Title
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Acute and delayed drug effects on voltage-gated potassium channels = Acute en vertraagde geneesmiddel effecten op spanningsgevoelige kaliumkanalen
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Author
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Abstract
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The voltage-dependent K⁺ (Kv) channel family is large compared to other ion channel families, owing to a diverse array of genes encoding different α-subunits. In some subfamilies, these subunits can "mix-and-match" to form functional tetrameric Kv channels, further expanding this channel family. As a result, Kv channels are involved in a wide range of (patho)physiological processes. Consequently, there is interest in developing selective drugs that target specific Kv channels. However, drug specificity remains a major challenge due to the homology within the Kv channel family. In parallel, safety pharmacology is increasingly incorporating a broader range of Kv channels to prevent adverse side effects in newly developed drugs. Current in vitro testing procedures primarily focus on acute drug effects, often overlooking delayed effects that manifest slowly and are not yet routinely included in drug screening. In this thesis, we investigate a potential new selective drug binding site in Kv channels, and the importance of optimizing experimental conditions to ensure reliable and relevant drug screening outcomes. Using the whole-cell voltage-clamp technique, we demonstrated that extracellular charge substitutions in the S1-S2 linker of the Kv1.5 channel significantly modulate its gating properties. Specifically, a charge reversal from positive to negative (R276E) shifted the voltage dependence of channel activation in the hyperpolarized direction, while the opposite reversal (E274K and E278K) shifted it in the depolarized direction. Notably, the sequence of the S1-S2 linker is highly variable among Kv1 channels, making this region a promising target for selective inhibition or activation of Kv channels. Additionally, we explored how the choice of expression system can influence the potency of a novel Kv1.3 inhibitor. Factors such as cell size, morphological characteristics, endogenous currents, and auxiliary proteins all contribute to the pharmacological response of Kv channels, highlighting the need to carefully select the most appropriate expression system for drug screening. Finally, we investigated delayed drug effects that impact the trafficking or degradation of channel proteins, leading to reduced expression of mature ion channels at the plasma membrane. These effects are often missed in early drug development and may only become apparent during later stages. We propose a potential method to accelerate the onset of delayed drug effects. Removing (fetal bovine) serum from the cell culture medium seems to increase the potency of a delayed-action compound. This PhD thesis aims to deepen our understanding of Kv channel pharmacology and the factors that modulate their function. |
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Language
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English
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Publication
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Antwerp
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University of Antwerp & Ghent University
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2024
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DOI
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10.63028/10067/2079510151162165141
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Volume/pages
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128 p.
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Note
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Labro, Alain [Supervisor]
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Snyders, Dirk [Supervisor]
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Full text (open access)
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