{"gene":"ASIC2","run_date":"2026-06-09T22:02:44","timeline":{"discoveries":[{"year":1996,"finding":"MDEG (ASIC2) is an amiloride-sensitive cation channel permeable for Na+, K+, and Li+. Gain-of-function mutations homologous to those causing neurodegeneration in C. elegans constitutively activate the channel and cause cell death in mammalian cells, indicating the channel's ion-conducting activity underlies its cytotoxic effects.","method":"Electrophysiology (Xenopus oocyte expression), gain-of-function mutagenesis, cell death assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct electrophysiological characterization with mutagenesis showing constitutive activation causes cell death; foundational study replicated across the field","pmids":["8631835"],"is_preprint":false},{"year":1997,"finding":"BNaC1 (ASIC2) and BNaC2 form a new branch of the DEG/ENaC superfamily. Both genes are co-expressed in most brain neurons throughout life, consistent with assembly into heteromultimeric channels.","method":"cDNA cloning, Northern blot, in situ hybridization, chromosomal mapping (17q11.2-12)","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — foundational cloning and expression study; heteromultimerization proposed but not yet experimentally confirmed in this paper","pmids":["9037075"],"is_preprint":false},{"year":2000,"finding":"ASIC2a and ASIC3 subunits co-assemble into functional heteromeric proton-gated channels with greatly amplified acid-induced currents (up to 20-fold larger than homomers), a cation current selective for sodium, and increased sensitivity to gadolinium (IC50 ~40 µM vs. ≥1 mM for ASIC2a alone). Biochemical co-purification from HEK293 cells and Xenopus oocytes confirmed direct physical interaction.","method":"Xenopus oocyte electrophysiology, co-immunoprecipitation/co-purification from HEK293 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-purification plus functional electrophysiology with multiple orthogonal methods","pmids":["10842183"],"is_preprint":false},{"year":2001,"finding":"PICK1 (a PDZ domain protein) interacts specifically with BNaC1/ASIC2 via the PDZ domain of PICK1 and the last four amino acids of ASIC2. Co-expression of both proteins leads to their clustering in intracellular compartments. PICK1 co-localizes with ASIC2 at peripheral mechanosensory nerve endings of DRG neurons and in dendrites of central neurons.","method":"Yeast two-hybrid screen, GST pull-down, co-immunoprecipitation, immunohistochemistry, subcellular localization imaging","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal biochemical methods (yeast two-hybrid, GST pull-down, co-IP) plus in vivo localization; single lab but comprehensive","pmids":["11739374"],"is_preprint":false},{"year":2002,"finding":"PKC potentiates ASIC2a current amplitude (~300%) when PICK1 is co-expressed, requiring both the PDZ domain of PICK1 and the PDZ-binding domain of ASIC2a. Direct PICK1-dependent phosphorylation of ASIC2a was demonstrated by 32P-labeling and immunoprecipitation; the major phosphorylation site was identified as Thr39 (TIR motif) in the N-terminus. PKC potentiation did not alter ASIC2a unitary conductance.","method":"Electrophysiology (whole-cell patch clamp), 32P phosphorylation labeling, co-immunoprecipitation, site-directed mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct phosphorylation demonstrated by radiolabeling with phosphosite identified by mutagenesis, combined with electrophysiology; multiple orthogonal methods","pmids":["12399460"],"is_preprint":false},{"year":2003,"finding":"ASIC2b (an N-terminal splice variant of ASIC2a from the same gene) co-assembles with ASIC2a to form heteromeric channels in taste cells. The ASIC2a/ASIC2b heteromeric channel generates maximal inward currents at pH ≤2.0, and amiloride sensitivity is almost abolished at pH 2.0, distinguishing it from ASIC2a homomers.","method":"Co-immunoprecipitation from circumvallate papillae, Xenopus oocyte electrophysiology, immunohistochemistry","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — native tissue co-IP plus functional electrophysiology characterizing heteromeric channel properties","pmids":["12736332"],"is_preprint":false},{"year":2004,"finding":"ASIC2 and ASIC3 null mutations do not alter mechanically activated current amplitude or kinetics in DRG neuron cell bodies, indicating that ASIC2 is not a direct transducer of mechanical stimuli at the soma level.","method":"Whole-cell patch clamp of cultured DRG neurons from ASIC2-/- and ASIC3-/- knockout mice","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct electrophysiology in knockout neurons; rigorous negative result independently supported by the ASIC2 KO paper (PMID 15169849)","pmids":["14990679"],"is_preprint":false},{"year":2004,"finding":"ASIC2 knockout mice show no impairment of cutaneous mechanosensation, visceral mechanonociception, or hearing, arguing against ASIC2 being an essential direct mechanotransducer in these modalities.","method":"Behavioral mechanosensation assays, auditory brainstem response, in vivo nerve recordings in ASIC2-/- mice","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — rigorous in vivo knockout study with multiple mechanosensory readouts; negative result for direct mechanotransducer role","pmids":["15169849"],"is_preprint":false},{"year":2005,"finding":"ASIC2 protein expression in medium/large DRG neurons is maintained by BDNF signaling: ASIC2 mRNA and protein are dramatically down-regulated in BDNF-deficient mice, and exogenous BDNF (10–100 ng/ml) rescues ASIC2 expression in a dose- and time-dependent manner that requires new transcription and protein synthesis.","method":"Immunocytochemistry, RT-PCR, pharmacological block of transcription/translation, BDNF-deficient mouse DRG cultures","journal":"Neuroscience","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — multiple methods (immunostaining, mRNA, KO mice, pharmacological rescue) but no direct signaling mechanism established","pmids":["15708491"],"is_preprint":false},{"year":2006,"finding":"ASIC2 is retained intracellularly in high-grade glioma cells; forcing its surface expression (via glycerol or sodium 4-phenylbutyrate) abolishes the constitutively active amiloride-sensitive inward Na+ current and reduces glioma cell growth and migration, indicating ASIC2 exerts negative regulation of this ENaC/DEG-mediated conductance when present at the plasma membrane.","method":"Electrophysiology (whole-cell patch clamp), cell migration assays, surface biotinylation, chemical chaperone treatment","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — electrophysiology plus functional migration/growth assays; single lab, mechanistic pharmacological intervention","pmids":["16704974"],"is_preprint":false},{"year":2007,"finding":"AKAP150 and the protein phosphatase calcineurin bind to ASIC2a (and ASIC1a) as demonstrated by pulldown and mass spectrometry followed by co-immunoprecipitation. Inhibiting PKA-AKAP150 interaction (Ht-31 peptide) reduces ASIC currents, while inhibiting calcineurin (cyclosporin A) increases ASIC currents, indicating that calcineurin-dependent dephosphorylation tonically inhibits ASIC2a activity.","method":"GST pulldown, mass spectrometry, co-immunoprecipitation, whole-cell patch clamp in cortical neurons and CHO cells, pharmacological inhibition","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — mass spec identification confirmed by co-IP, functional validation with two independent pharmacological tools in neurons and heterologous cells","pmids":["17548344"],"is_preprint":false},{"year":2007,"finding":"Five specific protonatable residues in the extracellular loop of ASIC2a are required for proton-gated activation; mutating any one of these sites abolishes acid sensitivity while the channels still traffic normally to the cell surface and retain the capacity to form functional heteromers.","method":"Site-directed mutagenesis, immunocytochemistry (surface trafficking), whole-cell patch clamp electrophysiology","journal":"Neuroscience letters","confidence":"High","confidence_rationale":"Tier 1 / Moderate — site-directed mutagenesis with functional electrophysiology and trafficking controls; single lab but rigorous mechanistic dissection","pmids":["17881127"],"is_preprint":false},{"year":2007,"finding":"Hsc70 co-immunoprecipitates with ASIC2 and is overexpressed in glioma cells versus normal astrocytes. Hsc70 siRNA knockdown inhibits the constitutive amiloride-sensitive current, decreases glioma migration, and increases ASIC2 surface expression, demonstrating that Hsc70 retains ASIC2 in the ER of glioma cells.","method":"Co-immunoprecipitation, siRNA knockdown, electrophysiology, cell migration assay, surface biotinylation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP plus siRNA knockdown with multiple functional readouts; single lab with orthogonal methods","pmids":["17878160"],"is_preprint":false},{"year":2008,"finding":"Hsc70 inhibits ASIC2 surface expression in vascular smooth muscle cells (VSMCs). Hsc70 silencing increases ASIC2 cell surface expression and inhibits VSMC migration; co-silencing of ASIC2 abolishes this effect, placing ASIC2 downstream of Hsc70 in regulating VSMC migration.","method":"siRNA knockdown, surface expression assay, VSMC migration (chemotaxis) assay","journal":"American journal of physiology. Heart and circulatory physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional epistasis by co-silencing with migration readout; single lab","pmids":["18310515"],"is_preprint":false},{"year":2008,"finding":"Pressure-induced (myogenic) constriction in mouse middle cerebral arteries is impaired in ASIC2-/- and ASIC2+/- mice, while constriction to KCl and phenylephrine is unaffected, demonstrating that normal ASIC2 expression is required for the myogenic response in cerebral arteries.","method":"Pressure myography on isolated middle cerebral arteries from ASIC2 knockout mice","journal":"American journal of physiology. Heart and circulatory physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — well-controlled in vitro vascular preparation with genetic knockout; single lab","pmids":["18296560"],"is_preprint":false},{"year":2009,"finding":"ASIC2a and ASIC3 are the principal ASIC subunits in cardiac dorsal root ganglia afferents. In ASIC3-/- cardiac afferents, currents match ASIC2a homomeric properties; in ASIC2-/- afferents, currents match ASIC3 homomeric properties; currents are absent in ASIC2/3 double knockouts, establishing that ASIC2a and ASIC3 heteromultimerize to form the predominant channels in cardiac DRG neurons.","method":"Retrograde labeling, patch-clamp electrophysiology in ASIC-null mice (ASIC2-/-, ASIC3-/-, double KO)","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis using multiple knockout combinations with direct electrophysiological readout","pmids":["19590043"],"is_preprint":false},{"year":2012,"finding":"Triple knockout of ASIC1a, ASIC2, and ASIC3 increases cutaneous mechanosensitivity (enhanced A-mechanonociceptor responses), the opposite of what would be expected if ASICs directly transduce mechanical stimuli, suggesting ASICs modulate rather than directly mediate cutaneous mechanotransduction.","method":"Behavioral von Frey assays, single-fiber nerve recordings in triple ASIC knockout mice","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo genetic and electrophysiological analysis; single lab but multi-modal readout","pmids":["22506072"],"is_preprint":false},{"year":2012,"finding":"ASIC1a, ASIC2a, and ASIC3 heteromultimerize to form the principal acid-sensing channels in skeletal muscle afferents. Deletion of ASIC2 selectively abolishes zinc potentiation of acid-evoked currents in muscle afferents, and currents are absent in triple-null mice, establishing the subunit composition