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Koumangoye R, Omer S, Delpire E. Mistargeting of a truncated Na-K-2Cl cotransporter in epithelial cells. Am J Physiol Cell Physiol 2018; 315:C258-C276. [PMID: 29719172 DOI: 10.1152/ajpcell.00130.2018] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We recently reported the case of a young patient with multisystem failure carrying a de novo mutation in SLC12A2, the gene encoding the Na-K-2Cl cotransporter-1 (NKCC1). Heterologous expression studies in nonepithelial cells failed to demonstrate dominant-negative effects. In this study, we examined expression of the mutant cotransporter in epithelial cells. Using Madin-Darby canine kidney (MDCK) cells grown on glass coverslips, permeabilized support, and Matrigel, we show that the fluorescently tagged mutant cotransporter is expressed in cytoplasm and at the apical membrane and affects epithelium integrity. Expression of the mutant transporter at the apical membrane also results in the mislocalization of some of the wild-type transporter to the apical membrane. This mistargeting is specific to NKCC1 as the Na+-K+-ATPase remains localized on the basolateral membrane. To assess transporter localization in vivo, we created a mouse model using CRISPR/cas9 that reproduces the 11 bp deletion in exon 22 of Slc12a2. Although the mice do not display an overt phenotype, we show that the colon and salivary gland expresses wild-type NKCC1 abundantly at the apical pole, confirming the data obtained in cultured epithelial cells. Enough cotransporter must remain, however, on the basolateral membrane to participate in saliva secretion, as no significant decrease in saliva production was observed in the mutant mice.
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Affiliation(s)
- Rainelli Koumangoye
- Department of Anesthesiology, Vanderbilt University School of Medicine , Nashville, Tennessee
| | - Salma Omer
- Department of Anesthesiology, Vanderbilt University School of Medicine , Nashville, Tennessee
| | - Eric Delpire
- Department of Anesthesiology, Vanderbilt University School of Medicine , Nashville, Tennessee
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Williams JR, Payne JA. Cation transport by the neuronal K(+)-Cl(-) cotransporter KCC2: thermodynamics and kinetics of alternate transport modes. Am J Physiol Cell Physiol 2004; 287:C919-31. [PMID: 15175220 DOI: 10.1152/ajpcell.00005.2004] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Both Cs(+) and NH(4)(+) alter neuronal Cl(-) homeostasis, yet the mechanisms have not been clearly elucidated. We hypothesized that these two cations altered the operation of the neuronal K(+)-Cl(-) cotransporter (KCC2). Using exogenously expressed KCC2 protein, we first examined the interaction of cations at the transport site of KCC2 by monitoring furosemide-sensitive (86)Rb(+) influx as a function of external Rb(+) concentration at different fixed external cation concentrations (Na(+), Li(+), K(+), Cs(+), and NH(4)(+)). Neither Na(+) nor Li(+) affected furosemide-sensitive (86)Rb(+) influx, indicating their inability to interact at the cation translocation site of KCC2. As expected for an enzyme that accepts Rb(+) and K(+) as alternate substrates, K(+) was a competitive inhibitor of Rb(+) transport by KCC2. Like K(+), both Cs(+) and NH(4)(+) behaved as competitive inhibitors of Rb(+) transport by KCC2, indicating their potential as transport substrates. Using ion chromatography to measure unidirectional Rb(+) and Cs(+) influxes, we determined that although KCC2 was capable of transporting Cs(+), it did so with a lower apparent affinity and maximal velocity compared with Rb(+). To assess NH(4)(+) transport by KCC2, we monitored intracellular pH (pH(i)) with a pH-sensitive fluorescent dye after an NH(4)(+)-induced alkaline load. Cells expressing KCC2 protein recovered pH(i) much more rapidly than untransfected cells, indicating that KCC2 can mediate net NH(4)(+) uptake. Consistent with KCC2-mediated NH(4)(+) transport, pH(i) recovery in KCC2-expressing cells could be inhibited by furosemide (200 microM) or removal of external [Cl(-)]. Thermodynamic and kinetic considerations of KCC2 operating in alternate transport modes can explain altered neuronal Cl(-) homeostasis in the presence of Cs(+) and NH(4)(+).
