates NKCC1 via JAK signaling and IL-6 receptor upregulation, leading to NKCC1 phosphorylation and Cl- accumulation that supports neurite regrowth; IL-6 neutralization or IL-6-/- mice prevent NKCC1 phosphorylation and Cl- accumulation.","method":"IL-6 knockout mice, receptor-blocking antibodies, pharmacological JAK inhibition, functional Cl- accumulation assay, neurite growth assay","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — KO mice + pharmacological + functional assays, multiple orthogonal approaches","pmids":["21940443"],"is_preprint":false},{"year":1999,"finding":"Point mutations in Slc12a2 (encoding basolateral Na-K-Cl cotransporter NKCC1) cause deafness and abnormal endolymph production in sy and sy(ns) mice, establishing NKCC1 as an essential component of K+ recycling in the cochlea.","method":"Positional cloning, mutation identification, mouse phenotyping (deaf mutant)","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 — positional cloning with in vivo loss-of-function phenotype","pmids":["10401008"],"is_preprint":false},{"year":2009,"finding":"Loss-of-function mutations in zebrafish nkcc1 (slc12a2) cause collapse of the otic vesicle (endolymph fluid loss) and over-inflation of the swim bladder, establishing NKCC1 as required for endolymph volume regulation; morpholino rescue of splicing defect ameliorates ear volume collapse.","method":"Forward genetics (ENU mutagenesis), Sanger sequencing, morpholino rescue","journal":"Development","confidence":"High","confidence_rationale":"Tier 2 — in vivo genetic loss-of-function with specific fluid-homeostasis phenotype, morpholino rescue","pmids":["19633174"],"is_preprint":false},{"year":1997,"finding":"BSC2/NKCC1 protein localizes to the apical surface of choroid plexus epithelium and to neuronal cell bodies/dendrites; apical localization in choroid plexus is confirmed by 86Rb+ uptake in cells grown on permeable filters and confocal microscopy, suggesting a role in CSF K+ homeostasis.","method":"Immunocytochemistry, confocal microscopy, 86Rb+ transport assay on polarized epithelial cells","journal":"The American journal of physiology","confidence":"High","confidence_rationale":"Tier 2 — direct localization by immunofluorescence + functional 86Rb transport, multiple methods","pmids":["9038823"],"is_preprint":false},{"year":2021,"finding":"NKCC1 in the choroid plexus mediates CSF K+ clearance during mouse early postnatal development; overexpression of NKCC1 in choroid plexus increases CSF K+ clearance and reduces circulating CSF; in an obstructive hydrocephalus model, choroid plexus-specific NKCC1 overexpression reduces ventriculomegaly.","method":"AAV-mediated gene overexpression in choroid plexus, CSF [K+] measurement, MRI ventriculometry, mouse hydrocephalus model","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — in vivo gain-of-function with specific mechanistic and volumetric readouts","pmids":["33469018"],"is_preprint":false},{"year":2023,"finding":"Intraventricular blood increases CSF [K+] and triggers cytosolic calcium activity in choroid plexus epithelial cells, followed by NKCC1 activation; AAV-mediated ChP-targeted NKCC1 overexpression prevents blood-induced ventriculomegaly; phosphodeficient NKCC1-NT51 mutant fails to mitigate ventriculomegaly, demonstrating that phosphorylation-dependent NKCC1 activation is required for CSF clearance.","method":"AAV gene delivery, phosphodeficient mutant (loss-of-function), calcium imaging, ventriculometry, CSF K+ measurement","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 1-2 — phosphodeficient mutant + AAV overexpression + mechanistic imaging, multiple orthogonal methods","pmids":["36893755"],"is_preprint":false},{"year":2016,"finding":"A gain-of-function missense variant p.Y199C in the N-terminal regulatory domain of SLC12A2/NKCC1 increases Cl--dependent, bumetanide-sensitive cotransporter activity even under hypotonicity (conditions where wild-type is normally silent), identified in human schizophrenia patients.","method":"Xenopus oocyte ion transport assay (Cl--dependent 86Rb uptake), patient sequencing","journal":"Journal of psychiatric research","confidence":"High","confidence_rationale":"Tier 1 — functional reconstitution in Xenopus oocytes with mutant vs. wild-type comparison","pmids":["26955005"],"is_preprint":false},{"year":2020,"finding":"De novo SLC12A2 mutations identified in children with neurodevelopmental disorders and sensorineural hearing loss all reduce cotransporter function when expressed in Xenopus laevis oocytes, establishing loss-of-function as the pathogenic mechanism.","method":"Xenopus oocyte expression assay, trio exome sequencing","journal":"Brain","confidence":"High","confidence_rationale":"Tier 1 — functional assay in Xenopus oocytes for multiple variants, direct mechanistic link","pmids":["32658972"],"is_preprint":false},{"year":2017,"finding":"NKCC1 interacts with actin-regulatory protein Cofilin-1 and regulates its membrane localization; NKCC1 knockdown decreases F-actin content and reduces active RhoA and Rac1, thereby decreasing glioblastoma cell migration.","method":"Co-immunoprecipitation (NKCC1–Cofilin-1 interaction), siRNA knockdown, F-actin staining, Rho-GTPase activity assay, in vitro migration assay, intracranial mouse model","journal":"EBioMedicine","confidence":"High","confidence_rationale":"Tier 2 — Co-IP + KD + multiple functional readouts + in vivo validation","pmids":["28679472"],"is_preprint":false},{"year":2019,"finding":"NKCC1 (SLC12A2) is present in a complex with the leucine transporter LAT1; NKCC1 depletion enhances LAT1 activity, Akt and Erk activation, and mTORC1 activation, reduces intracellular Na+ and cell volume/mass, and stimulates cell proliferation, establishing NKCC1 as a suppressor of mTORC1 that links cell volume to cell mass regulation.","method":"Co-immunoprecipitation (NKCC1–LAT1 complex), NKCC1 siRNA/CRISPR deletion, mTORC1 signaling assays, ion flux measurements, colonic organoids, mouse colon KO","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — Co-IP + multiple KO/KD models (cells, organoids, mouse) + pathway readout","pmids":["31067471"],"is_preprint":false},{"year":2012,"finding":"NKCC1 knockdown in neonatal mouse subventricular zone neural progenitor cells reduces GABA-induced depolarization and Ca2+ responses, decreases proliferative Ki67+ progenitors by ~70%, reduces newborn neuron density by ~60%, and causes truncated dendritic arborization; GABAA agonist pentobarbital rescues proliferation, confirming NKCC1 acts via GABAA receptor depolarization.","method":"In vivo electroporation of shRNA, Ki67 immunostaining, calcium imaging, dendritic morphology analysis, pharmacological rescue","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — in vivo KD with multiple cellular phenotype readouts and pharmacological rescue","pmids":["23015452"],"is_preprint":false},{"year":2017,"finding":"NKCC1 promotes GABA-mediated depolarization in Cajal-Retzius neurons; genetic deletion or pharmacological blockade of NKCC1 in vitro and in vivo rescues Cajal-Retzius neurons from apoptosis via blockade of p75NTR receptor signaling pathway.","method":"NKCC1 genetic knockout mice, in vitro pharmacological blockade (bumetanide), p75NTR pathway analysis, apoptosis assays","journal":"Cerebral cortex","confidence":"High","confidence_rationale":"Tier 2 — KO + pharmacological + pathway placement (p75NTR), replicated in vitro and in vivo","pmids":["26819276"],"is_preprint":false},{"year":2008,"finding":"AVP-induced cell swelling in inner medullary collecting duct requires basolateral NaCl uptake via NKCC1; bumetanide abolishes AVP-induced cell height increase; NKCC1 knockout mice lack AVP-induced cell swelling; myosin II also contributes via actin cytoskeleton reorganization.","method":"NKCC1 knockout mice, quantitative video microscopy, bumetanide pharmacology, immunocytochemistry, blebbistatin inhibition","journal":"American journal of physiology. Renal physiology","confidence":"High","confidence_rationale":"Tier 2 — KO mice + pharmacology + direct morphometry, multiple approaches","pmids":["18417545"],"is_preprint":false},{"year":2002,"finding":"NKCC1 is expressed on the basolateral membrane of mammary epithelial cells; NKCC1-/- mice show delayed ductal outgrowth and increased branching morphogenesis during virgin development in a cell-autonomous manner (demonstrated by transplantation); loss of NKCC1 impairs lactation function.","method":"NKCC1 knockout mice, mammary gland transplantation (cell-autonomous test), immunolocalization","journal":"Molecular endocrinology","confidence":"High","confidence_rationale":"Tier 2 — KO + transplantation (cell-autonomous) + localization","pmids":["12040017"],"is_preprint":false},{"year":2005,"finding":"NKCC1 is expressed on the basolateral membrane of secretory coil cells of sweat glands (rat, mouse, human) and is responsible for bumetanide-sensitive NaCl secretion in sweat glands; NKCC2 is absent; basolateral NKCC1 mediates NaCl entry for fluid secretion.","method":"RT-PCR, Western blot, immunoperoxidase, immunoelectron microscopy","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 2 — immunoelectron microscopy confirming basolateral membrane localization + functional transport data","pmids":["15843440"],"is_preprint":false},{"year":2005,"finding":"NKCC1 in juxtaglomerular granular cells directly suppresses basal renin release; furosemide stimulates renin release from wild-type JG cells (measured by patch-clamp membrane capacitance and primary culture assay) but not from NKCC1-deficient cells; NKCC1-/- mice have elevated plasma renin.","method":"NKCC1 knockout mice, patch-clamp (membrane capacitance), primary JG cell culture renin release assay","journal":"American journal of physiology. Renal physiology","confidence":"High","confidence_rationale":"Tier 2 — KO mice + electrophysiology + cell culture functional assay","pmids":["16106034"],"is_preprint":false},{"year":2001,"finding":"NKCC1 on the basolateral membrane is required for large UTP-stimulated anion secretory responses in mouse airways; NKCC1-/- neonatal trachea has reduced basal short-circuit current; HCO3- secretion compensates for reduced Cl- secretion in knockout airways.","method":"NKCC1 knockout mice, Ussing chamber ion transport assay, bumetanide pharmacology","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 2 — KO mice + Ussing chamber