scholarly journals Acute activation of NHE3 by dexamethasone correlates with activation of SGK1 and requires a functional glucocorticoid receptor

2007 ◽  
Vol 292 (1) ◽  
pp. C396-C404 ◽  
Author(s):  
Dongsheng Wang ◽  
Huanchun Zhang ◽  
Florian Lang ◽  
C. Chris Yun
Keyword(s):  
Glucocorticoid Receptor ◽  
Kinase Activity ◽  
Actinomycin D ◽  
Acute Effect ◽  
Protein Abundance ◽  
Transport Activity ◽  
Opossum Kidney ◽  
Opossum Kidney Cells ◽  
Dependent Mechanism ◽  
Stimulation Of

Glucocorticoids stimulate the intestinal absorption of Na+ and water partly by regulation of the Na+/H+ exchanger 3 (NHE3). Previous studies have shown both genomic and nongenomic regulation of NHE3 by glucocorticoids. Serum and glucocorticoid-inducible kinase 1 (SGK1) has been shown to be part of this cascade, where phosphorylation of NHE3 by SGK1 initiates the translocation of NHE3 to the cell surface. In the present work, we examined a series of changes in SGK1 and NHE3 induced by glucocorticoids using human colonic Caco-2 and opossum kidney cells. We found that dexamethasone rapidly stimulated SGK1 mRNAs, but a significant change in protein abundance was not detected. Instead, there was an increase in SGK1 kinase activity as early as at 2 h. An increase in NHE3 protein abundance was not detected until 12 h of dexamethasone exposure, although the transport activity was significantly stimulated at 4 h. These data demonstrate that the changes of SGK1 precede those of NHE3. Chronic regulation (24 h) of NHE3 was blocked completely by prevention of protein synthesis with cycloheximide or actinomycin D and by the glucocorticoid receptor blocker RU486. The acute effect of dexamethasone was similarly abrogated by RU486, but was insensitive to cycloheximide and actinomycin D. Similarly, the stimulation of SGK1 activity by dexamethasone was blocked by RU486 but not by actinomycin D. Together, these data show that the acute effect of glucocorticoids on NHE3 is mediated by a glucocorticoid receptor dependent mechanism that activates SGK1 in a nongenomic manner.

Modulation of Na+-Pi cotransport in opossum kidney cells by extracellular phosphate

1988 ◽  
Vol 255 (2) ◽  
pp. C155-C161 ◽  
Author(s):  
J. Biber ◽  
J. Forgo ◽  
H. Murer
Keyword(s):  
Actinomycin D ◽  
Phosphate Transport ◽  
Kidney Cells ◽  
Transport Activity ◽  
Similar Extent ◽  
Opossum Kidney ◽  
Ok Cells ◽  
Opossum Kidney Cells ◽  
Dependent Transport ◽  
Posttranscriptional Level

The effect of the extracellular concentration of Pi on the Na+-dependent phosphate transport activity of OK cells was investigated. When incubated with extracellular Pi at concentrations of 200 microM or less, Na+-Pi cotransport increased approximately twofold in OK cells compared with control cells (kept in 0.85 mM Pi), whereas other Na+-dependent transport activities were not affected. After Pi deprivation, Na+-Pi cotransport could be inhibited to a similar extent (80%) by parathyroid hormone (PTH) as in control cells, suggesting that the PTH-sensitive Na+-Pi cotransport activity is also regulated by extracellular Pi. The increase of Na+-Pi cotransport was maximally expressed after 6 h and could be prevented by cycloheximide (70 microM) but not by actinomycin D (0.5-5 g/ml). However, the adaptive response was completely blocked by 3'-deoxyadenosine (cordycepin) at 100 microM. From these data, it is concluded that the upregulation of Na+-Pi cotransport in OK cells due to low extracellular Pi is controlled at a posttranscriptional level.

