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

Hung-Tsung Hsiao; Guan-Ling Lu; Yen-Chin Liu; Sheng-Nan Wu

doi:10.3390/membranes11080636

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

Membranes (Basel). 2021 Aug 17;11(8):636. doi: 10.3390/membranes11080636.

Authors

Hung-Tsung Hsiao¹, Guan-Ling Lu¹, Yen-Chin Liu^{1

2}, Sheng-Nan Wu^{3

4}

Affiliations

¹ Department of Anesthesiology, College of Medicine, National Cheng Kung University Hospital, National Cheng Kung University, Tainan City 70403, Taiwan.
² Department of Anesthesiology, School of Post-Baccalaureate, College of Medicine, Kaohsiung Medical University, Kaohsiung City 80708, Taiwan.
³ Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan City 70101, Taiwan.
⁴ Department of Physiology, College of Medicine, National Cheng Kung University, Tainan City 70101, Taiwan.

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 (I_K(DR)) in a time- and concentration-dependent manner, with IC₅₀ values of 8.1 or 2.2 µM, respectively, while the K_D value in PT-2385-induced shortening in the slow component of I_K(DR) inactivation was estimated to be 2.9 µM. The PT-2385-mediated block of I_K(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 I_K(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 I_K(DR) block. The hysteretic strength of I_K(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 I_K(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 I_K(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.

Keywords: PT-2385; current kinetics; delayed-rectifier K+ current; free energy; glioma cell; pituitary cell; voltage-dependent hysteresis.