Purpose: Na_v1.5 α-subunits constitute the central ion-conducting pore of the cardiac sodium channel. While these subunits are not known to oligomerize, some studies suggest a possible cooperation between them. Here, we aimed to explore the effects of potential interaction between Na_v1.5 α-subunits by characterizing two Na_v1.5 mutations: R104W, an N-terminal variant identified in a patient with a Brugada type-I ECG pattern, and R1860GfsX12, a C-terminal truncating variant identified in a patient with a complex clinical picture of sick sinus syndrome and atrial fibrillation.

Methods: Both mutant channels were expressed alone or with wild type (WT) channels in a 1:1 ratio in HEK293 cells and their effects were studied by biochemical and patch-clamp analysis.

Results: Expressing the N-terminal mutation R104W alone resulted in mostly degraded protein and absence of I_Na current. In the heterozygous state, the mutant exerted a dominant negative effect on WT channels and led to a positive shift of voltage-dependent activation. The mutant alone was mostly retained in the endoplasmic reticulum whereas its co-expression with WT led to WT retention. The C-terminal mutation R1860GfsX12 expressed alone showed partial proteasomal protein degradation, a drastic reduction of I_Na density, a positive shift of activation, a negative shift of steady-state inactivation and an increase in persistent current compared to WT. However, co-transfection of this mutant with the WT channel almost restored the I_Na density to the WT level, but the biophysical properties of the mutant channels remained altered. In addition, an increase in total and cell surface protein expression of mutant channels was observed, suggesting that WT channels allow mutant proteins to escape proteasomal degradation. Co-immunoprecipitation studies showed that the WT α-subunits interacted with each other, as well as the N- and C-terminal mutants with WT α-subunits.

Conclusion: Our results indicate an interaction between Na_v1.5 α-subunits, likely occurring in the endoplasmic reticulum. WT and mutant channel interaction could impair or favour channel trafficking, and modulate the effects of Na_v1.5 mutations and their clinical phenotypes.

عنوان المؤتمر

Denis Escande Symposium 2013

دولة المؤتمر

هولندا

تاريخ المؤتمر

30 أغسطس، 2013 - 31 أغسطس، 2013

راعي المؤتمر

St Jude Medical, Boston Scientific, Thermofischer and other

معلومات إضافية

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