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Hyperosmolarity leads to an increase in derepressed system A activity in the renal epithelial cell line NBL-1.

ABSTRACT: Hyperosmolarity induced an increase in Na(+)-dependent L-alanine uptake in confluent monolayers of the established renal epithelial cell line NBL-1. This induction was attributable to system A and was only seen when the cells had been previously deprived of amino acids in the culture medium to derepress system A activity. It was additive to the adaptive regulation induction, and both were inhibited by cycloheximide. However, the hyperosmolarity effect was inhibited by colcemid (an inhibitor of microtubular function), but adaptive regulation was not. Otherwise, when cell monolayers were incubated in a control medium, basal Na(+)-dependent L-alanine uptake mediated by system B0 decreased. The results of this study show that: (i) system A activity was not induced by cell shrinkage and subsequent swelling due to extracellular hyperosmolarity when cells were incubated in control medium; (ii) previous expression of system A activity induced by amino acid starvation seems to be a prerequisite for further induction due to hyperosmolarity; and (iii) the effects of adaptive regulation and hyperosmotic stress are mediated by different mechanisms.

SUBMITTER: Soler C

PROVIDER: S-EPMC1132225 | biostudies-other | 1993 Feb

REPOSITORIES: biostudies-other

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Amino acid deprivation leads to the emergence of System A activity and the synthesis of a specific membrane glycoprotein in the bovine renal epithelial cell line NBL-1.

Project description:1. Amino acid deprivation of confluent monolayers of the bovine renal epithelial cell line NBL-1 causes a stimulation of Na(+)-dependent alanine transport. 2. This stimulation is mediated by a protein-synthesis-dependent induction of 2-(methylamino)isobutyric acid (methyl-AIB)-sensitive alanine transport activity (System A), which was not previously present in these cells. 3. Induction was prevented by the addition of methyl-AIB, alanine or glutamine. 4. Tunicamycin prevented the induction of alanine transport activity. 5. Induction of System A activity was accompanied by incorporation of [3H]mannose into a single membrane protein band of molecular mass 113-140 kDa. 6. These results are consistent with the possibility that induced System A activity in confluent NBL-1 cells is mediated by the synthesis of a 113-140 kDa membrane glycoprotein.

| S-EPMC1132677 | biostudies-other

Regulation of System B0 amino-acid-transport activity in the renal epithelial cell line NBL-1 and concomitant changes in SAAT1 hybridizing transcripts.

Project description:alpha-(Methylamino)isobutyric acid (MeAIB) insensitive Na(+)-dependent alanine transport activity in the bovine kidney cell line NBL-1 was increased upon amino acid starvation (> or = 20% over control levels). When L-phenylalanine (3 mM) was included in the starvation medium the increase was further enhanced (> or = 85% over control levels). In cells grown in control medium the Vmax, for MeAIB-insensitive Na+/alanine co-transport was found to be 6.0 +/- 0.7 nmol/3 min per mg (Km 41 +/- 12 microM) and for L-phenylalanine-treated amino-acid-starved cells the Vmax. was 21 +/- 5 nmol/3 min per mg (Km 92 +/- 40 microM). The increase in Vmax. was prevented by cycloheximide. Substrate specificity analysis identified the L-phenylalanine-induced transport system as System B0. [35S]Methionine labelling of cells during the amino acid starvation/phenylalanine treatments resulted in the differential labelling of a protein of 78 kDa. Northern-blot analysis using a SAAT1-specific probe revealed the presence of a new transcript (3.2 kb) in RNA extracted from cells incubated in amino acid starvation medium with L-phenylalanine included. The present findings suggest a novel means of control for System B0 by the use of physiological stress. It is also proposed that SAAT1 and System-B0 transcripts have considerable sequence similarity.

| S-EPMC1137094 | biostudies-other

Induction of the high-affinity Na(+)-dependent glutamate transport system XAG- by hypertonic stress in the renal epithelial cell line NBL-1.