functional assay","pmids":["11443061"],"is_preprint":false},{"year":1997,"finding":"The Slc12a2 gene encodes a cotransporter with 27 exons and tissue-specific transcription initiation; a brain-specific alternatively spliced variant lacking exon 21 (encoding 16 amino acids of the C-terminal tail) loses the single PKA consensus phosphorylation site, suggesting splice-variant-specific regulation.","method":"Genomic cloning, RNase protection assay, primer extension, luciferase reporter transfection, RT-PCR of splice variants","journal":"The American journal of physiology","confidence":"Medium","confidence_rationale":"Tier 2 — molecular cloning with functional promoter assay; splice-variant mechanism inferred rather than directly tested","pmids":["9357771"],"is_preprint":false},{"year":2012,"finding":"NKCC1 upregulation in hypothalamic paraventricular nucleus presympathetic neurons causes depolarizing shift in GABA reversal potential and disrupts GABAergic inhibition in spontaneously hypertensive rats; NKCC1 inhibition normalizes EGABA; increased N-glycosylation of NKCC1 contributes to its enhanced activity in hypertension.","method":"Gramicidin perforated-patch clamp (EGABA measurement), NKCC1 inhibitor bumetanide, N-glycosylation inhibition, Western blot","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — electrophysiology + pharmacology + glycosylation manipulation, multiple orthogonal methods","pmids":["22723696"],"is_preprint":false},{"year":2013,"finding":"Aldosterone upregulates NKCC1 protein expression rapidly and independently of mRNA changes, by increasing protein stability (reducing ubiquitination) via mineralocorticoid receptors; proteasome inhibitor MG132 and cycloheximide experiments confirm post-translational stabilization mechanism.","method":"HT-29 cell pharmacology, cycloheximide chase, MG132 (proteasome inhibitor), eplerenone (mineralocorticoid receptor antagonist), Western blot","journal":"American journal of physiology. Cell physiology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple pharmacological tools in single cell line; no direct ubiquitination assay","pmids":["24173102"],"is_preprint":false},{"year":2017,"finding":"The ubiquitin ligase Nedd4L indirectly suppresses NKCC1 protein abundance in mouse distal colon; conditional intestinal Nedd4L knockout leads to increased NKCC1 protein and elevated NKCC1-dependent short-circuit current; no direct Nedd4L–NKCC1 co-immunoprecipitation detected, indicating indirect regulation.","method":"Conditional knockout mice (Nedd4L;Vil-Cre), Ussing chamber Isc, Western blot, co-IP (negative result)","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo KO with functional Ussing assay; mechanism shown to be indirect","pmids":["28087701"],"is_preprint":false},{"year":2007,"finding":"NKCC1 protein localizes to the plasma membrane at the growth cone during NGF-induced neurite outgrowth in PC12D cells; NKCC1 knockdown by RNAi drastically reduces NGF-induced neurite outgrowth; NKCC1 expression is upregulated by NGF.","method":"RNAi knockdown, EGFP-NKCC1 live imaging (localization), neurite length measurement","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2-3 — localization by live imaging + RNAi functional assay, single lab","pmids":["17548052"],"is_preprint":false},{"year":2007,"finding":"In native human colonic epithelium, cholinergic Ca2+ signals initiate NKCC1 recruitment to basolateral membranes, followed by activation, internalization, lysosomal degradation, and re-expression over a 4-hour cycle; internalization requires EGFR kinase activity; cAMP (forskolin) sustains NKCC1 activity without internalization; co-stimulation prolongs the cycle.","method":"Human colonic crypt imaging, BCECF/Fura-2/calcein fluorescence, bumetanide-sensitive 86Rb uptake, EGFR inhibitor (tyrphostin-AG1478), cycloheximide, chloroquine","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (imaging, functional transport, pharmacological dissection) in native human tissue","pmids":["17478539"],"is_preprint":false},{"year":2015,"finding":"N-glycosylation of NKCC1 is required for its plasma membrane targeting and transport function; inhibition of N-glycan biosynthesis (tunicamycin) nearly abolishes surface NKCC1 and cotransport; inhibition of N-glycan maturation (swainsonine/kifunensine) eliminates functional complex N-glycosylated NKCC1 from the plasma membrane.","method":"Tunicamycin, swainsonine, kifunensine treatment, surface biotinylation, 86Rb uptake functional assay","journal":"International journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple glycosylation inhibitors + functional transport assay, single lab","pmids":["26351455"],"is_preprint":false},{"year":2022,"finding":"NKCC1 in microglia regulates baseline and reactive microglial morphology, process recruitment to injury sites, and volume adaptation via membrane conductance in a cell-autonomous manner; microglial NKCC1 deficiency leads to NLRP3 inflammasome priming and increased IL-1β production; NKCC1 microglial KO mice show worse outcomes after experimental stroke.","method":"Conditional microglial NKCC1 knockout, morphology analysis, NLRP3/IL-1β assay, experimental stroke model, electrophysiology","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 2 — cell-type-specific KO with multiple mechanistic and in vivo phenotypic readouts","pmids":["35085235"],"is_preprint":false},{"year":2018,"finding":"TRPV1 activation by capsaicin or hyperosmotic solution stimulates NKCC1 phosphorylation and ion transport in lens epithelium via ERK1/2 and WNK kinase signaling; TRPV1-/- lenses lack NKCC1 phosphorylation and Rb+ uptake responses; WNK inhibitor WNK463 prevents NKCC1 phosphorylation; ERK acts upstream of WNK in the signaling cascade.","method":"TRPV1 knockout mice, Rb+ uptake assay, NKCC1 phosphorylation (Western blot), MEK/ERK inhibitor (U0126), WNK inhibitor (WNK463), TRPV1 agonist/antagonist","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 2 — KO mice + pharmacological dissection of pathway + functional assay, multiple orthogonal methods","pmids":["30207782"],"is_preprint":false},{"year":2005,"finding":"Six1 and Six4 homeobox transcription factors directly bind multiple sites in the Slc12a2 promoter; gel-retardation assays show distinct DNA-binding specificities between Six1 and Six4; Slc12a2 expression is reduced in developing dorsal root ganglia of Six1-/-/Six4-/- double knockout mice.","method":"Gel-retardation assay (EMSA), in situ hybridization in double-KO mice","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 2 — EMSA + in vivo KO expression; direct transcriptional control demonstrated","pmids":["15955062"],"is_preprint":false},{"year":2011,"finding":"NKCC1 phosphorylation correlates with activation and stimulation of ion transport; kinase inhibitors reduce both phosphorylation and activity of NKCC1 and NKCC2A; calyculin A (phosphatase inhibitor) increases phosphorylation but only slightly stimulates NKCC1 and inhibits NKCC2A, suggesting phosphorylation of N-terminal domain sets transport capacity but final activity depends on additional factors.","method":"Stably expressing HEK-293 cells, 86Rb uptake, phospho-specific antibodies, calyculin A and kinase inhibitor pharmacology","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — systematic pharmacological dissection with functional and phosphorylation readouts, single lab","pmids":["21464992"],"is_preprint":false},{"year":2019,"finding":"Novel human SLC12A2/NKCC1 mutations (DFX and Kilquist homozygous deletion) impair goblet cell mucus granule exocytosis, leading to secretion of intact granules into the colonic lumen; loss of NKCC1 or DFX expression aggravates inflammatory response to Citrobacter rodentium infection and decreases claudin-2 expression.","method":"Mouse model of NKCC1-DFX mutation, electron microscopy, immunostaining, FISH, Citrobacter infection model, multiplex cytokine assay","journal":"Cellular and molecular gastroenterology and hepatology","confidence":"High","confidence_rationale":"Tier 2 — mouse model recapitulating human mutation + multiple functional assays + infection model","pmids":["31655271"],"is_preprint":false},{"year":2020,"finding":"In a Drosophila NGLY1-deficiency model, Ncc69 (NKCC1/2 ortholog) is the top genetic modifier; in NGLY1-/- mouse cells, NKCC1 has altered average molecular weight (consistent with N-glycosylation defect) and reduced cotransporter function, linking NKCC1 misregulation to defects in secretory epithelium function in NGLY1 deficiency.","method":"Drosophila genetic screen, NGLY1-/- mouse cells, functional NKCC1 assay, molecular weight analysis","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2 — genetic modifier screen + mammalian cell functional validation; mechanism (N-glycosylation) inferred","pmids":["33315011"],"is_preprint":false},{"year":2009,"finding":"NKCC1 mediates vascular smooth muscle cell contraction; bumetanide inhibits myogenic tone and agonist-induced contractions in wild-type mesenteric arteries but is completely without effect in NKCC1-/- arteries, demonstrating that NKCC1 is the relevant bumetanide target in VSMC excitation-contraction coupling; effect is independent of nitric oxide.","method":"NKCC1 knockout mice, mesenteric artery myography, NOS inhibition (L-NAME)","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 2 — KO mice with pharmacological dissection + functional vascular assay","pmids":["19150334"],"is_preprint":false},{"year":2021,"finding":"AAV-mediated neuron-specific NKCC1 knockdown restores intracellular chloride concentration, GABA inhibitory efficacy, and neuronal network dynamics in Ts65Dn Down syndrome mice in vitro and ex vivo, and rescues cognitive deficits in behavioral tasks in vivo.","method":"AAV-RNAi in vivo, intracellular Cl- measurement, electrophysiology, behavioral assays in Ts65Dn mice","journal":"Molecular therapy","confidence":"High","confidence_rationale":"Tier 2 — in vivo gene therapy knockdown + multiple mechanistic (Cl- homeostasis, electrophysiology) and behavioral readouts","pmids":["34058387"],"is_preprint":false},{"year":1998,"finding":"NKCC1 and NKCC2 have distinct kinetic properties: NKCC2A has ~4-fold lower Rb affinity and ~3-fold higher bumetanide affinity than NKCC1; NKCC1 activity is governed primarily by intracellular [Cl-] rather than cell volume; NKCC2 activity responds to volume changes and intracellular [Cl-] in parallel, supporting a model where NKCC2 apical activity is matched to basolateral Cl- exit via [Cl-]i.","method":"Stable expression in HEK-293 cells, 86Rb uptake kinetics, chimeric construct analysis, ion substitution experiments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstituted transport kinetics with chimeras and ion substitution, mechanistically defining isoform differences","pmids":["9556622"],"is_preprint":false}],"current_model":"NKCC1 (SLC12A2) is an electroneutral Na+/K+/2Cl- cotransporter that assembles as a dimer with an LeuT-fold transmembrane core harboring defined ion-binding sites for Na+, K+, and 2Cl-; its transport activity is regulated by phosphorylation of N-terminal threonines by the WNK–SPAK/OSR1 kinase cascade (and suppressed by PP1-type phosphatases), with additional modulation by N-glycosylation, aldosterone-mediated protein stabilization, and splice-variant-dependent loss of the PKA site; it localizes to basolateral membranes of secretory epithelia and functions in transepithelial Cl- secretion, cell volume regulation, endolymph and CSF homeostasis, and neuronal Cl- accumulation that sustains depolarizing GABA signaling in immature neurons, while also interacting with Cofilin-1 and the LAT1-mTORC1 axis to regulate cell migration and growth."