Epilepsy-causing mutations in Kv7.2 C-terminus affect binding and functional modulation by calmodulin
Mutations in the KCNQ2 gene, encoding for voltage-gated Kv7.2 K+ channel subunits, are responsible for early-onset epileptic diseases with widely-diverging phenotypic presentation, ranging from Benign Familial Neonatal Seizures (BFNS) to epileptic encephalopathy. In the present study, Kv7.2 BFNS-cau...
| Autores: | , , , , , , , , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2015 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/421275 |
| Acceso en línea: | http://hdl.handle.net/10261/421275 https://api.elsevier.com/content/abstract/scopus_id/84936816788 |
| Access Level: | acceso abierto |
| Palabra clave: | Surface Plasmon Resonance Calmodulin Electrophysiology Epilepsy Far-Western blotting Fluorescence Kv7.2 |
| Sumario: | Mutations in the KCNQ2 gene, encoding for voltage-gated Kv7.2 K+ channel subunits, are responsible for early-onset epileptic diseases with widely-diverging phenotypic presentation, ranging from Benign Familial Neonatal Seizures (BFNS) to epileptic encephalopathy. In the present study, Kv7.2 BFNS-causing mutations (W344R, L351F, L351V, Y362C, and R553Q) have been investigated for their ability to interfere with calmodulin (CaM) binding and CaM-induced channel regulation. To this aim, semi-quantitative (Far-Western blotting) and quantitative (Surface Plasmon Resonance and dansylated CaM fluorescence) biochemical assays have been performed to investigate the interaction of CaM with wild-type or mutant Kv7.2 C-terminal fragments encompassing the CaM-binding domain; in parallel, mutation-induced changes in CaM-dependent Kv7.2 or Kv7.2/Kv7.3 current regulation were investigated by patch-clamp recordings in Chinese Hamster Ovary (CHO) cells co-expressing Kv7.2 or Kv7.2/Kv7.3 channels and CaM or CaM1234 (a CaM isoform unable to bind Ca2+). The results obtained suggest that each BFNS-causing mutation prompts specific biochemical and/or functional consequences; these range from slight alterations in CaM affinity which did not translate into functional changes (L351V), to a significant reduction in the affinity and functional modulation by CaM (L351F, Y362C or R553Q), to a complete functional loss without significant alteration in CaM affinity (W344R). CaM overexpression increased Kv7.2 and Kv7.2/Kv7.3 current levels, and partially (R553Q) or fully (L351F) restored normal channel function, providing a rationale pathogenetic mechanism for mutation-induced channel dysfunction in BFNS, and highlighting the potentiation of CaM-dependent Kv7.2 modulation as a potential therapeutic approach for Kv7.2-related epilepsies. |
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