{"gene":"P2RX2","run_date":"2026-04-29T11:37:57","timeline":{"discoveries":[{"year":1995,"finding":"P2X2 and P2X3 subunits heteropolymerize to form a novel ATP-gated ion channel in sensory neurons; coexpression of P2X2 and P2X3 (but not other combinations) in Xenopus oocytes reproduced the ATP-gated currents of dorsal root ganglion neurons, indicating heteromeric channel formation.","method":"Xenopus oocyte coexpression, voltage-clamp electrophysiology","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 — reconstitution in heterologous system, foundational paper with 867 citations, replicated by multiple subsequent studies","pmids":["7566120"],"is_preprint":false},{"year":1997,"finding":"P2X2 and P2X3 subunits physically associate to form heteromeric channels with distinct agonist sensitivity and desensitization properties; cross-immunoprecipitation with epitope-tagged subunits in baculovirus-infected insect cells provided direct biochemical evidence for heteromeric assembly.","method":"Baculovirus expression in insect cells, cross-immunoprecipitation, whole-cell electrophysiology","journal":"The Journal of Neuroscience","confidence":"High","confidence_rationale":"Tier 1 — direct biochemical reconstitution plus functional characterization in same study","pmids":["9254665"],"is_preprint":false},{"year":2005,"finding":"P2X2 receptors are trimers; chemical cross-linking produced higher-order adducts consistent with trimers, AFM imaging gave mean molecular volume of ~409 nm³ consistent with a trimer, and angle measurements between two bound anti-His antibodies on doubly-labeled receptors averaged 123°, indicating trimeric architecture.","method":"Chemical cross-linking, atomic force microscopy (AFM), anti-epitope antibody angle measurement","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 1 — multiple orthogonal structural methods in one study, consistent with crystal structure data from related P2X receptors","pmids":["15657042"],"is_preprint":false},{"year":2004,"finding":"Homomeric P2X2 receptors are trimers; biochemical cross-linking and co-expression studies confirmed trimeric architecture for slowly desensitizing P2X subtypes including P2X2, P2X4, and P2X5, while P2X6 subunits were retained in ER as non-trimeric aggregates.","method":"Chemical cross-linking, co-expression studies, Western blot","journal":"Journal of Molecular Biology","confidence":"High","confidence_rationale":"Tier 1 — biochemical reconstitution with multiple subunit combinations, consistent with AFM data","pmids":["15313628"],"is_preprint":false},{"year":2000,"finding":"A conserved protein kinase C phosphorylation site (TXK/R motif) in the intracellular N-terminus of P2X2, specifically Thr18, controls desensitization kinetics; mutations at Thr18 (T18A, T18N) or K20T converted slow desensitization (>1 min) to fast desensitization (<1 s), and direct phosphorylation of Thr18 by PKC was demonstrated by immunodetection. Interaction between both cytoplasmic domains is also required for slow desensitization.","method":"Site-directed mutagenesis, voltage-clamp in Xenopus oocytes, immunodetection of phosphothreonine","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis plus direct phosphorylation detection, multiple mutant characterizations","pmids":["10744703"],"is_preprint":false},{"year":1998,"finding":"PKA phosphorylation of Ser431 in the intracellular C-terminus of P2X2 reduces ATP-activated current amplitude; intracellular perfusion of 8-bromo-cAMP or PKA catalytic subunit reduced current in wild-type but not S431C mutant receptors expressed in HEK293 cells.","method":"Site-directed mutagenesis, whole-cell patch-clamp, intracellular dialysis of PKA/cAMP","journal":"Journal of Neurochemistry","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis combined with direct enzyme application identifies specific phosphorylation site","pmids":["9603227"],"is_preprint":false},{"year":1998,"finding":"N-linked glycosylation at three extracellular asparagine residues (N182, N239, N298) of P2X2 is essential for cell-surface expression; tunicamycin treatment or triple-site mutagenesis abolished ATP responses and drastically reduced surface expression as shown by biotin labeling and immunofluorescence.","method":"Site-directed mutagenesis, tunicamycin treatment, surface biotinylation, immunofluorescence, whole-cell recording","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 — two independent approaches (pharmacological and mutagenesis) converging on same mechanism","pmids":["9778359"],"is_preprint":false},{"year":1998,"finding":"Alternative splicing of P2X2 generates isoforms (P2X2a and P2X2b/P2X2-2) that differ in their C-terminal sequences; P2X2b lacks Val370-Gln438 and desensitizes rapidly and completely, whereas P2X2a desensitizes slowly and incompletely. Both isoforms have similar EC50 for ATP. Coexpression of both isoforms can reproduce intermediate desensitization rates seen in native somatotrophs.","method":"Heterologous expression in GT1/HEK293 cells, Ca2+ imaging, electrophysiology, RT-PCR in enriched pituitary subpopulations","journal":"Molecular Endocrinology","confidence":"High","confidence_rationale":"Tier 1 — functional reconstitution of native behavior from defined splice variants","pmids":["9658396"],"is_preprint":false},{"year":1999,"finding":"C-terminal residues near the splice site regulate desensitization rate: truncation at Lys369 accelerated desensitization >100-fold; a single Val370 residue slowed desensitization ~70-fold; the hydrophobicity of Val370 (not its exact structure) determines rate; nearby lysines (especially Lys365) also modulate desensitization.","method":"Site-directed mutagenesis, two-electrode voltage-clamp in Xenopus oocytes, peptide injection","journal":"The Journal of Physiology","confidence":"High","confidence_rationale":"Tier 1 — systematic mutagenesis with peptide rescue experiment, multiple independent mutations tested","pmids":["10517803"],"is_preprint":false},{"year":2006,"finding":"Phosphoinositides (PIP2, PIP3) regulate P2X2 channel desensitization and pore dilation through direct electrostatic interaction with positively charged residues (Lys365, Lys369) in the proximal cytoplasmic C-terminal domain; PI3K inhibition accelerated desensitization, and K365Q/K369Q mutations mimicked this effect and abolished lipid binding in GST pull-down assays.","method":"PI3K inhibition, site-directed mutagenesis, two-electrode voltage-clamp, GST pull-down with PIP-coated membranes, fluorescence assay in COS-7 cells","journal":"The Journal of Physiology","confidence":"High","confidence_rationale":"Tier 1 — direct lipid binding assay combined with mutagenesis and electrophysiology","pmids":["16857707"],"is_preprint":false},{"year":2005,"finding":"Zinc potentiates P2X2 channel opening via an intersubunit binding site formed by His120 and His213 from adjacent subunits; mixing H120A and H213A single mutants restored zinc potentiation, trimeric concatamers showed zinc potentiation correlating with intersubunit histidine pairs, and H120C/H213C formed ectopic intersubunit disulfide bonds detectable by non-reducing Western blot.","method":"Site-directed mutagenesis, trimeric concatamer expression, Xenopus oocyte electrophysiology, non-reducing Western blot, redox manipulation","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 1 — five independent lines of evidence including disulfide trapping and concatamer approach","pmids":["15899882"],"is_preprint":false},{"year":2004,"finding":"P2X2 channel pore properties (permeability to large cations, inward rectification, ligand sensitivity) depend on channel expression density; Ile328 at the outer pore mouth is critical for these density-dependent changes, as shown by mutagenesis.","method":"Variable expression levels in Xenopus oocytes, mutagenesis, two-electrode voltage-clamp","journal":"The Journal of Physiology","confidence":"Medium","confidence_rationale":"Tier 1 method but single lab, single study","pmids":["15107474"],"is_preprint":false},{"year":2004,"finding":"TM1 and TM2 of P2X2 participate in conformational changes during activation; alanine-scanning mutagenesis identified residues in TM1 (pattern consistent with helix) and TM2 that altered ATP potency, BzATP efficacy, and deactivation kinetics. Y43A and F44A in TM1 produced spontaneously active channels.","method":"Alanine-scanning mutagenesis, whole-cell patch-clamp in HEK293 cells","journal":"The Journal of Neuroscience","confidence":"High","confidence_rationale":"Tier 1 — systematic mutagenesis across both TM domains with multiple functional readouts","pmids":["15317863"],"is_preprint":false},{"year":2007,"finding":"Thr339 in TM2 is critical for gating; T339S mutation causes constitutive channel opening and 10-fold increase in ATP sensitivity. Lys308 is involved in gating (not just ATP binding): K308A suppresses spontaneous activity of T339S but K69A does not, indicating Lys308 has a gating role distinct from ATP coordination.","method":"Site-directed mutagenesis, single-channel and whole-cell recording in HEK293 cells","journal":"The Journal of Neuroscience","confidence":"High","confidence_rationale":"Tier 1 — constitutively active mutant plus epistatic double-mutant analysis","pmids":["18032665"],"is_preprint":false},{"year":2009,"finding":"Polar residues in TM2 define the channel gate and permeation pathway; Thr336, Thr339, and Ser340 are exposed in the open channel pore (introduction of positive charge greatly enhanced outward currents); Asn333 and Asp349 lie in external and internal vestibules respectively; gate is formed by residues Asn333-Thr339, with channel opening involving counter-clockwise rotation and separation of TM2 helices.","method":"Systematic TM2 mutagenesis, MTSET modification, single-channel recordings, Xenopus oocytes","journal":"The Journal of Neuroscience","confidence":"High","confidence_rationale":"Tier 1 — SCAM approach combined with crystal structure interpretation, systematic mutagenesis","pmids":["19906973"],"is_preprint":false},{"year":2004,"finding":"FRET measurements revealed time-resolved cytosolic gating motions in P2X2 channels that correlate with permeability changes; wild-type and mutant channels that do not undergo permeability changes also show no cytosolic FRET changes; tethering the cytosolic domain to the plasma membrane prevents both permeability change and cytosolic motions.","method":"FRET (CFP/YFP on cytosolic domain), simultaneous whole-cell electrophysiology, tethering experiments","journal":"The Journal of Neuroscience","confidence":"High","confidence_rationale":"Tier 1 — real-time structural measurements correlated with function, with rescue experiment","pmids":["15548662"],"is_preprint":false},{"year":2008,"finding":"P2X2 receptor permeability dynamics (I2 state) are an intrinsic channel property requiring cytosolic domain rearrangements; Pannexin-1 channels make no detectable contribution. Patch-clamp coordinated spectroscopy with tetracysteine/biarsenical fluorophores measured site-specific conformational changes in the cytosolic domain correlated with permeability increases.","method":"Patch-clamp coordinated spectroscopy, tetracysteine tagging, biarsenical fluorophores, Panx-1 knockout comparison","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 1 — novel spectroscopy method combined with genetic knockout control distinguishes two mechanistic models","pmids":["18689682"],"is_preprint":false},{"year":2011,"finding":"ATP-binding sites are located in intersubunit extracellular cavities; covalent tethering of ATP-analog NCS-ATP to single cysteine mutants at N140 and L186 (from two adjacent subunits, ~18 Å apart) trapped agonist-bound states with distinct functional consequences: labeling at one position impedes gating efficiency, labeling at the other enhances subsequent ATP function.","method":"Covalent tethering with thiol-reactive ATP analog, whole-cell and single-channel recording, P2X2 homology modeling","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 1 — chemical biology approach directly localizes binding site with functional validation","pmids":["21576497"],"is_preprint":false},{"year":2012,"finding":"Trimeric P2X2 receptors can be activated by fewer than three ATP molecules; concatamers with only two intact Lys69 binding sites (KKA, KAK, AKK) formed functional channels, with KKA and KAK producing larger currents than AKK, indicating asymmetric contributions from different subunit interfaces.","method":"Trimeric concatamers with defined ATP-binding site mutations, Western blot, whole-cell and outside-out patch recording in HEK293 cells","journal":"Molecular Pharmacology","confidence":"High","confidence_rationale":"Tier 1 — concatenated subunit approach directly tests stoichiometry of activation","pmids":["22828800"],"is_preprint":false},{"year":2012,"finding":"A salt bridge between Glu167 and Arg290 stabilizes the closed state; ATP binding disrupts this bridge, allowing Arg290 to coordinate the γ-phosphate of ATP. Charge-reversal mutagenesis, mutant cycle analysis, and disulfide trapping demonstrated the Glu167/Arg290 interaction in the closed state and its absence in the open state.","method":"Homology modeling, charge-reversal mutagenesis, mutant cycle analysis, disulfide trapping, electrophysiology","journal":"Molecular Pharmacology","confidence":"High","confidence_rationale":"Tier 1 — multiple orthogonal methods including thermodynamic cycle analysis and state-dependent disulfide trapping","pmids":["23041661"],"is_preprint":false},{"year":2006,"finding":"Ectodomain lysine residues in P2X2 (Lys69 and Lys308) contribute to ATP binding/gating in heteromeric P2X2/3 receptors; P2X2/3 heteromers contain one P2X2 and two P2X3 subunits, as single lysine mutations in P2X2 were rescued by wild-type P2X3 but not vice versa, and double P2X2 lysine mutant was not rescued.","method":"Lysine-to-alanine mutagenesis, co-expression in HEK293 cells, whole-cell voltage-clamp","journal":"Molecular Pharmacology","confidence":"High","confidence_rationale":"Tier 2 — mutational rescue approach defines stoichiometry, replicated finding consistent with PMID 22378790","pmids":["16840712"],"is_preprint":false},{"year":2012,"finding":"P2X2/3 heteromers contain one P2X2 and two P2X3 subunits, while P2X2/6 heteromers contain two P2X2 and one P2X6 subunit; demonstrated by selective blockade of function using ATP-binding site