[HTML][HTML] The epithelial sodium channel (ENaC) establishes a trafficking vesicle pool responsible for its regulation

RS Edinger, CA Bertrand, C Rondandino, GA Apodaca… - 2012 - journals.plos.org
RS Edinger, CA Bertrand, C Rondandino, GA Apodaca, JP Johnson, MB Butterworth
2012journals.plos.org
The epithelial sodium channel (ENaC) is the rate-limiting step for sodium reabsorption
across tight epithelia. Cyclic-AMP (cAMP) stimulation promotes ENaC trafficking to the apical
surface to increase channel number and transcellular Na+ transport. Removal of
corticosteroid supplementation in a cultured cortical collecting duct cell line reduced ENaC
expression. Concurrently, the number of vesicles trafficked in response to cAMP stimulation,
as measured by a change in membrane capacitance, also decreased. Stimulation with …
The epithelial sodium channel (ENaC) is the rate-limiting step for sodium reabsorption across tight epithelia. Cyclic-AMP (cAMP) stimulation promotes ENaC trafficking to the apical surface to increase channel number and transcellular Na+ transport. Removal of corticosteroid supplementation in a cultured cortical collecting duct cell line reduced ENaC expression. Concurrently, the number of vesicles trafficked in response to cAMP stimulation, as measured by a change in membrane capacitance, also decreased. Stimulation with aldosterone restored both the basal and cAMP-stimulated ENaC activity and increased the number of exocytosed vesicles. Knocking down ENaC directly decreased both the cAMP-stimulated short-circuit current and capacitance response in the presence of aldosterone. However, constitutive apical recycling of the Immunoglobulin A receptor was unaffected by alterations in ENaC expression or trafficking. Fischer Rat Thyroid cells, transfected with α,β,γ-mENaC had a significantly greater membrane capacitance response to cAMP stimulation compared to non-ENaC controls. Finally, immunofluorescent labeling and quantitation revealed a smaller number of vesicles in cells where ENaC expression was reduced. These findings indicate that ENaC is not a passive passenger in regulated epithelial vesicle trafficking, but plays a role in establishing and maintaining the pool of vesicles that respond to cAMP stimulation.
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