Bcl-2 antibodies induce hemoglobin release by red blood cells loaded with in vitro translated Bcl-2 and its cleaved fragment.
Apoptosis induced by proteasome inhibitor in human THP-1 leukemia cells is associated with the cleavage of Bcl-2 into a shortened fragment, Bcl-2/Delta34. Both Bcl-2 and its cleaved fragment were located exclusively on the mitochondria of THP-1 cells. No translocation of Bcl-2 or Bcl-2/Delta34 to the cytosolic fraction was detected during apoptosis. Treatment of isolated mitochondria with recombinant caspase-3 induced the same cleavage of Bcl-2 in vitro and triggered the release of cytochrome c from the mitochondria. The ability of Bcl-2/Delta34 in regulating the opening of membrane "pores" was investigated using a sheep red blood cell (RBC) model with in vitro translated Bcl-2/Delta34 and Bcl-2 proteins. Bcl-2 and Bcl-2/Delta34 generated in vitro were relocated rapidly to sheep RBC but caused no hemoglobin release in either case. Addition of anti-Bcl-2 antibodies directly to the RBC that had been loaded with either Bcl-2 or Bcl-2/Delta34 resulted in a rapid release of hemoglobin from the blood cells. Treatment of the sheep RBC with anti-Bcl-2 or anti-sheep RBC antibodies alone did not trigger hemoglobin release from the RBC. Based on these findings, we proposed that, upon "enforced aggregation," both Bcl-2 and Bcl-2/Delta34 can form "pores" in membranes, which may contribute to the release of cytochrome c in apoptosis.
Chen
C
C
Division of Hematology-Oncology, Barbara Ann Karmanos Cancer Institute, Detroit, Michigan 48201, USA.
Lin
H
H
Chen
B D
BD
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004789:Enzyme Activation; D004912:Erythrocytes / Q000502:physiology*; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D007938:Leukemia; D008928:Mitochondria / Q000378:metabolism*; D014176:Protein Biosynthesis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D012756:Sheep; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D000906:Antibodies; D006454:Hemoglobins; D019253:Proto-Oncogene Proteins c-bcl-2; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases