{"gene":"CNGA4","run_date":"2026-06-09T22:57:18","timeline":{"discoveries":[{"year":2001,"finding":"Targeted deletion of CNGA4 in mice results in defective Ca2+-calmodulin-mediated desensitization of the olfactory CNG channel; excised membrane patches from CNGA4-null mice showed slower Ca2+-calmodulin-mediated channel desensitization, establishing that CNGA4 accelerates Ca2+-mediated negative feedback in olfactory signaling and is required for rapid odorant adaptation.","method":"Gene knockout mouse, excised membrane patch-clamp electrophysiology, Ca2+-calmodulin desensitization assay","journal":"Science","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined cellular and electrophysiological phenotype, replicated by independent lab in same journal issue (PMID:11739960)","pmids":["11739959"],"is_preprint":false},{"year":2001,"finding":"Ca2+-calmodulin-mediated negative feedback inhibition of the olfactory CNG channel requires both modulatory subunits CNGA4 and CNGB1b in addition to the principal CNGA2 subunit; CNGA2 alone (which possesses the CaM-binding site) is insufficient for rapid Ca2+-dependent adaptation without these auxiliary subunits.","method":"Heterologous expression in Xenopus oocytes and HEK cells, patch-clamp electrophysiology, Ca2+-calmodulin feedback assays with defined subunit combinations","journal":"Science","confidence":"High","confidence_rationale":"Tier 2 / Strong — defined subunit requirement with patch-clamp, independently replicated by two labs in same journal issue (PMID:11739959 and PMID:11739960)","pmids":["11739960","11739959"],"is_preprint":false},{"year":1998,"finding":"CNGA4 (CNG4.3), cloned from rat olfactory epithelium, is an isoform of the rod photoreceptor beta subunit that lacks the N-terminal glutamic acid-rich domain; coexpression with CNGA2 increases cAMP sensitivity, weakens outward rectification in extracellular Ca2+, reduces relative Ca2+ permeability, and enhances L-cis diltiazem sensitivity. Coexpression of CNGA2 + CNGA4 + CNGB1b (CNG5) yields cAMP sensitivity near that of the native olfactory channel.","method":"Molecular cloning, heterologous expression in HEK293 cells, patch-clamp electrophysiology, ion permeability and pharmacology assays","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro reconstitution with multiple orthogonal electrophysiological measurements, replicated in subsequent studies","pmids":["9539801"],"is_preprint":false},{"year":2006,"finding":"Ciliary trafficking of the olfactory CNG channel (comprising CNGA2, CNGA4, CNGB1b) requires heteroassembly with CNGB1b, which contains a critical C-terminal RVxP motif; CNGA4 alone is insufficient for ciliary targeting. Additionally, the kinesin-2 motor KIF17 is required for anterograde transport of the olfactory CNG channel into cilia.","method":"Transgenic mouse models, immunofluorescence localization, dominant-negative KIF17 expression, mutagenesis of RVxP motif","journal":"Current Biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct ciliary localization experiments with mutagenesis and motor protein knockdown, corroborated by independent study (PMID:16980309)","pmids":["16782012"],"is_preprint":false},{"year":2006,"finding":"In CNGB1-deficient mice, a CNGA2/CNGA4 channel is present in the olfactory epithelium (confirmed by co-immunoprecipitation) and traffics to the plasma membrane of olfactory knobs but fails to enter olfactory cilia. A similar ciliary trafficking defect occurs in CNGA4-deficient mice, demonstrating that both CNGA4 and CNGB1 are required for ciliary targeting of the olfactory CNG channel.","method":"Gene knockout mouse, co-immunoprecipitation, immunofluorescence/confocal microscopy, electro-olfactogram, patch-clamp electrophysiology","journal":"Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, direct subcellular localization with functional consequence, two KO models tested","pmids":["16980309"],"is_preprint":false},{"year":2003,"finding":"CNGA4-null mice are profoundly impaired in the detection and discrimination of olfactory stimuli in the presence of an adapting background odor in operant conditioning tasks, demonstrating that Ca2+-dependent CNG channel desensitization mediated by CNGA4 is essential for odor discrimination and adaptation in behaving animals.","method":"Gene knockout mouse, operant conditioning behavioral paradigm, electro-olfactogram","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined in vivo behavioral and electrophysiological phenotype","pmids":["12649326"],"is_preprint":false},{"year":2006,"finding":"Disruption of CNGA4 in mice reveals a profound defect in adaptation of MHC class I peptide-evoked field potentials in the main olfactory epithelium, showing that CNGA4 is required for adaptation to nonvolatile immune peptide olfactory cues.","method":"Gene knockout mouse, Ca2+ imaging, electro-olfactogram, behavioral preference assays","journal":"Journal of Neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with multiple electrophysiological and behavioral readouts","pmids":["16481428"],"is_preprint":false},{"year":2004,"finding":"The inability of CNGA4 to form functional homomeric channels was localized to a tripeptide in its C-linker domain. This tripeptide decreases the efficacy of ligand gating by preventing cAMP-induced assembly of C-terminal domains into a tetrameric gating ring, as demonstrated by analytical ultracentrifugation showing that cAMP causes gating ring disassembly when the CNGA4 tripeptide is present.","method":"Chimeric channel mutagenesis, patch-clamp electrophysiology in Xenopus oocytes, analytical ultracentrifugation of isolated C-terminal domains","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with mutagenesis plus biophysical structural analysis (analytical ultracentrifugation) in single study","pmids":["15572113"],"is_preprint":false},{"year":2000,"finding":"The CNGA4 (CNG5/beta) subunit increases cAMP selectivity of heteromeric olfactory CNG channels primarily through its cyclic nucleotide-binding region (CNBR); a single residue (M475) in the CNBR accounts for the altered cAMP/cGMP selectivity ratio. Ligand-independent effects of CNGA4 (voltage dependence, Mg2+ block properties, desensitization) reside outside the CNBR.","method":"Chimeric