Modulation of K+ channel N-type inactivation by sulfhydration through hydrogen sulfide and polysulfides
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Fast N-type inactivation of voltage-gated K+ (Kv) channels is important in fine-tuning of cellular excitability. To serve diverse cellular needs, N-type inactivation is regulated by numerous mechanisms. Here, we address how reactive sulfur species—the gaseous messenger H2S and polysulfides—affect N-type inactivation of the mammalian Kv channels Kv1.4 and Kv3.4. In both channels, the H2S donor NaHS slowed down inactivation with varying potency depending on the “aging” of NaHS solution. Polysulfides were > 1000 times more effective than NaHS with the potency increasing with the number of sulfur atoms (Na2S2 < Na2S3 < Na2S4). In Kv1.4, C13 in the N-terminal ball domain mediates the slowing of inactivation. In recombinant protein exposed to NaHS or Na2S4, a sulfur atom is incorporated at C13 in the protein. In Kv3.4, the N terminus harbors two cysteine residues (C6, C24), and C6 is of primary importance for channel regulation by H2S and polysulfides, with a minor contribution from C24. To fully eliminate the dependence of N-type inactivation on sulfhydration, both cysteine residues must be removed (C6S:C24S). Sulfhydration of a single cysteine residue in the ball-and-chain domain modulates the speed of inactivation but does not remove it entirely. In both Kv1.4 and Kv3.4, polysulfides affected the N-terminal cysteine residues when assayed in the whole-cell configuration; on-cell recordings confirmed that polysulfides also modulate K+ channel inactivation with undisturbed cytosol. These findings have collectively identified reactive sulfur species as potent modulators of N-type inactivation in mammalian Kv channels.
KeywordsHydrogen sulfide Sulfhydration K+ channel inactivation Kcna4 Kcnc4 Reactive sulfur species
dorsal root ganglion
voltage-gated potassium channel
sodium hydrogen sulfide
reactive nitrogen species
reactive oxygen species
reduction-oxidation sensitive green fluorescent protein 2
reactive sulfur species
We thank Dr. Ilka Wittig (Frankfurt, Germany) for helpful comments on the mass spectrometry experiment.
This work was supported by grants of the German Research Foundation RTG 1715 and RTG 2155 (ProMoAge) (S.H.H.). T.H. was supported in part by the National Institutes of Health grant GM121375.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All procedures performed in studies involving animals were in accordance with the ethical standards of the institution or practice at which the studies were conducted. This article does not contain any studies with human participants performed by any of the authors.
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