Downregulation of the taurine transporter TauT during hypo-osmotic stress in NIH3T3 mouse fibroblasts.
Bottom Line: Taurine influx is reduced following reduction in osmolarity, keeping the extracellular Na(+) concentration constant.TonEBP activity is unaltered, whereas TauT transcription as well as TauT activity are significantly reduced under hypo-osmotic conditions.Acute exposure to ROS reduces taurine uptake as a result of modulated TauT transport kinetics.
Affiliation: Department of Biology, Section of Cellular and Developmental Biology, University of Copenhagen, The August Krogh Building, Universitetsparken 13, 2100 Copenhagen Ø, Denmark.Show MeSH
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Mentions: Using NOX4-overexpressing cells, we tested whether ROS generated by NOX4 could affect TonEBP activity and TauT transcription. It is seen that the increase in TonEBP activity following hypertonic exposure in NOX4-overexpressing cells is comparable to that in native cells, whereas there is a significant decrease in TonEBP activity under hypo-osmotic conditions (4 h) (Fig. 3a). The significant reduction in TonEBP activity under hypo-osmotic conditions compared to iso-osmotic conditions is taken to indicate that TonEBP is negatively regulated by excess ROS produced by NOX4 under hypo-osmotic conditions. From Fig. 3b it is seen that TauT mRNA transcription is unaltered under hypo-osmotic conditions when overexpressing NOX4. Thus, the increased ROS availability generated from NOX4 under hypo-osmotic conditions does not seem to suppress TauT transcription via the altered TonEBP activity.Fig. 3
Affiliation: Department of Biology, Section of Cellular and Developmental Biology, University of Copenhagen, The August Krogh Building, Universitetsparken 13, 2100 Copenhagen Ø, Denmark.