Atrial fibrillation (AF) is the most common arrhythmia in the clinic. While previous studies have identified AF-associated mutations in several genes, the genetic basis for AF remains unclear. Here, we identified a novel T361S missense mutation in potassium voltage-gated channel, shal-related subfamily, member 3 (KCND3) from a Chinese Han family ancestor with lone AF. The wild-type (WT) or mutant T361S of Kv4.3 protein (encoded by KCND3) were co-expressed with the auxiliary subunit K+ channel-Interacting Protein (KChIP2) in HEK293 cells, and transient outward potassium current (Ito) were recorded using patch-clamp methods, and the surface or total protein levels of Kv4.3 were analyzed by western blot. Ito density, measured at 60 mV, for T361S was significantly higher than that for WT. Both the steady-state activation and inactivation curves showed a remarkable hyperpolarizing shift in T361S. Moreover, recovery from inactivation after a 500-ms depolarizing pulse was significantly delayed for T361S compared with that for WT. Mechanistically, the gain of function of Ito elicited by T361S was associated with the increased expression of cell surface and total cell protein of Kv4.3. The computer stimulation revealed that the T361S mutation shortened the action potential duration through an increased Itoin Human Atrial Model. In conclusion, we identified a novel T361S mutation in KCND3 associated with AF in the Chinese Han family. The T361S mutant result in the changes in channel kinetics as well as the up-regulation of Kv4.3 protein, which may be a critical driver for lone AF as observed in the patient.
Keywords: KCND3; atrial fibrillation; patch clamp; transient outward potassium current.