{"gene":"KCNJ6","run_date":"2026-06-10T02:59:49","timeline":{"discoveries":[{"year":2011,"finding":"Crystal structure of mammalian GIRK2 (homotetrameric) revealed a G-loop gate in the cytoplasmic domain and an inner helix gate in the transmembrane domain. Comparison of wild-type and constitutively active mutant structures showed that G proteins open only the G-loop gate in the absence of PIP2, but in the presence of PIP2 the G-loop and inner helix gates become coupled so both open simultaneously. An intracellular Na+ ion-binding site was also identified, providing a structural basis for Na+-dependent modulation of channel activity.","method":"X-ray crystallography of wild-type and constitutively active mutant GIRK2 in the absence and presence of PIP2","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures of multiple channel states with functional interpretation, single rigorous study with multiple orthogonal structural comparisons and mutagenesis-validated constitutively active mutant","pmids":["21962516"],"is_preprint":false},{"year":2013,"finding":"3.5 Å crystal structure of mammalian GIRK2 in complex with βγ G-protein subunits revealed that four Gβγ subunits bind at interfaces between four K+ channel subunits via short-range atomic and long-range electrostatic interactions, inducing a pre-open state intermediate between closed and fully open conformations. This structure is compatible with membrane-delimited activation and burst kinetics, and shows how PIP2 and Na+ participate in multi-ligand regulation.","method":"X-ray crystallography of GIRK2–Gβγ complex at 3.5 Å resolution","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structure of signaling complex, replicated and consistent with prior structural work from same lab","pmids":["23739333"],"is_preprint":false},{"year":2014,"finding":"Purified mammalian GIRK2 reconstituted in planar lipid bilayers showed that Gβγ and PIP2 must both be present simultaneously to activate the channel. Gαi1(GTPγS) has no activating effect, while Gαi1(GDP) closes the channel by removing Gβγ. Na+ is not essential but modulates Gβγ/PIP2 effects over physiological concentrations. GIRK2 opens as a function of PIP2 mole fraction with Hill coefficient ~2.5.","method":"Reconstitution of purified GIRK2 in planar lipid membranes; patch-clamp electrophysiology with defined purified protein components","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with purified components, multiple orthogonal conditions tested, mechanistically comprehensive","pmids":["25049222"],"is_preprint":false},{"year":2016,"finding":"Using membrane-anchored G protein concentration assays, four Gβγ subunits were shown to bind cooperatively to open GIRK2 (neuronal homomeric channel). Intracellular Na+, which enters neurons during action potentials, amplifies channel opening primarily by increasing Gβγ binding affinity, establishing a dual-input activation mechanism that provides activity-dependent feedback inhibition.","method":"Functional assay of GIRK2 activity vs. membrane-anchored Gβγ concentration in cell-based system; electrophysiology in mouse dopamine neurons","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — quantitative functional reconstitution with defined Gβγ concentrations plus native neuron validation, single lab but multiple orthogonal methods","pmids":["27074662"],"is_preprint":false},{"year":2021,"finding":"Cryo-EM structures of GIRK2 in the presence and absence of cholesterol analog CHS and PIP2 revealed that CHS binds in lipid-facing hydrophobic pockets of the transmembrane domain near the PIP2 binding site. CHS stabilizes PIP2 interaction with the channel and promotes engagement of the cytoplasmic domain onto the transmembrane region. Mutagenesis of one CHS-binding pocket eliminated cholesterol-dependent potentiation.","method":"Cryo-electron microscopy structures of GIRK2 ± CHS ± PIP2; mutagenesis of CHS-binding site with functional assay","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 / Moderate — cryo-EM structures combined with mutagenesis functional validation, single lab but two orthogonal methods","pmids":["34433062"],"is_preprint":false},{"year":1996,"finding":"GIRK2 and GIRK1 co-immunoprecipitate from brain regions where both are expressed (cerebral cortex, hippocampus, cerebellum), demonstrating that they form heteromeric channels in vivo. In weaver mouse brain, GIRK2 expression is dramatically decreased and GIRK1 expression is also disrupted in regions of co-assembly.","method":"Co-immunoprecipitation from rat and mouse brain tissue; immunohistochemistry","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP from native tissue, replicated across brain regions, consistent with expression data","pmids":["8929423"],"is_preprint":false},{"year":1996,"finding":"The weaver mutation (G156S in the H5/pore region of GIRK2) causes constitutive activation, loss of K+ selectivity (increased Na+ permeability), and increased sensitivity to channel blockers when expressed in Xenopus oocytes. Pharmacological blockade of Na+ influx in weaver granule cells rescues their ability to differentiate, establishing that Na+ flux through mutant GIRK2 underlies granule cell development failure.","method":"Xenopus oocyte expression of weaver GIRK2; electrophysiology; pharmacological rescue of weaver cerebellar granule cells in culture","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — heterologous expression electrophysiology combined with pharmacological rescue in primary neurons, replicated across multiple labs","pmids":["8630252"],"is_preprint":false},{"year":1996,"finding":"The weaver G156S mutation in the pore region of GIRK2 causes loss of high K+ selectivity over Na+, resulting in increased basal Na+ permeability and membrane depolarization in Xenopus oocytes. This loss of selectivity persists when weaver GIRK2 is coexpressed with GIRK1.","method":"Xenopus oocyte expression; electrophysiology/ion substitution experiments","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct electrophysiological characterization in heterologous system, replicated by multiple independent labs","pmids":["8706831"],"is_preprint":false},{"year":1997,"finding":"GIRK2 knockout mice lack GABAB receptor-activated inwardly rectifying K+ currents in cerebellar granule cells, and GIRK1 expression is reduced in regions normally co-expressing both subunits. This establishes that GABAB receptors couple to heteromultimers of GIRK1 and GIRK2, and that GIRK2 is required for maintaining GIRK1 protein levels in these complexes.","method":"Electrophysiology of cerebellar granule cells from Girk2 null and weaver mice; Western blot for GIRK1 expression","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean knockout electrophysiology with defined phenotype replicated in two mutant mouse models, consistent with co-IP data from another lab","pmids":["9342388"],"is_preprint":false},{"year":1999,"finding":"In the substantia nigra, GIRK channels are composed only of Kir3.2 (GIRK2) subunits (homotetramers of Kir3.2a and Kir3.2c splice variants), without significant Kir3.1 or Kir3.3 content, and are localized specifically at postsynaptic membranes on dopaminergic neuron dendrites. Kir3.2c, but not Kir3.2a, binds PDZ domain-containing protein PSD-95. Kir3.2a alone or Kir3.2a+Kir3.2c were activated by G-protein stimulation, but Kir3.2c alone was not.","method":"Immunoprecipitation, Western blot, immunohistochemistry, heterologous expression electrophysiology in Xenopus oocytes","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal biochemical and electrophysiological methods, single lab","pmids":["9920664"],"is_preprint":false},{"year":2000,"finding":"GIRK2 and GIRK3 co-assemble to form functional heteromultimeric K+ channels in brain. Co-expressed GIRK2/GIRK3 channels showed ~5-fold lower sensitivity to activation by Gβγ compared to GIRK1/GIRKx channels. Complexes containing only GIRK2 and GIRK3 were immunoprecipitated from transfected cells and purified from native brain tissue.","method":"Co-transfection in CHO-K1 cells; patch-clamp electrophysiology; co-immunoprecipitation from transfected cells and native brain","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP from both heterologous and native tissue plus functional electrophysiology, single lab","pmids":["10956667"],"is_preprint":false},{"year":2003,"finding":"Gβγ binds to both the N-terminus and a segment of the C-terminus (~residues 320–409 by GIRK1 count, corresponding residues in GIRK2) of GIRK2. The Gβγ-binding sites in GIRK1 and GIRK2 C-termini are not identical; GIRK1 has an additional binding segment in the first half of its C-terminus that GIRK2 lacks. Key leucine residues (L273, L344 in GIRK2) are important for Gβγ-induced gating changes rather than Gβγ binding per se.","method":"Pull-down binding assays with GIRK subunit fragments; competition assays with Gαi1; mutagenesis with functional electrophysiology in Xenopus oocytes","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — direct binding assays combined with mutagenesis and functional electrophysiology, single lab with multiple orthogonal methods","pmids":["12743112"],"is_preprint":false},{"year":2009,"finding":"The GDP-bound form of Gαi3 (inactive state) regulates GIRK1-containing heteromeric channels by forming heterotrimers and reducing basal activity while increasing Gβγ-evoked current. This Gαi3-GDP regulation is unique to GIRK1 subunit-containing channels; homomeric GIRK2 channels are insensitive to Gαi3GDP. In vitro binding showed Gβγ enhances binding of Gαi3GDP to the cytosolic domain of GIRK1 but not GIRK2. The distal C-terminus of GIRK1 confers this differential regulation.","method":"Electrophysiology in Xenopus oocytes with coexpression of constitutively inactive/active Gα mutants; in vitro pull-down protein interaction assays; chimeric GIRK1/GIRK2 constructs","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro binding + heterologous electrophysiology + chimeric constructs, multiple orthogonal methods in single lab","pmids":["19470775"],"is_preprint":false},{"year":1997,"finding":"GIRK2 knockout mice develop spontaneous seizures and are more susceptible to pharmacologically induced seizures (GABA antagonist), demonstrating that GIRK2 is required for normal neuronal excitability. GIRK2-null mice have normal cerebellar morphology but dramatically reduced GIRK1 expression in brain, unlike weaver mice. Weaver heterozygotes show milder cerebellar abnormalities than homozygotes, establishing a dosage-dependent gain-of-function mechanism for the weaver mutation.","method":"Gene knockout (homologous recombination), behavioral seizure testing, pharmacological seizure induction, immunohistochemistry","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined electrophysiological/behavioral phenotype, multiple orthogonal methods, widely replicated","pmids":["9023358"],"is_preprint":false},{"year":2002,"finding":"GIRK2 knockout mice showed largely eliminated clonidine antinociception and significantly reduced morphine antinociception, establishing that postsynaptic GIRK2-mediated signaling is the primary effector for α2-adrenergic receptor analgesia and a major contributor to opioid analgesia. GIRK2 deletion eliminated sex differences in pain threshold, with greater impact in male mice.","method":"GIRK2 knockout mice; spinal reflex nociceptive testing (tail-flick); intrathecal drug administration","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with well-defined pharmacological phenotype, replicated across multiple analgesic drugs","pmids":["12496346"],"is_preprint":false},{"year":2002,"finding":"GIRK2 knockout reduces or eliminates antinociceptive effects of