Stimulation of P(i) transport in opossum kidney cells by hyposmotic media

1993 ◽  
Vol 264 (4) ◽  
pp. F585-F592
Author(s):  
M. Loghman-Adham ◽  
G. T. Motock
Keyword(s):  
Fluid Phase ◽  
Kinetic Studies ◽  
Uptake Kinetic ◽  
Opossum Kidney ◽  
Pi Transport ◽  
Opossum Kidney Cells ◽  
Fluid Phase Endocytosis ◽  
Peroxidase Uptake ◽  
Stimulation Of

Exposure of various cells to hyposmotic media (Hypo) results in a rapid inhibition of both receptor-mediated and fluid-phase endocytosis. We used this maneuver to investigate the role of endocytosis in regulation of Pi transport in opossum kidney (OK) cells. Following exposure to Hypo, Na(+)-dependent Pi uptake increased rapidly, reaching a maximum within 5 min, and remained elevated up to 30 min. This was associated with a simultaneous reduction of horseradish peroxidase uptake. Kinetic studies showed increased apparent Vmax for Pi (9.38 +/- 0.93 vs. 13.08 +/- 1.04 nmol.mg-1.5 min-1 for control and Hypo, respectively; P < 0.05, n = 6) with no change in apparent Km. The effect was specific for Pi with no change in the Na(+)-dependent or -independent uptake of L-proline, L-glutamine, or methyl-alpha-D-glucopyranoside. Stimulation of Pi transport persisted when control and Hypo had identical ionic compositions. Stimulation of Pi transport was rapidly reversed when cells were returned to an isosmotic medium. Preincubation with Hypo at 4 degrees C had no effect on Pi transport. Addition of cycloheximide or actinomycin D did not prevent the increased Pi uptake after exposure to Hypo. The effect also persisted after protein kinase C downregulation. Stimulation of Pi transport by Hypo is consistent with reduced endocytic retrieval of Na(+)-Pi cotransporters from brush-border membrane (BBM), resulting in an increase in their number on the BBM.

scholarly journals Insulin-induced Stimulation of Na+,K+-ATPase Activity in Kidney Proximal Tubule Cells Depends on Phosphorylation of the α-Subunit at Tyr-10

1999 ◽  
Vol 10 (9) ◽  
pp. 2847-2859 ◽  
Author(s):  
Eric Féraille ◽  
Maria Luisa Carranza ◽  
Sandrine Gonin ◽  
Pascal Béguin ◽  
Carlos Pedemonte ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Tyrosine Phosphorylation ◽  
Site Directed Mutagenesis ◽  
Common Mechanism ◽  
Sodium Reabsorption ◽  
Kidney Cells ◽  
Α Subunit ◽  
Opossum Kidney ◽  
Opossum Kidney Cells ◽  
Stimulation Of

Phosphorylation of the α-subunit of Na+,K+-ATPase plays an important role in the regulation of this pump. Recent studies suggest that insulin, known to increase solute and fluid reabsorption in mammalian proximal convoluted tubule (PCT), is stimulating Na+,K+-ATPase activity through the tyrosine phosphorylation process. This study was therefore undertaken to evaluate the role of tyrosine phosphorylation of the Na+,K+-ATPase α-subunit in the action of insulin. In rat PCT, insulin and orthovanadate (a tyrosine phosphatase inhibitor) increased tyrosine phosphorylation level of the α-subunit more than twofold. Their effects were not additive, suggesting a common mechanism of action. Insulin-induced tyrosine phosphorylation was prevented by genistein, a tyrosine kinase inhibitor. The site of tyrosine phosphorylation was identified on Tyr-10 by controlled trypsinolysis in rat PCTs and by site-directed mutagenesis in opossum kidney cells transfected with rat α-subunit. The functional relevance of Tyr-10 phosphorylation was assessed by 1) the abolition of insulin-induced stimulation of the ouabain-sensitive86Rb uptake in opossum kidney cells expressing mutant rat α1-subunits wherein tyrosine was replaced by alanine or glutamine; and 2) the similarity of the time course and dose dependency of the insulin-induced increase in ouabain-sensitive 86Rb uptake and tyrosine phosphorylation. These findings indicate that phosphorylation of the Na+,K+-ATPase α-subunit at Tyr-10 likely participates in the physiological control of sodium reabsorption in PCT.

