501
|
Cannon CL, Basavappa S, Strange K. Intracellular ionic strength regulates the volume sensitivity of a swelling-activated anion channel. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:C416-22. [PMID: 9688595 DOI: 10.1152/ajpcell.1998.275.2.c416] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Cell swelling activates an outwardly rectifying anion channel termed VSOAC (volume-sensitive organic osmolyte/anion channel). Regulation of VSOAC by intracellular electrolytes was characterized in Chinese hamster ovary cells by whole cell patch clamp. Elevation of intracellular CsCl concentration from 40 to 180 mM resulted in a concentration-dependent decrease in channel activation. Activation of VSOAC was insensitive to the salt gradient across the plasma membrane, the intracellular concentration of specific anions or cations, and the total intracellular concentration of cations, anions, or electrolytes. Comparison of cells dialyzed with either CsCl or Na2SO4 solutions demonstrated directly that VSOAC activation is modulated by intracellular ionic strength (microi). The relative cell volume at which VSOAC current activation was triggered, termed the channel volume set point, decreased with decreasing ionic strength. At microi = 0.04, VSOAC activation occurred spontaneously in shrunken cells. The rate of VSOAC activation was nearly 50-fold higher in cells with microi = 0.04 vs. those with microi = 0.18. We propose that microi modulates the volume sensor responsible for channel activation.
Collapse
Affiliation(s)
- C L Cannon
- Laboratory of Cellular and Molecular Physiology, Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
| | | | | |
Collapse
|
502
|
Tao GZ, Komatsuda A, Miura AB, Kobayashi A, Itoh H, Tashima Y. pICln predominantly localizes at luminal surface membranes of distal tubules and Henle's ascending limbs. Biochem Biophys Res Commun 1998; 247:668-73. [PMID: 9647751 DOI: 10.1006/bbrc.1998.8837] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We produced a highly specific antibody to the C-terminal peptide sequence of pICln. It recognized pICln with a 38-kDa molecular mass on SDS-polyacrylamide gel electrophoresis, coinciding with that previously reported. During native polyacrylamide gel electrophoresis, three immunoreactive bands (38, 70, and 130 kDa) were detected. The isoelectric point of pICln was calculated to be 4.0. Subcellular localization study showed the presence of pICln in the soluble and microsomal fraction. pICln can be easily solubilized from the membrane fraction with Triton X-100. From immunohistochemical observations, we found pICln to be obviously located on the luminal surface membranes of the distal tubules and Henle's loop ascending limbs, and it can also be found inside proximal tubular cells. The present results suggested that pICln functions as a "cytosolic anchor = membrane insertion" model, and it plays important roles in the "urine dilution segment" cells of nephrons.
Collapse
Affiliation(s)
- G Z Tao
- Department-2 of Biochemistry, School of Medicine, Akita University, Japan
| | | | | | | | | | | |
Collapse
|
503
|
Rutledge EM, Aschner M, Kimelberg HK. Pharmacological characterization of swelling-induced D-[3H]aspartate release from primary astrocyte cultures. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:C1511-20. [PMID: 9696693 DOI: 10.1152/ajpcell.1998.274.6.c1511] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
During stroke or head trauma, extracellular K+ concentration increases, which can cause astrocytes to swell. In vitro, such swelling causes astrocytes to release excitatory amino acids, which may contribute to excitotoxicity in vivo. Several putative swelling-activated channels have been identified through which such anionic organic cellular osmolytes can be released. In the present study, we sought to identify the swelling-activated channel(s) responsible for D-[3H]aspartate release from primary cultured astrocytes exposed to either KCl or hypotonic medium. KCl-induced D-[3H]aspartate release was inhibited by the anion channel inhibitors 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), dideoxyforskolin, L-644711, ATP, ITP, 3'-azido-3'-deoxythymidine, DIDS, and tamoxifen but not by cAMP. The cell swelling caused by raised KCl was not inhibited by extracellular ATP or tamoxifen as measured by an electrical impedance method, which suggests that these anion channel inhibitors directly blocked the channel responsible for efflux. Extracellular nucleotides and DIDS, however, had no or only partial effects on D-[3H]aspartate release from cells swollen by hypotonic medium, but such release was inhibited by NPPB, dideoxyforskolin, and tamoxifen. Of the swelling-activated channels so far identified, our data suggest that a volume-sensitive outwardly rectifying channel is responsible for D-[3H]aspartate release from primary cultured astrocytes during raised extracellular K+ and possibly during hypotonic medium-induced release.