ethanol, oxotremorine, nicotine, baclofen, clonidine, and cannabinoid agonist WIN 55,212 (but not ketamine), establishing that opioid, α-adrenergic, muscarinic cholinergic, GABAB, and cannabinoid receptors are coupled to postsynaptic GIRK2 channels in vivo. GIRK2 also mediates the opioid-dependent component of stress-induced analgesia.","method":"GIRK2 knockout mice; hot plate analgesia test; stress-induced analgesia paradigm","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with multiple drugs tested via consistent phenotypic readout, broad pharmacological validation","pmids":["12493843"],"is_preprint":false},{"year":2002,"finding":"In locus coeruleus neurons, acute opioid-induced hyperpolarization is mediated primarily by G-protein-gated K+ channels containing Kir3.2 (GIRK2) and Kir3.3 subunits. [Met5]enkephalin-induced hyperpolarization was reduced by 40% in Kir3.2 KO neurons and by 80% in Kir3.2/Kir3.3 double KO neurons, with residual current nearly eliminated by K+ channel blockers Ba2+/Cs2+. This established that the cAMP-dependent cation conductance does not contribute significantly to acute opioid inhibition of LC neurons.","method":"Brain slice electrophysiology from Kir3.2 KO, Kir3.3 KO, and Kir3.2/3.3 double KO mice","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO electrophysiology with pharmacological dissection, genetically validated subunit contributions","pmids":["12040038"],"is_preprint":false},{"year":2004,"finding":"Spinal GIRK channels composed primarily of GIRK1/GIRK2 complexes modulate thermal nociception and mediate a significant component of intrathecal high-dose morphine analgesia. GIRK1 or GIRK2 knockout each reduces expression of the other subunit in spinal cord, confirming physical interaction between subunits. The GIRK channel blocker tertiapin reproduced the knockout phenotype in wild-type mice.","method":"GIRK1 and GIRK2 knockout mice; tail-flick thermal nociception test; intrathecal drug delivery; Western blot; tertiapin pharmacology","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — parallel KO lines + pharmacological validation + biochemical subunit interaction evidence, multiple orthogonal methods","pmids":["15028774"],"is_preprint":false},{"year":2006,"finding":"In hippocampal pyramidal cells, Kir3.2-containing channels are enriched around glutamatergic synapses on dendritic spines and co-cluster with GABAB1 receptors at these sites, while on dendritic shafts Kir3.2 and GABAB1 are largely segregated. This compartment-dependent colocalization suggests that spine Kir3.2 channels preferentially mediate GABA effects while shaft channels are activated by other neurotransmitters.","method":"High-resolution immunocytochemistry; quantitative immunogold analysis; SDS-digested freeze-fracture replica immunolabeling (SDS-FRL)","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Moderate — high-resolution quantitative subcellular localization with SDS-FRL, co-clustering analysis with receptor, single lab but rigorous methodology","pmids":["16624949"],"is_preprint":false},{"year":1999,"finding":"GIRK2 splice variant Kir3.2c binds the PDZ domain-containing scaffolding protein PSD-95 (demonstrated by co-immunoprecipitation), while Kir3.2a does not, providing a mechanism for selective postsynaptic localization of Kir3.2c-containing channels to dendritic membranes. Kir3.2c is specifically localized to acrosomal vesicles in testicular spermatids.","method":"Co-immunoprecipitation; immunohistochemistry; heterologous expression in Xenopus oocytes and HEK293T cells","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP demonstrating PDZ interaction with localization data, single lab with multiple methods","pmids":["9920664"],"is_preprint":false},{"year":2012,"finding":"Conformational rearrangements at the Gβγ-Kir3.1 (GIRK1) subunit interface upon δ-opioid receptor activation were detected by BRET, with DORs, Gβγ, and Kir3 subunits forming a constitutive complex. Conformational changes at the Gβγ/Kir3 interface were predictive of ligand ability to evoke channel currents, and were lost when Kir3.1 was replaced by a mutant lacking Gβγ-activation sites. GαoA did not directly associate with the channel despite being part of the complex.","method":"Bioluminescence resonance energy transfer (BRET) in HEK293 cells; co-immunoprecipitation; pertussis toxin treatment; mutagenesis","journal":"Molecular pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — BRET and co-IP with mutagenesis, single lab, Kir3.2-containing heteromeric channel studied as Kir3.1/Kir3.2 complex","pmids":["23175530"],"is_preprint":false},{"year":2000,"finding":"RGS4 (a GTPase-activating protein) reduces basal GIRK1/GIRK2 current, accelerates channel deactivation kinetics, and abolishes the post-agonist reduction of basal conductance seen without RGS4 when co-expressed with kappa-opioid receptor in Xenopus oocytes. This establishes that RGS4 gates the duration and extent of GIRK1/GIRK2 channel activation by controlling G-protein GTPase activity.","method":"Co-expression in Xenopus oocytes; two-electrode voltage-clamp electrophysiology","journal":"Life sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — electrophysiology in heterologous system, single lab, single method","pmids":["11065178"],"is_preprint":false},{"year":1999,"finding":"Kappa-opioid receptor couples to GIRK1/GIRK2 heteromeric channels. At nanomolar concentrations, U50488H activates GIRK1/GIRK2 via receptor-mediated pathway; at micromolar concentrations, U50488H, propoxyphene, methadone, and naloxone block GIRK1/GIRK2 by direct voltage-independent channel block (IC50 70 µM for U50488H). Morphine did not block at concentrations up to 1 mM. The related IRK1 channel was not affected.","method":"Xenopus oocyte expression; two-electrode voltage-clamp electrophysiology; ion substitution","journal":"European journal of pharmacology","confidence":"Medium","confidence_rationale":"Tier 1–2 / Weak — in vitro functional assay with dose-response, single lab","pmids":["10607882"],"is_preprint":false},{"year":1999,"finding":"GIRK1 rescues the weaver GIRK2 (G156S) phenotype by restoring K+ selectivity and G-protein dependence in a subunit-position-dependent manner. When two GIRK2wv subunits are arranged adjacently in a tetramer, currents remain weaver-like; alternating GIRK1-GIRK2wv tetramers restore wild-type K+-selective currents. This provides a structural basis for selective neuronal vulnerability in weaver mice.","method":"Xenopus oocyte expression of tandem dimers and linked tetramers; two-electrode voltage-clamp electrophysiology","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with engineered subunit arrangements, single lab but mechanistically informative","pmids":["10493734"],"is_preprint":false},{"year":2015,"finding":"De novo heterozygous mutations in KCNJ6 (GIRK2) cause Keppen-Lubinsky syndrome. An in-frame deletion (p.Thr152del) and a missense mutation (p.Gly154Ser) in the pore region were identified in three unrelated affected individuals, establishing this condition as a channelopathy caused by severely impaired KCNJ6 channel function.","method":"Whole-exome sequencing of three unrelated KPLBS patients; genotype-phenotype correlation with animal model data","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — exome sequencing identifying de novo mutations at functionally critical pore residues, consistent with functional characterization in animal models, no direct functional assay in this paper","pmids":["25620207"],"is_preprint":false},{"year":2018,"finding":"A de novo heterozygous KCNJ6 mutation p.Leu171Arg causes a gain-of-function: heterologous expression of mutant GIRK2 produces an aberrant basal inward current that is G-protein-independent, loses K+ selectivity, gains Ca2+ permeability, and is inhibited by the Na+ channel blocker QX-314 (similar to weaver). Expression of GIRK1-GIRK2(L171R) tandem dimer produces no current, suggesting non-functional heterotetramers.","method":"Whole-exome sequencing; heterologous expression in Xenopus oocytes or HEK cells; patch-clamp electrophysiology; pharmacological characterization","journal":"Neuroscience","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro functional characterization with defined pharmacological and biophysical properties, multiple mutant constructs tested","pmids":["29852244"],"is_preprint":false},{"year":2013,"finding":"GIRK2 channels are necessary and sufficient for peripheral opioid analgesia. GIRK channels are absent from mouse peripheral sensory neurons but present in human and rat. Transgenic expression of GIRK channels in mouse nociceptors established peripheral opioid signaling and local analgesia. A regulatory element in the rat GIRK2 gene accounts for differential expression in rodent sensory neurons.","method":"Transgenic mouse expression of GIRK in nociceptors; in vivo pain behavioral assays; immunohistochemistry in human/rat/mouse sensory neurons; regulatory element analysis","journal":"EMBO molecular medicine","confidence":"High","confidence_rationale":"Tier 2 / Moderate — gain-of-function transgenic with defined behavioral rescue, species comparison with molecular mechanism for differential expression","pmids":["23818182"],"is_preprint":false},{"year":2019,"finding":"Molecular dynamics simulations using the GIRK2 crystal structure revealed that Na+ ions control the cytosolic (G-loop) gate through an anti-clockwise rotation of the cytoplasmic domain, while Gβγ stabilizes the transmembrane inner helix gate in the open state through a rocking movement of the cytoplasmic domain. Both effects alter channel interaction with PIP2 to stabilize respective open states.","method":"All-atom microsecond-scale molecular dynamics simulations based on GIRK2 crystal structures","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — computational modeling only with no direct mutagenesis validation in this paper; consistent with crystal structure data","pmids":["31659119"],"is_preprint":false},{"year":2020,"finding":"Native mass spectrometry and fluorescent lipid binding assays showed PIP2 (PIP(4,5)P2) cooperatively binds GIRK2 with Hill coefficient of 2.7. Single mutations at specific Kir3.2 residues distinctly alter PIP isoform selectivity: K64Q alters binding profiles favoring specific PIP(4,5)P2 acyl chains, R92P (equivalent to Kir6.2 residue) causes promiscuous binding, and K194A creates preference for PIP(3,4,5)P3.","method":"Native mass spectrometry; fluorescent lipid binding assays; site-directed mutagenesis","journal":"Biochemistry","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — direct biophysical binding measurements with mutagenesis, two orthogonal methods, single lab","pmids":["32372643"],"is_preprint":false},{"year":1996,"finding":"A novel GIRK2 splice variant (GIRK2B) has a shorter C-terminus differing in only the last 8 amino acids from GIRK2A. When co-injected with GIRK1 and m2-receptor in Xenopus oocytes, GIRK2B dramatically enhances acetylcholine-induced inwardly rectifying K+ current, demonstrating it forms functional heteromultimeric G-protein-gated K+ channels with GIRK1.","method":"cDNA library cloning; RT-PCR tissue distribution; Xenopus oocyte co-expression electrophysiology","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — functional heterologous expression showing channel activity, single lab","pmids":["8573147"],"is_preprint":false},{"year":2017,"finding":"GIRK2 isoforms GIRK2a and GIRK2c support comparable somato-dendritic GIRK currents in hippocampal pyramidal neurons, but GIRK2c achieves more uniform subcellular distribution and better supports inhibitory postsynaptic currents in distal dendrites. GIRK2a over-expression additionally enhanced cue fear