Pharmacology and gating of SLO2.1, an intracellular Na+ activated potassium channel

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Publication Type dissertation
School or College College of Pharmacy
Department Pharmaceutics & Pharmaceutical Chemistry
Author Garg, Priyanka
Title Pharmacology and gating of SLO2.1, an intracellular Na+ activated potassium channel
Date 2014-12
Description Slo2.1 is an intracellular Na+-regulated K+ channel that is abundantly expressed in the brain and the heart. Although Slo2.1 channels are believed to provide cardioprotection under ischemic conditions in the heart, the exact physiological or pathophysiological significance of these channels is still unclear, in part because of the lack of pharmacological probes. While the fenamate niflumic acid (NFA) is the first compound shown to activate Slo2.1 channels, its low potency and reduced specificity limits its usefulness as a tool to study these channels in physiological conditions. In this study, I report that fenamates other than NFA, including flufenamic acid, mefenamic acid, tolfenamic acid, meclofenamic acid, and a phenyl acetic acid derivative, diclofenac, are low-potency modulators of Slo2.1 channels. In addition, N-phenylanthranilic acid was established as the minimal pharmacophore for the activation of Slo2.1. The structural basis of the activation gate in Slo channels is controversial. Emerging evidence suggests that the selectivity filter (SF) functions as the activation gate in Ca2+-activated Slo1 and cyclic nucleotide-gated (CNG) channels, unlike Kv channels where the S6 bundle crossing forms the canonical activation gate. Based on my studies, the SF also appears to serve as a gate in Slo2.1 channels. Two residues in the S6 segment, Pro271 and Glu275, were found to be vital for maintaining the intracellular bundle crossing in an open configuration. iv The pore helix residue Phe240 exhibited constitutive channel activity when substituted with polar residues. Further mutational analysis suggests that Phe240 forms a hydrophobic interaction with Leu209 in the S5 segment and Phe258, Met262, and Ala266 in the S6 segment. It is proposed that these interactions favor the closed state of the SF gate under normal low [Na+]i conditions. Collectively, these findings suggest that similar to CNG and Slo1 channels, dynamic rearrangement of S5 and S6 segments in Slo2.1 in response to Na+ binding is allosterically coupled via the pore helix to conformational changes at the SF gate that mediates channel opening. Finally, a long standing controversy prevails regarding the [ATP]i regulation of Slo2.1 channels. This dissertation provides both direct and indirect evidence that intracellular ATP has no effect on Slo2.1 channels.
Type Text
Publisher University of Utah
Subject MESH Potassium Channels; Ion Channel Gating; Potassium Channels, Voltage-Gated; Action Potentials; Ion Transport; Niflumic Acid; Fenamates; Flufenamic Acid; Meclofenamic Acid; Channelopathies; Adenosine Triphosphate; Myocardial Ischemia; Long QT Syndrome; Cystic Fibrosis; Xenopus laevis; Large-Conductance Calcium-Activated Potassium Channel alpha Subunits
Dissertation Institution University of Utah
Dissertation Name Doctor of Philosophy
Language eng
Relation is Version of Digital reproduction of Pharmacology and Gating of SLO2.1, An Intracellular Na+ Activated Potassium Channel
Rights Management Copyright © Priyanka Garg 2014
Format Medium application/pdf
Format Extent 123,954,638 bytes
Source Original in Marriott Library Special Collections.
ARK ark:/87278/s6bg5xb0
Setname ir_etd
ID 197472
Reference URL https://collections.lib.utah.edu/ark:/87278/s6bg5xb0
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