Role of SGK in hormonal regulation of epithelial sodium channel in A6 cells

2003 ◽  
Vol 284 (2) ◽  
pp. C404-C414 ◽  
Author(s):  
Diego Alvarez de la Rosa ◽  
Cecilia M. Canessa
Keyword(s):  
Sodium Channel ◽  
Hormonal Regulation ◽  
Apical Membrane ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Epithelial Sodium Channel ◽  
Hormonal Stimulation ◽  
A6 Cells ◽  
Epithelial Sodium Channel Enac

The purpose of this study was to examine the role of the serum- and glucocorticoid-induced kinase (SGK) in the activation of the epithelial sodium channel (ENaC) by aldosterone, arginine vasopressin (AVP), and insulin. We used a tetracycline-inducible system to control the expression of wild-type (SGK[Formula: see text]), constitutively active (S425D mutation; SGK[Formula: see text]), or inactive (K130M mutation; SGK[Formula: see text]) SGK in A6 cells independently of hormonal stimulation. The effect of SGK expression on ENaC activity was monitored by measuring transepithelial amiloride-sensitive short-circuit current ( I sc) of transfected A6 cell lines. Expression of SGK[Formula: see text] or SGK[Formula: see text] and aldosterone stimulation have additive effects on I sc. Although SGK could play some role in the aldosterone response, our results suggest that other mechanisms take place. SGK[Formula: see text] abrogates the responses to AVP and insulin; hence, in the signaling pathways of these hormones there is a shared step that is stimulated by SGK. Because AVP and insulin induce fusion of vesicles to the apical membrane, our results support the notion that SGK promotes incorporation of channels in the apical membrane.

scholarly journals Cyclosporine stimulates the renal epithelial sodium channel by elevating cholesterol

2009 ◽  
Vol 296 (2) ◽  
pp. F284-F290 ◽  
Author(s):  
Jing Wang ◽  
Zhi-Ren Zhang ◽  
Chu-Fang Chou ◽  
You-You Liang ◽  
Yuchun Gu ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Epithelial Sodium Channel ◽  
Disulfonic Acid ◽  
Severe Side Effect ◽  
Open Probability ◽  
A6 Cells ◽  
Induced Hypertension ◽  
Microscopy Data ◽  
Abca1 Protein ◽  
Epithelial Sodium Channel Enac

Cyclosporine A (CsA) is an efficient immunosuppressant used for reducing allograft rejection but with a severe side effect of causing hypertension. We hypothesize that the renal epithelial sodium channel (ENaC) may participate in CsA-induced hypertension. In the present study, we used the patch-clamp cell-attached configuration to examine whether and how CsA stimulates ENaC in A6 distal nephron cells. The data showed that CsA significantly increased ENaC open probability. Since CsA is an inhibitor of the ATP-binding cassette A1 (ABCA1) transporter, we employed 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS), another ABCA1 inhibitor, and found that DIDS mimicked the effects of CsA on ENaC basal and cholesterol-induced activity but without any additive effect if combined with CsA. CsA and DIDS also had an identical effect on reduced ENaC activity caused by cholesterol extraction. ABCA1 protein was detected in A6 cells by Western blot analysis. Confocal microscopy data showed that both CsA and DIDS facilitated A6 cells to uptake cholesterol. Since enhanced ENaC activity is known to cause hypertension, these data together suggest that CsA may cause hypertension by stimulating ENaC through a pathway associated with inhibition of ABCA1 and consequent elevation of cholesterol in the cells.

Hormonal regulation of Na+-K+-ATPase in cultured epithelial cells

1986 ◽  
Vol 251 (2) ◽  
pp. C186-C190 ◽  
Author(s):  
J. P. Johnson ◽  
D. Jones ◽  
W. P. Wiesmann
Keyword(s):  
Enzyme Activity ◽  
Epithelial Cells ◽  
Atpase Activity ◽  
Hormonal Regulation ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Toad Urinary Bladder ◽  
A6 Cells ◽  
Cultured Epithelial Cells ◽  
Stimulation Of

Aldosterone and insulin stimulate Na+ transport through mechanisms involving protein synthesis. Na+-K+-ATPase has been implicated in the action of both hormones. We examined the effect of aldosterone and insulin on Na+-K+-ATPase in epithelial cells in culture derived from toad urinary bladder (TB6C) and toad kidney (A6). Aldosterone, but not insulin, increases short-circuit current (ISC) in TB6C cells. Aldosterone increases Na+-K+-ATPase activity after 18 h of incubation, but no effect can be seen at 3 and 6 h. Amiloride, which inhibits aldosterone-induced increases in ISC, has no effect on either basal or aldosterone stimulated enzyme activity. Both aldosterone and insulin increase ISC in A6 cells and when added together are synergistic. Aldosterone stimulates enzyme activity in A6 cells, but insulin alone has no effect. However, aldosterone and insulin together stimulate enzyme activity more than aldosterone alone. It appears that stimulation of Na+-K+-ATPase activity is involved in aldosterone action in both cell lines but does not appear to be due to increased Na+ entry, since enhanced enzyme activity is not inhibited by amiloride. In contrast, insulin alone has no direct effect on Na+-K+-ATPase, although the increased enzyme activity following both agents in combination may explain their synergism on ISC.