Collapse
Affiliation(s)
- E M Rutledge
- Department of Pharmacology, Albany Medical College, New York 12208, USA
| | | | | |
Collapse
|
504
|
Emma F, Breton S, Morrison R, Wright S, Strange K. Effect of cell swelling on membrane and cytoplasmic distribution of pICln. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:C1545-51. [PMID: 9696697 DOI: 10.1152/ajpcell.1998.274.6.c1545] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
pICln is found ubiquitously in mammalian cells and is postulated to play a critical role in cell volume regulation. Mutagenesis studies led to the proposal that pICln is a swelling-activated anion channel. However, recent studies in Madin-Darby canine kidney cells and endothelial cells have shown that the protein is localized primarily to the cytoplasm. It has therefore been postulated that activation involves reversible translocation of pICln from the cytoplasm and insertion into the plasma membrane. We tested this hypothesis using several different approaches. Fractionation of C6 glioma cells into plasma membrane- and cytoplasm-containing fractions demonstrated that approximately 90% of the recovered pICln was confined to the cytosol. Swelling had no effect on the relative amount of protein present in the plasma membrane fraction. Immunofluorescence microscopy revealed that pICln is localized primarily, if not exclusively, to the cytoplasm of swollen and nonswollen cells. Similarly, transfection of cells with a green fluorescent protein-labeled pICln construct failed to reveal any membrane localization of the protein. These findings do not support the hypothesis that pICln is a volume regulatory anion channel activated by swelling-induced membrane insertion.
Collapse
Affiliation(s)
- F Emma
- Renal Division, Children's Hospital, Boston, Massachusetts 02115, USA
| | | | | | | | | |
Collapse
|
505
|
Strange K. Molecular identity of the outwardly rectifying, swelling-activated anion channel: time to reevaluate pICln. J Gen Physiol 1998; 111:617-22. [PMID: 9565399 PMCID: PMC2217135 DOI: 10.1085/jgp.111.5.617] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/1997] [Accepted: 03/16/1998] [Indexed: 11/29/2022] Open
Affiliation(s)
- K Strange
- Laboratory of Cellular and Molecular Physiology, Departments of Anesthesiology and Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
| |
Collapse
|
506
|
Clapham DE. The list of potential volume-sensitive chloride currents continues to swell (and shrink). J Gen Physiol 1998; 111:623-4. [PMID: 9565400 PMCID: PMC2217136 DOI: 10.1085/jgp.111.5.623] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- D E Clapham
- Howard Hughes Medical Institute, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA
| |
Collapse
|
507
|
Krapivinsky G, Pu W, Wickman K, Krapivinsky L, Clapham DE. pICln binds to a mammalian homolog of a yeast protein involved in regulation of cell morphology. J Biol Chem 1998; 273:10811-4. [PMID: 9556550 DOI: 10.1074/jbc.273.18.10811] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Since its cloning and tentative identification as a chloride channel, the function of the pICln protein has been debated. Although there is no consensus regarding the specific function of pICln, it was suggested to play a role, directly or indirectly, in the function of a swelling-induced chloride conductance. Previously, the protein was shown to exist in several discrete protein complexes. To determine the function of the protein, we have begun the systematic identification of all proteins to which it binds. Here we show that four proteins firmly bind to pICln and identify the 72-kDa pICln-binding protein by affinity purification and peptide microsequencing. The interaction between this protein and pICln was verified several ways, including the extraction of several pICln clones from a cDNA library using the 72-kDa protein as a bait in a yeast two-hybrid screen. The protein is homologous to the yeast Skb1 protein. Skb1 interacts with Shk1, a homolog of the p21(Cdc42/Rac)-activated protein kinases (PAKs). The known involvement of PAKs in cytoskeletal rearrangement suggests that pICln may be linked to a system regulating cell morphology.
