Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

BK channel inhibition by strong extracellular acidification.

ABSTRACT: Mammalian BK-type voltage- and Ca2+-dependent K+ channels are found in a wide range of cells and intracellular organelles. Among different loci, the composition of the extracellular microenvironment, including pH, may differ substantially. For example, it has been reported that BK channels are expressed in lysosomes with their extracellular side facing the strongly acidified lysosomal lumen (pH ~4.5). Here we show that BK activation is strongly and reversibly inhibited by extracellular H+, with its conductance-voltage relationship shifted by more than +100 mV at pHO 4. Our results reveal that this inhibition is mainly caused by H+ inhibition of BK voltage-sensor (VSD) activation through three acidic residues on the extracellular side of BK VSD. Given that these key residues (D133, D147, D153) are highly conserved among members in the voltage-dependent cation channel superfamily, the mechanism underlying BK inhibition by extracellular acidification might also be applicable to other members in the family.

SUBMITTER: Zhou Y

PROVIDER: S-EPMC6054526 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

BK channel inhibition by strong extracellular acidification.

Zhou Yu Y Xia Xiao-Ming XM Lingle Christopher J CJ

eLife 20180702

Mammalian BK-type voltage- and Ca<sup>2+</sup>-dependent K<sup>+</sup> channels are found in a wide range of cells and intracellular organelles. Among different loci, the composition of the extracellular microenvironment, including pH, may differ substantially. For example, it has been reported that BK channels are expressed in lysosomes with their extracellular side facing the strongly acidified lysosomal lumen (pH ~4.5). Here we show that BK activation is strongly and reversibly inhibited by e ...[more]

PMID: 29963986

Similar Datasets

Enhancement effects of martentoxin on glioma BK channel and BK channel (?+?1) subtypes.

Project description:BACKGROUND: BK channels are usually activated by membrane depolarization and cytoplasmic Ca(2+). Especially,the activity of BK channel (?+?4) can be modulated by martentoxin, a 37 residues peptide, with Ca(2+)-dependent manner. gBK channel (glioma BK channel) and BK channel (?+?1) possessed higher Ca(2+) sensitivity than other known BK channel subtypes. METHODOLOGY AND PRINCIPAL FINDINGS: The present study investigated the modulatory characteristics of martentoxin on these two BK channel subtypes by electrophysiological recordings, cell proliferation and Ca(2+) imaging. In the presence of cytoplasmic Ca(2+), martentoxin could enhance the activities of both gBK and BK channel (?+?1) subtypes in dose-dependent manner with EC(50) of 46.7 nM and 495 nM respectively, while not shift the steady-state activation of these channels. The enhancement ratio of martentoxin on gBK and BK channel (?+?1) was unrelated to the quantitative change of cytoplasmic Ca(2+) concentrations though the interaction between martentoxin and BK channel (?+?1) was accelerated under higher cytoplasmic Ca(2+). The selective BK pore blocker iberiotoxin could fully abolish the enhancement of these two BK subtypes induced by martentoxin, suggesting that the auxiliary ? subunit might contribute to the docking for martentoxin. However, in the absence of cytoplasmic Ca(2+), the activity of gBK channel would be surprisingly inhibited by martentoxin while BK channel (?+?1) couldn't be affected by the toxin. CONCLUSIONS AND SIGNIFICANCE: Thus, the results shown here provide the novel evidence that martentoxin could increase the two Ca(2+)-hypersensitive BK channel subtypes activities in a new manner and indicate that ? subunit of these BK channels plays a vital role in this enhancement by martentoxin.

| S-EPMC3060806 | biostudies-literature

Rectification ratio based determination of disulfide bonds of ?2 extracellular loop of BK channel.

Project description:Large-conductance Ca2+-activated K+ (BK) channels are composed of a pore-forming ? and a variable number of auxiliary ? subunits and play important roles in regulating excitability, action potential waveforms and firing patterns, particularly in neurons and endocrine and cardiovascular cells. The ?2 subunits increase the diversity of gating and pharmacological properties. Its extracellular loop contains eight cysteine residues, which can pair to form a high-order structure, underlying the stability of the extracellular loop of ?2 subunits and the functional effects on BK channels. However, how these cysteines form disulfide bonds still remains unclear. To address this, based on the fact that the rectification and association of BK ? to ?2 subunits are highly sensitive to disruption of the disulfide bonds in the extracellular loop of ?2, we developed a rectification ratio based assay by combining the site-directed mutagenesis, electrophysiology and enzymatic cleavage. Three disulfide bonds: C1(C84)-C5(C113), C3(C101)-C7(C148) and C6(C142)-C8C(174) are successfully deduced in ?2 subunit in complex with a BK ? subunit, which are helpful to predict structural model of ?2 subunits through computational simulation and to understand the interface between the extracellular domain of the ? subunits and the pore-forming ? subunit.

| S-EPMC6298698 | biostudies-literature

Distinct mechanisms underlying cholesterol protection against alcohol-induced BK channel inhibition and resulting vasoconstriction.

Project description:Alcohol (ethanol) at concentrations reached in blood following moderate to heavy drinking (30-80mM) reduces cerebral artery diameter via inhibition of voltage- and calcium-gated potassium channels of large conductance (BK) in cerebral artery smooth muscle. These channels consist of channel-forming ? and regulatory ?1 subunits. A high-cholesterol diet protects against ethanol-induced constriction via accumulation of cholesterol within the vasculature. The molecular mechanisms of this protection remain unknown. In the present work, we demonstrate that in vitro cholesterol enrichment of rat middle cerebral arteries significantly increased cholesterol within arterial tissues and blunted constriction by 50mM of ethanol. Ethanol-induced BK channel inhibition in inside-out patches excised from freshly isolated cerebral artery myocytes was also abolished by cholesterol enrichment. Enrichment of arteries with enantiomeric cholesterol (ent-cholesterol) also blunted BK channel inhibition and cerebral artery constriction in response to ethanol. The similar protection of cholesterol and ent-cholesterol against ethanol action indicates that this protection does not require protein site(s) that specifically sense natural cholesterol. Cholesterol-driven protection against ethanol-induced BK channel inhibition and vasoconstriction was replicated in myocytes and middle cerebral arteries of C57BL/6 mice. BK ?1 subunits are known to regulate vascular diameter and its modification by ethanol. However, blunting of an ethanol effect by in vitro cholesterol enrichment was observed in arteries and myocyte membrane patches from BK ?1 (KCNMB1) knockout mice. Thus, BK ?1 subunits are not needed for cholesterol protection against ethanol effect on BK channel function and cerebral artery diameter.

| S-EPMC5274633 | biostudies-literature

Molecular mechanisms of BK channel activation.

Project description:Large conductance, Ca(2+)-activated potassium (BK) channels are widely expressed throughout the animal kingdom and play important roles in many physiological processes, such as muscle contraction, neural transmission and hearing. These physiological roles derive from the ability of BK channels to be synergistically activated by membrane voltage, intracellular Ca(2+) and other ligands. Similar to voltage-gated K(+) channels, BK channels possess a pore-gate domain (S5-S6 transmembrane segments) and a voltage-sensor domain (S1-S4). In addition, BK channels contain a large cytoplasmic C-terminal domain that serves as the primary ligand sensor. The voltage sensor and the ligand sensor allosterically control K(+) flux through the pore-gate domain in response to various stimuli, thereby linking cellular metabolism and membrane excitability. This review summarizes the current understanding of these structural domains and their mutual interactions in voltage-, Ca(2+)- and Mg(2+)-dependent activation of the channel.

| S-EPMC2694844 | biostudies-literature

Smooth muscle cholesterol enables BK β1 subunit-mediated channel inhibition and subsequent vasoconstriction evoked by alcohol.

Project description:ObjectiveHypercholesterolemia and alcohol drinking constitute independent risk factors for cerebrovascular disease. Alcohol constricts cerebral arteries in several species, including humans. This action results from inhibition of voltage- and calcium-gated potassium channels (BK) in vascular smooth muscle cells (VSMC). BK activity is also modulated by membrane cholesterol. We investigated whether VSMC cholesterol regulates ethanol actions on BK and cerebral arteries.Methods and resultsAfter myogenic tone development, cholesterol depletion of rat, resistance-size cerebral arteries ablated ethanol-induced constriction, a result that was identical in intact and endothelium-free vessels. Cholesterol depletion reduced ethanol inhibition of BK whether the channel was studied in VSMC or after rat cerebral artery myocyte subunit (cbv1+β1) reconstitution into phospholipid bilayers. Homomeric cbv1 channels reconstituted into bilayers and VSMC BK from β1 knockout mice were both resistant to ethanol-induced inhibition. Moreover, arteries from β1 knockout mice failed to respond to ethanol even when VSMC cholesterol was kept unmodified. Remarkably, ethanol inhibition of cbv1+β1 in bilayers and wt mouse VSMC BK were drastically blunted by cholesterol depletion. Consistently, cholesterol depletion suppressed ethanol constriction of wt mouse arteries.ConclusionVSMC cholesterol and BK β1 are both required for ethanol inhibition of BK and the resulting cerebral artery constriction, with health-related implications for manipulating cholesterol levels in alcohol-induced cerebrovascular disease.

| S-EPMC3366592 | biostudies-literature

An extracellular domain of the accessory ?1 subunit is required for modulating BK channel voltage sensor and gate.

Project description:A family of tissue-specific auxiliary ? subunits modulates large conductance voltage- and calcium-activated potassium (BK) channel gating properties to suit their diverse functions. Paradoxically, ? subunits both promote BK channel activation through a stabilization of voltage sensor activation and reduce BK channel openings through an increased energetic barrier of the closed-to-open transition. The molecular determinants underlying ? subunit function, including the dual gating effects, remain unknown. In this study, we report the first identification of a ?1 functional domain consisting of Y74, S104, Y105, and I106 residues located in the extracellular loop of ?1. These amino acids reside within two regions of highest conservation among related ?1, ?2, and ?4 subunits. Analysis in the context of the Horrigan-Aldrich gating model revealed that this domain functions to both promote voltage sensor activation and also reduce intrinsic gating. Free energy calculations suggest that the dual effects of the ?1 Y74 and S104-I106 domains can be largely accounted for by a relative destabilization of channels in open states that have few voltage sensors activated. These results suggest a unique and novel mechanism for ? subunit modulation of voltage-gated potassium channels wherein interactions between extracellular ? subunit residues with the external portions of the gate and voltage sensor regulate channel opening.

| S-EPMC3250105 | biostudies-literature

Metabolic inhibition reduces cardiac L-type Ca2+ channel current due to acidification caused by ATP hydrolysis.

Project description:Metabolic stress evoked by myocardial ischemia leads to impairment of cardiac excitation and contractility. We studied the mechanisms by which metabolic inhibition affects the activity of L-type Ca2+ channels (LTCCs) in frog ventricular myocytes. Metabolic inhibition induced by the protonophore FCCP (as well as by 2,4- dinitrophenol, sodium azide or antimycin A) resulted in a dose-dependent reduction of LTCC current (ICa,L) which was more pronounced during ?-adrenergic stimulation with isoprenaline. ICa,L was still reduced by metabolic inhibition even in the presence of 3 mM intracellular ATP, or when the cell was dialysed with cAMP or ATP-?-S to induce irreversible thiophosphorylation of LTCCs, indicating that reduction in ICa,L is not due to ATP depletion and/or reduced phosphorylation of the channels. However, the effect of metabolic inhibition on ICa,L was strongly attenuated when the mitochondrial F1F0-ATP-synthase was blocked by oligomycin or when the cells were dialysed with the non-hydrolysable ATP analogue AMP-PCP. Moreover, increasing the intracellular pH buffering capacity or intracellular dialysis of the myocytes with an alkaline solution strongly attenuated the inhibitory effect of FCCP on ICa,L. Thus, our data demonstrate that metabolic inhibition leads to excessive ATP hydrolysis by the mitochondrial F1F0-ATP-synthase operating in the reverse mode and this results in intracellular acidosis causing the suppression of ICa,L. Limiting ATP break-down by F1F0-ATP-synthase and the consecutive development of intracellular acidosis might thus represent a potential therapeutic approach for maintaining a normal cardiac function during ischemia.

| S-EPMC5578678 | biostudies-literature

BK channel activation: structural and functional insights.