},"narrative":{"teleology":[{"year":1997,"claim":"Initial molecular characterization defined the SLC12A2 gene structure, tissue-specific promoter usage, and a brain-specific splice variant lacking a PKA phosphorylation site, establishing the framework for understanding isoform-specific regulation.","evidence":"Genomic cloning, RNase protection, primer extension, RT-PCR of splice variants","pmids":["9357771"],"confidence":"Medium","gaps":["Direct functional consequence of exon 21 exclusion on transport not tested","PKA-mediated regulation of the full-length isoform not demonstrated in vivo"]},{"year":1997,"claim":"Localization of NKCC1 to the apical choroid plexus and neuronal cell bodies established its dual epithelial-neuronal expression pattern, implying roles in both CSF ion homeostasis and neuronal Cl⁻ regulation.","evidence":"Immunocytochemistry, confocal microscopy, ⁸⁶Rb⁺ transport in polarized choroid plexus cells","pmids":["9038823"],"confidence":"High","gaps":["In vivo functional consequence of choroid plexus NKCC1 not yet demonstrated","Mechanism of apical vs. basolateral sorting unknown"]},{"year":1998,"claim":"Reconstitution kinetics revealed that NKCC1 activity is governed primarily by intracellular Cl⁻ concentration rather than cell volume, distinguishing it from NKCC2 and defining the sensory logic of cotransporter regulation.","evidence":"Stable HEK-293 expression, ⁸⁶Rb uptake kinetics, chimeric constructs, ion substitution","pmids":["9556622"],"confidence":"High","gaps":["Molecular sensor for intracellular Cl⁻ not identified","Structural basis of isoform-specific kinetic differences unknown at this time"]},{"year":1999,"claim":"Positional cloning of deafness-causing Slc12a2 mutations in mice established NKCC1 as essential for endolymph K⁺ recycling and cochlear function, providing the first in vivo loss-of-function phenotype.","evidence":"Positional cloning, mutation identification, phenotyping of sy/sy(ns) deaf mice","pmids":["10401008"],"confidence":"High","gaps":["Precise cell type within stria vascularis mediating the phenotype not resolved","Human disease mutations not yet identified at this time"]},{"year":2001,"claim":"NKCC1 knockout airway studies demonstrated that basolateral NKCC1 is the principal Cl⁻ entry pathway for agonist-stimulated anion secretion, with HCO₃⁻ secretion partially compensating in its absence.","evidence":"NKCC1 KO mice, Ussing chamber short-circuit current, bumetanide pharmacology","pmids":["11443061"],"confidence":"High","gaps":["Relative contribution of NKCC1 vs. other basolateral Cl⁻ pathways in adult airways not quantified","Compensatory HCO₃⁻ mechanism not molecularly characterized"]},{"year":2003,"claim":"Identification of SPAK/PASK as the direct kinase phosphorylating N-terminal threonines of NKCC1 established the core activating kinase–cotransporter axis, with constitutive SPAK–NKCC1 binding and kinase/phosphatase balance controlling activity.","evidence":"Co-IP, ³²P phosphorylation, dominant-negative PASK, ⁸⁶Rb uptake, calyculin A rescue in HEK cells","pmids":["12740379"],"confidence":"High","gaps":["Upstream kinase activating SPAK not yet connected","Identity of relevant phosphatase not established"]},{"year":2005,"claim":"Multiple tissue-specific studies—sweat gland, juxtaglomerular cells—confirmed basolateral NKCC1 as essential for secretory NaCl entry and revealed an unexpected role suppressing basal renin release, broadening the physiological scope of the transporter.","evidence":"Immunoelectron microscopy (sweat gland), NKCC1 KO mice + patch-clamp + renin assay (JG cells)","pmids":["15843440","16106034"],"confidence":"High","gaps":["How Cl⁻ accumulation mechanistically suppresses renin exocytosis not delineated","Relevance of NKCC1 in human sweat disorders not tested"]},{"year":2007,"claim":"In native human colonic crypts, cholinergic stimulation was shown to trigger a dynamic cycle of NKCC1 membrane recruitment, activation, EGFR-dependent internalization, lysosomal degradation, and re-synthesis, revealing post-translational trafficking as a major regulatory layer.","evidence":"Human colonic crypt imaging, ⁸⁶Rb uptake, tyrphostin-AG1478 EGFR inhibitor, cycloheximide, chloroquine","pmids":["17478539"],"confidence":"High","gaps":["EGFR phosphorylation site on NKCC1 or adaptor not identified","Whether this trafficking cycle operates in non-colonic epithelia unknown"]},{"year":2009,"claim":"Zebrafish nkcc1 loss-of-function confirmed a conserved requirement for NKCC1 in endolymph volume regulation, extending the cochlear phenotype from mouse and establishing evolutionary conservation.","evidence":"ENU mutagenesis, morpholino rescue of splicing defect, otic vesicle volume measurement","pmids":["19633174"],"confidence":"High","gaps":["Specific ionic mechanism by which NKCC1 drives endolymph volume in zebrafish not resolved"]},{"year":2012,"claim":"Genetic placement of SPAK/OSR1 downstream of WNK1 and upstream of NKCC1 via double-knockin ES cells completed the WNK–SPAK/OSR1–NKCC1 signaling cascade, showing SPAK/OSR1 are both necessary and sufficient kinases for NKCC1 activation.","evidence":"Double-knockin ES cells (SPAK/OSR1 cannot be activated by WNK1), phospho-specific antibodies, ion transport","pmids":["22032326"],"confidence":"High","gaps":["Whether other WNK family members contribute differentially in specific tissues not resolved","Feedback from SPAK/OSR1 onto WNK activity mechanistically unexplained"]},{"year":2012,"claim":"NKCC1 knockdown in neonatal subventricular zone progenitors demonstrated that NKCC1-mediated Cl⁻ accumulation underlies depolarizing GABA responses required for neural progenitor proliferation and dendritic arborization, with pharmacological GABA_A rescue confirming the mechanism.","evidence":"In vivo shRNA electroporation, Ki67 staining, Ca²⁺ imaging, dendritic morphology, pentobarbital rescue","pmids":["23015452"],"confidence":"High","gaps":["Whether NKCC1 also affects migration of SVZ-derived neuroblasts not tested","Long-term circuit consequences of neonatal NKCC1 loss not characterized"]},{"year":2015,"claim":"N-glycosylation was shown to be required for NKCC1 plasma membrane targeting and transport function, with glycan biosynthesis or maturation inhibition eliminating surface NKCC1 and cotransport.","evidence":"Tunicamycin, swainsonine, kifunensine treatment, surface biotinylation, ⁸⁶Rb uptake","pmids":["26351455"],"confidence":"Medium","gaps":["Specific glycosylation sites critical for trafficking not mapped by mutagenesis","Only tested in one cell type"]},{"year":2017,"claim":"Discovery of a physical NKCC1–Cofilin-1 interaction linked NKCC1 to actin cytoskeletal remodeling and glioblastoma cell migration via RhoA/Rac1 signaling, expanding NKCC1 function beyond ion transport.","evidence":"Co-IP, siRNA knockdown, F-actin staining, Rho-GTPase activity, migration assay, intracranial mouse model","pmids":["28679472"],"confidence":"High","gaps":["Whether ion transport activity is required for migration effect or whether it is a scaffolding function unknown","Reciprocal effect of Cofilin-1 on NKCC1 transport not tested"]},{"year":2019,"claim":"The first cryo-EM structure of NKCC1 (zebrafish) defined the LeuT-fold architecture, ion-binding sites for Na⁺, K⁺, and 2Cl⁻, and the ion-translocation pathway, providing the atomic framework for understanding transport mechanism and CCC family function.","evidence":"Single-particle cryo-EM, MD simulations, mutagenesis, functional transport assays","pmids":["31367042"],"confidence":"High","gaps":["Only one conformational state captured","Drug-binding sites not resolved"]},{"year":2019,"claim":"Identification of NKCC1 in a complex with the leucine transporter LAT1 revealed that NKCC1 suppresses mTORC1 signaling and couples cell volume to cell mass regulation, establishing a non-canonical growth-regulatory role.","evidence":"Co-IP, CRISPR KO, siRNA, mTORC1 signaling assays, colonic organoids, mouse colon KO","pmids":["31067471"],"confidence":"High","gaps":["Direct vs. indirect nature of NKCC1–LAT1 interaction not structurally resolved","Whether ion transport activity is required for mTORC1 suppression not determined"]},{"year":2020,"claim":"Human NKCC1 cryo-EM structure in a partially loaded inward-open state revealed dimeric assembly, broken α-helical geometry at ion-binding sites on TM1/TM6, and distinct entryway/exit routes for different ions, refining the transport cycle model.","evidence":"Single-particle cryo-EM of human NKCC1","pmids":["32081947"],"confidence":"High","gaps":["Outward-facing state not captured in this study","Ion occupancy at individual sites uncertain"]},{"year":2020,"claim":"Functional characterization of de novo SLC12A2 mutations from children with neurodevelopmental disorders and hearing loss established loss-of-function as the pathogenic mechanism in human disease, confirming NKCC1 haploinsufficiency as disease-causing.","evidence":"Xenopus oocyte expression, ⁸⁶Rb uptake for multiple patient variants, trio exome sequencing","pmids":["32658972"],"confidence":"High","gaps":["Genotype–phenotype correlations across