Identification of a Novel Putative Non-selenocysteine Containing Phospholipid Hydroperoxide Glutathione Peroxidase (NPGPx) Essential for Alleviating Oxidative Stress Generated from Polyunsaturated Fatty Acids in Breast Cancer Cells

• Published in: The Journal of biological chemistry Vol. 279; no. 42; pp. 43522 - 43529
• Main Authors: Utomo, Ahmad, Jiang, Xianzhi, Furuta, Saori, Yun, Jeanho, Levin, David S, Wang, Yi-Chun J, Desai, Kartiki V, Green, Jeffrey E, Chen, Phang-Lang, Lee, Wen-Hwa
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 15-10-2004
• Subjects: Amino Acid Sequence; Animals; Base Sequence; BRCA1 Protein - deficiency; BRCA1 Protein - genetics; Breast Neoplasms; Carrier Proteins - chemistry; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cell Line, Tumor; DNA Primers; Eicosapentaenoic Acid - pharmacology; Fatty Acids, Unsaturated - pharmacology; Female; Glutathione Peroxidase - chemistry; Glutathione Peroxidase - genetics; Glutathione Peroxidase - metabolism; Humans; Mice; Mice, Knockout; Molecular Sequence Data; Oxidative Stress - drug effects; Oxidative Stress - physiology; Phospholipid Hydroperoxide Glutathione Peroxidase; Reverse Transcriptase Polymerase Chain Reaction; RNA, Small Interfering - genetics; Selenocysteine; Sequence Alignment; Sequence Homology, Amino Acid
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M407141200

A dramatic reduction in the expression of a novel phospholipid hydroperoxide glutathione peroxidase (PHGPx), which incorporates
cysteine instead of selenocysteine in the conserved catalytic motif was observed in a microarray analysis using cDNAs amplified
from mRNA of Brca1 -null mouse embryonic fibroblasts. This non-selenocysteine PHGPx named NPGPx is a cytoplasmic protein with molecular mass
of ∼22 kDa and has little detectable glutathione peroxidase activity in vitro . Ectopic expression of NPGPx in Brca1 -null cells that were sensitive to oxidative stress induced by hydrogen peroxide conferred a similar resistance level to that
of the wild-type cells, suggesting the importance of this protein in reducing oxidative stress. Expression of NPGPx was found
in many tissues, including developing mammary gland. However, the majority of breast cancer cell lines studied (11 of 12)
expressed very low or undetectable levels of NPGPx irrespective of BRCA1 status. Re-expression of NPGPx in breast cancer lines,
MCF-7 and HCC1937, which have very little or no endogenous NPGPx, induced resistance to eicosapentaenoic acid (an omega-3
type of polyunsaturated fatty acid)-mediated cell death. Conversely, inhibition of the expression of NPGPx by the specific
small interfering RNA in HS578T breast cancer cells that originally express substantial amounts of endogenous NPGPx increased
their sensitivity to eicosapentaenoic acid-mediated cell death. Thus, NPGPx plays an essential role in breast cancer cells
in alleviating oxidative stress generated from polyunsaturated fatty acid metabolism.