Project description:The high-affinity Na(+)-dependent glutamate transport system XAG- is induced (threefold increase in Vmax. with no change in Km) by hypertonicity in the renal epithelial cell line NBL-1. This effect is dependent on protein synthesis and glycosylation and is accompanied by an increase in EAAC1 mRNA levels. Other Na(+)-dependent transport systems in this cell line do not respond to hypertonic stress. In contrast to recent findings [Ruiz-Montasell, Gomez-Angelats, Casado, Felipe, McGivan and Pastor-Anglada (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 9569-9573] showing that increased system A activity after hyperosmotic shock results from induction of a regulatory protein, this is the first demonstration that hypertonicity may increase the expression of the gene for an amino acid transport protein itself.

| S-EPMC1135950 | biostudies-other

Regulation of Na+,K(+)-ATPase and the Na+/K+/Cl- co-transporter in the renal epithelial cell line NBL-1 under osmotic stress.

Project description:The long-term adaptation of the Na+,K(+)-ATPase to hypertonicity was studied using the bovine renal epithelial cell line NBL-1. Na+,K(+)-ATPase activity measured in intact cells as the ouabain-sensitive fraction of Rb+ uptake was stimulated (40% above controls) after incubating the cells in hypertonic medium. This stimulation was not correlated with significant changes in the amount of Na+,K(+)-ATPase alpha 1 subunit protein. Nevertheless, the amount of alpha 1 but not beta 1 subunit mRNA progressively increased after hypertonic shock (3-4-fold above basal values). These results suggest that the alpha 1 subunit gene is modulated by medium osmolarity, although this does not necessarily involve enhanced translation of the mRNA into active alpha 1 protein. Indeed, the increase in the biological activity of the Na+,K(+)-ATPase is abolished when the electrochemical Na+ transmembrane gradient is depleted by monensin, which is consistent with a post-translational effect on the activity of the sodium pump. A furosemide-sensitive component of Rb+ uptake, attributable to Na+/K+/Cl- co-transporter activity, was very low when cells were cultured in a regular medium, but was greatly induced after hypertonic shock. This induction could not be blocked by cycloheximide. Colcemide addition slightly reduced the absolute increase in Na+/K+/Cl- co-transporter activity, while cytochalasin B significantly potentiated the effect triggered by hypertonic shock. It is concluded: (i) that in NBL-1 cells the alpha 1 but not the beta 1 subunit of the Na+,K(+)-ATPase is encoded by an osmotically sensitive gene, and (ii) that the Na+/K+/Cl- co-transporter, although an osmotically sensitive carrier, is induced by a mechanism that is independent of protein synthesis but may rely, in an undetermined manner, on the structure of the cytoskeletal network.

| S-EPMC1217774 | biostudies-other

Regulation of glycosylation of Lamp-1 in the bovine renal epithelial cell line NBL-1 by changes in the concentration of extracellular phosphate.

Project description:We have identified the bovine renal homologue of Lamp-1 (lysosomal-associated membrane glycoprotein 1). It has very similar physical characteristics to other Lamp-1 proteins from a wide variety of tissues and species. Partial sequence analysis has shown it to be 61% identical with human Lamp-1 and about 50% identical with rat and mouse Lamp-1. The extent of glycosylation of bovine Lamp-1 alters in response to changes in the concentration of extracellular phosphate. Bovine renal epithelial cells (NBL-1) grown in normal or phosphate-starved medium contain Lamp-1 of 120 kDa. However, if cells are grown in medium containing 8-10 mM phosphate, they contain Lamp-1 of only 100 kDa. The core protein and mRNA levels have been shown to remain constant under both conditions. Therefore the only conclusion is that the extent of Lamp-1 glycosylation must be changing in response to the extracellular concentration of phosphate. Unlike Carlsson and Fukuda [(1990) J. Biol. Chem. 265, 20488-20495], who showed that the human Lamp-1 protein contained polylactosaminoglycan residues, we have been unable to demonstrate the partial deglycosylation of bovine Lamp-1 by endo-beta-galactosidase. This enzyme removes polylactosaminoglycan groups from glycoproteins, and therefore indicates that the carbohydrate structure of bovine Lamp-1 is probably different from that of other Lamp-1 proteins. At present the physiological importance of bovine renal Lamp-1 and the changes in its extent of glycosylation are unknown. In this paper we postulate that Lamp-1 may be involved in the cycling of plasma-membrane proteins to the lysosome. This is based on the finding that the only other known effect of high extracellular phosphate on NBL-1 cells is to cause a decrease in the Vmax. of plasma-membrane-associated Na(+)-dependent phosphate transport [Helps and McGivan (1991) Eur. J. Biochem. 200, 797-803].

