Influenza virus M2 protein inhibits epithelial sodium channels by increasing reactive oxygen species.
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.
Lazrak
Ahmed
A
Department of Anesthesiology, Schools of Medicine and Public Health, University of Alabama at Birmingham, Birmingham, Alabama, USA.
Iles
Karen E
KE
Liu
Gang
G
Noah
Diana L
DL
Noah
James W
JW
Matalon
Sadis
S
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D062686:Epithelial Sodium Channel Blockers; D006801:Humans; D009865:Oocytes / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014162:Transfection; D014763:Viral Matrix Proteins / Q000502:physiology*; D014982:Xenopus laevis; D000086082:Viroporin Proteins
D000584:Amiloride; D062686:Epithelial Sodium Channel Blockers; D011493:Protein Kinase C; D017382:Reactive Oxygen Species; D014763:Viral Matrix Proteins; C488937:M2 protein, Influenza A virus; D000086082:Viroporin Proteins