The highly selective, low conductance, epithelial sodium channel of
xenopus laevis a6 kidney cells.
Puoti, Alessandro, Anne May, Cecilia M. Canessa, Jean-Daniel
Horisberger, Laurent Schild, and Bernard C. Rossier.
Institut de Pharmacologie et de Toxicologie de l'Universit[acute]e, Rue du
Bugnon 27, CH-1005 Lausanne, Switzerland
APStracts 2:0097C, 1995.
In sodium reabsorbing tight epithelia, the rate limiting step for
sodium transport is the highly selective, low conductance, amiloride
-sensitive epithelial sodium channel (Type 1 ENaC). In rat distal
colon, Type 1 ENaC is made of three homologous subunits. The aim of
this study was to identify the corresponding genes of the renal
channel from the kidney-derived A6 cell line of Xenopus laevis. Three
homologous subunits were identified and coexpressed in the Xenopus
oocyte system. The reconstituted channel had all the characteristics
of the native Type 1 ENaC described in A6 cells: i) high selectivity
ii), low single channel conductance, iii) slow gating kinetics and
iv) high affinity for amiloride Transcripts for [alpha], [beta], [gamma]
xENaC were detected in A6 kidney cells, Xenopus kidney, lung and to a
lesser extent in stomach and skin. Each subunit of the Xenopus
epithelial Na channel (xENaC) shares about 60% overall identity with
the corresponding rat homologue ([alpha], [beta] and [gamma] rENaC). Our
data suggest that the triplication of the ENaC subunits occurred
before the divergence between mammalian and amphibian lineages.
Received 4 January 1995; accepted in final form 13 January 1995.
APS Manuscript Number C7-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 28 February 1995.