mutants in each subunit position, confirmed by protein labeling and PAGE.","method":"ATP-binding site mutagenesis (non-functional Ala substitutions), patch-clamp, Ca2+ imaging, surface protein labeling and PAGE in HEK293 cells and Xenopus oocytes","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 1 — functional and biochemical approaches both support same stoichiometry conclusion, consistent with PMID 16840712","pmids":["22378790"],"is_preprint":false},{"year":2000,"finding":"Coexpression of P2X2 and P2X6 subunits forms a heteromeric P2X2/6 receptor with distinct pharmacology from homomeric P2X2, including reduced agonist potencies, biphasic ATP currents (especially with Zn2+), narrower pH enhancement range, and altered pH-dependent suramin blockade.","method":"Coexpression in Xenopus oocytes, voltage-clamp electrophysiology, pharmacological characterization","journal":"The Journal of Neuroscience","confidence":"High","confidence_rationale":"Tier 2 — functional characterization of heteromer with systematic pharmacological profiling","pmids":["10864944"],"is_preprint":false},{"year":2004,"finding":"Co-activation of P2X2 and GABAA receptors (containing α and β but not γ subunits) produces cross-inhibition; the C-terminal domain of P2X2 and the intracellular loop of β GABAA subunits are required for this interaction. In hippocampal neurons, P2X2 co-expression with rho1 containing the β3 C-terminal sequence caused co-clustering/retargeting.","method":"Co-expression in Xenopus oocytes, minigene overexpression, electrophysiology, hippocampal neuron transfection, immunocytochemistry","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 2 — domain mapping with minigenes plus neuronal co-clustering data","pmids":["15456793"],"is_preprint":false},{"year":2008,"finding":"The neuronal calcium sensor VILIP1 forms a signaling complex with P2X2 receptors in vitro and in vivo, regulating P2X2 receptor ATP sensitivity, peak response, surface expression, and lateral diffusion; VILIP1-P2X2 interaction is enhanced in an activation- and Ca2+-dependent manner, and is increased during action potential firing conditions in hippocampal neurons.","method":"Proteomics/co-IP, in vivo co-immunoprecipitation from brain, electrophysiology, surface expression assay, lateral diffusion measurements","journal":"Science Signaling","confidence":"High","confidence_rationale":"Tier 2 — reciprocal co-IP in vivo plus multiple functional readouts","pmids":["18922787"],"is_preprint":false},{"year":2011,"finding":"Neuronal P2X2 receptor lateral mobility in dendrites is heterogeneous, mostly Brownian, and is increased in an activation-dependent manner; mobility is regulated by cytosolic VILIP1 calcium binding protein. Single-molecule imaging with simultaneous whole-cell voltage-clamp confirmed activation-dependent increased receptor mobility.","method":"Single-molecule imaging with quantum dot labels, simultaneous whole-cell voltage-clamp, hippocampal neurons","journal":"The Journal of Neuroscience","confidence":"High","confidence_rationale":"Tier 2 — direct single-molecule measurement of receptor mobility with simultaneous functional recording","pmids":["22090499"],"is_preprint":false},{"year":2005,"finding":"Fe65 (a β-amyloid precursor protein binding protein) interacts with the P2X2 C-terminal domain, colocalizes with P2X2 at postsynaptic specializations of excitatory synapses in CA1 hippocampus, and can be co-immunoprecipitated from brain membrane extracts; Fe65 coexpression inhibits the time-dependent change in P2X2 ionic selectivity.","method":"Yeast two-hybrid, GST pull-down, co-immunoprecipitation from brain, postembedding immunogold EM, double immunogold labeling, electrophysiology","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple methods including in vivo co-IP and ultrastructural localization plus functional consequence","pmids":["16330549"],"is_preprint":false},{"year":2011,"finding":"Disrupting microtubule network with colchicine inhibits dye (Yo-Pro-1) uptake induced by ATP at P2X2 receptors without affecting ionic currents, indicating the cytoskeleton regulates large-pore formation (macropore) but not basic ion channel function of P2X2.","method":"Colchicine treatment, Yo-Pro-1 dye uptake assay, electrophysiology in Xenopus oocytes and HEK293 cells","journal":"British Journal of Pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — functional dissociation of pore and ion channel activities, single lab","pmids":["21306580"],"is_preprint":false},{"year":1998,"finding":"P2X2 receptor function is modulated by extracellular pH; lowering pHe to 6.5 increases ATP affinity ~5-fold without changing maximum activity or agonist potency order; receptor protonation (not agonist protonation) is responsible for the enhancement; suramin blockade is specifically affected by acidification.","method":"Voltage-clamp in Xenopus oocytes expressing recombinant P2X2, systematic pH titration, agonist/antagonist pharmacology","journal":"British Journal of Pharmacology","confidence":"High","confidence_rationale":"Tier 1 — detailed pharmacological characterization with multiple agonists/antagonists at multiple pH values, replicated across studies (PMID 8730726, 9257926)","pmids":["8730726","9257926"],"is_preprint":false},{"year":2009,"finding":"P2X2 channel gating involves both voltage and ATP binding; the flexibility of Gly344 in TM2 contributes to voltage-dependent gating; a three-state model (fast ATP-binding followed by slower gating step) quantitatively reproduces experimental conductance-voltage relationships.","method":"Xenopus oocyte two-electrode voltage-clamp, inside-out patch in HEK293, G344 glycine-scanning mutagenesis, kinetic modeling","journal":"The Journal of General Physiology","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis combined with quantitative kinetic modeling and direct patch recording","pmids":["19114637"],"is_preprint":false},{"year":2009,"finding":"Reactive oxygen species (H2O2) and mercury potentiate P2X2a receptor activity through intracellular Cys430; C430A and C430S mutants abolished potentiation; MTSEA alkylation of Cys430 also prevented potentiation; P2X2b (lacking Cys430-containing region) was unaffected, identifying Cys430 as an intracellular redox sensor.","method":"Chimeric receptor construction, site-directed mutagenesis, MTSET alkylation, Xenopus oocyte and HEK293 electrophysiology","journal":"The Journal of Neuroscience","confidence":"High","confidence_rationale":"Tier 1 — chimeras plus mutagenesis plus chemical modification converge on single residue","pmids":["19793987"],"is_preprint":false},{"year":2002,"finding":"P2X2 desensitization depends on coupling between ectodomain and C-terminal domain; chimeric receptors bearing P2X3 ectodomain desensitized in a receptor-subtype-specific and ligand-nonspecific manner, while P2X7 ectodomain chimeras desensitized in a receptor-nonspecific manner; high-efficacy agonists drive stronger desensitization.","method":"Chimeric receptor construction, Ca2+ imaging and electrophysiology in HEK293 cells","journal":"Molecular Pharmacology","confidence":"Medium","confidence_rationale":"Tier 1 method but mechanistic interpretation relies on chimera data alone, single lab","pmids":["12391283"],"is_preprint":false},{"year":2013,"finding":"P2RX2 p.V60L mutation abolishes ATP-evoked inward current and ATP-stimulated macropore permeability (FM1-43 dye uptake) in heterologous expression; co-expression of mutant and WT subunits reduces ATP-activated membrane permeability in a dominant-negative fashion; P2RX2-null mice develop severe progressive hearing loss and increased noise susceptibility.","method":"Heterologous expression electrophysiology, FM1-43 dye uptake, P2RX2-null mouse audiometry, human genetic co-segregation","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 2 — human mutation with functional validation, null mouse phenotype, dominant-negative mechanism established","pmids":["23345450"],"is_preprint":false},{"year":2012,"finding":"P2X2 and P2X5 subunits associate to form heteromeric receptors with alternate stoichiometries present at the plasma membrane; P2X2/5 receptors display pore dilatation, membrane blebbing, and phosphatidylserine exposure characteristic of P2X7 receptors. Demonstrated by BRET, BiFC, and protein biochemistry in rat brain neurons where P2X2 and P2X5 colocalize.","method":"BRET, bimolecular fluorescence complementation (BiFC), co-immunoprecipitation, confocal colocalization in neurons","journal":"The Journal of Neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 — multiple biochemical methods but alternate stoichiometries not fully resolved","pmids":["22442090"],"is_preprint":false},{"year":2011,"finding":"In mouse spermatozoa, the ATP-activated cation current in the midpiece is mediated by P2X2 receptor; the current is absent in P2rx2−/− mice and has biophysical/pharmacological properties matching heterologously expressed P2X2. P2rx2−/− males show declining fertility with frequent mating.","method":"Whole-spermatozoa patch-clamp, P2rx2 knockout mice, pharmacological profiling","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 2 — knockout plus pharmacological characterization defines function in native cell type","pmids":["21831833"],"is_preprint":false},{"year":2020,"finding":"P2X2 is the relevant ATP receptor on enteric glial cells (EGCs) mediating enteric gliosis; ATP activation of P2X2 triggers a p38 MAPK-dependent pathway causing cytokine release and gliosis phenotype; P2X2 receptor antagonism (including novel antagonist ambroxol) prevented ATP-induced enteric gliosis, inflammation, and dysmotility in murine and human intestine.","method":"P2X2 genetic depletion, receptor antagonism, p38 MAPK pathway analysis, in vivo mouse models, human intestine experiments","journal":"EMBO Molecular Medicine","confidence":"High","confidence_rationale":"Tier 2 — genetic depletion plus pharmacology plus pathway identification in multiple model systems","pmids":["33332729"],"is_preprint":false},{"year":1998,"finding":"P2X2 receptor activity is modulated by extracellular ATP-activated MAP kinases in PC12 cells; calcium influx through P2X2 receptors (not voltage-gated Ca2+ channels) activates ERK1/2 via Pyk2 tyrosine phosphorylation; response requires extracellular calcium and is blocked by suramin.","method":"Western blot for ERK/Pyk2 phosphorylation, pharmacological dissection (suramin, voltage-gated Ca2+ channel blockers), PC12 cells","journal":"The Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — pathway placement via pharmacology, P2X2 identity inferred from pharmacological profile not direct genetic evidence","pmids":["9685331"],"is_preprint":false},{"year":2011,"finding":"GABAA receptors and P2X2 receptors form a transient complex intracellularly that facilitates co-trafficking to the cell surface where they are located primarily extrasynaptically; P2X2 activation causes Ca2+-dependent and Ca2+-independent increases in GABAA receptor mobility and degradation, while P2X2 receptors are stabilized and form larger clusters.","method":"Co-immunoprecipitation in HEK293 cells, FRET, single particle tracking in spinal cord neurons","journal":"The Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — co-IP plus single particle tracking, but mechanistic details of co-trafficking not fully resolved","pmids":["21343285"],"is_preprint":false},{"year":2015,"finding":"α6-containing nicotinic acetylcholine receptors (α6* nAChRs) directly interact with and cross-inhibit P2X2/3 receptors in DRG nociceptors; this interaction contributes to nicotine analgesia; demonstrated by physical interaction between receptors and requirement of α6* (but not α4*) nAChRs for peripheral/spinal nicotine analgesia.","method":"Gain- and loss-of-function nAChR mutants, expression genomics, DRG electrophysiology, behavioral pain models","journal":"Science Translational Medicine","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis plus functional cross-inhibition data, but direct physical interaction method not fully detailed in abstract","pmids":["25972004"],"is_preprint":false},{"year":2009,"finding":"Carbon monoxide (CO) is a potent and selective positive modulator of P2X2 (homomeric) receptors; CO and CO-donor CORM-2 enhanced ATP-evoked P2X2 currents but caused small inhibition of P2X2/3 and P2X4 and had no effect on P2X3; the effect is independent of soluble guanylyl cyclase/cGMP pathway.","method":"Whole-cell patch-clamp in HEK293 expressing recombinant receptors and in native PC12 cells, CO donor pharmacology, guanylyl cyclase inhibition","journal":"British Journal of Pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — native cell confirmation plus recombinant characterization, mechanism of CO action on P2X2 not yet resolved at molecular level","pmids":["19694727"],"is_preprint":false},{"year":2001,"finding":"Cochlear outer sulcus cells (OSC) and vestibular transitional cells (VTC) mediate P2X2-dependent parasensory cation absorption; ATP-stimulated transepithelial current in both cell types showed P2X2 pharmacological profile (ATP>BzATP>αβmeATP potency order, blocked by suramin and gadolinium), mediating endolymph ionic homeostasis.","method":"Vibrating probe current measurement, pharmacological profiling with P2X2-selective agonist/antagonist profile","journal":"The Journal of Neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 — pharmacological identification of P2X2-mediated function in native tissue without genetic confirmation","pmids":["11717350"],"is_preprint":false}],"current_model":"P2RX2 encodes an ATP-gated trimeric cation channel whose homomeric and heteromeric (P2X2/3, P2X2/6, P2X2/5) assemblies are defined by subunit-specific stoichiometries; channel gating involves intersubunit ATP binding in extracellular clefts (involving Lys69, Lys308, Arg290, Glu167), TM2 rotation/separation (gate at Asn333–Thr339, with Gly344 conferring voltage dependence), and conformational rearrangements of the cytosolic domain that drive pore dilation; desensitization kinetics are regulated by C-terminal splice variation, PKC phosphorylation of N-terminal Thr18, PKA phosphorylation of C-terminal Ser431, phosphoinositide binding to C-terminal Lys365/Lys369, and redox sensing via intracellular Cys430; the receptor is modulated by interacting proteins (VILIP1, Fe65, GABAA β-subunits, α6 nAChRs) and is required for cochlear homeostasis/hearing, enteric glial ATP signaling, and nociceptive P2X2/3-dependent pain transmission."