Mouse kidney expresses mRNA of four highly related sodium-glucose cotransporters: regulation by cadmium.
BACKGROUND
To study the molecular mechanism responsible for cadmium-induced Fanconi syndrome, an in vitro mouse model has been used. We have previously shown that exposure of primary cultures of kidney cortical cells to micromolar concentrations of cadmium inhibited uptake of the glucose analog, [14C] methyl alpha-d-glucopyranoside (AMG) (261 mCi/mmol, NEN), and decreased mRNA levels of two kidney sodium-glucose cotransporters (SGLTs), SGLT1 and SGLT2. We also isolated partial cDNA of another member of the SGLT family, SGLT3-b, from cultured kidney cells and observed that cadmium exposure increased the abundance of its mRNA. In this study, we investigated the effect of cadmium on the second mouse kidney SGLT3 isoform, SGLT3-a. We also examined which SGLTs were transcribed in vivo.


METHODS
Cadmium was added to the confluent primary cultures of kidney cortical cells at concentrations of 5, 7.5, and 10 micromol/L. After 24 hours, uptake of [14C]AMG was measured and total RNA was extracted for semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) of SGLT3-a. Also, cDNA from whole kidneys of mice was used in PCR with primers specific for each SGLT. A partial cDNA sequence of SGLT3-a and the full-length cDNA sequence of SGLT3-b were obtained from their respective PCR clones.


RESULTS
Exposure of cortical cells to 5 micromol/L cadmium increased SGLT3-a mRNA level 3.4- +/- 0.78-fold (mean +/- SEM, P < 0.03, N = 5). mRNAs of SGLT1, SGLT2, SGLT3-a, and SGLT3-b were simultaneously present in cDNA samples from whole kidneys of mice. SGLT3-b cDNA sequence was revised from its predicted sequence to encode a 660 amino acid protein.


CONCLUSIONS
Reabsorption of glucose in mouse kidney may involve four SGLTs. Cadmium affects mRNA expression of all four SGLTs in vitro.
Tabatabai
Niloofar M
NM
Department of Chemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, USA. niloofar@uwm.edu
Blumenthal
Samuel S
SS
Lewand
Donna L
DL
Petering
David H
DH
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002104:Cadmium / Q000494:pharmacology; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000235:genetics; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000235:genetics*; D020033:Protein Isoforms / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism*; D051247:Sodium-Glucose Transport Proteins; D051269:Sodium-Glucose Transporter 1; D051297:Sodium-Glucose Transporter 2
D018076:DNA, Complementary; D008562:Membrane Glycoproteins; D009004:Monosaccharide Transport Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; C495675:Slc5a1 protein, mouse; C490299:Slc5a2 protein, mouse; C490297:Slc5a4b protein, mouse; D051247:Sodium-Glucose Transport Proteins; D051269:Sodium-Glucose Transporter 1; D051297:Sodium-Glucose Transporter 2; D002104:Cadmium