Gating Modulation of the Tumor‐Related Kv10.1 Channel by Mibefradil

Abstract

Several reports credit mibefradil with tumor suppressing properties arising from its known inhibition of Ca currents. Given that mibefradil (Mb) is also known to inhibit K channels, we decided to study the interaction between this organic compound and the tumor-related Kv10.1 channel. Here we report that Mb modulates the gating of Kv10.1. Mb induces an apparent inactivation from both open and early closed states where the channels dwell at hyperpolarized potentials. Additionally, Mb accelerates the kinetics of current activation, in a manner that depends on initial conditions. Our observations suggest that Mb binds to the voltage sensor domain of Kv10.1 channels, thereby modifying the gating of the channels in a way that in some, but not all, aspects opposes to the gating effects exerted by divalent cations. J. Cell. Physiol. 232: 2019-2032, 2017. © 2016 Wiley Periodicals, Inc.

Correction to: Inhibition of the K+ conductance and Cole-Moore shift of the oncogenic Kv10.1 channel by amiodarone

“…HEK293 cells stably expressing the Kv10.1 channel [10] were kept in culture at 37°C in a humidified 5% CO 2 atmosphere in DMEM/F12 media supplemented with 10%FBS and containing zeocin 300 μM. Experiments were conducted 24 h after palting the cells on glass coverslips, as previously reported [10]. HEK293-Kv10.1 cells were kindly provided by Dr. Luis A. Pardo and Walter Stühmer.…”

“…Eighty percent series resistance compensation was always applied. Experiments were conducted at room temperature, as previously reported [10].…”

Mibefradil inhibition of the Cole-Moore shift and K+-conductance of the tumor-related Kv10.1 channel

“…1), pointing out to the voltage-sensor domain as a site of action of mibefradil. 18 The exhaustive Competition-plot of CornishBowden, 19 performed between quinidine and mibefradil, along with other observations, excluded open-pore block as the mechanism underlying mibefradilinduced inactivation. Hence, we concluded that both the mibefradil inhibition of the Cole-Moore effect and its induced inactivation were the result of the drug binding within the voltage-sensor domain.…”

“…20 Similar to our hypothesis regarding the gating modification of Kv10.1, namely that mibefradil binds to the voltagesensor domain inducing an apparent inactivation and accelerating the rate limiting transition that accompanies the passage from deep closed states to states near the open state. 17,18 It remains to be determined where on the voltage-sensor domain mibefradil binds, thus exerting the aforementioned effects, and how this relates to the particular way of communication between voltage-sensor and pore domains of Kv10.1.…”

“…18 Upon prolonged depolarizations, externally added mibefradil induces an apparent open-state inactivation, that inhibits the K C conductance, and shifts the conductance (G)…”