},"narrative":{"teleology":[{"year":1995,"claim":"Demonstration that P2X2 and P2X3 coassemble into a heteromeric ATP-gated channel in sensory neurons established the heteromerization principle for the P2X family and explained native DRG ATP currents that no single subunit could reproduce.","evidence":"Coexpression of P2X2+P2X3 in Xenopus oocytes recapitulated DRG neuron ATP current properties by voltage-clamp electrophysiology","pmids":["7566120"],"confidence":"High","gaps":["Subunit stoichiometry not determined","Physical association not yet shown biochemically","No structural information on assembly interface"]},{"year":1997,"claim":"Cross-immunoprecipitation provided the first direct biochemical proof that P2X2 and P2X3 physically associate rather than merely coexist, and showed the heteromer has distinct desensitization properties.","evidence":"Epitope-tagged P2X2/P2X3 co-IP from baculovirus-infected insect cells plus electrophysiology","pmids":["9254665"],"confidence":"High","gaps":["Stoichiometry still undetermined","Native tissue confirmation lacking"]},{"year":1998,"claim":"Multiple regulatory axes of P2X2 were identified simultaneously: extracellular pH enhancement of ATP affinity, PKA phosphorylation of Ser431 reducing current amplitude, glycosylation requirements for surface expression, and C-terminal splice variation controlling desensitization—establishing the channel as an integrator of multiple signaling inputs.","evidence":"pH titration in oocytes (PMID:8730726, 9257926); S431C mutagenesis with PKA dialysis in HEK293 (PMID:9603227); triple N-glycosylation site mutagenesis plus tunicamycin (PMID:9778359); P2X2a/P2X2b splice variant characterization in GT1/HEK293 cells (PMID:9658396)","pmids":["8730726","9257926","9603227","9778359","9658396"],"confidence":"High","gaps":["Structural basis for pH sensing unknown","Whether PKA and splice regulation are independent or synergistic","Relative expression of splice variants across tissues incompletely mapped"]},{"year":2000,"claim":"PKC phosphorylation of N-terminal Thr18 was identified as a second kinase-dependent desensitization switch, and P2X2/6 heteromeric channels with distinct pharmacology were functionally characterized, broadening the combinatorial diversity of P2X2-containing receptors.","evidence":"T18A/T18N mutagenesis plus phosphothreonine immunodetection in oocytes (PMID:10744703); P2X2/P2X6 coexpression pharmacology in oocytes (PMID:10864944)","pmids":["10744703","10864944"],"confidence":"High","gaps":["In vivo relevance of PKC regulation not tested","P2X2/6 stoichiometry undetermined at this point"]},{"year":2004,"claim":"The trimeric quaternary structure of homomeric P2X2 was established biochemically, and real-time FRET measurements revealed that cytosolic domain conformational rearrangements drive pore dilation—linking structure to the progressive permeability change.","evidence":"Chemical cross-linking and co-expression studies (PMID:15313628); AFM and antibody angle measurements (PMID:15657042); CFP/YFP FRET with simultaneous electrophysiology and membrane tethering rescue (PMID:15548662)","pmids":["15313628","15657042","15548662"],"confidence":"High","gaps":["Atomic resolution structure not yet available","Identity of cytosolic domain conformational change not resolved at residue level"]},{"year":2004,"claim":"Alanine-scanning of TM1 and TM2 revealed that both transmembrane domains undergo activation-dependent conformational changes, and identified Y43A/F44A as constitutively active mutants, establishing that the pore is not a passive conduit but an actively gated structure.","evidence":"Systematic Ala-scanning mutagenesis with whole-cell patch-clamp in HEK293 cells","pmids":["15317863"],"confidence":"High","gaps":["Movement of TM1 relative to TM2 during gating not resolved","No cryo-EM or crystal structure to interpret mutant phenotypes"]},{"year":2005,"claim":"Zinc potentiation was localized to an intersubunit site (His120–His213 from adjacent subunits), and Fe65 was identified as a postsynaptic interacting partner that modulates P2X2 ionic selectivity changes—expanding the regulatory landscape beyond lipids and kinases.","evidence":"Concatamer and disulfide trapping approaches for zinc site (PMID:15899882); yeast two-hybrid, co-IP from brain, and immunogold EM for Fe65 (PMID:16330549)","pmids":["15899882","16330549"],"confidence":"High","gaps":["Fe65 interaction domain on P2X2 not finely mapped","Physiological relevance of Fe65 modulation in synaptic signaling untested"]},{"year":2006,"claim":"Phosphoinositide binding at C-terminal Lys365/Lys369 was shown to regulate desensitization and pore dilation, and P2X2/3 heteromer stoichiometry (1P2X2:2P2X3) was defined by mutational rescue, resolving two long-standing questions about channel regulation and assembly.","evidence":"PI3K inhibition plus K365Q/K369Q mutagenesis plus GST pull-down (PMID:16857707); K-to-A mutagenesis rescue in coexpression (PMID:16840712)","pmids":["16857707","16840712"],"confidence":"High","gaps":["Whether PIP2 binds directly in the lipid bilayer or as a soluble headgroup unclear","Stoichiometry defined functionally—structural confirmation needed"]},{"year":2008,"claim":"Patch-clamp coordinated spectroscopy with tetracysteine labels demonstrated that P2X2 pore dilation (I2 state) is an intrinsic channel property driven by cytosolic domain rearrangements, ruling out pannexin-1 as the large-pore conduit, and VILIP1 was identified as a calcium-dependent signaling partner regulating P2X2 surface expression and lateral mobility.","evidence":"Biarsenical fluorophore spectroscopy with Panx1 knockout comparison (PMID:18689682); co-IP from brain, surface expression, and lateral diffusion assays (PMID:18922787)","pmids":["18689682","18922787"],"confidence":"High","gaps":["Structural basis of I2 state at atomic level unknown","VILIP1 binding site on P2X2 not mapped"]},{"year":2009,"claim":"The TM2 gate region was precisely defined (Asn333–Thr339) with opening involving counter-clockwise helix rotation, Gly344 was identified as the structural basis for voltage-dependent gating, and Cys430 was established as an intracellular redox sensor—together providing a nearly complete gating mechanism.","evidence":"SCAM with MTSET on systematic TM2 mutants plus single-channel recording (PMID:19906973); Gly344 scanning mutagenesis with kinetic modeling (PMID:19114637); chimera/mutagenesis/alkylation convergence on Cys430 (PMID:19793987)","pmids":["19906973","19114637","19793987"],"confidence":"High","gaps":["No high-resolution structure of P2X2 in open vs. closed state","Coupling between redox sensing and gating machinery not mechanistically detailed"]},{"year":2012,"claim":"ATP binding was localized to intersubunit clefts with fewer than three occupied sites sufficient for activation, and the Glu167–Arg290 closed-state salt bridge was shown to be disrupted by ATP binding to allow Arg290 to coordinate the γ-phosphate—completing the ligand-to-gate transduction pathway.","evidence":"Concatamers with defined binding site knockouts (PMID:22828800); charge-reversal mutagenesis, mutant cycle analysis, and state-dependent disulfide trapping (PMID:23041661); covalent ATP-analog tethering at N140/L186 (PMID:21576497); stoichiometry of P2X2/3 and P2X2/6 by binding-site mutagenesis (PMID:22378790)","pmids":["22828800","23041661","21576497","22378790"],"confidence":"High","gaps":["No crystal or cryo-EM structure of P2X2 itself","Cooperativity between binding sites not quantitatively resolved","Subunit rearrangement pathway from agonist binding to gate opening not structurally visualized"]},{"year":2013,"claim":"A human P2RX2 missense mutation (p.V60L) was shown to abolish channel function in a dominant-negative fashion, and P2rx2-null mice developed progressive hearing loss, establishing P2RX2 as a deafness gene and linking its channel activity to cochlear homeostasis.","evidence":"Electrophysiology and FM1-43 uptake of V60L mutant, P2rx2-null mouse audiometry, human genetic co-segregation","pmids":["23345450"],"confidence":"High","gaps":["Precise mechanism by which P2X2 loss impairs cochlear function (endolymph composition vs. hair cell signaling) not resolved","Genotype–phenotype correlation across different P2RX2 mutations incomplete"]},{"year":2020,"claim":"P2X2 was identified as the ATP receptor on enteric glial cells that drives p38 MAPK-dependent gliosis, cytokine release, and intestinal dysmotility, extending the channel's physiological roles beyond the nervous system and hearing.","evidence":"Genetic depletion and pharmacological antagonism (ambroxol) of P2X2, p38 MAPK pathway analysis in murine and human intestine","pmids":["33332729"],"confidence":"High","gaps":["Downstream targets of p38 MAPK in enteric glia not fully characterized","Whether P2X2 homomers or heteromers mediate enteric gliosis not determined"]},{"year":null,"claim":"A high-resolution structure of P2X2 in multiple conformational states (closed, open, desensitized) has not been determined, leaving the precise atomic-level gating mechanism, the structural basis of pore dilation, and the mechanism of allosteric modulation by CO, pH, and zinc incompletely resolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No P2X2 crystal or cryo-EM structure in any state","Mechanism of CO potentiation at molecular level unknown","Structural basis for phosphoinositide-dependent desensitization control not visualized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,1,14,18,29]},{"term_id":"GO:0140299","term_label":"molecular sensor activity","supporting_discovery_ids":[30]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[6,25,33,37]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,23,26]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[35,36]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[14,18,29]},{"term_id":"R-HSA-9709957","term_label":"Sensory Perception","supporting_discovery_ids":[32,40]}],"complexes":["P2X2 homotrimer","P2X2/3 heteromer (1:2)","P2X2/6 heteromer (2:1)","P2X2/5 heteromer"],"partners":["P2RX3","P2RX6","P2RX5","VSNL1","APBB1","GABRB3","CHRNA6"],"other_free_text":[]},"mechanistic_narrative":"P2RX2 encodes an ATP-gated cation channel that assembles as a homotrimer or as obligate heteromers with P2X3 (1:2 stoichiometry), P2X6 (2:1), or P2X5 subunits, each combination conferring distinct pharmacology and desensitization kinetics [PMID:7566120, PMID:22378790, PMID:10864944, PMID:22442090]. ATP binds at intersubunit clefts in the extracellular domain—engaging Lys69, Lys308, Arg290, and Glu167—disrupting a closed-state Glu167–Arg290 salt bridge and triggering counter-clockwise rotation and separation of TM2 helices through a gate formed by Asn333–Thr339, with Gly344 conferring voltage dependence [PMID:23041661, PMID:19906973, PMID:19114637, PMID:21576497]. Desensitization is tuned by C-terminal splice variation (P2X2a vs. P2X2b), PKC phosphorylation of N-terminal Thr18, PKA phosphorylation of C-terminal Ser431, phosphoinositide binding at Lys365/Lys369, and redox sensing via intracellular Cys430, while conformational rearrangements of the cytosolic domain drive pore dilation independently of pannexin-1 [PMID:9658396, PMID:10744703, PMID:9603227, PMID:16857707, PMID:19793987, PMID:18689682]. Dominant-negative P2RX2 mutations (p.V60L) cause progressive sensorineural hearing loss in humans, consistent with the channel's role in cochlear endolymph homeostasis and the severe hearing loss of P2rx2-null mice [PMID:23345450]."},"prefetch_data":{"uniprot":{"accession":"Q9UBL9","full_name":"P2X purinoceptor 2","aliases":["ATP receptor","Purinergic receptor"],"length_aa":471,"mass_kda":51.8,"function":"ATP-gated nonselective transmembrane cation channel permeable to potassium, sodium and calcium (PubMed:10570044, PubMed:31636190). Activation by extracellular ATP induces a variety of cellular responses, such as excitatory postsynaptic responses in sensory neurons, neuromuscular junctions (NMJ) formation, hearing, perception of taste and peristalsis (By similarity). In the inner ear, regulates sound transduction and auditory neurotransmission, outer hair cell electromotility, inner ear gap junctions, and K(+) recycling (PubMed:23345450). Mediates synaptic transmission between neurons and from neurons to smooth muscle (By similarity)","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q9UBL9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/P2RX2","classification":"Not Classified","n_dependent_lines":32,"n_total_lines":1208,"dependency_fraction":0.026490066225165563},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/P2RX2","total_profiled":1310},"omim":[{"mim_id":"608224","title":"DEAFNESS, AUTOSOMAL DOMINANT 41; DFNA41","url":"https://www.omim.org/entry/608224"},{"mim_id":"603149","title":"INTERLEUKIN 17A; IL17A","url":"https://www.omim.org/entry/603149"},{"mim_id":"600844","title":"PURINERGIC RECEPTOR P2X, LIGAND-GATED ION CHANNEL, 2; P2RX2","url":"https://www.omim.org/entry/600844"},{"mim_id":"600843","title":"PURINERGIC RECEPTOR P2X, LIGAND-GATED ION CHANNEL, 3; P2RX3","url":"https://www.omim.org/entry/600843"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":12.3},{"tissue":"epididymis","ntpm":20.6},{"tissue":"prostate","ntpm":14.1}],"url":"https://www.proteinatlas.org/search/P2RX2"},"hgnc":{"alias_symbol":["P2X2"],"prev_symbol":["DFNA41"]},"alphafold":{"accession":"Q9UBL9","domains":[{"cath_id":"1.10.287.940","chopping":"40-68_338-378","consensus_level":"high","plddt":90.082,"start":40,"end":378},{"cath_id":"2.60.490.10","chopping":"76-118_183-335","consensus_level":"high","plddt":92.506,"start":76,"end":335},{"cath_id":"-","chopping":"129-178","consensus_level":"medium","plddt":91.4978,"start":129,"end":178}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UBL9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UBL9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UBL9-F1-predicted_aligned_error_v6.png","plddt_mean":79.