A Decade of CLC Chloride Channels: Structure, Mechanism, and Many Unsettled Questions

Maduke, Merritt; Miller, Christopher; Mindell, Joseph A.

doi:10.1146/annurev.biophys.29.1.411

Cited by 169 publications

(163 citation statements)

References 95 publications

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“…CLC channels are voltage dependent (Jentsch et al, 2002;Maduke et al, 2000) like I Cl(Ca) but do not exhibit Ca 2+ dependence. CLC channels are also commonly blocked by molar concentrations of extracellular Zn 2+ (Jentsch et al, 2002), something we do not observe for I Cl(Ca).…”

Section: Discussionmentioning

confidence: 99%

Dopamine modulation of Ca2+ dependent Cl- current regulates ciliary beat frequency controlling locomotion inTritonia diomedea

Woodward

Willows

2006

Journal of Experimental Biology

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SUMMARY The physiological mechanisms controlling ciliary beating remain largely unknown. Evidence exists supporting both hormonal control of ciliary beating and control via direct innervation. In the present study we investigated nervous control of cilia based locomotion in the nudibranch mollusc, Tritonia diomedea. Ciliated pedal epithelial (CPE) cells acting as locomotory effectors may be electrically excitable. To explore this possibility we characterized the cells' electrical properties, and found that CPE cells have large voltage dependent whole cell currents with two components. First, there is a fast activating outward Cl- current that is both voltage and Ca2+ influx dependent(ICl(Ca)). ICl(Ca) is sensitive to DIDS and 9-AC, and resembles currents of Ca2+-activated Cl- channels (CaCC). Ca2+ dependence also suggests the presence of voltage-gated Ca2+ channels; however, we were unable to detect these currents. The second current, a voltage dependent proton current(IH), activates very slowly and is sensitive to both Zn2+ and changes in pH. In addition we identify a new cilio-excitatory substance in Tritonia, viz., dopamine. Dopamine, in the 10 μmol l-1-1 mmol l-1 range, significantly increases ciliary beat frequency (CBF). We also found dopamine and Tritonia Pedal Peptide(TPep-NLS) selectively suppress ICl(Ca) in CPE cells,demonstrating a link between CBF excitation and ICl(Ca). It appears that dopamine and TPep-NLS inhibit ICl(Ca) not through changing [Ca2+]in, but directly by an unknown mechanism. Coupling of ICl(Ca) and CBF is further supported by our finding that DIDS and zero [Cl-]outboth increase CBF, mimicking dopamine and TPep-NLS excitation. These results suggest that dopamine and TPep-NLS act to inhibit ICl(Ca),initiating and prolonging Ca2+ influx, and activating CBF excitation.

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Section: Discussionmentioning

confidence: 99%

Dopamine modulation of Ca2+ dependent Cl- current regulates ciliary beat frequency controlling locomotion inTritonia diomedea

Woodward

Willows

2006

Journal of Experimental Biology

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“…The ability of discrete cytoplasmic domains to affect the gatings of a broad spectrum of ion channels is emerging as an important general theme in ion-channel regulation (4,(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). In most cases, little is known about the mechanism and sites of interaction of these domains with the gating mechanism of the channel itself.…”

Section: Discussionmentioning

confidence: 99%

“…Further characterization of these ''unique'' properties are important not just for the sake of understanding TOK1 function, but for possible general relevance. Both filter-specific gating (5)(6)(7)(8) and cytoplasmic domain influence of channel gating (9)(10)(11)(12)(13)(14)(15)(16)(17)(18) are emerging as common themes amongst K ϩ channels. Here, we report on a more specific analysis of the ability of the carboxyl tail to influence TOK1 gating.…”

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confidence: 99%

The carboxyl tail forms a discrete functional domain that blocks closure of the yeast K ⁺ channel