subunit construction, site-directed mutagenesis (M475E), heterologous expression in Xenopus oocytes, patch-clamp electrophysiology","journal":"Biophysical Journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mutagenesis with functional reconstitution in Xenopus oocytes, multiple chimeras tested","pmids":["10777729"],"is_preprint":false},{"year":2009,"finding":"Using site-directed mutagenesis and patch-clamp analysis, CNGA4 was assigned to a functional module that stabilizes the open state of the olfactory CNG channel at low cAMP concentrations (distinct from the channel-opening module in CNGA2 and the Ca2+-dependent feedback inhibition module), defining the gating logic of the olfactory transduction channel.","method":"Site-directed mutagenesis, patch-clamp electrophysiology, heterologous expression","journal":"Journal of General Physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis with electrophysiology, single lab, well-controlled but no independent replication cited","pmids":["19822638"],"is_preprint":false},{"year":2011,"finding":"The LQ-type calmodulin-binding site of CNGA4 binds Ca2+-calmodulin at 10-fold higher Ca2+ concentrations than the corresponding site on CNGB1, providing biochemical evidence against a primary role for CNGA4 in Ca2+-calmodulin feedback inhibition; the data suggest feedback control is the exclusive role of B-subunits.","method":"Recombinant protein expression, in vitro Ca2+-calmodulin binding assays (biochemical)","journal":"Biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct in vitro binding assay with recombinant domains, single lab, contradicts earlier genetic evidence (PMID:11739959); moderate uncertainty due to contradiction","pmids":["21413724"],"is_preprint":false},{"year":2001,"finding":"The cyclic nucleotide-binding domain (BD) of CNGA4 (beta/CNG5 subunit), when placed in a chimeric subunit with alpha-subunit transmembrane domains, can couple ligand binding to channel opening with higher opening efficacy and lower K1/2 than the corresponding alpha-subunit BD; both the roll subdomain and C-helix subdomain of CNGA4's BD contribute to this enhanced efficacy.","method":"Chimeric subunit construction (X-beta chimera), heterologous expression in Xenopus oocytes, excised patch-clamp, thermodynamic linkage analysis","journal":"Journal of General Physiology","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro reconstitution with chimeric subunits and functional electrophysiology, single lab","pmids":["11696610"],"is_preprint":false},{"year":2016,"finding":"In heterotetrameric olfactory CNG channels, the CNGA4 subunit (alongside CNGB1b) binds cyclic nucleotides and accelerates channel deactivation; both modulatory subunits contribute to rapid termination of the odorant signal, as shown by simultaneous ligand-binding and channel-activation measurements.","method":"Simultaneous fluorescence ligand-binding and patch-clamp electrophysiology, heterologous expression","journal":"Scientific Reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — orthogonal simultaneous binding/gating measurements, single lab","pmids":["27405959"],"is_preprint":false},{"year":2025,"finding":"In lateral habenular neurons, the long depolarizing phase of rebound depolarizing potentials is mediated by CNG channels activated via electrical coupling between neurons and non-neuronal cells (oligodendrocytes/OPCs); RNA-sequencing and genome editing experiments identified Cnga4 as the primary CNG channel subtype responsible for this long depolarization, and Cnga4 expression is decreased in stress-susceptible mice.","method":"Whole-cell patch-clamp, RNA-sequencing, CRISPR/genome editing, gap junction dye coupling, in situ hybridization","journal":"Journal of Physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — genome editing with electrophysiological phenotype, single lab, novel context","pmids":["40168081"],"is_preprint":false},{"year":1996,"finding":"The CNGA4 (oCNC2/CNG5) subunit mRNA is expressed in vomeronasal organ (VNO) sensory neurons but not in main olfactory epithelium neurons (which express the oCNC1/CNGA2 subunit), indicating distinct CNG channel subunit composition in the two olfactory organs.","method":"In situ hybridization, Northern blot analysis","journal":"Proceedings of the National Academy of Sciences","confidence":"Low","confidence_rationale":"Tier 3 / Weak — expression localization only, no functional mechanism established for CNGA4 specifically","pmids":["8637879"],"is_preprint":false}],"current_model":"CNGA4 is a modulatory subunit of the native heteromeric olfactory CNG channel (assembled as 2×CNGA2 + CNGA4 + CNGB1b), where it stabilizes the open state at low cAMP concentrations, accelerates Ca2+-calmodulin-mediated channel desensitization to enable rapid odorant adaptation, and—together with CNGB1b—is required for ciliary trafficking of the channel complex; its inability to form homomeric channels is attributable to a C-linker tripeptide that prevents ligand-induced gating-ring assembly."},"narrative":{"mechanistic_narrative":"CNGA4 is a modulatory subunit of the heteromeric olfactory cyclic-nucleotide-gated (CNG) channel that shapes the speed, sensitivity, and adaptation of odorant transduction in olfactory sensory neurons [PMID:9539801, PMID:12649326]. It cannot form functional homomeric channels: a tripeptide in its C-linker prevents cAMP from driving assembly of the C-terminal domains into a tetrameric gating ring, abolishing ligand-induced gating in the homomer [PMID:15572113]. When coassembled with the principal CNGA2 subunit and CNGB1b, CNGA4 contributes its cyclic-nucleotide-binding region to tune the channel's cAMP selectivity and sensitivity toward the native olfactory phenotype, with a single CNBR residue (M475) setting the cAMP/cGMP selectivity ratio [PMID:9539801, PMID:10777729], and it stabilizes the channel open state at low cAMP [PMID:19822638]. CNGA4 accelerates Ca2+-calmodulin-mediated desensitization and deactivation of the channel, providing the rapid negative feedback required for odorant adaptation and for discrimination against an adapting background, both at the level of channel kinetics and of animal behavior [PMID:11739959, PMID:11739960, PMID:12649326, PMID:27405959]. Together