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Hyperosmolarity-Induced Down-Regulation of Claudin-2 Mediated by Decrease in PKCβ-Dependent GATA-2 in MDCK Cells.

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|April 1, 2015
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Summary
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Hyperosmolarity reduces claudin-2 expression in kidney cells through protein kinase C beta (PKCβ) and GATA-2 transcription factors. This pathway involves calcium channels and affects gene promoter activity.

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Area of Science:

  • Nephrology
  • Molecular Biology
  • Cell Biology

Background:

  • Hyperosmolarity is known to affect renal tubular epithelial cells.
  • The precise molecular mechanisms by which hyperosmolarity influences claudin-2 expression are not fully understood.

Purpose of the Study:

  • To elucidate the molecular pathway through which hyperosmolarity decreases claudin-2 expression in renal tubular epithelial cells.
  • To investigate the roles of protein kinase C (PKC) and GATA-2 in this process.

Main Methods:

  • Utilized Madin-Darby canine kidney II cells.
  • Employed inhibitors of PKC (Go6983, PKCβ specific inhibitor) and transient receptor potential vanilloid 4 channel (RN-1734).
  • Assessed claudin-2 expression via real-time PCR and Western blotting, promoter activity using reporter assays, and GATA-2 levels through nuclear fractionation and chromatin immunoprecipitation.

Main Results:

  • Hyperosmolarity decreased claudin-2 expression, promoter activity, and nuclear GATA-2 levels.
  • These effects were mediated by the activation of RN-1734-sensitive channels and PKCβ.
  • PKC activation mimicked the effect of hyperosmolarity, and GATA-2 binding to the claudin-2 promoter was confirmed.

Conclusions:

  • Hyperosmolarity decreases claudin-2 expression in renal tubular epithelial cells.
  • This decrease is dependent on the activation of a transient receptor potential vanilloid 4 channel and protein kinase C beta.
  • The mechanism involves reduced GATA-2 transcriptional activity on the claudin-2 promoter.