learning, while both isoforms restored contextual fear learning in Girk2-null pyramidal neurons.","method":"Viral-mediated expression of individual GIRK2 isoforms in Girk2-/- hippocampal neurons; patch-clamp electrophysiology; immunofluorescence; fear conditioning behavioral assays","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (electrophysiology, imaging, behavior) with isoform-specific comparisons, single lab","pmids":["28487514"],"is_preprint":false},{"year":2008,"finding":"Transgenic mice overexpressing human KCNJ6 (Kir3.2/GIRK2) show increased Kir3.2 protein in atria (2.5-fold) and enhanced chronotropic responses to muscarinic (carbachol, methoxamine) and adenosinergic (CCPA) stimulation, demonstrating that KCNJ6 overexpression alters cardiac rate control specifically at sino-atrial node and atria.","method":"Transgenic mouse model with human KCNJ6; ECG recording under urethane anesthesia; pharmacological challenge","journal":"Physiological genomics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — transgenic gain-of-function with defined cardiac phenotype and pharmacological dissection, single lab","pmids":["18303085"],"is_preprint":false},{"year":2017,"finding":"Increased Kcnj6 gene dose is necessary for synaptic and cognitive dysfunction in the Ts65Dn mouse model of Down syndrome. Reduction of Kcnj6 from 3 to 2 copies in Ts65Dn mice restored hippocampal Kir3.2 protein to normal levels, improved long-term memory, and rescued short-term and long-term potentiation in the dentate gyrus. Fluoxetine, which suppresses Kir3.2 channels, also rescued synaptic plasticity.","method":"Genetic reduction of Kcnj6 copy number in Ts65Dn mice; novel object recognition test; hippocampal slice electrophysiology (STP, LTP); fluoxetine pharmacology","journal":"Neurobiology of disease","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic epistasis (copy number normalization) with defined synaptic and behavioral rescue plus pharmacological validation, single lab","pmids":["28342823"],"is_preprint":false},{"year":2016,"finding":"Deletion of GIRK2 subunit increases basal firing rate of dorsal raphe neurons and causes desensitization of 5-HT1A receptors, demonstrated by lower sensitivity of dorsal raphe neurons to inhibitory effects of 5-HT1A agonist 8-OH-DPAT and citalopram. GIRK2 knockout mice show a depression-resistant behavioral phenotype.","method":"In vivo extracellular recordings from dorsal raphe neurons in GIRK2 KO mice; GIRK channel blocker tertiapin-Q; behavioral depression tests","journal":"The international journal of neuropsychopharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO electrophysiology with pharmacological validation using channel blocker, functional link established","pmids":["25956878"],"is_preprint":false},{"year":2023,"finding":"GIRK2 expressed in NPY/AgRP neurons stabilizes their excitability; conditional deletion of GIRK2 from AgRP neurons increases their persistent excitability, leading to decreased sympathetic activity and energy expenditure (not food intake), resulting in increased body weight and adiposity. Compromised cold adaptation was also observed.","method":"AgRP neuron-selective GIRK2 conditional knockout mice; electrophysiology; metabolic phenotyping; sympathetic activity measurement","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — cell-type-specific conditional KO with defined metabolic and electrophysiological phenotype, multiple orthogonal measurements","pmids":["37594983"],"is_preprint":false},{"year":2014,"finding":"A novel GIRK2 activator (N5) identified from tethered protein scaffold library selection increases Kir3.2 basal activity by inhibiting clearance of the channel from the cell surface (reducing internalization), rather than affecting core biophysical channel properties.","method":"Tethered protein display selection in yeast; functional assay; cell surface expression quantification","journal":"ACS chemical neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — functional selection with cell surface trafficking assay, single lab, novel mechanism but limited mechanistic depth in abstract","pmids":["25028803"],"is_preprint":false},{"year":2022,"finding":"KCNJ6 noncoding variants in AUD subjects reduce GIRK2 expression in iPSC-derived glutamatergic neurons, causing increased neurite area and elevated neuronal excitability. Ethanol at intoxicating concentrations induces GIRK2 expression and reverses these functional effects. Ectopic overexpression of GIRK2 alone mimics the ethanol effect to normalize excitability, establishing GIRK2 as the molecular effector linking KCNJ6 variants to altered neuronal excitability and ethanol response.","method":"iPSC-derived neurons from AUD patients; single-cell RNA sequencing; patch-clamp electrophysiology; morphological analysis; GIRK2 overexpression","journal":"Molecular psychiatry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — patient-derived neurons with multiple orthogonal readouts and rescue experiment, single lab","pmids":["36207584"],"is_preprint":false}],"current_model":"KCNJ6/GIRK2 encodes an inwardly rectifying K+ channel subunit that forms homo- or heterotetramers (with GIRK1, GIRK3) and is activated by a dual obligatory requirement for both Gβγ (binding cooperatively at subunit interfaces) and PIP2 (binding at the transmembrane-cytoplasmic domain interface), with intracellular Na+ serving as an amplifier of Gβγ affinity; crystal and cryo-EM structures have defined two sequential gates (a cytoplasmic G-loop gate controlled by Na+ and a transmembrane inner helix gate stabilized by Gβγ), cholesterol binding near PIP2 stabilizes channel opening, and the channel serves as the principal postsynaptic effector coupling inhibitory GPCRs (GABAB, μ/δ/κ opioid, α2-adrenergic, muscarinic, cannabinoid, serotonin 5-HT1A, adenosine A1) to neuronal hyperpolarization, with critical physiological roles in nociception, analgesia, cardiac rate control, neuronal excitability, and energy homeostasis."},"narrative":{"mechanistic_narrative":"KCNJ6 encodes GIRK2 (Kir3.2), the principal neuronal subunit of G-protein-gated inwardly rectifying K+ channels that couple inhibitory GPCRs to membrane hyperpolarization and thereby set neuronal excitability across multiple circuits [PMID:9342388, PMID:12040038]. GIRK2 assembles into functional tetramers as homomers in dopaminergic substantia nigra neurons and as heteromers with GIRK1 or GIRK3 in cortex, hippocampus, and cerebellum, where loss of GIRK2 destabilizes the partner subunit [PMID:8929423, PMID:9342388, PMID:9920664, PMID:10956667]. Channel opening requires the simultaneous, obligatory presence of both Gβγ and PIP2: reconstitution of purified GIRK2 in lipid bilayers showed neither ligand alone activates the channel, and Gαi(GDP) closes it by sequestering Gβγ [PMID:25049222]. Crystal and Gβγ-complex structures defined two sequential gates — a cytoplasmic G-loop gate and a transmembrane inner-helix gate — with four Gβγ subunits binding cooperatively at subunit interfaces to drive a pre-open state, and an intracellular Na+ site that amplifies Gβγ affinity to provide activity-dependent feedback inhibition [PMID:21962516, PMID:23739333, PMID:27074662]. Cholesterol/CHS binds adjacent to the PIP2 site and stabilizes channel opening, while PIP2 itself binds cooperatively with isoform-selective residues controlling lipid specificity [PMID:34433062, PMID:32372643]. Through these inputs GIRK2 serves as the postsynaptic effector for GABAB, opioid, α2-adrenergic, muscarinic, cannabinoid, adenosine, and 5-HT1A receptors, mediating analgesia, neuronal excitability control, cardiac rate modulation, mood regulation, and energy homeostasis [PMID:12496346, PMID:12493843, PMID:12040038, PMID:18303085, PMID:25956878, PMID:37594983]. De novo pore-region mutations in KCNJ6 cause Keppen-Lubinsky syndrome, and a gain-of-function pore mutation produces an aberrant, non-selective basal current mirroring the classic weaver phenotype [PMID:25620207, PMID:29852244, PMID:8630252].","teleology":[{"year":1996,"claim":"Established that GIRK2 is a physiological channel subunit that physically assembles with GIRK1 in vivo and whose pore mutation underlies a neurodevelopmental disease, answering what GIRK2 partners with and how its dysfunction causes pathology.","evidence":"Reciprocal co-IP from rat/mouse brain and Xenopus oocyte electrophysiology of the weaver G156S pore mutant with pharmacological rescue of granule cells","pmids":["8929423","8630252","8706831"],"confidence":"High","gaps":["Stoichiometry of native heteromers not resolved","Mechanism by which GIRK2 stabilizes GIRK1 protein levels unknown"]},{"year":1996,"claim":"Defined GIRK2 splice variants and showed GIRK2B forms functional G-protein-gated channels with GIRK1, addressing isoform diversity at the channel level.","evidence":"cDNA cloning and Xenopus oocyte co-expression with GIRK1 and m2 receptor","pmids":["8573147"],"confidence":"Medium","gaps":["In vivo role of GIRK2B not established","Single-lab functional characterization"]},{"year":1997,"claim":"Demonstrated genetically that GIRK2 is the obligatory effector for GABAB receptor-activated K+ currents and is required for normal neuronal excitability, linking the channel to inhibitory neurotransmission and seizure susceptibility.","evidence":"Girk2 knockout mouse electrophysiology in cerebellar granule cells and behavioral seizure testing","pmids":["9342388","9023358"],"confidence":"High","gaps":["Does not dissect contributions of individual heteromeric partners","Circuit-level basis of seizures not mapped"]},{"year":1999,"claim":"Resolved the molecular subunit composition and postsynaptic targeting of native GIRK2 channels, showing homomeric Kir3.2 in substantia nigra and PSD-95 binding by the Kir3.2c splice variant for dendritic localization.","evidence":"IP/Western, immunohistochemistry, and heterologous electrophysiology of Kir3.2a/c splice variants; co-IP with PSD-95","pmids":["9920664","9920664"],"confidence":"Medium","gaps":["Single-lab co-IP for PSD-95 interaction","Functional consequence of acrosomal localization unexplored"]},{"year":1999,"claim":"Used engineered subunit arrangements to explain selective neuronal vulnerability, showing GIRK1 rescues the weaver pore defect in a position-dependent manner.","evidence":"Xenopus oocyte expression of tandem dimers and linked tetramers","pmids":["10493734"],"confidence":"Medium","gaps":["Native subunit arrangement not directly observed","Single-lab reconstitution"]},{"year":2000,"claim":"Showed GIRK2/GIRK3 heteromers form in brain and that RGS proteins gate the kinetics and duration of GIRK1/GIRK2 activation, extending the channel's regulatory and partner repertoire.","evidence":"Co-IP from transfected cells and native brain plus CHO patch-clamp; Xenopus oocyte voltage-clamp with RGS4 and kappa-opioid receptor","pmids":["10956667","11065178"],"confidence":"Medium","gaps":["RGS4 evidence from single heterologous study","Physiological role of GIRK2/GIRK3 heteromers in vivo unclear"]},{"year":2002,"claim":"Established GIRK2 as the dominant postsynaptic effector mediating analgesia from multiple GPCRs and acute opioid hyperpolarization, defining its in vivo pharmacological coupling.","evidence":"Girk2 (and Kir3.3) knockout mice in nociceptive behavioral assays and locus coeruleus slice electrophysiology with multiple agonists","pmids":["12496346","12493843","12040038"],"confidence":"High","gaps":["Relative contribution of each receptor to specific circuits not fully resolved","Sex-difference mechanism not defined"]},{"year":2003,"claim":"Mapped the Gβγ-binding determinants in GIRK2 N- and C-termini and distinguished binding from gating residues, clarifying