Cloning of the cDNa for a Na+/myo-inositol cotransporter, a hypertonicity stress protein

• Published in: The Journal of biological chemistry 1992-03, Vol.267 (9), p.6297-6301
• Main Authors: MOO KWON, H, YAMAUCHI, A, UCHIDA, S, PRESTON, A. S, GARCIA-PEREZ, A, BURG, M. B, HANDLER, J. S
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Animals; Base Sequence; Binding and carrier proteins; Biological and medical sciences; Carrier Proteins - genetics; Carrier Proteins - isolation & purification; Carrier Proteins - metabolism; Cell Line; Cloning, Molecular - methods; DNA - analysis; DNA - genetics; Female; Fundamental and applied biological sciences. Psychology; Gene Library; Heat-Shock Proteins - genetics; Heat-Shock Proteins - isolation & purification; Heat-Shock Proteins - metabolism; Inositol - metabolism; Kidney - metabolism; Kinetics; Membrane Proteins; Molecular Sequence Data; Oocytes - metabolism; Poly A - genetics; Protein Conformation; Proteins; Recombinant Proteins - isolation & purification; Recombinant Proteins - metabolism; RNA - genetics; RNA, Messenger; Sequence Homology, Nucleic Acid; Symporters; Transcription, Genetic; Xenopus laevis
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/s0021-9258(18)42695-6

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.