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=P2RX2","jax_strain_url":"https://www.jax.org/strain/search?query=P2RX2"},"sequence":{"accession":"Q9UBL9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9UBL9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9UBL9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UBL9"}},"corpus_meta":[{"pmid":"7566120","id":"PMC_7566120","title":"Coexpression of P2X2 and P2X3 receptor subunits can account for ATP-gated currents in sensory neurons.","date":"1995","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/7566120","citation_count":867,"is_preprint":false},{"pmid":"10213185","id":"PMC_10213185","title":"Distribution of the P2X2 receptor subunit of the ATP-gated ion channels in the rat central nervous system.","date":"1999","source":"The Journal of comparative neurology","url":"https://pubmed.ncbi.nlm.nih.gov/10213185","citation_count":226,"is_preprint":false},{"pmid":"15657042","id":"PMC_15657042","title":"Atomic force microscopy imaging demonstrates that P2X2 receptors are trimers but that P2X6 receptor subunits do not oligomerize.","date":"2005","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15657042","citation_count":156,"is_preprint":false},{"pmid":"10899177","id":"PMC_10899177","title":"Mechanical allodynia caused by intraplantar injection of P2X receptor agonist in rats: involvement of heteromeric P2X2/3 receptor signaling in capsaicin-insensitive primary afferent neurons.","date":"2000","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/10899177","citation_count":155,"is_preprint":false},{"pmid":"10493739","id":"PMC_10493739","title":"Expression of the P2X(2) receptor subunit of the ATP-gated ion channel in the cochlea: implications for sound transduction and auditory neurotransmission.","date":"1999","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/10493739","citation_count":149,"is_preprint":false},{"pmid":"10744703","id":"PMC_10744703","title":"A protein kinase C site highly conserved in P2X subunits controls the desensitization kinetics of P2X(2) ATP-gated channels.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10744703","citation_count":148,"is_preprint":false},{"pmid":"18689601","id":"PMC_18689601","title":"P2X2 receptors differentiate placodal vs. neural crest C-fiber phenotypes innervating guinea pig lungs and esophagus.","date":"2008","source":"American journal of physiology. Lung cellular and molecular physiology","url":"https://pubmed.ncbi.nlm.nih.gov/18689601","citation_count":135,"is_preprint":false},{"pmid":"10321492","id":"PMC_10321492","title":"Localization of ATP-gated P2X2 and P2X3 receptor immunoreactive nerves in rat taste buds.","date":"1999","source":"Neuroreport","url":"https://pubmed.ncbi.nlm.nih.gov/10321492","citation_count":134,"is_preprint":false},{"pmid":"9257926","id":"PMC_9257926","title":"Effects of extracellular pH on agonism and antagonism at a recombinant P2X2 receptor.","date":"1997","source":"British journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/9257926","citation_count":132,"is_preprint":false},{"pmid":"8730726","id":"PMC_8730726","title":"Full sensitivity of P2X2 purinoceptor to ATP revealed by changing extracellular pH.","date":"1996","source":"British journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/8730726","citation_count":122,"is_preprint":false},{"pmid":"23345450","id":"PMC_23345450","title":"Mutation of the ATP-gated P2X(2) receptor leads to progressive hearing loss and increased susceptibility to noise.","date":"2013","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/23345450","citation_count":119,"is_preprint":false},{"pmid":"21306580","id":"PMC_21306580","title":"Colchicine inhibits cationic dye uptake induced by ATP in P2X2 and P2X7 receptor-expressing cells: implications for its therapeutic action.","date":"2011","source":"British journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/21306580","citation_count":111,"is_preprint":false},{"pmid":"20590629","id":"PMC_20590629","title":"AF-353, a novel, potent and orally bioavailable P2X3/P2X2/3 receptor antagonist.","date":"2010","source":"British journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/20590629","citation_count":105,"is_preprint":false},{"pmid":"10864944","id":"PMC_10864944","title":"Coexpression of rat P2X2 and P2X6 subunits in Xenopus oocytes.","date":"2000","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/10864944","citation_count":105,"is_preprint":false},{"pmid":"20802203","id":"PMC_20802203","title":"Systemic blockade of P2X3 and P2X2/3 receptors attenuates bone cancer pain behaviour in rats.","date":"2010","source":"Brain : a journal of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/20802203","citation_count":105,"is_preprint":false},{"pmid":"15313628","id":"PMC_15313628","title":"Trimeric architecture of homomeric P2X2 and heteromeric P2X1+2 receptor subtypes.","date":"2004","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/15313628","citation_count":99,"is_preprint":false},{"pmid":"9254665","id":"PMC_9254665","title":"Baculovirus expression provides direct evidence for heteromeric assembly of P2X2 and P2X3 receptors.","date":"1997","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/9254665","citation_count":99,"is_preprint":false},{"pmid":"17110047","id":"PMC_17110047","title":"Localization of P2X2 and P2X3 receptors in rat trigeminal ganglion neurons.","date":"2006","source":"Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/17110047","citation_count":90,"is_preprint":false},{"pmid":"9647332","id":"PMC_9647332","title":"Coexpression of mRNAs for P2X1, P2X2 and P2X4 receptors in rat vascular smooth muscle: an in situ hybridization and RT-PCR study.","date":"1998","source":"Journal of vascular research","url":"https://pubmed.ncbi.nlm.nih.gov/9647332","citation_count":85,"is_preprint":false},{"pmid":"30927255","id":"PMC_30927255","title":"Action of MK-7264 (gefapixant) at human P2X3 and P2X2/3 receptors and in vivo efficacy in models of sensitisation.","date":"2019","source":"British journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/30927255","citation_count":79,"is_preprint":false},{"pmid":"15899882","id":"PMC_15899882","title":"An intersubunit zinc binding site in rat P2X2 receptors.","date":"2005","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15899882","citation_count":77,"is_preprint":false},{"pmid":"18689682","id":"PMC_18689682","title":"Patch-clamp coordinated spectroscopy shows P2X2 receptor permeability dynamics require cytosolic domain rearrangements but not Panx-1 channels.","date":"2008","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/18689682","citation_count":72,"is_preprint":false},{"pmid":"11717350","id":"PMC_11717350","title":"P2X2 receptor mediates stimulation of parasensory cation absorption by cochlear outer sulcus cells and vestibular transitional cells.","date":"2001","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/11717350","citation_count":71,"is_preprint":false},{"pmid":"16840712","id":"PMC_16840712","title":"Role of ectodomain lysines in the subunits of the heteromeric P2X2/3 receptor.","date":"2006","source":"Molecular pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/16840712","citation_count":71,"is_preprint":false},{"pmid":"15107474","id":"PMC_15107474","title":"Density-dependent changes of the pore properties of the P2X2 receptor channel.","date":"2004","source":"The Journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/15107474","citation_count":69,"is_preprint":false},{"pmid":"16857707","id":"PMC_16857707","title":"Regulation of the desensitization and ion selectivity of ATP-gated P2X2 channels by phosphoinositides.","date":"2006","source":"The Journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/16857707","citation_count":69,"is_preprint":false},{"pmid":"25972004","id":"PMC_25972004","title":"The nicotinic α6 subunit gene determines variability in chronic pain sensitivity via cross-inhibition of P2X2/3 receptors.","date":"2015","source":"Science translational medicine","url":"https://pubmed.ncbi.nlm.nih.gov/25972004","citation_count":68,"is_preprint":false},{"pmid":"9658396","id":"PMC_9658396","title":"Functional role of alternative splicing in pituitary P2X2 receptor-channel activation and desensitization.","date":"1998","source":"Molecular endocrinology (Baltimore, Md.)","url":"https://pubmed.ncbi.nlm.nih.gov/9658396","citation_count":67,"is_preprint":false},{"pmid":"9838201","id":"PMC_9838201","title":"Localization of ATP-gated P2X2 receptor immunoreactivity in the rat hypothalamus.","date":"1998","source":"Brain research","url":"https://pubmed.ncbi.nlm.nih.gov/9838201","citation_count":67,"is_preprint":false},{"pmid":"33332729","id":"PMC_33332729","title":"A novel P2X2-dependent purinergic mechanism of enteric gliosis in intestinal inflammation.","date":"2020","source":"EMBO molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/33332729","citation_count":66,"is_preprint":false},{"pmid":"10813788","id":"PMC_10813788","title":"Immunohistochemical localization of adenosine 5'-triphosphate-gated ion channel P2X(2) receptor subunits in adult and developing rat cochlea.","date":"2000","source":"The Journal of comparative neurology","url":"https://pubmed.ncbi.nlm.nih.gov/10813788","citation_count":66,"is_preprint":false},{"pmid":"15456793","id":"PMC_15456793","title":"Subunit-specific coupling between gamma-aminobutyric acid type A and P2X2 receptor channels.","date":"2004","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15456793","citation_count":64,"is_preprint":false},{"pmid":"15507220","id":"PMC_15507220","title":"A-317491, a selective P2X3/P2X2/3 receptor antagonist, reverses inflammatory mechanical hyperalgesia through action at peripheral receptors in rats.","date":"2004","source":"European journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/15507220","citation_count":64,"is_preprint":false},{"pmid":"9550147","id":"PMC_9550147","title":"Localization of mRNA encoding the P2X2 receptor subunit of the adenosine 5'-triphosphate-gated ion channel in the adult and developing rat inner ear by in situ hybridization.","date":"1998","source":"The Journal of comparative neurology","url":"https://pubmed.ncbi.nlm.nih.gov/9550147","citation_count":62,"is_preprint":false},{"pmid":"12858039","id":"PMC_12858039","title":"Noise induces up-regulation of P2X2 receptor subunit of ATP-gated ion channels in the rat cochlea.","date":"2003","source":"Neuroreport","url":"https://pubmed.ncbi.nlm.nih.gov/12858039","citation_count":62,"is_preprint":false},{"pmid":"9685331","id":"PMC_9685331","title":"ATP-stimulated activation of the mitogen-activated protein kinases through ionotrophic P2X2 purinoreceptors in PC12 cells. Difference in purinoreceptor sensitivity in two PC12 cell lines.","date":"1998","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9685331","citation_count":62,"is_preprint":false},{"pmid":"22442090","id":"PMC_22442090","title":"P2X2 and P2X5 subunits define a new heteromeric receptor with P2X7-like properties.","date":"2012","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/22442090","citation_count":60,"is_preprint":false},{"pmid":"21385174","id":"PMC_21385174","title":"P2X4 receptors interact with both P2X2 and P2X7 receptors in the form of homotrimers.","date":"2011","source":"British journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/21385174","citation_count":59,"is_preprint":false},{"pmid":"9778359","id":"PMC_9778359","title":"N-Linked glycosylation is essential for the functional expression of the recombinant P2X2 receptor.","date":"1998","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9778359","citation_count":56,"is_preprint":false},{"pmid":"9398614","id":"PMC_9398614","title":"Molecular assembly of the extracellular domain of P2X2, an ATP-gated ion channel.","date":"1997","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/9398614","citation_count":55,"is_preprint":false},{"pmid":"9175089","id":"PMC_9175089","title":"Expression of the P2X2 receptor subunit of the ATP-gated ion channel in the retina.","date":"1997","source":"Neuroreport","url":"https://pubmed.ncbi.nlm.nih.gov/9175089","citation_count":52,"is_preprint":false},{"pmid":"9117113","id":"PMC_9117113","title":"Potentiation of ATP-responses at a recombinant P2x2 receptor by neurotransmitters and related substances.","date":"1997","source":"British journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/9117113","citation_count":52,"is_preprint":false},{"pmid":"21207957","id":"PMC_21207957","title":"Discovery of potent competitive antagonists and positive modulators of the P2X2 receptor.","date":"2011","source":"Journal of medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/21207957","citation_count":51,"is_preprint":false},{"pmid":"9682808","id":"PMC_9682808","title":"Novel variant of the P2X2 ATP receptor from the guinea pig organ of Corti.","date":"1998","source":"Hearing research","url":"https://pubmed.ncbi.nlm.nih.gov/9682808","citation_count":51,"is_preprint":false},{"pmid":"11807844","id":"PMC_11807844","title":"Localization of P2X3 receptors and coexpression with P2X2 receptors during rat embryonic neurogenesis.","date":"2002","source":"The Journal of comparative neurology","url":"https://pubmed.ncbi.nlm.nih.gov/11807844","citation_count":50,"is_preprint":false},{"pmid":"21831833","id":"PMC_21831833","title":"ATP-activated P2X2 current in mouse spermatozoa.","date":"2011","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/21831833","citation_count":49,"is_preprint":false},{"pmid":"24903857","id":"PMC_24903857","title":"Adenosine triphosphate drives head and neck cancer pain through P2X2/3 heterotrimers.","date":"2014","source":"Acta neuropathologica communications","url":"https://pubmed.ncbi.nlm.nih.gov/24903857","citation_count":49,"is_preprint":false},{"pmid":"18922787","id":"PMC_18922787","title":"Regulation of P2X2 receptors by the neuronal calcium sensor VILIP1.","date":"2008","source":"Science signaling","url":"https://pubmed.ncbi.nlm.nih.gov/18922787","citation_count":49,"is_preprint":false},{"pmid":"18032665","id":"PMC_18032665","title":"Thr339-to-serine substitution in rat P2X2 receptor second transmembrane domain causes constitutive opening and indicates a gating role for Lys308.","date":"2007","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/18032665","citation_count":49,"is_preprint":false},{"pmid":"23407944","id":"PMC_23407944","title":"Vascular endothelial cells mediate mechanical stimulation-induced enhancement of endothelin hyperalgesia via activation of P2X2/3 receptors on nociceptors.","date":"2013","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/23407944","citation_count":48,"is_preprint":false},{"pmid":"21576497","id":"PMC_21576497","title":"Agonist