with CNGB1b, CNGA4 is also required for ciliary trafficking of the assembled channel: in CNGA4-deficient mice the channel reaches the plasma membrane of olfactory knobs but fails to enter the cilia [PMID:16782012, PMID:16980309]. Beyond olfaction, CNGA4 has been identified as the CNG subunit underlying a long rebound depolarization in lateral habenular neurons [PMID:40168081].","teleology":[{"year":1996,"claim":"Before any function was assigned, it was unknown where the CNGA4 subunit was expressed; establishing its restricted sensory expression framed it as an olfactory channel component.","evidence":"In situ hybridization and Northern blot across olfactory tissues","pmids":["8637879"],"confidence":"Low","gaps":["Expression localization only, no functional mechanism established","Reported VNO-restricted expression, leaving its role in main olfactory epithelium open"]},{"year":1998,"claim":"It was unclear what CNGA4 contributes to the channel; reconstitution showed it modulates cAMP sensitivity, rectification, Ca2+ permeability and pharmacology, and that the CNGA2+CNGA4+CNGB1b combination reproduces native cAMP sensitivity.","evidence":"Molecular cloning and heterologous expression in HEK293 with patch-clamp, ion permeability and pharmacology assays","pmids":["9539801"],"confidence":"High","gaps":["Did not resolve which structural element confers each property","Native subunit stoichiometry not defined"]},{"year":2000,"claim":"The structural basis of CNGA4's effect on ligand selectivity was unknown; mutagenesis localized cAMP selectivity to the CNBR and a single residue (M475), separating ligand-dependent from ligand-independent effects.","evidence":"Chimeric subunits and M475E site-directed mutagenesis with patch-clamp in Xenopus oocytes","pmids":["10777729"],"confidence":"High","gaps":["Did not localize the desensitization and voltage-dependent effects to specific residues","Conducted in heterologous chimeras rather than native channels"]},{"year":2001,"claim":"Whether CNGA4 contributes to gating efficacy was unresolved; chimera analysis showed its binding domain couples ligand binding to opening more efficaciously than the alpha-subunit domain.","evidence":"X-beta chimeric subunits, excised patch-clamp and thermodynamic linkage analysis in oocytes","pmids":["11696610"],"confidence":"Medium","gaps":["Single lab, chimeric context","Did not test contribution within the full native heteromer"]},{"year":2001,"claim":"The molecular requirement for rapid olfactory adaptation was unknown; knockout and reconstitution established that CNGA4 (with CNGB1b) is required for Ca2+-calmodulin-mediated desensitization that CNGA2 alone cannot provide.","evidence":"CNGA4-null mice, excised patch-clamp, and defined subunit reconstitution in oocytes/HEK with Ca2+-CaM feedback assays, replicated by two labs","pmids":["11739959","11739960"],"confidence":"High","gaps":["Did not define the CaM-binding site driving feedback","Mechanism of how an auxiliary subunit accelerates CaM action left open"]},{"year":2003,"claim":"It was unclear whether channel-level adaptation translated to behavior; CNGA4-null mice were profoundly impaired in odor discrimination and adaptation against a background odor.","evidence":"CNGA4 knockout mice in operant conditioning and electro-olfactogram","pmids":["12649326"],"confidence":"High","gaps":["Behavioral deficit not dissected from possible developmental or trafficking contributions"]},{"year":2004,"claim":"Why CNGA4 cannot form homomeric channels was unknown; the defect was localized to a C-linker tripeptide that blocks cAMP-induced gating-ring assembly.","evidence":"Chimeric mutagenesis with patch-clamp plus analytical ultracentrifugation of isolated C-terminal domains","pmids":["15572113"],"confidence":"High","gaps":["Structural detail of how the tripeptide perturbs the gating ring at atomic resolution not resolved","Single study"]},{"year":2006,"claim":"The route by which the olfactory channel reaches cilia was unknown; CNGA4 and CNGB1b were both shown to be required for ciliary targeting, with KIF17-dependent anterograde transport.","evidence":"Transgenic and knockout mice, co-immunoprecipitation, immunofluorescence, RVxP mutagenesis and dominant-negative KIF17","pmids":["16782012","16980309"],"confidence":"High","gaps":["The specific contribution of CNGA4 versus CNGB1b to the trafficking signal not separated","Direct interaction of CNGA4 with the transport machinery not shown"]},{"year":2006,"claim":"Whether CNGA4-dependent adaptation extended to nonvolatile cues was untested; knockout mice showed defective adaptation to MHC class I peptide-evoked responses.","evidence":"CNGA4 knockout mice with Ca2+ imaging, electro-olfactogram and behavioral preference assays","pmids":["16481428"],"confidence":"High","gaps":["Receptor/transduction pathway upstream of the CNG channel for peptide cues not defined"]},{"year":2009,"claim":"The gating logic of the heteromeric channel was unclear; CNGA4 was assigned to a module that stabilizes the open state at low cAMP, distinct from CNGA2's opening module and the feedback module.","evidence":"Site-directed mutagenesis and patch-clamp in heterologous expression","pmids":["19822638"],"confidence":"Medium","gaps":["Single lab, no independent replication cited","Module assignment inferred functionally rather than structurally"]},{"year":2011,"claim":"Whether CNGA4 directly mediates Ca2+-CaM feedback was challenged; its LQ-type CaM site bound Ca2+-CaM only at 10-fold higher Ca2+ than CNGB1, arguing feedback is the B-subunit's role.","evidence":"Recombinant domain expression and in vitro Ca2+-calmodulin binding assays","pmids":["21413724"],"confidence":"Medium","gaps":["In vitro binding contradicts earlier genetic data and was not reconciled in native channels","Single lab biochemical assay only"]},{"year":2016,"claim":"The link between ligand binding and signal termination by modulatory subunits was unresolved; CNGA4 was shown to bind cyclic nucleotides and accelerate deactivation alongside CNGB1b.","evidence":"Simultaneous fluorescence ligand-binding and patch-clamp electrophysiology in heterologous channels","pmids":["27405959"],"confidence":"Medium","gaps":["Single lab","Quantitative contribution of