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Kwon, H. Moo
Inflammation and Kidney Disorder Lab
Research Interests
  • TonEBP, Obesity, Cancer, Chronic inflammatory diseases, Brain disorder, Kidney disorders, Genomic instability

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Tyrosine kinase inhibitors and immunosuppressants perturb the myo-inositol but not the betaine cotransporter in isotonic and hypertonic MDCK cells

Cited 18 times inthomson ciCited 17 times inthomson ci
Title
Tyrosine kinase inhibitors and immunosuppressants perturb the myo-inositol but not the betaine cotransporter in isotonic and hypertonic MDCK cells
Author
Atta, MGDahl, SCKwon, H. MooHandler, JS
Keywords
Cell volume; Cotransport; Hypertonicity; Osmolytes; Protein phosphorylation; Transcription
Issue Date
199903
Publisher
NATURE PUBLISHING GROUP
Citation
KIDNEY INTERNATIONAL, v.55, no.3, pp.956 - 962
Abstract
Background. The sodium/myo-inositol cotransporter (SMIT) and the betaine cotransporter (BGT1) are essential for the accumulation of myo-inositol and betaine, and hence cell survival in a hypertonic environment. The underlying molecular mechanism involves an increase in transcription of the SMIT and BGT1 genes through binding of a trans-acting factor to enhancer elements in the 5' flanking region of both genes, resulting in increased mRNA abundance and increased activity of the cotransporters. Current evidence regarding transcriptional and post-transcriptional regulation indicates that both cotransporters are regulated in parallel. Methods. To investigate the signal transduction of hypertonic stress, we examined the effect of tyrosine kinase inhibitors and immunosuppressants on the hypertonicity-induced activity of the two cotransporters in Madin-Darby canine kidney (MDCK) cells. Results. None of the agents studied affected BGT1 activity in isotonic or hypertonic conditions. Treatment of MDCK cells with genistein, a tyrosine kinase inhibitor, increased SMIT activity in hypertonic but not isotonic conditions. The stimulation of SMIT by genistein was accompanied by a parallel increase in mRNA abundance. In contrast, treating cells with tyrphostin A23, another tyrosine kinase inhibitor, or cyclosporine A, an immunosuppressant, inhibited SMIT activity in hypertonic cells. FK506, another immunosuppressant, increased SMIT activity, but only in isotonic conditions. Conclusions. These results provide the first evidence of divergent regulatory pathways modulating SMIT and BGT activity.
URI
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DOI
http://dx.doi.org/10.1046/j.1523-1755.1999.055003956.x
ISSN
0085-2538
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