Affinage

CNGA1

Cyclic nucleotide-gated channel alpha-1 · UniProt P29973

Length
686 aa
Mass
79.1 kDa
Annotated
2026-06-09
35 papers in source corpus 15 papers cited in narrative 15 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 9/9 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

CNGA1 is the principal pore-forming alpha subunit of the rod photoreceptor cyclic nucleotide-gated (CNG) cation channel, the effector that transduces light-driven changes in cGMP into membrane current (PMID:33651975, PMID:34418172). It assembles as a homotetramer in heterologous systems and as a 3:1 heterotetramer with CNGB1 in native rods, where the three CNGA1 subunits are tethered at their C-termini through a coiled-coil region while the incorporated CNGB1 subunit contributes an additional pore gate (via residue R994) distinct from the central hydrophobic gate of homomeric channels (PMID:34969975). Unlike most voltage-gated tetrameric cation channels, CNGA1 positions its activation gate in the middle of the membrane, occluding the central cavity, and opens upon cGMP binding to its C-terminal cyclic nucleotide-binding domain (PMID:33651975). Gating is modular: intersubunit and intrasubunit salt bridges in the C-linker stabilize the closed state, so that the CNBD can adopt a ligand-bound configuration while the C-linker remains at rest, and breaking these bridges favors opening (PMID:15572346). The selectivity filter defines two intrapore Ca2+ binding sites underlying Ca2+ block and permeation, and the wild-type filter architecture has evolved to suppress an inherent voltage-dependent gating mode so that cGMP binding alone suffices to open the channel at physiological voltages (PMID:33651975, PMID:19635856). Consistent with this, CNGA1 moves fewer than two elementary gating charges across the membrane and is poorly voltage-sensitive under physiological conditions (PMID:24400150). Loss of CNGA1 causes progressive rod and cone degeneration: knockout mice develop a retinitis pigmentosa-like phenotype with down-regulated phototransduction and synaptic transmission and engagement of autophagic pathways (PMID:34418172), and pathogenic missense variants act by retaining the protein intracellularly and depleting it from the plasma membrane (PMID:26802146). AAV-mediated CNGA1 gene augmentation restores correctly localized protein, rod function, and photoreceptor survival, establishing that CNGA1 restoration is sufficient for rescue (PMID:40897815). A distinct pool of CNGA1 functions outside the retina, mediating the amiloride-insensitive component of cGMP-stimulated lung liquid reabsorption in alveolar type I cells (PMID:21559843).

Mechanistic history

Synthesis pass · year-by-year structured walk · 13 steps
  1. 2003 Medium

    Establishing where blockers bind within the conduction pathway clarified the architecture of the open pore and provided a pharmacological tool to distinguish homomeric from heteromeric channels.

    Evidence Inside-out/outside-out patch clamp with dequalinium block of CNGA1 and CNGA1+CNGB1 in Xenopus oocytes

    PMID:12508052

    Open questions at the time
    • Blocker binding site not resolved at atomic resolution
    • Functional consequence of differential CNGB1 sensitivity in native rods not addressed
  2. 2004 High

    Identifying C-linker salt bridges that stabilize the closed state revealed that ligand binding and gate opening are mechanically separable, defining a modular allosteric gating scheme.

    Evidence Charge-swap mutagenesis with functional rescue in CNGA1 and HCN2 expressed in Xenopus oocytes; electrophysiology

    PMID:15572346

    Open questions at the time
    • Did not resolve the structural transition coupling CNBD to the membrane gate
    • Quantitative energetic contribution of each bridge not fully partitioned
  3. 2004 Medium

    Single-channel analysis showed cGMP and permeant ions jointly shape pore conformational fluctuations, linking ligand occupancy and ion occupancy to gating behavior.

    Evidence Single-channel and macroscopic patch-clamp from CNGA1 in Xenopus oocytes varying cGMP and permeant ion species

    PMID:15308684

    Open questions at the time
    • Structural basis of ion-dependent fluctuations not defined
    • Single lab
  4. 2009 High

    Mutations around the selectivity filter that rendered the channel fully voltage-gated demonstrated that the wild-type filter architecture actively suppresses intrinsic voltage sensitivity, explaining why cGMP alone opens the channel physiologically.

    Evidence Selectivity filter region mutagenesis with patch-clamp in Xenopus oocytes

    PMID:19635856

    Open questions at the time
    • Did not provide the atomic structure of the filter in open and closed states
    • Coupling between filter and central gate not directly observed
  5. 2011 Medium

    Identifying CNGA1 in alveolar type I cells and its pharmacological control of fluid clearance extended its role beyond phototransduction to epithelial liquid transport.

    Evidence Protein expression profiling, in situ rat lung liquid clearance with PsTx/L-cis-diltiazem/amiloride, and patch-clamp validation in HEK293 cells

    PMID:21559843

    Open questions at the time
    • cGMP source and upstream signaling in alveolar cells not defined
    • Physiological relevance to human lung not tested
  6. 2013 Medium

    Gating current measurements quantified that CNGA1 moves fewer than two charges with weak S4-to-gate coupling, mechanistically explaining its poor physiological voltage sensitivity.

    Evidence Tail and gating current recordings with S4 charge mutagenesis and multiple permeant ions in Xenopus oocytes

    PMID:24400150

    Open questions at the time
    • Structural motion of S4 not visualized
    • Two voltage-dependent transitions not fully assigned to structural elements
  7. 2016 Medium

    Demonstrating that a pathogenic missense variant traps CNGA1 intracellularly established loss of plasma membrane targeting as a disease mechanism in autosomal recessive retinitis pigmentosa.

    Evidence Heterologous expression of WT and p.G513R CNGA1 in HEK293 cells; western blot and immunofluorescence

    PMID:26802146

    Open questions at the time
    • No electrophysiology to confirm channel function loss
    • Trafficking defect studied in heterologous cells, not rods
  8. 2019 Low

    A second trafficking-defective missense variant reinforced reduced plasma-membrane expression as a recurring pathogenic theme.

    Evidence Expression of WT and p.D208N CNGA1 in HEK293T cells; western blot and immunofluorescence

    PMID:30652268

    Open questions at the time
    • No functional electrophysiology
    • Single lab, single heterologous system
    • S2-S4 interaction loss inferred, not structurally confirmed
  9. 2021 High

    Cryo-EM of human CNGA1 in apo-closed and cGMP-bound open states defined a mid-membrane central gate and two intrapore Ca2+ sites, providing the structural framework for ligand gating and ion permeation.

    Evidence Cryo-EM of apo and cGMP-bound CNGA1 with E365Q selectivity filter mutagenesis and ion binding analysis

    PMID:33651975

    Open questions at the time
    • Dynamics of the gating transition not captured
    • Structures of homomeric channel may differ from native heteromer
  10. 2021 High

    Cryo-EM of the native bovine 3:1 CNGA1-CNGB1 channel revealed C-terminal coiled-coil tethering and a CNGB1-specific second pore gate, defining how the native rod channel differs from the homomer.

    Evidence Cryo-EM of native bovine retinal rod CNG channel with subunit-resolved analysis

    PMID:34969975

    Open questions at the time
    • Open-state structure of the heteromer not resolved
    • Functional role of the CNGB1 R994 gate not directly tested
  11. 2021 Medium

    A CRISPR knockout mouse causally linked CNGA1 loss to progressive photoreceptor degeneration and identified early down-regulated phototransduction and autophagy engagement as molecular correlates of cell death.

    Evidence CRISPR/Cas9 Cnga1 knockout mice with ERG, immunofluorescence, TUNEL, and RNA-seq

    PMID:34418172

    Open questions at the time
    • Causal role of autophagy/PI3K-AKT-mTOR changes in death not tested
    • Cone degeneration mechanism downstream of rod loss not defined
  12. 2025 Medium

    AAV8 gene augmentation rescued rod function and photoreceptor survival in knockout mice, establishing that restoring CNGA1 alone is sufficient and providing therapeutic proof of concept.

    Evidence AAV8 subretinal delivery of mCnga1 in Cnga1-/- mice; ERG, immunofluorescence, vision-guided behavior, RNA-seq

    PMID:40897815

    Open questions at the time
    • Durability beyond 9 months and large-animal/human efficacy not shown
    • Optimal therapeutic window relative to degeneration stage not defined
  13. 2026 Medium

    A medium-throughput functional assay across 86 missense variants enabled large-scale variant classification and revealed that some apparent missense changes act through missplicing.