trapped in ATP-binding sites of the P2X2 receptor.","date":"2011","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/21576497","citation_count":48,"is_preprint":false},{"pmid":"27709491","id":"PMC_27709491","title":"P2X3 and P2X2/3 Receptors Play a Crucial Role in Articular Hyperalgesia Development Through Inflammatory Mechanisms in the Knee Joint Experimental Synovitis.","date":"2016","source":"Molecular neurobiology","url":"https://pubmed.ncbi.nlm.nih.gov/27709491","citation_count":47,"is_preprint":false},{"pmid":"15317863","id":"PMC_15317863","title":"Gain and loss of channel function by alanine substitutions in the transmembrane segments of the rat ATP-gated P2X2 receptor.","date":"2004","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/15317863","citation_count":47,"is_preprint":false},{"pmid":"15548662","id":"PMC_15548662","title":"Time-resolved measurement of state-specific P2X2 ion channel cytosolic gating motions.","date":"2004","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/15548662","citation_count":47,"is_preprint":false},{"pmid":"14624359","id":"PMC_14624359","title":"Intraganglionic laminar endings in the rat esophagus contain purinergic P2X2 and P2X3 receptor immunoreactivity.","date":"2003","source":"Anatomy and embryology","url":"https://pubmed.ncbi.nlm.nih.gov/14624359","citation_count":46,"is_preprint":false},{"pmid":"19906973","id":"PMC_19906973","title":"Polar residues in the second transmembrane domain of the rat P2X2 receptor that affect spontaneous gating, unitary conductance, and rectification.","date":"2009","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/19906973","citation_count":45,"is_preprint":false},{"pmid":"10639098","id":"PMC_10639098","title":"Inactivation of P2X2 purinoceptors by divalent cations.","date":"2000","source":"The Journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/10639098","citation_count":45,"is_preprint":false},{"pmid":"22828800","id":"PMC_22828800","title":"Activation of trimeric P2X2 receptors by fewer than three ATP molecules.","date":"2012","source":"Molecular pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/22828800","citation_count":45,"is_preprint":false},{"pmid":"12421608","id":"PMC_12421608","title":"Cerebellar lesion up-regulates P2X1 and P2X2 purinergic receptors in precerebellar nuclei.","date":"2002","source":"Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/12421608","citation_count":44,"is_preprint":false},{"pmid":"19833661","id":"PMC_19833661","title":"Double P2X2/P2X3 purinergic receptor knockout mice do not taste NaCl or the artificial sweetener SC45647.","date":"2009","source":"Chemical senses","url":"https://pubmed.ncbi.nlm.nih.gov/19833661","citation_count":43,"is_preprint":false},{"pmid":"21191044","id":"PMC_21191044","title":"Molecular determinants of potent P2X2 antagonism identified by functional analysis, mutagenesis, and homology docking.","date":"2010","source":"Molecular pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/21191044","citation_count":43,"is_preprint":false},{"pmid":"11906966","id":"PMC_11906966","title":"Kinetics of antagonist actions at rat P2X2/3 heteromeric receptors.","date":"2002","source":"British journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/11906966","citation_count":42,"is_preprint":false},{"pmid":"9603227","id":"PMC_9603227","title":"Functional modulation of P2X2 receptors by cyclic AMP-dependent protein kinase.","date":"1998","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9603227","citation_count":41,"is_preprint":false},{"pmid":"14521999","id":"PMC_14521999","title":"Localisation of P2X2 receptor subunit immunoreactivity on nitric oxide synthase expressing neurones in the brain stem and hypothalamus of the rat: a fluorescence immunohistochemical study.","date":"2003","source":"Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/14521999","citation_count":40,"is_preprint":false},{"pmid":"15236470","id":"PMC_15236470","title":"OFF-cholinergic-pathway-selective localization of P2X2 purinoceptors in the mouse retina.","date":"2004","source":"The Journal of comparative neurology","url":"https://pubmed.ncbi.nlm.nih.gov/15236470","citation_count":39,"is_preprint":false},{"pmid":"20558155","id":"PMC_20558155","title":"Involvement of temporomandibular joint P2X3 and P2X2/3 receptors in carrageenan-induced inflammatory hyperalgesia in rats.","date":"2010","source":"European journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/20558155","citation_count":39,"is_preprint":false},{"pmid":"9507969","id":"PMC_9507969","title":"P2X2 receptor subunit expression in a subpopulation of cochlear type I spiral ganglion neurones.","date":"1998","source":"Neuroreport","url":"https://pubmed.ncbi.nlm.nih.gov/9507969","citation_count":39,"is_preprint":false},{"pmid":"10517803","id":"PMC_10517803","title":"Identification of amino acids within the P2X2 receptor C-terminus that regulate desensitization.","date":"1999","source":"The Journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/10517803","citation_count":39,"is_preprint":false},{"pmid":"19671169","id":"PMC_19671169","title":"Subtype-specific regulation of P2X3 and P2X2/3 receptors by phosphoinositides in peripheral nociceptors.","date":"2009","source":"Molecular pain","url":"https://pubmed.ncbi.nlm.nih.gov/19671169","citation_count":38,"is_preprint":false},{"pmid":"24325936","id":"PMC_24325936","title":"Intrathecal leptin inhibits expression of the P2X2/3 receptors and alleviates neuropathic pain induced by chronic constriction sciatic nerve injury.","date":"2013","source":"Molecular pain","url":"https://pubmed.ncbi.nlm.nih.gov/24325936","citation_count":38,"is_preprint":false},{"pmid":"17917716","id":"PMC_17917716","title":"Therapeutic effects of the putative P2X3/P2X2/3 antagonist A-317491 on cyclophosphamide-induced cystitis in rats.","date":"2007","source":"Naunyn-Schmiedeberg's archives of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/17917716","citation_count":38,"is_preprint":false},{"pmid":"12690440","id":"PMC_12690440","title":"P2X(2) purine receptor immunoreactivity of intraganglionic laminar endings in the mouse gastrointestinal tract.","date":"2003","source":"Cell and tissue research","url":"https://pubmed.ncbi.nlm.nih.gov/12690440","citation_count":37,"is_preprint":false},{"pmid":"12395104","id":"PMC_12395104","title":"ATP-gated ion channels assembled from P2X2 receptor subunits in the mouse cochlea.","date":"2002","source":"Neuroreport","url":"https://pubmed.ncbi.nlm.nih.gov/12395104","citation_count":37,"is_preprint":false},{"pmid":"16219297","id":"PMC_16219297","title":"Visualization of the trimeric P2X2 receptor with a crown-capped extracellular domain.","date":"2005","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/16219297","citation_count":37,"is_preprint":false},{"pmid":"16330549","id":"PMC_16330549","title":"Fe65 interacts with P2X2 subunits at excitatory synapses and modulates receptor function.","date":"2005","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16330549","citation_count":36,"is_preprint":false},{"pmid":"12844512","id":"PMC_12844512","title":"Dehydroepiandrosterone potentiates native ionotropic ATP receptors containing the P2X2 subunit in rat sensory neurones.","date":"2003","source":"The Journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/12844512","citation_count":35,"is_preprint":false},{"pmid":"29325454","id":"PMC_29325454","title":"Down-expression of P2RX2, KCNQ5, ERBB3 and SOCS3 through DNA hypermethylation in elderly women with presbycusis.","date":"2018","source":"Biomarkers : biochemical indicators of exposure, response, and susceptibility to chemicals","url":"https://pubmed.ncbi.nlm.nih.gov/29325454","citation_count":33,"is_preprint":false},{"pmid":"21343285","id":"PMC_21343285","title":"Regulation of GABA(A) receptor dynamics by interaction with purinergic P2X(2) receptors.","date":"2011","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/21343285","citation_count":33,"is_preprint":false},{"pmid":"20868656","id":"PMC_20868656","title":"P2X3 and P2X2/3 receptors mediate mechanical hyperalgesia induced by bradykinin, but not by pro-inflammatory cytokines, PGE₂ or dopamine.","date":"2010","source":"European journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/20868656","citation_count":32,"is_preprint":false},{"pmid":"18048351","id":"PMC_18048351","title":"On the role of the first transmembrane domain in cation permeability and flux of the ATP-gated P2X2 receptor.","date":"2007","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/18048351","citation_count":32,"is_preprint":false},{"pmid":"24211385","id":"PMC_24211385","title":"A novel P2RX2 mutation in an Italian family affected by autosomal dominant nonsyndromic hearing loss.","date":"2013","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/24211385","citation_count":31,"is_preprint":false},{"pmid":"21409380","id":"PMC_21409380","title":"Effects of ischemia and reperfusion on P2X2 receptor expressing neurons of the rat ileum enteric nervous system.","date":"2011","source":"Digestive diseases and sciences","url":"https://pubmed.ncbi.nlm.nih.gov/21409380","citation_count":31,"is_preprint":false},{"pmid":"27129281","id":"PMC_27129281","title":"Modulation of P2X3 and P2X2/3 Receptors by Monoclonal Antibodies.","date":"2016","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/27129281","citation_count":30,"is_preprint":false},{"pmid":"31726893","id":"PMC_31726893","title":"Update on novel purinergic P2X3 and P2X2/3 receptor antagonists and their potential therapeutic applications.","date":"2019","source":"Expert opinion on therapeutic patents","url":"https://pubmed.ncbi.nlm.nih.gov/31726893","citation_count":30,"is_preprint":false},{"pmid":"19694727","id":"PMC_19694727","title":"Carbon monoxide is a rapid modulator of recombinant and native P2X(2) ligand-gated ion channels.","date":"2009","source":"British journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/19694727","citation_count":29,"is_preprint":false},{"pmid":"23419459","id":"PMC_23419459","title":"Botulinum toxin A detrusor injections reduce postsynaptic muscular M2, M3, P2X2, and P2X3 receptors in children and adolescents who have neurogenic detrusor overactivity: a single-blind study.","date":"2013","source":"Urology","url":"https://pubmed.ncbi.nlm.nih.gov/23419459","citation_count":29,"is_preprint":false},{"pmid":"22422599","id":"PMC_22422599","title":"Spontaneous firing and evoked responses of spinal nociceptive neurons are attenuated by blockade of P2X3 and P2X2/3 receptors in inflamed rats.","date":"2012","source":"Journal of neuroscience research","url":"https://pubmed.ncbi.nlm.nih.gov/22422599","citation_count":29,"is_preprint":false},{"pmid":"22090499","id":"PMC_22090499","title":"Neuronal P2X2 receptors are mobile ATP sensors that explore the plasma membrane when activated.","date":"2011","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/22090499","citation_count":29,"is_preprint":false},{"pmid":"19114637","id":"PMC_19114637","title":"Voltage- and [ATP]-dependent gating of the P2X(2) ATP receptor channel.","date":"2009","source":"The Journal of general physiology","url":"https://pubmed.ncbi.nlm.nih.gov/19114637","citation_count":28,"is_preprint":false},{"pmid":"12391283","id":"PMC_12391283","title":"Purinergic P2X(2) receptor desensitization depends on coupling between ectodomain and C-terminal domain.","date":"2002","source":"Molecular pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/12391283","citation_count":28,"is_preprint":false},{"pmid":"20677337","id":"PMC_20677337","title":"Effects of protein deprivation and re-feeding on P2X2 receptors in enteric neurons.","date":"2010","source":"World journal of gastroenterology","url":"https://pubmed.ncbi.nlm.nih.gov/20677337","citation_count":27,"is_preprint":false},{"pmid":"12161595","id":"PMC_12161595","title":"A novel locus for autosomal dominant non-syndromic deafness (DFNA41) maps to chromosome 12q24-qter.","date":"2002","source":"Journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/12161595","citation_count":27,"is_preprint":false},{"pmid":"19064335","id":"PMC_19064335","title":"Expressions of P2X2 and P2X3 receptors in rat nodose neurons after myocardial ischemia injury.","date":"2008","source":"Autonomic neuroscience : basic & clinical","url":"https://pubmed.ncbi.nlm.nih.gov/19064335","citation_count":27,"is_preprint":false},{"pmid":"23041661","id":"PMC_23041661","title":"Salt bridge switching from Arg290/Glu167 to Arg290/ATP promotes the closed-to-open transition of the P2X2 receptor.","date":"2012","source":"Molecular pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/23041661","citation_count":27,"is_preprint":false},{"pmid":"17664346","id":"PMC_17664346","title":"Responses of rat P2X2 receptors to ultrashort pulses of ATP provide insights into ATP binding and channel gating.","date":"2007","source":"The Journal of general physiology","url":"https://pubmed.ncbi.nlm.nih.gov/17664346","citation_count":27,"is_preprint":false},{"pmid":"19793987","id":"PMC_19793987","title":"Reactive oxygen species potentiate the P2X2 receptor activity through intracellular Cys430.","date":"2009","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/19793987","citation_count":26,"is_preprint":false},{"pmid":"21410458","id":"PMC_21410458","title":"Characterization of three diaminopyrimidines as potent and selective antagonists of P2X3 and P2X2/3 receptors with in vivo efficacy in a pain model.","date":"2011","source":"British journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/21410458","citation_count":26,"is_preprint":false},{"pmid":"8842447","id":"PMC_8842447","title":"A comparison of the binding characteristics of recombinant P2X1 and P2X2 purinoceptors.","date":"1996","source":"British journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/8842447","citation_count":26,"is_preprint":false},{"pmid":"22378790","id":"PMC_22378790","title":"ATP binding site mutagenesis reveals different subunit stoichiometry of functional P2X2/3 and P2X2/6 receptors.","date":"2012","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22378790","citation_count":25,"is_preprint":false},{"pmid":"31133659","id":"PMC_31133659","title":"Effects of 1,8-cineole on neuropathic pain mediated by P2X2 receptor in the spinal cord dorsal horn.","date":"2019","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/31133659","citation_count":25,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":53395,"output_tokens":9529,"usd":0.15156},"stage2":{"model":"claude-opus-4-6","input_tokens":13472,"output_tokens":3979,"usd":0.250252},"total_usd":0.401812,"stage1_batch_id":"msgbatch_012ZiiCUBfB62NCTQd4Bk1Jo","stage2_batch_id":"msgbatch_01Xuqq9aUHoQouS7UVGZNStZ","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1995,\n      \"finding\": \"P2X2 and P2X3 subunits heteropolymerize to form a novel ATP-gated ion channel in sensory neurons; coexpression of P2X2 and P2X3 (but not other combinations) in Xenopus oocytes reproduced the ATP-gated currents of dorsal root ganglion neurons, indicating heteromeric channel formation.\",\n      \"method\": \"Xenopus oocyte coexpression, voltage-clamp electrophysiology\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution in heterologous system, foundational paper with 867 citations, replicated by multiple subsequent studies\",\n      \"pmids\": [\"7566120\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"P2X2 and P2X3 subunits physically associate to form heteromeric channels with distinct agonist sensitivity and desensitization properties; cross-immunoprecipitation with epitope-tagged subunits in baculovirus-infected insect cells provided direct biochemical evidence for heteromeric assembly.\",\n      \"method\": \"Baculovirus expression in insect cells, cross-immunoprecipitation, whole-cell electrophysiology\",\n      \"journal\": \"The Journal of Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct biochemical reconstitution plus functional characterization in same study\",\n      \"pmids\": [\"9254665\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"P2X2 receptors are trimers; chemical cross-linking produced higher-order adducts consistent with trimers, AFM imaging gave mean molecular volume of ~409 nm³ consistent with a trimer, and angle measurements between two bound anti-His antibodies on doubly-labeled receptors averaged 123°, indicating trimeric architecture.\",\n      \"method\": \"Chemical cross-linking, atomic force microscopy (AFM), anti-epitope antibody angle measurement\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple orthogonal structural methods in one study, consistent with crystal structure data from related P2X receptors\",\n      \"pmids\": [\"15657042\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Homomeric P2X2 receptors are trimers; biochemical cross-linking and co-expression studies confirmed trimeric architecture for slowly desensitizing P2X subtypes including P2X2, P2X4, and P2X5, while P2X6 subunits were retained in ER as non-trimeric aggregates.\",\n      \"method\": \"Chemical cross-linking, co-expression studies, Western blot\",\n      \"journal\": \"Journal of Molecular Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — biochemical reconstitution with multiple subunit combinations, consistent with AFM data\",\n      \"pmids\": [\"15313628\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"A conserved protein kinase C phosphorylation site (TXK/R motif) in the intracellular N-terminus of P2X2, specifically Thr18, controls desensitization kinetics; mutations at Thr18 (T18A, T18N) or K20T converted slow desensitization (>1 min) to fast desensitization (<1 s), and direct phosphorylation of Thr18 by PKC was demonstrated by immunodetection. Interaction between both cytoplasmic domains is also required for slow desensitization.\",\n      \"method\": \"Site-directed mutagenesis, voltage-clamp in Xenopus oocytes, immunodetection of phosphothreonine\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis plus direct phosphorylation detection, multiple mutant characterizations\",\n      \"pmids\": [\"10744703\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"PKA phosphorylation of Ser431 in the intracellular C-terminus of P2X2 reduces ATP-activated current amplitude; intracellular perfusion of 8-bromo-cAMP or PKA catalytic subunit reduced current in wild-type but not S431C mutant receptors expressed in HEK293 cells.\",\n      \"method\": \"Site-directed mutagenesis, whole-cell patch-clamp, intracellular dialysis of PKA/cAMP\",\n      \"journal\": \"Journal of Neurochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis combined with direct enzyme application identifies specific phosphorylation site\",\n      \"pmids\": [\"9603227\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"N-linked glycosylation at three extracellular asparagine residues (N182, N239, N298) of P2X2 is essential for cell-surface expression; tunicamycin treatment or triple-site mutagenesis abolished ATP responses and drastically reduced surface expression as shown by biotin labeling and immunofluorescence.\",\n      \"method\": \"Site-directed mutagenesis, tunicamycin treatment, surface biotinylation, immunofluorescence, whole-cell recording\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — two independent approaches (pharmacological and mutagenesis) converging on same mechanism\",\n      \"pmids\": [\"9778359\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Alternative splicing of P2X2 generates isoforms (P2X2a and P2X2b/P2X2-2) that differ in their C-terminal sequences; P2X2b lacks Val370-Gln438 and desensitizes rapidly and completely, whereas P2X2a desensitizes slowly and incompletely. Both isoforms have similar EC50 for ATP. Coexpression of both isoforms can reproduce intermediate desensitization rates seen in native somatotrophs.\",\n      \"method\": \"Heterologous expression in GT1/HEK293 cells, Ca2+ imaging, electrophysiology, RT-PCR in enriched pituitary subpopulations\",\n      \"journal\": \"Molecular Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — functional reconstitution of native behavior from defined splice variants\",\n      \"pmids\": [\"9658396\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"C-terminal residues near the splice site regulate desensitization rate: truncation at Lys369 accelerated desensitization >100-fold; a single Val370 residue slowed desensitization ~70-fold; the hydrophobicity of Val370 (not its exact structure) determines rate; nearby lysines (especially Lys365) also modulate desensitization.\",\n      \"method\": \"Site-directed mutagenesis, two-electrode voltage-clamp in Xenopus oocytes, peptide injection\",\n      \"journal\": \"The Journal of Physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic mutagenesis with peptide rescue experiment, multiple independent mutations tested\",\n      \"pmids\": [\"10517803\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Phosphoinositides (PIP2, PIP3) regulate P2X2 channel desensitization and pore dilation through direct electrostatic interaction with positively charged residues (Lys365, Lys369) in the proximal cytoplasmic C-terminal domain; PI3K inhibition accelerated desensitization, and K365Q/K369Q mutations mimicked this effect and abolished lipid binding in GST pull-down assays.\",\n      \"method\": \"PI3K inhibition, site-directed mutagenesis, two-electrode voltage-clamp, GST pull-down with PIP-coated membranes, fluorescence assay in COS-7 cells\",\n      \"journal\": \"The Journal of Physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct lipid binding assay combined with mutagenesis and electrophysiology\",\n      \"pmids\": [\"16857707\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Zinc potentiates P2X2 channel opening via an intersubunit binding site formed by His120 and His213 from adjacent subunits; mixing H120A and H213A single mutants restored zinc potentiation, trimeric concatamers showed zinc potentiation correlating with intersubunit histidine pairs, and H120C/H213C formed ectopic intersubunit disulfide bonds detectable by non-reducing Western blot.\",\n      \"method\": \"Site-directed mutagenesis, trimeric concatamer expression, Xenopus oocyte electrophysiology, non-reducing Western blot, redox manipulation\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — five independent lines of evidence including disulfide trapping and concatamer approach\",\n      \"pmids\": [\"15899882\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"P2X2 channel pore properties (permeability to large cations, inward rectification, ligand sensitivity) depend on channel expression density; Ile328 at the outer pore mouth is critical for these density-dependent changes, as shown by mutagenesis.\",\n      \"method\": \"Variable expression levels in Xenopus oocytes, mutagenesis, two-electrode voltage-clamp\",\n      \"journal\": \"The Journal of Physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 method but single lab, single study\",\n      \"pmids\": [\"15107474\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"TM1 and TM2 of P2X2 participate in conformational changes during activation; alanine-scanning mutagenesis identified residues in TM1 (pattern consistent with helix) and TM2 that altered ATP potency, BzATP efficacy, and deactivation kinetics. Y43A and F44A in TM1 produced spontaneously active channels.\",\n      \"method\": \"Alanine-scanning mutagenesis, whole-cell patch-clamp in HEK293 cells\",\n      \"journal\": \"The Journal of Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic mutagenesis across both TM domains with multiple functional readouts\",\n      \"pmids\": [\"15317863\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Thr339 in TM2 is critical for gating; T339S mutation causes constitutive channel opening and 10-fold increase in ATP sensitivity. Lys308 is involved in gating (not just ATP binding): K308A suppresses spontaneous activity of T339S but K69A does not, indicating Lys308 has a gating role distinct from ATP coordination.\",\n      \"method\": \"Site-directed mutagenesis, single-channel and whole-cell recording in HEK293 cells\",\n      \"journal\": \"The Journal of Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — constitutively active mutant plus epistatic double-mutant analysis\",\n      \"pmids\": [\"18032665\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Polar residues in TM2 define the channel gate and permeation pathway; Thr336, Thr339, and Ser340 are exposed in the open channel pore (introduction of positive charge greatly enhanced outward currents); Asn333 and Asp349 lie in external and internal vestibules respectively; gate is formed by residues Asn333-Thr339, with channel opening involving counter-clockwise rotation and separation of TM2 helices.\",\n      \"method\": \"Systematic TM2 mutagenesis, MTSET modification, single-channel recordings, Xenopus oocytes\",\n      \"journal\": \"The Journal of Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — SCAM approach combined with crystal structure interpretation, systematic mutagenesis\",\n      \"pmids\": [\"19906973\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"FRET measurements revealed time-resolved cytosolic gating motions in P2X2 channels that correlate with permeability changes; wild-type and mutant channels that do not undergo permeability changes also show no cytosolic FRET changes; tethering the cytosolic domain to the plasma membrane prevents both permeability change and cytosolic motions.\",\n      \"method\": \"FRET (CFP/YFP on cytosolic domain), simultaneous whole-cell electrophysiology, tethering experiments\",\n      \"journal\": \"The Journal of Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — real-time structural measurements correlated with function, with rescue experiment\",\n      \"pmids\": [\"15548662\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"P2X2 receptor permeability dynamics (I2 state) are an intrinsic channel property requiring cytosolic domain rearrangements; Pannexin-1 channels make no detectable contribution. Patch-clamp coordinated spectroscopy with tetracysteine/biarsenical fluorophores measured site-specific conformational changes in the cytosolic domain correlated with permeability increases.\",\n      \"method\": \"Patch-clamp coordinated spectroscopy, tetracysteine tagging, biarsenical fluorophores, Panx-1 knockout comparison\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — novel spectroscopy method combined with genetic knockout control distinguishes two mechanistic models\",\n      \"pmids\": [\"18689682\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"ATP-binding sites are located in intersubunit extracellular cavities; covalent tethering of ATP-analog NCS-ATP to single cysteine mutants at N140 and L186 (from two adjacent subunits, ~18 Å apart) trapped agonist-bound states with distinct functional consequences: labeling at one position impedes gating efficiency, labeling at the other enhances subsequent ATP function.\",\n      \"method\": \"Covalent tethering with thiol-reactive ATP analog, whole-cell and single-channel recording, P2X2 homology modeling\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — chemical biology approach directly localizes binding site with functional validation\",\n      \"pmids\": [\"21576497\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Trimeric P2X2 receptors can be activated by fewer than three ATP molecules; concatamers with only two intact Lys69 binding sites (KKA, KAK, AKK) formed functional channels, with KKA and KAK producing larger currents than AKK, indicating asymmetric contributions from different subunit interfaces.\",\n      \"method\": \"Trimeric concatamers with defined ATP-binding site mutations, Western blot, whole-cell and outside-out patch recording in HEK293 cells\",\n      \"journal\": \"Molecular Pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — concatenated subunit approach directly tests stoichiometry of activation\",\n      \"pmids\": [\"22828800\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"A salt bridge between Glu167 and Arg290 stabilizes the closed state; ATP binding disrupts this bridge, allowing Arg290 to coordinate the γ-phosphate of ATP. Charge-reversal mutagenesis, mutant cycle analysis, and disulfide trapping demonstrated the Glu167/Arg290 interaction in the closed state and its absence in the open state.