| S-EPMC1137371 | biostudies-other

Regulation of the glutamate transporter by amino acid deprivation and associated effects on the level of EAAC1 mRNA in the renal epithelial cell line NBL-I.

Project description:The glutamate transport system of the bovine renal epithelial cell line NBL-1 was studied. The Km for Na(+)-dependent glutamate transport was found to be 13.8 +/- 2.4 microM (Vmax. 365 +/- 19.2 pmol/3 min per mg) and for Na(+)-dependent aspartate transport 4.5 +/- 1.1 microM (Vmax. 108 +/- 6.3 pmol/3 min per mg). The Km values are in close agreement with those expected for high-affinity Na(+)-dependent glutamate transport by System XAG-. Upon deprivation of amino acids, the Vmax. for Na+/aspartate co-transport rose to 203 +/- 6.0 pmol/3 min per mg (Km 3.8 +/- 0.5 microns). A probe was constructed to the high-affinity excitatory amino acid carrier (EAAC1) [Kanai and Hediger (1992) Nature (London) 360, 467-471]. The probe hybridized to a 3.5 kb transcript. On deprivation of amino acids, the level of EAAC1 mRNA decreased sharply before the measurable increase in transport levels, but was subsequently restored to control levels. A motif, which we propose is linked to amino acid deprivation, was found in the EAAC1 primary sequence.

| S-EPMC1134624 | biostudies-other

Loss of RANBP3L leads to transformation of renal epithelial cells towards a renal clear cell carcinoma like phenotype.

Project description:BackgroundRenal cell carcinomas (RCC) are characterized by the deregulation of several hundred hyperosmolality-responsive genes. High expression of a subset of these genes including the Ran binding protein 3 like (RANBP3L) is linked to a favorable prognostic outcome in RCC. However, the cellular function of RANBP3L remains largely unknown.MethodsWe used CRISPR/Cas9-mediated gene editing to generate functional deletions of the Ranbp3l and nuclear factor of activated T cells 5 (Nfat5) gene loci in a murine renal cell line. The NFAT5-KO cells were used to assess the regulation of Ranbp3l by NFAT5 using immunofluorescence, RNA-Seq and promoter assays. RANBP3L-deficient cells were analyzed for changes in cell morphology, proliferation, migration and colony-forming capacity using immunofluorescence and live cell imaging. RANPB3L-dependent changes in gene expression were identified by RNA-Seq.ResultsWe show that NFAT5 directly regulates Ranpb3l under hyperosmotic conditions by binding its promoter. Functional analysis of RANBP3L-deficient cells revealed a loss of epithelial structure, an increased cell migration behavior and colony forming capacity, accompanied by massive alterations in gene expression, all of which are hallmarks for tumor cells. Strikingly, a RANBP3L dependent signature of 60 genes separated samples with clear cell carcinoma (KIRC) from papillary (KIRP), chromophobe renal carcinoma (KICH) and healthy tissue.ConclusionsLoss of RANBP3L induces a tumor like phenotype resembles RCC, especially KIRC, on the morphological and gene expression level and might promote tumor development and progression. Therapeutic reconstitution or elevation of osmoregulated RANBP3L expression might represent a novel treatment strategy for RCC or KIRC.

| S-EPMC8265145 | biostudies-literature

Identification of Wnt responsive genes using a murine mammary epithelial cell line model system.