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Affiliation(s)
- Jeffery R Williams
- Department of Physiology and Membrane Biology, One Shields Ave., University of California, Davis, CA 95616-8644, USA
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de Jong JC, Willems PHGM, van den Heuvel LPWJ, Knoers NVAM, Bindels RJM. Functional Expression of the Human Thiazide-Sensitive NaCl Cotransporter in Madin-Darby Canine Kidney Cells. J Am Soc Nephrol 2003; 14:2428-35. [PMID: 14514720 DOI: 10.1097/01.asn.0000089832.52063.f5] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
ABSTRACT. The thiazide-sensitive Na+-Cl−cotransporter (NCC), which is expressed on the apical membrane of epithelial cells lining the distal convoluted tubule, is responsible for the reabsorption of 5% to 10% of filtered Na+and Cl−. To date, functional studies on the structural and regulatory requirements for localized trafficking and ion-transporting activity of NCC have been hampered by lack of a suitable cell system expressing this cotransporter. Reported here is the functional expression of human NCC (hNCC) in a polarized mammalian cell of renal origin—that is, the high-resistance Madin-Darby canine kidney (MDCK) cell. Western blot testing revealed that the cells predominantly expressed the complex glycosylated (approximately 140 kD) form of hNCC. hNCC was present primarily in the apical part of the cell. The functionality of hNCC was demonstrated by the gain of thiazide-sensitive Na+uptake and transepithelial transport activity. Na+uptake was significantly increased after short-term (15 min) treatment with forskolin, whereas cyclic guanosine monophosphate, wortmannin, phorbol 12-myriatate 13-acetate, and staurosporine were without effect. This indicates that hNCC activity is regulated through cyclic adenosine monophosphate, rather than via cyclic guanosine monophosphate, phospho-inositide 3-kinases or protein kinase C. Aldosterone did not alter Na+uptake in the short term (15 min) but significantly increased the transport activity in the long term (16 h). The latter effect of aldosterone was due to an effect on the cytomegalovirus promoter/enhancer driving the expression of hNCC. hNCC-MDCK cells are a good model for the study of the regulation of apical trafficking and ion-transporting activity of hNCC. E-mail r.bindels@ncmls.kun.nl
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Affiliation(s)
- Joke C de Jong
- Department of Physiology, University Medical Centre Nijmegen, Nijmegen, The Netherlands
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Vibat CR, Holland MJ, Kang JJ, Putney LK, O'Donnell ME. Quantitation of Na+-K+-2Cl- cotransport splice variants in human tissues using kinetic polymerase chain reaction. Anal Biochem 2001; 298:218-30. [PMID: 11700976 DOI: 10.1006/abio.2001.5398] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A kinetic reverse transcription-polymerase chain reaction (RT-PCR)-based assay is described that can discriminate and quantitate differentially spliced mRNAs. This assay should be generally applicable for high-throughput quantitation of differentially spliced transcripts. The utility of this method was assessed for spliced transcripts encoded by the human Na+-K+-2Cl- cotransporter gene hNKCC1. Evidence is presented that the NKCC1 isoform of the human Na+-K+-2Cl- cotransporter is differentially spliced analogous to that recently described for the mouse Na+-K+-2Cl- cotransporter gene BSC2. The nucleotide sequences of the two human splice variants predict Na+-K+-2Cl- cotransporter proteins differing only in length. Stable transfectants expressing these human splice variants, designated NKCC1a or NKCC1b, were constructed. Both splice variants produce functional Na+-K+-2Cl- cotransporters in vivo. The abundance of NKCC1 mRNA and patterns of differential splicing in 10 different tissue types and three cell lines were quantitated using the kRT-PCR assay. The results showed that the total amount of NKCC1 mRNA varied by more than 30-fold in the human tissues and cell lines examined. The ratio of NKCC1a/NKCC1b varied nearly 70-fold among these same tissues and cell lines suggesting that differential splicing of the NKCC1 transcript may play a regulatory role in human tissues.