of native muscle afferent ASICs.","method":"Patch-clamp electrophysiology in labeled muscle afferents from ASIC-null mice, pharmacological profiling (zinc potentiation)","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple genetic knockout combinations with pharmacological subunit fingerprinting","pmids":["23109675"],"is_preprint":false},{"year":2012,"finding":"Hyperactivation of MDEG/ASIC2 (G430F mutant) causes intracellular Ca2+ overload and ROS production leading to inhibition of proteasomal and autophagic degradation, accumulation of protein aggregates containing caspase-8, and subsequent caspase-8-dependent apoptosis. This pathway is independent of Bax/Bak but dependent on p62 and LC3.","method":"Tetracycline-inducible expression system, calcium imaging, ROS measurement, flow cytometry apoptosis assay, caspase activity assay, siRNA knockdown of p62 and LC3","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — mechanistic pathway dissected with inducible gain-of-function, calcium chelation, ROS scavenging, caspase inhibition, and siRNA knockdown; multiple orthogonal methods","pmids":["23239879"],"is_preprint":false},{"year":2013,"finding":"ASIC2 is expressed in brain regions of high synaptic density and co-localizes with ASIC1. Loss of ASIC2 decreases freezing behavior in contextual and auditory fear conditioning, predator odor, and CO2 inhalation assays, and increases activity in forced swim, demonstrating that ASIC2 modulates defensive responses to aversive stimuli in vivo.","method":"Immunohistochemistry, behavioral assays (fear conditioning, predator odor, CO2, forced swim) in ASIC2-/- mice","journal":"Genes, brain, and behavior","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined behavioral phenotypes in KO mice with anatomical localization; single lab","pmids":["24256442"],"is_preprint":false},{"year":2014,"finding":"ASIC2 subunits increase cell surface expression of ASIC1a-containing channels when co-expressed, and genetic deletion of ASIC2 reduces acid-evoked current amplitude in hippocampal neurons. ASIC2a interacts with PSD-95, and PSD-95 reduces ASIC2a surface expression and current amplitude; this effect requires ASIC2 (absent in ASIC2-/- neurons).","method":"Surface biotinylation, patch-clamp electrophysiology in ASIC2-/- hippocampal neurons, co-immunoprecipitation, PSD-95 overexpression","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — co-IP plus surface expression plus electrophysiology in native neurons with genetic KO confirmation; multiple orthogonal methods","pmids":["24699665"],"is_preprint":false},{"year":2016,"finding":"ASIC2 deletion reduces acid-activated current in cortical and striatal neurons but not cerebellar granule neurons (region-specific effect). ASIC2a (but not ASIC2b) facilitates ASIC1a surface trafficking in the brain, and ASIC2 is important for ASIC1a expression levels. ASIC2 deletion reduces ischemia-induced neuronal injury in cortex/hippocampus but not cerebellum, and protects mouse brain from ischemic damage in vivo.","method":"Whole-cell patch clamp in neurons from ASIC2-/- mice, surface biotinylation, organotypic slice injury assays, in vivo MCAO stroke model","journal":"Journal of cerebral blood flow and metabolism","confidence":"High","confidence_rationale":"Tier 2 / Strong — electrophysiology, biochemistry, and in vivo stroke model with genetic KO; multiple orthogonal methods in single study","pmids":["26861816"],"is_preprint":false},{"year":2016,"finding":"Two di-leucine (LL) motifs in the C-terminal juxtamembrane region of ASIC2a act as negative regulators of trafficking: mutating either LL motif increases total and surface ASIC2a expression, enhances dendritic and dendritic spine targeting in hippocampal neurons, increases acid-activated current density, and mutating the second LL motif also increases pH sensitivity.","method":"Site-directed mutagenesis, surface biotinylation, electrophysiology, immunofluorescence imaging in organotypic hippocampal slices","journal":"Molecular brain","confidence":"High","confidence_rationale":"Tier 1 / Strong — mutagenesis with multiple functional readouts (trafficking, electrophysiology, subcellular localization) in heterologous and neuronal systems","pmids":["26819004"],"is_preprint":false},{"year":2016,"finding":"ASIC2a facilitates surface trafficking of ASIC3 via heteromeric assembly; ASIC3 mostly accumulates in the ER alone but is delivered to the plasma membrane when co-expressed with ASIC2a, confirmed by BiFC assay. ASIC2a-dependent ASIC3 surface expression enhances the sustained component of acid-evoked currents.","method":"Surface biotinylation, bimolecular fluorescence complementation (BiFC), electrophysiology in heterologous cells","journal":"BMB reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — BiFC plus surface expression plus electrophysiology; single lab, heterologous system","pmids":["27241858"],"is_preprint":false},{"year":2016,"finding":"ASIC2a promotes surface trafficking of ASIC2b via heteromeric assembly. The first transmembrane domain and proximal post-TM1 region (17 amino acids) of ASIC2a are critical for membrane targeting. Replacing corresponding ASIC2b residues with those of ASIC2a confers both proton sensitivity and surface expression to ASIC2b.","method":"Chimeric channel construction, surface biotinylation, electrophysiology in heterologous cells","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — domain-swap mutagenesis with functional validation; single lab, heterologous system only","pmids":["27477936"],"is_preprint":false},{"year":2017,"finding":"ASIC2 activates the calcineurin/NFAT1 signaling pathway under acidosis in colorectal cancer cells, promoting invasion and metastasis. Inhibition of calcineurin/NFAT with cyclosporin A blocks ASIC2-induced invasion. ChIP-seq of NFAT1 identified downstream target genes in Rho GTPase and calcium signaling pathways.","method":"Gene overexpression/knockdown, matrigel invasion assay, in vivo xenograft/metastasis models, calcineurin inhibitor pharmacology, ChIP-seq","journal":"Journal of experimental & clinical cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro and in vivo functional assays with pharmacological pathway inhibition and ChIP-seq; single lab","pmids":["28927426"],"is_preprint":false},{"year":2018,"finding":"Psalmotoxin 1 (PcTx1) has dual actions at ASIC1a/ASIC2a heteromeric channels: potent inhibition at desensitizing conditioning pH (IC50=2.9 nM at pH 7.0), and potent potentiation at physiological pH (EC50=56.1 nM in CHO cells; threshold <10 nM in cortical neurons) by increasing channel apparent proton affinity for activation.","method":"Whole-cell patch clamp in CHO cells and cortical neurons, concentration-response analysis","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct electrophysiology with quantitative pharmacology in two cell systems; single lab","pmids":["29739981"],"is_preprint":false},{"year":2019,"finding":"Three N-terminal residues of ASIC2a (T25, T39, and I40) determine rapid resensitization: mutating these residues causes prolonged desensitization (phenocopying ASIC2b) in homomeric and heteromeric channels. This desensitization is not due to channel internalization or degradation.","method":"Site-directed mutagenesis, domain-swapping chimeras, whole-cell patch clamp, internalization assays","journal":"The Journal of general physiology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mutagenesis identifying specific residues with functional electrophysiology and mechanistic controls; single lab but rigorous","pmids":["31010811"],"is_preprint":false},{"year":2019,"finding":"Nocistatin, an endogenous neuropeptide, is a direct agonist of ASIC2a (as well as ASIC1a, ASIC1b, ASIC3), evoking proton-like currents in Xenopus oocytes; the mambalgin-2 antagonist (ASIC1a blocker) inhibits nocistatin-induced currents, suggesting a similar activation mechanism to protons.","method":"Xenopus oocyte electrophysiology, pharmacological characterization with peptide toxins","journal":"Biomolecules","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct electrophysiological activation assay with pharmacological controls; single lab, heterologous expression","pmids":["31443477"],"is_preprint":false},{"year":2020,"finding":"Ion selectivity in ASIC2a-containing channels is determined differently from ASIC1a: E18' residues at the lower pore are conserved and create energetic preference for Na+ in ASIC2a, but the L7' residues (critical in ASIC1a) do not determine ion permeation in ASIC2a. Instead, ASIC2a-specific negatively charged residues E59 and E62 in the upper pore compensate, making the GAS belt more important for selectivity.","method":"Site-directed mutagenesis, whole-cell electrophysiology, molecular dynamics free energy simulations","journal":"The Journal of general physiology","confidence":"High","confidence_rationale":"Tier 1 / Strong — mutagenesis combined with molecular dynamics simulations and electrophysiology with multiple residues systematically tested","pmids":["31952079"],"is_preprint":false},{"year":2021,"finding":"A truncated variant of ASIC2b, whose expression in kidney tubules is induced by luminal albumin and ERK activation, produces sustained acid-stimulated sodium currents when co-expressed with ASIC2a. ASIC2b-null rats in a corticosteroid-clamped nephrotic model do not develop sodium retention, establishing this ASIC2b variant as the mediator of renal Na+ retention in nephrotic syndrome.","method":"Xenopus oocyte electrophysiology, ASIC2b-null rat model, renal function measurements, ERK signaling analysis","journal":"JCI insight","confidence":"High","confidence_rationale":"Tier 2 / Strong — functional electrophysiology plus genetic knockout rat model plus upstream signaling mechanism; multiple orthogonal methods","pmids":["34166227"],"is_preprint":false},{"year":2021,"finding":"ASIC2 and TRPV1 co-localize in aortic baroreceptor nerve endings and form a physical complex confirmed by co-immunoprecipitation and biotin pull-down. In HEK293T cells co-expressing both proteins, inhibition of ASIC2 (but not TRPV1) completely blocks stretch-activated currents, indicating ASIC2 is required upstream of TRPV1 in baroreceptor mechanotransduction.","method":"Co-immunoprecipitation, biotin pull-down, cell-attached patch clamp in HEK293T cells, aortic arch nerve recording, immunofluorescence","journal":"Neuroscience bulletin","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, pull-down, and functional electrophysiology; single lab, includes heterologous expression","pmids":["34215968"],"is_preprint":false},{"year":2022,"finding":"βENaC and ASIC2 form biochemical complexes in vascular smooth muscle cells (co-immunoprecipitation). In renal afferent arterioles, pressure-induced constriction is abolished in ASIC2-/-/βENaCm/m double-mutant mice but only partially impaired in single mutants, demonstrating that βENaC and ASIC2 interact functionally and are jointly required for the full myogenic response.","method":"Co-immunoprecipitation from VSMCs, isolated afferent arteriole-attached glomerulus pressure myography in single and double KO mice","journal":"American journal of physiology. Renal physiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP plus genetic epistasis with double KO in ex vivo vascular preparation; multiple orthogonal approaches","pmids":["35285274"],"is_preprint":false},{"year":2023,"finding":"ASIC2 is expressed in proprioceptive sensory neurons. Asic2 loss-of-function mice display impaired muscle spindle responses to stretch and deficits in motor coordination tasks. Analysis of skeletons revealed specific effects on spinal alignment, identifying ASIC2 as a component of proprioceptive sensing.","method":"In vivo proprioception behavioral tests, ex vivo muscle spindle