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Thomas J. Jentsch - One of the best experts on this subject based on the ideXlab platform.
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functional and structural analysis of clc k Chloride Channels involved in renal disease
Journal of Biological Chemistry, 2000Co-Authors: Siegfried Waldegger, Thomas J. JentschAbstract:ClC-K Channels belong to the CLC family of Chloride Channels and are predominantly expressed in the kidney. Genetic evidence suggests their involvement in transepithelial transport of Chloride in distal nephron segments; ClC-K1 gene deletion leads to nephrogenic diabetes insipidus in mice, and mutations of the hClC-Kb gene cause Bartter's syndrome type III in humans. Expression of rClC-K1 in Xenopus oocytes yielded voltage-independent currents that were pH-sensitive, had a Br(-) > NO(3)(-) = Cl(-) > I(-) conductance sequence, and were activated by extracellular calcium. A glutamate for valine exchange at amino acid position 166 induced strong voltage dependence and altered the conductance sequence of ClC-K1. This demonstrates that rClC-K1 indeed functions as an anion channel. By contrast, we did not detect currents upon hClC-Kb expression in Xenopus oocytes. Using a chimeric approach, we defined a protein domain that, when replaced by that of rClC-K1, allowed the functional expression of a chimera consisting predominantly of hClC-Kb. Its currents were linear and were inhibited by extracellular acidification. Contrasting with rClC-K1, they displayed a Cl(-) > Br(-)> I(-) > NO(3)(-) conductance sequence and were not augmented by extracellular calcium. Insertion of point mutations associated with Bartter's syndrome type III destroyed channel activity. We conclude that ClC-K proteins form constitutively open Chloride Channels with distinct physiological characteristics.
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From Tonus to Tonicity Physiology of CLC Chloride Channels
Journal of The American Society of Nephrology, 2000Co-Authors: Siegfried Waldegger, Thomas J. JentschAbstract:Abstract . Chloride Channels are involved in a multitude of physiologic processes ranging from basal cellular functions such as cell volume regulation and acidification of intracellular vesicles to more specialized mechanisms such as vectorial transepithelial transport and regulation of cellular excitability. This plethora of functions is accomplished by numerous functionally highly diverse Chloride Channels that are only partially identified at the molecular level. The CLC family of Chloride Channels comprises at present nine members in mammals that differ with respect to biophysical properties, cellular compartmentalization, and tissue distribution. Their common structural features include a predicted topology model with 10 to 12 transmembrane regions together with two C-terminal CBS domains. Loss of function mutations affecting three different members of the CLC channel family lead to three human inherited diseases : myotonia congenita, Dent9s disease, and Bartter9s syndrome. These diseases, together with the diabetes insipidus symptoms of a knockout mouse model, emphasize the physiologic relevance of this ion channel family.
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CLC Chloride Channels in Caenorhabditis elegans.
Journal of Biological Chemistry, 1999Co-Authors: Antje M. Schriever, Thomas Friedrich, Michael Pusch, Thomas J. JentschAbstract:Abstract The genome of the nematode Caenorhabditis elegans encodes six putative Chloride Channels (CeCLC-1 through CeCLC-6) that represent all three known branches of the mammalian CLC gene family. Using promoter fragments to drive the expression of the green fluorescent protein, CeCLC-2, -3, and -4 expression was studied in transgenic C. elegans. CeCLC-4 was specifically expressed in the large H-shaped excretory cell, where it was co-expressed with CeCLC-3, which is also expressed in other cells, including neurons, muscles, and epithelial cells. Also, CeCLC-2 was expressed in several cells of the nervous system, intestinal cells, and vulval muscle cells. Similar to mammalian CLC proteins, only two nematode CLC Channels elicited detectable plasma membrane currents inXenopus oocytes. CeCLC-3 currents were inwardly rectifying and were activated by positive prepulses. Its complex gating behavior can be explained by two gates, at least one of which depends on extracellular anions. In this respect it resembles some mammalian Chloride Channels with which it also shares a preference of Chloride over iodide. C. elegans thus provides new opportunities to understand common mechanisms underlying structure and function in CLC Channels and will allow for a genetic dissection of Chloride Channels in this simple model organism.
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Molecular physiology of renal Chloride Channels.