the molecular basis of G-protein activation.","evidence":"Pull-down binding assays with subunit fragments, Gαi1 competition, and mutagenesis with Xenopus oocyte electrophysiology","pmids":["12743112"],"confidence":"High","gaps":["Structural basis of binding-vs-gating distinction not resolved in this work","Single-lab study"]},{"year":2004,"claim":"Demonstrated spinal GIRK1/GIRK2 channels mediate thermal nociception and high-dose morphine analgesia, with reciprocal subunit dependence confirming physical interaction.","evidence":"GIRK1 and GIRK2 knockout mice in tail-flick assays with intrathecal drug delivery, Western blot, and tertiapin pharmacology","pmids":["15028774"],"confidence":"High","gaps":["Cellular site of spinal GIRK action not pinpointed"]},{"year":2006,"claim":"Revealed compartment-specific subcellular targeting, with spine Kir3.2 co-clustering with GABAB receptors while shaft channels segregate, suggesting input-specific signaling.","evidence":"Quantitative immunogold and SDS-FRL in hippocampal pyramidal cells","pmids":["16624949"],"confidence":"High","gaps":["Functional consequence of compartmentalization not directly tested electrophysiologically","Single-lab analysis"]},{"year":2008,"claim":"Showed KCNJ6 overexpression alters cardiac rate control at the sino-atrial node, extending GIRK2 function beyond the CNS.","evidence":"Transgenic human-KCNJ6 mice with ECG and muscarinic/adenosinergic pharmacological challenge","pmids":["18303085"],"confidence":"Medium","gaps":["Endogenous cardiac GIRK2 contribution not assessed by loss-of-function","Single-lab study"]},{"year":2009,"claim":"Identified GIRK1-specific regulation by Gαi3-GDP, distinguishing heteromer-specific tuning from GIRK2-intrinsic gating.","evidence":"Xenopus oocyte electrophysiology with Gα mutants, in vitro pull-down, and GIRK1/GIRK2 chimeras","pmids":["19470775"],"confidence":"High","gaps":["Does not address GIRK2-homomer regulation, which is insensitive"]},{"year":2011,"claim":"Provided the first structural framework for gating, defining two gates and a Na+ site and showing PIP2 couples the G-loop and inner-helix gates.","evidence":"X-ray crystallography of wild-type and constitutively active GIRK2 with and without PIP2","pmids":["21962516"],"confidence":"High","gaps":["Gβγ engagement not yet visualized structurally at this stage"]},{"year":2012,"claim":"Captured dynamic conformational rearrangements at the Gβγ/Kir3 interface upon receptor activation in a pre-formed signaling complex, linking ligand efficacy to channel gating.","evidence":"BRET, co-IP, pertussis toxin, and mutagenesis in HEK293 cells (Kir3.1/Kir3.2 heteromer)","pmids":["23175530"],"confidence":"Medium","gaps":["Performed on GIRK1-containing heteromers","Single-lab live-cell biosensor data"]},{"year":2013,"claim":"Solved the GIRK2–Gβγ complex structure, showing four Gβγ binding cooperatively at subunit interfaces to induce a pre-open intermediate, and established GIRK2 sufficiency for peripheral opioid analgesia.","evidence":"3.5 Å crystallography of the GIRK2–Gβγ complex; transgenic GIRK expression in mouse nociceptors with behavioral assays and cross-species immunohistochemistry","pmids":["23739333","23818182"],"confidence":"High","gaps":["Full open-state transition from pre-open not captured","Determinants of species-specific sensory expression only partially mapped"]},{"year":2014,"claim":"Reconstituted the obligatory dual Gβγ+PIP2 activation requirement with purified components and identified a trafficking-based pharmacological activation mechanism.","evidence":"Planar lipid bilayer reconstitution of purified GIRK2 with patch-clamp; tethered protein scaffold selection of activator N5","pmids":["25049222","25028803"],"confidence":"High","gaps":["N5 mechanism described only at the level of internalization","Cooperativity origin (Hill ~2.5) not structurally explained"]},{"year":2015,"claim":"Established KCNJ6 as a Mendelian disease gene, linking pore-region de novo mutations to Keppen-Lubinsky syndrome.","evidence":"Whole-exome sequencing of three unrelated patients with genotype-phenotype correlation to animal models","pmids":["25620207"],"confidence":"Medium","gaps":["No direct functional assay of patient mutations in this study","Loss- vs gain-of-function consequence not biophysically tested here"]},{"year":2016,"claim":"Quantified the cooperative dual-input mechanism, showing Na+ amplifies channel opening by increasing Gβγ affinity to provide activity-dependent feedback, and linked GIRK2 to serotonergic autoinhibition.","evidence":"Membrane-anchored Gβγ concentration assays with dopamine-neuron electrophysiology; dorsal raphe in vivo recordings in Girk2 KO with tertiapin-Q and behavior","pmids":["27074662","25956878"],"confidence":"High","gaps":["Native concentrations of Gβγ/Na+ during physiological firing not directly measured","Antidepressant-resistance mechanism only correlative"]},{"year":2017,"claim":"Defined isoform-specific subcellular distribution and behavioral roles, and demonstrated Kcnj6 gene dosage drives Down-syndrome synaptic and cognitive dysfunction.","evidence":"Viral isoform expression in Girk2-null hippocampal neurons with electrophysiology and fear conditioning; genetic copy-number reduction in Ts65Dn mice with LTP and memory assays plus fluoxetine pharmacology","pmids":["28487514","28342823"],"confidence":"High","gaps":["Molecular basis of isoform distribution differences incompletely defined"]},{"year":2018,"claim":"Showed a de novo pore mutation produces a weaver-like gain-of-function with loss of K+ selectivity and gained Ca2+ permeability, defining a pathogenic mechanism distinct from simple loss of function.","evidence":"Whole-exome sequencing and heterologous expression of the L171R mutant with patch-clamp and QX-314 pharmacology","pmids":["29852244"],"confidence":"High","gaps":["In vivo phenotype of L171R not modeled","Heterotetramer non-functionality inferred from tandem dimer only"]},{"year":2020,"claim":"Resolved PIP2 cooperativity and isoform selectivity at the residue level, refining how lipid identity tunes GIRK2 activation.","evidence":"Native mass spectrometry and fluorescent lipid binding assays with site-directed mutagenesis","pmids":["32372643"],"confidence":"Medium","gaps":["Physiological relevance of altered PIP isoform selectivity not tested in cells","Single-lab biophysical data"]},{"year":2021,"claim":"Identified cholesterol as a structural modulator binding near PIP2 to stabilize the open state, integrating lipid environment into the gating model.","evidence":"Cryo-EM of GIRK2 ± CHS ± PIP2 with mutagenesis of the CHS pocket and functional validation","pmids":["34433062"],"confidence":"High","gaps":["Native cholesterol regulation in neurons not directly demonstrated"]},{"year":2023,"claim":"Defined a cell-type-specific role in energy homeostasis, showing GIRK2 stabilizes AgRP neuron excitability to control sympathetic tone and energy expenditure.","evidence":"AgRP-selective conditional Girk2 knockout with electrophysiology, metabolic phenotyping, and sympathetic activity measurement","pmids":["37594983"],"confidence":"High","gaps":["Upstream GPCR driving AgRP GIRK2 signaling not identified"]},{"year":2023,"claim":"Linked KCNJ6 regulatory variants to alcohol-use phenotypes via GIRK2 expression-dependent control of human neuronal excitability.","evidence":"iPSC-derived glutamatergic neurons from AUD patients with single-cell RNA-seq, patch-clamp, morphology, and GIRK2 overexpression rescue","pmids":["36207584"],"confidence":"Medium","gaps":["Causal noncoding variant mechanism not fully defined","In vivo relevance to AUD not established"]},{"year":null,"claim":"How the sequential gates, multi-ligand cooperativity, and isoform/partner-specific tuning are integrated dynamically in native circuits to produce precise context-dependent inhibition remains unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No native-membrane structure of a fully open GPCR–Gβγ–GIRK2 signaling complex","Quantitative in vivo dynamics of Na+/Gβγ/PIP2 co-regulation during firing unmeasured","Direct functional assays of most disease mutations lacking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[2,6,7,8,16]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[2,4,28]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[8,16,33]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,1,5,10]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[2,9,18,35]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[19]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,3,11,16]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[8,13,16,18]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[34]}],"complexes":["GIRK1/GIRK2 heterotetramer","GIRK2 homotetramer","GIRK2/GIRK3 heterotetramer","GPCR-Gβγ-GIRK2 signaling complex"],"partners":["KCNJ3","KCNJ9","GNB1","GNG2","GNAI3","DLG4","RGS4","GABBR1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P48051","full_name":"G protein-activated inward rectifier potassium channel 2","aliases":["BIR1","Inward rectifier K(+) channel Kir3.2","KATP-2","Potassium channel, inwardly rectifying subfamily J member 6"],"length_aa":423,"mass_kda":48.5,"function":"Inward rectifier potassium channels are characterized by a greater tendency to allow potassium to flow into the cell rather than out of it. Their voltage dependence is regulated by the concentration of extracellular potassium; as external potassium is raised, the voltage range of the channel opening shifts to more positive voltages. The inward rectification is mainly due to the blockage of outward current by internal magnesium. This potassium channel may be involved in the regulation of insulin secretion by glucose and/or neurotransmitters acting through G-protein-coupled receptors","subcellular_location":"Membrane","url":"https://www.uniprot.org/uniprotkb/P48051/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KCNJ6","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/KCNJ6","total_profiled":1310},"omim":[{"mim_id":"614098","title":"KEPPEN-LUBINSKY SYNDROME; KPLBS","url":"https://www.omim.org/entry/614098"},{"mim_id":"602106","title":"POTASSIUM CHANNEL, INWARDLY RECTIFYING, SUBFAMILY J, MEMBER 15; KCNJ15","url":"https://www.omim.org/entry/602106"},{"mim_id":"601534","title":"POTASSIUM CHANNEL, INWARDLY RECTIFYING, SUBFAMILY J, MEMBER 3; KCNJ3","url":"https://www.omim.org/entry/601534"},{"mim_id":"600877","title":"POTASSIUM CHANNEL, INWARDLY RECTIFYING, SUBFAMILY J, MEMBER 6; KCNJ6","url":"https://www.omim.org/entry/600877"},{"mim_id":"168600","title":"PARKINSON DISEASE, LATE-ONSET; PD","url":"https://www.omim.org/entry/168600"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"brain","ntpm":5.0},{"tissue":"pituitary gland","ntpm":1.7}],"url":"https://www.proteinatlas.org/search/KCNJ6"},"hgnc":{"alias_symbol":["Kir3.2","GIRK2","KATP2","BIR1","hiGIRK2"],"prev_symbol":["KCNJ7"]},"alphafold":{"accession":"P48051","domains":[{"cath_id":"1.10.287.70","chopping":"70-194","consensus_level":"medium","plddt":93.9164,"start":70,"end":194},{"cath_id":"2.60.40.1400","chopping":"198-372","consensus_level":"high","plddt":94.9336,"start":198,"end":372}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P48051","model_url":"https://alphafold.ebi.ac.uk/files/AF-P48051-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P48051-F1-predicted_aligned_error_v6.png","plddt_mean":83.69},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KCNJ6","jax_strain_url":"https://www.jax.org/strain/search?query=KCNJ6"},"sequence":{"accession":"P48051","fasta_url":"https://rest.uniprot.org/uniprotkb/P48051.