Cloning and functional studies of splice variants of the alpha-subunit of the amiloride-sensitive Na+ channel.
The alpha-subunit of the amiloride-sensitive epithelial Na+ channel (alpha ENaC) is critical in forming an ion conductive pore in the membrane. We have identified the wild-type and three splice variants of the human alpha ENaC (h alpha ENaC) from the human lung cell line H441, using RT-PCR. These splice variants contain various structures in the extracellular domain, resulting in premature truncation (h alpha ENaCx), 19-amino acid deletion (h alpha ENaC-19), and 22-amino acid insertion (h alpha ENaC + 22). Wild-type h alpha ENaC and splice variants were functionally characterized in Xenopus oocytes by coexpression with hENaC beta- and gamma-subunits. Unlike wild-type h alpha ENaC, undetectable or substantially reduced amiloride-sensitive currents were observed in oocytes expressing these splice variants. Wild-type h alpha ENaC was the most abundantly expressed h alpha ENaC mRNA species in all tissues in which its expression was detected. These findings indicate that the extracellular domain is important to generate structural and functional diversity of h alpha ENaC and that alternative splicing may play a role in regulating hENaC activity.
Tucker
J K
JK
Department of Medicine, University of Alabama, Birmingham 35294, USA.
Tamba
K
K
Lee
Y J
YJ
Shen
L L
LL
Warnock
D G
DG
Oh
Y
Y
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004274:DNA, Recombinant; D053503:Epithelial Sodium Channels; D005091:Exons / Q000235:genetics; D005260:Female; D014644:Genetic Variation / Q000235:genetics*; D006801:Humans; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D015222:Sodium Channels / Q000235:genetics*; D014982:Xenopus laevis
D004274:DNA, Recombinant; D053503:Epithelial Sodium Channels; D015222:Sodium Channels