Characterization of a new C-terminal truncating Nav1.5 mutation associated with sick sinus syndrome and atrial arrhythmia
- Publication Type
- Conference Paper
- Authors
- Azza ZIYADEH-ISLEEM
- Jérôme Clatot
- Sabine Duchatelet
- Estelle Gandjbakhch
- Isabelle Denjoy
- Svetlana Maugenre
- Françoise Hidden-Lucet
- Alain Coulombe
- Nathalie Neyroud
- Pascale Guicheney
Introduction
Mutations in SCN5A, which encodes the cardiac sodium channel Nav 1.5, result in multiple arrhythmic syndromes, like long QT syndrome type 3, Brugada syndrome, and rare cases of sick sinus syndrome and atrial fibrillation. Eight families with atrial arrhythmia were screened for twelve familial atrial fibrillation genes. A heterozygous SCN5A frameshift mutation, p.Arg1860GlyfsX12, leading to premature truncation of the Nav1.5 C-terminal domain, was identified in a family presenting with an atypical phenotype of sick sinus syndrome, paroxysmal atrial fibrillation, first degree AV block and atrial flutter. We aimed to characterize the physiological and biophysical properties of this mutation.
Methods and results
Sequencing and restriction analysis showed mutant mRNA to be present in proband lymphocytes, escaping nonsense mediated mRNA decay, consistent with the mutation’s location in the last exon of SCN5A. The sodium current INa was recorded in HEK293 cells transfected with wild type (WT) or mutant channels using the patch-clamp technique. Mutant channel reduced INa by 70% compared to WT. In addition, gating kinetics analysis showed a 20-mV negative shift of inactivation and an increased late current. Western blot analysis showed a significant decrease in total protein expression of the mutant channel compared to WT. Mutant protein expression was restored by the ubiquitin-proteasome inhibitor, MG132, suggesting a cellular degradation of the mutant. Moreover, cell surface protein biotinylation showed reduced cell surface expression of mutant compared to WT.
Conclusion
The Nav1.5 mutant Arg1860GlyfsX12 resulted in a loss-of-function phenotype, with a mixed clinical picture of sick sinus syndrome, first degree AV block and atrial fibrillation or flutter. We now aim to determine the sub-cellular localization of this truncated channel which lacks binding sites for proteins involved in the correct localization and stability of the cardiac Na+ channel.
- Conference Title
- Printemps de la Cardiologie
- Conference Country
- France
- Conference Date
- April 12, 2012 - April 13, 2012
- Conference Sponsor
- wwww
- Additional Info
- Conference Website