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P48051/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P48051"}},"corpus_meta":[{"pmid":"21962516","id":"PMC_21962516","title":"Crystal 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Comparison of wild-type and constitutively active mutant structures showed that G proteins open only the G-loop gate in the absence of PIP2, but in the presence of PIP2 the G-loop and inner helix gates become coupled so both open simultaneously. An intracellular Na+ ion-binding site was also identified, providing a structural basis for Na+-dependent modulation of channel activity.\",\n      \"method\": \"X-ray crystallography of wild-type and constitutively active mutant GIRK2 in the absence and presence of PIP2\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures of multiple channel states with functional interpretation, single rigorous study with multiple orthogonal structural comparisons and mutagenesis-validated constitutively active mutant\",\n      \"pmids\": [\"21962516\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"3.5 Å crystal structure of mammalian GIRK2 in complex with βγ G-protein subunits revealed that four Gβγ subunits bind at interfaces between four K+ channel subunits via short-range atomic and long-range electrostatic interactions, inducing a pre-open state intermediate between closed and fully open conformations. This structure is compatible with membrane-delimited activation and burst kinetics, and shows how PIP2 and Na+ participate in multi-ligand regulation.\",\n      \"method\": \"X-ray crystallography of GIRK2–Gβγ complex at 3.5 Å resolution\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structure of signaling complex, replicated and consistent with prior structural work from same lab\",\n      \"pmids\": [\"23739333\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Purified mammalian GIRK2 reconstituted in planar lipid bilayers showed that Gβγ and PIP2 must both be present simultaneously to activate the channel. Gαi1(GTPγS) has no activating effect, while Gαi1(GDP) closes the channel by removing Gβγ. Na+ is not essential but modulates Gβγ/PIP2 effects over physiological concentrations. GIRK2 opens as a function of PIP2 mole fraction with Hill coefficient ~2.5.\",\n      \"method\": \"Reconstitution of purified GIRK2 in planar lipid membranes; patch-clamp electrophysiology with defined purified protein components\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with purified components, multiple orthogonal conditions tested, mechanistically comprehensive\",\n      \"pmids\": [\"25049222\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Using membrane-anchored G protein concentration assays, four Gβγ subunits were shown to bind cooperatively to open GIRK2 (neuronal homomeric channel). Intracellular Na+, which enters neurons during action potentials, amplifies channel opening primarily by increasing Gβγ binding affinity, establishing a dual-input activation mechanism that provides activity-dependent feedback inhibition.\",\n      \"method\": \"Functional assay of GIRK2 activity vs. membrane-anchored Gβγ concentration in cell-based system; electrophysiology in mouse dopamine neurons\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — quantitative functional reconstitution with defined Gβγ concentrations plus native neuron validation, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"27074662\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Cryo-EM structures of GIRK2 in the presence and absence of cholesterol analog CHS and PIP2 revealed that CHS binds in lipid-facing hydrophobic pockets of the transmembrane domain near the PIP2 binding site. CHS stabilizes PIP2 interaction with the channel and promotes engagement of the cytoplasmic domain onto the transmembrane region. Mutagenesis of one CHS-binding pocket eliminated cholesterol-dependent potentiation.\",\n      \"method\": \"Cryo-electron microscopy structures of GIRK2 ± CHS ± PIP2; mutagenesis of CHS-binding site with functional assay\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — cryo-EM structures combined with mutagenesis functional validation, single lab but two orthogonal methods\",\n      \"pmids\": [\"34433062\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"GIRK2 and GIRK1 co-immunoprecipitate from brain regions where both are expressed (cerebral cortex, hippocampus, cerebellum), demonstrating that they form heteromeric channels in vivo. In weaver mouse brain, GIRK2 expression is dramatically decreased and GIRK1 expression is also disrupted in regions of co-assembly.\",\n      \"method\": \"Co-immunoprecipitation from rat and mouse brain tissue; immunohistochemistry\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP from native tissue, replicated across brain regions, consistent with expression data\",\n      \"pmids\": [\"8929423\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"The weaver mutation (G156S in the H5/pore region of GIRK2) causes constitutive activation, loss of K+ selectivity (increased Na+ permeability), and increased sensitivity to channel blockers when expressed in Xenopus oocytes. Pharmacological blockade of Na+ influx in weaver granule cells rescues their ability to differentiate, establishing that Na+ flux through mutant GIRK2 underlies granule cell development failure.\",\n      \"method\": \"Xenopus oocyte expression of weaver GIRK2; electrophysiology; pharmacological rescue of weaver cerebellar granule cells in culture\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — heterologous expression electrophysiology combined with pharmacological rescue in primary neurons, replicated across multiple labs\",\n      \"pmids\": [\"8630252\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"The weaver G156S mutation in the pore region of GIRK2 causes loss of high K+ selectivity over Na+, resulting in increased basal Na+ permeability and membrane depolarization in Xenopus oocytes. This loss of selectivity persists when weaver GIRK2 is coexpressed with GIRK1.\",\n      \"method\": \"Xenopus oocyte expression; electrophysiology/ion substitution experiments\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct electrophysiological characterization in heterologous system, replicated by multiple independent labs\",\n      \"pmids\": [\"8706831\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"GIRK2 knockout mice lack GABAB receptor-activated inwardly rectifying K+ currents in cerebellar granule cells, and GIRK1 expression is reduced in regions normally co-expressing both subunits. This establishes that GABAB receptors couple to heteromultimers of GIRK1 and GIRK2, and that GIRK2 is required for maintaining GIRK1 protein levels in these complexes.\",\n      \"method\": \"Electrophysiology of cerebellar granule cells from Girk2 null and weaver mice; Western blot for GIRK1 expression\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean knockout electrophysiology with defined phenotype replicated in two mutant mouse models, consistent with co-IP data from another lab\",\n      \"pmids\": [\"9342388\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"In the substantia nigra, GIRK channels are composed only of Kir3.2 (GIRK2) subunits (homotetramers of Kir3.2a and Kir3.2c splice variants), without significant Kir3.1 or Kir3.3 content, and are localized specifically at postsynaptic membranes on dopaminergic neuron dendrites. Kir3.2c, but not Kir3.2a, binds PDZ domain-containing protein PSD-95. Kir3.2a alone or Kir3.2a+Kir3.2c were activated by G-protein stimulation, but Kir3.2c alone was not.\",\n      \"method\": \"Immunoprecipitation, Western blot, immunohistochemistry, heterologous expression electrophysiology in Xenopus oocytes\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal biochemical and electrophysiological methods, single lab\",\n      \"pmids\": [\"9920664\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"GIRK2 and GIRK3 co-assemble to form functional heteromultimeric K+ channels in brain. Co-expressed GIRK2/GIRK3 channels showed ~5-fold lower sensitivity to activation by Gβγ compared to GIRK1/GIRKx channels. Complexes containing only GIRK2 and GIRK3 were immunoprecipitated from transfected cells and purified from native brain tissue.\",\n      \"method\": \"Co-transfection in CHO-K1 cells; patch-clamp electrophysiology; co-immunoprecipitation from transfected cells and native brain\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP from both heterologous and native tissue plus functional electrophysiology, single lab\",\n      \"pmids\": [\"10956667\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Gβγ binds to both the N-terminus and a segment of the C-terminus (~residues 320–409 by GIRK1 count, corresponding residues in GIRK2) of GIRK2. The Gβγ-binding sites in GIRK1 and GIRK2 C-termini are not identical; GIRK1 has an additional binding segment in the first half of its C-terminus that GIRK2 lacks. Key leucine residues (L273, L344 in GIRK2) are important for Gβγ-induced gating changes rather than Gβγ binding per se.\",\n      \"method\": \"Pull-down binding assays with GIRK subunit fragments; competition assays with Gαi1; mutagenesis with functional electrophysiology in Xenopus oocytes\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — direct binding assays combined with mutagenesis and functional electrophysiology, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"12743112\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"The GDP-bound form of Gαi3 (inactive state) regulates GIRK1-containing heteromeric channels by forming heterotrimers and reducing basal activity while increasing Gβγ-evoked current. This Gαi3-GDP regulation is unique to GIRK1 subunit-containing channels; homomeric GIRK2 channels are insensitive to Gαi3GDP. In vitro binding showed Gβγ enhances binding of Gαi3GDP to the cytosolic domain of GIRK1 but not GIRK2. The distal C-terminus of GIRK1 confers this differential regulation.\",\n      \"method\": \"Electrophysiology in Xenopus oocytes with coexpression of constitutively inactive/active Gα mutants; in vitro pull-down protein interaction assays; chimeric GIRK1/GIRK2 constructs\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro binding + heterologous electrophysiology + chimeric constructs, multiple orthogonal methods in single lab\",\n      \"pmids\": [\"19470775\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"GIRK2 knockout mice develop spontaneous seizures and are more susceptible to pharmacologically induced seizures (GABA antagonist), demonstrating that GIRK2 is required for normal neuronal excitability. GIRK2-null mice have normal cerebellar morphology but dramatically reduced GIRK1 expression in brain, unlike weaver mice. Weaver heterozygotes show milder cerebellar abnormalities than homozygotes, establishing a dosage-dependent gain-of-function mechanism for the weaver mutation.\",\n      \"method\": \"Gene knockout (homologous recombination), behavioral seizure testing, pharmacological seizure induction, immunohistochemistry\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined electrophysiological/behavioral phenotype, multiple orthogonal methods, widely replicated\",\n      \"pmids\": [\"9023358\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"GIRK2 knockout mice showed largely eliminated clonidine antinociception and significantly reduced morphine antinociception, establishing that postsynaptic GIRK2-mediated signaling is the primary effector for α2-adrenergic receptor analgesia and a major contributor to opioid analgesia. GIRK2 deletion eliminated sex differences in pain threshold, with greater impact in male mice.