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 Prolactin stimulates sodium and chloride ion channels in A6 renal epithelial cells

2015 ◽  
Vol 308 (7) ◽  
pp. F697-F705 ◽  
Author(s):  
Megan M. Greenlee ◽  
Jeremiah D. Mitzelfelt ◽  
Billie Jeanne Duke ◽  
Otor Al-Khalili ◽  
Hui-Fang Bao ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Chloride Transport ◽  
Anion Channel ◽  
Chloride Ion ◽  
Peptide Hormone ◽  
Open Probability ◽  
Renal Epithelial Cells ◽  
Electrophysiological Properties ◽  
A6 Cells ◽  
Pka Pathway

Many hormonal pathways contribute to the regulation of renal epithelial sodium channel (ENaC) function, a key process for maintaining blood volume and controlling blood pressure. In the present study, we examined whether the peptide hormone prolactin (PRL) regulates ENaC function in renal epithelial cells (A6). Basolateral application of several different concentrations of PRL dramatically stimulated the transepithelial current in A6 cells, increasing both amiloride-sensitive (ENaC) and amiloride-insensitive currents. Using cell-attached patch clamp, we determined that PRL increased both the number ( N) and open probability ( Po) of ENaC present in the apical membrane. Inhibition of PKA with H-89 abolished the effect of PRL on amiloride-sensitive and insensitive transepithelial currents and eliminated the increase in ENaC NPo with PRL exposure. PRL also increased cAMP in A6 cells, consistent with signaling through the cAMP-dependent PKA pathway. We also identified that PRL induced activity of a 2-pS anion channel with outward rectification, electrophysiological properties consistent with ClC4 or ClC5. RT-PCR only detected ClC4, but not ClC5 transcripts. Here, we show for the first time that PRL activates sodium and chloride transport in renal epithelial cells via ENaC and ClC4.

Mutations in exons 5, 7 and 8 of the human voltage-dependent anion channel type 3 (VDAC3) gene in sperm with low motility

Andrologia ◽  
2011 ◽  
Vol 44 (1) ◽  
pp. 46-52 ◽  
Author(s):  
Asmarinah ◽  
T. Nuraini ◽  
T. Sumarsih ◽  
R. Paramita ◽  
M. I. Saleh ◽  
...  
Keyword(s):  
Anion Channel ◽  
Voltage Dependent Anion Channel ◽  
Voltage Dependent ◽  
Type 3 ◽  
Channel Type

Basolateral outward rectifier chloride channel in isolated crypts of mouse colon

2000 ◽  
Vol 279 (2) ◽  
pp. G277-G287 ◽  
Author(s):  
Olivier Mignen ◽  
Stéphane Egee ◽  
Martine Liberge ◽  
Brian J. Harvey
Keyword(s):  
Protein Kinase ◽  
Chloride Channels ◽  
Single Channel ◽  
Basolateral Membrane ◽  
Distal Colon ◽  
Open Probability ◽  
Voltage Dependent ◽  
Intracellular Ca ◽  
Dependent Protein ◽  
Inside Out

Single channel patch-clamp techniques were used to demonstrate the presence of outwardly rectifying chloride channels in the basolateral membrane of crypt cells from mouse distal colon. These channels were rarely observed in the cell-attached mode and, in the inside-out configuration, only became active after a delay and depolarizing voltage steps. Single channel conductance was 23.4 pS between −100 and −40 mV and increased to 90.2 pS between 40 and 100 mV. The channel permeability sequence for anions was: I− > SCN− > Br−> Cl− > NO3 − > F−≫ SO4 2− ≈ gluconate. In inside-out patches, the channel open probability was voltage dependent but insensitive to intracellular Ca2+ concentration. In cell-attached mode, forskolin, histamine, carbachol, A-23187, and activators of protein kinase C all failed to activate the channel, and activity could not be evoked in inside-out patches by exposure to the purified catalytic subunit of cAMP-dependent protein kinase A. The channel was inhibited by 5-nitro-2-(3-phenylpropylamino)benzoate, 9-anthracenecarboxylic acid, and DIDS. Stimulation of G proteins with guanosine 5′- O-(3-thiotriphosphate) decreased the channel open probability and conductance, whereas subsequent addition of guanosine 5′- O-(2-thiodiphosphate) reactivated the channel.

scholarly journals Immotile Sperm and Infertility in Mice Lacking Mitochondrial Voltage-dependent Anion Channel Type 3

2001 ◽  
Vol 276 (42) ◽  
pp. 39206-39212 ◽  
Author(s):  
Margaret J. Sampson ◽  
William K. Decker ◽  
Arthur L. Beaudet ◽  
Wim Ruitenbeek ◽  
Dawna Armstrong ◽  
...  
Keyword(s):  
Anion Channel ◽  
Voltage Dependent Anion Channel ◽  
Voltage Dependent ◽  
Type 3 ◽  
Channel Type

scholarly journals Chloride Channels in Astrocytes: Structure, Roles in Brain Homeostasis and Implications in Disease

2019 ◽  
Vol 20 (5) ◽  
pp. 1034 ◽  
Author(s):  
Xabier Elorza-Vidal ◽  
Héctor Gaitán-Peñas ◽  
Raúl Estévez
Keyword(s):  
Chloride Channels ◽  
3D Structure ◽  
Physiological Role ◽  
Anion Channel ◽  
Cell Type ◽  
Multiple Functions ◽  
Voltage Dependent ◽  
Key Aspects ◽  
Brain Homeostasis

