Abstract |
KCNQ2 and KCNQ3 K+ channel subunits underlie the muscarinic-regulated K+ current (I(KM)), a widespread regulator of neuronal excitability. Mutations in KCNQ2- or KCNQ3-encoding genes cause benign familiar neonatal convulsions (BFNCs), a rare autosomal-dominant idiopathic epilepsy of the newborn. In the present study, we have investigated, by means of electrophysiological, biochemical, and immunocytochemical techniques in transiently transfected cells, the consequences prompted by a BFNC-causing 1-bp deletion (2043deltaT) in the KCNQ2 gene; this frameshift mutation caused the substitution of the last 163 amino acids of the KCNQ2 C terminus and the extension of the subunit by additional 56 residues. The 2043deltaT mutation abolished voltage-gated K+ currents produced upon homomeric expression of KCNQ2 subunits, dramatically reduced the steady-state cellular levels of KCNQ2 subunits, and prevented their delivery to the plasma membrane. Metabolic labeling experiments revealed that mutant KCNQ2 subunits underwent faster degradation; 10-h treatment with the proteasomal inhibitor MG132 (20 microm) at least partially reversed such enhanced degradation. Co-expression with KCNQ3 subunits reduced the degradation rate of mutant KCNQ2 subunits and led to their expression on the plasma membrane. Finally, co-expression of KCNQ2 2043deltaT together with KCNQ3 subunits generated functional voltage-gated K+ currents having pharmacological and biophysical properties of heteromeric channels. Collectively, the present results suggest that mutation-induced reduced stability of KCNQ2 subunits may cause epilepsy in neonates.
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Authors | Maria Virginia Soldovieri, Pasqualina Castaldo, Luisa Iodice, Francesco Miceli, Vincenzo Barrese, Giulia Bellini, Emanuele Miraglia del Giudice, Antonio Pascotto, Stefano Bonatti, Lucio Annunziato, Maurizio Taglialatela |
Journal | The Journal of biological chemistry
(J Biol Chem)
Vol. 281
Issue 1
Pg. 418-28
(Jan 06 2006)
ISSN: 0021-9258 [Print] United States |
PMID | 16260777
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
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Chemical References |
- KCNQ2 Potassium Channel
- KCNQ3 Potassium Channel
- Protein Subunits
- Green Fluorescent Proteins
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Topics |
- Animals
- CHO Cells
- Carcinoma, Hepatocellular
- Cell Line, Tumor
- Cell Membrane
(physiology)
- Cricetinae
- Epilepsy, Benign Neonatal
(genetics, physiopathology)
- Frameshift Mutation
- Green Fluorescent Proteins
(genetics)
- Humans
- Infant, Newborn
- KCNQ2 Potassium Channel
(chemistry, genetics, physiology)
- KCNQ3 Potassium Channel
(chemistry, genetics, physiology)
- Liver Neoplasms
- Mutagenesis
- Patch-Clamp Techniques
- Protein Subunits
(chemistry, physiology)
- Transfection
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