PKA phosphorylation is important for Nav1.5 expression and function, however little is known about the relationship between Brugada syndrome (BrS) phenotype and PKA. We characterized the biophysical properties of a novel BrS-associated SCN5A mutation, R526H, identified in a proband that was resuscitated from sudden cardiac death. Methods: Whole-cell currents through wild-type (WT) Nav1.5 and mutant (R526H) channels expressed in HEK293-cell were recorded using patch clamp. Results: No difference was found in the peak current, steady-state activation, inactivation and recovery from inactivation in WT and mutant channels at baseline. PKA-stimulation (forskolin+cAMP) 1.7-fold increased the peak Na current (p>0.01), hyperpolarized the activation curve (+13mV; p>0.01) and hastened recovery from inactivation of WT. In contrast, no difference was found in the peak Na current, activation and recovery from inactivation after PKA-stimulation in R526H or in the mutation of the PKA-phosphorylation site, S528A. Voltage-dependent availability was not altered by PKA in WT, R526H and S528A. Thus, PKA-stimulation 4-fold increased Na window current in WT but not the mutant channels. In-vitro PKA phosphorylation was detected in the I-II linker of WT but not R526H and S528A mutants of Nav1.5. Conclusion: R526H mutant eliminated phosphorylation of Nav1.5 and abolished the PKA-induced increase in current amplitude. The loss of PKA stimulation may result in the Brugada phenotype.
- Na channel
- sudden death
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine