Absence of a Trafficking Defect in R1232W/T1620M, a Double SCN5A Mutant Responsible for Brugada Syndrome

BACKGROUND: A trafficking defect of mutant cardiac Na-channels (SCN5A) has been implicated in Brugada syndrome. Although R1232W polymorphism and T1620M mutation by themselves have little effect on Na-channel function, their combination has been reported to disrupt membrane trafficking, resulting in a non-functioning Na channel. METHODS AND RESULTS: Contrary to previous findings, patch-clamp recordings of heterologously expressed R1232W/T1620M showed robust Na currents and confocal microscopy exhibited predominant expression in the plasma membrane, similar to the wild-type channel. CONCLUSIONS: It is unlikely that an intragenic interaction between R1232W and T1620M of SCN5A causes a trafficking defect leading to a non-functioning Na channel.