electrophysiology, skeletal analysis in Asic2 KO mice","journal":"Experimental physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo and ex vivo functional tests in KO mice with electrophysiological validation; single lab","pmids":["36951012"],"is_preprint":false},{"year":2023,"finding":"ASIC2A (but not ASIC2B) is the predominant ASIC2 subunit in nucleus accumbens core. Recombinant ASIC2A expressed via AAV integrates with endogenous ASIC1A to form functional channels in medium spiny neurons. Loss of ASIC2 alters dendritic spine morphology and increases conditioned place preference to cocaine and morphine, but region-restricted ASIC2A restoration in nucleus accumbens core is insufficient to rescue cocaine/morphine preference.","method":"Western blot, AAV-mediated in vivo rescue, patch-clamp electrophysiology in MSNs, conditioned place preference, dendritic spine morphology analysis","journal":"Frontiers in molecular biosciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo rescue with electrophysiological confirmation of heteromeric assembly; single lab, multiple readouts","pmids":["36793786"],"is_preprint":false}],"current_model":"ASIC2 (BNaC1/MDEG) is a proton-gated, amiloride-sensitive Na+-selective cation channel of the DEG/ENaC superfamily that obligately forms homotrimeric or heterotrimeric complexes with ASIC1a, ASIC2b, ASIC3, and βENaC; its subunit composition determines pH sensitivity, ion selectivity (governed by conserved E18' and ASIC2a-specific E59/E62 in the pore), and pharmacology; its trafficking to the plasma membrane is negatively regulated by di-leucine motifs in its C-terminal juxtamembrane region and by Hsc70-mediated ER retention, and positively promoted by ASIC2a's TM1 domain enabling co-assembly with ASIC2b and ASIC3; its activity is dynamically regulated by PKC-dependent phosphorylation at T39 via the PDZ scaffold PICK1, and by calcineurin-dependent dephosphorylation anchored by AKAP150; ASIC2 forms physical complexes with PSD-95 (reducing surface expression), TRPV1 (baroreceptor mechanotransduction), and βENaC (renal/cerebrovascular myogenic constriction); endogenous nocistatin directly activates ASIC2a; hyperactivation of ASIC2/MDEG causes Ca2+-overload-driven caspase-8 apoptosis via p62/LC3-dependent protein aggregate formation; and at the systems level ASIC2 is required for proprioceptive muscle spindle responses, modulation of fear/aversive behaviors, renal sodium retention in nephrotic syndrome (via a truncated ASIC2b variant), and normal myogenic vasoconstriction in cerebral and renal vessels."},"narrative":{"mechanistic_narrative":"ASIC2 (MDEG/BNaC1) is a proton-gated, amiloride-sensitive cation channel of the DEG/ENaC superfamily whose ion-conducting activity, when constitutively activated by gain-of-function mutation, is directly cytotoxic [PMID:8631835]. Proton gating depends on a set of protonatable residues in the extracellular loop, and mutating any one abolishes acid sensitivity without disrupting surface trafficking or heteromer formation [PMID:17881127]; Na+ selectivity is set by a conserved lower-pore E18' acidic residue working together with ASIC2a-specific upper-pore residues E59/E62, distinguishing the basis of selectivity from ASIC1a [PMID:31952079]. ASIC2 functions principally as a modulatory subunit that co-assembles into heteromeric channels with ASIC2b, ASIC3, and ASIC1a, with subunit composition dictating current amplitude, pH dependence, desensitization kinetics, and pharmacology [PMID:10842183, PMID:12736332, PMID:19590043, PMID:23109675]; ASIC2a's first transmembrane domain and proximal post-TM1 region drive both its own membrane targeting and the surface delivery of partner subunits ASIC2b, ASIC3, and ASIC1a [PMID:27477936, PMID:27241858, PMID:26861816]. Surface expression is held in check by C-terminal di-leucine motifs [PMID:26819004], by Hsc70-mediated ER retention [PMID:17878160], and by PSD-95 binding [PMID:24699665], while channel activity is dynamically tuned by PICK1-anchored PKC phosphorylation at Thr39 [PMID:11739374, PMID:12399460] and by AKAP150-anchored calcineurin dephosphorylation [PMID:17548344]. Through these heteromers ASIC2 contributes to acid sensing in sensory afferents and the brain rather than acting as a direct mechanotransducer, since cutaneous mechanosensation, hearing, and somatic mechanically activated currents are intact or even enhanced in ASIC2-null animals [PMID:14990679, PMID:15169849, PMID:22506072]. At the systems level ASIC2 is required for proprioceptive muscle spindle responses [PMID:36951012], modulates fear and aversive behaviors [PMID:24256442], supports myogenic vasoconstriction in cerebral and renal vessels jointly with βENaC [PMID:18296560, PMID:35285274], contributes to ischemic neuronal injury [PMID:26861816], and, via an albumin/ERK-induced truncated ASIC2b variant, mediates renal sodium retention in nephrotic syndrome [PMID:34166227]. Hyperactivation drives Ca2+ overload and ROS that block proteasomal/autophagic degradation, producing p62/LC3-dependent aggregates and caspase-8 apoptosis [PMID:23239879].","teleology":[{"year":1996,"claim":"Established that ASIC2/MDEG is an ion-conducting amiloride-sensitive cation channel and that its conductance itself can be cytotoxic, linking channel activity to neurodegeneration.","evidence":"Electrophysiology in Xenopus oocytes with gain-of-function mutagenesis and cell death assays","pmids":["8631835"],"confidence":"High","gaps":["Did not establish physiological gating stimulus","Native subunit partners unknown","No structural basis for ion conduction"]},{"year":1997,"claim":"Defined ASIC2 as a brain-expressed member of a new DEG/ENaC branch co-expressed with a related subunit, raising the possibility of heteromeric channels.","evidence":"cDNA cloning, Northern blot, in situ hybridization, chromosomal mapping","pmids":["9037075"],"confidence":"Medium","gaps":["Heteromultimerization proposed but not demonstrated","Functional channel properties not characterized"]},{"year":2000,"claim":"Showed that ASIC2 is a partner subunit whose co-assembly reshapes channel function, demonstrating direct heteromerization with ASIC3.","evidence":"Co-purification from HEK293 cells and oocyte electrophysiology","pmids":["10842183"],"confidence":"High","gaps":["Stoichiometry of heteromer not resolved","Physiological context of ASIC2a/ASIC3 channels not established"]},{"year":2001,"claim":"Identified PICK1 as a direct PDZ-domain partner of the ASIC2 C-terminus that clusters the channel, providing a scaffold linking ASIC2 to regulatory machinery.","evidence":"Yeast two-hybrid, GST pull-down, co-IP, and immunohistochemistry in DRG and central neurons","pmids":["11739374"],"confidence":"High","gaps":["Functional consequence of clustering not yet shown","Did not establish phosphorylation regulation"]},{"year":2002,"claim":"Connected the PICK1 scaffold to functional regulation, showing PKC potentiates ASIC2a current via direct phosphorylation at Thr39.","evidence":"Whole-cell patch clamp, 32P labeling, co-IP, and site-directed mutagenesis","pmids":["12399460"],"confidence":"High","gaps":["Upstream signals activating PKC at the channel unknown","Did not address dephosphorylation"]},{"year":2003,"claim":"Demonstrated that the ASIC2b splice variant co-assembles with ASIC2a to produce channels with distinct extreme-acid responsiveness, expanding the functional repertoire from one gene.","evidence":"Native co-IP from taste tissue and oocyte electrophysiology","pmids":["12736332"],"confidence":"High","gaps":["Trafficking determinants of the heteromer not defined","Physiological role in taste not established"]},{"year":2004,"claim":"Resolved whether ASIC2 is a direct somatic mechanotransducer; knockout neurons and mice retained normal mechanically activated currents and mechanosensation, arguing against a direct transducer role.","evidence":"Patch clamp of knockout DRG neurons and in vivo mechanosensation/auditory assays in ASIC2-/- mice","pmids":["14990679","15169849"],"confidence":"High","gaps":["Did not exclude modulatory mechanosensory roles in specialized endings","Compensation by other ASICs not assessed"]},{"year":2005,"claim":"Showed ASIC2 expression in DRG neurons is maintained by BDNF, identifying a transcriptional/trophic input controlling channel abundance.","evidence":"Immunocytochemistry, RT-PCR, and pharmacological rescue in BDNF-deficient mouse DRG cultures","pmids":["15708491"],"confidence":"Medium","gaps":["Direct signaling pathway from BDNF to ASIC2 transcription not defined","Functional channel consequence not measured"]},{"year":2006,"claim":"Revealed regulated intracellular retention of ASIC2 in glioma and that forced surface expression suppresses a constitutive Na+ conductance and tumor cell migration/growth, indicating negative regulation at the membrane.","evidence":"Patch clamp, migration assays, surface biotinylation, and chemical chaperone treatment","pmids":["16704974"],"confidence":"Medium","gaps":["Identity of the retention machinery not yet defined here","Molecular basis of suppression of conductance unclear"]},{"year":2007,"claim":"Identified Hsc70 as the ER-retention factor for ASIC2 in glioma, mechanistically explaining intracellular sequestration and its link to migration.","evidence":"Co-IP, siRNA knockdown, electrophysiology, migration assay, and surface biotinylation","pmids":["17878160"],"confidence":"High","gaps":["Whether Hsc70 retention is selective for specific ASIC2 conformers unknown","Generalizability beyond glioma not addressed here"]},{"year":2007,"claim":"Mapped the proton-sensing apparatus to five extracellular protonatable residues required for gating but dispensable for trafficking and heteromerization.","evidence":"Site-directed mutagenesis with surface trafficking imaging and patch clamp","pmids":["17881127"],"confidence":"High","gaps":["Conformational mechanism coupling protonation to gating not resolved","No structural model"]},{"year":2007,"claim":"Defined a phosphatase arm of ASIC2 regulation, showing AKAP150 anchors calcineurin to tonically dephosphorylate and inhibit the channel, complementing PKC potentiation.","evidence":"GST pulldown, mass spec, co-IP, and pharmacological modulation in cortical neurons and CHO cells","pmids":["17548344"],"confidence":"High","gaps":["Specific dephosphorylation site not mapped","Integration with PICK1/PKC at single channels unresolved"]},{"year":2008,"claim":"Extended Hsc70-dependent retention of ASIC2 to vascular smooth muscle, placing ASIC2 downstream of Hsc70 in controlling VSMC migration.","evidence":"siRNA knockdown with co-silencing epistasis and migration assays in VSMCs","pmids":["18310515"],"confidence":"Medium","gaps":["Channel activity required for migration not directly demonstrated","Single-lab functional epistasis"]},{"year":2008,"claim":"Linked ASIC2 to vascular physiology, showing it is required for pressure-induced myogenic constriction of cerebral arteries.","evidence":"Pressure myography on cerebral arteries from ASIC2 knockout mice","pmids":["18296560"],"confidence":"Medium","gaps":["Molecular partners in VSMC mechanosensing not identified here","Whether ASIC2 senses pressure directly unknown"]},{"year":2009,"claim":"Established native ASIC2a/ASIC3 heteromers as the predominant acid-sensing channels in cardiac afferents using genetic epistasis.","evidence":"Retrograde labeling and patch clamp across ASIC2-/-, ASIC3-/-, and double-KO mice","pmids":["19590043"],"confidence":"High","gaps":["Functional role in cardiac afferent signaling in vivo not measured here","Stoichiometry not determined"]},{"year":2012,"claim":"Defined the subunit composition of muscle afferent ASICs as ASIC1a/ASIC2a/ASIC3 heteromers, with ASIC2 specifically conferring zinc potentiation.","evidence":"Patch clamp with