variant types not fully established","Whether heterozygous loss is sufficient or requires second hit unknown"]},{"year":2022,"claim":"Capture of NKCC1 in outward-facing, occluded, and drug-bound conformations completed the structural catalog of the transport cycle, revealed bumetanide/furosemide binding pockets, and showed that N-terminal phosphoregulatory domain–C-terminal domain interaction controls conformational switching.","evidence":"Cryo-EM in multiple conformational/drug-bound states, functional mutagenesis, MD simulations","pmids":["35585053","36239040","36306358"],"confidence":"High","gaps":["Full transport cycle with all ions simultaneously resolved not achieved","How phosphorylation physically disrupts N-term–C-term interaction not structurally captured"]},{"year":2023,"claim":"Choroid plexus NKCC1 was shown to be activated by blood-derived K⁺ to clear CSF and prevent post-hemorrhagic ventriculomegaly; a phosphodeficient mutant failed to rescue, demonstrating that phosphorylation-dependent activation is required for CSF homeostasis in disease.","evidence":"AAV-mediated ChP-targeted NKCC1 overexpression/phosphodeficient mutant, Ca²⁺ imaging, ventriculometry, CSF K⁺ measurement","pmids":["36893755"],"confidence":"High","gaps":["Identity of the kinase activated by K⁺-triggered Ca²⁺ signals in choroid plexus not confirmed","Whether NKCC1-targeted therapy is viable in human post-hemorrhagic hydrocephalus untested"]},{"year":null,"claim":"Outstanding questions include the structural basis of phosphorylation-induced N-terminal–C-terminal domain dissociation, the identity of the Cl⁻ sensor that activates WNK signaling, whether NKCC1's mTORC1-suppressive and migration-promoting roles require ion transport or scaffolding, and the molecular mechanisms underlying NKCC1's role in goblet cell mucus granule exocytosis.","evidence":"","pmids":[],"confidence":"Low","gaps":["Structural visualization of phosphorylated vs. dephosphorylated regulatory domain interaction","Intracellular Cl⁻ sensor identity linking Cl⁻ to WNK activation","Separation of transport-dependent vs. scaffolding functions in migration and growth signaling"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,1,2,3,4,41]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[12,22,23,30,31,32]}],"pathway":[{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,1,4,41]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[6,7,18,34]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[19,20,40]}],"complexes":["NKCC1 homodimer"],"partners":["SPAK","OSR1","WNK1","CFL1","SLC7A5","TRPV1"],"other_free_text":[]},"mechanistic_narrative":"SLC12A2 encodes NKCC1, an electroneutral Na⁺/K⁺/2Cl⁻ cotransporter that operates as a homodimer with an LeuT-fold transmembrane core containing discrete binding sites for Na⁺, K⁺, and two Cl⁻ ions, and that undergoes alternating-access conformational changes to couple ion translocation [PMID:31367042, PMID:32081947, PMID:36239040]. Transport activity is activated by WNK–SPAK/OSR1 kinase-mediated phosphorylation of N-terminal threonines and suppressed by PP1-type phosphatases, with the phosphoregulatory domain communicating with the C-terminal domain to control conformational transitions; additional regulation occurs through N-glycosylation-dependent surface targeting and aldosterone-mediated protein stabilization [PMID:12740379, PMID:22032326, PMID:35585053, PMID:26351455, PMID:24173102]. Physiologically, NKCC1 localizes to basolateral membranes of secretory epithelia—including airway, colon, sweat gland, and mammary gland—where it drives transepithelial Cl⁻ secretion, and to the apical membrane of choroid plexus epithelium where it mediates CSF K⁺ clearance and volume homeostasis; in neurons, NKCC1 accumulates intracellular Cl⁻ to sustain depolarizing GABA signaling critical for progenitor proliferation and circuit maturation [PMID:11443061, PMID:9038823, PMID:33469018, PMID:23015452, PMID:34058387]. Loss-of-function mutations in SLC12A2 cause sensorineural hearing loss and neurodevelopmental disorders in humans and mice, linked to defective endolymph homeostasis and impaired neuronal Cl⁻ regulation [PMID:10401008, PMID:32658972]."},"prefetch_data":{"uniprot":{"accession":"P55011","full_name":"Solute carrier family 12 member 2","aliases":["Basolateral Na-K-Cl symporter","Bumetanide-sensitive sodium-(potassium)-chloride cotransporter 2","BSC2","Na-K-2Cl cotransporter 1","hNKCC1"],"length_aa":1212,"mass_kda":131.4,"function":"Cation-chloride cotransporter which mediates the electroneutral transport of chloride, potassium and/or sodium ions across the membrane (PubMed:16669787, PubMed:32081947, PubMed:32294086, PubMed:33597714, PubMed:35585053, PubMed:36239040, PubMed:36306358, PubMed:7629105). Plays a vital role in the regulation of ionic balance and cell volume (PubMed:16669787, PubMed:32081947, PubMed:32294086, PubMed:7629105)","subcellular_location":"Basolateral cell membrane","url":"https://www.uniprot.org/uniprotkb/P55011/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SLC12A2","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CANX","stoichiometry":0.2},{"gene":"TMEM192","stoichiometry":0.2},{"gene":"TMED10","stoichiometry":0.2},{"gene":"CCDC47","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/SLC12A2","total_profiled":1310},"omim":[{"mim_id":"619083","title":"DELPIRE-MCNEILL SYNDROME; DELMNES","url":"https://www.omim.org/entry/619083"},{"mim_id":"619081","title":"DEAFNESS, AUTOSOMAL DOMINANT 78; DFNA78","url":"https://www.omim.org/entry/619081"},{"mim_id":"619080","title":"KILQUIST SYNDROME; KILQS","url":"https://www.omim.org/entry/619080"},{"mim_id":"616861","title":"SOLUTE CARRIER FAMILY 12 (POTASSIUM/CHLORIDE TRANSPORTER), MEMBER 9; SLC12A9","url":"https://www.omim.org/entry/616861"},{"mim_id":"610153","title":"DEAFNESS, AUTOSOMAL RECESSIVE 49; DFNB49","url":"https://www.omim.org/entry/610153"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"},{"location":"Plasma membrane","reliability":"Approved"},{"location":"Basal body","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"salivary gland","ntpm":71.2}],"url":"https://www.proteinatlas.org/search/SLC12A2"},"hgnc":{"alias_symbol":["NKCC1","BSC2","BSC-2","PPP1R141","CCC1"],"prev_symbol":[]},"alphafold":{"accession":"P55011","domains":[{"cath_id":"1.20.1740.10","chopping":"287-751","consensus_level":"medium","plddt":89.0428,"start":287,"end":751},{"cath_id":"3.40.50.620","chopping":"786-928","consensus_level":"high","plddt":91.998,"start":786,"end":928},{"cath_id":"-","chopping":"1020-1200","consensus_level":"high","plddt":89.662,"start":1020,"end":1200}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P55011","model_url":"https://alphafold.ebi.ac.uk/files/AF-P55011-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P55011-F1-predicted_aligned_error_v6.png","plddt_mean":73.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SLC12A2","jax_strain_url":"https://www.jax.org/strain/search?query=SLC12A2"},"sequence":{"accession":"P55011","fasta_url":"https://rest.uniprot.org/uniprotkb/P55011.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P55011/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P55011"}},"corpus_meta":[{"pmid":"24482245","id":"PMC_24482245","title":"Contributions of the Na⁺/K⁺-ATPase, NKCC1, and Kir4.1 to hippocampal K⁺ clearance and volume responses.","date":"2014","source":"Glia","url":"https://pubmed.ncbi.nlm.nih.gov/24482245","citation_count":221,"is_preprint":false},{"pmid":"12740379","id":"PMC_12740379","title":"PASK (proline-alanine-rich STE20-related kinase), a regulatory kinase of the Na-K-Cl cotransporter (NKCC1).","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12740379","citation_count":220,"is_preprint":false},{"pmid":"22705273","id":"PMC_22705273","title":"Cation-chloride cotransporters NKCC1 and KCC2 as potential targets for novel antiepileptic and antiepileptogenic treatments.","date":"2012","source":"Neuropharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/22705273","citation_count":213,"is_preprint":false},{"pmid":"9038823","id":"PMC_9038823","title":"Expression of the Na(+)-K(+)-2Cl- cotransporter BSC2 in the nervous system.","date":"1997","source":"The American journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/9038823","citation_count":200,"is_preprint":false},{"pmid":"10401008","id":"PMC_10401008","title":"Mutation of the Na-K-Cl co-transporter gene Slc12a2 results in deafness in mice.","date":"1999","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/10401008","citation_count":137,"is_preprint":false},{"pmid":"22032326","id":"PMC_22032326","title":"SPAK/OSR1 regulate NKCC1 and WNK activity: analysis of WNK isoform interactions and activation by T-loop trans-autophosphorylation.","date":"2012","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/22032326","citation_count":114,"is_preprint":false},{"pmid":"9556622","id":"PMC_9556622","title":"Comparison of Na-K-Cl cotransporters. 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TM1 and TM6 helices break α-helical geometry at ion-binding sites; multiple extracellular entryways and intracellular exits are identified, suggesting K+, Na+, and Cl- may traverse along distinct routes.\",\n      \"method\": \"Single-particle cryo-EM\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution cryo-EM structure of human protein\",\n      \"pmids\": [\"32081947\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Cryo-EM structures of human NKCC1 and mouse KCC2 at near-atomic resolution identify essential residues for ion transport and reveal mechanisms by which N-terminal phosphorylation regulates transport activity.\",\n      \"method\": \"Cryo-EM, computational analysis, functional characterization\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM + functional + computational in one study\",\n      \"pmids\": [\"33597714\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Cryo-EM structure of NKCC1 in an outward-facing conformation shows bumetanide wedged into a pocket in the extracellular ion translocation pathway; comparison with inward-facing structures defines the translocation pathway and conformational changes for ion translocation; an N-terminal phosphoregulatory domain interacts with the C-terminal domain, suggesting (de)phosphorylation regulates NKCC1 by tuning this domain association.