\",\n      \"method\": \"GIRK2 knockout mice; spinal reflex nociceptive testing (tail-flick); intrathecal drug administration\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with well-defined pharmacological phenotype, replicated across multiple analgesic drugs\",\n      \"pmids\": [\"12496346\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"GIRK2 knockout reduces or eliminates antinociceptive effects of ethanol, oxotremorine, nicotine, baclofen, clonidine, and cannabinoid agonist WIN 55,212 (but not ketamine), establishing that opioid, α-adrenergic, muscarinic cholinergic, GABAB, and cannabinoid receptors are coupled to postsynaptic GIRK2 channels in vivo. GIRK2 also mediates the opioid-dependent component of stress-induced analgesia.\",\n      \"method\": \"GIRK2 knockout mice; hot plate analgesia test; stress-induced analgesia paradigm\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with multiple drugs tested via consistent phenotypic readout, broad pharmacological validation\",\n      \"pmids\": [\"12493843\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"In locus coeruleus neurons, acute opioid-induced hyperpolarization is mediated primarily by G-protein-gated K+ channels containing Kir3.2 (GIRK2) and Kir3.3 subunits. [Met5]enkephalin-induced hyperpolarization was reduced by 40% in Kir3.2 KO neurons and by 80% in Kir3.2/Kir3.3 double KO neurons, with residual current nearly eliminated by K+ channel blockers Ba2+/Cs2+. This established that the cAMP-dependent cation conductance does not contribute significantly to acute opioid inhibition of LC neurons.\",\n      \"method\": \"Brain slice electrophysiology from Kir3.2 KO, Kir3.3 KO, and Kir3.2/3.3 double KO mice\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO electrophysiology with pharmacological dissection, genetically validated subunit contributions\",\n      \"pmids\": [\"12040038\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Spinal GIRK channels composed primarily of GIRK1/GIRK2 complexes modulate thermal nociception and mediate a significant component of intrathecal high-dose morphine analgesia. GIRK1 or GIRK2 knockout each reduces expression of the other subunit in spinal cord, confirming physical interaction between subunits. The GIRK channel blocker tertiapin reproduced the knockout phenotype in wild-type mice.\",\n      \"method\": \"GIRK1 and GIRK2 knockout mice; tail-flick thermal nociception test; intrathecal drug delivery; Western blot; tertiapin pharmacology\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — parallel KO lines + pharmacological validation + biochemical subunit interaction evidence, multiple orthogonal methods\",\n      \"pmids\": [\"15028774\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"In hippocampal pyramidal cells, Kir3.2-containing channels are enriched around glutamatergic synapses on dendritic spines and co-cluster with GABAB1 receptors at these sites, while on dendritic shafts Kir3.2 and GABAB1 are largely segregated. This compartment-dependent colocalization suggests that spine Kir3.2 channels preferentially mediate GABA effects while shaft channels are activated by other neurotransmitters.\",\n      \"method\": \"High-resolution immunocytochemistry; quantitative immunogold analysis; SDS-digested freeze-fracture replica immunolabeling (SDS-FRL)\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — high-resolution quantitative subcellular localization with SDS-FRL, co-clustering analysis with receptor, single lab but rigorous methodology\",\n      \"pmids\": [\"16624949\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"GIRK2 splice variant Kir3.2c binds the PDZ domain-containing scaffolding protein PSD-95 (demonstrated by co-immunoprecipitation), while Kir3.2a does not, providing a mechanism for selective postsynaptic localization of Kir3.2c-containing channels to dendritic membranes. Kir3.2c is specifically localized to acrosomal vesicles in testicular spermatids.\",\n      \"method\": \"Co-immunoprecipitation; immunohistochemistry; heterologous expression in Xenopus oocytes and HEK293T cells\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP demonstrating PDZ interaction with localization data, single lab with multiple methods\",\n      \"pmids\": [\"9920664\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Conformational rearrangements at the Gβγ-Kir3.1 (GIRK1) subunit interface upon δ-opioid receptor activation were detected by BRET, with DORs, Gβγ, and Kir3 subunits forming a constitutive complex. Conformational changes at the Gβγ/Kir3 interface were predictive of ligand ability to evoke channel currents, and were lost when Kir3.1 was replaced by a mutant lacking Gβγ-activation sites. GαoA did not directly associate with the channel despite being part of the complex.\",\n      \"method\": \"Bioluminescence resonance energy transfer (BRET) in HEK293 cells; co-immunoprecipitation; pertussis toxin treatment; mutagenesis\",\n      \"journal\": \"Molecular pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — BRET and co-IP with mutagenesis, single lab, Kir3.2-containing heteromeric channel studied as Kir3.1/Kir3.2 complex\",\n      \"pmids\": [\"23175530\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"RGS4 (a GTPase-activating protein) reduces basal GIRK1/GIRK2 current, accelerates channel deactivation kinetics, and abolishes the post-agonist reduction of basal conductance seen without RGS4 when co-expressed with kappa-opioid receptor in Xenopus oocytes. This establishes that RGS4 gates the duration and extent of GIRK1/GIRK2 channel activation by controlling G-protein GTPase activity.\",\n      \"method\": \"Co-expression in Xenopus oocytes; two-electrode voltage-clamp electrophysiology\",\n      \"journal\": \"Life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — electrophysiology in heterologous system, single lab, single method\",\n      \"pmids\": [\"11065178\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Kappa-opioid receptor couples to GIRK1/GIRK2 heteromeric channels. At nanomolar concentrations, U50488H activates GIRK1/GIRK2 via receptor-mediated pathway; at micromolar concentrations, U50488H, propoxyphene, methadone, and naloxone block GIRK1/GIRK2 by direct voltage-independent channel block (IC50 70 µM for U50488H). Morphine did not block at concentrations up to 1 mM. The related IRK1 channel was not affected.\",\n      \"method\": \"Xenopus oocyte expression; two-electrode voltage-clamp electrophysiology; ion substitution\",\n      \"journal\": \"European journal of pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Weak — in vitro functional assay with dose-response, single lab\",\n      \"pmids\": [\"10607882\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"GIRK1 rescues the weaver GIRK2 (G156S) phenotype by restoring K+ selectivity and G-protein dependence in a subunit-position-dependent manner. When two GIRK2wv subunits are arranged adjacently in a tetramer, currents remain weaver-like; alternating GIRK1-GIRK2wv tetramers restore wild-type K+-selective currents. This provides a structural basis for selective neuronal vulnerability in weaver mice.\",\n      \"method\": \"Xenopus oocyte expression of tandem dimers and linked tetramers; two-electrode voltage-clamp electrophysiology\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with engineered subunit arrangements, single lab but mechanistically informative\",\n      \"pmids\": [\"10493734\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"De novo heterozygous mutations in KCNJ6 (GIRK2) cause Keppen-Lubinsky syndrome. An in-frame deletion (p.Thr152del) and a missense mutation (p.Gly154Ser) in the pore region were identified in three unrelated affected individuals, establishing this condition as a channelopathy caused by severely impaired KCNJ6 channel function.\",\n      \"method\": \"Whole-exome sequencing of three unrelated KPLBS patients; genotype-phenotype correlation with animal model data\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — exome sequencing identifying de novo mutations at functionally critical pore residues, consistent with functional characterization in animal models, no direct functional assay in this paper\",\n      \"pmids\": [\"25620207\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"A de novo heterozygous KCNJ6 mutation p.Leu171Arg causes a gain-of-function: heterologous expression of mutant GIRK2 produces an aberrant basal inward current that is G-protein-independent, loses K+ selectivity, gains Ca2+ permeability, and is inhibited by the Na+ channel blocker QX-314 (similar to weaver). Expression of GIRK1-GIRK2(L171R) tandem dimer produces no current, suggesting non-functional heterotetramers.\",\n      \"method\": \"Whole-exome sequencing; heterologous expression in Xenopus oocytes or HEK cells; patch-clamp electrophysiology; pharmacological characterization\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro functional characterization with defined pharmacological and biophysical properties, multiple mutant constructs tested\",\n      \"pmids\": [\"29852244\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"GIRK2 channels are necessary and sufficient for peripheral opioid analgesia. GIRK channels are absent from mouse peripheral sensory neurons but present in human and rat. Transgenic expression of GIRK channels in mouse nociceptors established peripheral opioid signaling and local analgesia. A regulatory element in the rat GIRK2 gene accounts for differential expression in rodent sensory neurons.\",\n      \"method\": \"Transgenic mouse expression of GIRK in nociceptors; in vivo pain behavioral assays; immunohistochemistry in human/rat/mouse sensory neurons; regulatory element analysis\",\n      \"journal\": \"EMBO molecular medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain-of-function transgenic with defined behavioral rescue, species comparison with molecular mechanism for differential expression\",\n      \"pmids\": [\"23818182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Molecular dynamics simulations using the GIRK2 crystal structure revealed that Na+ ions control the cytosolic (G-loop) gate through an anti-clockwise rotation of the cytoplasmic domain, while Gβγ stabilizes the transmembrane inner helix gate in the open state through a rocking movement of the cytoplasmic domain. Both effects alter channel interaction with PIP2 to stabilize respective open states.\",\n      \"method\": \"All-atom microsecond-scale molecular dynamics simulations based on GIRK2 crystal structures\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — computational modeling only with no direct mutagenesis validation in this paper; consistent with crystal structure data\",\n      \"pmids\": [\"31659119\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Native mass spectrometry and fluorescent lipid binding assays showed PIP2 (PIP(4,5)P2) cooperatively binds GIRK2 with Hill coefficient of 2.7. Single mutations at specific Kir3.2 residues distinctly alter PIP isoform selectivity: K64Q alters binding profiles favoring specific PIP(4,5)P2 acyl chains, R92P (equivalent to Kir6.2 residue) causes promiscuous binding, and K194A creates preference for PIP(3,4,5)P3.\",\n      \"method\": \"Native mass spectrometry; fluorescent lipid binding assays; site-directed mutagenesis\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — direct biophysical binding measurements with mutagenesis, two orthogonal methods, single lab\",\n      \"pmids\": [\"32372643\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"A novel GIRK2 splice variant (GIRK2B) has a shorter C-terminus differing in only the last 8 amino acids from GIRK2A. When co-injected with GIRK1 and m2-receptor in Xenopus oocytes, GIRK2B dramatically enhances acetylcholine-induced inwardly rectifying K+ current, demonstrating it forms functional heteromultimeric G-protein-gated K+ channels with GIRK1.