Use Dependent Attenuation of Rat HCN1-Mediated Ih in Intact HEK293 Cells

Abstract

Background/Aims: Cationic currents (I_h) through the fast activating and relatively cAMP insensitive subtype of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, HCN1, are limited by cytosolic factors in mammalian cells. This cytosolic HCN1 break is boosted by changes in membrane voltage that are not characterized on a biophysical level, yet. Methods: We overexpressed rat (r)HCN1 in human embryonic kidney cells (HEK293) and recorded pharmacologically isolated I_h in cell-attached or whole-cell mode of the patch-clamp technique. Results: Recurring activation of rHCN1 reduced and slowed I_h in intact HEK293 cells (cell-attached mode). On the contrary, sustained disruption of the intracellular content (whole-cell mode) ceased activity dependence and partially enables voltage dependent hysteresis. The activity induced I_h attenuation in intact cells was independent of the main external cation, depended on the number of previous forced activations and was - at least in part - due to a shift in the voltage dependence of activation towards hyperpolarization as estimated by an adapted tail current analysis. Intracellular elevation of cAMP could not reverse the changes in I_h. Conclusion: Reduction of rHCN1 mediated I_h is use dependent and may involve the coupling of voltage sensor and pore.

Characterization in Dual Activation by Oxaliplatin, a Platinum-Based Chemotherapeutic Agent of Hyperpolarization-Activated Cation and Electroporation-Induced Currents

“…Voltage-dependent hysteresis of I h is thought to exhibit a substantial role in influencing the electrical behavior of electrically excitable cells such as GH 3 cells. In agreement with previous observations [42][43][44], the I h natively existing in GH 3 cells was described to undergo either a hysteretic change in its voltage dependence, or a mode shift in which the voltage sensitivity in gating charge movements of the current depends on the previous state of the channel [42,43]. In this study, we also examined the possible perturbations of OXAL on such a non-equilibrium property of I h in GH 3 cells.…”

“…The voltage-dependent hysteresis of Ih has been previously demonstrated to exert a high influence on electrical behaviors such as action potential (AP) firing [42][43][44]. For this reason, we further explored whether there is possible voltage-dependent hysteresis existing in Ih recorded from GH3 cells.…”

Characterization of Inhibitory Effectiveness in Hyperpolarization-Activated Cation Currents by a Group of ent-Kaurane-Type Diterpenoids from Croton tonkinensis

“…The voltage-dependent hysteresis of I h has been shown to exhibit substantial role in influencing electrical behavior of electrically excitable cells such as GH 3 cells. In keeping with previous observations [25][26][27], the I h identified in GH 3 cells was found to undergo either a hysteresis in its voltage dependence, or mode shift in which the voltage sensitivity of gating charge movements relies on the previous state [26,27]. In this study, we also examined possible perturbations of croton-03 on such non-equilibrium property of I h in GH 3 cells.…”

“…The voltage-dependent hysteresis of ionic currents (e.g., I h ) has been previously demonstrated to exert a significant impact on electrical behaviors such as the firing of action potentials [25][26][27]. For this reason, we further explored whether there is possible voltage-dependent hysteresis existing in I h recorded from GH 3 cells.…”

Effectiveness in the Block by Honokiol, a Dimerized Allylphenol from Magnolia Officinalis, of Hyperpolarization-Activated Cation Current and Delayed-Rectifier K+ Current

“…It has been previously demonstrated that the voltage-dependent hysteresis of I h density can exert a high influence on electrical behaviors such as action potential firing [41,[44][45][46]. As such, we further explored whether HNK could perturb the voltage hysteresis of this current density identified in GH 3 cells.…”