Figure 1
From: Intracellular hemin is a potent inhibitor of the voltage-gated potassium channel Kv10.1
Kv10.1 current inhibition by hemin. (A) Mean traces of Kv10.1 channel currents from Xenopus oocyte inside-out patches, stimulated with the indicated pulse protocol, before (black) and recorded at the indicated times (color) after hemin application at 1 nM (left), 10 nM (center), or 100 nM (right). Traces are normalized to the maximal current at 40 mV obtained under control conditions. Thick traces are means, sem is indicated in shading, the number of recordings n in parentheses. (B) Time course of normalized maximal currents at 40 mV with application of hemin at the indicated concentration at time zero. The superimposed curves are the results of single-exponential fits. (C) As in (B) with 10 nM hemin application, wash with control solutions (Wash), and final exposure of the inside-out patch to a control solution with 1 mM DTT. The solid line is a single-exponential data fit to characterize the onset of current inhibition. (D) Steady-state Kv10.1 current inhibition at 40 mV, recorded from inside-out Xenopus oocyte membrane patches, as a function of hemin concentration in oxidizing (no GSH, red circles) and reducing (with 1 mM reduced GSH, green squares) conditions. The continuous curves are the result of Hill fits (Eq. 3) yielding the indicated half-maximal inhibition concentrations. (E) Mean remaining current at 40 mV in Kv10.1-containing inside-out patches after 200-s application of hemin (Fe3+), heme (Fe2+), protoporphyrin IX (PpIX), and Zn(II) protoporphyrin IX (Zn-PpIX) (all at 50 nM concentration), as well as FeSO4 (1 µM) and MP-11 (1 µM). Data are mean ± sem, n in parentheses. For current traces, see Supplementary Fig. S1. Solutions: Standard K-Asp.