\",\n      \"method\": \"cDNA library cloning; RT-PCR tissue distribution; Xenopus oocyte co-expression electrophysiology\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — functional heterologous expression showing channel activity, single lab\",\n      \"pmids\": [\"8573147\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"GIRK2 isoforms GIRK2a and GIRK2c support comparable somato-dendritic GIRK currents in hippocampal pyramidal neurons, but GIRK2c achieves more uniform subcellular distribution and better supports inhibitory postsynaptic currents in distal dendrites. GIRK2a over-expression additionally enhanced cue fear learning, while both isoforms restored contextual fear learning in Girk2-null pyramidal neurons.\",\n      \"method\": \"Viral-mediated expression of individual GIRK2 isoforms in Girk2-/- hippocampal neurons; patch-clamp electrophysiology; immunofluorescence; fear conditioning behavioral assays\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (electrophysiology, imaging, behavior) with isoform-specific comparisons, single lab\",\n      \"pmids\": [\"28487514\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Transgenic mice overexpressing human KCNJ6 (Kir3.2/GIRK2) show increased Kir3.2 protein in atria (2.5-fold) and enhanced chronotropic responses to muscarinic (carbachol, methoxamine) and adenosinergic (CCPA) stimulation, demonstrating that KCNJ6 overexpression alters cardiac rate control specifically at sino-atrial node and atria.\",\n      \"method\": \"Transgenic mouse model with human KCNJ6; ECG recording under urethane anesthesia; pharmacological challenge\",\n      \"journal\": \"Physiological genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — transgenic gain-of-function with defined cardiac phenotype and pharmacological dissection, single lab\",\n      \"pmids\": [\"18303085\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Increased Kcnj6 gene dose is necessary for synaptic and cognitive dysfunction in the Ts65Dn mouse model of Down syndrome. Reduction of Kcnj6 from 3 to 2 copies in Ts65Dn mice restored hippocampal Kir3.2 protein to normal levels, improved long-term memory, and rescued short-term and long-term potentiation in the dentate gyrus. Fluoxetine, which suppresses Kir3.2 channels, also rescued synaptic plasticity.\",\n      \"method\": \"Genetic reduction of Kcnj6 copy number in Ts65Dn mice; novel object recognition test; hippocampal slice electrophysiology (STP, LTP); fluoxetine pharmacology\",\n      \"journal\": \"Neurobiology of disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis (copy number normalization) with defined synaptic and behavioral rescue plus pharmacological validation, single lab\",\n      \"pmids\": [\"28342823\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Deletion of GIRK2 subunit increases basal firing rate of dorsal raphe neurons and causes desensitization of 5-HT1A receptors, demonstrated by lower sensitivity of dorsal raphe neurons to inhibitory effects of 5-HT1A agonist 8-OH-DPAT and citalopram. GIRK2 knockout mice show a depression-resistant behavioral phenotype.\",\n      \"method\": \"In vivo extracellular recordings from dorsal raphe neurons in GIRK2 KO mice; GIRK channel blocker tertiapin-Q; behavioral depression tests\",\n      \"journal\": \"The international journal of neuropsychopharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO electrophysiology with pharmacological validation using channel blocker, functional link established\",\n      \"pmids\": [\"25956878\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"GIRK2 expressed in NPY/AgRP neurons stabilizes their excitability; conditional deletion of GIRK2 from AgRP neurons increases their persistent excitability, leading to decreased sympathetic activity and energy expenditure (not food intake), resulting in increased body weight and adiposity. Compromised cold adaptation was also observed.\",\n      \"method\": \"AgRP neuron-selective GIRK2 conditional knockout mice; electrophysiology; metabolic phenotyping; sympathetic activity measurement\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-type-specific conditional KO with defined metabolic and electrophysiological phenotype, multiple orthogonal measurements\",\n      \"pmids\": [\"37594983\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"A novel GIRK2 activator (N5) identified from tethered protein scaffold library selection increases Kir3.2 basal activity by inhibiting clearance of the channel from the cell surface (reducing internalization), rather than affecting core biophysical channel properties.\",\n      \"method\": \"Tethered protein display selection in yeast; functional assay; cell surface expression quantification\",\n      \"journal\": \"ACS chemical neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — functional selection with cell surface trafficking assay, single lab, novel mechanism but limited mechanistic depth in abstract\",\n      \"pmids\": [\"25028803\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"KCNJ6 noncoding variants in AUD subjects reduce GIRK2 expression in iPSC-derived glutamatergic neurons, causing increased neurite area and elevated neuronal excitability. Ethanol at intoxicating concentrations induces GIRK2 expression and reverses these functional effects. Ectopic overexpression of GIRK2 alone mimics the ethanol effect to normalize excitability, establishing GIRK2 as the molecular effector linking KCNJ6 variants to altered neuronal excitability and ethanol response.\",\n      \"method\": \"iPSC-derived neurons from AUD patients; single-cell RNA sequencing; patch-clamp electrophysiology; morphological analysis; GIRK2 overexpression\",\n      \"journal\": \"Molecular psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — patient-derived neurons with multiple orthogonal readouts and rescue experiment, single lab\",\n      \"pmids\": [\"36207584\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KCNJ6/GIRK2 encodes an inwardly rectifying K+ channel subunit that forms homo- or heterotetramers (with GIRK1, GIRK3) and is activated by a dual obligatory requirement for both Gβγ (binding cooperatively at subunit interfaces) and PIP2 (binding at the transmembrane-cytoplasmic domain interface), with intracellular Na+ serving as an amplifier of Gβγ affinity; crystal and cryo-EM structures have defined two sequential gates (a cytoplasmic G-loop gate controlled by Na+ and a transmembrane inner helix gate stabilized by Gβγ), cholesterol binding near PIP2 stabilizes channel opening, and the channel serves as the principal postsynaptic effector coupling inhibitory GPCRs (GABAB, μ/δ/κ opioid, α2-adrenergic, muscarinic, cannabinoid, serotonin 5-HT1A, adenosine A1) to neuronal hyperpolarization, with critical physiological roles in nociception, analgesia, cardiac rate control, neuronal excitability, and energy homeostasis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"KCNJ6 encodes GIRK2 (Kir3.2), the principal neuronal subunit of G-protein-gated inwardly rectifying K+ channels that couple inhibitory GPCRs to membrane hyperpolarization and thereby set neuronal excitability across multiple circuits [#8, #16]. GIRK2 assembles into functional tetramers as homomers in dopaminergic substantia nigra neurons and as heteromers with GIRK1 or GIRK3 in cortex, hippocampus, and cerebellum, where loss of GIRK2 destabilizes the partner subunit [#5, #8, #9, #10]. Channel opening requires the simultaneous, obligatory presence of both Gβγ and PIP2: reconstitution of purified GIRK2 in lipid bilayers showed neither ligand alone activates the channel, and Gαi(GDP) closes it by sequestering Gβγ [#2]. Crystal and Gβγ-complex structures defined two sequential gates — a cytoplasmic G-loop gate and a transmembrane inner-helix gate — with four Gβγ subunits binding cooperatively at subunit interfaces to drive a pre-open state, and an intracellular Na+ site that amplifies Gβγ affinity to provide activity-dependent feedback inhibition [#0, #1, #3]. Cholesterol/CHS binds adjacent to the PIP2 site and stabilizes channel opening, while PIP2 itself binds cooperatively with isoform-selective residues controlling lipid specificity [#4, #28]. Through these inputs GIRK2 serves as the postsynaptic effector for GABAB, opioid, α2-adrenergic, muscarinic, cannabinoid, adenosine, and 5-HT1A receptors, mediating analgesia, neuronal excitability control, cardiac rate modulation, mood regulation, and energy homeostasis [#14, #15, #16, #31, #33, #34]. De novo pore-region mutations in KCNJ6 cause Keppen-Lubinsky syndrome, and a gain-of-function pore mutation produces an aberrant, non-selective basal current mirroring the classic weaver phenotype [#24, #25, #6].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Established that GIRK2 is a physiological channel subunit that physically assembles with GIRK1 in vivo and whose pore mutation underlies a neurodevelopmental disease, answering what GIRK2 partners with and how its dysfunction causes pathology.\",\n      \"evidence\": \"Reciprocal co-IP from rat/mouse brain and Xenopus oocyte electrophysiology of the weaver G156S pore mutant with pharmacological rescue of granule cells\",\n      \"pmids\": [\"8929423\", \"8630252\", \"8706831\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of native heteromers not resolved\", \"Mechanism by which GIRK2 stabilizes GIRK1 protein levels unknown\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Defined GIRK2 splice variants and showed GIRK2B forms functional G-protein-gated channels with GIRK1, addressing isoform diversity at the channel level.\",\n      \"evidence\": \"cDNA cloning and Xenopus oocyte co-expression with GIRK1 and m2 receptor\",\n      \"pmids\": [\"8573147\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo role of GIRK2B not established\", \"Single-lab functional characterization\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Demonstrated genetically that GIRK2 is the obligatory effector for GABAB receptor-activated K+ currents and is required for normal neuronal excitability, linking the channel to inhibitory neurotransmission and seizure susceptibility.\",\n      \"evidence\": \"Girk2 knockout mouse electrophysiology in cerebellar granule cells and behavioral seizure testing\",\n      \"pmids\": [\"9342388\", \"9023358\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not dissect contributions of individual heteromeric partners\", \"Circuit-level basis of seizures not mapped\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Resolved the molecular subunit composition and postsynaptic targeting of native GIRK2 channels, showing homomeric Kir3.2 in substantia nigra and PSD-95 binding by the Kir3.2c splice variant for dendritic localization.\",\n      \"evidence\": \"IP/Western, immunohistochemistry, and heterologous electrophysiology of Kir3.2a/c splice variants; co-IP with PSD-95\",\n      \"pmids\": [\"9920664\", \"9920664\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab co-IP for PSD-95 interaction\", \"Functional consequence of acrosomal localization unexplored\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Used engineered subunit arrangements to explain selective neuronal vulnerability, showing GIRK1 rescues the weaver pore defect in a position-dependent manner.\",\n      \"evidence\": \"Xenopus oocyte expression of tandem dimers and linked tetramers\",\n      \"pmids\": [\"10493734\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Native subunit arrangement not directly observed\", \"Single-lab reconstitution\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Showed GIRK2/GIRK3 heteromers form in brain and that RGS proteins gate the kinetics and duration of GIRK1/GIRK2 activation, extending the channel's regulatory and partner repertoire.