Acute Inhibition of the Epithelial Sodium Channel

Acute Inhibition of the Epithelial Sodium Channel

Bibliographic Details
Main Author: Falin, Rebecca A.
Language:English
Published: Case Western Reserve University School of Graduate Studies / OhioLINK 2008
Subjects:
ENaC beta
Epidermal Growth Factor
Ubiquitin
ERK MAP Kinases
Kidney Collecting Duct
Online Access:http://rave.ohiolink.edu/etdc/view?acc_num=case1190724697
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spelling ndltd-OhioLink-oai-etd.ohiolink.edu-case11907246972021-08-03T05:32:35Z Acute Inhibition of the Epithelial Sodium Channel Falin, Rebecca A. ENaC beta Epidermal Growth Factor Ubiquitin ERK MAP Kinases Kidney Collecting Duct <p>The epithelial sodium channel (ENaC) is expressed in a variety of tissues, including the renal collecting duct, where it constitutes the rate-limiting step for sodium reabsorption. First, the ERK1/2-mediated down-regulation of ENaC was characterized in primary and immortalized renal collecting duct cells (mCT12). Addition of epidermal growth factor (EGF) to polarized monolayers reduced amiloride-sensitive short-circuit current (ISC) by 15-25%.</p> <p>Exposure of mCT12 cells to EGF caused an increase in phosphorylation of ERK1/2; pretreatment of monolayers with a MEK inhibitor prevented this phosphorylation and significantly reduced EGF-induced inhibition of amiloride-sensitive ISC. The results of these studies demonstrate that acute inhibition of ISC by EGF involves ERK1/2 activation. p>Liddle's syndrome is caused by gain-of-function mutations in the beta- and gamma-subunits of ENaC, resulting in enhanced Na+ reabsorption and hypertension. In the second part of this study the effect of EGF on sodium absorption in primary renal collecting duct cells derived from a Liddle's mouse model was evaluated. It was found that EGF inhibited ISC by 24+/-5% in wild-type cells but only by 6+/-3% in homozygous mutant cells. EGF-induced ERK1/2 phosphorylation was similar in +/+ and L/L cells, and prolonged exposure to EGF decreased ENaC expression by ~50% in both. Acute inhibition of ENaC activity by EGF requires an intact beta-ENaC C-terminus, whereas EGF-induced down-regulation of ENaC expression does not.</p> <p>Finally, in order to elucidate the role of specific regions of the beta-ENaC C-terminus, MDCK cell lines expressing beta-ENaC with mutations of the PY motif, ERK phosphorylation site, and C-terminus truncation were created. All mutants exhibited significant attenuation of EGF-induced inhibition of sodium current. In MDCK cells with wild-type beta-ENaC, EGF-induced inhibition of ISC (<30min) was fully reversed by exposure to an ERK kinase inhibitor and occurred with no change in ENaC surface expression, indicative of an effect on channel open probability (Po). At later times (>30min), EGF-induced inhibition of ISC was not reversed by an ERK kinase inhibitor and was accompanied by a decrease in ENaC surface expression. These results are consistent with a reversible ERK-mediated decrease in ENaC Po followed by an irreversible retrieval of sodium channels from the apical membrane.</p> 2008 English text Case Western Reserve University School of Graduate Studies / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=case1190724697 http://rave.ohiolink.edu/etdc/view?acc_num=case1190724697 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.
collection NDLTD
language English
sources NDLTD
topic ENaC beta
Epidermal Growth Factor
Ubiquitin
ERK MAP Kinases
Kidney Collecting Duct
spellingShingle ENaC beta
Epidermal Growth Factor
Ubiquitin
ERK MAP Kinases
Kidney Collecting Duct
Falin, Rebecca A.
Acute Inhibition of the Epithelial Sodium Channel
author Falin, Rebecca A.
author_facet Falin, Rebecca A.
author_sort Falin, Rebecca A.
title Acute Inhibition of the Epithelial Sodium Channel
title_short Acute Inhibition of the Epithelial Sodium Channel
title_full Acute Inhibition of the Epithelial Sodium Channel
title_fullStr Acute Inhibition of the Epithelial Sodium Channel
title_full_unstemmed Acute Inhibition of the Epithelial Sodium Channel
title_sort acute inhibition of the epithelial sodium channel
publisher Case Western Reserve University School of Graduate Studies / OhioLINK
publishDate 2008
url http://rave.ohiolink.edu/etdc/view?acc_num=case1190724697
work_keys_str_mv AT falinrebeccaa acuteinhibitionoftheepithelialsodiumchannel
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