Deletion of Protein Kinase A Phosphorylation Sites in the HERG Potassium Channel Inhibits Activation Shift by Protein Kinase A

Xenopus oocytes heterologously expressing HERG clones (wild type and mutants S283A, S890A, T895A, S1137A, and 4M)

Application of cAMP-specific phosphodiesterase (PDE IV) inhibitor Ro-20-1724 (100 microM) or adenylate cyclase activator forskolin (400 microM, 60 min)

HERG wild type channels compared to HERG 4M channels (missing all PKA phosphorylation sites)

HERG potassium currents and shift in activation curve measured with two microelectrode voltage clamp techniquesurrogate