Cloning of a bovine renal epithelial Na+ channel subunit.
A bovine homologue of the rat and human epithelial Na+ channel subunits, alpha-rENaC and alpha-hENaC, was cloned. The cDNA clone, termed alpha-bENaC, was isolated from a bovine renal papillary collecting duct cDNA expression library. The bovine cDNA is 3,584 base pairs (bp) long, has an open reading frame of 2,094 bp encoding a 697-amino acid protein, and is 75-85% homologous to its rat and human counterparts. In vitro translation of the transcribed cRNA yields an 80-kDa polypeptide and one at 92 kDa in the presence of pancreatic microsomes. The clone exhibits consensus sequences for N-linked glycosylation and for phosphorylation by protein kinase C, but not for protein kinase A. After expression in Xenopus laevis oocytes, a small amiloride-sensitive Na+ conductance that exhibited inward rectification and a reversal potential greater than +30 mV, consistent with the predicted equilibrium potential for Na+, was identified. The expressed alpha-bENaC-associated Na+ current was not responsive to elevations in adenosine 3',5'-cyclic monophosphate but could be stimulated by phorbol 12-myristate 13-acetate, an activator of protein kinase C. alpha-bENaC also formed amiloride-sensitive chimeric channels when coexpressed with the rat beta- and gamma-ENaC subunits in Xenopus oocytes. alpha-bENaC therefore represents a novel isoform of a growing family of epithelial Na+ channels.
Fuller
C M
CM
Department of Physiology and Biophysics, University of Alabama at Birmingham 35294, USA.
Awayda
M S
MS
Arrate
M P
MP
Bradford
A L
AL
Morris
R G
RG
Canessa
C M
CM
Rossier
B C
BC
Benos
D J
DJ
D000595:Amino Acid Sequence; D000818:Animals; D016375:Antisense Elements (Genetics) / Q000235:genetics; D001483:Base Sequence; D015152:Blotting, Northern; D002417:Cattle; D003001:Cloning, Molecular; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007536:Isomerism; D007668:Kidney / Q000378:metabolism*; D015335:Molecular Probes / Q000235:genetics; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D014176:Protein Biosynthesis; D051381:Rats; D017386:Sequence Homology, Amino Acid; D015222:Sodium Channels / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D014982:Xenopus laevis
D016375:Antisense Elements (Genetics); D015335:Molecular Probes; D015222:Sodium Channels