Current Opinion in Nephrology and Hypertension, 1998Co-Authors: Klaus Steinmeyer, Thomas J. JentschAbstract:Chloride Channels are present In all cells of the kidney. Physiological studies have revealed a bewildering variety of kidney Chloride Channels, but only in the past few years has molecular information on some of these Channels emerged. This review will focus on cloned Chloride Channels expressed in
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Chloride Channels: an emerging molecular picture
BioEssays, 1997Co-Authors: Thomas J. Jentsch, Willy GüntherAbstract:Chloride Channels are probably found in every cell, from bacteria to mammals. Their physiological tasks range from cell volume regulation to stabilization of the membrane potential, signal transduction, transepithelial transport and acidification of intracellular organelles. These different functions require the presence of many distinct Chloride Channels, which are differentially expressed and regulated by various stimuli. These include various intracellular messengers (like calcium and cyclic AMP), pH, extracellular ligands and transmembrane voltage. Three major structural classes of Chloride Channels are known to date, but there may be others not yet identified. After an overview of the general functions of Chloride Channels, this review will focus on these cloned Chloride Channels: the CLC Chloride channel family, which includes voltage-gated Chloride Channels, and the cystic fibrosis transmembrane regulator (CFTR), which performs other functions in addition to being a Chloride channel. Finally, a short section deals with GABA and glycine receptors. Diseases resulting from Chloride channel defects will be specially emphasized, together with the somewhat limited information about how these proteins work at the molecular level.
Karol Ondrias - One of the best experts on this subject based on the ideXlab platform.
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Inhibitory effect of glybenclamide on mitochondrial Chloride Channels from rat heart.
Biochemical and Biophysical Research Communications, 2013Co-Authors: Viera Kominkova, Karol Ondrias, Zuzana TomaskovaAbstract:Abstract Glybenclamide is used as a pharmacological tool in studies of mitochondrial functions supposing its main role to block ATP-dependent potassium (KATP) channel. The aim of this study was to test whether glybenclamide might interact with the mitochondrial Chloride Channels. Mitochondrial membranes, isolated from rat heart muscle, were incorporated into lipid bilayer membrane and single Chloride channel currents were measured in 250/50 mM KCl cis/trans solutions. The observed Chloride Channels (N = 11) with mean conductance 120 ± 14 pS were sensitive to glybenclamide, which decreased the open probability (IC50 = 129 μM) and affected the channel gating kinetics (IC50 = 12 μM) by perturbing its open state. It did not influence the channel conductance or reversal potential. These results indicate that glybenclamide interacts with Chloride Channels what should be taken into consideration, when glybenclamide is used as a specific inhibitor of KATP Channels.
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Mitochondrial Chloride Channels – What are they for?
FEBS Letters, 2010Co-Authors: Zuzana Tomaskova, Karol OndriasAbstract:This minireview focuses on observation of the properties, functional significance, and modulation of single Chloride Channels in the mitochondrial inner membrane using two electrophysiological methods – the patch-clamp and bilayer lipid membrane methods. Measurements of parameters such as conductance, Cl−/K+ selectivity, voltage or pH dependence as well as their modulation by endogenous and exogenous compounds using individual mitochondrial Chloride Channels result in an unexpectedly wide range of values. This paper discusses the origin of this wide variety of channel parameters and the possible involvement of these Channels in mitochondrial membrane potential oscillations, apoptosis, carrier function, and mitochondrial fusion and fission.
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Modulation of intracellular Chloride Channels by ATP and Mg2+
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2010Co-Authors: Viera Kominkova, Adam Szewczyk, Zuzana Tomaskova, Lubica Malekova, Peter Slezak, Karol OndriasAbstract:AbstractWe report the effects of ATP and Mg2+ on the activity of intracellular Chloride Channels. Mitochondrial and lysosomal membrane vesicles isolated from rat hearts were incorporated into bilayer lipid membranes, and single Chloride channel currents were measured. The observed Chloride Channels (n=112) possessed a wide variation in single channel parameters and sensitivities to ATP. ATP (0.5–2mmol/l) modulated and/or inhibited the Chloride channel activities (n=38/112) in a concentration-dependent manner. The inhibition effect was irreversible (n=5/93) or reversible (n=15/93). The non-hydrolysable ATP analogue AMP-PNP had a similar inhibition effect as ATP, indicating that phosphorylation did not play a role in the ATP inhibition effect. ATP modulated the gating properties of the Channels (n=6/93), decreased the Channels' open dwell times and increased the gating transition rates. ATP (0.5–2mmol/l) without the presence of Mg2+ decreased the Chloride channel current (n=12/14), whereas Mg2+ significantly reversed the effect (n=4/4). We suggest that ATP-intracellular Chloride channel interactions and Mg2+ modulation of these interactions may regulate different physiological and pathological processes
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Inhibitory effect of DIDS, NPPB, and phloretin on intracellular Chloride Channels.
