Gene expression of taurine transporter and taurine biosynthetic enzymes in hyperosmotic states: a comparative study with the expression of the genes involved in the accumulation of other osmolytes.

Abstract

Our results show that the gene expression of taurine transporter and taurine biosynthetic enzymes cysteine dioxygenase and cysteine sulfinate decarboxylase can be upregulated by hyperosmolarity. This finding strongly suggests that these three genes possess in their 5′ flanking region the consensus osmotic responsive element previously identified as necessary for the hyperosmolarity-induced upregulation of the genes, aldose reductase, myo-inositol transporter and betaine transporter involved in the accumulation of the osmolytes, sorbitol, myo-inositol and betaine. Although all genes involved in the accumulation of the various osmolytes can possibly be upregulated by hyperosmolarity, the actual pattern and time-course of their respective upregulations differ markedly in cells or tissues exposed to the same hyperosmotic conditions. This observation clearly indicates that there exist other factors which can selectively prevent the upregulation of these genes by hypertonicity.