The effects of H-89 (N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide), a potent and selective inhibitor of protein kinase A (PKA), were examined on Kv1.3 channels stably expressed in Chinese hamster ovary (CHO) cells using the patch clamp technique. In whole-cell recordings, H-89 decreased Kv1.3 currents and accelerated the decay rate of current inactivation in a concentration-dependent manner with an ic50 value of 1.70 μM. These effects were completely reversible after washout. Intracellular infusion with PKA inhibitors, adenosine 3′, 5′-cyclic phosphorothioate-Rp (Rp-cAMPS) or protein kinase A inhibitor 5-24 (PKI 5-24) had no effect on Kv1.3 currents and did not prevent the inhibitory action of H-89 on the current. H-89 applied to the cytoplasmic surface also inhibited Kv1.3 currents in excised inside-out patches. These findings suggest that H-89 inhibits Kv1.3 currents independently of PKA.
Bibliographical noteFunding Information:
We thank Dr. Kaczmarek (Yale University School of Medicine, USA) for the Kv1.3 transfected CHO cells and Won Kim for reading the manuscript. This work was supported by the Catholic Medical Center Research Fund for Special Projects (1997).
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