scholarly journals The Epithelial Sodium Channel (ENaC) Traffics to Apical Membrane in Lipid Rafts in Mouse Cortical Collecting Duct Cells

2007 ◽  
Vol 282 (52) ◽  
pp. 37402-37411 ◽  
Author(s):  
Warren G. Hill ◽  
Michael B. Butterworth ◽  
Huamin Wang ◽  
Robert S. Edinger ◽  
Jonathan Lebowitz ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Lipid Rafts ◽  
Apical Membrane ◽  
Collecting Duct ◽  
Epithelial Sodium Channel ◽  
Cortical Collecting Duct ◽  
Duct Cells ◽  
Collecting Duct Cells ◽  
Epithelial Sodium Channel Enac

scholarly journals Molecular mechanisms for intestinal HCO3- secretion and its regulation by guanylin in seawater-acclimated eels

2019 ◽  
Author(s):  
Yoshio Takei ◽  
Marty K.S. Wong ◽  
Masaaki Ando
Keyword(s):  
Hormonal Regulation ◽  
Time Course ◽  
Molecular Mechanisms ◽  
Apical Membrane ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Short Circuit Current ◽  
Disulfonic Acid ◽  
Intestinal Epithelia ◽  
Mucosal Side

AbstractThe intestine of marine teleosts secretes HCO3- into the lumen and precipitates Ca2+ and Mg2+ in the imbibed seawater as carbonates to decrease luminal fluid osmolality and facilitate water absorption. However, reports on studies on the hormonal regulation of HCO3- secretion are just emerging. Here, we showed that guanylin (GN) applied to the mucosal side of intestinal epithelia increased HCO3- secretion in seawater-acclimated eels. The effect of GN on HCO3- secretion was slower than that on the short-circuit current, and the time-course of the GN effect was similar to that of bumetanide. Mucosal bumetanide and serosal 4,4’-dinitrostilbene-2,2’-disulfonic acid (DNDS) inhibited the GN effect, suggesting an involvement of apical Na+-K+-2Cl- cotransporter (NKCC2) and basolateral Cl-/HCO3- exchanger (AE)/Na+-HCO3- cotransporter (NBC) in the GN effect. However, mucosal DNDS and diphenylamine-2-carboxylic acid (DPC) failed to inhibit the GN effect, showing that apical AE and Cl- channel are not involved. To identify molecular species of possible transporters involved in the GN effect, we performed RNA-seq analyses followed by quantitative real-time PCR after transfer of eels to seawater. Among the genes upregulated after seawater transfer, those of Slc26a3a, b (DRAa, b) and Slc26a6a, c (Pat-1a, c) on the apical membrane of the intestinal epithelial cells, and those of Sls4a4a (NBCe1a), Slc4a7 (NBCn1), Slc4a10a (NBCn2a) and Slc26a1 (Sat-1) on the basolateral membrane were candidate transporters involved in HCO3- secretion. Judging from the slow effect of GN, we suggest that GN inhibits NKCC2b on the apical membrane and decreases cytosolic Cl- and Na+, which then activates apical DNDS-insensitive DRAa, b and basolateral DNDS-sensitive NBCela, n1, n2a to enhance transcellular HCO3- flux across the intestinal epithelia of seawater-acclimated eels.

scholarly journals Amiloride-sensitive trypsinization of apical sodium channels. Analysis of hormonal regulation of sodium transport in toad bladder.

1983 ◽  
Vol 81 (6) ◽  
pp. 785-803 ◽  
Author(s):  
H Garty ◽  
I S Edelman
Keyword(s):  
Hormonal Regulation ◽  
Apical Membrane ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Toad Urinary Bladder ◽  
Apical Surface ◽  
Na Channels ◽  
Na Transport ◽  
Na Permeability ◽  
Trypsin Inhibition

Incubation of the mucosal surface of the toad urinary bladder with trypsin (1 mg/ml) irreversibly decreased the short-circuit current to 50% of the initial value. This decrease was accompanied by a proportionate decrease in apical Na permeability, estimated from the change in amiloride-sensitive resistance in depolarized preparations. In contrast, the paracellular resistance was unaffected by trypsinization. Amiloride, a specific blocker of the apical Na channels, prevented inactivation by trypsin. Inhibition of Na transport by substitution of mucosal Na, however, had no effect on the response to trypsin. Trypsinization of the apical membrane was also used to study regulation of Na transport by anti-diuretic hormone (ADH) and aldosterone. Prior exposure of the apical surface to trypsin did not reduce the response to ADH, which indicates that the ADH-induced Na channels were inaccessible to trypsin before addition of the hormone. On the other hand, stimulation of short-circuit current by aldosterone or pyruvate (added to substrate-depleted, aldosterone-repleted bladders) was substantially reduced by prior trypsinization of the apical surface. Thus, the increase in apical Na permeability elicited by aldosterone or substrate involves activation of Na channels that are continuously present in the apical membrane in nonconductive but trypsin-sensitive forms.

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