AJP - Cell Physiology, Vol 266, Issue 6 C1505-C1512, Copyright © 1994 by American Physiological Society
Isolation of a rat amiloride-binding protein cDNA clone: tissue distribution and regulation of expression
K. Verity and P. J. Fuller
Prince Henry's Institute for Medical Research at Monash Medical Centre, Clayton, Victoria, Australia.
Sodium transport across high-resistance epithelia involves both an apical
amiloride-sensitive sodium channel and the basal Na(+)-K(+)-ATPase pump.
Aldosterone regulates sodium transport by increasing the sodium
permeability of the sodium channels. To study further the regulation of
gene expression in sodium-transporting epithelia by corticosteroids, we
have cloned an amiloride-binding protein (ABP) cDNA from rat descending
colon and kidney. Identical 311 nucleotide cDNAs were amplified from both
rat descending colon and kidney, and the predicted amino acid sequence
exhibited 83% homology to the equivalent region of the human peptide
sequence. Use of this cDNA as a probe resulted in detection of a transcript
in both the small and large bowel, thymus, and seminal vesicle. The latter
tissue exhibited the highest level of rat ABP expression. Low to
undetectable levels of rat ABP were expressed in the descending colon and
kidney. No regulation of rat ABP by either class of corticosteroids was
observed. Levels of ABP were low at birth and increased gradually to adult
levels just before weaning in the bowel. The distribution of rat ABP is not
as would be predicted for an aldosterone-induced gene and is thus unlikely
to be a component of the amiloride-sensitive electrogenic sodium channel.
