KCND3 missense mutations increase Ito current in heterologous cells. A: Representative whole-cell wild-type (WT) plus KChIP2, p.Val392Ile plus KChIP2, p.Ser530Pro plus KChIP2, and p.Gly600Arg Kv4.3 plus KChIP2 traces recorded in HEK293 cells elicited by step depolarization of 500 ms duration to +40 mV from a holding potential of −80 mV in 10 mV increments. B: The current voltage relationship for WT (n = 16), p.Val392Ile (n = 16), p.Ser530Pro (n = 17), and p.Gly600Arg (n = 11) Kv4.3 channels coexpressed with KChIP2. All values represent mean ± SEM. *P < 0.05 versus WT Kv4.3 plus KChIP2. C: Bar graph showing peak current density at 40 mV for WT (n = 16), p.Val392Ile (n = 16), p.Ser530Pro (n = 17), and p.Gly600Arg (n = 11) Kv4.3 channels coexpressed with KChIP2. *P < 0.05 versus WT Kv4.3 plus KChIP2.