Regulation of aquaporin 3 expression by magnesium ion

Eur J Pharmacol. 2008 Jun 24;588(1):26-32. doi: 10.1016/j.ejphar.2008.03.063. Epub 2008 Apr 12.

Abstract

For understanding the actions of magnesium formulations, magnesium oxide and magnesium sulfate as a constituent of antacid, in the gastrointestinal tract, the effect of magnesium ion on the water channel aquaporin 3 (AQP3) known to be permeable mainly to water and glycerol was investigated in Caco-2 cells. The mRNA and protein of aquaporin 3 were detected by real-time RT-PCR and Western blotting, respectively, and found to increase significantly after treatment with magnesium acetate. Inhibitors for signal transducers, MDL-12330A, H-89, U0126, and Ro 31-8220, were shown to repress the increase in expression of the mRNA. A luciferase reporter vector containing bp -1382 to -12 of the 5'-flanking region of the aquaporin 3 gene was constructed for a reporter gene assay. The luciferase activity in transfectants increased on treatment with magnesium acetate. Serial deletion constructs revealed two regions responsible for the magnesium ion-mediated activation, one between bps -404 and -190, and the other between bps -190 and -82. siRNA for the cAMP response element-binding protein (CREB) sequence located between bp -404 and -190 counteracted the magnesium ion-mediated activation of aquaporin 3 transcription. These results suggest that signal transducers, adenylyl cyclase, protein kinase A (PKA), mitogen-activated protein kinase 1/2 (MEK1/2), and mitogen- and stress-activated protein kinase 1 (MSK1), were involved in the signaling pathway for regulating transcription of the aquaporin 3 gene and CREB is one of the transcriptional regulators for aquaporin 3 gene expression mediated by magnesium ion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aquaporin 3 / biosynthesis*
  • Blotting, Western
  • Caco-2 Cells
  • Chemistry, Pharmaceutical
  • Gene Expression Regulation / drug effects
  • Genes, Reporter
  • Genetic Vectors
  • Humans
  • Luciferases / metabolism
  • Magnesium / metabolism
  • Magnesium Compounds / pharmacology*
  • Mutagenesis, Site-Directed
  • RNA, Messenger / biosynthesis
  • RNA, Messenger / genetics
  • RNA, Small Interfering
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction / drug effects

Substances

  • Magnesium Compounds
  • RNA, Messenger
  • RNA, Small Interfering
  • Aquaporin 3
  • Luciferases
  • Magnesium