Cadmium induces nuclear translocation of beta-catenin and increases expression of c-myc and Abcb1a in kidney proximal tubule cells

Biometals. 2007 Oct;20(5):807-20. doi: 10.1007/s10534-006-9044-9. Epub 2006 Nov 29.

Abstract

Cadmium (Cd2+) induces renal proximal tubular (PT) damage, including disruption of the E-cadherin/beta-catenin complex of adherens junctions (AJs) and apoptosis. Yet, chronic Cd2+ exposure causes malignant transformation of renal cells. Previously, we have demonstrated that Cd(2+)-mediated up-regulation of the multidrug transporter Abcb1 causes apoptosis resistance in PT cells. We hypothesized that Cd2+ activates adaptive signaling mechanisms mediated by beta-catenin to evade apoptosis and increase proliferation. Here we show that 50 microM Cd2+, which induces cell death via apoptosis and necrosis, also causes a decrease of the trans-epithelial resistance of confluent WKPT-0293 Cl.2 cells, a rat renal PT cell model, within 45 min of Cd2+ exposure, as measured by electric cell-substrate impedance sensing. Immunofluorescence microscopy demonstrates Cd(2+)-induced decrease of E-cadherin at AJs and redistribution of beta-catenin from the E-cadherin/beta-catenin complex of AJs to cytosol and nuclei after 3 h. Immunoblotting confirms Cd(2+)-induced decrease of E-cadherin expression and translocation of beta-catenin to cytosol and nuclei of PT cells. RT-PCR shows Cd(2+)-induced increase of expression of c-myc and of the isoform Abcb1a at 3 h. The data prove for the first time that Cd2+ induces nuclear translocation of beta-catenin in PT cells. We speculate that Cd2+ activates beta-catenin/T-cell factor signaling to trans-activate proliferation and apoptosis resistance genes and promote carcinogenesis of PT cells.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter 1
  • ATP-Binding Cassette Transporters / biosynthesis*
  • ATP-Binding Cassette Transporters / genetics*
  • Active Transport, Cell Nucleus / physiology
  • Animals
  • Cadherins / biosynthesis
  • Cadherins / genetics
  • Cadmium / physiology*
  • Cell Line, Transformed
  • Cell Nucleus / metabolism*
  • Kidney Tubules, Proximal / cytology
  • Kidney Tubules, Proximal / drug effects
  • Kidney Tubules, Proximal / metabolism*
  • Proto-Oncogene Proteins c-myc / biosynthesis
  • Proto-Oncogene Proteins c-myc / genetics*
  • Rats
  • Up-Regulation / drug effects*
  • Up-Regulation / genetics
  • beta Catenin / biosynthesis
  • beta Catenin / genetics
  • beta Catenin / metabolism*

Substances

  • ATP Binding Cassette Transporter 1
  • ATP-Binding Cassette Transporters
  • Cadherins
  • Proto-Oncogene Proteins c-myc
  • beta Catenin
  • Cadmium