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Four Drug-Sensitive Subunits Are Required for Maximal Effect of a Voltage Sensor-Targeted KCNQ Opener

Four Drug-Sensitive Subunits Are Required for Maximal Effect of a Voltage Sensor-Targeted KCNQ Opener

Alice W Wang, Michael C Yau, Caroline K Wang, Nazlee Sharmin, Runying Y Yang, Stephan A Pless, Harley T Kurata

J Gen Physiol. 2018 Oct 1;150(10):1432-1443.

PMID: 30166313

Abstract:

KCNQ2-5 (Kv7.2-Kv7.5) channels are strongly influenced by an emerging class of small-molecule channel activators. Retigabine is the prototypical KCNQ activator that is thought to bind within the pore. It requires the presence of a Trp side chain that is conserved among retigabine-sensitive channels but absent in the retigabine-insensitive KCNQ1 subtype. Recent work has demonstrated that certain KCNQ openers are insensitive to mutations of this conserved Trp, and that their effects are instead abolished or attenuated by mutations in the voltage-sensing domain (VSD). In this study, we investigate the stoichiometry of a VSD-targeted KCNQ2 channel activator, ICA-069673, by forming concatenated channel constructs with varying numbers of drug-insensitive subunits. In homomeric WT KCNQ2 channels, ICA-069673 strongly stabilizes an activated channel conformation, which is reflected in the pronounced deceleration of deactivation and leftward shift of the conductance-voltage relationship. A full complement of four drug-sensitive subunits is required for maximal sensitivity to ICA-069673-even a single drug-insensitive subunit leads to significantly weakened effects. In a companion article (see Yau et al. in this issue), we demonstrate very different stoichiometry for the action of retigabine on KCNQ3, for which a single retigabine-sensitive subunit enables near-maximal effect. Together, these studies highlight fundamental differences in the site and mechanism of activation between retigabine and voltage sensor-targeted KCNQ openers.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP582323168	ICA-069673		582323-16-8	Price

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