\",\n      \"method\": \"Single-particle cryo-EM, functional studies, mutagenesis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structures in multiple conformations + functional validation\",\n      \"pmids\": [\"35585053\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"2.6 Å cryo-EM structure of human NKCC1 in substrate-loaded, occluded inward-facing state reveals Cl- binding at Cl1 site bridges scaffold and bundle domains via K+; Cl- at Cl2 site plays a structural role analogous to conserved glutamate in SLC6 transporters; a putative Na+ release pathway along TM5 coupled to the Cl2 site is identified and supported by functional studies and MD simulations.\",\n      \"method\": \"Cryo-EM (2.6 Å), functional assays in mammalian cells, MD simulations\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution structure + functional + computational, orthogonal methods\",\n      \"pmids\": [\"36239040\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Four cryo-EM structures of human NKCC1 (apo and bound to bumetanide or furosemide) reveal two drug-binding sites at transmembrane and cytosolic C-terminal domains; an inhibition mechanism involving coupled movement between cytosolic and transmembrane domains is delineated; the C-terminal domain is implicated in long-range conformational coupling.\",\n      \"method\": \"Single-particle cryo-EM, functional studies\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple structures with and without inhibitors + functional studies\",\n      \"pmids\": [\"36306358\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"PASK/SPAK kinase directly phosphorylates two regulatory threonines on the N-terminal domain of NKCC1 and activates cotransport; dominant-negative PASK markedly reduces NKCC1 phosphorylation and activity; co-immunoprecipitation confirms constitutive PASK–NKCC1 binding in HEK cells; phosphatase inhibitor calyculin A rescues activity, indicating kinase/phosphatase balance controls NKCC1.\",\n      \"method\": \"Dominant-negative overexpression, co-immunoprecipitation, 32Pi phosphorylation assay, ion transport assay (86Rb uptake)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP + functional assay + phosphorylation assay, multiple orthogonal methods\",\n      \"pmids\": [\"12740379\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"SPAK and OSR1 are essential upstream kinases for NKCC1 phosphorylation and activation; double-knockin ES cells where SPAK/OSR1 cannot be activated by WNK1 show complete loss of NKCC1 phosphorylation and activation; SPAK/OSR1 activity also significantly influences WNK kinase activity (feedback).\",\n      \"method\": \"Double-knockin ES cells (loss-of-function genetic approach), phospho-specific antibodies, ion transport assay\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic knockin with defined molecular and functional phenotype, replicated across conditions\",\n      \"pmids\": [\"22032326\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Estradiol increases protein levels of SPAK and OSR1 in the neonatal hypothalamus in a transcription-dependent manner; SPAK/OSR1 upregulation mediates estradiol-enhanced NKCC1 phosphorylation; antisense knockdown of SPAK (and to a lesser extent OSR1) blocks estradiol-enhanced NKCC1 phosphorylation and GABA-induced Ca2+ influx.\",\n      \"method\": \"In vivo antisense oligonucleotide knockdown, Western blot with phospho-specific antibodies, calcium imaging\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo knockdown + phosphorylation assay + functional Ca2+ imaging, multiple methods\",\n      \"pmids\": [\"22238094\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"IL-6 autocrine signaling in axotomized sensory neurons activates NKCC1 via JAK signaling and IL-6 receptor upregulation, leading to NKCC1 phosphorylation and Cl- accumulation that supports neurite regrowth; IL-6 neutralization or IL-6-/- mice prevent NKCC1 phosphorylation and Cl- accumulation.\",\n      \"method\": \"IL-6 knockout mice, receptor-blocking antibodies, pharmacological JAK inhibition, functional Cl- accumulation assay, neurite growth assay\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mice + pharmacological + functional assays, multiple orthogonal approaches\",\n      \"pmids\": [\"21940443\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Point mutations in Slc12a2 (encoding basolateral Na-K-Cl cotransporter NKCC1) cause deafness and abnormal endolymph production in sy and sy(ns) mice, establishing NKCC1 as an essential component of K+ recycling in the cochlea.\",\n      \"method\": \"Positional cloning, mutation identification, mouse phenotyping (deaf mutant)\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — positional cloning with in vivo loss-of-function phenotype\",\n      \"pmids\": [\"10401008\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Loss-of-function mutations in zebrafish nkcc1 (slc12a2) cause collapse of the otic vesicle (endolymph fluid loss) and over-inflation of the swim bladder, establishing NKCC1 as required for endolymph volume regulation; morpholino rescue of splicing defect ameliorates ear volume collapse.\",\n      \"method\": \"Forward genetics (ENU mutagenesis), Sanger sequencing, morpholino rescue\",\n      \"journal\": \"Development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo genetic loss-of-function with specific fluid-homeostasis phenotype, morpholino rescue\",\n      \"pmids\": [\"19633174\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"BSC2/NKCC1 protein localizes to the apical surface of choroid plexus epithelium and to neuronal cell bodies/dendrites; apical localization in choroid plexus is confirmed by 86Rb+ uptake in cells grown on permeable filters and confocal microscopy, suggesting a role in CSF K+ homeostasis.\",\n      \"method\": \"Immunocytochemistry, confocal microscopy, 86Rb+ transport assay on polarized epithelial cells\",\n      \"journal\": \"The American journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct localization by immunofluorescence + functional 86Rb transport, multiple methods\",\n      \"pmids\": [\"9038823\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"NKCC1 in the choroid plexus mediates CSF K+ clearance during mouse early postnatal development; overexpression of NKCC1 in choroid plexus increases CSF K+ clearance and reduces circulating CSF; in an obstructive hydrocephalus model, choroid plexus-specific NKCC1 overexpression reduces ventriculomegaly.\",\n      \"method\": \"AAV-mediated gene overexpression in choroid plexus, CSF [K+] measurement, MRI ventriculometry, mouse hydrocephalus model\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo gain-of-function with specific mechanistic and volumetric readouts\",\n      \"pmids\": [\"33469018\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Intraventricular blood increases CSF [K+] and triggers cytosolic calcium activity in choroid plexus epithelial cells, followed by NKCC1 activation; AAV-mediated ChP-targeted NKCC1 overexpression prevents blood-induced ventriculomegaly; phosphodeficient NKCC1-NT51 mutant fails to mitigate ventriculomegaly, demonstrating that phosphorylation-dependent NKCC1 activation is required for CSF clearance.\",\n      \"method\": \"AAV gene delivery, phosphodeficient mutant (loss-of-function), calcium imaging, ventriculometry, CSF K+ measurement\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — phosphodeficient mutant + AAV overexpression + mechanistic imaging, multiple orthogonal methods\",\n      \"pmids\": [\"36893755\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"A gain-of-function missense variant p.Y199C in the N-terminal regulatory domain of SLC12A2/NKCC1 increases Cl--dependent, bumetanide-sensitive cotransporter activity even under hypotonicity (conditions where wild-type is normally silent), identified in human schizophrenia patients.\",\n      \"method\": \"Xenopus oocyte ion transport assay (Cl--dependent 86Rb uptake), patient sequencing\",\n      \"journal\": \"Journal of psychiatric research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — functional reconstitution in Xenopus oocytes with mutant vs. wild-type comparison\",\n      \"pmids\": [\"26955005\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"De novo SLC12A2 mutations identified in children with neurodevelopmental disorders and sensorineural hearing loss all reduce cotransporter function when expressed in Xenopus laevis oocytes, establishing loss-of-function as the pathogenic mechanism.\",\n      \"method\": \"Xenopus oocyte expression assay, trio exome sequencing\",\n      \"journal\": \"Brain\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — functional assay in Xenopus oocytes for multiple variants, direct mechanistic link\",\n      \"pmids\": [\"32658972\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"NKCC1 interacts with actin-regulatory protein Cofilin-1 and regulates its membrane localization; NKCC1 knockdown decreases F-actin content and reduces active RhoA and Rac1, thereby decreasing glioblastoma cell migration.\",\n      \"method\": \"Co-immunoprecipitation (NKCC1–Cofilin-1 interaction), siRNA knockdown, F-actin staining, Rho-GTPase activity assay, in vitro migration assay, intracranial mouse model\",\n      \"journal\": \"EBioMedicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP + KD + multiple functional readouts + in vivo validation\",\n      \"pmids\": [\"28679472\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"NKCC1 (SLC12A2) is present in a complex with the leucine transporter LAT1; NKCC1 depletion enhances LAT1 activity, Akt and Erk activation, and mTORC1 activation, reduces intracellular Na+ and cell volume/mass, and stimulates cell proliferation, establishing NKCC1 as a suppressor of mTORC1 that links cell volume to cell mass regulation.\",\n      \"method\": \"Co-immunoprecipitation (NKCC1–LAT1 complex), NKCC1 siRNA/CRISPR deletion, mTORC1 signaling assays, ion flux measurements, colonic organoids, mouse colon KO\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP + multiple KO/KD models (cells, organoids, mouse) + pathway readout\",\n      \"pmids\": [\"31067471\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"NKCC1 knockdown in neonatal mouse subventricular zone neural progenitor cells reduces GABA-induced depolarization and Ca2+ responses, decreases proliferative Ki67+ progenitors by ~70%, reduces newborn neuron density by ~60%, and causes truncated dendritic arborization; GABAA agonist pentobarbital rescues proliferation, confirming NKCC1 acts via GABAA receptor depolarization.