pharmacological fingerprinting in muscle afferents from ASIC-null mice","pmids":["23109675"],"confidence":"High","gaps":["Functional consequence of zinc potentiation in vivo unknown"]},{"year":2012,"claim":"Showed ASICs modulate rather than directly mediate cutaneous mechanotransduction, since triple knockout enhanced rather than abolished mechanonociceptor responses.","evidence":"von Frey assays and single-fiber recordings in triple ASIC knockout mice","pmids":["22506072"],"confidence":"Medium","gaps":["Mechanism of modulation unresolved","ASIC2-specific contribution not isolated"]},{"year":2012,"claim":"Dissected the cytotoxic pathway of hyperactivated ASIC2, showing Ca2+/ROS-driven degradation blockade produces p62/LC3-dependent aggregates and caspase-8 apoptosis independent of Bax/Bak.","evidence":"Inducible G430F expression with calcium imaging, ROS measurement, apoptosis/caspase assays, and p62/LC3 siRNA","pmids":["23239879"],"confidence":"High","gaps":["Relevance to physiological ASIC2 activation unclear","Trigger for aggregate formation not fully defined"]},{"year":2014,"claim":"Established ASIC2 as a brain channel that boosts ASIC1a surface expression and acid-evoked currents, with PSD-95 acting as a negative regulator of surface ASIC2a.","evidence":"Surface biotinylation, patch clamp in ASIC2-/- hippocampal neurons, co-IP, and PSD-95 overexpression","pmids":["24699665"],"confidence":"High","gaps":["Mechanism by which PSD-95 reduces surface expression not defined","Interplay with PICK1 scaffolding unresolved"]},{"year":2016,"claim":"Showed ASIC2a is a chaperone-like trafficking subunit that delivers ASIC1a, ASIC3, and ASIC2b to the membrane, and identified its TM1/post-TM1 region as the membrane-targeting determinant.","evidence":"Surface biotinylation, BiFC, chimeric domain swaps, and electrophysiology in heterologous cells and neurons","pmids":["26861816","27241858","27477936"],"confidence":"Medium","gaps":["Trafficking machinery engaged by TM1 not identified","Largely heterologous systems for ASIC3/ASIC2b"]},{"year":2016,"claim":"Identified two C-terminal di-leucine motifs as autonomous negative regulators of ASIC2a trafficking, surface density, dendritic targeting, and pH sensitivity.","evidence":"Mutagenesis with surface biotinylation, electrophysiology, and imaging in hippocampal slices","pmids":["26819004"],"confidence":"High","gaps":["Adaptor proteins recognizing the di-leucine motifs not identified"]},{"year":2016,"claim":"Linked ASIC2 trafficking function to ischemic injury, showing ASIC2a facilitates ASIC1a surface delivery and that ASIC2 deletion protects brain regions from ischemic damage region-specifically.","evidence":"Patch clamp, biotinylation, organotypic slice injury, and in vivo MCAO stroke model in ASIC2-/- mice","pmids":["26861816"],"confidence":"High","gaps":["Region-specificity mechanism unresolved","Relative contribution of ASIC2 vs ASIC1a to injury not separated"]},{"year":2017,"claim":"Connected ASIC2 to a downstream transcriptional program, showing acidosis-driven ASIC2 activates calcineurin/NFAT1 to promote colorectal cancer invasion.","evidence":"Overexpression/knockdown, invasion and metastasis models, calcineurin inhibition, and NFAT1 ChIP-seq","pmids":["28927426"],"confidence":"Medium","gaps":["Direct coupling of channel conductance to calcineurin activation not demonstrated","Single-lab"]},{"year":2018,"claim":"Characterized dual modulation of ASIC1a/ASIC2a heteromers by PcTx1, inhibiting under desensitizing pH and potentiating at physiological pH by increasing proton affinity.","evidence":"Concentration-response patch clamp in CHO cells and cortical neurons","pmids":["29739981"],"confidence":"Medium","gaps":["Toxin binding site on ASIC2a-containing heteromers not mapped"]},{"year":2019,"claim":"Identified three N-terminal ASIC2a residues (T25, T39, I40) that confer rapid resensitization, explaining a key kinetic difference from ASIC2b independent of internalization.","evidence":"Site-directed mutagenesis, domain-swap chimeras, patch clamp, and internalization assays","pmids":["31010811"],"confidence":"High","gaps":["Structural mechanism of N-terminal control of gating unresolved"]},{"year":2019,"claim":"Identified the endogenous neuropeptide nocistatin as a direct proton-like agonist of ASIC2a, suggesting a non-proton activation ligand for ASICs.","evidence":"Oocyte electrophysiology with mambalgin-2 antagonist controls","pmids":["31443477"],"confidence":"Medium","gaps":["Binding site and physiological relevance not established","Heterologous expression only"]},{"year":2020,"claim":"Resolved the molecular basis of ion selectivity in ASIC2a, showing conserved E18' plus ASIC2a-specific upper-pore E59/E62 govern Na+ preference differently from ASIC1a.","evidence":"Mutagenesis, electrophysiology, and molecular dynamics free-energy simulations","pmids":["31952079"],"confidence":"High","gaps":["No experimental atomic structure of the ASIC2a pore","Selectivity in heteromers not addressed"]},{"year":2021,"claim":"Established a disease mechanism: an albumin/ERK-induced truncated ASIC2b variant co-assembling with ASIC2a mediates renal sodium retention in nephrotic syndrome.","evidence":"Oocyte electrophysiology, ASIC2b-null rat nephrotic model, and renal/ERK signaling analysis","pmids":["34166227"],"confidence":"High","gaps":["Localization of the active channel along the nephron not fully defined","Direct channel activity in vivo not measured"]},{"year":2021,"claim":"Placed ASIC2 upstream of TRPV1 in baroreceptor mechanotransduction, showing the two form a complex and that ASIC2 inhibition blocks stretch-activated currents.","evidence":"Co-IP, biotin pull-down, cell-attached patch clamp in HEK293T, and aortic nerve recording","pmids":["34215968"],"confidence":"Medium","gaps":["Whether ASIC2 directly senses stretch versus relays to TRPV1 unresolved","Includes heterologous reconstitution"]},{"year":2022,"claim":"Demonstrated functional partnership of ASIC2 and βENaC in vascular myogenic responses, with both jointly required for full renal afferent arteriolar constriction.","evidence":"Co-IP from VSMCs and pressure myography in single and double KO mice","pmids":["35285274"],"confidence":"High","gaps":["Whether ASIC2/βENaC form a single channel complex not established","Mechanosensing mechanism unresolved"]},{"year":2023,"claim":"Established a physiological proprioceptive role, showing ASIC2 is required for muscle spindle stretch responses, motor coordination, and spinal alignment.","evidence":"In vivo proprioception tests, ex vivo muscle spindle electrophysiology, and skeletal analysis in Asic2 KO mice","pmids":["36951012"],"confidence":"Medium","gaps":["Whether ASIC2 directly transduces spindle stretch versus modulates unresolved"]},{"year":2023,"claim":"Defined ASIC2A as the predominant nucleus accumbens subunit that integrates with ASIC1A and influences spine morphology and drug reward, though regional restoration alone is insufficient to rescue reward behavior.","evidence":"Western blot, AAV rescue, MSN patch clamp, conditioned place preference, and spine morphology in Asic2 KO mice","pmids":["36793786"],"confidence":"Medium","gaps":["Circuit-level mechanism of reward modulation unresolved","Failure of regional rescue not explained"]},{"year":null,"claim":"How ASIC2 transduces or modulates mechanical force across its diverse vascular, baroreceptor, and proprioceptive roles remains unresolved, as does an experimental atomic structure of ASIC2-containing channels and the adaptor machinery reading its trafficking motifs.","evidence":"No direct evidence in the available corpus","pmids":[],"confidence":"Low","gaps":["No atomic structure of ASIC2 channels","Direct mechanosensing mechanism undetermined","Trafficking adaptors for di-leucine motifs unidentified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,2,29]},{"term_id":"GO:0140299","term_label":"molecular sensor activity","supporting_discovery_ids":[11,28]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[11,31,33]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[9,12,20,22,24]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[12,13,23]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[19,20,21,34]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[4,10,25]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[18]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[2,29,30]}],"complexes":["ASIC2a/ASIC3 heteromeric channel","ASIC2a/ASIC2b heteromeric channel","ASIC1a/ASIC2a/ASIC3 heteromeric channel"],"partners":["ASIC1A","ASIC3","ASIC2B","PICK1","AKAP5","HSPA8","DLG4","TRPV1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q16515","full_name":"Acid-sensing ion channel 2","aliases":["Amiloride-sensitive cation channel 1, neuronal","Amiloride-sensitive cation channel neuronal 1","Brain sodium channel 1","BNC1","BNaC1","Mammalian degenerin homolog","MDEG"],"length_aa":512,"mass_kda":57.7,"function":"Forms pH-gated trimeric sodium channels that act as postsynaptic excitatory sensors in the nervous system (PubMed:10842183, PubMed:23034652, PubMed:8626462, PubMed:8631835). Upon extracellular acidification, these channels generate rapid, transient inward currents that fully desensitize (PubMed:10842183). Highly selective for sodium, they are permeable to other cations (PubMed:8626462, PubMed:8631835). By forming heterotrimeric channels with ASIC1, could contribute to synaptic plasticity, learning, and memory. Additionally, as acid sensors at nerve terminals, plays a role in mechanosensation and phototransduction (By similarity)","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q16515/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ASIC2","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/ASIC2","total_profiled":1310},"omim":[{"mim_id":"611741","title":"ACID-SENSING ION CHANNEL, SUBUNIT 3; ASIC3","url":"https://www.omim.org/entry/611741"},{"mim_id":"602866","title":"ACID-SENSING ION CHANNEL, SUBUNIT 1; ASIC1","url":"https://www.omim.org/entry/602866"},{"mim_id":"601784","title":"ACID-SENSING ION CHANNEL, SUBUNIT 2; ASIC2","url":"https://www.omim.org/entry/601784"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"brain","ntpm":12.7},{"tissue":"cervix","ntpm":5.5},{"tissue":"endometrium 1","ntpm":3.2},{"tissue":"retina","ntpm":4.2}],"url":"https://www.proteinatlas.org/search/ASIC2"},"hgnc":{"alias_symbol":["ASIC2a","BNC1","BNaC1","hBNaC1","MDEG"],"prev_symbol":["ACCN","ACCN1"]},"alphafold":{"accession":"Q16515","domains":[{"cath_id":"1.10.287.770","chopping":"15-67_425-453","consensus_level":"high","plddt":91.0167,"start":15,"end":453},{"cath_id":"2.60.470.10","chopping":"72-96_161-281_364-422","consensus_level":"medium","plddt":94.3901,"start":72,"end":422},{"cath_id":"1.10.3590.10","chopping":"99-155","consensus_level":"medium","plddt":92.4889,"start":99,"end":155},{"cath_id":"1.10.287.820","chopping":"291-360","consensus_level":"medium","plddt":90.0296,"start":291,"end":360}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q16515","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q16515-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q16515-F1-predicted_aligned_error_v6.png","plddt_mean":86.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ASIC2","jax_strain_url":"https://www.jax.org/strain/search?query=ASIC2"},"sequence":{"accession":"Q16515","fasta_url":"https://rest.uniprot.org/uniprotkb/Q16515.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q16515/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q16515"}},"corpus_meta":[{"pmid":"9037075","id":"PMC_9037075","title":"BNaC1 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Gain-of-function mutations homologous to those causing neurodegeneration in C. elegans constitutively activate the channel and cause cell death in mammalian cells, indicating the channel's ion-conducting activity underlies its cytotoxic effects.