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XB-ART-40027
FASEB J 2009 Nov 01;2311:3829-42. doi: 10.1096/fj.09-135590.
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Influenza virus M2 protein inhibits epithelial sodium channels by increasing reactive oxygen species.

Lazrak A, Iles KE, Liu G, Noah DL, Noah JW, Matalon S.


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The mechanisms by which replicating influenza viruses decrease the expression and function of amiloride-sensitive epithelial sodium channels (ENaCs) have not been elucidated. We show that expression of M2, a transmembrane influenza protein, decreases ENaC membrane levels and amiloride-sensitive currents in both Xenopus oocytes, injected with human alpha-, beta-, and gamma-ENaCs, and human airway cells (H441 and A549), which express native ENaCs. Deletion of a 10-aa region within the M2 C terminus prevented 70% of this effect. The M2 ENaC down-regulation occurred at normal pH and was prevented by MG-132, a proteasome and lysosome inhibitor. M2 had no effect on Liddle ENaCs, which have decreased affinity for Nedd4-2. H441 and A549 cells transfected with M2 showed higher levels of reactive oxygen species, as shown by the activation of redox-sensitive dyes. Pretreatment with glutathione ester, which increases intracellular reduced thiol concentrations, or protein kinase C (PKC) inhibitors prevented the deleterious effects of M2 on ENaCs. The data suggest that M2 protein increases steady-state concentrations of reactive oxygen intermediates that simulate PKC and decrease ENaCs by enhancing endocytosis and its subsequent destruction by the proteasome. These novel findings suggest a mechanism for the influenza-induced rhinorrhea and life-threatening alveolar edema in humans.

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Species referenced: Xenopus laevis
Genes referenced: nedd4 nedd4l

References [+] :
Abriel, Defective regulation of the epithelial Na+ channel by Nedd4 in Liddle's syndrome. 1999, Pubmed, Xenbase