CNGA4 versus CNGB1b binding not separated"]},{"year":2025,"claim":"Whether CNGA4 functions outside olfaction was unknown; it was identified as the CNG subtype mediating a long rebound depolarization in lateral habenular neurons, with reduced expression in stress-susceptible mice.","evidence":"Whole-cell patch-clamp, RNA-seq, CRISPR genome editing, dye coupling and in situ hybridization","pmids":["40168081"],"confidence":"Medium","gaps":["Subunit partners of CNGA4 in habenular neurons not defined","Causal link to stress behavior not established","Novel context, single lab"]},{"year":null,"claim":"It remains unresolved how CNGA4's biochemically weak Ca2+-CaM binding reconciles with the genetically demonstrated requirement for CNGA4 in Ca2+-dependent feedback, and what structural arrangement underlies its modulatory and trafficking roles within the native heteromer.","evidence":"No timeline study resolves the contradiction or provides an atomic-resolution structure of the native heteromer","pmids":[],"confidence":"Low","gaps":["No high-resolution structure of the native CNGA2/CNGA4/CNGB1b channel","CaM-feedback contradiction between genetic and biochemical data unresolved","CNGA4 partners and function in non-olfactory neurons uncharacterized"]}],"mechanism_profile":{"molecular_activity":[],"localization":[{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[3,4]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[4]}],"pathway":[{"term_id":"R-HSA-9709957","term_label":"Sensory Perception","supporting_discovery_ids":[0,5]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[13]}],"complexes":["Olfactory CNG channel (CNGA2/CNGA4/CNGB1b)"],"partners":["CNGA2","CNGB1","KIF17","CALM1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8IV77","full_name":"Cyclic nucleotide-gated channel alpha-4","aliases":["Olfactory cyclic nucleotide-gated channel subunit 2","OCNC2"],"length_aa":575,"mass_kda":66.0,"function":"Pore-forming subunit of the olfactory cyclic nucleotide-gated channel. Operates in the cilia of olfactory sensory neurons where chemical stimulation of the odorant is converted to an electrical signal. Mediates odorant-induced cAMP-dependent Ca(2+) influx triggering neuron depolarization. The rise of intracellular Ca(2+) levels potentiates the olfactory response by activating Ca(2+)-dependent Cl(-) channels, but it also serves as a negative feedback signal to desensitize the channel for rapid adaptation to odorants. Conducts cAMP- and cGMP-gated ion currents, with permeability for monovalent and divalent cations","subcellular_location":"Cell projection, cilium membrane","url":"https://www.uniprot.org/uniprotkb/Q8IV77/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CNGA4","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/CNGA4","total_profiled":1310},"omim":[{"mim_id":"609472","title":"CYCLIC NUCLEOTIDE-GATED CHANNEL, ALPHA-4; CNGA4","url":"https://www.omim.org/entry/609472"},{"mim_id":"600724","title":"CYCLIC NUCLEOTIDE-GATED CHANNEL, BETA-1; CNGB1","url":"https://www.omim.org/entry/600724"},{"mim_id":"300338","title":"CYCLIC NUCLEOTIDE-GATED CHANNEL, ALPHA-2; CNGA2","url":"https://www.omim.org/entry/300338"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Uncertain","locations":[{"location":"Nucleoplasm","reliability":"Uncertain"},{"location":"Plasma membrane","reliability":"Uncertain"}],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"fallopian tube","ntpm":16.2},{"tissue":"testis","ntpm":5.9}],"url":"https://www.proteinatlas.org/search/CNGA4"},"hgnc":{"alias_symbol":["OCNC2","OCNCb","CNG5"],"prev_symbol":["CNCA2","CNGB2"]},"alphafold":{"accession":"Q8IV77","domains":[{"cath_id":"1.10.287","chopping":"164-280","consensus_level":"medium","plddt":91.2885,"start":164,"end":280},{"cath_id":"2.60.120.10","chopping":"327-479","consensus_level":"high","plddt":85.8421,"start":327,"end":479},{"cath_id":"1.20.58","chopping":"25-161","consensus_level":"medium","plddt":92.183,"start":25,"end":161}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IV77","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IV77-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IV77-F1-predicted_aligned_error_v6.png","plddt_mean":83.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CNGA4","jax_strain_url":"https://www.jax.org/strain/search?query=CNGA4"},"sequence":{"accession":"Q8IV77","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8IV77.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8IV77/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IV77"}},"corpus_meta":[{"pmid":"16481428","id":"PMC_16481428","title":"Essential role of the main olfactory system in social recognition of major histocompatibility complex peptide ligands.","date":"2006","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/16481428","citation_count":190,"is_preprint":false},{"pmid":"16782012","id":"PMC_16782012","title":"Ciliary targeting of olfactory CNG channels requires the CNGB1b subunit and the kinesin-2 motor protein, KIF17.","date":"2006","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/16782012","citation_count":175,"is_preprint":false},{"pmid":"8637879","id":"PMC_8637879","title":"Evidence for distinct signaling mechanisms in two mammalian olfactory sense organs.","date":"1996","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/8637879","citation_count":123,"is_preprint":false},{"pmid":"10662822","id":"PMC_10662822","title":"Molecular cloning and functional characterization of a new modulatory cyclic nucleotide-gated channel subunit from mouse retina.","date":"2000","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/10662822","citation_count":100,"is_preprint":false},{"pmid":"9539801","id":"PMC_9539801","title":"An isoform of the rod photoreceptor cyclic nucleotide-gated channel beta subunit expressed in olfactory neurons.","date":"1998","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/9539801","citation_count":97,"is_preprint":false},{"pmid":"11739959","id":"PMC_11739959","title":"Central role of the CNGA4 channel subunit in Ca2+-calmodulin-dependent odor adaptation.","date":"2001","source":"Science (New York, 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physiology","url":"https://pubmed.ncbi.nlm.nih.gov/11696610","citation_count":12,"is_preprint":false},{"pmid":"19822638","id":"PMC_19822638","title":"Activation