Cloning and expression of the beta- and gamma-subunits of the human epithelial sodium channel.
Amiloride-sensitive Na+ channels are an important component of the Na+ reabsorption pathway in a number of epithelia. Here we report the cloning and characterization of cDNAs encoding two subunits of the human kidney epithelial Na+ channel (beta- and gamma-hENaC). Their predicted amino acid sequences were highly homologous (83-85% identical) to the corresponding subunits reported from rat colon (beta- and gamma-rENaC). Both beta- and gamma-hENaC mapped to human chromosome 16. Northern blot analysis showed high expression of beta- and gamma-hENaC in kidney and lung and differential expression of the three subunits in other tissues. Coexpression of beta- and gamma-hENaC with alpha-hENaC in Xenopus oocytes produced Na+ channels with high selectivity for Na+ and high sensitivity to amiloride. In addition, human subunits were able to substitute for the corresponding rat subunits in forming functional Na+ channels, suggesting conservation of function and suggesting that differences in sequence do not disrupt interactions between subunits. These results suggest that human alpha-, beta-, and gamma-ENaC together form Na+ channels with properties that are similar to those observed in epithelia, and will allow further investigation into the role that these channels may play in human disease.
McDonald
F J
FJ
Department of Internal Medicine, Howard Hughes Medical Institute, University of Iowa College of Medicine, Iowa City 52242, USA.
Price
M P
MP
Snyder
P M
PM
Welsh
M J
MJ
D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D003001:Cloning, Molecular; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D015335:Molecular Probes / Q000235:genetics; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D015222:Sodium Channels / Q000235:genetics* / Q000378:metabolism*; D014981:Xenopus
D015335:Molecular Probes; D015222:Sodium Channels