AJP - Lung Cellular and Molecular Physiology, Vol 266, Issue 6 728-L734, Copyright © 1994 by American Physiological Society
Cloning, expression, and tissue distribution of a human amiloride-sensitive Na+ channel
F. J. McDonald, P. M. Snyder, P. B. McCray Jr and M. J. Welsh
Howard Hughes Medical Institute, Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242.
Amiloride-sensitive Na+ channels control, in part, fluid and electrolyte
transport across epithelia in many organs. In the lung, they control the
quantity and composition of the respiratory tract fluid and play a key role
in the transition from a fluid-filled lung at the time of birth. Their
function may also be altered in a number of diseases. The recent
identification of an epithelial Na+ channel from rat colon allowed us to
use a probe from that sequence to clone an amiloride-sensitive Na+ channel
from human kidney, alpha hENaC. The cDNA had an open reading frame of 2,007
nucleotides and encoded a protein predicted to contain 669 amino acids. The
amino acid sequence of alpha hENaC was 83% identical to that of the rat.
The gene was mapped to chromosome 12 by polymerase chain reaction (PCR) of
somatic cell hybrids. Transcripts of alpha hENaC were detected in human
kidney, lung, liver, and pancreas. No message was detected in first- and
second-trimester human fetal lung, indicating that alpha hENaC expression
is developmentally regulated. In vitro transcription and translation of
alpha hENaC produced a 74-kDa protein and translation in the presence of
microsomal membranes produced a glycosylated 87-kDa protein. Expression of
alpha hENaC in Xenopus oocytes produced currents that were amiloride
sensitive and Na+ selective, properties consistent with the function of
epithelial Na+ channels in native tissues.