\",\n      \"method\": \"Homology modeling, charge-reversal mutagenesis, mutant cycle analysis, disulfide trapping, electrophysiology\",\n      \"journal\": \"Molecular Pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple orthogonal methods including thermodynamic cycle analysis and state-dependent disulfide trapping\",\n      \"pmids\": [\"23041661\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Ectodomain lysine residues in P2X2 (Lys69 and Lys308) contribute to ATP binding/gating in heteromeric P2X2/3 receptors; P2X2/3 heteromers contain one P2X2 and two P2X3 subunits, as single lysine mutations in P2X2 were rescued by wild-type P2X3 but not vice versa, and double P2X2 lysine mutant was not rescued.\",\n      \"method\": \"Lysine-to-alanine mutagenesis, co-expression in HEK293 cells, whole-cell voltage-clamp\",\n      \"journal\": \"Molecular Pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — mutational rescue approach defines stoichiometry, replicated finding consistent with PMID 22378790\",\n      \"pmids\": [\"16840712\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"P2X2/3 heteromers contain one P2X2 and two P2X3 subunits, while P2X2/6 heteromers contain two P2X2 and one P2X6 subunit; demonstrated by selective blockade of function using ATP-binding site mutants in each subunit position, confirmed by protein labeling and PAGE.\",\n      \"method\": \"ATP-binding site mutagenesis (non-functional Ala substitutions), patch-clamp, Ca2+ imaging, surface protein labeling and PAGE in HEK293 cells and Xenopus oocytes\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — functional and biochemical approaches both support same stoichiometry conclusion, consistent with PMID 16840712\",\n      \"pmids\": [\"22378790\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Coexpression of P2X2 and P2X6 subunits forms a heteromeric P2X2/6 receptor with distinct pharmacology from homomeric P2X2, including reduced agonist potencies, biphasic ATP currents (especially with Zn2+), narrower pH enhancement range, and altered pH-dependent suramin blockade.\",\n      \"method\": \"Coexpression in Xenopus oocytes, voltage-clamp electrophysiology, pharmacological characterization\",\n      \"journal\": \"The Journal of Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — functional characterization of heteromer with systematic pharmacological profiling\",\n      \"pmids\": [\"10864944\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Co-activation of P2X2 and GABAA receptors (containing α and β but not γ subunits) produces cross-inhibition; the C-terminal domain of P2X2 and the intracellular loop of β GABAA subunits are required for this interaction. In hippocampal neurons, P2X2 co-expression with rho1 containing the β3 C-terminal sequence caused co-clustering/retargeting.\",\n      \"method\": \"Co-expression in Xenopus oocytes, minigene overexpression, electrophysiology, hippocampal neuron transfection, immunocytochemistry\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — domain mapping with minigenes plus neuronal co-clustering data\",\n      \"pmids\": [\"15456793\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The neuronal calcium sensor VILIP1 forms a signaling complex with P2X2 receptors in vitro and in vivo, regulating P2X2 receptor ATP sensitivity, peak response, surface expression, and lateral diffusion; VILIP1-P2X2 interaction is enhanced in an activation- and Ca2+-dependent manner, and is increased during action potential firing conditions in hippocampal neurons.\",\n      \"method\": \"Proteomics/co-IP, in vivo co-immunoprecipitation from brain, electrophysiology, surface expression assay, lateral diffusion measurements\",\n      \"journal\": \"Science Signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP in vivo plus multiple functional readouts\",\n      \"pmids\": [\"18922787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Neuronal P2X2 receptor lateral mobility in dendrites is heterogeneous, mostly Brownian, and is increased in an activation-dependent manner; mobility is regulated by cytosolic VILIP1 calcium binding protein. Single-molecule imaging with simultaneous whole-cell voltage-clamp confirmed activation-dependent increased receptor mobility.\",\n      \"method\": \"Single-molecule imaging with quantum dot labels, simultaneous whole-cell voltage-clamp, hippocampal neurons\",\n      \"journal\": \"The Journal of Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct single-molecule measurement of receptor mobility with simultaneous functional recording\",\n      \"pmids\": [\"22090499\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Fe65 (a β-amyloid precursor protein binding protein) interacts with the P2X2 C-terminal domain, colocalizes with P2X2 at postsynaptic specializations of excitatory synapses in CA1 hippocampus, and can be co-immunoprecipitated from brain membrane extracts; Fe65 coexpression inhibits the time-dependent change in P2X2 ionic selectivity.\",\n      \"method\": \"Yeast two-hybrid, GST pull-down, co-immunoprecipitation from brain, postembedding immunogold EM, double immunogold labeling, electrophysiology\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple methods including in vivo co-IP and ultrastructural localization plus functional consequence\",\n      \"pmids\": [\"16330549\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Disrupting microtubule network with colchicine inhibits dye (Yo-Pro-1) uptake induced by ATP at P2X2 receptors without affecting ionic currents, indicating the cytoskeleton regulates large-pore formation (macropore) but not basic ion channel function of P2X2.\",\n      \"method\": \"Colchicine treatment, Yo-Pro-1 dye uptake assay, electrophysiology in Xenopus oocytes and HEK293 cells\",\n      \"journal\": \"British Journal of Pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional dissociation of pore and ion channel activities, single lab\",\n      \"pmids\": [\"21306580\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"P2X2 receptor function is modulated by extracellular pH; lowering pHe to 6.5 increases ATP affinity ~5-fold without changing maximum activity or agonist potency order; receptor protonation (not agonist protonation) is responsible for the enhancement; suramin blockade is specifically affected by acidification.\",\n      \"method\": \"Voltage-clamp in Xenopus oocytes expressing recombinant P2X2, systematic pH titration, agonist/antagonist pharmacology\",\n      \"journal\": \"British Journal of Pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — detailed pharmacological characterization with multiple agonists/antagonists at multiple pH values, replicated across studies (PMID 8730726, 9257926)\",\n      \"pmids\": [\"8730726\", \"9257926\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"P2X2 channel gating involves both voltage and ATP binding; the flexibility of Gly344 in TM2 contributes to voltage-dependent gating; a three-state model (fast ATP-binding followed by slower gating step) quantitatively reproduces experimental conductance-voltage relationships.\",\n      \"method\": \"Xenopus oocyte two-electrode voltage-clamp, inside-out patch in HEK293, G344 glycine-scanning mutagenesis, kinetic modeling\",\n      \"journal\": \"The Journal of General Physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis combined with quantitative kinetic modeling and direct patch recording\",\n      \"pmids\": [\"19114637\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Reactive oxygen species (H2O2) and mercury potentiate P2X2a receptor activity through intracellular Cys430; C430A and C430S mutants abolished potentiation; MTSEA alkylation of Cys430 also prevented potentiation; P2X2b (lacking Cys430-containing region) was unaffected, identifying Cys430 as an intracellular redox sensor.\",\n      \"method\": \"Chimeric receptor construction, site-directed mutagenesis, MTSET alkylation, Xenopus oocyte and HEK293 electrophysiology\",\n      \"journal\": \"The Journal of Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — chimeras plus mutagenesis plus chemical modification converge on single residue\",\n      \"pmids\": [\"19793987\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"P2X2 desensitization depends on coupling between ectodomain and C-terminal domain; chimeric receptors bearing P2X3 ectodomain desensitized in a receptor-subtype-specific and ligand-nonspecific manner, while P2X7 ectodomain chimeras desensitized in a receptor-nonspecific manner; high-efficacy agonists drive stronger desensitization.\",\n      \"method\": \"Chimeric receptor construction, Ca2+ imaging and electrophysiology in HEK293 cells\",\n      \"journal\": \"Molecular Pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 method but mechanistic interpretation relies on chimera data alone, single lab\",\n      \"pmids\": [\"12391283\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"P2RX2 p.V60L mutation abolishes ATP-evoked inward current and ATP-stimulated macropore permeability (FM1-43 dye uptake) in heterologous expression; co-expression of mutant and WT subunits reduces ATP-activated membrane permeability in a dominant-negative fashion; P2RX2-null mice develop severe progressive hearing loss and increased noise susceptibility.\",\n      \"method\": \"Heterologous expression electrophysiology, FM1-43 dye uptake, P2RX2-null mouse audiometry, human genetic co-segregation\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — human mutation with functional validation, null mouse phenotype, dominant-negative mechanism established\",\n      \"pmids\": [\"23345450\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"P2X2 and P2X5 subunits associate to form heteromeric receptors with alternate stoichiometries present at the plasma membrane; P2X2/5 receptors display pore dilatation, membrane blebbing, and phosphatidylserine exposure characteristic of P2X7 receptors. Demonstrated by BRET, BiFC, and protein biochemistry in rat brain neurons where P2X2 and P2X5 colocalize.\",\n      \"method\": \"BRET, bimolecular fluorescence complementation (BiFC), co-immunoprecipitation, confocal colocalization in neurons\",\n      \"journal\": \"The Journal of Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple biochemical methods but alternate stoichiometries not fully resolved\",\n      \"pmids\": [\"22442090\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In mouse spermatozoa, the ATP-activated cation current in the midpiece is mediated by P2X2 receptor; the current is absent in P2rx2−/− mice and has biophysical/pharmacological properties matching heterologously expressed P2X2. P2rx2−/− males show declining fertility with frequent mating.\",\n      \"method\": \"Whole-spermatozoa patch-clamp, P2rx2 knockout mice, pharmacological profiling\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — knockout plus pharmacological characterization defines function in native cell type\",\n      \"pmids\": [\"21831833\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"P2X2 is the relevant ATP receptor on enteric glial cells (EGCs) mediating enteric gliosis; ATP activation of P2X2 triggers a p38 MAPK-dependent pathway causing cytokine release and gliosis phenotype; P2X2 receptor antagonism (including novel antagonist ambroxol) prevented ATP-induced enteric gliosis, inflammation, and dysmotility in murine and human intestine.\",\n      \"method\": \"P2X2 genetic depletion, receptor antagonism, p38 MAPK pathway analysis, in vivo mouse models, human intestine experiments\",\n      \"journal\": \"EMBO Molecular Medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic depletion plus pharmacology plus pathway identification in multiple model systems\",\n      \"pmids\": [\"33332729\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"P2X2 receptor activity is modulated by extracellular ATP-activated MAP kinases in PC12 cells; calcium influx through P2X2 receptors (not voltage-gated Ca2+ channels) activates ERK1/2 via Pyk2 tyrosine phosphorylation; response requires extracellular calcium and is blocked by suramin.\",\n      \"method\": \"Western blot for ERK/Pyk2 phosphorylation, pharmacological dissection (suramin, voltage-gated Ca2+ channel blockers), PC12 cells\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pathway placement via pharmacology, P2X2 identity inferred from pharmacological profile not direct genetic evidence\",\n      \"pmids\": [\"9685331\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"GABAA receptors and P2X2 receptors form a transient complex intracellularly that facilitates co-trafficking to the cell surface where they are located primarily extrasynaptically; P2X2 activation causes Ca2+-dependent and Ca2+-independent increases in GABAA receptor mobility and degradation, while P2X2 receptors are stabilized and form larger clusters.\",\n      \"method\": \"Co-immunoprecipitation in HEK293 cells, FRET, single particle tracking in spinal cord neurons\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — co-IP plus single particle tracking, but mechanistic details of co-trafficking not fully resolved\",\n      \"pmids\": [\"21343285\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"α6-containing nicotinic acetylcholine receptors (α6* nAChRs) directly interact with and cross-inhibit P2X2/3 receptors in DRG nociceptors; this interaction contributes to nicotine analgesia; demonstrated by physical interaction between receptors and requirement of α6* (but not α4*) nAChRs for peripheral/spinal nicotine analgesia.\",\n      \"method\": \"Gain- and loss-of-function nAChR mutants, expression genomics, DRG electrophysiology, behavioral pain models\",\n      \"journal\": \"Science Translational Medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis plus functional cross-inhibition data, but direct physical interaction method not fully detailed in abstract\",\n      \"pmids\": [\"25972004\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Carbon monoxide (CO) is a potent and selective positive modulator of P2X2 (homomeric) receptors; CO and CO-donor CORM-2 enhanced ATP-evoked P2X2 currents but caused small inhibition of P2X2/3 and P2X4 and had no effect on P2X3; the effect is independent of soluble guanylyl cyclase/cGMP pathway.\",\n      \"method\": \"Whole-cell patch-clamp in HEK293 expressing recombinant receptors and in native PC12 cells, CO donor pharmacology, guanylyl cyclase inhibition\",\n      \"journal\": \"British Journal of Pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — native cell confirmation plus recombinant characterization, mechanism of CO action on P2X2 not yet resolved at molecular level\",\n      \"pmids\": [\"19694727\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Cochlear outer sulcus cells (OSC) and vestibular transitional cells (VTC) mediate P2X2-dependent parasensory cation absorption; ATP-stimulated transepithelial current in both cell types showed P2X2 pharmacological profile (ATP>BzATP>αβmeATP potency order, blocked by suramin and gadolinium), mediating endolymph ionic homeostasis.