and desensitization of the olfactory cAMP-gated transduction channel: identification of functional modules.","date":"2009","source":"The Journal of general physiology","url":"https://pubmed.ncbi.nlm.nih.gov/19822638","citation_count":12,"is_preprint":false},{"pmid":"11834291","id":"PMC_11834291","title":"Expression of subunits for the cAMP-sensitive 'olfactory' cyclic nucleotide-gated ion channel in the cochlea: implications for signal transduction.","date":"2002","source":"Brain research. Molecular brain research","url":"https://pubmed.ncbi.nlm.nih.gov/11834291","citation_count":9,"is_preprint":false},{"pmid":"21284860","id":"PMC_21284860","title":"Sodium selectivity of Reissner's membrane epithelial cells.","date":"2011","source":"BMC physiology","url":"https://pubmed.ncbi.nlm.nih.gov/21284860","citation_count":9,"is_preprint":false},{"pmid":"32174961","id":"PMC_32174961","title":"Transcriptomic Study of Porcine Small Intestine Epithelial Cells Reveals Important Genes and Pathways Associated With Susceptibility to Escherichia coli F4ac Diarrhea.","date":"2020","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/32174961","citation_count":8,"is_preprint":false},{"pmid":"32272140","id":"PMC_32272140","title":"Neuropathic and cAMP-induced pain behavior is ameliorated in mice lacking CNGB1.","date":"2020","source":"Neuropharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/32272140","citation_count":7,"is_preprint":false},{"pmid":"38236765","id":"PMC_38236765","title":"Comparative Gene Signature of Nociceptors Innervating Mouse Molar Teeth, Cranial Meninges, and Cornea.","date":"2024","source":"Anesthesia and analgesia","url":"https://pubmed.ncbi.nlm.nih.gov/38236765","citation_count":3,"is_preprint":false},{"pmid":"19823021","id":"PMC_19823021","title":"Bimodal agonism in heteromeric cyclic nucleotide-gated channels.","date":"2009","source":"Channels (Austin, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/19823021","citation_count":2,"is_preprint":false},{"pmid":"40168081","id":"PMC_40168081","title":"Neuron-non-neuron electrical coupling networks are involved in chronic stress-induced electrophysiological changes in lateral habenular neurons.","date":"2025","source":"The Journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/40168081","citation_count":1,"is_preprint":false},{"pmid":"21624949","id":"PMC_21624949","title":"Ligand-binding domain subregions contributing to bimodal agonism in cyclic nucleotide-gated channels.","date":"2011","source":"The Journal of general physiology","url":"https://pubmed.ncbi.nlm.nih.gov/21624949","citation_count":1,"is_preprint":false},{"pmid":"36584110","id":"PMC_36584110","title":"Ancient multiplicity in cyclic nucleotide-gated (CNG) cation channel repertoire was reduced in the ancestor of Olfactores before re-expansion by whole genome duplications in vertebrates.","date":"2022","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/36584110","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":17446,"output_tokens":3718,"usd":0.054054,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":11455,"output_tokens":4004,"usd":0.078687,"stage2_stop_reason":"end_turn"},"total_usd":0.132741,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2001,\n      \"finding\": \"Targeted deletion of CNGA4 in mice results in defective Ca2+-calmodulin-mediated desensitization of the olfactory CNG channel; excised membrane patches from CNGA4-null mice showed slower Ca2+-calmodulin-mediated channel desensitization, establishing that CNGA4 accelerates Ca2+-mediated negative feedback in olfactory signaling and is required for rapid odorant adaptation.\",\n      \"method\": \"Gene knockout mouse, excised membrane patch-clamp electrophysiology, Ca2+-calmodulin desensitization assay\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined cellular and electrophysiological phenotype, replicated by independent lab in same journal issue (PMID:11739960)\",\n      \"pmids\": [\"11739959\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Ca2+-calmodulin-mediated negative feedback inhibition of the olfactory CNG channel requires both modulatory subunits CNGA4 and CNGB1b in addition to the principal CNGA2 subunit; CNGA2 alone (which possesses the CaM-binding site) is insufficient for rapid Ca2+-dependent adaptation without these auxiliary subunits.\",\n      \"method\": \"Heterologous expression in Xenopus oocytes and HEK cells, patch-clamp electrophysiology, Ca2+-calmodulin feedback assays with defined subunit combinations\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — defined subunit requirement with patch-clamp, independently replicated by two labs in same journal issue (PMID:11739959 and PMID:11739960)\",\n      \"pmids\": [\"11739960\", \"11739959\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"CNGA4 (CNG4.3), cloned from rat olfactory epithelium, is an isoform of the rod photoreceptor beta subunit that lacks the N-terminal glutamic acid-rich domain; coexpression with CNGA2 increases cAMP sensitivity, weakens outward rectification in extracellular Ca2+, reduces relative Ca2+ permeability, and enhances L-cis diltiazem sensitivity. Coexpression of CNGA2 + CNGA4 + CNGB1b (CNG5) yields cAMP sensitivity near that of the native olfactory channel.\",\n      \"method\": \"Molecular cloning, heterologous expression in HEK293 cells, patch-clamp electrophysiology, ion permeability and pharmacology assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro reconstitution with multiple orthogonal electrophysiological measurements, replicated in subsequent studies\",\n      \"pmids\": [\"9539801\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Ciliary trafficking of the olfactory CNG channel (comprising CNGA2, CNGA4, CNGB1b) requires heteroassembly with CNGB1b, which contains a critical C-terminal RVxP motif; CNGA4 alone is insufficient for ciliary targeting. Additionally, the kinesin-2 motor KIF17 is required for anterograde transport of the olfactory CNG channel into cilia.