AJP - Cell Physiology, Vol 259, Issue 4 C605-C610, Copyright © 1990 by American Physiological Society
Sequence homologies among intestinal and renal Na+/glucose cotransporters
M. J. Coady, A. M. Pajor and E. M. Wright
Department of Physiology, University of California, School of Medicine, Los Angeles 90024-1751.
Sodium-dependent glucose transport occurs in the intestine and kidney of
most animal species. The cDNA encoding the Na+/glucose cotransporter from
rabbit jejunum was used to examine the distribution of homologous mRNA in
other rabbit tissues and in the intestines of other species. Northern blots
of mRNA extracted from various tissues were probed with radiolabeled cDNA
of the cloned rabbit transporter. The probe hybridized with mRNA of
approximately 2.2 kb from rabbit jejunum, renal cortex, and renal medulla,
indicating that related mRNA of the same size is found in these tissues.
With the use of the same cDNA probe, a 1.6-kb partial-length clone encoding
484 amino acids was isolated from a rabbit renal cortex cDNA library. There
was greater than 99% identity between the cDNA sequences, and 100% identity
between the amino acid sequences, of the renal clone and the rabbit
intestinal Na+/glucose cotransporter. The 2.2-kb transcript was seen in
mRNA from duodenum, jejunum, and ileum, with a distribution that matched
the Na+/glucose transport capacity in these tissues. A faint signal at 2.2
kb was also seen in colon mRNA. There was no detectable hybridization to
blots of stomach and heart mRNA. The rabbit probe also hybridized to
intestinal mRNA from a number of species from trout to humans. We conclude
that a Na+/glucose cotransporter of rabbit renal cortex is very similar to
that of the intestine and that the intestinal transporter has been
conserved during evolution.