Loukin

Lin

Athar

et al. 2002

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

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Non-targeted mutagenesis studies of the yeast K ؉ channel, TOK1, have led to identification of functional domains common to other cation channels as well as those so far not found in other channels. Among the latter is the ability of the carboxyl tail to prevent channel closure. Here, we show that the tail can fulfill this function in trans. Coexpression of the carboxyl tail with the tail-deleted channel core restores normal channel behavior . A Ser͞Thr-rich region at its amino end and an acidic stretch at its carboxyl end delineate the minimal region required for tail function. This region of 160 aa apparently forms a discrete functional domain. Interaction of this domain with the channel core is strong, being recalcitrant to removal from excised membrane patches by both high salt and reducing agents. Although the use of a cytoplasmic domain to regulate channel is common among animal channels, by using it as a ''foot-in-the-door'' to maintain open state appears unique to TOK1, the first fungal K ؉ channel studied in depth.Saccharomyces cerevisiae ͉ TOK1 ͉ channel gating T he K ϩ -specific ion channel in the plasma membrane of the budding yeast Saccharomyces cerevisiae (TOK1) is one of the first microbial K ϩ channels to be examined in detail. Genetic analysis, coupled with biophysical analysis, of TOK1 has assisted in the identification of what we call the PP region, the cytoplasmic end of the P-region-following membrane domain, which has been found to be intimately involved with gating of cation channels (1, 2, 3). Our analyses have also pointed to the existence of functional domains that, on first glance, appeared unique to TOK1, including a filter-specific gating (Fig. 1A; ref. 22) and a carboxyl tail stabilization of the inner-pore gate (Fig. 1B; ref. 4). Further characterization of these ''unique'' properties are important not just for the sake of understanding TOK1 function, but for possible general relevance. Both filter-specific gating (5-8) and cytoplasmic domain influence of channel gating (9-18) are emerging as common themes amongst K ϩ channels. Here, we report on a more specific analysis of the ability of the carboxyl tail to influence TOK1 gating.TOK1 is predicted to contain eight transmembrane domains with canonical P-region pore loops following both the fifth and seventh spans (19,20). The biophysics and genetics of this channel have been explored, but its physiological function remains largely unknown except as a target for killer toxin (6, 7). Although commonly referred to as ''voltage-regulated'' (21), TOK1's gating is regulated by the K ϩ electrochemical potential (⌬ K ϩ ) rather than merely voltage alone (19,20). The front line of this ⌬ K ϩ -dependent regulation is a nearinstantaneous gating process that prevents inward current flow, the ''R'' state (1). Because it is the only place where the transmembrane ⌬ K ϩ can be efficiently monitored, the R state is most readily accounted for as an intrinsic gating property of the filter region (22). We proposed a model in which inward ⌬ K ϩ results...

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“…The cells were purchased from ATCC (ATCC, #HTB-79, Manassas, VA) and grown in Iscove's modified Dulbecco's medium (Invitrogen, Carlsbad, CA) with 4 mM L-glutamine, 1.5 g/L sodium bicarbonate, and 20% FBS. Cells were incubated at 37°C with 5% CO 2 .…”

Section: Cell Culturementioning

confidence: 99%

“…2 They were named chloride channels mainly because chloride ions were the most abundant anion in biological systems.…”

mentioning

confidence: 99%

Development of a Colorimetric Method for Functional Chloride Channel Assay

Tang

Wildey²

2004

SLAS Discovery

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Anion channels play significant physiological roles in humans and animals. However, the effort of screening for anion channel modulators was limited by the available assay technologies. This report discusses the development of a cell-based functional chloride channel assay using iodine as the chloride channel functional indicator. Iodine concentrations were measured with modified Sandell-Kolthoff reaction using colorimetric detection. The assay was rapid and quantitative. When WSS-1 cells were activated by γ-aminobutyric acid (GABA) in the condition that γ-aminobutyric acid type A receptor (GABA A receptor) conducted outwardly rectifying chloride channel function, the EC 50 of GABA was 7.69 µM. IC 50 s were 0.53 µM for bicuculline and 3.1 µM for picrotoxin, respectively, in the presence of 10 µM GABA. When Capan-1 cells were activated by forskolin, the EC 50 was 0.14 µM. The assay can also be applied to inwardly rectifying anion channels as exemplified by GABA A channel with an EC 50 of 294 µM. Thus, the assay is universal and reliable and can be used for anion channel highthroughput screening. (Journal of Biomolecular Screening 2004:607-613)

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A Decade of CLC Chloride Channels: Structure, Mechanism, and Many Unsettled Questions

Cited by 169 publications

References 95 publications

Dopamine modulation of Ca2+ dependent Cl- current regulates ciliary beat frequency controlling locomotion inTritonia diomedea

Dopamine modulation of Ca2+ dependent Cl- current regulates ciliary beat frequency controlling locomotion inTritonia diomedea

The carboxyl tail forms a discrete functional domain that blocks closure of the yeast K ⁺ channel

Development of a Colorimetric Method for Functional Chloride Channel Assay

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A Decade of CLC Chloride Channels: Structure, Mechanism, and Many Unsettled Questions

Cited by 169 publications

References 95 publications

Dopamine modulation of Ca2+ dependent Cl- current regulates ciliary beat frequency controlling locomotion inTritonia diomedea

Dopamine modulation of Ca2+ dependent Cl- current regulates ciliary beat frequency controlling locomotion inTritonia diomedea

The carboxyl tail forms a discrete functional domain that blocks closure of the yeast K + channel

Development of a Colorimetric Method for Functional Chloride Channel Assay

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The carboxyl tail forms a discrete functional domain that blocks closure of the yeast K ⁺ channel