Deletion of alpha-subunit exon 11 of the epithelial Na+ channel reveals a regulatory module

作者：Chen Jingxin; Kleyman Thomas R^*; Sheng Shaohu

来源：American Journal of Physiology - Renal Fluid and Electrolyte Physiology, 2014, 306(5): F561-F567.

DOI：10.1152/ajprenal.00587.2013

• epithelial Na+ channel
• exon
• domain
• open probability
• self-inhibition

Epithelial Na+ channel (ENaC) subunits (alpha, beta, and gamma) found in functional complexes are translated from mature mRNAs that are similarly processed by the inclusion of 13 canonical exons. We examined whether individual exons 3-12, encoding the large extracellular domain, are required for functional channel expression. Human ENaCs with an in-frame deletion of a single alpha-subunit exon were expressed in Xenopus oocytes, and their functional properties were examined by two-electrode voltage clamp. With the exception of exon 11, deletion of an individual exon eliminated channel activity. Channels lacking alpha-subunit exon 11 were hyperactive. Oocytes expressing this mutant exhibited fourfold greater amiloride-sensitive whole cell currents than cells expressing wild-type channels. A parallel fivefold increase in channel open probability was observed with channels lacking alpha-subunit exon 11. These mutant channels also exhibited a lost of Na+ self-inhibition, whereas we found similar levels of surface expression of mutant and wild-type channels. In contrast, in-frame deletions of exon 11 from either the beta- or gamma-subunit led to a significant loss of channel activity, in association with a marked decrease in surface expression. Our results suggest that exon 11 within the three human ENaC genes encodes structurally homologous yet functionally diverse domains and that exon 11 in the alpha-subunit encodes a module that regulates channel gating.

• 出版日期2014-3