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Affiliation(s)
- C R Vibat
- Department of Human Physiology, Department of Biological Chemistry, School of Medicine, University of California, One Shields Avenue, Davis, California 95616, USA
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Payne JA, Ferrell C, Chung CY. Endogenous and exogenous Na-K-Cl cotransporter expression in a low K-resistant mutant MDCK cell line. Am J Physiol Cell Physiol 2001; 280:C1607-15. [PMID: 11350756 DOI: 10.1152/ajpcell.2001.280.6.c1607] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A low K-resistant mutant Madin-Darby canine kidney (MDCK) cell line, LK-C1, has been shown previously to lack functional Na-K-Cl cotransporter (NKCC) activity, indicating that it may be a useful NKCC “knockout” cell line for structure-function studies. Using immunological probes, we first characterized the defect in the endogenous NKCC protein of the LK-C1 cells and then fully restored NKCC activity in these cells by stably expressing the human secretory NKCC1 protein (hNKCC1). The endogenous NKCC protein of the LK-C1 cells was expressed at significantly lower levels than in wild-type MDCK cells and was not properly glycosylated. This latter finding indicated that the lack of functional NKCC activity in the LK-C1 cells may be due to the inability to process the protein to the plasma membrane. In contrast, exogenously expressed hNKCC1 protein was properly processed and fully functional at the plasma membrane. Significantly, the exogenous hNKCC1 protein was regulated in a manner similar to the protein in native secretory cells as it was robustly activated by cell shrinkage, calyculin A, and low-Cl incubation. Furthermore, when the LK-C1 cells formed an epithelium on permeable supports, the exogenous hNKCC1 protein was properly polarized and functional at the basolateral membrane. The low levels of endogenous NKCC protein expression, the absence of any endogenous NKCC transport activity, and the ability to form a polarized epithelium indicate that the LK-C1 cells offer an excellent expression system with which to study the molecular physiology of the cation Cl cotransporters.
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Affiliation(s)
- J A Payne
- Department of Human Physiology, School of Medicine, University of California, One Shields Ave, Davis, CA 95616, USA.
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Jennings ML, Milanick MA. Membrane Transport in Single Cells. Compr Physiol 1997. [DOI: 10.1002/cphy.cp140107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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7
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Regulation by nerve growth factor and protein phosphorylation of Na/K/2Cl cotransport and cell volume in PC12 cells. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)34099-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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8
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Handler JS, Burg MB. Application of Tissue Culture Techniques to Study of Renal Tubular Epithelia. Compr Physiol 1992. [DOI: 10.1002/cphy.cp080110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Simmons NL, Tivey DR. The effect of hyperosmotic challenge upon ion transport in cultured renal epithelial layers (MDCK). Pflugers Arch 1992; 421:503-9. [PMID: 1281313 DOI: 10.1007/bf00370263] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Exposure of the basal-lateral surfaces of MDCK epithelia, mounted in Ussing chambers, to medium made hyperosmotic by the non-electrolyte mannitol, resulted in a marked inhibition of the adrenaline-stimulated inward short-circuit current (Cl- secretion). This inhibition was unaccompanied by a reversal of the adrenaline-stimulated increment in tissue conductance, indicating that the inhibition was due to modulation of ion transport at the basal-lateral membranes. Loop-diuretic-sensitive 86Rb(K+) efflux mediated by the Na+ - K+ -2 Cl- cotransporter at the basal-lateral membranes was markedly stimulated by hypertonic exposure. A diuretic-sensitive K+ (Cl-) loss was observed in shrunken cells upon prolonged exposure (20 min), showing that the net direction of "cotransport" flux was outward. 86Rb(K+) efflux stimulated by adrenaline (100 microM), exogenous ATP (100 microM) and A23187 (10 microM) was attenuated in shrunken cells, suggesting that basal-lateral K+ conductance is reduced in hyperosmotic media. "Cotransport" stimulation by hyperosmotic medium was asymmetric, apical bathing hypertonicity being ineffective. These data are consistent with a low hydraulic permeability of the apical membranes.
