Oxidized Glutathione Increases Delta-Subunit Expressing Epithelial Sodium Channel Activity in Oocytes.

Epithelial sodium channels (ENaC) are heterotrimeric structures, made up of α, β, and γ subunits, and play an important role in maintaining fluid homeostasis. When δ-ENaC subunits are expressed in place of (or in addition to) the α-ENaC subunit alongside β- and γ- subunits, fundamental changes in the biophysical properties of ENaC can be observed. Using human ENaC cRNA constructs and the oocyte expression system, we show that oxidized glutathione (GSSG) differently effects αβγ-ENaC and αβγ-ENaC current. GSSG (400 μM) significantly decreased normalized whole cell current in oocytes expressing αβγ-ENaC, and conversely increased whole cell current in δ1βγ-ENaC and δ2βγ-ENaC expressing oocytes. GSSG treatment increased current in oocytes expressing all four subunits. Western blot and PCR analysis show that human small airway epithelial cells (hSAEC) express canonical αβγ-subunits alongside δ-ENaC subunits. Differences in single channel responses to GSSG in hSAECs indicate that airway epithelia redox sensitivity may depend on whether δ- or α- subunits assemble in the membrane. analysis predict that six Cys amino acids in the δ-ENaC extracellular loop, and a single Cys in the N-terminal domain, are susceptible to post-translational modification by GSSG. Additional studies are needed to better understand the molecular regulation and pathophysiological roles of oxidized glutathione and δ-ENaC in lung disorders.