Metallothionein isoform 2A expression is inducible and protects against ROS-mediated cell death in rotenone-treated HeLa cells

Biochem J. 2006 Apr 15;395(2):405-15. doi: 10.1042/BJ20051253.


The role of MT (metallothionein) gene expression was investigated in rotenone-treated HeLa cells to induce a deficiency of NADH:ubiquinone oxidoreductase (complex I). Complex I deficiency leads to a diversity of cellular consequences, including production of ROS (reactive oxygen species) and apoptosis. HeLa cells were titrated with rotenone, resulting in dose-dependent decrease in complex I activity and elevated ROS production at activities lower than 33%. Expression of MT2A (MT isoform 2A), but not MT1A or MT1B RNA, was significantly inducible by rotenone (up to 7-fold), t-BHP (t-butyl hydroperoxide; 5-fold) and CdCl2 (50-fold), but not ZnCl2. Myxothiazol treatment did not elevate either ROS or MT2A levels, which supports a ROS-related mechanism for rotenone-induced MT2A expression. To evaluate the role of MT2A expression, MT2A and MT1B were overexpressed in HeLa cells and treated with rotenone. Compared with control and MT1B-overexpressing cells, ROS production was significantly lower and cell viability higher in MT2A-overexpressing HeLa cells when ROS production was enhanced by treatment with t-BHP. Mitochondrial membrane potential was noticeably less reduced in both MT-overexpressing cell lines. MT2A overexpression in rotenone-treated cells also significantly reduced or delayed apoptosis induction, as measured by caspase 3/7 activity and cytosolic nucleosome enrichment. We conclude that MT2A offers significant protection against the main death-causing consequences of rotenone-induced complex I deficiency in HeLa cells. Our results are in support of the protective role against oxidative stress ascribed to MTs and provide evidence that MT2A expression may be a beneficial downstream adaptive response in complex I-deficient cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / analysis
  • Apoptosis / drug effects
  • Cell Death / drug effects
  • Cell Survival / drug effects
  • Cells, Cultured
  • Electron Transport Complex I / drug effects
  • Electron Transport Complex III / drug effects
  • HeLa Cells
  • Humans
  • Membrane Potentials / drug effects
  • Metallothionein / genetics
  • Metallothionein / metabolism*
  • Mitochondria / metabolism
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Reactive Oxygen Species / metabolism*
  • Recombinant Proteins / metabolism
  • Rotenone / pharmacology*
  • Up-Regulation / drug effects*
  • tert-Butylhydroperoxide / pharmacology


  • Protein Isoforms
  • RNA, Messenger
  • Reactive Oxygen Species
  • Recombinant Proteins
  • Rotenone
  • Adenosine Triphosphate
  • Metallothionein
  • tert-Butylhydroperoxide
  • Electron Transport Complex I
  • Electron Transport Complex III