\",\n      \"method\": \"Transgenic mouse models, immunofluorescence localization, dominant-negative KIF17 expression, mutagenesis of RVxP motif\",\n      \"journal\": \"Current Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct ciliary localization experiments with mutagenesis and motor protein knockdown, corroborated by independent study (PMID:16980309)\",\n      \"pmids\": [\"16782012\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"In CNGB1-deficient mice, a CNGA2/CNGA4 channel is present in the olfactory epithelium (confirmed by co-immunoprecipitation) and traffics to the plasma membrane of olfactory knobs but fails to enter olfactory cilia. A similar ciliary trafficking defect occurs in CNGA4-deficient mice, demonstrating that both CNGA4 and CNGB1 are required for ciliary targeting of the olfactory CNG channel.\",\n      \"method\": \"Gene knockout mouse, co-immunoprecipitation, immunofluorescence/confocal microscopy, electro-olfactogram, patch-clamp electrophysiology\",\n      \"journal\": \"Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, direct subcellular localization with functional consequence, two KO models tested\",\n      \"pmids\": [\"16980309\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"CNGA4-null mice are profoundly impaired in the detection and discrimination of olfactory stimuli in the presence of an adapting background odor in operant conditioning tasks, demonstrating that Ca2+-dependent CNG channel desensitization mediated by CNGA4 is essential for odor discrimination and adaptation in behaving animals.\",\n      \"method\": \"Gene knockout mouse, operant conditioning behavioral paradigm, electro-olfactogram\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined in vivo behavioral and electrophysiological phenotype\",\n      \"pmids\": [\"12649326\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Disruption of CNGA4 in mice reveals a profound defect in adaptation of MHC class I peptide-evoked field potentials in the main olfactory epithelium, showing that CNGA4 is required for adaptation to nonvolatile immune peptide olfactory cues.\",\n      \"method\": \"Gene knockout mouse, Ca2+ imaging, electro-olfactogram, behavioral preference assays\",\n      \"journal\": \"Journal of Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with multiple electrophysiological and behavioral readouts\",\n      \"pmids\": [\"16481428\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The inability of CNGA4 to form functional homomeric channels was localized to a tripeptide in its C-linker domain. This tripeptide decreases the efficacy of ligand gating by preventing cAMP-induced assembly of C-terminal domains into a tetrameric gating ring, as demonstrated by analytical ultracentrifugation showing that cAMP causes gating ring disassembly when the CNGA4 tripeptide is present.\",\n      \"method\": \"Chimeric channel mutagenesis, patch-clamp electrophysiology in Xenopus oocytes, analytical ultracentrifugation of isolated C-terminal domains\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with mutagenesis plus biophysical structural analysis (analytical ultracentrifugation) in single study\",\n      \"pmids\": [\"15572113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"The CNGA4 (CNG5/beta) subunit increases cAMP selectivity of heteromeric olfactory CNG channels primarily through its cyclic nucleotide-binding region (CNBR); a single residue (M475) in the CNBR accounts for the altered cAMP/cGMP selectivity ratio. Ligand-independent effects of CNGA4 (voltage dependence, Mg2+ block properties, desensitization) reside outside the CNBR.\",\n      \"method\": \"Chimeric subunit construction, site-directed mutagenesis (M475E), heterologous expression in Xenopus oocytes, patch-clamp electrophysiology\",\n      \"journal\": \"Biophysical Journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis with functional reconstitution in Xenopus oocytes, multiple chimeras tested\",\n      \"pmids\": [\"10777729\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Using site-directed mutagenesis and patch-clamp analysis, CNGA4 was assigned to a functional module that stabilizes the open state of the olfactory CNG channel at low cAMP concentrations (distinct from the channel-opening module in CNGA2 and the Ca2+-dependent feedback inhibition module), defining the gating logic of the olfactory transduction channel.\",\n      \"method\": \"Site-directed mutagenesis, patch-clamp electrophysiology, heterologous expression\",\n      \"journal\": \"Journal of General Physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis with electrophysiology, single lab, well-controlled but no independent replication cited\",\n      \"pmids\": [\"19822638\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The LQ-type calmodulin-binding site of CNGA4 binds Ca2+-calmodulin at 10-fold higher Ca2+ concentrations than the corresponding site on CNGB1, providing biochemical evidence against a primary role for CNGA4 in Ca2+-calmodulin feedback inhibition; the data suggest feedback control is the exclusive role of B-subunits.\",\n      \"method\": \"Recombinant protein expression, in vitro Ca2+-calmodulin binding assays (biochemical)\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct in vitro binding assay with recombinant domains, single lab, contradicts earlier genetic evidence (PMID:11739959); moderate uncertainty due to contradiction\",\n      \"pmids\": [\"21413724\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The cyclic nucleotide-binding domain (BD) of CNGA4 (beta/CNG5 subunit), when placed in a chimeric subunit with alpha-subunit transmembrane domains, can couple ligand binding to channel opening with higher opening efficacy and lower K1/2 than the corresponding alpha-subunit BD; both the roll subdomain and C-helix subdomain of CNGA4's BD contribute to this enhanced efficacy.\",\n      \"method\": \"Chimeric subunit construction (X-beta chimera), heterologous expression in Xenopus oocytes, excised patch-clamp, thermodynamic linkage analysis\",\n      \"journal\": \"Journal of General Physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro reconstitution with chimeric subunits and functional electrophysiology, single lab\",\n      \"pmids\": [\"11696610\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"In heterotetrameric olfactory CNG channels, the CNGA4 subunit (alongside CNGB1b) binds cyclic nucleotides and accelerates channel deactivation; both modulatory subunits contribute to rapid termination of the odorant signal, as shown by simultaneous ligand-binding and channel-activation measurements.