Title: Expression of ENaC and other transport proteins in Xenopus oocytes is modulated by intracellular Na+
Authors: Kusche-Vihrog, Kristina *
Segal Stanciu, Andrei *
Grygorczyk, Ryszard
Bangel-Ruland, Nadine
Van Driessche, Willy
Weber, Wolf-Michael # ×
Issue Date: 2009
Publisher: S. Karger
Series Title: Cellular Physiology and Biochemistry vol:23 issue:1-3 pages:9-24
Abstract: The expression of the epithelial Na+ channel (ENaC) is tissue-specific and dependent on a variety of mediators and interacting proteins. Here we examined the role of intracellular Na+ ([Na+](i)) as a modulator of the expression of rat ENaC in Xenopus laevis oocytes. We manipulated [Na+](i) of ENaC-expressing oocytes in the range of 0-20 mM by incubating in extracellular solutions of different [Na+](o). Electrophysiological, protein biochemical and fluorescence optical methods were used to determine the effects of different [Na+]i on ENaC expression and membrane abundance. In voltage-clamp experiments we found that amiloride-sensitive ENaC current (Iami) and conductance (Gami) peak at a [Na+](i) of approximately 10 mM Na+, but were significantly reduced in 5 mM and 20 mM [Na+](i). Fluorescence intensity of EGFP-ENaC-expressing oocytes also followed a bell-shaped curve with a maximum at approximately 10 mM [Na+](i). In Western blot experiments with specific anti-ENaC antibodies the highest protein expression was found in ENaC-expressing oocytes with [Na+](i) of 10-15 mM. Since ENaC is also highly permeable for Li+, we incubated ENaC-expressing oocytes in different Li+ concentrations and found a peak of Iami and Gami with 5 mM Li+. The influence of [Na+](i) on the expression is not ENaC-specific, since expression of a Cl(-) channel (CFTR) and a Na+/glucose cotransporter (SGLT1) showed the same dependence on [Na+](i). We conclude that specific concentrations of Na+ and Li+ influence the expression and abundance of ENaC and other transport proteins in the plasma membrane in Xenopus laevis oocytes. Furthermore, we suggest the existence of a general mechanism dependent on monovalent cations that optimizes the expression of membrane proteins.
ISSN: 1015-8987
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Laboratory of Ion Channel Research (VIB-KU Leuven Center for Brain & Disease Research)
* (joint) first author
× corresponding author
# (joint) last author

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