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Cell surface expression and biosynthesis of epithelial Na+ channels
1Howard Hughes Medical Institute, Departments of Pediatrics, Internal Medicine, and Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, IA 52242, USA.
The Biochemical Journal
|December 8, 1998
Summary
The epithelial sodium channel (ENaC) complex subunits traffic to the cell surface and form detergent-insoluble complexes. These unique trafficking and biochemical characteristics are key to ENaC function and regulation.
Area of Science:
- Cell Biology
- Molecular Biology
- Physiology
Background:
- The epithelial sodium channel (ENaC) complex comprises alpha, beta, and gamma subunits.
- ENaC mutations are linked to Liddle's syndrome (hypertension) and pseudohypoaldosteronism type I (salt-wasting).
Purpose of the Study:
- To investigate the surface expression and biochemical properties of ENaC subunits.
- To understand the trafficking and complex formation of ENaC.
Main Methods:
- Surface biotinylation and protease sensitivity assays in COS-7 and HEK293 cells.
- Analysis of ENaC subunit glycosylation and detergent solubility.
- Studied wild-type and truncated ENaC subunits, including co-expression of all three subunits.
Main Results:
- Individual ENaC subunits traffic to the cell surface.
- ENaC subunits undergo deglycosylation before reaching the cell surface.
- ENaC subunits form detergent-insoluble complexes, even when cytoplasmic regions are removed.
- Co-expression of all three subunits results in the predominant formation of insoluble complexes.
Conclusions:
- ENaC subunits exhibit unique trafficking and biochemical properties.
- The formation of detergent-insoluble complexes is a key characteristic of ENaC.
- These findings provide insights into the post-translational modifications and assembly of ENaC.