Genetic Variant in Nicotinic Receptor α4-Subunit Causes Sleep-Related Hyperkinetic Epilepsy via Increased Channel Opening
We describe genetic and molecular-level functional alterations in the α4β2 neuronal nicotinic acetylcholine receptor (nAChR) from a patient with sleep-related hyperkinetic epilepsy and a family history of epilepsy. Genetic sequencing revealed a heterozygous variant c.851C>G in the <i>CHRNA4...
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MDPI AG
2022-10-01
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| Series: | International Journal of Molecular Sciences |
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| Online Access: | https://www.mdpi.com/1422-0067/23/20/12124 |
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| author | Simone Mazzaferro Deborah J. Msekela Edward C. Cooper Atul Maheshwari Steven M. Sine |
| author_facet | Simone Mazzaferro Deborah J. Msekela Edward C. Cooper Atul Maheshwari Steven M. Sine |
| author_sort | Simone Mazzaferro |
| collection | DOAJ |
| description | We describe genetic and molecular-level functional alterations in the α4β2 neuronal nicotinic acetylcholine receptor (nAChR) from a patient with sleep-related hyperkinetic epilepsy and a family history of epilepsy. Genetic sequencing revealed a heterozygous variant c.851C>G in the <i>CHRNA4</i> gene encoding the α4 subunit, resulting in the missense mutation p.Ser284Trp. Patch clamp recordings from genetically engineered nAChRs incorporating the α4-Ser284Trp subunit revealed aberrant channel openings in the absence of agonist and markedly prolonged openings in its presence. Measurements of single channel current amplitude distinguished two pentameric stoichiometries of the variant nAChR containing either two or three copies of the α4-Ser284Trp subunit, each exhibiting aberrant spontaneous and prolonged agonist-elicited channel openings. The α4-Ser284 residue is highly conserved and located within the M2 transmembrane α-helix that lines the ion channel. When mapped onto the receptor’s three-dimensional structure, the larger Trp substitution sterically clashes with the M2 α-helix from the neighboring subunit, promoting expansion of the pore and stabilizing the open relative to the closed conformation of the channel. Together, the clinical, genetic, functional, and structural observations demonstrate that α4-Ser284Trp enhances channel opening, predicting increased membrane excitability and a pathogenic seizure phenotype. |
| first_indexed | 2024-03-09T03:37:40Z |
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| issn | 1661-6596 1422-0067 |
| language | English |
| last_indexed | 2024-03-09T03:37:40Z |
| publishDate | 2022-10-01 |
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| series | International Journal of Molecular Sciences |
| spelling | doaj.art-9e0fc294328b48ffaa4ae023fad5f56c2023-12-03T14:46:23ZengMDPI AGInternational Journal of Molecular Sciences1661-65961422-00672022-10-0123201212410.3390/ijms232012124Genetic Variant in Nicotinic Receptor α4-Subunit Causes Sleep-Related Hyperkinetic Epilepsy via Increased Channel OpeningSimone Mazzaferro0Deborah J. Msekela1Edward C. Cooper2Atul Maheshwari3Steven M. Sine4Departments of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine and Science, Rochester, MN 55905, USADepartments of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine and Science, Rochester, MN 55905, USADepartment of Neurology, Baylor College of Medicine, Houston, TX 77030, USADepartment of Neurology, Baylor College of Medicine, Houston, TX 77030, USADepartments of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine and Science, Rochester, MN 55905, USAWe describe genetic and molecular-level functional alterations in the α4β2 neuronal nicotinic acetylcholine receptor (nAChR) from a patient with sleep-related hyperkinetic epilepsy and a family history of epilepsy. Genetic sequencing revealed a heterozygous variant c.851C>G in the <i>CHRNA4</i> gene encoding the α4 subunit, resulting in the missense mutation p.Ser284Trp. Patch clamp recordings from genetically engineered nAChRs incorporating the α4-Ser284Trp subunit revealed aberrant channel openings in the absence of agonist and markedly prolonged openings in its presence. Measurements of single channel current amplitude distinguished two pentameric stoichiometries of the variant nAChR containing either two or three copies of the α4-Ser284Trp subunit, each exhibiting aberrant spontaneous and prolonged agonist-elicited channel openings. The α4-Ser284 residue is highly conserved and located within the M2 transmembrane α-helix that lines the ion channel. When mapped onto the receptor’s three-dimensional structure, the larger Trp substitution sterically clashes with the M2 α-helix from the neighboring subunit, promoting expansion of the pore and stabilizing the open relative to the closed conformation of the channel. Together, the clinical, genetic, functional, and structural observations demonstrate that α4-Ser284Trp enhances channel opening, predicting increased membrane excitability and a pathogenic seizure phenotype.https://www.mdpi.com/1422-0067/23/20/12124sleep-related hyperkinetic epilepsyneuronal nicotinic acetylcholine receptorgain-of-function variantpatch-clampsingle ion-channelion-channel gating |
| spellingShingle | Simone Mazzaferro Deborah J. Msekela Edward C. Cooper Atul Maheshwari Steven M. Sine Genetic Variant in Nicotinic Receptor α4-Subunit Causes Sleep-Related Hyperkinetic Epilepsy via Increased Channel Opening International Journal of Molecular Sciences sleep-related hyperkinetic epilepsy neuronal nicotinic acetylcholine receptor gain-of-function variant patch-clamp single ion-channel ion-channel gating |
| title | Genetic Variant in Nicotinic Receptor α4-Subunit Causes Sleep-Related Hyperkinetic Epilepsy via Increased Channel Opening |
| title_full | Genetic Variant in Nicotinic Receptor α4-Subunit Causes Sleep-Related Hyperkinetic Epilepsy via Increased Channel Opening |
| title_fullStr | Genetic Variant in Nicotinic Receptor α4-Subunit Causes Sleep-Related Hyperkinetic Epilepsy via Increased Channel Opening |
| title_full_unstemmed | Genetic Variant in Nicotinic Receptor α4-Subunit Causes Sleep-Related Hyperkinetic Epilepsy via Increased Channel Opening |
| title_short | Genetic Variant in Nicotinic Receptor α4-Subunit Causes Sleep-Related Hyperkinetic Epilepsy via Increased Channel Opening |
| title_sort | genetic variant in nicotinic receptor α4 subunit causes sleep related hyperkinetic epilepsy via increased channel opening |
| topic | sleep-related hyperkinetic epilepsy neuronal nicotinic acetylcholine receptor gain-of-function variant patch-clamp single ion-channel ion-channel gating |
| url | https://www.mdpi.com/1422-0067/23/20/12124 |
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