Collapse
Affiliation(s)
- G Krapivinsky
- Howard Hughes Medical Institute, Cardiovascular Division, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA
| | | | | | | | | |
Collapse
|
508
|
Voets T, Buyse G, Droogmans G, Eggermont J, Nilius B. The GXGXG motif in the pI(Cln) protein is not important for the nucleotide sensitivity of the pI(Cln)-induced Cl- current in Xenopus oocytes. FEBS Lett 1998; 426:171-3. [PMID: 9599001 DOI: 10.1016/s0014-5793(98)00334-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
It has been proposed that the pI(Cln) protein forms a nucleotide-sensitive plasma membrane anion channel with a GXGXG motif being an essential component of the extracellular nucleotide-binding site. To evaluate this hypothesis, we have performed voltage-clamp experiments on Xenopus laevis oocytes injected with RNA encoding a rat mutant pI(Cln) in which the three glycines of the putative nucleotide-binding site have been changed into alanines (G54A; G56A; G58A). The injected oocytes displayed outwardly rectifying anion currents, which were voltage-dependently blocked by extracellular cAMP, but which were not affected by removal of extracellular Ca2+. Furthermore, the mutation did not affect the voltage-dependent inactivation. We therefore conclude that there is no evidence in favour of an extracellular nucleotide-binding site in pI(Cln).
Collapse
Affiliation(s)
- T Voets
- Katholieke Universiteit Leuven, Laboratorium voor Fysiologie Campus Gasthuisberg O and N, Belgium
| | | | | | | | | |
Collapse
|
509
|
Lytle C. A volume-sensitive protein kinase regulates the Na-K-2Cl cotransporter in duck red blood cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:C1002-10. [PMID: 9575797 DOI: 10.1152/ajpcell.1998.274.4.c1002] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
When Na-K-2Cl cotransport is activated in duck red blood cells by either osmotic cell shrinkage, norepinephrine, fluoride, or calyculin A, phosphorylation of the transporter occurs at a common set of serine/threonine sites. To examine the kinetics and regulation of the activating kinase, phosphatase activity was inhibited abruptly with calyculin A and the subsequent changes in transporter phosphorylation and activity were determined. Increases in fractional incorporation of 32P into the transporter and uptake of 86Rb by the cells were closely correlated, suggesting that the phosphorylation event is rate determining in the activation process. Observed in this manner, the activating kinase was 1) stimulated by cell shrinkage, 2) inhibited by cell swelling, staurosporine, or N-ethylmaleimide, and 3) unaffected by norepinephrine or fluoride. The inhibitory effect of swelling on kinase activity was progressively relieved by calyculin A, suggesting that the kinase itself is switched on by phosphorylation. The kinetics of activation by calyculin A conformed to an autocatalytic model in which the volume-sensitive kinase is stimulated by a product of its own reaction (e.g., via autophosphorylation).
Collapse
Affiliation(s)
- C Lytle
- Division of Biomedical Sciences, University of California, Riverside 92521, USA
| |
Collapse
|
510
|
Linsdell P, Hanrahan JW. Adenosine triphosphate-dependent asymmetry of anion permeation in the cystic fibrosis transmembrane conductance regulator chloride channel. J Gen Physiol 1998; 111:601-14. [PMID: 9524141 PMCID: PMC2217125 DOI: 10.1085/jgp.111.4.601] [Citation(s) in RCA: 129] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/1997] [Accepted: 02/10/1998] [Indexed: 11/20/2022] Open
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) forms a tightly regulated channel that mediates the passive diffusion of Cl- ions. Here we show, using macroscopic current recording from excised membrane patches, that CFTR also shows significant, but highly asymmetrical, permeability to a broad range of large organic anions. Thus, all large organic anions tested were permeant when present in the intracellular solution under biionic conditions (PX/PCl = 0.048-0.25), whereas most were not measurably permeant when present in the extracellular solution. This asymmetry was not observed for smaller anions. ATPase inhibitors that "lock" CFTR channels in the open state (pyrophosphate, 5'-adenylylimidodiphosphate) disrupted the asymmetry of large anion permeation by allowing their influx from the extracellular solution, which suggests that ATP hydrolysis is required to maintain asymmetric permeability. The ability of CFTR to allow efflux of large organic anions represents a novel function of CFTR. Loss of this function may contribute to the pleiotropic symptoms seen in cystic fibrosis.