Project description:The voltage- and Ca(2+)-activated K(+) (BK) channels are involved in the regulation of neurotransmitter release and neuronal excitability. Structurally, BK channels are homologous to voltage- and ligand-gated K(+) channels, having a voltage sensor and pore as the membrane-spanning domain and a cytosolic domain containing metal binding sites. Recently published electron cryomicroscopy (cryo-EM) and X-ray crystallographic structures of the BK channel provided the first glimpse into the assembly of these domains, corroborating the close interactions among these domains during channel gating that have been suggested by functional studies. This review discusses these latest findings and an emerging new understanding about BK channel gating and implications for diseases such as epilepsy, in which mutations in BK channel genes have been associated.

| S-EPMC2929326 | biostudies-literature

Solution structure of extracellular loop of human ?4 subunit of BK channel and its biological implication on ChTX sensitivity.

Project description:Large-conductance Ca2+- and voltage-dependent K+ (BK) channels display diverse biological functions while their pore-forming ? subunit is coded by a single Slo1 gene. The variety of BK channels is correlated with the effects of BK? coexpression with auxiliary ? (?1-?4) subunits, as well as newly defined ? subunits. Charybdotoxin (ChTX) blocks BK channel through physically occluding the K+-conduction pore. Human brain enriched ?4 subunit (h?4) alters the conductance-voltage curve, slows activation and deactivation time courses of BK channels. Its extracellular loop (h?4-loop) specifically impedes ChTX to bind BK channel pore. However, the structure of ?4 subunit's extracellular loop and the molecular mechanism for gating kinetics, toxin sensitivity of BK channels regulated by ?4 are still unclear. To address them, here, we first identified four disulfide bonds in h?4-loop by mass spectroscopy and NMR techniques. Then we determined its three-dimensional solution structure, performed NMR titration and electrophysiological analysis, and found that residue Asn123 of ?4 subunit regulated the gating and pharmacological characteristics of BK channel. Finally, by constructing structure models of BK?/?4 and thermodynamic double-mutant cycle analysis, we proposed that BK? subunit might interact with ?4 subunit through the conserved residue Glu264(BK?) coupling with residue Asn123(?4).

| S-EPMC5854672 | biostudies-literature

Unoprostone activation of BK (KCa1.1) channel splice variants.

Project description:This investigation was conducted to study the relationship between intracellular Ca(2+) and activation of large conductance Ca(2+)-activated K(+) (BK) currents by unoprostone, the first synthetic docosanoid. We used HEK293 cells stably transfected with two BK channel splice variants, one sensitive to unoprostone and the other insensitive. We examined the effects of unoprostone on channel activity in excised inside-out patches and cell-attached patches. The half-maximal stimulation of the sensitive BK channels by Ca(2+) was shifted from 3.4±0.017 nM to 0.81±.0058 nM in the presence of 10 nM unoprostone. There was no effect on insensitive channels even at unoprostone concentrations as high as 1000 nM. There was no effect of unoprostone on the voltage dependence of the BK channels. Changes in open probability and effects of Ca(2+) and unoprostone were best described by a synergistic binding model. These data would suggest that Ca(2+) and unoprostone were binding to sites close to one another on the channel protein and that unoprostone binding causes the affinity of the calcium binding site to increase. This idea is consistent with three dimensional models of the Ca(2+) binding site and a putative unoprostone binding domain. Our results have important implications for the clinical use of unoprostone to activate BK channels. Channel activation will be limited if intracellular Ca(2+) is not elevated.

| S-EPMC4598293 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data