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Published on: September 1, 2015
Interaction between Epithelial Sodium Channel γ-Subunit and Claudin-8 Modulates Paracellular Sodium Permeability in
Ali Sassi1,2, Yubao Wang1,2, Alexandra Chassot1,2
1Department of Cellular Physiology and Metabolism, University of Geneva, University Medical Center, Geneva, Switzerland.
The gamma subunit of the epithelial sodium channel (ENaC) specifically regulates claudin-8 expression, controlling kidney paracellular permeability. This finding is crucial for understanding sodium reabsorption and preventing solute backflow in the renal collecting duct.
Area of Science:
- Renal physiology
- Epithelial biology
- Molecular mechanisms of transport
Background:
- Paracellular transport is crucial for ion reabsorption in the kidney, mediated by tight junctions.
- In the renal collecting duct, tight junctions coordinate with transcellular sodium reabsorption to prevent solute backflow.
- The transmembrane protein claudin-8 is a key component of tight junctions influencing paracellular permeability.
Purpose of the Study:
- To investigate the role of epithelial sodium channel (ENaC) subunits in regulating tight junction composition and paracellular permeability.
- To determine if ENaC subunits modulate the expression of claudin-8, a critical tight junction protein.
- To elucidate the specific ENaC subunit responsible for controlling claudin-8 expression and its impact on renal sodium transport.
Main Methods:
- Utilized cultured mouse cortical collecting duct cells to examine the effects of ENaC subunit overexpression and silencing on claudin-8 expression and paracellular permeability.
- Employed conditional kidney tubule-specific knockout mice lacking specific ENaC subunits to assess in vivo regulation of claudin-8.
- Manipulated claudin-8 expression directly to confirm its functional role in paracellular ion permeability.
Main Results:
- Specific overexpression or silencing of the ENaC gamma (γ)-subunit led to parallel changes in claudin-8 abundance.
- Increased claudin-8 expression reduced paracellular sodium permeability, while decreased expression had the opposite effect.
- Conditional knockout of the ENaC γ-subunit in kidney tubules confirmed reduced claudin-8 expression, whereas α- and β-ENaC knockouts showed no effect on claudin-8.
Conclusions:
- Demonstrated a specific coupling between the ENaC γ-subunit and claudin-8 expression in the renal collecting duct.
- This regulatory mechanism is vital for preventing the backflow of reabsorbed solutes and water into the tubular lumen.
- The findings highlight a critical link between transcellular sodium transport and paracellular permeability in maintaining renal function.
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