scholarly journals Phosphorylation of rat kidney Na-K pump at Ser938 is required for rapid angiotensin II-dependent stimulation of activity and trafficking in proximal tubule cells

2016 ◽  
Vol 310 (3) ◽  
pp. C227-C232 ◽  
Author(s):  
Katherine J. Massey ◽  
Quanwen Li ◽  
Noreen F. Rossi ◽  
Susan M. Keezer ◽  
Raymond R. Mattingly ◽  
...  
Keyword(s):  
Plasma Membranes ◽  
Rat Kidney ◽  
Proximal Tubules ◽  
Kidney Cells ◽  
Ang Ii ◽  
Wild Type ◽  
Stimulate Activity ◽  
Opossum Kidney ◽  
Opossum Kidney Cells ◽  
Stimulation Of

How angiotensin (ANG) II acutely stimulates the Na-K pump in proximal tubules is only partially understood, limiting insight into how ANG II increases blood pressure. First, we tested whether ANG II increases the number of pumps in plasma membranes of native rat proximal tubules under conditions of rapid activation. We found that exposure to 100 pM ANG II for 2 min, which was previously shown to increase affinity of the Na-K pump for Na and stimulate activity threefold, increased the amount of the Na-K pump in plasma membranes of native tubules by 33%. Second, we tested whether previously observed increases in phosphorylation of the Na-K pump at Ser938 were part of the stimulatory mechanism. These experiments were carried out in opossum kidney cells, cultured proximal tubules stably coexpressing the ANG type 1 (AT1) receptor, and either wild-type or a S938A mutant of rat kidney Na-K pump under conditions found by others to stimulate activity. We found that 10 min of incubation in 10 pM ANG II stimulated activity of wild-type pumps from 2.3 to 3.5 nmol K·mg protein−1·min−1 and increased the amount of the pump in the plasma membrane by 80% but had no effect on cells expressing the S938A mutant. We conclude that acute stimulation of Na-K pump activity in native rat proximal tubules includes increased trafficking to the plasma membrane and that phosphorylation at Ser938 is part of the mechanism by which ANG II directly stimulates activity and trafficking of the rat kidney Na-K pump in opossum kidney cells.

scholarly journals Ouabain-insensitive acidification by dopamine in renal OK cells: primary control of the Na+/H+exchanger

2001 ◽  
Vol 281 (1) ◽  
pp. R10-R18 ◽  
Author(s):  
Pedro Gomes ◽  
M. A. Vieira-Coelho ◽  
P. Soares-da-Silva
Keyword(s):  
Adenylyl Cyclase ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Kidney Cells ◽  
Primary Control ◽  
Intracellular Acidification ◽  
Opossum Kidney ◽  
Opossum Kidney Cells ◽  
Stimulation Of

The present study was aimed at evaluating the role of D1- and D2-like receptors and investigating whether inhibition of Na+ transepithelial flux by dopamine is primarily dependent on inhibition of the apical Na+/H+ exchanger, inhibition of the basolateral Na+-K+-ATPase, or both. The data presented here show that opossum kidney cells are endowed with D1- and D2-like receptors, the activation of the former, but not the latter, accompanied by stimulation of adenylyl cyclase (EC50 = 220 ± 2 nM), marked intracellular acidification (IC50 = 58 ± 2 nM), and attenuation of amphotericin B-induced decreases in short-circuit current (28.6 ± 4.5% reduction) without affecting intracellular pH recovery after CO2 removal. These results agree with the view that dopamine, through the activation of D1- but not D2-like receptors, inhibits both the Na+/H+ exchanger (0.001933 ± 0.000121 vs. 0.000887 ± 0.000073 pH unit/s) and Na+-K+-ATPase without interfering with the Na+-independent HCO[Formula: see text] transporter. It is concluded that dopamine, through the action of D1-like receptors, inhibits both the Na+/H+ exchanger and Na+-K+-ATPase, but its marked acidifying effects result from inhibition of the Na+/H+exchanger only, without interfering with the Na+-independent HCO[Formula: see text] transporter and Na+-K+-ATPase.