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Affiliation(s)
- N L Simmons
- Department of Physiological Sciences, The Medical School, Newcastle upon Tyne, UK
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Sánchez Olea R, Pasantes-Morales H, Lázaro A, Cereijido M. Osmolarity-sensitive release of free amino acids from cultured kidney cells (MDCK). J Membr Biol 1991; 121:1-9. [PMID: 1646888 DOI: 10.1007/bf01870646] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The amino acid pool of MDCK cells was essentially constituted by alanine, glycine, glutamic acid, serine, taurine, lysine, beta-alanine and glutamine. Upon reductions in osmolarity, free amino acids were rapidly mobilized. In 50% hyposmotic solutions, the intracellular content of free amino acids decreased from 69 to 25 mM. Glutamic acid, taurine and beta-alanine were the most sensitive to hyposmolarity, followed by glycine, alanine and serine, whereas isoleucine, phenylalanine and valine were only weakly reactive. The properties of this osmolarity-sensitive release of amino acids were examined using 3H-taurine. Decreasing osmolarity to 85, 75 or 50% increased taurine efflux from 0.6% per min to 1.6, 3.5 and 5.06 per min, respectively. The time course of 3H-taurine release closely follows that of the regulatory volume decrease in MDCK cells. Taurine release was unaffected by removal of Na+, Cl- or Ca2+, or by treating cells with colchicine or cytochalasin. It was temperature dependent and decreased at low pH. Taurine release was unaffected by bumetanide (an inhibitor of the Na+/K+/2Cl- carrier); it was inhibited 16 and 67 by TEA and quinidine (inhibitors of K+ conductances), unaffected by gadolinium or diphenylamine-2-carboxylate (inhibitors of Cl- channels) and inhibited 50% by DIDS. The inhibitory effects of DIDS and quinidine were additive. Quinidine but not DIDS inhibited taurine uptake by MDCK cells.
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Affiliation(s)
- R Sánchez Olea
- Institute of Cell Physiology, University of Mexico, Mexico City
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11
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Chapter 6 Ion Transport and Adenylyl Cyclase System in Red Blood Cells. CURRENT TOPICS IN MEMBRANES 1991. [DOI: 10.1016/s0070-2161(08)60804-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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12
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Dharmsathaphorn K, Madara JL. Established intestinal cell lines as model systems for electrolyte transport studies. Methods Enzymol 1990; 192:354-89. [PMID: 2074798 DOI: 10.1016/0076-6879(90)92082-o] [Citation(s) in RCA: 154] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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13
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Wilcock C, Hickman JA. Characterisation of a Na+/K+/Cl- cotransporter in alkylating agent-sensitive L1210 murine leukemia cells. BIOCHIMICA ET BIOPHYSICA ACTA 1988; 946:359-67. [PMID: 3207751 DOI: 10.1016/0005-2736(88)90411-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The mode of influx of 86Rb+, a K+ congener, to exponentially proliferating L1210 murine leukemia cells, incubated in a Krebs-Ringer buffer, has been characterised. The influx was composed of a ouabain-sensitive fraction (approx. 40%), a loop diuretic-sensitive fraction (approx. 40%) and a fraction which was insensitive to both types of inhibitor (approx. 15%). The fraction of ouabain-insensitive 86Rb+ influx, which was fully inhibited by furosemide (1 mM) or bumetanide (100 microM), was completely inhibited when Cl- was completely substituted by nitrate or gluconate ions, but was slightly (29 +/- 12%) stimulated if the Cl- was substituted by Br-. The substitution of Na+ by Li+, choline or tetramethylammonium ions inhibited the loop diuretic-sensitive fraction of 86Rb+ uptake. These results suggested that a component of 86Rb+ influx to L1210 cells was mediated via a Na+/K+/Cl- cotransporter. 86Rb+ efflux from L1210 cells which had been equilibrated with 86Rb+ and incubated in the presence or absence of 1 mM ouabain, was insensitive to the loop diuretics. Additionally, efflux rates were found to be independent of the external concentration of K+, suggesting that efflux was not mediated by K+-K+ exchange. The initial rate of 86Rb+ influx to L1210 cells in the plateau phase of growth was reduced to 44% of that of exponentially dividing cells, the reduction being accounted for by significant decreases in both ouabain- and loop diuretic-sensitive influx; these cells were reduced in volume compared to cells in the exponential phase of cell growth. In cells which had been deprived of serum for 18 h, and which showed an increase of the proportion of cells in the G1 phase of the cell cycle, the addition of serum stimulated an immediate increase in the furosemide-sensitive component of 86Rb+ influx. Diuretic-sensitive 86Rb+ influx was not altered by the incubation of the cells with 100 microM dibutyryl cyclic AMP, but was inhibited by 10 microM of the cross-linking agent nitrogen mustard (bis(2-chloro-ethyl)methylamine, HN2).