Collapse
Affiliation(s)
- P Linsdell
- Department of Physiology, McGill University, Montréal, Québec, Canada
| | | |
Collapse
|
511
|
Yamazaki J, Duan D, Janiak R, Kuenzli K, Horowitz B, Hume JR. Functional and molecular expression of volume-regulated chloride channels in canine vascular smooth muscle cells. J Physiol 1998; 507 ( Pt 3):729-36. [PMID: 9508834 PMCID: PMC2230812 DOI: 10.1111/j.1469-7793.1998.729bs.x] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/1997] [Accepted: 01/27/1998] [Indexed: 02/06/2023] Open
Abstract
1. We examined the possibility of functional and molecular expression of volume-regulated Cl- channels in vascular smooth muscle using the whole-cell patch-clamp technique and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) on cells from canine pulmonary and renal arteries. 2. Decreasing external osmolarity induced cell swelling, which was accompanied by activation of Cl--dependent outward-rectifying membrane currents with an anion permeability sequence of SCN- > I- > Br- > Cl- > aspartate-. These currents were sensitive to block by DIDS, extracellular ATP and the antioestrogen compound tamoxifen. 3. Experiments were performed to determine whether the molecular form of the volume-regulated chloride channel (ClC-3) is expressed in pulmonary and renal arteries. Quantitative RT-PCR confirmed expression of ClC-3 in both types of smooth muscle. ClC-3 expression was 76.4 % of beta-actin in renal artery and 48.0 % of beta-actin in pulmonary artery. 4. We conclude that volume-regulated Cl- channels are expressed in vascular smooth muscle cells and exhibit functional properties similar to those found in other types of cells, presumably contributing to the regulation of cell volume, electrical activity and, possibly, myogenic tone.
Collapse
Affiliation(s)
- J Yamazaki
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557-0046, USA
| | | | | | | | | | | |
Collapse
|
512
|
Basavappa S, Pedersen SF, Jørgensen NK, Ellory JC, Hoffmann EK. Swelling-induced arachidonic acid release via the 85-kDa cPLA2 in human neuroblastoma cells. J Neurophysiol 1998; 79:1441-9. [PMID: 9497423 DOI: 10.1152/jn.1998.79.3.1441] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Arachidonic acid or its metabolites have been implicated in the regulatory volume decrease (RVD) response after hypotonic cell swelling in some mammalian cells. The present study investigated the role of arachidonic acid (AA) during RVD in the human neuroblastoma cell line CHP-100. During the first nine minutes of hypo-osmotic exposure the rate of 3H-arachidonic acid (3H-AA) release increased to 250 +/- 19% (mean +/- SE, n = 22) as compared with cells under iso-osmotic conditions. This release was significantly inhibited after preincubation with AACOCF3, an inhibitor of the 85-kDa cytosolic phospholipase A2 (cPLA2). This indicates that a PLA2, most likely the 85-kDa cPLA2 is activated during cell swelling. In contrast, preincubation with U73122, an inhibitor of phospholipase C, did not affect the swelling-induced release of 3H-AA. Swelling-activated efflux of 36Cl and 3H-taurine were inhibited after preincubation with AACOCF3. Thus the swelling-induced activation of cPLA2 may be essential for stimulation of both 36Cl and 3H-taurine efflux during RVD. As the above observation could result from a direct effect of AA or its metabolite leukotriene D4 (LTD4), the effects of these agents were investigated on swelling-induced 36Cl and 3H-taurine effluxes. In the presence of high concentrations of extracellular AA, the swelling-induced efflux of 36Cl and 3H-taurine were inhibited significantly. In contrast, addition of exogenous LTD4 had no significant effect on the swelling-activated 36Cl efflux. Furthermore, exogenous AA increased cytosolic calcium levels as measured in single cells loaded with the calcium sensitive dye Fura-2. On the basis of these results we propose that cell swelling activates phospholipase A2 and that this activation via an increased production of AA or some AA metabolite(s) other than LTD4 is essential for RVD.
