Functional analysis of novel SCN5A mutations related to Brugada syndrome

Abstract

Abstract Brugada syndrome (BrS) is an arrhythmogenic disorder that has been linked to mutations in SCN5A, the gene encoding for the pore-forming α-subunit of the cardiac Na+ channel. Recently, novel SCN5A missense mutations (A385T and R504T) were identified in a BrS patient. Since the mutations are in the loop connecting transmembrane segments 5 and 6 in domain 1 (S5-S6 in DI) and segments 6 and 1 between domain 1 and 2 (DI-DII linker), it can lead to dysfunctional property of the Na+ channel. Here we aimed to characterize the electrophysiological properties of A385T and R504T. The wild-type (WT) and mutant SCN5A were transiently transfected in HEK293 cells, and the Na+ channel was analyzed using the whole-cell patch-clamp technique. WT, A385T, R504T, and double mutant (A385T/R504T) showed no significant differences in the current density and the voltage-dependent activation. Unexpectedly, a rightward shift of the voltage-dependent inactivation was identified in the three groups of mutation. Besides, the recovery from inactivation of double mutant was faster than that of WT. These results suggest that, contrary to the expected mechanism of BrS, the mutations cause a gain-of-function of NaV1.5. However, the current densities of R504T and double mutant transfected with β-subunit SCN1B were significantly suppressed but A385T was not different from WT. The voltage dependent activation and inactivation of all mutants were not significantly different from WT. The recovery from inactivation of all mutants were slower than that of WT. These results suggest that R504T mutation of α-subunit SCN5A interacting with β-subunit SCN1B is responsible to pathophysiological function of novel BrS. Funding Acknowledgement Type of funding sources: None.