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1.
Mouse embryonic fibroblast (MEF) cells prepared from transgenic mice overexpressing a cancer-specific and growth-related cell surface NADH oxidase with protein disulfide-thiol interchange activity grew at rates approximately twice those of wild-type embryonic fibroblast cells. Growth of transgenic MEF cells overexpressing tNOX was inhibited by low concentrations of the green tea catechin (-)-epigallocatechin-3-gallate (EGCg) or the synthetic isoflavene phenoxodiol. Both are putative tNOX-targeted inhibitors with anti-cancer activity. With both EGCg and phenoxodiol, growth inhibition was followed after about 48 h by apoptosis. Growth of wild-type mouse fibroblast cells from the same strain was unaffected by EGCg and phenoxodiol and neither compound induced apoptosis even at concentrations 100-1,000-fold higher than those that resulted in apoptotic death in the transgenic MEF cells. The findings validate earlier reports of evidence for tNOX presence as contributing to unregulated growth of cancer cells as well as the previous identification of the tNOX protein as the molecular target for the anti-cancer activities attributed to both EGCg and phenoxodiol. The expression of tNOX emerges as both necessary and sufficient to account for the cancer cell-specific growth inhibitions by both EGCg and phenoxodiol. 相似文献
2.
Thomas De Luca Dorothy M. Morré D. James Morré PhD 《Journal of cellular biochemistry》2010,110(6):1504-1511
ENOX2 (tNOX), a tumor‐associated cell surface ubiquinol (NADH) oxidase, functions as an alternative terminal oxidase for plasma membrane electron transport. Ubiquitous in all cancer cell lines studied thus far, ENOX2 expression correlates with the abnormal growth and division associated with the malignant phenotype. ENOX2 has been proposed as the cellular target for various quinone site inhibitors that demonstrate anticancer activity such as the green tea constituent epigallocatechin‐3‐gallate (EGCg) and the isoflavene phenoxodiol (PXD). Here we present a possible mechanism that explains how these substances result in apoptosis in cancer cells by ENOX2‐mediated alterations of cytosolic amounts of NAD+ and NADH. When ENOX2 is inhibited, plasma membrane electron transport is diminished, and cytosolic NADH accumulates. We show in HeLa cells that NADH levels modulate the activities of two pivotal enzymes of sphingolipid metabolism: sphingosine kinase 1 (SK1) and neutral sphingomyelinase (nSMase). Their respective products sphingosine 1‐phosphate (S1P) and ceramide (Cer) are key determinants of cell fate. S1P promotes cell survival and Cer promotes apoptosis. Using plasma membranes isolated from cervical adenocarcinoma (HeLa) cells as well as purified proteins of both bacterial and human origin, we demonstrate that NADH inhibits SK1 and stimulates nSMase, while NAD+ inhibits nSMase and has no effect on SK1. Additionally, intact HeLa cells treated with ENOX2 inhibitors exhibit an increase in Cer and a decrease in S1P. Treatments that stimulate cytosolic NADH production potentiate the antiproliferative effects of ENOX2 inhibitors while those that attenuate NADH production or stimulate plasma membrane electron transport confer a survival advantage. J. Cell. Biochem. 110: 1504–1511, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
3.
Tang X Chueh PJ Jiang Z Layman S Martin B Kim C Morré DM Morré DJ 《Journal of bioenergetics and biomembranes》2010,42(5):355-360
ECTO-NOX proteins are growth-related cell surface proteins that catalyze both hydroquinone or NADH oxidation and protein disulfide
interchange and exhibit time-keeping and prion-like properties. A bacterially expressed truncated recombinant 46 kDa ENOX2
with full ENOX2 activity bound ca 2 moles copper and 2 moles of zinc per mole of protein. Unfolding of the protein in trifluoroacetic
acid in the presence of the copper chelator bathocuproine resulted in reversible loss of both enzymatic activities and of
a characteristic pattern in the Amide I to Amide II ratios determined by FTIR with restoration by added copper. The H546-V-H
together with His 562 form one copper binding site and H582 represents a second copper site as determined from site-directed
mutagenesis. Bound copper emerges as having an essential role in ENOX2 both for enzymatic activity and for the structural
changes that underly the periodic alternations in activity that define the time-keeping cycle of the protein. 相似文献
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