Journal article
Basis for allosteric open-state stabilization of voltage-gated potassium channels by intracellular cations
The Journal of general physiology, Vol.140(5), pp.495-511
11/2012
DOI: 10.1085/jgp.201210823
PMCID: PMC3483119
PMID: 23071269
Abstract
The open state of voltage-gated potassium (Kv) channels is associated with an increased stability relative to the pre-open closed states and is reflected by a slowing of OFF gating currents after channel opening. The basis for this stabilization is usually assigned to intrinsic structural features of the open pore. We have studied the gating currents of Kv1.2 channels and found that the stabilization of the open state is instead conferred largely by the presence of cations occupying the inner cavity of the channel. Large impermeant intracellular cations such as N-methyl-d-glucamine (NMG(+)) and tetraethylammonium cause severe slowing of channel closure and gating currents, whereas the smaller cation, Cs(+), displays a more moderate effect on voltage sensor return. A nonconducting mutant also displays significant open state stabilization in the presence of intracellular K(+), suggesting that K(+) ions in the intracellular cavity also slow pore closure. A mutation in the S6 segment used previously to enlarge the inner cavity (Kv1.2-I402C) relieves the slowing of OFF gating currents in the presence of the large NMG(+) ion, suggesting that the interaction site for stabilizing ions resides within the inner cavity and creates an energetic barrier to pore closure. The physiological significance of ionic occupation of the inner cavity is underscored by the threefold slowing of ionic current deactivation in the wild-type channel compared with Kv1.2-I402C. The data suggest that internal ions, including physiological concentrations of K(+), allosterically regulate the deactivation kinetics of the Kv1.2 channel by impairing pore closure and limiting the return of voltage sensors. This may represent a primary mechanism by which Kv channel deactivation kinetics is linked to ion permeation and reveals a novel role for channel inner cavity residues to indirectly regulate voltage sensor dynamics.
Details
- Title: Subtitle
- Basis for allosteric open-state stabilization of voltage-gated potassium channels by intracellular cations
- Creators
- Samuel J Goodchild - Department of Anesthesiology, Pharmacology, and Therapeutics, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, CanadaHongjian XuZeineb Es-Salah-LamoureuxChristopher A AhernDavid Fedida
- Resource Type
- Journal article
- Publication Details
- The Journal of general physiology, Vol.140(5), pp.495-511
- DOI
- 10.1085/jgp.201210823
- PMID
- 23071269
- PMCID
- PMC3483119
- NLM abbreviation
- J Gen Physiol
- ISSN
- 0022-1295
- eISSN
- 1540-7748
- Publisher
- United States
- Grant note
- Canadian Institutes of Health Research
- Language
- English
- Date published
- 11/2012
- Academic Unit
- Molecular Physiology and Biophysics; Iowa Neuroscience Institute
- Record Identifier
- 9984070433502771
Metrics
34 Record Views