\",\n      \"method\": \"Simultaneous fluorescence ligand-binding and patch-clamp electrophysiology, heterologous expression\",\n      \"journal\": \"Scientific Reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — orthogonal simultaneous binding/gating measurements, single lab\",\n      \"pmids\": [\"27405959\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In lateral habenular neurons, the long depolarizing phase of rebound depolarizing potentials is mediated by CNG channels activated via electrical coupling between neurons and non-neuronal cells (oligodendrocytes/OPCs); RNA-sequencing and genome editing experiments identified Cnga4 as the primary CNG channel subtype responsible for this long depolarization, and Cnga4 expression is decreased in stress-susceptible mice.\",\n      \"method\": \"Whole-cell patch-clamp, RNA-sequencing, CRISPR/genome editing, gap junction dye coupling, in situ hybridization\",\n      \"journal\": \"Journal of Physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — genome editing with electrophysiological phenotype, single lab, novel context\",\n      \"pmids\": [\"40168081\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"The CNGA4 (oCNC2/CNG5) subunit mRNA is expressed in vomeronasal organ (VNO) sensory neurons but not in main olfactory epithelium neurons (which express the oCNC1/CNGA2 subunit), indicating distinct CNG channel subunit composition in the two olfactory organs.\",\n      \"method\": \"In situ hybridization, Northern blot analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — expression localization only, no functional mechanism established for CNGA4 specifically\",\n      \"pmids\": [\"8637879\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CNGA4 is a modulatory subunit of the native heteromeric olfactory CNG channel (assembled as 2×CNGA2 + CNGA4 + CNGB1b), where it stabilizes the open state at low cAMP concentrations, accelerates Ca2+-calmodulin-mediated channel desensitization to enable rapid odorant adaptation, and—together with CNGB1b—is required for ciliary trafficking of the channel complex; its inability to form homomeric channels is attributable to a C-linker tripeptide that prevents ligand-induced gating-ring assembly.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CNGA4 is a modulatory subunit of the heteromeric olfactory cyclic-nucleotide-gated (CNG) channel that shapes the speed, sensitivity, and adaptation of odorant transduction in olfactory sensory neurons [#2, #5]. It cannot form functional homomeric channels: a tripeptide in its C-linker prevents cAMP from driving assembly of the C-terminal domains into a tetrameric gating ring, abolishing ligand-induced gating in the homomer [#7]. When coassembled with the principal CNGA2 subunit and CNGB1b, CNGA4 contributes its cyclic-nucleotide-binding region to tune the channel's cAMP selectivity and sensitivity toward the native olfactory phenotype, with a single CNBR residue (M475) setting the cAMP/cGMP selectivity ratio [#2, #8], and it stabilizes the channel open state at low cAMP [#9]. CNGA4 accelerates Ca2+-calmodulin-mediated desensitization and deactivation of the channel, providing the rapid negative feedback required for odorant adaptation and for discrimination against an adapting background, both at the level of channel kinetics and of animal behavior [#0, #1, #5, #12]. Together with CNGB1b, CNGA4 is also required for ciliary trafficking of the assembled channel: in CNGA4-deficient mice the channel reaches the plasma membrane of olfactory knobs but fails to enter the cilia [#3, #4]. Beyond olfaction, CNGA4 has been identified as the CNG subunit underlying a long rebound depolarization in lateral habenular neurons [#13].\"\n,\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Before any function was assigned, it was unknown where the CNGA4 subunit was expressed; establishing its restricted sensory expression framed it as an olfactory channel component.\",\n      \"evidence\": \"In situ hybridization and Northern blot across olfactory tissues\",\n      \"pmids\": [\"8637879\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Expression localization only, no functional mechanism established\", \"Reported VNO-restricted expression, leaving its role in main olfactory epithelium open\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"It was unclear what CNGA4 contributes to the channel; reconstitution showed it modulates cAMP sensitivity, rectification, Ca2+ permeability and pharmacology, and that the CNGA2+CNGA4+CNGB1b combination reproduces native cAMP sensitivity.\",\n      \"evidence\": \"Molecular cloning and heterologous expression in HEK293 with patch-clamp, ion permeability and pharmacology assays\",\n      \"pmids\": [\"9539801\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve which structural element confers each property\", \"Native subunit stoichiometry not defined\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"The structural basis of CNGA4's effect on ligand selectivity was unknown; mutagenesis localized cAMP selectivity to the CNBR and a single residue (M475), separating ligand-dependent from ligand-independent effects.\",\n      \"evidence\": \"Chimeric subunits and M475E site-directed mutagenesis with patch-clamp in Xenopus oocytes\",\n      \"pmids\": [\"10777729\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not localize the desensitization and voltage-dependent effects to specific residues\", \"Conducted in heterologous chimeras rather than native channels\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Whether CNGA4 contributes to gating efficacy was unresolved; chimera analysis showed its binding domain couples ligand binding to opening more efficaciously than the alpha-subunit domain.