\",\n      \"method\": \"Vibrating probe current measurement, pharmacological profiling with P2X2-selective agonist/antagonist profile\",\n      \"journal\": \"The Journal of Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological identification of P2X2-mediated function in native tissue without genetic confirmation\",\n      \"pmids\": [\"11717350\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"P2RX2 encodes an ATP-gated trimeric cation channel whose homomeric and heteromeric (P2X2/3, P2X2/6, P2X2/5) assemblies are defined by subunit-specific stoichiometries; channel gating involves intersubunit ATP binding in extracellular clefts (involving Lys69, Lys308, Arg290, Glu167), TM2 rotation/separation (gate at Asn333–Thr339, with Gly344 conferring voltage dependence), and conformational rearrangements of the cytosolic domain that drive pore dilation; desensitization kinetics are regulated by C-terminal splice variation, PKC phosphorylation of N-terminal Thr18, PKA phosphorylation of C-terminal Ser431, phosphoinositide binding to C-terminal Lys365/Lys369, and redox sensing via intracellular Cys430; the receptor is modulated by interacting proteins (VILIP1, Fe65, GABAA β-subunits, α6 nAChRs) and is required for cochlear homeostasis/hearing, enteric glial ATP signaling, and nociceptive P2X2/3-dependent pain transmission.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"P2RX2 encodes an ATP-gated cation channel that assembles as a homotrimer or as obligate heteromers with P2X3 (1:2 stoichiometry), P2X6 (2:1), or P2X5 subunits, each combination conferring distinct pharmacology and desensitization kinetics [PMID:7566120, PMID:22378790, PMID:10864944, PMID:22442090]. ATP binds at intersubunit clefts in the extracellular domain—engaging Lys69, Lys308, Arg290, and Glu167—disrupting a closed-state Glu167–Arg290 salt bridge and triggering counter-clockwise rotation and separation of TM2 helices through a gate formed by Asn333–Thr339, with Gly344 conferring voltage dependence [PMID:23041661, PMID:19906973, PMID:19114637, PMID:21576497]. Desensitization is tuned by C-terminal splice variation (P2X2a vs. P2X2b), PKC phosphorylation of N-terminal Thr18, PKA phosphorylation of C-terminal Ser431, phosphoinositide binding at Lys365/Lys369, and redox sensing via intracellular Cys430, while conformational rearrangements of the cytosolic domain drive pore dilation independently of pannexin-1 [PMID:9658396, PMID:10744703, PMID:9603227, PMID:16857707, PMID:19793987, PMID:18689682]. Dominant-negative P2RX2 mutations (p.V60L) cause progressive sensorineural hearing loss in humans, consistent with the channel's role in cochlear endolymph homeostasis and the severe hearing loss of P2rx2-null mice [PMID:23345450].\",\n  \"teleology\": [\n    {\n      \"year\": 1995,\n      \"claim\": \"Demonstration that P2X2 and P2X3 coassemble into a heteromeric ATP-gated channel in sensory neurons established the heteromerization principle for the P2X family and explained native DRG ATP currents that no single subunit could reproduce.\",\n      \"evidence\": \"Coexpression of P2X2+P2X3 in Xenopus oocytes recapitulated DRG neuron ATP current properties by voltage-clamp electrophysiology\",\n      \"pmids\": [\"7566120\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Subunit stoichiometry not determined\", \"Physical association not yet shown biochemically\", \"No structural information on assembly interface\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Cross-immunoprecipitation provided the first direct biochemical proof that P2X2 and P2X3 physically associate rather than merely coexist, and showed the heteromer has distinct desensitization properties.\",\n      \"evidence\": \"Epitope-tagged P2X2/P2X3 co-IP from baculovirus-infected insect cells plus electrophysiology\",\n      \"pmids\": [\"9254665\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry still undetermined\", \"Native tissue confirmation lacking\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Multiple regulatory axes of P2X2 were identified simultaneously: extracellular pH enhancement of ATP affinity, PKA phosphorylation of Ser431 reducing current amplitude, glycosylation requirements for surface expression, and C-terminal splice variation controlling desensitization—establishing the channel as an integrator of multiple signaling inputs.\",\n      \"evidence\": \"pH titration in oocytes (PMID:8730726, 9257926); S431C mutagenesis with PKA dialysis in HEK293 (PMID:9603227); triple N-glycosylation site mutagenesis plus tunicamycin (PMID:9778359); P2X2a/P2X2b splice variant characterization in GT1/HEK293 cells (PMID:9658396)\",\n      \"pmids\": [\"8730726\", \"9257926\", \"9603227\", \"9778359\", \"9658396\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for pH sensing unknown\", \"Whether PKA and splice regulation are independent or synergistic\", \"Relative expression of splice variants across tissues incompletely mapped\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"PKC phosphorylation of N-terminal Thr18 was identified as a second kinase-dependent desensitization switch, and P2X2/6 heteromeric channels with distinct pharmacology were functionally characterized, broadening the combinatorial diversity of P2X2-containing receptors.\",\n      \"evidence\": \"T18A/T18N mutagenesis plus phosphothreonine immunodetection in oocytes (PMID:10744703); P2X2/P2X6 coexpression pharmacology in oocytes (PMID:10864944)\",\n      \"pmids\": [\"10744703\", \"10864944\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance of PKC regulation not tested\", \"P2X2/6 stoichiometry undetermined at this point\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"The trimeric quaternary structure of homomeric P2X2 was established biochemically, and real-time FRET measurements revealed that cytosolic domain conformational rearrangements drive pore dilation—linking structure to the progressive permeability change.\",\n      \"evidence\": \"Chemical cross-linking and co-expression studies (PMID:15313628); AFM and antibody angle measurements (PMID:15657042); CFP/YFP FRET with simultaneous electrophysiology and membrane tethering rescue (PMID:15548662)\",\n      \"pmids\": [\"15313628\", \"15657042\", \"15548662\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic resolution structure not yet available\", \"Identity of cytosolic domain conformational change not resolved at residue level\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Alanine-scanning of TM1 and TM2 revealed that both transmembrane domains undergo activation-dependent conformational changes, and identified Y43A/F44A as constitutively active mutants, establishing that the pore is not a passive conduit but an actively gated structure.\",\n      \"evidence\": \"Systematic Ala-scanning mutagenesis with whole-cell patch-clamp in HEK293 cells\",\n      \"pmids\": [\"15317863\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Movement of TM1 relative to TM2 during gating not resolved\", \"No cryo-EM or crystal structure to interpret mutant phenotypes\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Zinc potentiation was localized to an intersubunit site (His120–His213 from adjacent subunits), and Fe65 was identified as a postsynaptic interacting partner that modulates P2X2 ionic selectivity changes—expanding the regulatory landscape beyond lipids and kinases.\",\n      \"evidence\": \"Concatamer and disulfide trapping approaches for zinc site (PMID:15899882); yeast two-hybrid, co-IP from brain, and immunogold EM for Fe65 (PMID:16330549)\",\n      \"pmids\": [\"15899882\", \"16330549\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Fe65 interaction domain on P2X2 not finely mapped\", \"Physiological relevance of Fe65 modulation in synaptic signaling untested\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Phosphoinositide binding at C-terminal Lys365/Lys369 was shown to regulate desensitization and pore dilation, and P2X2/3 heteromer stoichiometry (1P2X2:2P2X3) was defined by mutational rescue, resolving two long-standing questions about channel regulation and assembly.\",\n      \"evidence\": \"PI3K inhibition plus K365Q/K369Q mutagenesis plus GST pull-down (PMID:16857707); K-to-A mutagenesis rescue in coexpression (PMID:16840712)\",\n      \"pmids\": [\"16857707\", \"16840712\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PIP2 binds directly in the lipid bilayer or as a soluble headgroup unclear\", \"Stoichiometry defined functionally—structural confirmation needed\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Patch-clamp coordinated spectroscopy with tetracysteine labels demonstrated that P2X2 pore dilation (I2 state) is an intrinsic channel property driven by cytosolic domain rearrangements, ruling out pannexin-1 as the large-pore conduit, and VILIP1 was identified as a calcium-dependent signaling partner regulating P2X2 surface expression and lateral mobility.\",\n      \"evidence\": \"Biarsenical fluorophore spectroscopy with Panx1 knockout comparison (PMID:18689682); co-IP from brain, surface expression, and lateral diffusion assays (PMID:18922787)\",\n      \"pmids\": [\"18689682\", \"18922787\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of I2 state at atomic level unknown\", \"VILIP1 binding site on P2X2 not mapped\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"The TM2 gate region was precisely defined (Asn333–Thr339) with opening involving counter-clockwise helix rotation, Gly344 was identified as the structural basis for voltage-dependent gating, and Cys430 was established as an intracellular redox sensor—together providing a nearly complete gating mechanism.\",\n      \"evidence\": \"SCAM with MTSET on systematic TM2 mutants plus single-channel recording (PMID:19906973); Gly344 scanning mutagenesis with kinetic modeling (PMID:19114637); chimera/mutagenesis/alkylation convergence on Cys430 (PMID:19793987)\",\n      \"pmids\": [\"19906973\", \"19114637\", \"19793987\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No high-resolution structure of P2X2 in open vs. closed state\", \"Coupling between redox sensing and gating machinery not mechanistically detailed\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"ATP binding was localized to intersubunit clefts with fewer than three occupied sites sufficient for activation, and the Glu167–Arg290 closed-state salt bridge was shown to be disrupted by ATP binding to allow Arg290 to coordinate the γ-phosphate—completing the ligand-to-gate transduction pathway.\",\n      \"evidence\": \"Concatamers with defined binding site knockouts (PMID:22828800); charge-reversal mutagenesis, mutant cycle analysis, and state-dependent disulfide trapping (PMID:23041661); covalent ATP-analog tethering at N140/L186 (PMID:21576497); stoichiometry of P2X2/3 and P2X2/6 by binding-site mutagenesis (PMID:22378790)\",\n      \"pmids\": [\"22828800\", \"23041661\", \"21576497\", \"22378790\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No crystal or cryo-EM structure of P2X2 itself\", \"Cooperativity between binding sites not quantitatively resolved\", \"Subunit rearrangement pathway from agonist binding to gate opening not structurally visualized\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"A human P2RX2 missense mutation (p.V60L) was shown to abolish channel function in a dominant-negative fashion, and P2rx2-null mice developed progressive hearing loss, establishing P2RX2 as a deafness gene and linking its channel activity to cochlear homeostasis.\",\n      \"evidence\": \"Electrophysiology and FM1-43 uptake of V60L mutant, P2rx2-null mouse audiometry, human genetic co-segregation\",\n      \"pmids\": [\"23345450\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise mechanism by which P2X2 loss impairs cochlear function (endolymph composition vs. hair cell signaling) not resolved\", \"Genotype–phenotype correlation across different P2RX2 mutations incomplete\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"P2X2 was identified as the ATP receptor on enteric glial cells that drives p38 MAPK-dependent gliosis, cytokine release, and intestinal dysmotility, extending the channel's physiological roles beyond the nervous system and hearing.\",\n      \"evidence\": \"Genetic depletion and pharmacological antagonism (ambroxol) of P2X2, p38 MAPK pathway analysis in murine and human intestine\",\n      \"pmids\": [\"33332729\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream targets of p38 MAPK in enteric glia not fully characterized\", \"Whether P2X2 homomers or heteromers mediate enteric gliosis not determined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A high-resolution structure of P2X2 in multiple conformational states (closed, open, desensitized) has not been determined, leaving the precise atomic-level gating mechanism, the structural basis of pore dilation, and the mechanism of allosteric modulation by CO, pH, and zinc incompletely resolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No P2X2 crystal or cryo-EM structure in any state\", \"Mechanism of CO potentiation at molecular level unknown\", \"Structural basis for phosphoinositide-dependent desensitization control not visualized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 1, 14, 18, 29]},\n      {\"term_id\": \"GO:0140299\", \"supporting_discovery_ids\": [30]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [6, 25, 33, 37]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 23, 26]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [35, 36]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [14, 18, 29]},\n      {\"term_id\": \"R-HSA-9709957\", \"supporting_discovery_ids\": [32, 40]}\n    ],\n    \"complexes\": [\n      \"P2X2 homotrimer\",\n      \"P2X2/3 heteromer (1:2)\",\n      \"P2X2/6 heteromer (2:1)\",\n      \"P2X2/5 heteromer\"\n    ],\n    \"partners\": [\n      \"P2RX3\",\n      \"P2RX6\",\n      \"P2RX5\",\n      \"VSNL1\",\n      \"APBB1\",\n      \"GABRB3\",\n      \"CHRNA6\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}