Cloning and induction by low NaCl intake of avian intestine Na+ channel subunits

The alpha-subunit of the highly Na(+)-selective amiloride-blockable channel (ENaC) was cloned from chicken lower intestine. The deduced amino acid sequence of the avian clone exhibits -60% identity to the previously cloned mammalian and amphibian alpha-subunits. It also maintains the same hydropathy profile and structural motifs. These include two transmembrane domains separated by a large extracellular loop, four extracellular N-glycosylation sites, a cysteine-rich box in the extracellular domain, and a proline-rich stretch at the carboxy terminus. Xenopus oocytes injected with cRNA transcribed from this clone express a small amiloride-blockable Na+ conductance. Degenerate primers have been used to amplify two other related products. Sequence homology indicates that one of them is the beta-subunit, whereas the other appears to represent a closely related but different transcript. Regulation of the mRNA corresponding to these clones was examined in chickens fed normal and low-NaCl rations. The low-salt di...