Antidepressive effect of an inward rectifier K+ channel blocker peptide, tertiapin-RQ
Fig 2
Blockade of ROMK currents by TPN-RQ and the lack of effect of Cys-to-Ser mutants.
(A) Whole-cell ROMK currents were evoked by step-pulses, as shown in the protocol. The application of TPN-RQ decreased ROMK currents in a concentration-dependent manner. The remaining current was resistant to 6 mM BaCl2, which is a selective blocker of the ROMK channel, indicating that TPN-RQ blocked the channel nearly completely. (B and C) The C3S and C5S mutants of TPN-RQ hardly inhibited the ROMK currents even at the highest concentrations, indicating the essential role of these Cys residues. (D) I-V relationship of whole-cell ROMK channel currents in the absence (Control) or presence of blockers (7 μM TPN-RQ and 6 mM BaCl2). The I-V curves of TPN-RQ and BaCl2 were completely overlapped. (E) The concentration–response curve of TPN-RQ, (C3S), and (C5S) on ROMK conductance (n = 3). (F) Preceding treatment of TPN-RQ with PDI did not affect the blocking activity of TPN-RQ, suggesting the adequate formation of disulfide bonds (n = 4).