You are here

THE EFFECTS OF ARSENITE ON SELENOPROTEINS BIOSYTHESIS

Download pdf | Full Screen View

Date Issued:
2005
Abstract/Description:
Arsenic contamination of drinking water is a real public health problem in certain areas of South-East Asia where chronic exposure has been correlated to higher rates of lung, skin, bladder, kidney, and liver cancer. Although arsenic carcinogenicity is well established, the mechanism by which it induces cancer is poorly understood. Recent evidence suggests that oxidative stress could be a possible mechanism for the carcinogenic effects of arsenic. Selenium, in the form of selenocysteine, is necessary for the activity of several enzymes with a role in the defense against reactive oxygen species (ROS), primarily thioredoxin reductases (TrxR) and glutathione peroxidases (Gpx). One of the key enzymes in the incorporation of Se into selenoproteins is selenophosphate synthetase (SPS). SPS catalyzes the activation of Se to selenophosphate, and is the first step in the pathway of selenoprotein biosynthesis. SPS contains a conserved vicinal dithiol motif (CXC) within a region of amino acids that have been predicted to be a selenium binding site. Our hypothesis is that arsenite inhibits new selenoprotein synthesis, thus indirectly increasing the level of ROS. In this study we have developed a spectrophotometric assay for SPS. Using this assay, we have determined that arsenite inhibits SPS activity. Kinetic analysis of this inhibition showed that arsenite, a trivalent form of arsenic, acts as a competitive inhibitor with the substrate, sodium selenide. This inhibition of SPS could represent a potential molecular mechanism for oxidative stress induced upon arsenite treatment of human cell lines in culture. To further study the effects of trivalent arsenicals at a cellular level we decided to use a human keratinocyte cell line, HaCaT as a cell culture model. Our study showed that although arsenite does not alter cell proliferation or protein synthesis, it specifically inhibits new selenoprotein synthesis. However, short term or long term exposure of HaCaT cells to arsenite failed to result in changes to Gpx and TrxR levels. Since the radioisotope selenium used in labeling studies is selenite, these results indicate that an alternate source of selenium may bypass the inhibitory effects of arsenite. Future studies will focus on studying the effects of arsenicals on keratinocytes cultured in a defined medium allowing a better control of the selenium source.
Title: THE EFFECTS OF ARSENITE ON SELENOPROTEINS BIOSYTHESIS.
0 views
0 downloads
Name(s): Konate, Fanta, Author
Self, William , Committee Chair
University of Central Florida, Degree Grantor
Type of Resource: text
Date Issued: 2005
Publisher: University of Central Florida
Language(s): English
Abstract/Description: Arsenic contamination of drinking water is a real public health problem in certain areas of South-East Asia where chronic exposure has been correlated to higher rates of lung, skin, bladder, kidney, and liver cancer. Although arsenic carcinogenicity is well established, the mechanism by which it induces cancer is poorly understood. Recent evidence suggests that oxidative stress could be a possible mechanism for the carcinogenic effects of arsenic. Selenium, in the form of selenocysteine, is necessary for the activity of several enzymes with a role in the defense against reactive oxygen species (ROS), primarily thioredoxin reductases (TrxR) and glutathione peroxidases (Gpx). One of the key enzymes in the incorporation of Se into selenoproteins is selenophosphate synthetase (SPS). SPS catalyzes the activation of Se to selenophosphate, and is the first step in the pathway of selenoprotein biosynthesis. SPS contains a conserved vicinal dithiol motif (CXC) within a region of amino acids that have been predicted to be a selenium binding site. Our hypothesis is that arsenite inhibits new selenoprotein synthesis, thus indirectly increasing the level of ROS. In this study we have developed a spectrophotometric assay for SPS. Using this assay, we have determined that arsenite inhibits SPS activity. Kinetic analysis of this inhibition showed that arsenite, a trivalent form of arsenic, acts as a competitive inhibitor with the substrate, sodium selenide. This inhibition of SPS could represent a potential molecular mechanism for oxidative stress induced upon arsenite treatment of human cell lines in culture. To further study the effects of trivalent arsenicals at a cellular level we decided to use a human keratinocyte cell line, HaCaT as a cell culture model. Our study showed that although arsenite does not alter cell proliferation or protein synthesis, it specifically inhibits new selenoprotein synthesis. However, short term or long term exposure of HaCaT cells to arsenite failed to result in changes to Gpx and TrxR levels. Since the radioisotope selenium used in labeling studies is selenite, these results indicate that an alternate source of selenium may bypass the inhibitory effects of arsenite. Future studies will focus on studying the effects of arsenicals on keratinocytes cultured in a defined medium allowing a better control of the selenium source.
Identifier: CFE0000453 (IID), ucf:46406 (fedora)
Note(s): 2005-05-01
M.S.
Burnett College of Biomedical Sciences, Department of Molecular Biology and Microbiology
Masters
This record was generated from author submitted information.
Subject(s): Arsenic
Arsenite
Selenoproteins
Selenophosphate Synthetase
Persistent Link to This Record: http://purl.flvc.org/ucf/fd/CFE0000453
Restrictions on Access: private 2025-01-31
Host Institution: UCF

In Collections