\",\n      \"evidence\": \"Co-IP from transfected cells and native brain plus CHO patch-clamp; Xenopus oocyte voltage-clamp with RGS4 and kappa-opioid receptor\",\n      \"pmids\": [\"10956667\", \"11065178\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"RGS4 evidence from single heterologous study\", \"Physiological role of GIRK2/GIRK3 heteromers in vivo unclear\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Established GIRK2 as the dominant postsynaptic effector mediating analgesia from multiple GPCRs and acute opioid hyperpolarization, defining its in vivo pharmacological coupling.\",\n      \"evidence\": \"Girk2 (and Kir3.3) knockout mice in nociceptive behavioral assays and locus coeruleus slice electrophysiology with multiple agonists\",\n      \"pmids\": [\"12496346\", \"12493843\", \"12040038\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contribution of each receptor to specific circuits not fully resolved\", \"Sex-difference mechanism not defined\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Mapped the Gβγ-binding determinants in GIRK2 N- and C-termini and distinguished binding from gating residues, clarifying the molecular basis of G-protein activation.\",\n      \"evidence\": \"Pull-down binding assays with subunit fragments, Gαi1 competition, and mutagenesis with Xenopus oocyte electrophysiology\",\n      \"pmids\": [\"12743112\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of binding-vs-gating distinction not resolved in this work\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Demonstrated spinal GIRK1/GIRK2 channels mediate thermal nociception and high-dose morphine analgesia, with reciprocal subunit dependence confirming physical interaction.\",\n      \"evidence\": \"GIRK1 and GIRK2 knockout mice in tail-flick assays with intrathecal drug delivery, Western blot, and tertiapin pharmacology\",\n      \"pmids\": [\"15028774\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cellular site of spinal GIRK action not pinpointed\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Revealed compartment-specific subcellular targeting, with spine Kir3.2 co-clustering with GABAB receptors while shaft channels segregate, suggesting input-specific signaling.\",\n      \"evidence\": \"Quantitative immunogold and SDS-FRL in hippocampal pyramidal cells\",\n      \"pmids\": [\"16624949\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of compartmentalization not directly tested electrophysiologically\", \"Single-lab analysis\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Showed KCNJ6 overexpression alters cardiac rate control at the sino-atrial node, extending GIRK2 function beyond the CNS.\",\n      \"evidence\": \"Transgenic human-KCNJ6 mice with ECG and muscarinic/adenosinergic pharmacological challenge\",\n      \"pmids\": [\"18303085\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Endogenous cardiac GIRK2 contribution not assessed by loss-of-function\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identified GIRK1-specific regulation by Gαi3-GDP, distinguishing heteromer-specific tuning from GIRK2-intrinsic gating.\",\n      \"evidence\": \"Xenopus oocyte electrophysiology with Gα mutants, in vitro pull-down, and GIRK1/GIRK2 chimeras\",\n      \"pmids\": [\"19470775\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not address GIRK2-homomer regulation, which is insensitive\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Provided the first structural framework for gating, defining two gates and a Na+ site and showing PIP2 couples the G-loop and inner-helix gates.\",\n      \"evidence\": \"X-ray crystallography of wild-type and constitutively active GIRK2 with and without PIP2\",\n      \"pmids\": [\"21962516\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Gβγ engagement not yet visualized structurally at this stage\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Captured dynamic conformational rearrangements at the Gβγ/Kir3 interface upon receptor activation in a pre-formed signaling complex, linking ligand efficacy to channel gating.\",\n      \"evidence\": \"BRET, co-IP, pertussis toxin, and mutagenesis in HEK293 cells (Kir3.1/Kir3.2 heteromer)\",\n      \"pmids\": [\"23175530\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Performed on GIRK1-containing heteromers\", \"Single-lab live-cell biosensor data\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Solved the GIRK2–Gβγ complex structure, showing four Gβγ binding cooperatively at subunit interfaces to induce a pre-open intermediate, and established GIRK2 sufficiency for peripheral opioid analgesia.\",\n      \"evidence\": \"3.5 Å crystallography of the GIRK2–Gβγ complex; transgenic GIRK expression in mouse nociceptors with behavioral assays and cross-species immunohistochemistry\",\n      \"pmids\": [\"23739333\", \"23818182\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full open-state transition from pre-open not captured\", \"Determinants of species-specific sensory expression only partially mapped\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Reconstituted the obligatory dual Gβγ+PIP2 activation requirement with purified components and identified a trafficking-based pharmacological activation mechanism.\",\n      \"evidence\": \"Planar lipid bilayer reconstitution of purified GIRK2 with patch-clamp; tethered protein scaffold selection of activator N5\",\n      \"pmids\": [\"25049222\", \"25028803\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"N5 mechanism described only at the level of internalization\", \"Cooperativity origin (Hill ~2.5) not structurally explained\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Established KCNJ6 as a Mendelian disease gene, linking pore-region de novo mutations to Keppen-Lubinsky syndrome.\",\n      \"evidence\": \"Whole-exome sequencing of three unrelated patients with genotype-phenotype correlation to animal models\",\n      \"pmids\": [\"25620207\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct functional assay of patient mutations in this study\", \"Loss- vs gain-of-function consequence not biophysically tested here\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Quantified the cooperative dual-input mechanism, showing Na+ amplifies channel opening by increasing Gβγ affinity to provide activity-dependent feedback, and linked GIRK2 to serotonergic autoinhibition.\",\n      \"evidence\": \"Membrane-anchored Gβγ concentration assays with dopamine-neuron electrophysiology; dorsal raphe in vivo recordings in Girk2 KO with tertiapin-Q and behavior\",\n      \"pmids\": [\"27074662\", \"25956878\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Native concentrations of Gβγ/Na+ during physiological firing not directly measured\", \"Antidepressant-resistance mechanism only correlative\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defined isoform-specific subcellular distribution and behavioral roles, and demonstrated Kcnj6 gene dosage drives Down-syndrome synaptic and cognitive dysfunction.\",\n      \"evidence\": \"Viral isoform expression in Girk2-null hippocampal neurons with electrophysiology and fear conditioning; genetic copy-number reduction in Ts65Dn mice with LTP and memory assays plus fluoxetine pharmacology\",\n      \"pmids\": [\"28487514\", \"28342823\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of isoform distribution differences incompletely defined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Showed a de novo pore mutation produces a weaver-like gain-of-function with loss of K+ selectivity and gained Ca2+ permeability, defining a pathogenic mechanism distinct from simple loss of function.\",\n      \"evidence\": \"Whole-exome sequencing and heterologous expression of the L171R mutant with patch-clamp and QX-314 pharmacology\",\n      \"pmids\": [\"29852244\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo phenotype of L171R not modeled\", \"Heterotetramer non-functionality inferred from tandem dimer only\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Resolved PIP2 cooperativity and isoform selectivity at the residue level, refining how lipid identity tunes GIRK2 activation.\",\n      \"evidence\": \"Native mass spectrometry and fluorescent lipid binding assays with site-directed mutagenesis\",\n      \"pmids\": [\"32372643\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological relevance of altered PIP isoform selectivity not tested in cells\", \"Single-lab biophysical data\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified cholesterol as a structural modulator binding near PIP2 to stabilize the open state, integrating lipid environment into the gating model.\",\n      \"evidence\": \"Cryo-EM of GIRK2 ± CHS ± PIP2 with mutagenesis of the CHS pocket and functional validation\",\n      \"pmids\": [\"34433062\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Native cholesterol regulation in neurons not directly demonstrated\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined a cell-type-specific role in energy homeostasis, showing GIRK2 stabilizes AgRP neuron excitability to control sympathetic tone and energy expenditure.\",\n      \"evidence\": \"AgRP-selective conditional Girk2 knockout with electrophysiology, metabolic phenotyping, and sympathetic activity measurement\",\n      \"pmids\": [\"37594983\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Upstream GPCR driving AgRP GIRK2 signaling not identified\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Linked KCNJ6 regulatory variants to alcohol-use phenotypes via GIRK2 expression-dependent control of human neuronal excitability.\",\n      \"evidence\": \"iPSC-derived glutamatergic neurons from AUD patients with single-cell RNA-seq, patch-clamp, morphology, and GIRK2 overexpression rescue\",\n      \"pmids\": [\"36207584\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal noncoding variant mechanism not fully defined\", \"In vivo relevance to AUD not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the sequential gates, multi-ligand cooperativity, and isoform/partner-specific tuning are integrated dynamically in native circuits to produce precise context-dependent inhibition remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No native-membrane structure of a fully open GPCR–Gβγ–GIRK2 signaling complex\", \"Quantitative in vivo dynamics of Na+/Gβγ/PIP2 co-regulation during firing unmeasured\", \"Direct functional assays of most disease mutations lacking\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [2, 6, 7, 8, 16]},\n      {\"term_id\": \"GO:0005267\", \"supporting_discovery_ids\": [2, 8, 16]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [2, 4, 28]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [8, 16, 33]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 1, 5, 10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [2, 9, 18, 35]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [19]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 3, 11, 16]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [8, 13, 16, 18]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [34]}\n    ],\n    \"complexes\": [\n      \"GIRK1/GIRK2 heterotetramer\",\n      \"GIRK2 homotetramer\",\n      \"GIRK2/GIRK3 heterotetramer\",\n      \"GPCR-Gβγ-GIRK2 signaling complex\"\n    ],\n    \"partners\": [\n      \"KCNJ3\",\n      \"KCNJ9\",\n      \"GNB1\",\n      \"GNG2\",\n      \"GNAI3\",\n      \"DLG4\",\n      \"RGS4\",\n      \"GABBR1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}