Collapse
Affiliation(s)
- S Basavappa
- University Laboratory of Physiology, University of Oxford, Oxford OX1 3PT, United Kingdom
| | | | | | | | | |
Collapse
|
513
|
Song D, O'Regan MH, Phillis JW. Amino acid release during volume regulation by cardiac cells: cellular mechanisms. Eur J Pharmacol 1998; 341:273-80. [PMID: 9543249 DOI: 10.1016/s0014-2999(97)01440-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Mechanisms of amino acid efflux during volume regulation in hypoosmotically treated isolated rat hearts were studied by collecting the coronary artery perfusate and analysis by high pressure liquid chromatography. Hypoosmotic stress resulted in marked percentage increases in perfusate taurine, aspartate and glutamate levels, smaller increases in phosphoethanolamine, glycine and alanine and non-significant increases in serine and glutamine. Amino acid levels declined during reperfusion with isosmotic perfusate. The anion channel blocker 4-acetamido-4-isothiocyanostilbene-2:2'-disulfonic acid (SITS, 500 microM) significantly reduced hypoosmotic release of taurine, aspartate, glutamate and glycine. Furosemide reduced hypoosmotically-evoked releases of taurine, glycine, alanine and phosphoethanolamine. The polyunsaturated amino acids, arachidonic and linoleic also reduced amino acid efflux. Phospholipase A2 inhibition with 7,7-dimethyleicosadienoic acid (DEDA, 2 microM) reduced osmotically-evoked releases of taurine, aspartate and glutamate. 4-Bromophenacyl bromide (1 microM) inhibited osmotically-evoked release of glutamate and glycine. Combined applications of SITS + DEDA markedly reduced osmotically evoked release of all eight amino acids. Glutamate and aspartate effluxes were not inhibited by the glutamate transport inhibitor dihydrokainic acid (1 mM). These results indicate that the hypoosmotic stress, by inducing cell swelling, can initiate an amino acid efflux as part of a regulatory volume decrease. An opening of anion-permeant channels and phospholipase activation appear to be involved in the regulatory volume decrease phenomenon.
Collapse
Affiliation(s)
- D Song
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201-1928, USA
| | | | | |
Collapse
|
514
|
Lang F, Busch GL, Ritter M, Völkl H, Waldegger S, Gulbins E, Häussinger D. Functional significance of cell volume regulatory mechanisms. Physiol Rev 1998; 78:247-306. [PMID: 9457175 DOI: 10.1152/physrev.1998.78.1.247] [Citation(s) in RCA: 1268] [Impact Index Per Article: 48.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
To survive, cells have to avoid excessive alterations of cell volume that jeopardize structural integrity and constancy of intracellular milieu. The function of cellular proteins seems specifically sensitive to dilution and concentration, determining the extent of macromolecular crowding. Even at constant extracellular osmolarity, volume constancy of any mammalian cell is permanently challenged by transport of osmotically active substances across the cell membrane and formation or disappearance of cellular osmolarity by metabolism. Thus cell volume constancy requires the continued operation of cell volume regulatory mechanisms, including ion transport across the cell membrane as well as accumulation or disposal of organic osmolytes and metabolites. The various cell volume regulatory mechanisms are triggered by a multitude of intracellular signaling events including alterations of cell membrane potential and of intracellular ion composition, various second messenger cascades, phosphorylation of diverse target proteins, and altered gene expression. Hormones and mediators have been shown to exploit the volume regulatory machinery to exert their effects. Thus cell volume may be considered a second message in the transmission of hormonal signals. Accordingly, alterations of cell volume and volume regulatory mechanisms participate in a wide variety of cellular functions including epithelial transport, metabolism, excitation, hormone release, migration, cell proliferation, and cell death.
Collapse
Affiliation(s)
- F Lang
- Institute of Physiology, University of Tübingen, Germany
| | | | | | | | | | | | | |
Collapse
|
515
|
Rezaie A, Esmon N, Esmon C. The high affinity calcium-binding site involved in protein C activation is outside the first epidermal growth factor homology domain. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)49753-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
|