title: Mitochondria control of cell death induced by anti-HLA-DR antibodies.
abstract: We have previously reported that crosslinking HLA-DR directly induces programmed cell death of malignant B cells. The present study further characterizes the biochemical mechanism for HLA-DR-mediated programmed cell death of tumor cells. Phosphatidylserine exposure on the plasma membrane and propidium iodide incorporation occur with very rapid kinetics and are observed as early as 10 min after the induction of cell death with anti-HLA-DR. In striking contrast to anti-CD95, we observe no activation of caspase-3, -8, or -9 upon anti-HLA-DR addition. Furthermore, the irreversible caspase inhibitor Z-VAD.fmk also failed to inhibit anti-HLA-DR-mediated cell death, further supporting the conclusion that HLA-DR induces cell death via a caspase-independent mechanism. We demonstrate that anti-HLA-DR-induced cell death is instead associated with a rapid disruption of the inner mitochondrial transmembrane potential, DeltaPsi(m), a process that is significantly inhibited by Bcl-2 overexpression. Furthermore, we find that DeltaPsi(m) disruption results in the selective release of apoptosis-inducing factor (AIF) from the mitochondria. We propose that AIF is acting to initiate the morphological and biochemical changes observed in HLA-DR-mediated cell death.
authors.affiliation: Protein Design Labs, Inc., Department of Oncology, Fremont, CA 94555, USA.
authors.forename: S K
authors.initials: SK
authors.lastname: Bains
authors.forename: A
authors.initials: A
authors.lastname: Mone
authors.forename: J
authors.initials: J
authors.lastname: Yun Tso
authors.forename: D
authors.initials: D
authors.lastname: Lucas
authors.forename: J C
authors.initials: JC
authors.lastname: Byrd
authors.forename: G J
authors.initials: GJ
authors.lastname: Weiner
authors.forename: J M
authors.initials: JM
authors.lastname: Green
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D051033:Apoptosis Inducing Factor; D020169:Caspases / Q000378:metabolism; D003574:Cytochrome c Group; D005420:Flavoproteins / Q000378:metabolism; D006684:HLA-DR Antigens / Q000276:immunology / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008565:Membrane Proteins / Q000378:metabolism; D008928:Mitochondria / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology; D014407:Tumor Cells, Cultured
chemical_list: C494829:AIFM1 protein, human; D000911:Antibodies, Monoclonal; D051033:Apoptosis Inducing Factor; D003574:Cytochrome c Group; D005420:Flavoproteins; D006684:HLA-DR Antigens; D008565:Membrane Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D020169:Caspases