Pflügers Archiv: European Journal of Physiology, 2007Co-Authors: Lubica Malekova, Jana Tomaskova, Marie Nováková, Peter Stefanik, Juraj Kopacek, Boris Lakatoš, Silvia Pastorekova, Olga Krizanova, Albert Breier, Karol OndriasAbstract:We studied the effects of the Chloride channel blockers, 5-nitro-2-(phenylpropylamino)-benzoate (NPPB), dihydro-4,4′ diisothiocyanostilbene-2,2′-disulphonic acid (DIDS), and phloretin on H2O2-induced primary culture cardiomyocyte apoptosis and activity of intracellular Chloride Channels obtained from rat heart mitochondrial and lysosomal vesicles. The Chloride channel blockers (100 μmol/l) inhibited the H2O2-induced cardiomyocytes apoptosis. We characterized the effect of the blockers on single channel properties of the Chloride Channels derived from the mitochondrial and lysosomal vesicles incorporated into a bilayer lipid membrane. The single Chloride channel currents were measured in 250:50 mmol/l KCl cis/trans solutions. NPPB, DIDS, and phloretin inhibited the Chloride Channels by decreasing the channel open probability in a concentration-dependent manner with EC50 values of 42, 7, and 20 μmol/l, respectively. NPPB and phloretin inhibited the channel’s conductance and open dwell time, indicating that they could affect the Chloride selective filter, pore permeability, and gating mechanism of the Chloride Channels. DIDS and NPPB inhibited the Channels from the other side than bongkrekic acid and carboxyatractyloside. The results may contribute to understand a possible involvement of intracellular Chloride Channels in apoptosis and cardioprotection.
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Inhibitory effect of DIDS, NPPB, and phloretin on intracellular Chloride Channels.
Pflugers Archiv : European journal of physiology, 2007Co-Authors: Lubica Malekova, Jana Tomaskova, Marie Nováková, Peter Stefanik, Juraj Kopacek, Boris Lakatoš, Silvia Pastorekova, Olga Krizanova, Albert Breier, Karol OndriasAbstract:We studied the effects of the Chloride channel blockers, 5-nitro-2-(phenylpropylamino)-benzoate (NPPB), dihydro-4,4′ diisothiocyanostilbene-2,2′-disulphonic acid (DIDS), and phloretin on H2O2-induced primary culture cardiomyocyte apoptosis and activity of intracellular Chloride Channels obtained from rat heart mitochondrial and lysosomal vesicles. The Chloride channel blockers (100 μmol/l) inhibited the H2O2-induced cardiomyocytes apoptosis. We characterized the effect of the blockers on single channel properties of the Chloride Channels derived from the mitochondrial and lysosomal vesicles incorporated into a bilayer lipid membrane. The single Chloride channel currents were measured in 250:50 mmol/l KCl cis/trans solutions. NPPB, DIDS, and phloretin inhibited the Chloride Channels by decreasing the channel open probability in a concentration-dependent manner with EC50 values of 42, 7, and 20 μmol/l, respectively. NPPB and phloretin inhibited the channel’s conductance and open dwell time, indicating that they could affect the Chloride selective filter, pore permeability, and gating mechanism of the Chloride Channels. DIDS and NPPB inhibited the Channels from the other side than bongkrekic acid and carboxyatractyloside. The results may contribute to understand a possible involvement of intracellular Chloride Channels in apoptosis and cardioprotection.
George Gallos - One of the best experts on this subject based on the ideXlab platform.
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calcium activated Chloride Channels anoctamin 1 and 2 promote murine uterine smooth muscle contractility
American Journal of Obstetrics and Gynecology, 2014Co-Authors: Kyra Bernstein, Jennifer Danielsson, Joy Vink, Ronald J Wapner, Hiromi Wakita, George GallosAbstract:Objective To determine the presence of calcium activated Chloride Channels anoctamin 1 (ANO1) and 2 (ANO2) in human and murine uterine smooth muscle (MUSM) and evaluate the physiologic role for these ion Channels in murine myometrial contractility. Study Design We performed reverse transcription polymerase chain reaction to determine whether ANO1 and 2 are expressed in human and murine uterine tissue to validate the study of this protein in mouse models. Immunohistochemical staining of ANO1 and 2 was then performed to determine protein expression in murine myometrial tissue. The function of ANO1 and 2 in murine uterine tissue was evaluated using electrophysiologic studies, organ bath, and calcium flux experiments. Results ANO1 and 2 are expressed in human and MUSM cells. Functional studies show that selective antagonism of these Channels promotes relaxation of spontaneous MUSM contractions. Blockade of ANO1 and 2 inhibits both agonist-induced and spontaneous transient inward currents and abolishes G-protein coupled receptor (oxytocin) mediated elevations in intracellular calcium. Conclusion The calcium activated Chloride Channels ANO1 and 2 are present in human and murine myometrial tissue and may provide novel potential therapeutic targets to achieve effective tocolysis.
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Calcium-activated Chloride Channels anoctamin 1 and 2 promote murine uterine smooth muscle contractility.
American journal of obstetrics and gynecology, 2014Co-Authors: Kyra Bernstein, Jennifer Danielsson, Ronald J Wapner, Hiromi Wakita, Joy Y Vink, George GallosAbstract:To determine the presence of calcium activated Chloride Channels anoctamin 1 (ANO1) and 2 (ANO2) in human and murine uterine smooth muscle (MUSM) and evaluate the physiologic role for these ion Channels in murine myometrial contractility. We performed reverse transcription polymerase chain reaction to determine whether ANO1 and 2 are expressed in human and murine uterine tissue to validate the study of this protein in mouse models. Immunohistochemical staining of ANO1 and 2 was then performed to determine protein expression in murine myometrial tissue. The function of ANO1 and 2 in murine uterine tissue was evaluated using electrophysiologic studies, organ bath, and calcium flux experiments. ANO1 and 2 are expressed in human and MUSM cells. Functional studies show that selective antagonism of these Channels promotes relaxation of spontaneous MUSM contractions. Blockade of ANO1 and 2 inhibits both agonist-induced and spontaneous transient inward currents and abolishes G-protein coupled receptor (oxytocin) mediated elevations in intracellular calcium. The calcium activated Chloride Channels ANO1 and 2 are present in human and murine myometrial tissue and may provide novel potential therapeutic targets to achieve effective tocolysis. Copyright © 2014 Elsevier Inc. All rights reserved.
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Calcium-Activated Chloride Channels
Calcium Signaling In Airway Smooth Muscle Cells, 2013Co-Authors: George Gallos, Charles W EmalaAbstract:Emerging functional evidence demonstrates the importance of membrane potential in the regulation of many intracellular signaling processes. The efflux of Chloride through the plasma membrane has been identified as a major contributor to plasma membrane depolarization in airway smooth muscle. Early studies demonstrated that calcium arising from intracellular sources and released by ryanodine or IP3 receptor activation on the sarcoplasmic-reticulum-induced plasma membrane Chloride currents. Moreover, external calcium entry through voltage-dependent calcium Channels was shown to augment calcium-activated Chloride currents. One of the earliest studies in this area suggested a role for Chloride influencing uptake and release of calcium from the sarcoplasmic reticulum in addition to Chloride flux’s effect on plasma membrane electrical potential. Recently the elusive proteins responsible for calcium-activated Chloride currents in many cells (TMEM16/anoctamin family) were cloned, which has renewed interest in the field of calcium-activated Chloride Channels (CaCCs). Anoctamin 1 has been identified on the apical side of airway epithelium, is critical to fluid secretion, and has been associated with increased mucin secretion in asthmatics. Anoctamin 1 is critical to the development of the trachea as global knockout mice exhibit severe tracheomalacia. Anoctamin 1 has been immunochemically localized to airway smooth muscle and human bronchi were shown to contract less effectively in the presence of benzbromarone, an antagonist of these Channels. Studies of the TMEM16/anoctamin family of CaCCs are revolutionizing the understanding of calcium-activated Chloride currents in many cell types, and emerging evidence suggests that this channel also contributes to the regulation of airway smooth muscle tone.
Kyra Bernstein - One of the best experts on this subject based on the ideXlab platform.
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calcium activated Chloride Channels anoctamin 1 and 2 promote murine uterine smooth muscle contractility
American Journal of Obstetrics and Gynecology, 2014Co-Authors: Kyra Bernstein, Jennifer Danielsson, Joy Vink, Ronald J Wapner, Hiromi Wakita, George GallosAbstract:Objective To determine the presence of calcium activated Chloride Channels anoctamin 1 (ANO1) and 2 (ANO2) in human and murine uterine smooth muscle (MUSM) and evaluate the physiologic role for these ion Channels in murine myometrial contractility. Study Design We performed reverse transcription polymerase chain reaction to determine whether ANO1 and 2 are expressed in human and murine uterine tissue to validate the study of this protein in mouse models. Immunohistochemical staining of ANO1 and 2 was then performed to determine protein expression in murine myometrial tissue. The function of ANO1 and 2 in murine uterine tissue was evaluated using electrophysiologic studies, organ bath, and calcium flux experiments. Results ANO1 and 2 are expressed in human and MUSM cells. Functional studies show that selective antagonism of these Channels promotes relaxation of spontaneous MUSM contractions. Blockade of ANO1 and 2 inhibits both agonist-induced and spontaneous transient inward currents and abolishes G-protein coupled receptor (oxytocin) mediated elevations in intracellular calcium. Conclusion The calcium activated Chloride Channels ANO1 and 2 are present in human and murine myometrial tissue and may provide novel potential therapeutic targets to achieve effective tocolysis.
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Calcium-activated Chloride Channels anoctamin 1 and 2 promote murine uterine smooth muscle contractility.
American journal of obstetrics and gynecology, 2014Co-Authors: Kyra Bernstein, Jennifer Danielsson, Ronald J Wapner, Hiromi Wakita, Joy Y Vink, George GallosAbstract:To determine the presence of calcium activated Chloride Channels anoctamin 1 (ANO1) and 2 (ANO2) in human and murine uterine smooth muscle (MUSM) and evaluate the physiologic role for these ion Channels in murine myometrial contractility. We performed reverse transcription polymerase chain reaction to determine whether ANO1 and 2 are expressed in human and murine uterine tissue to validate the study of this protein in mouse models. Immunohistochemical staining of ANO1 and 2 was then performed to determine protein expression in murine myometrial tissue. The function of ANO1 and 2 in murine uterine tissue was evaluated using electrophysiologic studies, organ bath, and calcium flux experiments. ANO1 and 2 are expressed in human and MUSM cells. Functional studies show that selective antagonism of these Channels promotes relaxation of spontaneous MUSM contractions. Blockade of ANO1 and 2 inhibits both agonist-induced and spontaneous transient inward currents and abolishes G-protein coupled receptor (oxytocin) mediated elevations in intracellular calcium. The calcium activated Chloride Channels ANO1 and 2 are present in human and murine myometrial tissue and may provide novel potential therapeutic targets to achieve effective tocolysis. Copyright © 2014 Elsevier Inc. All rights reserved.
Christopher Miller - One of the best experts on this subject based on the ideXlab platform.
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ClC Chloride Channels viewed through a transporter lens
Nature, 2006Co-Authors: Christopher MillerAbstract:Since its discovery, the ClC family of Chloride Channels has presented biophysicists with unexpected behaviours and unusual surprises. The latest of these is the realization that not only does the family feature genuine Chloride Channels, it also includes proton-coupled Chloride transporters, which move Chloride ions and protons across the membrane in opposite directions. The crystal structure of such a transporter serves as a useful platform for understanding ClC Channels, and features of Chloride/proton exchange-transport may provide a key for comprehending voltage-dependent gating of the Channels.
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A biological role for prokaryotic ClC Chloride Channels
Nature, 2002Co-Authors: Ramkumar Iyer, Tina M. Iverson, Alessio Accardi, Christopher MillerAbstract:An unexpected finding emerging from large-scale genome analyses is that prokaryotes express ion Channels belonging to molecular families long studied in neurons. Bacteria and archaea are now known to carry genes for potassium Channels of the voltage-gated, inward rectifier and calcium-activated classes, ClC-type Chloride Channels, an ionotropic glutamate receptor and a sodium channel. For two potassium Channels and a Chloride channel, these homologues have provided a means to direct structure determination. And yet the purposes of these ion Channels in bacteria are unknown. Strong conservation of functionally important sequences from bacteria to vertebrates, and of structure itself, suggests that prokaryotes use ion Channels in roles more adaptive than providing high-quality protein to structural biologists. Here we show that Escherichia coli uses Chloride Channels of the widespread ClC family in the extreme acid resistance response. We propose that the Channels function as an electrical shunt for an outwardly directed virtual proton pump that is linked to amino acid decarboxylation.
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a decade of clc Chloride Channels structure mechanism and many unsettled questions
Annual Review of Biophysics and Biomolecular Structure, 2000Co-Authors: Merritt Maduke, Christopher Miller, Joseph A MindellAbstract:ClC-type Chloride Channels are ubiquitous throughout the biological world. Expressed in nearly every cell type, these proteins have a host of biological functions. With nine distinct homologues known in eukaryotes, the ClCs represent the only molecularly defined family of Chloride Channels. ClC Channels exhibit features of molecular architecture and gating mechanisms unprecedented in other types of ion Channels. They form two-pore homodimers, and their voltage-dependence arises not from charged residues in the protein, but rather via coupling of gating to the movement of Chloride ions within the pore. Because the functional characteristics of only a few ClC Channels have been studied in detail, we are still learning which properties are general to the whole family. New approaches, including structural analyses, will be crucial to an understanding of ClC architecture and function.