Di-Substituted Cyclohexyl Derivatives Bind to Two Identical Sites with Positive Cooperativity on the Voltage-Gated Potassium Channel, Kv1.3

Di-substituted cyclohexyl (DSC) derivatives inhibit the voltage-gated potassium channel, Kv1.3, and have immunosuppressant activity (Schmalhofer et al. (2002) Biochemistry 41, 7781−7794). This class of inhibitors displays Hill coefficients of near 2 in functional assays, and trans DSC analogues appear to selectively interact with Kv1.3 channel conformations related to C-type inactivation. To further understand the details of the DSC inhibitor interaction with potassium channels, trans-1-(N-n-propylcarbamoyloxy)-4-phenyl-4-(3-(2-methoxyphenyl)-3-oxo-2-azaprop-1-yl)cyclo-hexane (trans-NPCO-DSC) was radiolabeled with tritium, and its binding characteristics to Kv1.3 channels were determined. Specific binding of [3H]-trans-NPCO-DSC to Kv1.3 channels is a saturable, time-dependent, and fully reversible process. Saturation binding isotherms and competition binding experiments are consistent with the presence of two receptor sites for DSC derivatives on the Kv1.3 channel that display positive allosteric cooperat...