Glutathione disulfide regulation of δ‐ENaC subunit may play an important role in renal injury

Abstract

Renal handling of Na+ and water is significantly compromised in renal injury and disease. Epithelial Na+ Channel (ENaC) dysfunction has been implicated in the pathogenesis of renal injury/disease because it is responsible for generating the osmotic gradient needed for net solute transport across the renal epithelium. ENaC is a trimeric structure made up of α or δ, β, and γ subunits. Recent studies have suggested a link between ENaC dysfunction and oxidative stress in renal injury/disease, however, the precise mechanisms responsible for progression of renal disorders remain unclear. Since δ-ENaC subunit is primate specific, we investigated the response of αβγ- and δβγ-ENaC under pro-oxidizing conditions as it may occur in renal patients (and not easily appreciated in pre-clinical animal models of renal disorder). Because δβγ-ENaC generate large conducting channels, we hypothesized that the δ-ENaC subunit plays a significant role in renal disorders. In order to test our hypothesis, we measured whole cell current (2 electrode voltage clamp) of heterologously expressed αβγ, δβγ, and αβγδ-ENaC cRNA in a Xenopus laevis oocyte model system. We modeled redox stress by perfusing oxidized glutathione (GSSG; 400μM) across the cell membrane during recordings. GSSG significantly decreased ENaC activity in oocytes expressing αβγ-ENaC (n=10; p<0.05). Conversely, GSSG significantly increased whole cell current by 38% in oocytes expressing δβγ-ENaC (n=12; p<0.05). Although whole cell current in βγ (only) injected oocytes were low, GSSG did not alter βγ transport. This suggests that δ-ENaC confers GSSG sensitivity in δβγ channels. Interestingly, when αβγδ cRNA was injected at equal ratios, GSSG significantly increased whole cell current by 65% in all 13 independent observations from 2 distinct batches of oocytes. Together, our results indicate that αβγ- and δβγ-ENaC are regulated differently under redox stress, and that the δ-ENaC subunit may play an important role in renal injury. Support or Funding Information This work was supported by NIH R01HL137033-01A1 awarded to MH. GSSG decreases αβγ-ENaC activity. GSSG increases δβγ-ENaC activity. GSSG increases whole cell current when αδβγ subunits are co-expressed. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.