Association of ClC-3 Channel with Cl − Transport by Human Nonpigmented Ciliary Epithelial Cells

Coca‐Prados, Miguel; Sánchez-Torres, Juan; Peterson-Yantorno, K.; Civan, Mortimer M.

doi:10.1007/s002329900044

Cited by 70 publications

(50 citation statements)

References 26 publications

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“…It was suggested that pICln, identified as a soluble cytosolic protein which forms specific complexes with actin and other cytosolic proteins, might be involved as a sensor or mediator in the change of cell volume, rearrangement of cytoskeletal components, and activation of chloride channels (Krapivinsky et al 1994(Krapivinsky et al , 1998. A model introduced by Coca-Prados et al (1996) integrates the function of ClC_3 and pICln. Their hypothesis was that ClC_3 provides a channel for chloride movement directly regulated by PKC, and pICln is a volume-sensitive regulator which controls the movement of chloride through the ClC_3 channel by a mechanism yet to be identified.…”

Section: Discussionmentioning

confidence: 99%

Functional and molecular characterization of a volume‐sensitive chloride current in rat brain endothelial cells

Weikersthal

Barrand

Hladky

1999

The Journal of Physiology

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Endothelial cells from brain microvessels form the structural and functional component of the blood-brain barrier (BBB) which isolates the brain parenchyma from normal variations in body fluid composition. Their properties are very different from those found in other parts of the vasculature. In particular they possess highly resistant, tight intercellular junctions, have minimal pinocytotic transport and there are no fenestrations. These characteristics ensure a stable environment in the brain protected from peripheral fluctuations and allowing normal neuronal activity. Various conditions such as ischaemia, hypoxia, brain injury and inflammation are accompanied by brain oedema which can be caused or aggravated by the swelling of endothelial cells which then can result in increased permeability and disruption of the BBB. The ability of endothelial cells to regulate volume efficiently is therefore a prerequisite for the preservation of the structural integrity of the BBB. Studying the ionic mechanisms underlying endothelial cell volume regulation is important in understanding the processes and regulation of fluid movement across the BBB. Under normal steady state conditions, the constancy of the cell volume is maintained by the Na¤-K¤-ATPase. In addition, most cells possess transport systems that become activated after changes in cell volume. These include the Na¤-H¤ exchangers, the Na¤-K¤-Cl¦ cotransporter, chloride 1. Volume-activated chloride currents in cultured rat brain endothelial cells were investigated on a functional level using the whole-cell voltage-clamp technique and on a molecular level using the reverse transcriptase-polymerase chain reaction (RT-PCR). 2. Exposure to a hypotonic solution caused the activation of a large, outward rectifying current, which exhibited a slight time-dependent decrease at strong depolarizing potentials. The anion permeability of the induced current was I¦ (1·7) > Br¦ (1·2) > Cl¦ (1·0) > F¦ (0·7) > gluconate (0·18). 3. The chloride channel blocker 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB, 100 ìÒ) rapidly and reversibly inhibited both inward and outward currents. The chloride transport blocker 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS, 100 ìÒ) also blocked the hypotonicity-induced current in a reversible manner. In this case, the outward current was more effectively suppressed than the inward current. The volume-activated current was also inhibited by the antioestrogen tamoxifen (10 ìÒ). 4. The current was dependent on intracellular ATP and independent of intracellular Ca¥. 5. Activation of protein kinase C by phorbol 12,13-dibutyrate (PDBu, 100 nÒ) inhibited the increase in current normally observed following hypotonic challenge. 6. Extracellular ATP (10 mÒ) inhibited the current with a more pronounced effect on the outward than the inward current. 7. Verapamil (100 ìÒ) decreased both the inward and the outward hypotonicity-activated chloride current. 8. RT-PCR analysis was used to determine possible molecular candidates for the volumesensitive curr...

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Section: Discussionmentioning

confidence: 99%

Functional and molecular characterization of a volume‐sensitive chloride current in rat brain endothelial cells

Weikersthal

Barrand

Hladky

1999

The Journal of Physiology

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“…It has been proposed that PICln, first cloned by Paulmichl, Li, Wickman, Ackerman, Peralata & Clapham (1992), is VSOAC (Strange et al 1996). In contrast, it has recently been suggested that ClC-3, first cloned from rat kidney by Kawasaki et al (1994), is the volume-activated Cl-channel in a human non-pigmented ciliary epithelial cell line (ODM-2 cells) (Coca-Prados, Sanchez-Torres, PetersonYantorno & Civan, 1996) and that this channel is regulated by PICln (Coca-Prados et al 1996). Further to this, but not necessarily in contradiction to it, Wu et al (1996) demonstrated that this volume-activated current was regulated by P-glycoprotein.…”

Section: Discussionmentioning

confidence: 99%

Three different Cl‐ channels in the bovine ciliary epithelium activated by hypotonic stress.

Zhang

Jacob

1997

The Journal of Physiology

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1. Hypotonic solution induced transient Cl-channel activity in both pigmented and nonpigmented ciliary epithelial cells in cell-attached patches. 2. The activation time constants for these currents were 63 and 97 s for non-pigmented and pigmented ciliary epithelial (NPCE and PCE) cells, respectively. The currents inactivated during the exposure to hypotonic solution with time constants of 59 and 304 s for NPCE and PCE cells, respectively. 3. Single channel analysis revealed the presence of a low-conductance Cl-channel in both the NPCE (7 3 + 0 4 pS) and PCE (8-6 + 0 9 pS) cells. In addition, an intermediate-conductance (18-8 pS) channel was found alone in the NPCE cells and a maxi Cl-channel (105 pS) was found in the PCE cells. The similarities between the 18-8 pS Cl-channel and the volumeactivated organic osmolyte-anion channel (VSOAC) are discussed. 4. The hypotonic activation of all three Cl-channels was prevented by the inclusion of 100 ,UM 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) in the patch pipette. 5. Inclusion of tamoxifen in the patch pipette inhibited only the intermediate-conductance channel in the NPCE cells. This is consistent with the identification of the intermediate 18 pS Cl-channel, found only in NPCE cells, as VSOAC. 6. Negative pressure also evoked single Cl-channel activity but the activation kinetics were quite different, suggesting that, even if the channels are the same, the second messenger pathways involved are different. 7. The activation/inactivation kinetics of these Cl-channels correlate well with the time course of regulatory volume decrease (RVD) in these cells, suggesting that these channels may well participate in the process of RVD. 8. The asymmetrical distribution of Cl-channels in the ciliary epithelium may be significant for aqueous humour secretion. For instance, the presence of the VSOAC-like channel in the NPCE cells may allow one-way traffic of anions and organic osmolytes into the eye and, if these solutes were loaded by the PCE cells, then a vectorial flow from the blood into the eye would occur.

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“…A standard protocol was then used to evaluate the hypothesis that swelling might increase secretion by directly affecting distal steps in insulin granule exocytosis. Finally, as a first step toward ultimately establishing the molecular identity of I Cl,islet , reverse transcriptase (RT)-polymerase chain reaction (PCR) was used to determine whether mRNA for CLC-3 was present in HIT cells, because this Cl Ϫ channel isoform is a strong candidate for the outwardly rectifying swelling-activated Cl Ϫ channel of other tissues (21)(22)(23)(24)(25)(26).…”

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confidence: 99%

Chloride Channels Regulate HIT Cell Volume but Cannot Fully Account for Swelling-Induced Insulin Secretion

Kinard¹,

Goforth²,

Qing³

et al. 2001

Diabetes

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Insulin-secreting pancreatic islet ␤-cells possess anionpermeable Cl؊ channels (I Cl,islet ) that are swelling-activated, but the role of these channels in the cells is unclear. The Cl ؊ channel blockers 4,4-diisothiocyanostilbene-2,2-disulfonic acid (DIDS) and niflumic acid were evaluated for their ability to inhibit I Cl,islet in clonal ␤-cells (HIT cells). Both drugs blocked the channel, but the blockade due to niflumic acid was less voltage-dependent than the blockade due to DIDS. HIT cell volume initially increased in hypotonic solution and was followed by a regulatory volume decrease (RVD). The addition of niflumic acid and, to a lesser extent, DIDS to the hypotonic solution potentiated swelling and blocked the RVD. In isotonic solution, niflumic acid produced swelling, suggesting that islet Cl ؊ channels are activated under basal conditions. The channel blockers glyburide, gadolinium, or tetraethylammonium-Cl did not alter hypotonic-induced swelling or volume regulation. The Na/K/2Cl transport blocker furosemide produced cell shrinkage in isotonic solution and blocked cell swelling normally induced by hypotonic solution. Perifused HIT cells secreted insulin when challenged with hypotonic solutions. However, this could not be completely attributed to I Cl,islet -mediated depolarization, because secretion persisted even when Cl ؊ channels were fully blocked. To test whether blocker-resistant secretion occurred via a distal pathway, distal secretion was isolated using 50 mmol/l potassium and diazoxide. Under these conditions, glucose-dependent secretion was blunted, but hypotonically induced secretion persisted, even with Cl ؊ channel blockers present. These results suggest that ␤-cell swelling stimulates insulin secretion primarily via a distal I Cl,isletindependent mechanism, as has been proposed for K ATPindependent glucose-and sulfonylurea-stimulated insulin secretion. Reverse transcriptase-polymerase chain reaction of HIT cell mRNA identified a CLC-3 transcript in HIT cells. In other systems, CLC-3 is believed to mediate swelling-induced outwardly rectify-

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Association of ClC-3 Channel with Cl − Transport by Human Nonpigmented Ciliary Epithelial Cells

Cited by 70 publications

References 26 publications

Functional and molecular characterization of a volume‐sensitive chloride current in rat brain endothelial cells

Functional and molecular characterization of a volume‐sensitive chloride current in rat brain endothelial cells

Three different Cl‐ channels in the bovine ciliary epithelium activated by hypotonic stress.

Chloride Channels Regulate HIT Cell Volume but Cannot Fully Account for Swelling-Induced Insulin Secretion

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