An Alu cassette in the human epithelial sodium channel

Here, we report the presence of two splice variants of the human epithelial sodium channel alpha subunit (h alpha ENaC) containing Alu cassette, namely h alpha ENaC+22 and h alpha ENaC+Alu, in various tissues. Functional expression of these splice variants with hENaC beta and gamma subunits produced loss-of-channel activity in the Xenopus oocyte expression system. Interestingly, coexpression of h alpha ENaC+22 or h alpha ENaC+Alu, respectively, with wild type hENaC alpha, beta, and gamma subunits enhanced the expression of amiloride-sensitive current in oocytes. The presence of Alu sequences in the 3'-untranslated region of h gamma ENaC was also identified.