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Affiliation(s)
- C Wilcock
- Cancer Research Campaign Experimental Chemotherapy Group, Aston University, Birmingham, U.K
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14
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Affiliation(s)
- T A Pressley
- Department of Physiology and Cell Biology, University of Texas Medical School, Houston 77225
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15
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Saier MH, Daniels GA, Boerner P, Lin J. Neutral amino acid transport systems in animal cells: potential targets of oncogene action and regulators of cellular growth. J Membr Biol 1988; 104:1-20. [PMID: 3054116 DOI: 10.1007/bf01871898] [Citation(s) in RCA: 111] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- M H Saier
- Department of Biology, University of California, San Diego, La Jolla 92093
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Giesen-Crouse EM, McRoberts JA. Coordinate expression of piretanide receptors and Na+,K+,Cl- cotransport activity in Madin-Darby canine kidney cell mutants. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)45391-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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17
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Scott DM. Differentiation in vitro of primary cultures and transfected cell lines of epithelial cells derived from the thick ascending limb of Henle's loop. Differentiation 1987; 36:35-46. [PMID: 2451630 DOI: 10.1111/j.1432-0436.1987.tb00179.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The use of primary cell cultures derived from defined locations of the kidney has enabled the study of certain kidney cell type-specific characteristics under defined environmental conditions. The use of primary cell cultures, however, has a number of inherent disadvantages, many of which may be overcome by the use of differentiated cell lines of defined origin. In this paper I describe in detail an approach to: (a) the isolation and culture of primary cultures derived from the thick ascending limb of Henle's loop (TALH), and (b) the production of differentiated cell lines by the transfection of these primary cell cultures with early region SV40 virus genes. The characteristics of these cultures and other TALH-derived cell lines are described.
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Affiliation(s)
- D M Scott
- Max-Planck-Institut für Systemphysiologie, Dortmund, Federal Republic of Germany
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Bolívar JJ, Lázaro A, Fernández S, Stefani E, Peña-Cruz V, Lechene C, Cereijido M. Rescue of a wild-type MDCK cell by a ouabain-resistant mutant. THE AMERICAN JOURNAL OF PHYSIOLOGY 1987; 253:C151-61. [PMID: 3300360 DOI: 10.1152/ajpcell.1987.253.1.c151] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
When wild-type MDCK cells (W-MDCK) were cocultured in mixed monolayers with a ouabain-resistant mutant (R-MDCK), the wild-type cells were protected from the effect of ouabain up to concentrations as high as 100 microM. Rescue depended on the dose of ouabain and on the proportion of each cell type in the coculture. The survival of R-MDCK cells at 1 microM ouabain was not endangered by varying from 1:9 to 9:1 the proportion of W-MDCK cells to be rescued. Ouabain binding revealed two kinds of binding sites in R-MDCK cells, one with high and the other with low affinity. Only the high affinity site was present in W-MDCK cells. Electron probe analysis of individual cells revealed that rescued cells kept a high K and a low Na intracellular contents, similar to control cells. Histograms of intracellular K/Na in cocultured cells treated with ouabain were unimodal. Using microinjection of Lucifer yellow or electrophysiological techniques we estimated that at most 13% of the R-MDCK and W-MDCK cells may be connected at a given time through cell-to-cell junctions. Therefore permanent cell-to-cell communication did not seem to play a central role in the rescue. W-MDCK cells cocultured with R-MDCK cells and subsequently separated, were not rescued. Thus rescue did not seem to depend on the transfer from R-MDCK to W-MDCK cells of either ouabain-resistant Na-K pumps or of information to synthesize them. It is speculated that intercellular communications were sporadic events, so that all cells may become intermittently connected and rescued.