\",\n      \"method\": \"In vivo electroporation of shRNA, Ki67 immunostaining, calcium imaging, dendritic morphology analysis, pharmacological rescue\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo KD with multiple cellular phenotype readouts and pharmacological rescue\",\n      \"pmids\": [\"23015452\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"NKCC1 promotes GABA-mediated depolarization in Cajal-Retzius neurons; genetic deletion or pharmacological blockade of NKCC1 in vitro and in vivo rescues Cajal-Retzius neurons from apoptosis via blockade of p75NTR receptor signaling pathway.\",\n      \"method\": \"NKCC1 genetic knockout mice, in vitro pharmacological blockade (bumetanide), p75NTR pathway analysis, apoptosis assays\",\n      \"journal\": \"Cerebral cortex\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO + pharmacological + pathway placement (p75NTR), replicated in vitro and in vivo\",\n      \"pmids\": [\"26819276\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"AVP-induced cell swelling in inner medullary collecting duct requires basolateral NaCl uptake via NKCC1; bumetanide abolishes AVP-induced cell height increase; NKCC1 knockout mice lack AVP-induced cell swelling; myosin II also contributes via actin cytoskeleton reorganization.\",\n      \"method\": \"NKCC1 knockout mice, quantitative video microscopy, bumetanide pharmacology, immunocytochemistry, blebbistatin inhibition\",\n      \"journal\": \"American journal of physiology. Renal physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mice + pharmacology + direct morphometry, multiple approaches\",\n      \"pmids\": [\"18417545\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"NKCC1 is expressed on the basolateral membrane of mammary epithelial cells; NKCC1-/- mice show delayed ductal outgrowth and increased branching morphogenesis during virgin development in a cell-autonomous manner (demonstrated by transplantation); loss of NKCC1 impairs lactation function.\",\n      \"method\": \"NKCC1 knockout mice, mammary gland transplantation (cell-autonomous test), immunolocalization\",\n      \"journal\": \"Molecular endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO + transplantation (cell-autonomous) + localization\",\n      \"pmids\": [\"12040017\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"NKCC1 is expressed on the basolateral membrane of secretory coil cells of sweat glands (rat, mouse, human) and is responsible for bumetanide-sensitive NaCl secretion in sweat glands; NKCC2 is absent; basolateral NKCC1 mediates NaCl entry for fluid secretion.\",\n      \"method\": \"RT-PCR, Western blot, immunoperoxidase, immunoelectron microscopy\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — immunoelectron microscopy confirming basolateral membrane localization + functional transport data\",\n      \"pmids\": [\"15843440\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"NKCC1 in juxtaglomerular granular cells directly suppresses basal renin release; furosemide stimulates renin release from wild-type JG cells (measured by patch-clamp membrane capacitance and primary culture assay) but not from NKCC1-deficient cells; NKCC1-/- mice have elevated plasma renin.\",\n      \"method\": \"NKCC1 knockout mice, patch-clamp (membrane capacitance), primary JG cell culture renin release assay\",\n      \"journal\": \"American journal of physiology. Renal physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mice + electrophysiology + cell culture functional assay\",\n      \"pmids\": [\"16106034\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"NKCC1 on the basolateral membrane is required for large UTP-stimulated anion secretory responses in mouse airways; NKCC1-/- neonatal trachea has reduced basal short-circuit current; HCO3- secretion compensates for reduced Cl- secretion in knockout airways.\",\n      \"method\": \"NKCC1 knockout mice, Ussing chamber ion transport assay, bumetanide pharmacology\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mice + Ussing chamber functional assay\",\n      \"pmids\": [\"11443061\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"The Slc12a2 gene encodes a cotransporter with 27 exons and tissue-specific transcription initiation; a brain-specific alternatively spliced variant lacking exon 21 (encoding 16 amino acids of the C-terminal tail) loses the single PKA consensus phosphorylation site, suggesting splice-variant-specific regulation.\",\n      \"method\": \"Genomic cloning, RNase protection assay, primer extension, luciferase reporter transfection, RT-PCR of splice variants\",\n      \"journal\": \"The American journal of physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — molecular cloning with functional promoter assay; splice-variant mechanism inferred rather than directly tested\",\n      \"pmids\": [\"9357771\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"NKCC1 upregulation in hypothalamic paraventricular nucleus presympathetic neurons causes depolarizing shift in GABA reversal potential and disrupts GABAergic inhibition in spontaneously hypertensive rats; NKCC1 inhibition normalizes EGABA; increased N-glycosylation of NKCC1 contributes to its enhanced activity in hypertension.\",\n      \"method\": \"Gramicidin perforated-patch clamp (EGABA measurement), NKCC1 inhibitor bumetanide, N-glycosylation inhibition, Western blot\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — electrophysiology + pharmacology + glycosylation manipulation, multiple orthogonal methods\",\n      \"pmids\": [\"22723696\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Aldosterone upregulates NKCC1 protein expression rapidly and independently of mRNA changes, by increasing protein stability (reducing ubiquitination) via mineralocorticoid receptors; proteasome inhibitor MG132 and cycloheximide experiments confirm post-translational stabilization mechanism.\",\n      \"method\": \"HT-29 cell pharmacology, cycloheximide chase, MG132 (proteasome inhibitor), eplerenone (mineralocorticoid receptor antagonist), Western blot\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple pharmacological tools in single cell line; no direct ubiquitination assay\",\n      \"pmids\": [\"24173102\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"The ubiquitin ligase Nedd4L indirectly suppresses NKCC1 protein abundance in mouse distal colon; conditional intestinal Nedd4L knockout leads to increased NKCC1 protein and elevated NKCC1-dependent short-circuit current; no direct Nedd4L–NKCC1 co-immunoprecipitation detected, indicating indirect regulation.\",\n      \"method\": \"Conditional knockout mice (Nedd4L;Vil-Cre), Ussing chamber Isc, Western blot, co-IP (negative result)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo KO with functional Ussing assay; mechanism shown to be indirect\",\n      \"pmids\": [\"28087701\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"NKCC1 protein localizes to the plasma membrane at the growth cone during NGF-induced neurite outgrowth in PC12D cells; NKCC1 knockdown by RNAi drastically reduces NGF-induced neurite outgrowth; NKCC1 expression is upregulated by NGF.\",\n      \"method\": \"RNAi knockdown, EGFP-NKCC1 live imaging (localization), neurite length measurement\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — localization by live imaging + RNAi functional assay, single lab\",\n      \"pmids\": [\"17548052\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"In native human colonic epithelium, cholinergic Ca2+ signals initiate NKCC1 recruitment to basolateral membranes, followed by activation, internalization, lysosomal degradation, and re-expression over a 4-hour cycle; internalization requires EGFR kinase activity; cAMP (forskolin) sustains NKCC1 activity without internalization; co-stimulation prolongs the cycle.\",\n      \"method\": \"Human colonic crypt imaging, BCECF/Fura-2/calcein fluorescence, bumetanide-sensitive 86Rb uptake, EGFR inhibitor (tyrphostin-AG1478), cycloheximide, chloroquine\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (imaging, functional transport, pharmacological dissection) in native human tissue\",\n      \"pmids\": [\"17478539\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"N-glycosylation of NKCC1 is required for its plasma membrane targeting and transport function; inhibition of N-glycan biosynthesis (tunicamycin) nearly abolishes surface NKCC1 and cotransport; inhibition of N-glycan maturation (swainsonine/kifunensine) eliminates functional complex N-glycosylated NKCC1 from the plasma membrane.\",\n      \"method\": \"Tunicamycin, swainsonine, kifunensine treatment, surface biotinylation, 86Rb uptake functional assay\",\n      \"journal\": \"International journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple glycosylation inhibitors + functional transport assay, single lab\",\n      \"pmids\": [\"26351455\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"NKCC1 in microglia regulates baseline and reactive microglial morphology, process recruitment to injury sites, and volume adaptation via membrane conductance in a cell-autonomous manner; microglial NKCC1 deficiency leads to NLRP3 inflammasome priming and increased IL-1β production; NKCC1 microglial KO mice show worse outcomes after experimental stroke.\",\n      \"method\": \"Conditional microglial NKCC1 knockout, morphology analysis, NLRP3/IL-1β assay, experimental stroke model, electrophysiology\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific KO with multiple mechanistic and in vivo phenotypic readouts\",\n      \"pmids\": [\"35085235\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TRPV1 activation by capsaicin or hyperosmotic solution stimulates NKCC1 phosphorylation and ion transport in lens epithelium via ERK1/2 and WNK kinase signaling; TRPV1-/- lenses lack NKCC1 phosphorylation and Rb+ uptake responses; WNK inhibitor WNK463 prevents NKCC1 phosphorylation; ERK acts upstream of WNK in the signaling cascade.