\",\n      \"method\": \"Electrophysiology (Xenopus oocyte expression), gain-of-function mutagenesis, cell death assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct electrophysiological characterization with mutagenesis showing constitutive activation causes cell death; foundational study replicated across the field\",\n      \"pmids\": [\"8631835\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"BNaC1 (ASIC2) and BNaC2 form a new branch of the DEG/ENaC superfamily. Both genes are co-expressed in most brain neurons throughout life, consistent with assembly into heteromultimeric channels.\",\n      \"method\": \"cDNA cloning, Northern blot, in situ hybridization, chromosomal mapping (17q11.2-12)\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — foundational cloning and expression study; heteromultimerization proposed but not yet experimentally confirmed in this paper\",\n      \"pmids\": [\"9037075\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"ASIC2a and ASIC3 subunits co-assemble into functional heteromeric proton-gated channels with greatly amplified acid-induced currents (up to 20-fold larger than homomers), a cation current selective for sodium, and increased sensitivity to gadolinium (IC50 ~40 µM vs. ≥1 mM for ASIC2a alone). Biochemical co-purification from HEK293 cells and Xenopus oocytes confirmed direct physical interaction.\",\n      \"method\": \"Xenopus oocyte electrophysiology, co-immunoprecipitation/co-purification from HEK293 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-purification plus functional electrophysiology with multiple orthogonal methods\",\n      \"pmids\": [\"10842183\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"PICK1 (a PDZ domain protein) interacts specifically with BNaC1/ASIC2 via the PDZ domain of PICK1 and the last four amino acids of ASIC2. Co-expression of both proteins leads to their clustering in intracellular compartments. PICK1 co-localizes with ASIC2 at peripheral mechanosensory nerve endings of DRG neurons and in dendrites of central neurons.\",\n      \"method\": \"Yeast two-hybrid screen, GST pull-down, co-immunoprecipitation, immunohistochemistry, subcellular localization imaging\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal biochemical methods (yeast two-hybrid, GST pull-down, co-IP) plus in vivo localization; single lab but comprehensive\",\n      \"pmids\": [\"11739374\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PKC potentiates ASIC2a current amplitude (~300%) when PICK1 is co-expressed, requiring both the PDZ domain of PICK1 and the PDZ-binding domain of ASIC2a. Direct PICK1-dependent phosphorylation of ASIC2a was demonstrated by 32P-labeling and immunoprecipitation; the major phosphorylation site was identified as Thr39 (TIR motif) in the N-terminus. PKC potentiation did not alter ASIC2a unitary conductance.\",\n      \"method\": \"Electrophysiology (whole-cell patch clamp), 32P phosphorylation labeling, co-immunoprecipitation, site-directed mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct phosphorylation demonstrated by radiolabeling with phosphosite identified by mutagenesis, combined with electrophysiology; multiple orthogonal methods\",\n      \"pmids\": [\"12399460\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"ASIC2b (an N-terminal splice variant of ASIC2a from the same gene) co-assembles with ASIC2a to form heteromeric channels in taste cells. The ASIC2a/ASIC2b heteromeric channel generates maximal inward currents at pH ≤2.0, and amiloride sensitivity is almost abolished at pH 2.0, distinguishing it from ASIC2a homomers.\",\n      \"method\": \"Co-immunoprecipitation from circumvallate papillae, Xenopus oocyte electrophysiology, immunohistochemistry\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — native tissue co-IP plus functional electrophysiology characterizing heteromeric channel properties\",\n      \"pmids\": [\"12736332\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"ASIC2 and ASIC3 null mutations do not alter mechanically activated current amplitude or kinetics in DRG neuron cell bodies, indicating that ASIC2 is not a direct transducer of mechanical stimuli at the soma level.\",\n      \"method\": \"Whole-cell patch clamp of cultured DRG neurons from ASIC2-/- and ASIC3-/- knockout mice\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct electrophysiology in knockout neurons; rigorous negative result independently supported by the ASIC2 KO paper (PMID 15169849)\",\n      \"pmids\": [\"14990679\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"ASIC2 knockout mice show no impairment of cutaneous mechanosensation, visceral mechanonociception, or hearing, arguing against ASIC2 being an essential direct mechanotransducer in these modalities.\",\n      \"method\": \"Behavioral mechanosensation assays, auditory brainstem response, in vivo nerve recordings in ASIC2-/- mice\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — rigorous in vivo knockout study with multiple mechanosensory readouts; negative result for direct mechanotransducer role\",\n      \"pmids\": [\"15169849\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"ASIC2 protein expression in medium/large DRG neurons is maintained by BDNF signaling: ASIC2 mRNA and protein are dramatically down-regulated in BDNF-deficient mice, and exogenous BDNF (10–100 ng/ml) rescues ASIC2 expression in a dose- and time-dependent manner that requires new transcription and protein synthesis.\",\n      \"method\": \"Immunocytochemistry, RT-PCR, pharmacological block of transcription/translation, BDNF-deficient mouse DRG cultures\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — multiple methods (immunostaining, mRNA, KO mice, pharmacological rescue) but no direct signaling mechanism established\",\n      \"pmids\": [\"15708491\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"ASIC2 is retained intracellularly in high-grade glioma cells; forcing its surface expression (via glycerol or sodium 4-phenylbutyrate) abolishes the constitutively active amiloride-sensitive inward Na+ current and reduces glioma cell growth and migration, indicating ASIC2 exerts negative regulation of this ENaC/DEG-mediated conductance when present at the plasma membrane.\",\n      \"method\": \"Electrophysiology (whole-cell patch clamp), cell migration assays, surface biotinylation, chemical chaperone treatment\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — electrophysiology plus functional migration/growth assays; single lab, mechanistic pharmacological intervention\",\n      \"pmids\": [\"16704974\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"AKAP150 and the protein phosphatase calcineurin bind to ASIC2a (and ASIC1a) as demonstrated by pulldown and mass spectrometry followed by co-immunoprecipitation. Inhibiting PKA-AKAP150 interaction (Ht-31 peptide) reduces ASIC currents, while inhibiting calcineurin (cyclosporin A) increases ASIC currents, indicating that calcineurin-dependent dephosphorylation tonically inhibits ASIC2a activity.\",\n      \"method\": \"GST pulldown, mass spectrometry, co-immunoprecipitation, whole-cell patch clamp in cortical neurons and CHO cells, pharmacological inhibition\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mass spec identification confirmed by co-IP, functional validation with two independent pharmacological tools in neurons and heterologous cells\",\n      \"pmids\": [\"17548344\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Five specific protonatable residues in the extracellular loop of ASIC2a are required for proton-gated activation; mutating any one of these sites abolishes acid sensitivity while the channels still traffic normally to the cell surface and retain the capacity to form functional heteromers.\",\n      \"method\": \"Site-directed mutagenesis, immunocytochemistry (surface trafficking), whole-cell patch clamp electrophysiology\",\n      \"journal\": \"Neuroscience letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — site-directed mutagenesis with functional electrophysiology and trafficking controls; single lab but rigorous mechanistic dissection\",\n      \"pmids\": [\"17881127\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Hsc70 co-immunoprecipitates with ASIC2 and is overexpressed in glioma cells versus normal astrocytes. Hsc70 siRNA knockdown inhibits the constitutive amiloride-sensitive current, decreases glioma migration, and increases ASIC2 surface expression, demonstrating that Hsc70 retains ASIC2 in the ER of glioma cells.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, electrophysiology, cell migration assay, surface biotinylation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP plus siRNA knockdown with multiple functional readouts; single lab with orthogonal methods\",\n      \"pmids\": [\"17878160\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Hsc70 inhibits ASIC2 surface expression in vascular smooth muscle cells (VSMCs). Hsc70 silencing increases ASIC2 cell surface expression and inhibits VSMC migration; co-silencing of ASIC2 abolishes this effect, placing ASIC2 downstream of Hsc70 in regulating VSMC migration.\",\n      \"method\": \"siRNA knockdown, surface expression assay, VSMC migration (chemotaxis) assay\",\n      \"journal\": \"American journal of physiology. Heart and circulatory physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional epistasis by co-silencing with migration readout; single lab\",\n      \"pmids\": [\"18310515\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Pressure-induced (myogenic) constriction in mouse middle cerebral arteries is impaired in ASIC2-/- and ASIC2+/- mice, while constriction to KCl and phenylephrine is unaffected, demonstrating that normal ASIC2 expression is required for the myogenic response in cerebral arteries.\",\n      \"method\": \"Pressure myography on isolated middle cerebral arteries from ASIC2 knockout mice\",\n      \"journal\": \"American journal of physiology. Heart and circulatory physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — well-controlled in vitro vascular preparation with genetic knockout; single lab\",\n      \"pmids\": [\"18296560\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"ASIC2a and ASIC3 are the principal ASIC subunits in cardiac dorsal root ganglia afferents. In ASIC3-/- cardiac afferents, currents match ASIC2a homomeric properties; in ASIC2-/- afferents, currents match ASIC3 homomeric properties; currents are absent in ASIC2/3 double knockouts, establishing that ASIC2a and ASIC3 heteromultimerize to form the predominant channels in cardiac DRG neurons.\",\n      \"method\": \"Retrograde labeling, patch-clamp electrophysiology in ASIC-null mice (ASIC2-/-, ASIC3-/-, double KO)\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis using multiple knockout combinations with direct electrophysiological readout\",\n      \"pmids\": [\"19590043\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Triple knockout of ASIC1a, ASIC2, and ASIC3 increases cutaneous mechanosensitivity (enhanced A-mechanonociceptor responses), the opposite of what would be expected if ASICs directly transduce mechanical stimuli, suggesting ASICs modulate rather than directly mediate cutaneous mechanotransduction.\",\n      \"method\": \"Behavioral von Frey assays, single-fiber nerve recordings in triple ASIC knockout mice\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo genetic and electrophysiological analysis; single lab but multi-modal readout\",\n      \"pmids\": [\"22506072\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"ASIC1a, ASIC2a, and ASIC3 heteromultimerize to form the principal acid-sensing channels in skeletal muscle afferents. Deletion of ASIC2 selectively abolishes zinc potentiation of acid-evoked currents in muscle afferents, and currents are absent in triple-null mice, establishing the subunit composition of native muscle afferent ASICs.