Thyroid hormone stimulation of Na/Pi-cotransport in opossum kidney cells

1995 ◽  
Vol 431 (2) ◽  
pp. 266-271 ◽  
Author(s):  
Victor Sorribas ◽  
Daniel Markovich ◽  
Tiziano Verri ◽  
J�rg Biber ◽  
Heini Murer
Keyword(s):  
Thyroid Hormone ◽  
Kidney Cells ◽  
Opossum Kidney ◽  
Hormone Stimulation ◽  
Opossum Kidney Cells ◽  
Stimulation Of

Stimulation of Na+/H+ exchange activity by endothelin in opossum kidney cells

1995 ◽  
Vol 430 (1) ◽  
pp. 137-144 ◽  
Author(s):  
R. Walter ◽  
C. Helmle-Kolb ◽  
J. Forgo ◽  
U. Binswanger ◽  
H. Murer
Keyword(s):  
Kidney Cells ◽  
Opossum Kidney ◽  
Opossum Kidney Cells ◽  
Stimulation Of ◽  
Exchange Activity

scholarly journals Inhibition of the translocation of GLUT1 and GLUT4 in 3T3-L1 cells by the phosphatidylinositol 3-kinase inhibitor, wortmannin

1994 ◽  
Vol 300 (3) ◽  
pp. 631-635 ◽  
Author(s):  
J F Clarke ◽  
P W Young ◽  
K Yonezawa ◽  
M Kasuga ◽  
G D Holman
Keyword(s):  
Glucose Transport ◽  
Glucose Transporter ◽  
Kinase Activity ◽  
Kinase Inhibitor ◽  
Insulin Signalling ◽  
Reversible Inhibitor ◽  
Transport Activity ◽  
Insulin Stimulation ◽  
Gamma S ◽  
Stimulation Of

Wortmannin is a potent and reversible inhibitor of insulin-stimulated PtdIns 3-kinase activity in 3T3-L1 cells (IC50 = 2.6 +/- 0.8 nM). Wortmannin inhibits the PtdIns 3-kinase activity which is precipitated with antibodies against insulin receptor substrate 1 and against the alpha-p85 subunit of PtdIns 3-kinase. These observations suggest that wortmannin inhibits at the p110 catalytic subunit of PtdIns 3-kinase. Insulin stimulation of glucose transport in permeabilized 3T3-L1 cells is also inhibited by wortmannin (IC50 = 6.4 +/- 1.4 nM). Wortmannin did not inhibit basal glucose transport activity. The close similarity of the IC50 values for wortmannin inhibition of insulin-stimulated PtdIns 3-kinase and glucose transport activities suggests that the PtdIns 3-kinase is a key intermediate in insulin signalling of glucose-transport stimulation. The wortmannin inhibitory effect on transport is associated with a reduction in the cell-surface, but not the total cellular, levels of both GLUT1 and GLUT4 glucose transporter isoforms that are accessible to the cell-impermeant photolabel, ATB-BMPA. These photolabelling results suggest that the glucose transporter translocation process is dependent upon PtdIns 3-kinase activity. The stimulatory effect of guanosine 5′-[gamma-thio]triphosphate (GTP gamma S) on glucose transport activity in permeabilized cells is only partially blocked by concentrations of wortmannin that completely inhibit the stimulatory effect of insulin. The residual stimulatory effect of GTP gamma S that occurs in the presence of wortmannin suggests that at least part of the GTP gamma S effect is mediated at a signalling site that is downstream of the site at which wortmannin inhibits the insulin stimulation of PtdIns 3-kinase and glucose transport activities.

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