    Evidence Aequorin-based cation flux assay, minigene splice assays, and in silico predictor correlation

    PMID:42192302

    Open questions at the time
    • Assay measures function in heterologous cells, not native rods
    • Trafficking versus gating defects not distinguished for each variant

Open questions

Synthesis pass · forward-looking unresolved questions
  • How allosteric coupling between the selectivity filter and the central cavity gate generates the channel's characteristic flicker and residual voltage sensitivity awaits direct experimental confirmation.
  • MD-predicted hydration fluctuations at the gate not experimentally validated
  • No time-resolved structural data on the gating transition
  • Coupling mechanism inferred computationally

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005215 transporter activity 3 GO:0060089 molecular transducer activity 3
Localization
GO:0005886 plasma membrane 3 GO:0005929 cilium 2
Pathway
R-HSA-162582 Signal Transduction 2 R-HSA-9709957 Sensory Perception 2 R-HSA-382551 Transport of small molecules 1
Partners
CNGB1
Complex memberships
Rod CNG channel (CNGA1/CNGB1 heterotetramer)

Evidence

Reading pass · 15 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2021 Cryo-EM structures of human CNGA1 in both apo closed and cGMP-bound open states reveal that CNGA1 forms a central channel gate in the middle of the membrane (occluding the central cavity), distinct from most other voltage-gated tetrameric cation channels. Structural analysis of the wild-type channel and the E365Q selectivity filter mutant defined two Ca2+ binding sites inside the selectivity filter, providing a structural basis for Ca2+ blockage and permeation. The E365Q mutant also revealed two alternative side-chain conformations at Q365, explaining voltage-dependent gating acquired upon E365 mutation. Cryo-EM structure determination of apo and cGMP-bound states; E365Q active-site mutagenesis; ion binding profile analysis Neuron High 33651975
2021 Cryo-EM structure of the native heterotetrameric bovine rod CNG channel (3 CNGA1 + 1 CNGB1) in the closed state shows that three CNGA1 subunits are tethered at their C-termini by a coiled-coil region. The CNGB1 subunit has a differently oriented C-helix in its CNBD compared to the three CNGA1 subunits, and CNGB1 residue R994 reaches into the ionic pathway to introduce an additional pore gate distinct from the central hydrophobic gate of homomeric CNGA1 channels. Cryo-EM structure of native bovine retinal rod CNG channel; subunit-resolved structural analysis Nature structural & molecular biology High 34969975
2004 Two salt bridges in the C-linker region of CNGA1 (an intersubunit bridge between neighboring C-linkers, and an intrasubunit bridge between the C-linker and its CNBD) stabilize a closed channel conformation. Breaking these salt bridges by mutation increases the favorability of channel opening; swapping the charged residues restores wild-type behavior. This indicates that in CNGA1, the CNBD can be in a ligand-activated configuration while the C-linker remains in the resting configuration, suggesting a modular gating scheme. Site-directed mutagenesis of salt bridge residues in CNGA1 (and HCN2) expressed in Xenopus oocytes; electrophysiology The Journal of general physiology High 15572346
2009 Mutations restricted to the region around the ion selectivity filter of CNGA1 render channels essentially fully voltage-gated even in saturating cGMP, with channels remaining mostly closed at physiological voltages. This voltage-dependent gating resembles the selectivity filter-based mechanism of KcsA K+ channels. The mutations loosen the attachment of the selectivity filter to its surrounding structure, shifting gating equilibrium toward closed states. The wild-type structure surrounding the selectivity filter has evolved to suppress inherent voltage-dependent gating, ensuring cGMP binding alone suffices to open the channel. Site-directed mutagenesis of selectivity filter region; patch-clamp electrophysiology in Xenopus oocytes The Journal of general physiology High 19635856