\",\n      \"method\": \"TRPV1 knockout mice, Rb+ uptake assay, NKCC1 phosphorylation (Western blot), MEK/ERK inhibitor (U0126), WNK inhibitor (WNK463), TRPV1 agonist/antagonist\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mice + pharmacological dissection of pathway + functional assay, multiple orthogonal methods\",\n      \"pmids\": [\"30207782\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Six1 and Six4 homeobox transcription factors directly bind multiple sites in the Slc12a2 promoter; gel-retardation assays show distinct DNA-binding specificities between Six1 and Six4; Slc12a2 expression is reduced in developing dorsal root ganglia of Six1-/-/Six4-/- double knockout mice.\",\n      \"method\": \"Gel-retardation assay (EMSA), in situ hybridization in double-KO mice\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — EMSA + in vivo KO expression; direct transcriptional control demonstrated\",\n      \"pmids\": [\"15955062\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"NKCC1 phosphorylation correlates with activation and stimulation of ion transport; kinase inhibitors reduce both phosphorylation and activity of NKCC1 and NKCC2A; calyculin A (phosphatase inhibitor) increases phosphorylation but only slightly stimulates NKCC1 and inhibits NKCC2A, suggesting phosphorylation of N-terminal domain sets transport capacity but final activity depends on additional factors.\",\n      \"method\": \"Stably expressing HEK-293 cells, 86Rb uptake, phospho-specific antibodies, calyculin A and kinase inhibitor pharmacology\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — systematic pharmacological dissection with functional and phosphorylation readouts, single lab\",\n      \"pmids\": [\"21464992\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Novel human SLC12A2/NKCC1 mutations (DFX and Kilquist homozygous deletion) impair goblet cell mucus granule exocytosis, leading to secretion of intact granules into the colonic lumen; loss of NKCC1 or DFX expression aggravates inflammatory response to Citrobacter rodentium infection and decreases claudin-2 expression.\",\n      \"method\": \"Mouse model of NKCC1-DFX mutation, electron microscopy, immunostaining, FISH, Citrobacter infection model, multiplex cytokine assay\",\n      \"journal\": \"Cellular and molecular gastroenterology and hepatology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — mouse model recapitulating human mutation + multiple functional assays + infection model\",\n      \"pmids\": [\"31655271\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In a Drosophila NGLY1-deficiency model, Ncc69 (NKCC1/2 ortholog) is the top genetic modifier; in NGLY1-/- mouse cells, NKCC1 has altered average molecular weight (consistent with N-glycosylation defect) and reduced cotransporter function, linking NKCC1 misregulation to defects in secretory epithelium function in NGLY1 deficiency.\",\n      \"method\": \"Drosophila genetic screen, NGLY1-/- mouse cells, functional NKCC1 assay, molecular weight analysis\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic modifier screen + mammalian cell functional validation; mechanism (N-glycosylation) inferred\",\n      \"pmids\": [\"33315011\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"NKCC1 mediates vascular smooth muscle cell contraction; bumetanide inhibits myogenic tone and agonist-induced contractions in wild-type mesenteric arteries but is completely without effect in NKCC1-/- arteries, demonstrating that NKCC1 is the relevant bumetanide target in VSMC excitation-contraction coupling; effect is independent of nitric oxide.\",\n      \"method\": \"NKCC1 knockout mice, mesenteric artery myography, NOS inhibition (L-NAME)\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mice with pharmacological dissection + functional vascular assay\",\n      \"pmids\": [\"19150334\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"AAV-mediated neuron-specific NKCC1 knockdown restores intracellular chloride concentration, GABA inhibitory efficacy, and neuronal network dynamics in Ts65Dn Down syndrome mice in vitro and ex vivo, and rescues cognitive deficits in behavioral tasks in vivo.\",\n      \"method\": \"AAV-RNAi in vivo, intracellular Cl- measurement, electrophysiology, behavioral assays in Ts65Dn mice\",\n      \"journal\": \"Molecular therapy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo gene therapy knockdown + multiple mechanistic (Cl- homeostasis, electrophysiology) and behavioral readouts\",\n      \"pmids\": [\"34058387\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"NKCC1 and NKCC2 have distinct kinetic properties: NKCC2A has ~4-fold lower Rb affinity and ~3-fold higher bumetanide affinity than NKCC1; NKCC1 activity is governed primarily by intracellular [Cl-] rather than cell volume; NKCC2 activity responds to volume changes and intracellular [Cl-] in parallel, supporting a model where NKCC2 apical activity is matched to basolateral Cl- exit via [Cl-]i.\",\n      \"method\": \"Stable expression in HEK-293 cells, 86Rb uptake kinetics, chimeric construct analysis, ion substitution experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted transport kinetics with chimeras and ion substitution, mechanistically defining isoform differences\",\n      \"pmids\": [\"9556622\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NKCC1 (SLC12A2) is an electroneutral Na+/K+/2Cl- cotransporter that assembles as a dimer with an LeuT-fold transmembrane core harboring defined ion-binding sites for Na+, K+, and 2Cl-; its transport activity is regulated by phosphorylation of N-terminal threonines by the WNK–SPAK/OSR1 kinase cascade (and suppressed by PP1-type phosphatases), with additional modulation by N-glycosylation, aldosterone-mediated protein stabilization, and splice-variant-dependent loss of the PKA site; it localizes to basolateral membranes of secretory epithelia and functions in transepithelial Cl- secretion, cell volume regulation, endolymph and CSF homeostasis, and neuronal Cl- accumulation that sustains depolarizing GABA signaling in immature neurons, while also interacting with Cofilin-1 and the LAT1-mTORC1 axis to regulate cell migration and growth.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"SLC12A2 encodes NKCC1, an electroneutral Na⁺/K⁺/2Cl⁻ cotransporter that operates as a homodimer with an LeuT-fold transmembrane core containing discrete binding sites for Na⁺, K⁺, and two Cl⁻ ions, and that undergoes alternating-access conformational changes to couple ion translocation [PMID:31367042, PMID:32081947, PMID:36239040]. Transport activity is activated by WNK–SPAK/OSR1 kinase-mediated phosphorylation of N-terminal threonines and suppressed by PP1-type phosphatases, with the phosphoregulatory domain communicating with the C-terminal domain to control conformational transitions; additional regulation occurs through N-glycosylation-dependent surface targeting and aldosterone-mediated protein stabilization [PMID:12740379, PMID:22032326, PMID:35585053, PMID:26351455, PMID:24173102]. Physiologically, NKCC1 localizes to basolateral membranes of secretory epithelia—including airway, colon, sweat gland, and mammary gland—where it drives transepithelial Cl⁻ secretion, and to the apical membrane of choroid plexus epithelium where it mediates CSF K⁺ clearance and volume homeostasis; in neurons, NKCC1 accumulates intracellular Cl⁻ to sustain depolarizing GABA signaling critical for progenitor proliferation and circuit maturation [PMID:11443061, PMID:9038823, PMID:33469018, PMID:23015452, PMID:34058387]. Loss-of-function mutations in SLC12A2 cause sensorineural hearing loss and neurodevelopmental disorders in humans and mice, linked to defective endolymph homeostasis and impaired neuronal Cl⁻ regulation [PMID:10401008, PMID:32658972].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Initial molecular characterization defined the SLC12A2 gene structure, tissue-specific promoter usage, and a brain-specific splice variant lacking a PKA phosphorylation site, establishing the framework for understanding isoform-specific regulation.\",\n      \"evidence\": \"Genomic cloning, RNase protection, primer extension, RT-PCR of splice variants\",\n      \"pmids\": [\"9357771\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct functional consequence of exon 21 exclusion on transport not tested\", \"PKA-mediated regulation of the full-length isoform not demonstrated in vivo\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Localization of NKCC1 to the apical choroid plexus and neuronal cell bodies established its dual epithelial-neuronal expression pattern, implying roles in both CSF ion homeostasis and neuronal Cl⁻ regulation.\",\n      \"evidence\": \"Immunocytochemistry, confocal microscopy, ⁸⁶Rb⁺ transport in polarized choroid plexus cells\",\n      \"pmids\": [\"9038823\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo functional consequence of choroid plexus NKCC1 not yet demonstrated\", \"Mechanism of apical vs. basolateral sorting unknown\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Reconstitution kinetics revealed that NKCC1 activity is governed primarily by intracellular Cl⁻ concentration rather than cell volume, distinguishing it from NKCC2 and defining the sensory logic of cotransporter regulation.\",\n      \"evidence\": \"Stable HEK-293 expression, ⁸⁶Rb uptake kinetics, chimeric constructs, ion substitution\",\n      \"pmids\": [\"9556622\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular sensor for intracellular Cl⁻ not identified\", \"Structural basis of isoform-specific kinetic differences unknown at this time\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Positional cloning of deafness-causing Slc12a2 mutations in mice established NKCC1 as essential for endolymph K⁺ recycling and cochlear function, providing the first in vivo loss-of-function phenotype.\",\n      \"evidence\": \"Positional cloning, mutation identification, phenotyping of sy/sy(ns) deaf mice\",\n      \"pmids\": [\"10401008\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise cell type within stria vascularis mediating the phenotype not resolved\", \"Human disease mutations not yet identified at this time\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"NKCC1 knockout airway studies demonstrated that basolateral NKCC1 is the principal Cl⁻ entry pathway for agonist-stimulated anion secretion, with HCO₃⁻ secretion partially compensating in its absence.