\",\n      \"method\": \"Patch-clamp electrophysiology in labeled muscle afferents from ASIC-null mice, pharmacological profiling (zinc potentiation)\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple genetic knockout combinations with pharmacological subunit fingerprinting\",\n      \"pmids\": [\"23109675\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Hyperactivation of MDEG/ASIC2 (G430F mutant) causes intracellular Ca2+ overload and ROS production leading to inhibition of proteasomal and autophagic degradation, accumulation of protein aggregates containing caspase-8, and subsequent caspase-8-dependent apoptosis. This pathway is independent of Bax/Bak but dependent on p62 and LC3.\",\n      \"method\": \"Tetracycline-inducible expression system, calcium imaging, ROS measurement, flow cytometry apoptosis assay, caspase activity assay, siRNA knockdown of p62 and LC3\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mechanistic pathway dissected with inducible gain-of-function, calcium chelation, ROS scavenging, caspase inhibition, and siRNA knockdown; multiple orthogonal methods\",\n      \"pmids\": [\"23239879\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"ASIC2 is expressed in brain regions of high synaptic density and co-localizes with ASIC1. Loss of ASIC2 decreases freezing behavior in contextual and auditory fear conditioning, predator odor, and CO2 inhalation assays, and increases activity in forced swim, demonstrating that ASIC2 modulates defensive responses to aversive stimuli in vivo.\",\n      \"method\": \"Immunohistochemistry, behavioral assays (fear conditioning, predator odor, CO2, forced swim) in ASIC2-/- mice\",\n      \"journal\": \"Genes, brain, and behavior\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined behavioral phenotypes in KO mice with anatomical localization; single lab\",\n      \"pmids\": [\"24256442\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"ASIC2 subunits increase cell surface expression of ASIC1a-containing channels when co-expressed, and genetic deletion of ASIC2 reduces acid-evoked current amplitude in hippocampal neurons. ASIC2a interacts with PSD-95, and PSD-95 reduces ASIC2a surface expression and current amplitude; this effect requires ASIC2 (absent in ASIC2-/- neurons).\",\n      \"method\": \"Surface biotinylation, patch-clamp electrophysiology in ASIC2-/- hippocampal neurons, co-immunoprecipitation, PSD-95 overexpression\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — co-IP plus surface expression plus electrophysiology in native neurons with genetic KO confirmation; multiple orthogonal methods\",\n      \"pmids\": [\"24699665\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"ASIC2 deletion reduces acid-activated current in cortical and striatal neurons but not cerebellar granule neurons (region-specific effect). ASIC2a (but not ASIC2b) facilitates ASIC1a surface trafficking in the brain, and ASIC2 is important for ASIC1a expression levels. ASIC2 deletion reduces ischemia-induced neuronal injury in cortex/hippocampus but not cerebellum, and protects mouse brain from ischemic damage in vivo.\",\n      \"method\": \"Whole-cell patch clamp in neurons from ASIC2-/- mice, surface biotinylation, organotypic slice injury assays, in vivo MCAO stroke model\",\n      \"journal\": \"Journal of cerebral blood flow and metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — electrophysiology, biochemistry, and in vivo stroke model with genetic KO; multiple orthogonal methods in single study\",\n      \"pmids\": [\"26861816\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Two di-leucine (LL) motifs in the C-terminal juxtamembrane region of ASIC2a act as negative regulators of trafficking: mutating either LL motif increases total and surface ASIC2a expression, enhances dendritic and dendritic spine targeting in hippocampal neurons, increases acid-activated current density, and mutating the second LL motif also increases pH sensitivity.\",\n      \"method\": \"Site-directed mutagenesis, surface biotinylation, electrophysiology, immunofluorescence imaging in organotypic hippocampal slices\",\n      \"journal\": \"Molecular brain\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mutagenesis with multiple functional readouts (trafficking, electrophysiology, subcellular localization) in heterologous and neuronal systems\",\n      \"pmids\": [\"26819004\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"ASIC2a facilitates surface trafficking of ASIC3 via heteromeric assembly; ASIC3 mostly accumulates in the ER alone but is delivered to the plasma membrane when co-expressed with ASIC2a, confirmed by BiFC assay. ASIC2a-dependent ASIC3 surface expression enhances the sustained component of acid-evoked currents.\",\n      \"method\": \"Surface biotinylation, bimolecular fluorescence complementation (BiFC), electrophysiology in heterologous cells\",\n      \"journal\": \"BMB reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — BiFC plus surface expression plus electrophysiology; single lab, heterologous system\",\n      \"pmids\": [\"27241858\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"ASIC2a promotes surface trafficking of ASIC2b via heteromeric assembly. The first transmembrane domain and proximal post-TM1 region (17 amino acids) of ASIC2a are critical for membrane targeting. Replacing corresponding ASIC2b residues with those of ASIC2a confers both proton sensitivity and surface expression to ASIC2b.\",\n      \"method\": \"Chimeric channel construction, surface biotinylation, electrophysiology in heterologous cells\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — domain-swap mutagenesis with functional validation; single lab, heterologous system only\",\n      \"pmids\": [\"27477936\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"ASIC2 activates the calcineurin/NFAT1 signaling pathway under acidosis in colorectal cancer cells, promoting invasion and metastasis. Inhibition of calcineurin/NFAT with cyclosporin A blocks ASIC2-induced invasion. ChIP-seq of NFAT1 identified downstream target genes in Rho GTPase and calcium signaling pathways.\",\n      \"method\": \"Gene overexpression/knockdown, matrigel invasion assay, in vivo xenograft/metastasis models, calcineurin inhibitor pharmacology, ChIP-seq\",\n      \"journal\": \"Journal of experimental & clinical cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro and in vivo functional assays with pharmacological pathway inhibition and ChIP-seq; single lab\",\n      \"pmids\": [\"28927426\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Psalmotoxin 1 (PcTx1) has dual actions at ASIC1a/ASIC2a heteromeric channels: potent inhibition at desensitizing conditioning pH (IC50=2.9 nM at pH 7.0), and potent potentiation at physiological pH (EC50=56.1 nM in CHO cells; threshold <10 nM in cortical neurons) by increasing channel apparent proton affinity for activation.\",\n      \"method\": \"Whole-cell patch clamp in CHO cells and cortical neurons, concentration-response analysis\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct electrophysiology with quantitative pharmacology in two cell systems; single lab\",\n      \"pmids\": [\"29739981\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Three N-terminal residues of ASIC2a (T25, T39, and I40) determine rapid resensitization: mutating these residues causes prolonged desensitization (phenocopying ASIC2b) in homomeric and heteromeric channels. This desensitization is not due to channel internalization or degradation.\",\n      \"method\": \"Site-directed mutagenesis, domain-swapping chimeras, whole-cell patch clamp, internalization assays\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis identifying specific residues with functional electrophysiology and mechanistic controls; single lab but rigorous\",\n      \"pmids\": [\"31010811\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Nocistatin, an endogenous neuropeptide, is a direct agonist of ASIC2a (as well as ASIC1a, ASIC1b, ASIC3), evoking proton-like currents in Xenopus oocytes; the mambalgin-2 antagonist (ASIC1a blocker) inhibits nocistatin-induced currents, suggesting a similar activation mechanism to protons.\",\n      \"method\": \"Xenopus oocyte electrophysiology, pharmacological characterization with peptide toxins\",\n      \"journal\": \"Biomolecules\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct electrophysiological activation assay with pharmacological controls; single lab, heterologous expression\",\n      \"pmids\": [\"31443477\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Ion selectivity in ASIC2a-containing channels is determined differently from ASIC1a: E18' residues at the lower pore are conserved and create energetic preference for Na+ in ASIC2a, but the L7' residues (critical in ASIC1a) do not determine ion permeation in ASIC2a. Instead, ASIC2a-specific negatively charged residues E59 and E62 in the upper pore compensate, making the GAS belt more important for selectivity.\",\n      \"method\": \"Site-directed mutagenesis, whole-cell electrophysiology, molecular dynamics free energy simulations\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mutagenesis combined with molecular dynamics simulations and electrophysiology with multiple residues systematically tested\",\n      \"pmids\": [\"31952079\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"A truncated variant of ASIC2b, whose expression in kidney tubules is induced by luminal albumin and ERK activation, produces sustained acid-stimulated sodium currents when co-expressed with ASIC2a. ASIC2b-null rats in a corticosteroid-clamped nephrotic model do not develop sodium retention, establishing this ASIC2b variant as the mediator of renal Na+ retention in nephrotic syndrome.\",\n      \"method\": \"Xenopus oocyte electrophysiology, ASIC2b-null rat model, renal function measurements, ERK signaling analysis\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — functional electrophysiology plus genetic knockout rat model plus upstream signaling mechanism; multiple orthogonal methods\",\n      \"pmids\": [\"34166227\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"ASIC2 and TRPV1 co-localize in aortic baroreceptor nerve endings and form a physical complex confirmed by co-immunoprecipitation and biotin pull-down. In HEK293T cells co-expressing both proteins, inhibition of ASIC2 (but not TRPV1) completely blocks stretch-activated currents, indicating ASIC2 is required upstream of TRPV1 in baroreceptor mechanotransduction.\",\n      \"method\": \"Co-immunoprecipitation, biotin pull-down, cell-attached patch clamp in HEK293T cells, aortic arch nerve recording, immunofluorescence\",\n      \"journal\": \"Neuroscience bulletin\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, pull-down, and functional electrophysiology; single lab, includes heterologous expression\",\n      \"pmids\": [\"34215968\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"βENaC and ASIC2 form biochemical complexes in vascular smooth muscle cells (co-immunoprecipitation). In renal afferent arterioles, pressure-induced constriction is abolished in ASIC2-/-/βENaCm/m double-mutant mice but only partially impaired in single mutants, demonstrating that βENaC and ASIC2 interact functionally and are jointly required for the full myogenic response.