IL-3 withdrawal activates a CrmA-insensitive poly(ADP-ribose) polymerase cleavage enzyme in factor-dependent myeloid progenitor cells.
Murine myeloid progenitor cells that are dependent on interleukin-3 (IL-3) undergo apoptosis when this essential cytokine is withdrawn. To determine whether IL-3 withdrawal leads to the activation of caspase proteases, known mediators of apoptosis, we studied proteolytic cleavage of the caspase substrate protein poly(ADP-ribose) polymerase (PARP) in two IL3-dependent myeloid progenitor cell lines, 32D and FDCP-1. We observed that IL-3 withdrawal leads to PARP cleavage in both cell lines, with complete cleavage occurring by 24 h after cytokine removal. The induced PARP cleavage activities were blocked by the caspase inhibitors z-DEVD-fluoromethyl ketone (z-DEVD-FMK) and z-VAD-fluoromethyl ketone (z-VAD-FMK), or by overexpression in 32D cells of Bcl-2 or BCR/ABL. By contrast, overexpression in 32D cells of cowpox virus CrmA protein, an inhibitor of Fas-mediated PARP cleavage, failed to inhibit PARP cleavage following IL-3 withdrawal. CrmA also failed to block DNA fragmentation and loss of cell viability. We propose that a CrmA-insensitive caspase protease is activated in the IL-3-deprived myeloid precursors, and that activation of this protease may direct the cells on a path towards commitment to death.
Antoku
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Department of Medicine, University of Pittsburgh, and the University of Pittsburgh Cancer Institute, PA 15213-2582, USA.
Liu
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Z
Johnson
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D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004247:DNA / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation; D006412:Hematopoietic Stem Cells / Q000201:enzymology*; D007377:Interleukin-3 / Q000494:pharmacology*; D051379:Mice; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D012680:Sensitivity and Specificity; D015843:Serpins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D013375:Substance Withdrawal Syndrome / Q000201:enzymology* / Q000209:etiology; D014162:Transfection; D014764:Viral Proteins
D007377:Interleukin-3; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011480:Protease Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D015843:Serpins; D014764:Viral Proteins; D004247:DNA; C074641:interleukin-1beta-converting enzyme inhibitor; D011065:Poly(ADP-ribose) Polymerases