Dataset Information

Thumb domains of the three epithelial Na+ channel subunits have distinct functions.

ABSTRACT: The epithelial Na+ channel (ENaC) possesses a large extracellular domain formed by a ?-strand core enclosed by three peripheral ?-helical subdomains, which have been dubbed thumb, finger, and knuckle. Here we asked whether the ENaC thumb domains play specific roles in channel function. To this end, we examined the characteristics of channels lacking a thumb domain in an individual ENaC subunit (?, ?, or ?). Removing the ? subunit thumb domain had no effect on Na+ currents when expressed in Xenopus oocytes, but moderately reduced channel surface expression. In contrast, ENaCs lacking the ? or ? subunit thumb domain exhibited significantly reduced Na+ currents along with a large reduction in channel surface expression. Moreover, channels lacking an ? or ? thumb domain exhibited a diminished Na+ self-inhibition response, whereas this response was retained in channels lacking a ? thumb domain. In turn, deletion of the ? thumb domain had no effect on the degradation rate of the immature ? subunit as assessed by cycloheximide chase analysis. However, accelerated degradation of the immature ? subunit and mature ? subunit was observed when the ? or ? thumb domain was deleted, respectively. Our results suggest that the thumb domains in each ENaC subunit are required for optimal surface expression in oocytes and that the ? and ? thumb domains both have important roles in the channel's inhibitory response to external Na+ Our findings support the notion that the extracellular helical domains serve as functional modules that regulate ENaC biogenesis and activity.

SUBMITTER: Sheng S

PROVIDER: S-EPMC6231141 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Thumb domains of the three epithelial Na+ channel subunits have distinct functions.

Sheng Shaohu S Chen Jingxin J Mukherjee Anindit A Yates Megan E ME Buck Teresa M TM Brodsky Jeffrey L JL Tolino Michael A MA Hughey Rebecca P RP Kleyman Thomas R TR

The Journal of biological chemistry 20180918 45

The epithelial Na+ channel (ENaC) possesses a large extracellular domain formed by a β-strand core enclosed by three peripheral α-helical subdomains, which have been dubbed thumb, finger, and knuckle. Here we asked whether the ENaC thumb domains play specific roles in channel function. To this end, we examined the characteristics of channels lacking a thumb domain in an individual ENaC subunit (α, β, or γ). Removing the γ subunit thumb domain had no effect on Na+ currents w ...[more]

PMID: 30228189

Similar Datasets

Project description:Bile acids, originally known to emulsify dietary lipids, are now established signalling molecules that regulate physiological processes. Signalling targets several proteins that include the ion channels involved in regulating intestinal motility and bile viscosity. Studies show that bile acids regulate the epithelial sodium channel (ENaC) in cultured cell models and heterologous expression systems. ENaC plays both local and systemic roles in regulating extracellular fluids. Here we investigated whether bile acids regulate ENaC expressed in native tissues. We found that taurocholic acid and taurohyodeoxycholic acid regulated ENaC in both the distal nephron and distal colon. We also tested the hypothesis that regulation occurs through direct binding. Using photoaffinity labelling, we found evidence for specific binding to both the β and γ subunits of the channel. In functional experiments, we found that the α subunit was sufficient for regulation. We also found that regulation by at least one bile acid was voltage-sensitive, suggesting that one binding site may be closely associated with the pore-forming helices of the channel. Our data provide evidence that bile acids regulate ENaC by binding to multiple sites to influence the open probability of the channel. KEY POINTS: Recent studies have shown that bile acids regulate the epithelial sodium channel (ENaC) in vitro. Here we investigated whether bile acids regulate ENaC in native tissues and whether bile acids directly bind the channel. We found that bile acids regulate ENaC expressed in the mouse cortical collecting duct and mouse colon by modulating open probability. Photoaffinity labelling experiments showed specific binding to the β and γ subunits of the channel, while channels comprising only α subunits were sensitive to taurocholic acid in functional experiments using Xenopus oocytes. Taurocholic acid regulation of ENaC was voltage-dependent, providing evidence for binding to pore-forming helices. Our data indicate that bile acids are ENaC regulatory effectors that may have a role in the physiology and pathophysiology of several systems.

Dataset Information

Thumb domains of the three epithelial Na+ channel subunits have distinct functions.

Publications

Thumb domains of the three epithelial Na<sup>+</sup> channel subunits have distinct functions.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets