Characterization of a novel voltage-dependent outwardly rectifying anion current in Caenorhabditis elegans oocytes

2007 ◽  
Vol 292 (1) ◽  
pp. C269-C277 ◽  
Author(s):  
Xiaoyan Yin ◽  
Jerod Denton ◽  
Xiaohui Yan ◽  
Kevin Strange
Keyword(s):  
Cell Cycle ◽  
Caenorhabditis Elegans ◽  
Cell Cycle Control ◽  
Anion Channel ◽  
Disulfonic Acid ◽  
Biophysical Properties ◽  
Open Probability ◽  
Voltage Dependent ◽  
Current Activation ◽  
Oocyte Meiotic Maturation

An inwardly rectifying swelling- and meiotic cell cycle-regulated anion current carried by the ClC channel splice variant CLH-3b dominates the whole cell conductance of the Caenorhabditis elegans oocyte. Oocytes also express a novel outwardly rectifying anion current termed ICl,OR. We recently identified a worm strain carrying a null allele of the clh-3 gene and utilized oocytes from these animals to characterize ICl,OR biophysical properties. The ICl,OR channel is strongly voltage dependent. Outward rectification is due to voltage-dependent current activation at depolarized voltages and rapid inactivation at voltages more hyperpolarized than approximately +20 mV. Apparent channel open probability is zero at voltages less than +20 mV. The channel has a 4:1 selectivity for Cl− over Na+ and an anion selectivity sequence of SCN− > I− > Br− > Cl− > F−. ICl,OR is relatively insensitive to most conventional anion channel inhibitors including DIDS, 4,4′-dinitrostilbene-2,2′-disulfonic acid, 9-anthracenecarboxylic acid, and 5-nitro-2-(3-phenylpropylamino)benzoic acid. However, the current is rapidly inhibited by niflumic acid, metal cations including Gd3+, Cd2+, and Zn2+, and bath acidification. The combined biophysical properties of ICl,OR are distinct from those of other anion currents that have been described. During oocyte meiotic maturation, ICl,OR activity is rapidly downregulated, suggesting that the channel may play a role in oocyte Cl− homeostasis, development, cell cycle control, and/or ovulation.

Disulfonic stilbene permeation and block of the anion channel from the sarcoplasmic reticulum of rabbit skeletal muscle

2006 ◽  
Vol 290 (6) ◽  
pp. C1666-C1677 ◽  
Author(s):  
Derek R. Laver ◽  
Katherine M. Bradley
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Single Molecule ◽  
Anion Channel ◽  
Disulfonic Acid ◽  
Channel Blockers ◽  
Channel Block ◽  
Open Probability ◽  
Planar Bilayers ◽  
Voltage Dependent ◽  
Disulfonic Stilbene

Block of a sarcoplasmic reticulum anion channel (SCl channel) by disulfonic stilbene derivatives [DIDS, dibenzamidostilbene-2,2′-disulfonic acid (DBDS), and 4,4′-dinitrostilbene-2,2′-disulfonic acid (DNDS)] was investigated in planar bilayers using SO[Formula: see text] as the conducting ion. All molecules caused reversible voltage-dependent channel block when applied to either side of the membrane. DIDS also produced nonreversible channel block from both sides within 1–3 min. Reversible inhibition was associated with a decrease in channel open probability and mean open duration but not with any change in channel conductance. The half inhibitory concentration for cis- and trans-inhibition had voltage dependencies with minima of 190 nM and 33 μM for DBDS and 3.4 and 55 μM for DNDS. Our data supports a permeant blocker mechanism, in which stilbenes block SCl channels by lodging in the permeation pathway, where they may dissociate to either side of the membrane and thus permeate the channel. The stilbenes acted as open channel blockers where the binding of a single molecule occludes the channel. DBDS and DNDS, from opposite sides of the membrane, competed for common sites on the channel. Dissociation rates exhibited biphasic voltage dependence, indicative of two dissociation processes associated with ion movement in opposite directions within the trans-membrane electric field. The kinetics of DNDS and DBDS inhibition predict that there are two stilbene sites in the channel that are separated by 14–24 Å and that the pore constriction is ∼10 Å in diameter.

Extracellular acidification elicits a chloride current that shares characteristics with ICl(swell)

2004 ◽  
Vol 287 (5) ◽  
pp. C1426-C1435 ◽  
Author(s):  
Muriel Nobles ◽  
Christopher F. Higgins ◽  
Alessandro Sardini
Keyword(s):  
Carboxylic Acid ◽  
Ion Selectivity ◽  
Cell Types ◽  
Cell Swelling ◽  
Disulfonic Acid ◽  
Biophysical Properties ◽  
Extracellular Acidification ◽  
Dependent Inactivation ◽  
Voltage Dependent ◽  
Rate Of Activation

A Cl− current activated by extracellular acidification, ICl(pHac), has been characterized in various mammalian cell types. Many of the properties of ICl(pHac) are similar to those of the cell swelling-activated Cl− current ICl(swell): ion selectivity (I− > Br− > Cl− > F−), pharmacology [ ICl(pHac) is inhibited by 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS), 1,9-dideoxyforskolin (DDFSK), diphenylamine-2-carboxylic acid (DPC), and niflumic acid], lack of dependence on intra- or extracellular Ca2+, and presence in all cell types tested. ICl(pHac) differs from ICl(swell) in three aspects: 1) its rate of activation and inactivation is very much more rapid, currents reaching a maximum in seconds rather than minutes; 2) it exhibits a slow voltage-dependent activation in contrast to the fast voltage-dependent activation and time- and voltage-dependent inactivation observed for ICl(swell); and 3) it shows a more pronounced outward rectification. Despite these differences, study of the transition between the two currents strongly suggests that ICl(swell) and ICl(pHac) are related and that extracellular acidification reflects a novel stimulus for activating ICl(swell) that, additionally, alters the biophysical properties of the channel.

Calcium-dependent chloride channels in endosomes from rabbit kidney cortex

1994 ◽  
Vol 266 (3) ◽  
pp. C741-C750 ◽  
Author(s):  
W. B. Reeves ◽  
R. W. Gurich
Keyword(s):  
Lipid Bilayers ◽  
Membrane Trafficking ◽  
Single Channel ◽  
Cell Volume Regulation ◽  
Rabbit Kidney ◽  
Disulfonic Acid ◽  
Kidney Cortex ◽  
Open Probability ◽  
Endosomal Acidification ◽  
Voltage Dependent

Ion channels in endosomal membranes from rabbit kidney cortex were studied after reconstitution into planar lipid bilayers. The most frequently observed ion channel was anion selective (PCl/PK = 13) and had a single-channel conductance of 116 pS when the cis and trans solutions contained 410 and 150 mM KCl, respectively, and a conductance of 90 pS in symmetrical 150 mM KCl solutions. The anion selectivity sequence of the channel was NO3- > F- > Br- > Cl- >> I-. The activity of the channel was voltage dependent such that hyperpolarization of the cis, or cytoplasmic, surface of the channel increased the open probability (Po). The activity of the channel was also highly dependent on the calcium activity of the cis but not the trans solution. Channels were fully active (Po > 0.7) at Ca2+ concentration > 1 microM, but channel activity was completely absent (Po < 0.001) at Ca2+ concentration < 250 nM. The effects of calcium on Po were not voltage dependent. The Cl(-)-channel blocker 2-[(2-cyclopentyl-6,7-dichloro-2,3-dihydro-2-methyl-1-oxo-1H-inden -5- yl)oxy]-acetic acid (IAA-94/95) produced a concentration-dependent reversible flickering block of the endosomal channel with a Ki of 15 microM. 4,4'-Dinitrostilbene-2,2'-disulfonic acid, a disulfonic stilbene, also produced a flickering block of the channel with a Ki of approximately 5 microM. Because endosomal Cl- channels are believed to facilitate endosomal acidification, we tested the effects of IAA-94/95 and deletion of Ca2+ on the rate of acidification of intact endosomes. Because neither maneuver affected acidification, we conclude that the 116-pS channel does not participate in endosomal acidification. This channel may be involved in other endosomal processes, e.g., cell volume regulation and control of membrane trafficking.

Cell cycle control by daf-21/Hsp90 at the first meiotic prophase/metaphase boundary during oogenesis in Caenorhabditis elegans

2006 ◽  
Vol 48 (1) ◽  
pp. 25-32 ◽  
Author(s):  
Tadao Inoue ◽  
Kazumasa Hirata ◽  
Yuichiro Kuwana ◽  
Masahiro Fujita ◽  
Johji Miwa ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Caenorhabditis Elegans ◽  
Meiotic Prophase ◽  
Cell Cycle Control

scholarly journals Cell-cycle control in Caenorhabditis elegans: how the worm moves from G1 to S

Oncogene ◽  
2005 ◽  
Vol 24 (17) ◽  
pp. 2756-2764 ◽  
Author(s):  
John Koreth ◽  
Sander van den Heuvel
Keyword(s):  
Cell Cycle ◽  
Caenorhabditis Elegans ◽  
Cell Cycle Control

scholarly journals A synthetic prostone activates apical chloride channels in A6 epithelial cells

2008 ◽  
Vol 295 (2) ◽  
pp. G234-G251 ◽  
Author(s):  
Hui Fang Bao ◽  
Lian Liu ◽  
Julie Self ◽  
Billie Jeanne Duke ◽  
Ryuji Ueno ◽  
...  
Keyword(s):  
Chloride Channels ◽  
Driving Forces ◽  
Anion Channel ◽  
Hek293 Cells ◽  
Open Probability ◽  
Anion Secretion ◽  
A6 Cells ◽  
Low Concentrations ◽  
Voltage Dependent ◽  
Channel Type

The bicyclic fatty acid lubiprostone (formerly known as SPI-0211) activates two types of anion channels in A6 cells. Both channel types are rarely, if ever, observed in untreated cells. The first channel type was activated at low concentrations of lubiprostone (<100 nM) in >80% of cell-attached patches and had a unit conductance of ∼3–4 pS. The second channel type required higher concentrations (>100 nM) of lubiprostone to activate, was observed in ∼30% of patches, and had a unit conductance of 8–9 pS. The properties of the first type of channel were consistent with ClC-2 and the second with CFTR. ClC-2's unit current strongly inwardly rectified that could be best fit by models of the channel with multiple energy barrier and multiple anion binding sites in the conductance pore. The open probability and mean open time of ClC-2 was voltage dependent, decreasing dramatically as the patches were depolarized. The order of anion selectivity for ClC-2 was Cl > Br > NO3 > I > SCN, where SCN is thiocyanate. ClC-2 was a “double-barreled” channel favoring even numbers of levels over odd numbers as if the channel protein had two conductance pathways that opened independently of one another. The channel could be, at least, partially blocked by glibenclamide. The properties of the channel in A6 cells were indistinguishable from ClC-2 channels stably transfected in HEK293 cells. CFTR in the patches had a selectivity of Cl > Br ≫ NO3 ≅ SCN ≅ I. It outwardly rectified as expected for a single-site anion channel. Because of its properties, ClC-2 is uniquely suitable to promote anion secretion with little anion reabsorption. CFTR, on the other hand, could promote either reabsorption or secretion depending on the anion driving forces.

scholarly journals Fate Specification and Tissue-specific Cell Cycle Control of the Caenorhabditis elegans Intestine

2010 ◽  
Vol 21 (5) ◽  
pp. 725-738 ◽  
Author(s):  
Alexandra Segref ◽  
Juan Cabello ◽  
Caroline Clucas ◽  
Ralf Schnabel ◽  
Iain L. Johnstone
Keyword(s):  
Cell Cycle ◽  
Caenorhabditis Elegans ◽  
Cell Fate ◽  
Mammalian Cells ◽  
Cell Cycle Control ◽  
Cell Number ◽  
Embryonic Cell ◽  
Cell Cycle Checkpoint ◽  
Specific Cell ◽  
Fate Specification

Coordination between cell fate specification and cell cycle control in multicellular organisms is essential to regulate cell numbers in tissues and organs during development, and its failure may lead to oncogenesis. In mammalian cells, as part of a general cell cycle checkpoint mechanism, the F-box protein β-transducin repeat-containing protein (β-TrCP) and the Skp1/Cul1/F-box complex control the periodic cell cycle fluctuations in abundance of the CDC25A and B phosphatases. Here, we find that the Caenorhabditis elegans β-TrCP orthologue LIN-23 regulates a progressive decline of CDC-25.1 abundance over several embryonic cell cycles and specifies cell number of one tissue, the embryonic intestine. The negative regulation of CDC-25.1 abundance by LIN-23 may be developmentally controlled because CDC-25.1 accumulates over time within the developing germline, where LIN-23 is also present. Concurrent with the destabilization of CDC-25.1, LIN-23 displays a spatially dynamic behavior in the embryo, periodically entering a nuclear compartment where CDC-25.1 is abundant.

scholarly journals Oligomerization of the Mitochondrial Protein Voltage-Dependent Anion Channel Is Coupled to the Induction of Apoptosis

2010 ◽  
Vol 30 (24) ◽  
pp. 5698-5709 ◽  
Author(s):  
Nurit Keinan ◽  
Dalia Tyomkin ◽  
Varda Shoshan-Barmatz
Keyword(s):  
Mitochondrial Protein ◽  
Resonance Energy ◽  
Anion Channel ◽  
General Mechanism ◽  
Disulfonic Acid ◽  
Molecular Architecture ◽  
Voltage Dependent Anion Channel ◽  
Necrosis Factor Alpha ◽  
Voltage Dependent ◽  
Induction Of Apoptosis

ABSTRACT Accumulating evidence implicates that the voltage-dependent anion channel (VDAC) functions in mitochondrion-mediated apoptosis and as a critical player in the release of apoptogenic proteins, such as cytochrome c, triggering caspase activation and apoptosis. The mechanisms regulating cytochrome c release and the molecular architecture of the cytochrome c-conducting channel remain unknown. Here the relationship between VDAC oligomerization and the induction of apoptosis was examined. We demonstrated that apoptosis induction by various stimuli was accompanied by highly increased VDAC oligomerization, as revealed by cross-linking and directly monitored in living cells using bioluminescence resonance energy transfer technology. VDAC oligomerization was induced in all cell types and with all apoptosis inducers used, including staurosporine, curcumin, As2O3, etoposide, cisplatin, selenite, tumor necrosis factor alpha (TNF-α), H2O2, and UV irradiation, all acting through different mechanisms yet all involving mitochondria. Moreover, correlation between the levels of VDAC oligomerization and apoptosis was observed. Furthermore, the apoptosis inhibitor 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS) inhibited VDAC oligomerization. Finally, a caspase inhibitor had no effect on VDAC oligomerization and cytochrome c release. We propose that VDAC oligomerization is involved in mitochondrion-mediated apoptosis and may represent a general mechanism common to numerous apoptogens acting via different initiating cascades. Thus, targeting the oligomeric status of VDAC, and hence apoptosis, offers a therapeutic strategy for combating cancers and neurodegenerative diseases.

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