Astrocytes are the most abundant cell type in the CNS (central nervous system). They exert multiple functions during development and in the adult CNS that are essential for brain homeostasis. Both cation and anion channel activities have been identified in astrocytes and it is believed that they play key roles in astrocyte function. Whereas the proteins and the physiological roles assigned to cation channels are becoming very clear, the study of astrocytic chloride channels is in its early stages. In recent years, we have moved from the identification of chloride channel activities present in astrocyte primary culture to the identification of the proteins involved in these activities, the determination of their 3D structure and attempts to gain insights about their physiological role. Here, we review the recent findings related to the main chloride channels identified in astrocytes: the voltage-dependent ClC-2, the calcium-activated bestrophin, the volume-activated VRAC (volume-regulated anion channel) and the stress-activated Maxi-Cl−. We discuss key aspects of channel biophysics and structure with a focus on their role in glial physiology and human disease.

Differential Mechanisms Underlying the Modulation of Delayed-Rectifier K+ Channel in Mouse Neocortical Neurons by Nitric Oxide

2006 ◽  
Vol 95 (4) ◽  
pp. 2167-2178 ◽  
Author(s):  
Nian-Lin R. Han ◽  
Jian-Shan Ye ◽  
Albert Cheung Hoi Yu ◽  
Fwu-Shan Sheu
Keyword(s):  
Nitric Oxide ◽  
K Channel ◽  
Delayed Rectifier ◽  
Open Probability ◽  
No Donor ◽  
Whole Cell ◽  
Low Concentrations ◽  
Cgmp Signaling ◽  
Voltage Dependent ◽  
High Concentrations

The modulatory effects of nitric oxide (NO) on voltage-dependent K+ channels are intricate. In our present study, the augmentation and reduction of K+ currents by NO donor S-nitro- N-acetylpenicillamine (SNAP) and pure dissolved NO was observed in dissociated neurons from mice neocortex with both whole cell and cell-attached patch clamp. By using a specific electrochemical sensor, the critical concentrations of NO that increased or reduced the channel activities were accurately quantified. Low concentrations of SNAP (20 μM) or NO solution (0.1 μM) enhanced whole cell delayed rectifier K+-current ( IK) and left the fast inactivating A current ( IA) unchanged. However, high concentrations of SNAP (100 μM) and NO (0.5 μM) reduced both IK and IA currents. In cell-attached experiments, a significant increase in channel open probability (NP0) was observed when using low concentrations of SNAP or NO. High concentrations of SNAP or NO dramatically decreased NP0. The increase in channel activities by low concentrations of SNAP was abolished in the presence of either inhibitors of soluble guaylate cyclase or inhibitors of cGMP-dependent protein kinase G, suggesting a link to the NO-cGMP signaling cascade. The reduction of channel activities by high concentrations of SNAP was reversed by the reducing agent dithiothreitol, implying a redox reaction mechanism. Thus both NO-cGMP signaling and a redox mechanism are involved in the modulation of IK channel activity for neuron excitability.

Single voltage-dependent K+ and Cl− channels in cultured rat astrocytes

1987 ◽  
Vol 65 (5) ◽  
pp. 1043-1050 ◽  
Author(s):  
U. Sonnhof
Keyword(s):  
Membrane Potential ◽  
Chloride Channels ◽  
Recovery Period ◽  
Active State ◽  
Current Fluctuations ◽  
Potential Range ◽  
Open Probability ◽  
Voltage Dependent ◽  
Testing Potential ◽  
Rat Astrocytes

The kinetic reactions of a voltage-dependent K+ channel, which constituted about 14% of all the recorded K+ channels in the membrane of cultured rat astrocytes were studied in detail. A scheme of one open and three closed states is necessary to describe the kinetic reactions of this channel. The channel contributes little to the resting membrane potential. Its steady state open probability (Po) is 0.06 at −70 mV. When the cell is depolarized to 0 mV, Po approaches 1. This represents a 17-fold increase. Such channels could contribute to the potassium clearance by enhancing the effect of "spatial buffering." Additionally, single anion-selective channels with very high conductances were found in inside-out patches in approximately 15% of all recorded channels in the membrane of rat astrocytes. Channel openings are characterized by more than one conductance level; the main level showed a mean conductance of 400 pS. These channels are divided into two groups. Approximately 90% of the recorded chloride channels showed a strong voltage dependency of their current fluctuations. Within a relatively small potential range (±15 mV) the channels have a high probability of being in the active state. After a voltage jump to varying testing potentials in the range of ±20 to ±50 mV the channels continued to be in the active state for some time and then closed to a shut state. If the testing potential persisted, the channels were not able to leave this shut state. The active state could only be reached again if the membrane potential was reset close to zero for some time. The time course of the current relaxation was measured by ensemble averaging of single channel current fluctuations. When at the end of a testing potential the voltage was set back to zero, the channel remained in the shut state for some time before it reached the open state again. The voltage dependence of this recovery period was analyzed as well but is not shown in this paper. The reaction indicates a nonstationary process as the open probability is time dependent, and for better differentiation I will call these channels nonstationary chloride channels. A subgroup of 10% of all recorded chloride channels showed no voltage-dependent kinetic reactions. I will denote them as stationary chloride channels. Both types of Cl− channels are mainly permeable to anions but showed a slight permeability to cations. An idea of the role of these channels at this state must be highly speculative. The possibilities include a cell to cell transfer of material or a regulation of the internal or external ion environment. In the latter case, they could provide an uptake mechanism for potassium ions in addition to the spatial buffer currents.

Sign in / Sign up

Export Citation Format

Share Document