2004 In homotetrameric CNGA1 channels, at saturating cGMP concentrations, current levels distribute around a single mean with long open times. At low cGMP, current levels become heterogeneous (smaller, equal, or larger than saturating cGMP levels) with short open times. Ions that stay longer in the pore (generating larger single-channel currents) increase heterogeneity of current levels and decrease open probability and open times, suggesting that cGMP and permeating ions jointly modulate the extent and frequency of conformational fluctuations of the channel pore. Single-channel and macroscopic patch-clamp recordings from CNGA1 channels expressed in Xenopus oocytes; varying cGMP concentrations and permeant ion species The Journal of physiology Medium 15308684
2013 Using tail and gating current measurements from homotetrameric CNGA1 channels expressed in Xenopus oocytes, two distinct mechanisms underlie rectification: (1) single-channel current rectification in symmetrical Rb+ and Cs+ dominating macroscopic currents, and (2) voltage-dependent gating becoming prominent with larger organic cations (ethylammonium, dimethylammonium). Isochronal tail current analysis revealed at least two voltage-dependent transitions; only the first is sensitive to S4 helix charge mutations. The number of elementary charges per channel moving across the membrane is less than 2 (vs ~12 in K+ channels), indicating a restricted S4 motion with inefficient coupling to the channel gate that renders CNGA1 poorly sensitive to voltage under physiological conditions. Tail and gating current recordings from CNGA1 in Xenopus oocytes; S4 charge mutagenesis; multiple permeant ion species Physiological reports Medium 24400150
2003 Dequalinium (an organic divalent cation) blocks CNGA1 channels from the intracellular side with K1/2 ~190 nM (at 0 mV) in a state-independent, voltage-dependent manner (zdelta ~1), occupying a binding site within the ion-conducting pathway. At the single-channel level, dequalinium acts as a slow blocker without changing unitary conductance. CNGA1+CNGB1 heteromeric channels show reduced sensitivity (K1/2 ~385 nM). Extracellular dequalinium also blocks but with voltage dependence suggesting it crosses the membrane to act from the inside. Inside-out and outside-out patch clamp from Xenopus oocytes expressing CNGA1 or CNGA1+CNGB1; single-channel recordings; concentration-response analysis The Journal of general physiology Medium 12508052
2016 A missense mutation c.1537G>A (p.G513R) in CNGA1 causes the mutant protein to be largely retained inside the cell rather than being targeted to the plasma membrane, as shown by in vitro expression in HEK293 cells. This suggests that loss of CNGA1 from the plasma membrane underlies the pathogenic mechanism in this form of autosomal recessive retinitis pigmentosa. In vitro expression of Flag-tagged wild-type and mutant CNGA1 in HEK293 cells; western blot; immunofluorescence localization Bioscience reports Medium 26802146
2019 The missense mutation c.622G>A (p.D208N) in CNGA1, predicted to eliminate interactions between transmembrane segments S2 and S4, significantly reduces expression of CNGA1 protein, particularly at the plasma membrane of transfected HEK293T cells. Expression of Flag-tagged wild-type and G622A mutant CNGA1 in HEK293T cells; western blot; immunofluorescence Biochemical genetics Low 30652268
2011 CNGA1 (but not CNGA2 or CNGA3) is expressed principally in rat alveolar type I cells at the protein level. Activation of CNG channels with 8Br-cGMP stimulates lung liquid absorption ~1.8-fold in a rat in situ lung liquid clearance assay; this stimulation is abolished by the CNGA1-specific inhibitor pseudechetoxin (PsTx) or L-cis-diltiazem, but not by amiloride. Patch-clamp confirmed CNGA1 channels in HEK293 cells are not inhibited by amiloride and ENaC is not inhibited by PsTx. Thus CNGA1 channels in alveolar type I cells underlie the amiloride-insensitive component of lung liquid reabsorption. RT-PCR and protein expression profiling; in situ rat lung liquid clearance assay with pharmacological inhibitors; patch-clamp of recombinant CNGA1 and ENaC in HEK293 cells Pflugers Archiv : European journal of physiology Medium 21559843
2012 CNG-A1 is localized at the basolateral membrane of proximal and distal tubules of rat renal cortex. Ovariectomy decreases CNG-A1 expression in the renal cortex, and 17β-estradiol benzoate replacement restores CNG-A1 expression to control levels, whereas progesterone replacement does not. This indicates estrogen, but not progesterone, modulates CNGA1 expression in renal cortex. Immunofluorescence localization in rat kidney; western blot of ovariectomized and hormone-replaced rats Cellular physiology and biochemistry Low 22759964
2021 CNGA1 knockout mice (generated by CRISPR/Cas9) show progressive retinal thinning, rod and cone degeneration, and functional deficits consistent with retinitis pigmentosa. RNA-sequencing of retinae revealed down-regulated synaptic transmission and phototransduction pathways as early as postnatal day 9, down-regulation of the PI3K-AKT-mTOR pathway indicating upregulation of autophagic processes, and chaperone-mediated autophagy coinciding with the time course of photoreceptor death. CRISPR/Cas9 knockout mouse model; ERG; immunofluorescence; TUNEL staining; RNA-sequencing; pathway analysis FASEB journal Medium 34418172
2025 AAV8-mediated subretinal delivery of mCnga1 driven by the rhodopsin promoter in Cnga1-/- mice results in correctly localized CNGA1 protein expression, sustained rescue of rod-mediated retinal function, long-term photoreceptor preservation for at least 9 months, improved vision-guided behavior, and upregulation of phototransduction-associated genes by RNA-seq. This demonstrates that CNGA1 restoration is sufficient to rescue rod photoreceptor function and survival. AAV8 gene augmentation in Cnga1-/- mice; ERG; immunofluorescence; vision-guided behavior assay; RNA-seq Communications medicine Medium 40897815
2026 A medium-throughput aequorin-based functional assay of 86 CNGA1 missense variants showed that 72.1% significantly impaired CNG channel function (classified as functionally abnormal) and 23.3% were functionally normal. Two putative missense variants were shown by in vitro minigene splice assays to induce missplicing rather than amino acid change. AlphaMissense and CPT-1 in silico predictors best correlated with functional outcomes. Functional data enabled reclassification of 62.1% of VUS as likely pathogenic or likely benign. Aequorin-based medium-throughput cation flux assay for CNGA1 channel function; in vitro minigene splice assays; correlation with in silico predictors Molecular medicine Medium 42192302
2024 Large-scale atomistic MD simulations of homotetrameric CNGA1 under transmembrane voltages reveal that monovalent cation permeation involves hydrated cations in the selectivity filter. Hydration fluctuations in the central gate region, driven by pore flexibility, are proposed as the mechanism for excess single-channel conductance noise and characteristic flickering. An allosteric coupling between the selectivity filter and the central cavity gate is proposed as the mechanism for intrinsic voltage sensitivity of the pore. Atomistic molecular dynamics simulations under transmembrane voltage; analysis of cation hydration and pore dynamics bioRxivpreprint Low bio_10.1101_2024.12.19.629380

