Carcinogenesis Advance Access originally published online on June 15, 2006
Carcinogenesis 2006 27(12):2538-2549; doi:10.1093/carcin/bgl111
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Thioredoxin reductase is required for the inactivation of tumor suppressor p53 and for apoptosis induced by endogenous electrophiles
1 Huntsman Cancer Institute L.S. Skagg’s Pharmacy, Room 201, 30 S 2000 Salt Lake City, UT 84112, USA
2 The Department of Medicinal Chemistry L.S. Skagg’s Pharmacy, Room 201, 30 S 2000 Salt Lake City, UT 84112, USA
3 The Mass Spectrometry and Proteomics Core Facility L.S. Skagg’s Pharmacy, Room 201, 30 S 2000 Salt Lake City, UT 84112, USA
4 The Department of Pharmacology and Toxicology, University of Utah L.S. Skagg’s Pharmacy, Room 201, 30 S 2000 Salt Lake City, UT 84112, USA
*To whom correspondence should be addressed Email: philip.moos{at}pharm.utah.edu
Previous studies demonstrate that the covalent modification of thioredoxin reductase (TrxR) by both endogenous and exogenous electrophiles results in disruption of the conformation of the tumor suppressor protein p53. Here we report that the loss of normal cellular TrxR enzymatic activity by electrophilic modification or deletion of the C-terminal catalytic selenocysteine residue has functional consequences that are distinct from those resulting from depletion of TrxR protein in human RKO colon cancer cells. A thorough kinetic analysis was performed on purified TrxR in order to characterize the mechanism of its inhibition by electrophiles. Furthermore, electrospray mass spectrometry confirmed the alkylation of TrxR by lipid electrophiles and liquid chromatography-mass spectrometry/mass spectrometry identified the C-terminus as one target for alkylation. Then the consequences of TrxR modification by electrophiles on p53 conformation, transactivation and apoptosis were compared and contrasted with the effects of depletion of TrxR protein by treatment of cells with small interfering RNA directed against TrxR1. We found that cells depleted of TrxR were actually less sensitive to electrophile-induced disruption of p53 conformation and apoptosis than were cells expressing normal levels of TrxR. When RKO cells depleted of wild-type TrxR were transfected with C-terminal mutants of TrxR lacking the catalytic selenocysteine, p53 was found to be conformationally deranged, similar to cells treated with electrophiles. These results lead us to conclude that C-terminal modification of TrxR is both necessary and sufficient for the disruption of p53 and for the induction of apoptosis. Endogenous lipid electrophiles have been our primary focus; however, metabolic activation of hormones can generate endogenous mutagens, and we demonstrate that estrone–quinone attenuates p53 function in human MCF7 cells.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  P. A. Grimsrud, H. Xie, T. J. Griffin, and D. A. Bernlohr Oxidative Stress and Covalent Modification of Protein with Bioactive Aldehydes J. Biol. Chem., August 8, 2008; 283(32): 21837 - 21841. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E.-H. Chew, J. Lu, T. D. Bradshaw, and A. Holmgren Thioredoxin reductase inhibition by antitumor quinols: a quinol pharmacophore effect correlating to antiproliferative activity FASEB J, June 1, 2008; 22(6): 2072 - 2083. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Lu, E.-H. Chew, and A. Holmgren Targeting thioredoxin reductase is a basis for cancer therapy by arsenic trioxide PNAS, July 24, 2007; 104(30): 12288 - 12293. [Abstract] [Full Text] [PDF]
|
|