Cloning of the cDNa for a Na+/myo-inositol cotransporter, a hypertonicity stress protein.
Kidney medullary cells in situ, as well as kidney-derived Madin-Darby canine kidney (MDCK) cells accumulate nonperturbing, small organic solutes (osmolytes), including myo-inositol, when bathed in hypertonic media. Accumulation of osmolytes balances the osmolality of extracellular fluid without raising intracellular salts that would perturb cellular functions. In hypertonic media, increased myo-inositol accumulation is the result of increased activity of a Na+/myo-inositol cotransporter. We have isolated a cDNA encoding a Na+/myo-inositol cotransporter from MDCK cells using expression in Xenopus oocytes. The cDNA sequence predicts a protein of 718 amino acids with a significant amino acid sequence similarity to the Na+/D-glucose cotransporters of absorbing epithelia. Transporter mRNA is present in kidney and brain and is markedly induced in MDCK cells by medium hypertonicity, demonstrating that adaptation to hypertonic stress involves up-regulation of transporter mRNA accumulation.
Division of Nephrology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205-2196.
H M
HM
Kwon
A
A
Yamauchi
S
S
Uchida
A S
AS
Preston
A
A
Garcia-Perez
M B
MB
Burg
J S
JS
Handler
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D002460:Cell Line; D003001:Cloning, Molecular / Q000379:methods; D004247:DNA / Q000032:analysis / Q000235:genetics*; D005260:Female; D015723:Gene Library; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D007294:Inositol / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism; D007700:Kinetics; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D011061:Poly A / Q000235:genetics; D011487:Protein Conformation; D012313:RNA / Q000235:genetics; D012333:RNA, Messenger; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D027981:Symporters; D014158:Transcription, Genetic; D014982:Xenopus laevis
D002352:Carrier Proteins; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D027981:Symporters; C073884:SLC5A3 protein, human; D011061:Poly A; D007294:Inositol; D012313:RNA; D004247:DNA