H2O2 regulates lung epithelial sodium channel (ENaC) via ubiquitin-like protein Nedd8.
Redundancies in both the ubiquitin and epithelial sodium transport pathways allude to their importance of proteolytic degradation and ion transport in maintaining normal cell function. The classical pathway implicated in ubiquitination of the epithelial sodium channel (ENaC) involves Nedd4-2 regulation of sodium channel subunit expression and has been studied extensively studied. However, less attention has been given to the role of the ubiquitin-like protein Nedd8. Here we show that Nedd8 plays an important role in the ubiquitination of ENaC in alveolar epithelial cells. We report that the Nedd8 pathway is redox-sensitive and that under oxidizing conditions Nedd8 conjugation to Cullin-1 is attenuated, resulting in greater surface expression of α-ENaC. This observation was confirmed in our electrophysiology studies in which we inhibited Nedd8-activating enzyme using MLN4924 (a specific Nedd8-activating enzyme inhibitor) and observed a marked increase in ENaC activity (measured as the product of the number of channels (N) and the open probability (Po) of a channel). These results suggest that ubiquitination of lung ENaC is redox-sensitive and may have significant implications for our understanding of the role of ENaC in pulmonary conditions where oxidative stress occurs, such as pulmonary edema and acute lung injury.
Nell Hodgson Woodruff School of Nursing, Emory University School of Medicine, Atlanta, Georgia 30322; Department of Physiology, Emory University School of Medicine, Atlanta, Georgia 30322.
Charles A
CA
Downs
Department of Physiology, Emory University School of Medicine, Atlanta, Georgia 30322.
Amrita
A
Kumar
Department of Physiology, Emory University School of Medicine, Atlanta, Georgia 30322; Department of Pediatrics Center for Developmental Lung Biology, Emory University School of Medicine, Atlanta, Georgia 30322.
Lisa H
LH
Kreiner
Department of Physiology, Emory University School of Medicine, Atlanta, Georgia 30322; Department of Pediatrics Center for Developmental Lung Biology, Emory University School of Medicine, Atlanta, Georgia 30322.
Nicholle M
NM
Johnson
Department of Physiology, Emory University School of Medicine, Atlanta, Georgia 30322; Department of Pediatrics Center for Developmental Lung Biology, Emory University School of Medicine, Atlanta, Georgia 30322. Electronic address: mhelms@emory.edu.
My N
MN
Helms
D056809:Alveolar Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D044842:Cullin Proteins / Q000378:metabolism; D003517:Cyclopentanes / Q000494:pharmacology; D053503:Epithelial Sodium Channels / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015870:Gene Expression; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008564:Membrane Potentials; D051379:Mice; D008810:Mice, Inbred C57BL; D000075687:NEDD8 Protein; D010084:Oxidation-Reduction; D018408:Patch-Clamp Techniques; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D044764:Ubiquitin-Activating Enzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D054875:Ubiquitination; D014452:Ubiquitins / Q000378:metabolism*; D015854:Up-Regulation
C100318:Cullin 1; D044842:Cullin Proteins; D003517:Cyclopentanes; D053503:Epithelial Sodium Channels; D000075687:NEDD8 Protein; C513172:Nedd8 protein, mouse; D011743:Pyrimidines; D014452:Ubiquitins; D006861:Hydrogen Peroxide; D044767:Ubiquitin-Protein Ligases; D044764:Ubiquitin-Activating Enzymes; C539933:pevonedistat