A C-terminal truncating mutation in Nav1.5 results in a loss of interaction with FHF1B
- Publication Type
- Conference Paper
- Authors
- Azza ZIYADEH-ISLEEM
- Jérôme Clatot
- sa
- Estelle Gandjbakhch
- Isabelle Denjoy
- Françoise Hidden-Lucet
- Alain Coulombe
- Nathalie Neyroud
- Pascale Guicheney
Introduction
The cardiac voltage-gated Na+ channel Nav1.5 underlies the cardiac Na+ current INa, which is essential for the generation and the transmission of the action potential. INa dysfunction can cause different types of arrhythmias. Several partners interact with the C-terminus of Nav1.5, including the Fibroblast Growth Factor Homologous Factor 1B (FHF1B), which modulates Nav1.5 inactivation. Its interaction site on Nav1.5 is still controversial, located either in the proximal or in the proximal and the distal parts of Nav1.5 C-terminus.
Here, we characterized two truncating mutations occurring in the last exon of SCN5A: R1860GfsX12 is a new mutation identified in a patient with a mixed clinical picture of sick sinus syndrome and atrial fibrillation, and L1821fsX10 was previously reported, also with a complex clinical phenotype, and tested whether the distal region of the Nav1.5 C-terminus interacts with FHF1B.
Methods and Results
Western blot analysis of HEK cells transiently expressing each mutant channels showed their partial proteasomal degradation. However, both mutant channels reached the plasma membrane, as shown by cell surface biotinylation. Patch-clamp recordings showed a marked reduction in INa density, a -25mV shift of the steady-state inactivation, drastically slowed inactivation kinetics and a persistent INa when mutants were compared to wild type (WT). In cells co-expressing the WT and the R1860GfsX12 channels in a 1:1 ratio, the steady-state inactivation and inactivation kinetics were still altered. Co-immunoprecipitation studies showed that the interaction of both mutants with FHF1B was nearly abolished.
Conclusion
The loss of interaction of the mutants with FHF1B confirms the involvement of the proximal and the distal parts of the Nav1.5 C-terminus in its interaction with FHF1B and is consistent with the shift of inactivation of INa. The mixed clinical picture of the patients is likely explained by the altered kinetics properties.
- Conference Title
- Printemps de la Cardiologie
- Conference Country
- France
- Conference Date
- April 18, 2013 - April 19, 2013
- Conference Sponsor
- wwww
- Additional Info
- Conference Website