Protease modulation of the activity of the epithelial sodium channel expressed in Xenopus oocytes.

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Serval ID
serval:BIB_DF7F00FCEDFD
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Protease modulation of the activity of the epithelial sodium channel expressed in Xenopus oocytes.
Journal
Journal of General Physiology
Author(s)
Chraïbi A., Vallet V., Firsov D., Hess S.K., Horisberger J.D.
ISSN
0022-1295 (Print)
ISSN-L
0022-1295
Publication state
Published
Issued date
1998
Volume
111
Number
1
Pages
127-138
Language
english
Abstract
We have investigated the effect of extracellular proteases on the amiloride-sensitive Na+ current (INa) in Xenopus oocytes expressing the three subunits alpha, beta, and gamma of the rat or Xenopus epithelial Na+ channel (ENaC). Low concentrations of trypsin (2 microg/ml) induced a large increase of INa within a few minutes, an effect that was fully prevented by soybean trypsin inhibitor, but not by amiloride. A similar effect was observed with chymotrypsin, but not with kallikrein. The trypsin-induced increase of INa was observed with Xenopus and rat ENaC, and was very large (approximately 20-fold) with the channel obtained by coexpression of the alpha subunit of Xenopus ENaC with the beta and gamma subunits of rat ENaC. The effect of trypsin was selective for ENaC, as shown by the absence of effect on the current due to expression of the K+ channel ROMK2. The effect of trypsin was not prevented by intracellular injection of EGTA nor by pretreatment with GTP-gammaS, suggesting that this effect was not mediated by G proteins. Measurement of the channel protein expression at the oocyte surface by antibody binding to a FLAG epitope showed that the effect of trypsin was not accompanied by an increase in the channel protein density, indicating that proteolysis modified the activity of the channel present at the oocyte surface rather than the cell surface expression. At the single channel level, in the cell-attached mode, more active channels were observed in the patch when trypsin was present in the pipette, while no change in channel activity could be detected when trypsin was added to the bath solution around the patch pipette. We conclude that extracellular proteases are able to increase the open probability of the epithelial sodium channel by an effect that does not occur through activation of a G protein-coupled receptor, but rather through proteolysis of a protein that is either a constitutive part of the channel itself or closely associated with it.
Keywords
Amiloride/pharmacology, Animals, Calcium/physiology, Chymotrypsin/pharmacology, Diuretics/pharmacology, Epinephrine/pharmacology, Epithelial Cells/chemistry, GTP-Binding Proteins/metabolism, Gene Expression, Guanosine 5'-O-(3-Thiotriphosphate)/pharmacology, Oocytes/chemistry, Oocytes/drug effects, Patch-Clamp Techniques, Rats, Second Messenger Systems/drug effects, Second Messenger Systems/physiology, Sodium Channels/genetics, Sodium Channels/metabolism, Sympathomimetics/pharmacology, Trypsin/pharmacology, Xenopus
Pubmed
Web of science
Open Access
Yes
Create date
24/01/2008 12:32
Last modification date
20/08/2019 16:03
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