A hydrophobic barrier deep within the inner pore of the TWIK-1 K2P potassium channel

Aryal, Prafulla; Abd-Wahab, Firdaus; Bucci, Giovanna; Sansom, Mark S. P.; Tucker, Stephen J.

doi:10.1038/ncomms5377

Cited by 114 publications

(159 citation statements)

References 51 publications

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“…Through mutagenesis of F80, we found that both the size and hydrophobic nature of the neck contribute to its role as an ion barrier when Ca 2+ is absent. In this regard, the neck appears similar to the so-called "hydrophobic gates" identified in other ion channels (33)(34)(35). By this theory, the bulky hydrophobic side chains at the neck region would prevent "wetting" of the channel pore by forming a "vapor lock" (33), blocking the passage of ions.…”

Section: +mentioning

confidence: 72%

Distinct regions that control ion selectivity and calcium-dependent activation in the bestrophin ion channel

Vaisey

Miller

Long

2016

Proc. Natl. Acad. Sci. U.S.A.

135

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Cytoplasmic calcium (Ca 2+ ) activates the bestrophin anion channel, allowing chloride ions to flow down their electrochemical gradient. Mutations in bestrophin 1 (BEST1) cause macular degenerative disorders. Previously, we determined an X-ray structure of chicken BEST1 that revealed the architecture of the channel. Here, we present electrophysiological studies of purified wild-type and mutant BEST1 channels and an X-ray structure of a Ca 2+ -independent mutant. From these experiments, we identify regions of BEST1 responsible for Ca 2+ activation and ion selectivity. A "Ca 2+ clasp" within the channel's intracellular region acts as a sensor of cytoplasmic Ca 2+ . Alanine substitutions within a hydrophobic "neck" of the pore, which widen it, cause the channel to be constitutively active, irrespective of Ca 2+. We conclude that the primary function of the neck is as a "gate" that controls chloride permeation in a Ca 2+ -dependent manner. In contrast to what others have proposed, we find that the neck is not a major contributor to the channel's ion selectivity. We find that mutation of a cytosolic "aperture" of the pore does not perturb the Ca 2+ dependence of the channel or its preference for anions over cations, but its mutation dramatically alters relative permeabilities among anions. The data suggest that the aperture functions as a size-selective filter that permits the passage of small entities such as partially dehydrated chloride ions while excluding larger molecules such as amino acids. Thus, unlike ion channels that have a single "selectivity filter," in bestrophin, distinct regions of the pore govern anion-vs.-cation selectivity and the relative permeabilities among anions.calcium-activated chloride channel | CaCC | ion selectivity | channel gating | ion channel biophysics E ukaryotic bestrophin proteins constitute a family of Ca 2+

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Section: +mentioning

confidence: 72%

Distinct regions that control ion selectivity and calcium-dependent activation in the bestrophin ion channel

Vaisey

Miller

Long

2016

Proc. Natl. Acad. Sci. U.S.A.

135

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“…In TREK-1 and TWIK-1 tandem pore potassium channels, the gate which regulates potassium flow resides deep in the pore (Piechotta et al, 2011;Aryal et al, 2014). A hydrophobic "cuff" in the TWIK-1 pore created by , and Leu-239 of TASK-3 align with those of TWIK-1 and create a similar hydrophobic cuff in the TASK-3 pore (Figs.…”

Section: Discussionmentioning

confidence: 99%

Breathing Stimulant Compounds Inhibit TASK-3 Potassium Channel Function Likely by Binding at a Common Site in the Channel Pore

et al. 2015

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Compounds PKTHPP (1-{1-[6-(biphenyl-4-ylcarbonyl)-5,6,7,8-tetrahydropyrido[4,3-d]-pyrimidin-4-yl]piperidin-4-yl}propan-1-one), A1899 (2ʹ9-[(4-methoxybenzoylamino)methyl]biphenyl-2-carboxylic acid 2,4-difluorobenzylamide), and doxapram inhibit TASK-1 (KCNK3) and TASK-3 (KCNK9) tandem pore (K 2P ) potassium channel function and stimulate breathing. To better understand the molecular mechanism(s) of action of these drugs, we undertook studies to identify amino acid residues in the TASK-3 protein that mediate this inhibition. Guided by homology modeling and molecular docking, we hypothesized that PKTHPP and A1899 bind in the TASK-3 intracellular pore. To test our hypothesis, we mutated each residue in or near the predicted PKTHPP and A1899 binding site (residues 118-128 and 228-248), individually, to a negatively charged aspartate. We quantified each mutation's effect on TASK-3 potassium channel concentration response to PKTHPP. Studies were conducted on TASK-3 transiently expressed in Fischer rat thyroid epithelial monolayers; channel function was measured in an Ussing chamber. TASK-3 pore mutations at residues 122 (L122D, E, or K) and 236 (G236D) caused the IC 50 of PKTHPP to increase more than 1000-fold. TASK-3 mutants L122D, G236D, L239D, and V242D were resistant to block by PKTHPP, A1899, and doxapram. Our data are consistent with a model in which breathing stimulant compounds PKTHPP, A1899, and doxapram inhibit TASK-3 function by binding at a common site within the channel intracellular pore region, although binding outside the channel pore cannot yet be excluded.

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“…The majority of substances exerts an inhibitory effect, is semi-selective and thus allows no distinction between channel subtypes. Recently the first crystal structures of K 2P -channels (TWIK-1, TRAAK) were published [48][49][50]. These studies do not only improve our biophysical knowledge of these channels, but they also facilitate the generation of new specific modulators.…”

Section: Discussionmentioning

confidence: 99%

TASK, TREK & Co.: a mutable potassium channel family for diverse tasks in the brain

et al. 2015

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A hydrophobic barrier deep within the inner pore of the TWIK-1 K2P potassium channel

Cited by 114 publications

References 51 publications

Distinct regions that control ion selectivity and calcium-dependent activation in the bestrophin ion channel

Distinct regions that control ion selectivity and calcium-dependent activation in the bestrophin ion channel

Breathing Stimulant Compounds Inhibit TASK-3 Potassium Channel Function Likely by Binding at a Common Site in the Channel Pore

TASK, TREK & Co.: a mutable potassium channel family for diverse tasks in the brain

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