\",\n      \"evidence\": \"X-beta chimeric subunits, excised patch-clamp and thermodynamic linkage analysis in oocytes\",\n      \"pmids\": [\"11696610\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab, chimeric context\", \"Did not test contribution within the full native heteromer\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"The molecular requirement for rapid olfactory adaptation was unknown; knockout and reconstitution established that CNGA4 (with CNGB1b) is required for Ca2+-calmodulin-mediated desensitization that CNGA2 alone cannot provide.\",\n      \"evidence\": \"CNGA4-null mice, excised patch-clamp, and defined subunit reconstitution in oocytes/HEK with Ca2+-CaM feedback assays, replicated by two labs\",\n      \"pmids\": [\"11739959\", \"11739960\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the CaM-binding site driving feedback\", \"Mechanism of how an auxiliary subunit accelerates CaM action left open\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"It was unclear whether channel-level adaptation translated to behavior; CNGA4-null mice were profoundly impaired in odor discrimination and adaptation against a background odor.\",\n      \"evidence\": \"CNGA4 knockout mice in operant conditioning and electro-olfactogram\",\n      \"pmids\": [\"12649326\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Behavioral deficit not dissected from possible developmental or trafficking contributions\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Why CNGA4 cannot form homomeric channels was unknown; the defect was localized to a C-linker tripeptide that blocks cAMP-induced gating-ring assembly.\",\n      \"evidence\": \"Chimeric mutagenesis with patch-clamp plus analytical ultracentrifugation of isolated C-terminal domains\",\n      \"pmids\": [\"15572113\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural detail of how the tripeptide perturbs the gating ring at atomic resolution not resolved\", \"Single study\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"The route by which the olfactory channel reaches cilia was unknown; CNGA4 and CNGB1b were both shown to be required for ciliary targeting, with KIF17-dependent anterograde transport.\",\n      \"evidence\": \"Transgenic and knockout mice, co-immunoprecipitation, immunofluorescence, RVxP mutagenesis and dominant-negative KIF17\",\n      \"pmids\": [\"16782012\", \"16980309\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The specific contribution of CNGA4 versus CNGB1b to the trafficking signal not separated\", \"Direct interaction of CNGA4 with the transport machinery not shown\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Whether CNGA4-dependent adaptation extended to nonvolatile cues was untested; knockout mice showed defective adaptation to MHC class I peptide-evoked responses.\",\n      \"evidence\": \"CNGA4 knockout mice with Ca2+ imaging, electro-olfactogram and behavioral preference assays\",\n      \"pmids\": [\"16481428\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor/transduction pathway upstream of the CNG channel for peptide cues not defined\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"The gating logic of the heteromeric channel was unclear; CNGA4 was assigned to a module that stabilizes the open state at low cAMP, distinct from CNGA2's opening module and the feedback module.\",\n      \"evidence\": \"Site-directed mutagenesis and patch-clamp in heterologous expression\",\n      \"pmids\": [\"19822638\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab, no independent replication cited\", \"Module assignment inferred functionally rather than structurally\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Whether CNGA4 directly mediates Ca2+-CaM feedback was challenged; its LQ-type CaM site bound Ca2+-CaM only at 10-fold higher Ca2+ than CNGB1, arguing feedback is the B-subunit's role.\",\n      \"evidence\": \"Recombinant domain expression and in vitro Ca2+-calmodulin binding assays\",\n      \"pmids\": [\"21413724\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vitro binding contradicts earlier genetic data and was not reconciled in native channels\", \"Single lab biochemical assay only\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"The link between ligand binding and signal termination by modulatory subunits was unresolved; CNGA4 was shown to bind cyclic nucleotides and accelerate deactivation alongside CNGB1b.\",\n      \"evidence\": \"Simultaneous fluorescence ligand-binding and patch-clamp electrophysiology in heterologous channels\",\n      \"pmids\": [\"27405959\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Quantitative contribution of CNGA4 versus CNGB1b binding not separated\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Whether CNGA4 functions outside olfaction was unknown; it was identified as the CNG subtype mediating a long rebound depolarization in lateral habenular neurons, with reduced expression in stress-susceptible mice.\",\n      \"evidence\": \"Whole-cell patch-clamp, RNA-seq, CRISPR genome editing, dye coupling and in situ hybridization\",\n      \"pmids\": [\"40168081\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Subunit partners of CNGA4 in habenular neurons not defined\", \"Causal link to stress behavior not established\", \"Novel context, single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how CNGA4's biochemically weak Ca2+-CaM binding reconciles with the genetically demonstrated requirement for CNGA4 in Ca2+-dependent feedback, and what structural arrangement underlies its modulatory and trafficking roles within the native heteromer.\",\n      \"evidence\": \"No timeline study resolves the contradiction or provides an atomic-resolution structure of the native heteromer\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No high-resolution structure of the native CNGA2/CNGA4/CNGB1b channel\", \"CaM-feedback contradiction between genetic and biochemical data unresolved\", \"CNGA4 partners and function in non-olfactory neurons uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005216\", \"supporting_discovery_ids\": [2, 9, 12]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [3, 4]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9709957\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [13]}\n    ],\n    \"complexes\": [\"Olfactory CNG channel (CNGA2/CNGA4/CNGB1b)\"],\n    \"partners\": [\"CNGA2\", \"CNGB1\", \"KIF17\", \"CALM1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}