Project description:The Wnt/Wg pathway plays an important role in the developmental program of many cells and tissues in a variety of organisms. In addition, many Wnts and components of their downstream signaling pathways, such as beta-catenin and APC, have been implicated in tumorigenesis. Over the past years, several genes have been identified as Wnt responsive, including c-myc, siamois, and cyclin D1.In order to identify additional genes responsive to Wnt signaling that contribute to the transformed phenotype, we performed a cDNA subtractive hybridization screen between a mouse mammary epithelial cell line that overexpresses Wnt-1 (C57MG/Wnt-1) and the parental cell line (C57MG). The screen identified a total of 67 genes to be up-regulated in response to Wnt signaling. Of these 67 genes, the up-regulation of 62 was subsequently confirmed by Northern and dot blot analyses (and, for a subset, semi-quantitative PCR) of RNA isolated from C57MG cells subjected to (1) an independent Wnt-1 retroviral infection, and (2) co-culture with Wnt-1 expressing cells. Among the confirmed Wnt-1 responsive genes, we further characterized a mouse homolog of the human transcription factor Basic Transcription Element Binding protein 2 (BTEB2), Wnt-1 Responsive Cdc42 homolog (Wrch-1), and Wnt-1 Induced Secreted Protein (WISP-1).Several novel genes were identified in this screen, as well as others that have been shown previously to be regulated by Wnt signaling, such as connexin43. The results indicate that cDNA subtractive hybridization is a useful method for identifying genes involved in the process of Wnt-1-induced transformation.

| S-EPMC425575 | biostudies-literature

Expression data from renal collecting duct epithelial cell line

Project description:Morphogenesis of epithelial tissues relies on the precise developmental control of cell polarity and architecture. In the early Drosophila embryo, the primary epithelium forms during cellularisation, following a tightly controlled genetic programme where specific sets of genes are up-regulated. Some of them, for instance, control membrane invagination between the nuclei anchored at the apical surface of the syncytium. We used microarrays to detail the global programme of gene expression underlying cellularisation and identified distinct classes of up-regulated genes during this process.

2018-03-08 | GSE111519 | GEO

Urinary Excretion of Tetrodotoxin Modeled in a Porcine Renal Proximal Tubule Epithelial Cell Line, LLC-PK₁.

Project description:This study examined the urinary excretion of tetrodotoxin (TTX) modeled in a porcine renal proximal tubule epithelial cell line, LLC-PK₁. Time course profiles of TTX excretion and reabsorption across the cell monolayers at 37 °C showed that the amount of TTX transported increased linearly for 60 min. However, at 4 °C, the amount of TTX transported was approximately 20% of the value at 37 °C. These results indicate that TTX transport is both a transcellular and carrier-mediated process. Using a transport inhibition assay in which cell monolayers were incubated with 50 µM TTX and 5 mM of a transport inhibitor at 37 °C for 30 min, urinary excretion was significantly reduced by probenecid, tetraethylammonium (TEA), l-carnitine, and cimetidine, slightly reduced by p-aminohippuric acid (PAH), and unaffected by 1-methyl-4-phenylpyridinium (MPP+), oxaliplatin, and cefalexin. Renal reabsorption was significantly reduced by PAH, but was unaffected by probenecid, TEA and l-carnitine. These findings indicate that TTX is primarily excreted by organic cation transporters (OCTs) and organic cation/carnitine transporters (OCTNs), partially transported by organic anion transporters (OATs) and multidrug resistance-associated proteins (MRPs), and negligibly transported by multidrug and toxic compound extrusion transporters (MATEs).

| S-EPMC5532667 | biostudies-other

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