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Syntaxin 1A regulates ENaC channel activity.
Steven B Condliffe1, Hui Zhang, Raymond A Frizzell
1Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15217, USA.
The Journal of Biological Chemistry
|January 3, 2004
Summary
Syntaxin-1A (S1A) rapidly reduces epithelial sodium channel (ENaC) open probability by altering channel gating. This complements S1A
Area of Science:
- Physiology
- Molecular Biology
- Cell Biology
Background:
- Epithelial sodium channel (ENaC) activity is crucial for Na(+) absorption.
- Syntaxin-1A (S1A) regulates ENaC trafficking, impacting channel number (N).
Purpose of the Study:
- To investigate if S1A also affects ENaC open probability (P(o)).
Main Methods:
- Xenopus oocyte expression system.
- Glutathione S-transferase (GST)-H3 S1A fusion protein injection.
- Whole-cell patch clamp electrophysiology.
- Cell-attached patch clamp recordings.
Main Results:
- GST-H3 S1A fusion protein inhibited Na(+) current (I(Na)) by 33% in a dose-dependent manner.
- GST-H3 S1A significantly decreased ENaC P(o) by 30% and prolonged mean closed time.
- S1A's effect on gating was independent of ENaC trafficking and did not affect constitutively open mutants.
Conclusions:
- S1A directly interacts with cell surface ENaC to decrease its open probability.
- S1A modulates ENaC gating, providing a rapid mechanism to control Na(+) entry.
- S1A has distinct effects on ENaC trafficking and gating, separable experimentally.