\",\n      \"method\": \"Co-immunoprecipitation from VSMCs, isolated afferent arteriole-attached glomerulus pressure myography in single and double KO mice\",\n      \"journal\": \"American journal of physiology. Renal physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP plus genetic epistasis with double KO in ex vivo vascular preparation; multiple orthogonal approaches\",\n      \"pmids\": [\"35285274\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"ASIC2 is expressed in proprioceptive sensory neurons. Asic2 loss-of-function mice display impaired muscle spindle responses to stretch and deficits in motor coordination tasks. Analysis of skeletons revealed specific effects on spinal alignment, identifying ASIC2 as a component of proprioceptive sensing.\",\n      \"method\": \"In vivo proprioception behavioral tests, ex vivo muscle spindle electrophysiology, skeletal analysis in Asic2 KO mice\",\n      \"journal\": \"Experimental physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo and ex vivo functional tests in KO mice with electrophysiological validation; single lab\",\n      \"pmids\": [\"36951012\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"ASIC2A (but not ASIC2B) is the predominant ASIC2 subunit in nucleus accumbens core. Recombinant ASIC2A expressed via AAV integrates with endogenous ASIC1A to form functional channels in medium spiny neurons. Loss of ASIC2 alters dendritic spine morphology and increases conditioned place preference to cocaine and morphine, but region-restricted ASIC2A restoration in nucleus accumbens core is insufficient to rescue cocaine/morphine preference.\",\n      \"method\": \"Western blot, AAV-mediated in vivo rescue, patch-clamp electrophysiology in MSNs, conditioned place preference, dendritic spine morphology analysis\",\n      \"journal\": \"Frontiers in molecular biosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo rescue with electrophysiological confirmation of heteromeric assembly; single lab, multiple readouts\",\n      \"pmids\": [\"36793786\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ASIC2 (BNaC1/MDEG) is a proton-gated, amiloride-sensitive Na+-selective cation channel of the DEG/ENaC superfamily that obligately forms homotrimeric or heterotrimeric complexes with ASIC1a, ASIC2b, ASIC3, and βENaC; its subunit composition determines pH sensitivity, ion selectivity (governed by conserved E18' and ASIC2a-specific E59/E62 in the pore), and pharmacology; its trafficking to the plasma membrane is negatively regulated by di-leucine motifs in its C-terminal juxtamembrane region and by Hsc70-mediated ER retention, and positively promoted by ASIC2a's TM1 domain enabling co-assembly with ASIC2b and ASIC3; its activity is dynamically regulated by PKC-dependent phosphorylation at T39 via the PDZ scaffold PICK1, and by calcineurin-dependent dephosphorylation anchored by AKAP150; ASIC2 forms physical complexes with PSD-95 (reducing surface expression), TRPV1 (baroreceptor mechanotransduction), and βENaC (renal/cerebrovascular myogenic constriction); endogenous nocistatin directly activates ASIC2a; hyperactivation of ASIC2/MDEG causes Ca2+-overload-driven caspase-8 apoptosis via p62/LC3-dependent protein aggregate formation; and at the systems level ASIC2 is required for proprioceptive muscle spindle responses, modulation of fear/aversive behaviors, renal sodium retention in nephrotic syndrome (via a truncated ASIC2b variant), and normal myogenic vasoconstriction in cerebral and renal vessels.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ASIC2 (MDEG/BNaC1) is a proton-gated, amiloride-sensitive cation channel of the DEG/ENaC superfamily whose ion-conducting activity, when constitutively activated by gain-of-function mutation, is directly cytotoxic [#0]. Proton gating depends on a set of protonatable residues in the extracellular loop, and mutating any one abolishes acid sensitivity without disrupting surface trafficking or heteromer formation [#11]; Na+ selectivity is set by a conserved lower-pore E18' acidic residue working together with ASIC2a-specific upper-pore residues E59/E62, distinguishing the basis of selectivity from ASIC1a [#29]. ASIC2 functions principally as a modulatory subunit that co-assembles into heteromeric channels with ASIC2b, ASIC3, and ASIC1a, with subunit composition dictating current amplitude, pH dependence, desensitization kinetics, and pharmacology [#2, #5, #15, #17]; ASIC2a's first transmembrane domain and proximal post-TM1 region drive both its own membrane targeting and the surface delivery of partner subunits ASIC2b, ASIC3, and ASIC1a [#24, #23, #21]. Surface expression is held in check by C-terminal di-leucine motifs [#22], by Hsc70-mediated ER retention [#12], and by PSD-95 binding [#20], while channel activity is dynamically tuned by PICK1-anchored PKC phosphorylation at Thr39 [#3, #4] and by AKAP150-anchored calcineurin dephosphorylation [#10]. Through these heteromers ASIC2 contributes to acid sensing in sensory afferents and the brain rather than acting as a direct mechanotransducer, since cutaneous mechanosensation, hearing, and somatic mechanically activated currents are intact or even enhanced in ASIC2-null animals [#6, #7, #16]. At the systems level ASIC2 is required for proprioceptive muscle spindle responses [#33], modulates fear and aversive behaviors [#19], supports myogenic vasoconstriction in cerebral and renal vessels jointly with βENaC [#14, #32], contributes to ischemic neuronal injury [#21], and, via an albumin/ERK-induced truncated ASIC2b variant, mediates renal sodium retention in nephrotic syndrome [#30]. Hyperactivation drives Ca2+ overload and ROS that block proteasomal/autophagic degradation, producing p62/LC3-dependent aggregates and caspase-8 apoptosis [#18].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Established that ASIC2/MDEG is an ion-conducting amiloride-sensitive cation channel and that its conductance itself can be cytotoxic, linking channel activity to neurodegeneration.\",\n      \"evidence\": \"Electrophysiology in Xenopus oocytes with gain-of-function mutagenesis and cell death assays\",\n      \"pmids\": [\"8631835\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish physiological gating stimulus\", \"Native subunit partners unknown\", \"No structural basis for ion conduction\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Defined ASIC2 as a brain-expressed member of a new DEG/ENaC branch co-expressed with a related subunit, raising the possibility of heteromeric channels.\",\n      \"evidence\": \"cDNA cloning, Northern blot, in situ hybridization, chromosomal mapping\",\n      \"pmids\": [\"9037075\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Heteromultimerization proposed but not demonstrated\", \"Functional channel properties not characterized\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Showed that ASIC2 is a partner subunit whose co-assembly reshapes channel function, demonstrating direct heteromerization with ASIC3.\",\n      \"evidence\": \"Co-purification from HEK293 cells and oocyte electrophysiology\",\n      \"pmids\": [\"10842183\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of heteromer not resolved\", \"Physiological context of ASIC2a/ASIC3 channels not established\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Identified PICK1 as a direct PDZ-domain partner of the ASIC2 C-terminus that clusters the channel, providing a scaffold linking ASIC2 to regulatory machinery.\",\n      \"evidence\": \"Yeast two-hybrid, GST pull-down, co-IP, and immunohistochemistry in DRG and central neurons\",\n      \"pmids\": [\"11739374\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of clustering not yet shown\", \"Did not establish phosphorylation regulation\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Connected the PICK1 scaffold to functional regulation, showing PKC potentiates ASIC2a current via direct phosphorylation at Thr39.\",\n      \"evidence\": \"Whole-cell patch clamp, 32P labeling, co-IP, and site-directed mutagenesis\",\n      \"pmids\": [\"12399460\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Upstream signals activating PKC at the channel unknown\", \"Did not address dephosphorylation\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Demonstrated that the ASIC2b splice variant co-assembles with ASIC2a to produce channels with distinct extreme-acid responsiveness, expanding the functional repertoire from one gene.\",\n      \"evidence\": \"Native co-IP from taste tissue and oocyte electrophysiology\",\n      \"pmids\": [\"12736332\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trafficking determinants of the heteromer not defined\", \"Physiological role in taste not established\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Resolved whether ASIC2 is a direct somatic mechanotransducer; knockout neurons and mice retained normal mechanically activated currents and mechanosensation, arguing against a direct transducer role.\",\n      \"evidence\": \"Patch clamp of knockout DRG neurons and in vivo mechanosensation/auditory assays in ASIC2-/- mice\",\n      \"pmids\": [\"14990679\", \"15169849\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not exclude modulatory mechanosensory roles in specialized endings\", \"Compensation by other ASICs not assessed\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Showed ASIC2 expression in DRG neurons is maintained by BDNF, identifying a transcriptional/trophic input controlling channel abundance.\",\n      \"evidence\": \"Immunocytochemistry, RT-PCR, and pharmacological rescue in BDNF-deficient mouse DRG cultures\",\n      \"pmids\": [\"15708491\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct signaling pathway from BDNF to ASIC2 transcription not defined\", \"Functional channel consequence not measured\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Revealed regulated intracellular retention of ASIC2 in glioma and that forced surface expression suppresses a constitutive Na+ conductance and tumor cell migration/growth, indicating negative regulation at the membrane.\",\n      \"evidence\": \"Patch clamp, migration assays, surface biotinylation, and chemical chaperone treatment\",\n      \"pmids\": [\"16704974\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Identity of the retention machinery not yet defined here\", \"Molecular basis of suppression of conductance unclear\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Identified Hsc70 as the ER-retention factor for ASIC2 in glioma, mechanistically explaining intracellular sequestration and its link to migration.\",\n      \"evidence\": \"Co-IP, siRNA knockdown, electrophysiology, migration assay, and surface biotinylation\",\n      \"pmids\": [\"17878160\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Hsc70 retention is selective for specific ASIC2 conformers unknown\", \"Generalizability beyond glioma not addressed here\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Mapped the proton-sensing apparatus to five extracellular protonatable residues required for gating but dispensable for trafficking and heteromerization.\",\n      \"evidence\": \"Site-directed mutagenesis with surface trafficking imaging and patch clamp\",\n      \"pmids\": [\"17881127\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Conformational mechanism coupling protonation to gating not resolved\", \"No structural model\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Defined a phosphatase arm of ASIC2 regulation, showing AKAP150 anchors calcineurin to tonically dephosphorylate and inhibit the channel, complementing PKC potentiation.\",\n      \"evidence\": \"GST pulldown, mass spec, co-IP, and pharmacological modulation in cortical neurons and CHO cells\",\n      \"pmids\": [\"17548344\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific dephosphorylation site not mapped\", \"Integration with PICK1/PKC at single channels unresolved\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Extended Hsc70-dependent retention of ASIC2 to vascular smooth muscle, placing ASIC2 downstream of Hsc70 in controlling VSMC migration.\",\n      \"evidence\": \"siRNA knockdown with co-silencing epistasis and migration assays in VSMCs\",\n      \"pmids\": [\"18310515\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Channel activity required for migration not directly demonstrated\", \"Single-lab functional epistasis\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Linked ASIC2 to vascular physiology, showing it is required for pressure-induced myogenic constriction of cerebral arteries.\",\n      \"evidence\": \"Pressure myography on cerebral arteries from ASIC2 knockout mice\",\n      \"pmids\": [\"18296560\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular partners in VSMC mechanosensing not identified here\", \"Whether ASIC2 senses pressure directly unknown\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Established native ASIC2a/ASIC3 heteromers as the predominant acid-sensing channels in cardiac afferents using genetic epistasis.\",\n      \"evidence\": \"Retrograde labeling and patch clamp across ASIC2-/-, ASIC3-/-, and double-KO mice\",\n      \"pmids\": [\"19590043\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional role in cardiac afferent signaling in vivo not measured here\", \"Stoichiometry not determined\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Defined the subunit composition of muscle afferent ASICs as ASIC1a/ASIC2a/ASIC3 heteromers, with ASIC2 specifically conferring zinc potentiation.\",\n      \"evidence\": \"Patch clamp with pharmacological fingerprinting in muscle afferents from ASIC-null mice\",\n      \"pmids\": [\"23109675\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of zinc potentiation in vivo unknown\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Showed ASICs modulate rather than directly mediate cutaneous mechanotransduction, since triple knockout enhanced rather than abolished mechanonociceptor responses.\",\n      \"evidence\": \"von Frey assays and single-fiber recordings in triple ASIC knockout mice\",\n      \"pmids\": [\"22506072\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of modulation unresolved\", \"ASIC2-specific contribution not isolated\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Dissected the cytotoxic pathway of hyperactivated ASIC2, showing Ca2+/ROS-driven degradation blockade produces p62/LC3-dependent aggregates and caspase-8 apoptosis independent of Bax/Bak.\",\n      \"evidence\": \"Inducible G430F expression with calcium imaging, ROS measurement, apoptosis/caspase assays, and p62/LC3 siRNA\",\n      \"pmids\": [\"23239879\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relevance to physiological ASIC2 activation unclear\", \"Trigger for aggregate formation not fully defined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Established ASIC2 as a brain channel that boosts ASIC1a surface expression and acid-evoked currents, with PSD-95 acting as a negative regulator of surface ASIC2a.\",\n      \"evidence\": \"Surface biotinylation, patch clamp in ASIC2-/- hippocampal neurons, co-IP, and PSD-95 overexpression\",\n      \"pmids\": [\"24699665\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which PSD-95 reduces surface expression not defined\", \"Interplay with PICK1 scaffolding unresolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Showed ASIC2a is a chaperone-like trafficking subunit that delivers ASIC1a, ASIC3, and ASIC2b to the membrane, and identified its TM1/post-TM1 region as the membrane-targeting determinant.\",\n      \"evidence\": \"Surface biotinylation, BiFC, chimeric domain swaps, and electrophysiology in heterologous cells and neurons\",\n      \"pmids\": [\"26861816\", \"27241858\", \"27477936\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Trafficking machinery engaged by TM1 not identified\", \"Largely heterologous systems for ASIC3/ASIC2b\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identified two C-terminal di-leucine motifs as autonomous negative regulators of ASIC2a trafficking, surface density, dendritic targeting, and pH sensitivity.\",\n      \"evidence\": \"Mutagenesis with surface biotinylation, electrophysiology, and imaging in hippocampal slices\",\n      \"pmids\": [\"26819004\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Adaptor proteins recognizing the di-leucine motifs not identified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Linked ASIC2 trafficking function to ischemic injury, showing ASIC2a facilitates ASIC1a surface delivery and that ASIC2 deletion protects brain regions from ischemic damage region-specifically.\",\n      \"evidence\": \"Patch clamp, biotinylation, organotypic slice injury, and in vivo MCAO stroke model in ASIC2-/- mice\",\n      \"pmids\": [\"26861816\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Region-specificity mechanism unresolved\", \"Relative contribution of ASIC2 vs ASIC1a to injury not separated\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Connected ASIC2 to a downstream transcriptional program, showing acidosis-driven ASIC2 activates calcineurin/NFAT1 to promote colorectal cancer invasion.\",\n      \"evidence\": \"Overexpression/knockdown, invasion and metastasis models, calcineurin inhibition, and NFAT1 ChIP-seq\",\n      \"pmids\": [\"28927426\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct coupling of channel conductance to calcineurin activation not demonstrated\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Characterized dual modulation of ASIC1a/ASIC2a heteromers by PcTx1, inhibiting under desensitizing pH and potentiating at physiological pH by increasing proton affinity.\",\n      \"evidence\": \"Concentration-response patch clamp in CHO cells and cortical neurons\",\n      \"pmids\": [\"29739981\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Toxin binding site on ASIC2a-containing heteromers not mapped\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identified three N-terminal ASIC2a residues (T25, T39, I40) that confer rapid resensitization, explaining a key kinetic difference from ASIC2b independent of internalization.\",\n      \"evidence\": \"Site-directed mutagenesis, domain-swap chimeras, patch clamp, and internalization assays\",\n      \"pmids\": [\"31010811\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural mechanism of N-terminal control of gating unresolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identified the endogenous neuropeptide nocistatin as a direct proton-like agonist of ASIC2a, suggesting a non-proton activation ligand for ASICs.\",\n      \"evidence\": \"Oocyte electrophysiology with mambalgin-2 antagonist controls\",\n      \"pmids\": [\"31443477\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Binding site and physiological relevance not established\", \"Heterologous expression only\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Resolved the molecular basis of ion selectivity in ASIC2a, showing conserved E18' plus ASIC2a-specific upper-pore E59/E62 govern Na+ preference differently from ASIC1a.\",\n      \"evidence\": \"Mutagenesis, electrophysiology, and molecular dynamics free-energy simulations\",\n      \"pmids\": [\"31952079\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No experimental atomic structure of the ASIC2a pore\", \"Selectivity in heteromers not addressed\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Established a disease mechanism: an albumin/ERK-induced truncated ASIC2b variant co-assembling with ASIC2a mediates renal sodium retention in nephrotic syndrome.\",\n      \"evidence\": \"Oocyte electrophysiology, ASIC2b-null rat nephrotic model, and renal/ERK signaling analysis\",\n      \"pmids\": [\"34166227\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Localization of the active channel along the nephron not fully defined\", \"Direct channel activity in vivo not measured\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Placed ASIC2 upstream of TRPV1 in baroreceptor mechanotransduction, showing the two form a complex and that ASIC2 inhibition blocks stretch-activated currents.\",\n      \"evidence\": \"Co-IP, biotin pull-down, cell-attached patch clamp in HEK293T, and aortic nerve recording\",\n      \"pmids\": [\"34215968\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether ASIC2 directly senses stretch versus relays to TRPV1 unresolved\", \"Includes heterologous reconstitution\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstrated functional partnership of ASIC2 and βENaC in vascular myogenic responses, with both jointly required for full renal afferent arteriolar constriction.\",\n      \"evidence\": \"Co-IP from VSMCs and pressure myography in single and double KO mice\",\n      \"pmids\": [\"35285274\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether ASIC2/βENaC form a single channel complex not established\", \"Mechanosensing mechanism unresolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Established a physiological proprioceptive role, showing ASIC2 is required for muscle spindle stretch responses, motor coordination, and spinal alignment.\",\n      \"evidence\": \"In vivo proprioception tests, ex vivo muscle spindle electrophysiology, and skeletal analysis in Asic2 KO mice\",\n      \"pmids\": [\"36951012\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether ASIC2 directly transduces spindle stretch versus modulates unresolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined ASIC2A as the predominant nucleus accumbens subunit that integrates with ASIC1A and influences spine morphology and drug reward, though regional restoration alone is insufficient to rescue reward behavior.\",\n      \"evidence\": \"Western blot, AAV rescue, MSN patch clamp, conditioned place preference, and spine morphology in Asic2 KO mice\",\n      \"pmids\": [\"36793786\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Circuit-level mechanism of reward modulation unresolved\", \"Failure of regional rescue not explained\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How ASIC2 transduces or modulates mechanical force across its diverse vascular, baroreceptor, and proprioceptive roles remains unresolved, as does an experimental atomic structure of ASIC2-containing channels and the adaptor machinery reading its trafficking motifs.\",\n      \"evidence\": \"No direct evidence in the available corpus\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No atomic structure of ASIC2 channels\", \"Direct mechanosensing mechanism undetermined\", \"Trafficking adaptors for di-leucine motifs unidentified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005216\", \"supporting_discovery_ids\": [0, 2, 11]},\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 2, 29]},\n      {\"term_id\": \"GO:0140299\", \"supporting_discovery_ids\": [11, 28]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [11, 31, 33]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [9, 12, 20, 22, 24]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [12, 13, 23]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [19, 20, 21, 34]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [4, 10, 25]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [18]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [2, 29, 30]}\n    ],\n    \"complexes\": [\n      \"ASIC2a/ASIC3 heteromeric channel\",\n      \"ASIC2a/ASIC2b heteromeric channel\",\n      \"ASIC1a/ASIC2a/ASIC3 heteromeric channel\"\n    ],\n    \"partners\": [\n      \"ASIC1a\",\n      \"ASIC3\",\n      \"ASIC2b\",\n      \"PICK1\",\n      \"AKAP5\",\n      \"HSPA8\",\n      \"DLG4\",\n      \"TRPV1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"tie","faith_supported":6,"faith_total":7,"faith_pct":85.71428571428571}}