Role of Bax in apoptosis of IL-3-dependent cells.
IL-3 removal was reported to induce membrane association of the apoptotic effector Bax. This report demonstrates that IL-3-dependent cells from Bax-null mice failed to activate caspases after IL-3 removal and survived in an 10-fold lower concentration of IL-3. As IL-3 removal also down-regulates expression of Bcl-X, we examined the relationship between Bcl-X decrease and Bax membrane association. IL-3 removal from BAF-3 cells, followed by sorting caspase-active and caspase-inactive populations, showed that both expressed similar levels of Bcl-X. Inhibition of IL-3 signalling via PI-3 kinase and MEK1/2 resulted in cells with minimal Bcl-X, which remained viable with soluble Bax. However BAF-3-derived cells, which maintained Bcl-X expression without IL-3, also remained viable with soluble Bax on IL-3 removal. Therefore a decrease in Bcl-X is necessary, though not sufficient, for Bax membrane association on IL-3 removal. In contrast, treatment of BAF-3 cells with hydroxyurea induced apoptosis in the absence of a Bcl-X decrease. Furthermore, IL-3-dependent cells from Bax-null mice activated caspases after hydroxyurea treatment and show the same sensitivity to a variety of cytotoxic drugs. Thus, apoptosis after IL-3 removal requires a decrease in Bcl-X and Bax membrane association, whereas that induced by cytotoxic drugs does not.
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Department of Immunology and Molecular Pathology, University College London, Windeyer Institute of Medical Science, 46 Cleveland Street, London W1P 6DB, UK.
Olmos-Centenera
G
G
Madsen
C
C
Leverrier
Y
Y
Collins
M K
MK
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D020169:Caspases / Q000378:metabolism; D002460:Cell Line / Q000187:drug effects / Q000528:radiation effects; D002462:Cell Membrane / Q000378:metabolism*; D002469:Cell Separation; D002945:Cisplatin / Q000494:pharmacology; D003114:Colony-Forming Units Assay; D019281:Dimerization; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005467:Floxuridine / