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The Journal of Neuroscience, October 10, 2007, 27(41):11037-11046; doi:10.1523/JNEUROSCI.3515-07.2007
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Neurobiology of Disease
Modulatory Proteins Can Rescue a Trafficking Defective Epileptogenic Nav1.1 Na+ Channel Mutant
Raffaella Rusconi,1 *
Paolo Scalmani,1 *
Rita Restano Cassulini,2
Giulia Giunti,1
Antonio Gambardella,3,4
Silvana Franceschetti,1
Grazia Annesi,4
Enzo Wanke,2 and
Massimo Mantegazza1
1Department of Neurophysiopathology, Besta Neurological Institute, 20133 Milan, Italy, 2Department of Biotechnology and Biosciences, Milano-Bicocca University, 20126 Milan, Italy, 3Institute of Neurology, Magna Graecia University, 88100 Catanzaro, Italy, and 4Institute of Neurological Sciences, Consiglio Nazionale delle Ricerche, 87050 Mangone, Italy
Correspondence should be addressed to either of the following: Dr. Massimo Mantegazza, Department of Neurophysiopathology, Istituto Neurologico Besta, Via Celoria 11, 20133 Milano, Italy, Email: mmantegazza{at}istituto-besta.it; or Prof. Enzo Wanke, Department of Biology and Biotechnology, Università di Milano-Bicocca, Piazza della Scienza, 20126 Milan, Italy, Email: enzo.wanke{at}unimib.it
Familial epilepsies are often caused by mutations of voltage-gated Na+ channels, but correlation genotype–phenotype is not yet clear. In particular, the cause of phenotypic variability observed in some epileptic families is unclear. We studied Nav1.1 (SCN1A) Na+ channel subunit M1841T mutation, identified in a family characterized by a particularly large phenotypic spectrum. The mutant is a loss of function because when expressed alone, the current was no greater than background. Function was restored by incubation at temperature <30°C, showing that the mutant is trafficking defective, thus far the first case among neuronal Na+ channels. Importantly, also molecular interactions with modulatory proteins or drugs were able to rescue the mutant. Protein–protein interactions may modulate the effect of the mutation in vivo and thus phenotype; variability in their strength may be one of the causes of phenotypic variability in familial epilepsy. Interacting drugs may be used to rescue the mutant in vivo.
Key words: sodium; current; epilepsy; excitability; trafficking; GEFS+; SMEI; seizure; SCN1A
Received March 3, 2007;
revised Aug. 14, 2007;
accepted Aug. 15, 2007.
Correspondence should be addressed to either of the following: Dr. Massimo Mantegazza, Department of Neurophysiopathology, Istituto Neurologico Besta, Via Celoria 11, 20133 Milano, Italy, Email: mmantegazza{at}istituto-besta.it; or Prof. Enzo Wanke, Department of Biology and Biotechnology, Università di Milano-Bicocca, Piazza della Scienza, 20126 Milan, Italy, Email: enzo.wanke{at}unimib.it
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