Cloning of a bovine renal epithelial na+ channel subunit. Fuller, Catherine M., Mouhamed S. Awayda, M. Pia Arrate, Anne Lynn Bradford, Ryan G. Morris, Cecilia M. Canessa, Bernard C. Rossier, and Dale J. Benos. Department of Physiology and Biophysics, University of Alabama at Birmingham, Birmingham, Alabama 35294 and Institut de Pharmacologie et de Toxicologie de l'Universite de Lausanne, rue de Bugnon 27, CH -1005 Lausanne, Switzerland
APStracts 2:0159C, 1995.
A bovine homolog of the rat and human epithelial sodium 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 3584 bp long, has an open reading frame of 2094 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. Following expression in Xenopus 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 cAMP but could be stimulated by phorbol 12-myristate 13-acatate (PMA), an activator of protein kinase C. [alpha]bENaC also formed amiloride-sensitive chimeric channels when co-expressed with the rat [beta] and [tau] ENaC subunits in Xenopus oocytes. [alpha]bENaC therefore represents a novel isoform of a growing family of epithelial Na+ channels. 

Received 1 March 1995; accepted in final form 28 March 1995.
APS Manuscript Number C114-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 10 April 1995.