Limits...
Downregulation of the taurine transporter TauT during hypo-osmotic stress in NIH3T3 mouse fibroblasts.

Hansen DB, Friis MB, Hoffmann EK, Lambert IH - J. Membr. Biol. (2012)

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.

View Article: PubMed Central - PubMed

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

Related in: MedlinePlus

NOX4 regulates TonEBP activity, but not TauT transcription, under hypo-osmotic conditions. TonEBP activity and TauT transcription were estimated in NIH3T3 cells exposed for 4 h to iso-osmotic or hypo-osmotic medium (DMEM). Cells were transfected with NOX4 (hatched bars) or mock-transfected (open bars) as described in Materials and Methods. TonEBP activity and TauT mRNA were estimated as described in the legend to Fig. 2 and Materials and Methods. a TonEBP activity in NOX4-transfected cells relative to non-transfected iso-osmotic control. b TauT mRNA transcription in mock- and NOX4-transfected cells. Values are given relative to their respective iso-osmotic control ± SEM. Data in (a) represent seven sets of experiments. Data in (b) represent four (hypo-osmotic) and three (NOX4) sets of experiments. Statistical evaluation for (a) and (b) by Student’s t-test (paired, one-sided) comparing hyperosmotic, hypo-osmotic or hypo-osmotic+NOX4 to the respective iso-osmotic control. Values are given relative to iso-osmotic control ± SEM. *P < 0.05, **P < 0.01 compared to iso-osmotic control
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3298736&req=5

Fig3: NOX4 regulates TonEBP activity, but not TauT transcription, under hypo-osmotic conditions. TonEBP activity and TauT transcription were estimated in NIH3T3 cells exposed for 4 h to iso-osmotic or hypo-osmotic medium (DMEM). Cells were transfected with NOX4 (hatched bars) or mock-transfected (open bars) as described in Materials and Methods. TonEBP activity and TauT mRNA were estimated as described in the legend to Fig. 2 and Materials and Methods. a TonEBP activity in NOX4-transfected cells relative to non-transfected iso-osmotic control. b TauT mRNA transcription in mock- and NOX4-transfected cells. Values are given relative to their respective iso-osmotic control ± SEM. Data in (a) represent seven sets of experiments. Data in (b) represent four (hypo-osmotic) and three (NOX4) sets of experiments. Statistical evaluation for (a) and (b) by Student’s t-test (paired, one-sided) comparing hyperosmotic, hypo-osmotic or hypo-osmotic+NOX4 to the respective iso-osmotic control. Values are given relative to iso-osmotic control ± SEM. *P < 0.05, **P < 0.01 compared to iso-osmotic control

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


Downregulation of the taurine transporter TauT during hypo-osmotic stress in NIH3T3 mouse fibroblasts.

Hansen DB, Friis MB, Hoffmann EK, Lambert IH - J. Membr. Biol. (2012)

NOX4 regulates TonEBP activity, but not TauT transcription, under hypo-osmotic conditions. TonEBP activity and TauT transcription were estimated in NIH3T3 cells exposed for 4 h to iso-osmotic or hypo-osmotic medium (DMEM). Cells were transfected with NOX4 (hatched bars) or mock-transfected (open bars) as described in Materials and Methods. TonEBP activity and TauT mRNA were estimated as described in the legend to Fig. 2 and Materials and Methods. a TonEBP activity in NOX4-transfected cells relative to non-transfected iso-osmotic control. b TauT mRNA transcription in mock- and NOX4-transfected cells. Values are given relative to their respective iso-osmotic control ± SEM. Data in (a) represent seven sets of experiments. Data in (b) represent four (hypo-osmotic) and three (NOX4) sets of experiments. Statistical evaluation for (a) and (b) by Student’s t-test (paired, one-sided) comparing hyperosmotic, hypo-osmotic or hypo-osmotic+NOX4 to the respective iso-osmotic control. Values are given relative to iso-osmotic control ± SEM. *P < 0.05, **P < 0.01 compared to iso-osmotic control
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3298736&req=5

Fig3: NOX4 regulates TonEBP activity, but not TauT transcription, under hypo-osmotic conditions. TonEBP activity and TauT transcription were estimated in NIH3T3 cells exposed for 4 h to iso-osmotic or hypo-osmotic medium (DMEM). Cells were transfected with NOX4 (hatched bars) or mock-transfected (open bars) as described in Materials and Methods. TonEBP activity and TauT mRNA were estimated as described in the legend to Fig. 2 and Materials and Methods. a TonEBP activity in NOX4-transfected cells relative to non-transfected iso-osmotic control. b TauT mRNA transcription in mock- and NOX4-transfected cells. Values are given relative to their respective iso-osmotic control ± SEM. Data in (a) represent seven sets of experiments. Data in (b) represent four (hypo-osmotic) and three (NOX4) sets of experiments. Statistical evaluation for (a) and (b) by Student’s t-test (paired, one-sided) comparing hyperosmotic, hypo-osmotic or hypo-osmotic+NOX4 to the respective iso-osmotic control. Values are given relative to iso-osmotic control ± SEM. *P < 0.05, **P < 0.01 compared to iso-osmotic control
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

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.

View Article: PubMed Central - PubMed

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
Related in: MedlinePlus