title: Thiol oxidation enforces phosphatidylserine externalization in apoptosis-sensitive and -resistant cells through a deltapsim/cytochrome C release-dependent mechanism.
abstract: Previous studies have shown that unlike most apoptotic cells, Raji cells do not externalize phosphatidylserine (PS) upon apoptosis. Here we show that Raji cells are resistant to intrinsic apoptogenic agents, but sensitive to extrinsically triggered Fas-induced apoptosis. Treatment of intrinsic apoptosis-competent Jurkat cells with vitamin E implicated reactive oxygen species in intrinsic apoptosis because, like Raji cells, they became resistant to actinomycin D- but not Fas-triggered apoptosis. Oxidation of sulfhydryls in both cell types with N-ethylmaleimide resulted in rapid disruption of the mitochondrial membrane potential, release of cytochrome c from the mitochondria to the cytoplasm, and externalization of PS by a mechanism that was not inhibited by the pan caspase inhibiter zVAD-fmk. These results suggest that although cell death and PS externalization are both cytochrome c-dependent, they are distinct and separable processes.
authors.affiliation: Department of Cancer Biology, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: A Johanna
authors.initials: AJ
authors.lastname: Forsberg
authors.forename: Valerian E
authors.initials: VE
authors.lastname: Kagan
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Schroit
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000378:metabolism; D000975:Antioxidants / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D045304:Cytochromes c / Q000378:metabolism*; D003609:Dactinomycin / Q000378:metabolism; D005033:Ethylmaleimide / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D008228:Lymphoma, Non-Hodgkin; D008564:Membrane Potentials / Q000502:physiology*; D010084:Oxidation-Reduction; D010718:Phosphatidylserines / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013439:Sulfhydryl Reagents / Q000378:metabolism; D014810:Vitamin E / Q000378:metabolism; D019014:fas Receptor / Q000378:metabolism
chemical_list: D000903:Antibiotics, Antineoplastic; D000975:Antioxidants; D010718:Phosphatidylserines; D017382:Reactive Oxygen Species; D013438:Sulfhydryl Compounds; D013439:Sulfhydryl Reagents; D019014:fas Receptor; D014810:Vitamin E; D003609:Dactinomycin; D045304:Cytochromes c; D005033:Ethylmaleimide