Source papers

Stage 0 corpus · 35 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2004 Salt bridges and gating in the COOH-terminal region of HCN2 and CNGA1 channels. The Journal of general physiology 121 15572346
2001 DNA variation at the rp49 gene region of Drosophila simulans: evolutionary inferences from an unusual haplotype structure. Genetics 87 11454763
2014 Whole exome analysis identifies frequent CNGA1 mutations in Japanese population with autosomal recessive retinitis pigmentosa. PloS one 58 25268133
2021 Structural mechanisms of gating and selectivity of human rod CNGA1 channel. Neuron 51 33651975
2005 Isolation of a fragment homologous to the rp49 constitutive gene of Drosophila in the Neotropical malaria vector Anopheles aquasalis (Diptera: Culicidae). Memorias do Instituto Oswaldo Cruz 45 16302065
1999 Molecular population genetics of the rp49 gene region in different chromosomal inversions of Drosophila subobscura. Genetics 42 9872959
1998 Molecular and chromosomal phylogeny in the obscura group of Drosophila inferred from sequences of the rp49 gene region. Molecular phylogenetics and evolution 41 9479691
1988 Nucleotide sequence comparison of the rp49 gene region between Drosophila subobscura and D. melanogaster. Molecular biology and evolution 30 3136296
1995 Expression of the olfactory cyclic nucleotide gated channel (CNG1) in the rat brain. Neuroreport 28 7488748
1993 Transfer of genetic information in the rp49 region of Drosophila subobscura between different chromosomal gene arrangements. Proceedings of the National Academy of Sciences of the United States of America 24 8367467
2005 Identification and characterization of a putative cyclic nucleotide-gated channel, CNG-1, in C. elegans. Molecules and cells 23 15750353
2021 The structure of the native CNGA1/CNGB1 CNG channel from bovine retinal rods. Nature structural & molecular biology 22 34969975
2009 Mutations reveal voltage gating of CNGA1 channels in saturating cGMP. The Journal of general physiology 22 19635856
2015 Progressive retinal atrophy in Shetland sheepdog is associated with a mutation in the CNGA1 gene. Animal genetics 21 26202106
2004 Autosomal recessive retinitis pigmentosa in a Pakistani family mapped to CNGA1 with identification of a novel mutation. Molecular vision 21 15570217
2016 Novel compound heterozygous mutation in the CNGA1 gene underlie autosomal recessive retinitis pigmentosa in a Chinese family. Bioscience reports 20 26802146
1993 Nucleotide divergence of the rp49 gene region between Drosophila melanogaster and two species of the Obscura group of Drosophila. Journal of molecular evolution 19 8483162
1990 Evidence of extensive genetic exchange in the rp49 region among polymorphic chromosome inversions in Drosophila subobscura. Genetics 18 2123162
2012 Role of estrogen and progesterone in the modulation of CNG-A1 and Na/K+-ATPase expression in the renal cortex. Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology 16 22759964
2011 Alveolar epithelial CNGA1 channels mediate cGMP-stimulated, amiloride-insensitive, lung liquid absorption. Pflugers Archiv : European journal of physiology 14 21559843
2004 Effects of permeating ions and cGMP on gating and conductance of rod-type cyclic nucleotide-gated (CNGA1) channels. The Journal of physiology 14 15308684
2022 Mutations within the cGMP-binding domain of CNGA1 causing autosomal recessive retinitis pigmentosa in human and animal model. Cell death discovery 13 36115851
2021 Retinal degeneration in mice lacking the cyclic nucleotide-gated channel subunit CNGA1. FASEB journal : official publication of the Federation of American Societies for Experimental Biology 12 34418172
2021 Genome-wide Association Analysis Across 16,956 Patients Identifies a Novel Genetic Association Between BMP6, NIPAL1, CNGA1 and Spondylosis. Spine 11 33332786
2013 Multiple mechanisms underlying rectification in retinal cyclic nucleotide-gated (CNGA1) channels. Physiological reports 11 24400150
2019 A Novel CNGA1 Gene Mutation (c.G622A) of Autosomal Recessive Retinitis Pigmentosa Leads to the CNGA1 Protein Reduction on Membrane. Biochemical genetics 10 30652268
2003 Dequalinium: a novel, high-affinity blocker of CNGA1 channels. The Journal of general physiology 10 12508052
2021 A case of retinitis pigmentosa homozygous for a rare CNGA1 causal variant. Scientific reports 8 33633220
2016 The cyclic nucleotide gated channel subunit CNG-1 instructs behavioral outputs in Caenorhabditis elegans by coincidence detection of nutritional status and olfactory input. Neuroscience letters 7 27561605
1990 Overproduction and translational regulation of rp49 ribosomal protein mRNA in transgenic Drosophila carrying extra copies of the gene. Molecular & general genetics : MGG 6 2370846
2020 Identification of a novel homozygous variant in the CNGA1 gene in a Chinese family with autosomal recessive retinitis pigmentosa. Molecular medicine reports 4 32705276
2024 Establishment of the induced pluripotent stem cell line SJTUGHi002-A from a CNGA1-related recessive retinitis pigmentosa patient. Stem cell research 1 38340451
2026 Systematic functional evaluation of CNGA1 missense variants associated with retinitis pigmentosa. Molecular medicine (Cambridge, Mass.) 0 42192302
2025 Generation of a human iPSC line (BTHBIOi001-A) from a retinitis pigmentosa patient with CNGA1 gene mutation. Stem cell research 0 40795580
2025 Gene augmentation therapy restores vision and preserves photoreceptors in a mouse model of CNGA1-retinitis pigmentosa. Communications medicine 0 40897815

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