Aldosterone-mediated regulation of ENaC α, β, and γ subunit proteins in rat kidney

TLDR

Aldosterone stimulates sodium transport in the renal collecting duct by activating the epithelial sodium channel (ENaC). The study aimed to elucidate this effect by generating rabbit polyclonal antibodies against the three ENaC subunits and mapping their abundance and distribution in rat collecting duct principal cells. Using these antibodies, the authors quantified ENaC subunit levels and localization to assess aldosterone‑induced changes. Elevated aldosterone selectively increased alphaENaC protein, redistributed ENaC to the apical membrane, and shifted gammaENaC molecular weight, revealing heterogeneous quantitative and qualitative alterations that explain the enhanced sodium transport.

Abstract

Aldosterone stimulates sodium transport in the renal collecting duct by activating the epithelial sodium channel (ENaC). To investigate the basis of this effect, we have developed a novel set of rabbit polyclonal antibodies to the 3 subunits of ENaC and have determined the abundance and distribution of ENaC subunits in the principal cells of the rat renal collecting duct. Elevated circulating aldosterone (due to either dietary NaCl restriction or aldosterone infusion) markedly increased the abundance of alphaENaC protein without increasing the abundance of the beta and gamma subunits. Thus, alphaENaC is selectively induced by aldosterone. In addition, immunofluorescence immunolocalization showed a striking redistribution in ENaC labeling to the apical region of the collecting duct principal cells. Finally, aldosterone induced a shift in molecular weight of gammaENaC from 85 kDa to 70 kDa, consistent with physiological proteolytic clipping of the extracellular loop as postulated previously. Thus, at the protein level, the response of ENaC to aldosterone stimulation is heterogenous, with both quantitative and qualitative changes that can explain observed increases in ENaC-mediated sodium transport.