title: Hyperexpression of catalase in selenium-deprived murine L1210 cells.
abstract: Murine leukemia L1210 cells grown for 2-3 weeks in the presence of 1% serum without selenium supplementation [L.Se(-) cells] typically exhibited < 10% of the glutathione peroxidase (GPX) and phospholipid hydroperoxide glutathione peroxidase (PHGPX) activity of selenium-satisfied controls [L.Se(+) cells]. Concomitant with diminished GPX and PHGPX activity was a 1.5- to 2.0-fold increase in catalase (CAT) activity, which reverted to control levels when L.Se(-) cells were given sufficient Se for full expression of selenoperoxidase activity. Selenium manipulation affected total glutathione content similarly, but had no effect on glutathione-S-transferase or superoxide dismutase activity. Long-term growth under Se-deficient conditions resulted in a progressive additional increase in CAT activity, which maximized after ca. 5 months. These cells [referred to as L'.Se(-)] attained CAT activity levels at least 100-times greater than those of Se-supplemented [L'.Se(+)] controls, whereas their glutathione content remained elevated by approximately 70%. Supplying L'.Se(-) cells with Se resulted in a rapid elevation to full GPX activity; however, CAT failed to decline in this case, suggesting that a selection for stable CAT hyperexpressing variants had been accomplished. Quantitative immunoblot analysis indicated that the high CAT activity of L'.Se(-) cells is accounted for by an elevated level of enzyme protein. Induction of CAT and selection for CAT-rich phenotypes, as apparent for Se-starved L1210 cells, was not observed in human K562 counterparts, which lack GPX and express only a low level of PHGPX. L.Se(-) cells were found to be more sensitive to H2O2-induced killing than L.Se(+) controls, whereas L'.Se(-) cells were exceedingly more resistant to H2O2 than L'.Se(+) counterparts. By contrast, L.Se(-) and L'.Se(-) cells were both more sensitive to t-butyl hydroperoxide than Se(+) controls, consistent with CAT being unimportant in the detoxification of this peroxide compared with GPX. This appears to be the first reported evidence for CAT hyperexpression in response to selenium deprivation.
authors.affiliation: Department of Biochemistry, Medical College of Wisconsin, Milwaukee 53226.
authors.forename: F
authors.initials: F
authors.lastname: Lin
authors.forename: J P
authors.initials: JP
authors.lastname: Thomas
authors.forename: A W
authors.initials: AW
authors.lastname: Girotti
mesh_terms: D000818:Animals; D002374:Catalase / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects; D002455:Cell Division; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D015151:Immunoblotting; D007939:Leukemia L1210 / Q000201:enzymology*; D051379:Mice; D000080662:Phospholipid Hydroperoxide Glutathione Peroxidase; D012643:Selenium / Q000008:administration & dosage* / Q000502:physiology; D014407:Tumor Cells, Cultured
chemical_list: D006861:Hydrogen Peroxide; D000080662:Phospholipid Hydroperoxide Glutathione Peroxidase; D002374:Catalase; D005979:Glutathione Peroxidase; D005978:Glutathione; D012643:Selenium