\",\n      \"evidence\": \"NKCC1 KO mice, Ussing chamber short-circuit current, bumetanide pharmacology\",\n      \"pmids\": [\"11443061\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contribution of NKCC1 vs. other basolateral Cl⁻ pathways in adult airways not quantified\", \"Compensatory HCO₃⁻ mechanism not molecularly characterized\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Identification of SPAK/PASK as the direct kinase phosphorylating N-terminal threonines of NKCC1 established the core activating kinase–cotransporter axis, with constitutive SPAK–NKCC1 binding and kinase/phosphatase balance controlling activity.\",\n      \"evidence\": \"Co-IP, ³²P phosphorylation, dominant-negative PASK, ⁸⁶Rb uptake, calyculin A rescue in HEK cells\",\n      \"pmids\": [\"12740379\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Upstream kinase activating SPAK not yet connected\", \"Identity of relevant phosphatase not established\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Multiple tissue-specific studies—sweat gland, juxtaglomerular cells—confirmed basolateral NKCC1 as essential for secretory NaCl entry and revealed an unexpected role suppressing basal renin release, broadening the physiological scope of the transporter.\",\n      \"evidence\": \"Immunoelectron microscopy (sweat gland), NKCC1 KO mice + patch-clamp + renin assay (JG cells)\",\n      \"pmids\": [\"15843440\", \"16106034\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How Cl⁻ accumulation mechanistically suppresses renin exocytosis not delineated\", \"Relevance of NKCC1 in human sweat disorders not tested\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"In native human colonic crypts, cholinergic stimulation was shown to trigger a dynamic cycle of NKCC1 membrane recruitment, activation, EGFR-dependent internalization, lysosomal degradation, and re-synthesis, revealing post-translational trafficking as a major regulatory layer.\",\n      \"evidence\": \"Human colonic crypt imaging, ⁸⁶Rb uptake, tyrphostin-AG1478 EGFR inhibitor, cycloheximide, chloroquine\",\n      \"pmids\": [\"17478539\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"EGFR phosphorylation site on NKCC1 or adaptor not identified\", \"Whether this trafficking cycle operates in non-colonic epithelia unknown\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Zebrafish nkcc1 loss-of-function confirmed a conserved requirement for NKCC1 in endolymph volume regulation, extending the cochlear phenotype from mouse and establishing evolutionary conservation.\",\n      \"evidence\": \"ENU mutagenesis, morpholino rescue of splicing defect, otic vesicle volume measurement\",\n      \"pmids\": [\"19633174\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific ionic mechanism by which NKCC1 drives endolymph volume in zebrafish not resolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Genetic placement of SPAK/OSR1 downstream of WNK1 and upstream of NKCC1 via double-knockin ES cells completed the WNK–SPAK/OSR1–NKCC1 signaling cascade, showing SPAK/OSR1 are both necessary and sufficient kinases for NKCC1 activation.\",\n      \"evidence\": \"Double-knockin ES cells (SPAK/OSR1 cannot be activated by WNK1), phospho-specific antibodies, ion transport\",\n      \"pmids\": [\"22032326\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether other WNK family members contribute differentially in specific tissues not resolved\", \"Feedback from SPAK/OSR1 onto WNK activity mechanistically unexplained\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"NKCC1 knockdown in neonatal subventricular zone progenitors demonstrated that NKCC1-mediated Cl⁻ accumulation underlies depolarizing GABA responses required for neural progenitor proliferation and dendritic arborization, with pharmacological GABA_A rescue confirming the mechanism.\",\n      \"evidence\": \"In vivo shRNA electroporation, Ki67 staining, Ca²⁺ imaging, dendritic morphology, pentobarbital rescue\",\n      \"pmids\": [\"23015452\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether NKCC1 also affects migration of SVZ-derived neuroblasts not tested\", \"Long-term circuit consequences of neonatal NKCC1 loss not characterized\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"N-glycosylation was shown to be required for NKCC1 plasma membrane targeting and transport function, with glycan biosynthesis or maturation inhibition eliminating surface NKCC1 and cotransport.\",\n      \"evidence\": \"Tunicamycin, swainsonine, kifunensine treatment, surface biotinylation, ⁸⁶Rb uptake\",\n      \"pmids\": [\"26351455\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific glycosylation sites critical for trafficking not mapped by mutagenesis\", \"Only tested in one cell type\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Discovery of a physical NKCC1–Cofilin-1 interaction linked NKCC1 to actin cytoskeletal remodeling and glioblastoma cell migration via RhoA/Rac1 signaling, expanding NKCC1 function beyond ion transport.\",\n      \"evidence\": \"Co-IP, siRNA knockdown, F-actin staining, Rho-GTPase activity, migration assay, intracranial mouse model\",\n      \"pmids\": [\"28679472\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether ion transport activity is required for migration effect or whether it is a scaffolding function unknown\", \"Reciprocal effect of Cofilin-1 on NKCC1 transport not tested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"The first cryo-EM structure of NKCC1 (zebrafish) defined the LeuT-fold architecture, ion-binding sites for Na⁺, K⁺, and 2Cl⁻, and the ion-translocation pathway, providing the atomic framework for understanding transport mechanism and CCC family function.\",\n      \"evidence\": \"Single-particle cryo-EM, MD simulations, mutagenesis, functional transport assays\",\n      \"pmids\": [\"31367042\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Only one conformational state captured\", \"Drug-binding sites not resolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identification of NKCC1 in a complex with the leucine transporter LAT1 revealed that NKCC1 suppresses mTORC1 signaling and couples cell volume to cell mass regulation, establishing a non-canonical growth-regulatory role.\",\n      \"evidence\": \"Co-IP, CRISPR KO, siRNA, mTORC1 signaling assays, colonic organoids, mouse colon KO\",\n      \"pmids\": [\"31067471\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct vs. indirect nature of NKCC1–LAT1 interaction not structurally resolved\", \"Whether ion transport activity is required for mTORC1 suppression not determined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Human NKCC1 cryo-EM structure in a partially loaded inward-open state revealed dimeric assembly, broken α-helical geometry at ion-binding sites on TM1/TM6, and distinct entryway/exit routes for different ions, refining the transport cycle model.\",\n      \"evidence\": \"Single-particle cryo-EM of human NKCC1\",\n      \"pmids\": [\"32081947\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Outward-facing state not captured in this study\", \"Ion occupancy at individual sites uncertain\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Functional characterization of de novo SLC12A2 mutations from children with neurodevelopmental disorders and hearing loss established loss-of-function as the pathogenic mechanism in human disease, confirming NKCC1 haploinsufficiency as disease-causing.\",\n      \"evidence\": \"Xenopus oocyte expression, ⁸⁶Rb uptake for multiple patient variants, trio exome sequencing\",\n      \"pmids\": [\"32658972\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genotype–phenotype correlations across variant types not fully established\", \"Whether heterozygous loss is sufficient or requires second hit unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Capture of NKCC1 in outward-facing, occluded, and drug-bound conformations completed the structural catalog of the transport cycle, revealed bumetanide/furosemide binding pockets, and showed that N-terminal phosphoregulatory domain–C-terminal domain interaction controls conformational switching.\",\n      \"evidence\": \"Cryo-EM in multiple conformational/drug-bound states, functional mutagenesis, MD simulations\",\n      \"pmids\": [\"35585053\", \"36239040\", \"36306358\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full transport cycle with all ions simultaneously resolved not achieved\", \"How phosphorylation physically disrupts N-term–C-term interaction not structurally captured\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Choroid plexus NKCC1 was shown to be activated by blood-derived K⁺ to clear CSF and prevent post-hemorrhagic ventriculomegaly; a phosphodeficient mutant failed to rescue, demonstrating that phosphorylation-dependent activation is required for CSF homeostasis in disease.\",\n      \"evidence\": \"AAV-mediated ChP-targeted NKCC1 overexpression/phosphodeficient mutant, Ca²⁺ imaging, ventriculometry, CSF K⁺ measurement\",\n      \"pmids\": [\"36893755\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the kinase activated by K⁺-triggered Ca²⁺ signals in choroid plexus not confirmed\", \"Whether NKCC1-targeted therapy is viable in human post-hemorrhagic hydrocephalus untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Outstanding questions include the structural basis of phosphorylation-induced N-terminal–C-terminal domain dissociation, the identity of the Cl⁻ sensor that activates WNK signaling, whether NKCC1's mTORC1-suppressive and migration-promoting roles require ion transport or scaffolding, and the molecular mechanisms underlying NKCC1's role in goblet cell mucus granule exocytosis.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Structural visualization of phosphorylated vs. dephosphorylated regulatory domain interaction\", \"Intracellular Cl⁻ sensor identity linking Cl⁻ to WNK activation\", \"Separation of transport-dependent vs. scaffolding functions in migration and growth signaling\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 1, 2, 3, 4, 41]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [12, 22, 23, 30, 31, 32]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 1, 4, 41]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [6, 7, 18, 34]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [19, 20, 40]}\n    ],\n    \"complexes\": [\n      \"NKCC1 homodimer\"\n    ],\n    \"partners\": [\n      \"SPAK\",\n      \"OSR1\",\n      \"WNK1\",\n      \"CFL1\",\n      \"SLC7A5\",\n      \"TRPV1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}