Effective Perturbations of the Amplitude, Gating, and Hysteresis of IK(DR) Caused by PT-2385, an HIF-2α Inhibitor

Abstract

PT-2385 is currently regarded as a potent and selective inhibitor of hypoxia-inducible factor-2α (HIF-2α), with potential antineoplastic activity. However, the membrane ion channels changed by this compound are obscure, although it is reasonable to assume that the compound might act on surface membrane before entering the cell´s interior. In this study, we intended to explore whether it and related compounds make any adjustments to the plasmalemmal ionic currents of pituitary tumor (GH3) cells and human 13-06-MG glioma cells. Cell exposure to PT-2385 suppressed the peak or late amplitude of delayed-rectifier K+ current (IK(DR)) in a time- and concentration-dependent manner, with IC50 values of 8.1 or 2.2 µM, respectively, while the KD value in PT-2385-induced shortening in the slow component of IK(DR) inactivation was estimated to be 2.9 µM. The PT-2385-mediated block of IK(DR) in GH3 cells was little-affected by the further application of diazoxide, cilostazol, or sorafenib. Increasing PT-2385 concentrations shifted the steady-state inactivation curve of IK(DR) towards a more hyperpolarized potential, with no change in the gating charge of the current, and also prolonged the time-dependent recovery of the IK(DR) block. The hysteretic strength of IK(DR) elicited by upright or inverted isosceles-triangular ramp voltage was decreased during exposure to PT-2385; meanwhile, the activation energy involved in the gating of IK(DR) elicitation was noticeably raised in its presence. Alternatively, the presence of PT-2385 in human 13-06-MG glioma cells effectively decreased the amplitude of IK(DR). Considering all of the experimental results together, the effects of PT-2385 on ionic currents demonstrated herein could be non-canonical and tend to be upstream of the inhibition of HIF-2α. This action therefore probably contributes to down-streaming mechanisms through the changes that it or other structurally resemblant compounds lead to in the perturbations of the functional activities of pituitary cells or neoplastic astrocytes, in the case that in vivo observations occur.

Evidence for Inhibitory Perturbations on the Amplitude, Gating, and Hysteresis of A-Type Potassium Current, Produced by Lacosamide, a Functionalized Amino Acid with Anticonvulsant Properties

“…The nonlinear V hys phenomenon inherently in different types of voltage-gated ionic currents has been since demonstrated to play roles in affecting various electrical behavior of excitable cells [59,60]. In this study, we were able to identify the V hys existence of I K(A) residing in GH 3 cells (Figure 6), implying that the voltage sensitivity inherent in the gating charge movement of K A channels is thought to rely on the previous state of the channel [61,62]. In other words, the magnitude of I K(A) is most likely to be contingent on the pre-existing state(s) or conformation(s) of the K A channel.…”

“…In other words, the magnitude of I K(A) is most likely to be contingent on the pre-existing state(s) or conformation(s) of the K A channel. The V hys strength of I K(A) is important, and it would be engaged in the regulation of electrical behaviors of excitable cells such as GH 3 cells [62,63]. In other words, as the action potential develops, the voltage dependence of K A channels may shift the mode of V hys to one in which activation occurs at more negative potentials, resulting in an increase in membrane repolarization, while as the membrane becomes negative, the voltage-dependence of I K(A) activation would switch to more positive voltages, therefore enhancing cell excitability [44,61].…”

Effective Perturbations by Phenobarbital on INa, IK(erg), IK(M) and IK(DR) during Pulse Train Stimulation in Neuroblastoma Neuro-2a Cells

“…The K V channels play a role in determining the membrane excitability associated with delayed-rectifier K V channels. The activity of K V 3 ( KCNC ) or K V 2 ( KCNB ) channels and the magnitude of delayed-rectifier K + current ( I K(DR) ) are correlated with AP firing in many cell types [ 18 , 26 , 30 ]. This type of I K(DR) activated during pulse train (PT) stimulations have the propensity to induce the resurgent K + tail current, which is proposed to serve as a negative-feedback mechanism for the closure of K V channels during high-frequency firing [ 31 ].…”

Inhibitory Effectiveness in Delayed-Rectifier Potassium Current Caused by Vortioxetine, Known to Be a Novel Antidepressant

“…The voltage-gated K + (K V ) channels are regarded as having a great influence in determining membrane excitability associated with delayed-rectifier K V channels, such as K V 3 (KCNC) and K V 2 (KCNB) channels; additionally, they are widely distributed and functionally expressed in neuroendocrine or endocrine cells [ 20 , 21 , 22 , 23 , 24 , 25 ]. Growing evidence reveals that there is a casual relationship with respect to the activity of K V 3 or K V 2 channels and the magnitude of delayed-rectifier K + currents ( I K(DR) ), and that changes in current magnitude are thought to be correlated with action potential firing and neurotransmitter release [ 26 , 27 , 28 , 29 , 30 , 31 , 32 ].…”