Knockdown of Cav3 or Nedd4-2 enhances IhERG (A) and the 155-kDa hERG expression (B) in a stable HEK 293 cell line expressing both hERG and Cav3. Cav3-hERG-HEK cells transfected with scrambled control siRNA, Cav3 siRNA, or Nedd4-2 siRNA for 24–48 h were collected for electrophysiology and Western blot analyses. A, effects of Cav3 siRNA or Nedd4-2 siRNA transfection on IhERG. The number above the bars in the lower panel indicates the number of cells examined. B, effects of Cav3 siRNA or Nedd4-2 siRNA transfection on the expression levels of hERG, Cav3, and Nedd4-2. The hERG 155-kDa expression levels under each condition are shown in the lower panel (n = 5). Compared with the control siRNA transfection, Cav3 siRNA transfection reduced Cav3 expression by 61% ± 13% (p < 0.01, n = 5), and Nedd4-2 siRNA transfection reduced Nedd4-2 expression by 81% ± 5% (p < 0.01, n = 5). *, p < 0.05; **, p < 0.01 versus control (Ctl) siRNA.