Essential role for the BH3-only protein Bim but redundant roles for Bax, Bcl-2, and Bcl-w in the control of granulocyte survival.
Programmed cell death of granulocytes is one of the mechanisms that limit inflammatory responses. Members of the Bcl-2 protein family are essential regulators of apoptosis induced by growth factor withdrawal or cytotoxic stress. We have used gene-targeted and transgenic mice to investigate the roles of the prosurvival molecules Bcl-2 and Bcl-w and their proapoptotic relatives Bax and Bim in spontaneous and stress-induced apoptosis of granulocytes from bone marrow or the peritoneum. Bim deficiency, like Bcl-2 overexpression, rendered granulocytes resistant to cytokine withdrawal and cytotoxic drugs, but absence of Bax alone had no protective effect. Loss of Bcl-2 or Bcl-w did not increase the sensitivity of granulocytes to any of these apoptotic stimuli, but Bcl-2 was essential for the in vitro survival of myeloid progenitors under conditions of cytokine withdrawal where cell death was mediated, in part, by Bim. Granulocyte colony-stimulating factor (G-CSF), a key survival factor for granulocytes, enhanced viability of cells lacking bcl-2, bcl-w, bax, or bim, indicating that none of these genes alone is the essential target of this cytokine's prosurvival function. Expression analysis of proapoptotic Bcl-2 family members in granulocytes revealed that the BH3-only protein Bmf is induced upon cytokine withdrawal. These results indicate that the BH3-only protein Bim and possibly also Bmf are critical initiators of spontaneous and drug-induced apoptosis of granulocytes, whereas Bcl-2, Bcl-w, and Bax act in a redundant manner in regulating granulocyte survival and death, respectively.
Villunger
Andreas
A
Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.
Scott
Clare
C
Bouillet
Philippe
P
Strasser
Andreas
A
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins; D000072224:Bcl-2-Like Protein 11; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D002470:Cell Survival; D002478:Cells, Cultured; D016207:Cytokines / Q000008:administration & dosage / Q000502:physiology; D005455:Fluorescent Antibody Technique; D015870:Gene Expression; D016179:Granulocyte Colony-Stimulating Factor / Q000008:administration & dosage; D006098:Granulocytes / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D006412:Hematopoietic Stem Cells / Q000502:physiology; D008565:Membrane Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051028:bcl-2-Associated X Protein
D051017:Apoptosis Regulatory Proteins; C494827:Bax protein, mouse; D000072224:Bcl-2-Like Protein 11; C000606776:Bcl2l11 protein, mouse; C101155:Bcl2l2 protein, mouse; D002352:Carrier Proteins; D016207:Cytokines; D008565:Membrane Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D051028:bcl-2-Associated X Protein; D016179:Granulocyte Colony-Stimulating Factor