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Gargus JJ. Selectable mutations altering two mechanisms of mammalian K+ transport are dominant. THE AMERICAN JOURNAL OF PHYSIOLOGY 1987; 252:C515-22. [PMID: 3578504 DOI: 10.1152/ajpcell.1987.252.5.c515] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Somatic cell mutants with altered K+ transport have previously been isolated from mutagenzied LMTK- cells for their ability to grow at subthreshold low-potassium concentrations (0.2 mM). These mutants fall into two classes: one class, LTK-5, possesses a functionally altered furosemide-sensitive Na+-K+-Cl- cotransport system and the other, LTK-1, an altered K+-conducting channel. Somatic cell hybrids have been formed between each of these cell lines and a wild-type L-cell line, making use of complementing selectable marker mutations carried by these parents, to establish the dominance of the K+ transport mutations. Hybrids were isolated and studied in two ways: clonal hybrid cell lines were selected in a manner unbiased toward their K+ transport phenotype, which was later assayed; and the number of independent hybrids arising in this single-selective condition was compared with the number arising in a condition which is double selective for the mutant phenotype as well. By both assays, hybrids formed with LTK-1 or LTK-5 as a parent uniformly exhibited the mutant phenotype by growth and cloning, whereas control hybrids with LMTK- as parent never did. This demonstrates both transport mutations to be dominant and thus potentially isolatable.
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Mills JW, Lubin M. Effect of adenosine 3',5'-cyclic monophosphate on volume and cytoskeleton of MDCK cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1986; 250:C319-24. [PMID: 3006500 DOI: 10.1152/ajpcell.1986.250.2.c319] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
We examined the effect of N6,2'-O-dibutyryladenosine 3',5'-cyclic monophosphate (DBcAMP) on the volume and cytoskeleton of confluent cultures of Madin-Darby canine kidney (MDCK) cells. A 90-min exposure to 1 mM DBcAMP resulted in a 20% reduction in volume as measured by [14C]-urea water space. The volume in cells exposed to isobutylmethylxanthine (IBMX, 0.1 mM) was reduced by 24%. In control cultures F-actin, revealed by staining with nitrobenzoxadiazole-phallacidin, was found at the base of the cell as fibers, at the junctional region as a circumferential band, and on the apical cell surface as a mottled fluorescence. A dense pattern of microtubules, revealed by indirect immunofluorescence, was seen throughout the cell. Exposure to DBcAMP for 90 min resulted in a change of F-actin fibers into dense bundles near the periphery of the cell. This effect was even more striking when cells were exposed to IBMX. Cytochalasin B disrupted F-actin and resulted in a volume reduction similar to that in DBcAMP. Neither DBcAMP nor IBMX affected the distribution of microtubules. Moreover, colchicine, which completely disrupted the microtubules, did not change MDCK cell volume. The results suggest that DBcAMP and F-actin play a role in volume control in MDCK cells.
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Sussman I, O'Brien TG. Characterization of a BALB/c 3T3 preadipose cell mutant with altered Na+K+Cl- cotransport activity. J Cell Physiol 1985; 124:153-9. [PMID: 4044649 DOI: 10.1002/jcp.1041240124] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A BALB/c 3T3 cell mutant (3T3-E12) was isolated by its ability to survive at a low extracellular K+ concentration (0.14 mM). The growth rate of mutant cells was less dependent on external K+ than parental cells. Analysis of potassium transport revealed that 3T3-E12 cells have a decreased activity of the furosemide-sensitive Na+K+Cl- cotransport system, both in the efflux and influx modes. This is shown to be a result of a decrease in the apparent affinity of the transport system for K+ and Na+, but not Cl-. Upon exposure to the phorbol ester 12-0-tetradecanoyl-phorbol-13-acetate (TPA), BALB/c 3T3 cells exhibited a maximal volume decrease of 20%, while mutant cells shrunk by only 7%, suggesting that regulation of cell volume, at least four exposure to a tumor promoter, is impaired in mutant cells compared to parental 3T3 cells.
