Dataset Information

The delta-subunit of the epithelial sodium channel (ENaC) enhances channel activity and alters proteolytic ENaC activation.

ABSTRACT: The epithelial sodium channel (ENaC) is probably a heterotrimer with three well characterized subunits (alphabetagamma). In humans an additional delta-subunit (delta-hENaC) exists but little is known about its function. Using the Xenopus laevis oocyte expression system, we compared the functional properties of alphabetagamma- and deltabetagamma-hENaC and investigated whether deltabetagamma-hENaC can be proteolytically activated. The amiloride-sensitive ENaC whole-cell current (DeltaI(ami)) was about 11-fold larger in oocytes expressing deltabetagamma-hENaC than in oocytes expressing alphabetagamma-hENaC. The 2-fold larger single-channel Na(+) conductance of deltabetagamma-hENaC cannot explain this difference. Using a chemiluminescence assay, we demonstrated that an increased channel surface expression is also not the cause. Thus, overall channel activity of deltabetagamma-hENaC must be higher than that of alphabetagamma-hENaC. Experiments exploiting the properties of the known betaS520C mutant ENaC confirmed this conclusion. Moreover, chymotrypsin had a reduced stimulatory effect on deltabetagamma-hENaC whole-cell currents compared with its effect on alphabetagamma-hENaC whole-cell currents (2-fold versus 5-fold). This suggests that the cell surface pool of so-called near-silent channels that can be proteolytically activated is smaller for deltabetagamma-hENaC than for alphabetagamma-hENaC. Proteolytic activation of deltabetagamma-hENaC was associated with the appearance of a delta-hENaC cleavage product at the cell surface. Finally, we demonstrated that a short inhibitory 13-mer peptide corresponding to a region of the extracellular loop of human alpha-ENaC inhibited DeltaI(ami) in oocytes expressing alphabetagamma-hENaC but not in those expressing deltabetagamma-hENaC. We conclude that the delta-subunit of ENaC alters proteolytic channel activation and enhances base-line channel activity.

SUBMITTER: Haerteis S

PROVIDER: S-EPMC2781449 | biostudies-literature | 2009 Oct

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

The delta-subunit of the epithelial sodium channel (ENaC) enhances channel activity and alters proteolytic ENaC activation.

Haerteis Silke S Krueger Bettina B Korbmacher Christoph C Rauh Robert R

The Journal of biological chemistry 20090828 42

The epithelial sodium channel (ENaC) is probably a heterotrimer with three well characterized subunits (alphabetagamma). In humans an additional delta-subunit (delta-hENaC) exists but little is known about its function. Using the Xenopus laevis oocyte expression system, we compared the functional properties of alphabetagamma- and deltabetagamma-hENaC and investigated whether deltabetagamma-hENaC can be proteolytically activated. The amiloride-sensitive ENaC whole-cell current (DeltaI(ami)) was a ...[more]

PMID: 19717556

Similar Datasets

Project description:BackgroundThe amiloride-sensitive Epithelial Sodium Channel (ENaC) is critical in maintaining Na+ balance, extracellular fluid volume and long term blood pressure control. ENaC is composed of three main subunits alpha, beta, & gamma. While alpha ENaC is critical for channel functionality, beta & gamma ENaC maximize channel function. To date, there are four alternatively spliced forms of the alpha subunit of ENaC (alpha ENaC-a, -b, -c, & -d) that have been published in rats, in addition to the major alpha ENaC transcript. While alpha ENaC-a, -c & -d transcripts are low abundance transcripts compared to full-length alpha ENaC, alpha ENaC-b is a higher abundance and salt-sensitive transcript compared to full-length alpha ENaC.Presentation of the hypothesisalpha ENaC-b protein, which is preferentially produced in Dahl R rats, to a greater extent on high salt diet, exerts a dominant negative effect on full-length alpha ENaC subunit by physically binding to and trapping full-length alpha ENaC subunit in the endoplasmic reticulum, and finally accelerating full-length alpha ENaC proteolytic degradation in a dose-dependent manner.Testing the hypothesis1) To examine the mRNA and protein abundance of alpha ENaC-b relative to alpha ENaC full-length in kidney, lung, and taste tissues of Dahl rats. 2) To compare the expression (mRNA and protein) of alpha ENaC-b in kidneys of Dahl S and R rats on regular and high salt diet. 3) To examine the putative binding of alpha ENaC-b proteins to full-length alpha ENaC in vitro and to determine the impact of such binding on full-length alpha ENaC expression in vitro.Implications of the hypothesisOur studies will be the first to demonstrate the over-expression of salt-sensitive alpha ENaC-b spliced form in kidney tissues of Dahl R rats at the expense of full-length alpha ENaC. The current proposal will provide highly novel insights into the putative mechanisms leading to ENaC hypoactivity in high-salt-fed Dahl R rats. Finally, findings from the present proposal will uncover a new mechanism by which alternative splicing may control the regulation of ENaC expression/function.

Dataset Information

The delta-subunit of the epithelial sodium channel (ENaC) enhances channel activity and alters proteolytic ENaC activation.

Publications

The delta-subunit of the epithelial sodium channel (ENaC) enhances channel activity and alters proteolytic ENaC activation.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets