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Originally published In Press as doi:10.1074/jbc.M212240200 on February 14, 2003
J. Biol. Chem., Vol. 278, Issue 17, 14669-14676, April 25, 2003
Cloning and Characterization of a Novel
Na+-dependent Glucose Transporter (NaGLT1) in
Rat Kidney*
Naoshi
Horiba,
Satohiro
Masuda,
Ayako
Takeuchi,
Daisuke
Takeuchi,
Masahiro
Okuda, and
Ken-ichi
Inui
From the Department of Pharmacy, Kyoto University Hospital, Faculty
of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan
To identify novel transporters in the kidney, we
have constructed an mRNA data base composed of 1000 overall clones
by random sequencing of a male rat kidney cDNA library. After a
BLAST search, ~40% of the clones were unknown and/or unannotated and
were screened by measuring the uptake of various compounds using
Xenopus oocytes. One clone stimulated the uptake of
-methyl-D-glucopyranoside and therefore was termed rat
Na+-dependent glucose transporter 1 (rNaGLT1).
The rNaGLT1 cDNA (2173 bp) has an open reading frame encoding a
484-amino acid protein, showing <22% homology to known SGLT and GLUT
glucose transporters. -Methyl-D-glucopyranoside uptake
by rNaGLT1 cRNA-injected oocytes showed saturability, with an apparent
Km of 3.7 mM and a coupling ratio of
1:1 with Na+. rNaGLT1 mRNA was expressed predominantly
in the kidney upon Northern blot analysis and reverse
transcription-PCR. Reverse transcription-PCR in microdissected nephron
segments revealed that rNaGLT1 mRNA was primarily localized in the
proximal tubules. A clear signal corresponding to rNaGLT1 protein was
recognized in the brush-border (but not basolateral) membrane fraction
by immunoblot analysis. The rNaGLT1 mRNA level in the kidney was significantly higher than rat SGLT1 and SGLT2 mRNA levels. These findings suggest that rNaGLT1 is a novel
Na+-dependent glucose transporter with low
substrate affinity that mediates tubular reabsorption of glucose.
*
This work was supported by Grant-in-aid for Research on
Human Genome, Tissue Engineering, and Food Biotechnology H12-Genome-019 from the Ministry of Health, Labor, and Welfare of Japan and by a
grant-in-aid for scientific research from the Ministry of Education, Culture, Sports, Science, and Technology of Japan.The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement" in
accordance with 18 U.S.C. Section
1734 solely to indicate this fact.
The nucleotide sequence(s) reported in this paper has been submitted to the GenBankTM/EBI Data Bank with accession number(s) AB089802.
To whom correspondence should be addressed. Tel.: 81-75-751-3577;
Fax: 81-75-751-4207; E-mail: inui@kuhp.kyoto-u.ac.jp.
Copyright © 2003 by The American Society for Biochemistry and Molecular Biology, Inc.

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