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Tivey DR, Simmons NL, Aiton JF. Role of passive potassium fluxes in cell volume regulation in cultured HeLa cells. J Membr Biol 1985; 87:93-105. [PMID: 2416931 DOI: 10.1007/bf01870656] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Cultured HeLa cells behave as ideal osmometers when subjected to hyperosmolar media, and show no volume regulatory behavior. In hypoosmolar solutions, cell swelling is not as great as predicted, and this is due largely to a loss of intracellular KCl. In hyperosmolar solutions there is a stimulation of the ouabain-insensitive but loop diuretic-sensitive 86Rb+ (K+) pathway. Analysis of the K+, Na+ and Cl- dependency of this K+ flux pathway demonstrates that the increase is principally due to an increase in its maximal velocity (Vmax). The sensitivity of this pathway to diuretic inhibition is unchanged in hyperosmolar media. Diuretic-sensitive 86Rb+ (K+) efflux stimulated by hypertonicity shows no marked dependence on external K+. The K+ loss observed in hypoosmolar media is distinct from the K+ transport pathway stimulated by hyperosmolar media on the basis of its sensitivity to furosemide and anion dependence.
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27
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Characterization of a Na : K : 2C1 cotransport system in the apical membrane of a renal epithelial cell line (LLC-PK1). J Membr Biol 1985; 87:131-9. [PMID: 2416929 DOI: 10.1007/bf01870659] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
86Rb uptake into LLC-PK1 cells (an established renal epithelial cell line) was found to be comprised of an active ouabain-sensitive component, a loop diuretic-sensitive component which was passive and strictly dependent upon the presence of extracellular Na+ and Cl- for activity, and a "leak" component. The diuretic-sensitive component of influx was investigated further in apical membrane vesicles derived from these cells. A large fraction of 86Rb, 22Na and 36Cl flux into these vesicles was sensitive to inhibition by furosemide and dependent upon the presence of the other two co-ions, in keeping with the presence of a loop diuretic-sensitive Na+ : K+ : Cl- cotransport system. The kinetic parameters for Na+ and K+ interaction have been analyzed under initial linear zero trans conditions. The following values were obtained KmNa+ = 0.42 +/- 0.05 mmol/liter, Vmax = 303 +/- 24 pmol/mg/6 sec; KmK+ = 11.9 +/- 1.0 mmol/liter, VmaxK+ = 307 +/- 27 pmol/mg/6 sec. For Cl- interaction evidence for two cooperative binding sites with different affinities and different specificities were obtained. Thus, a stoichiometry of 1Na+ : 1K+ :2Cl- can be calculated. It is concluded that the apical membrane of LLC-PK1 cells contains a Na+ : K+ : 2Cl- co-transport system with properties similar to those described for the thick ascending limb of the loop of Henle.
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Cereijido M, Bolívar JJ, Lázaro A. A ouabain resistant epithelial cell that protects the wild type in co-cultures. Pflugers Arch 1985; 405 Suppl 1:S147-51. [PMID: 4088830 DOI: 10.1007/bf00581797] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
MDCK cells (epithelioid of renal origin) can be cultured as monolayers that resemble natural epithelia. A mutant of these cells (R-MDCK) can grow in cultures exposed to high doses of ouabain (e.g. 100 microM) because one half of its population of pumps has a negligible affinity for this drug. It can also protect the wild type for at least 86 h in co-cultures exposed to ouabain. This article reviews several possible mechanisms of protection, and suggests that it is due to exchange of Na+ and K+ taking place through gap junctions. These connections though, do not seem to be continuous features, but the cells couple intermittently so that, in a given moment, only 28% of them communicate.
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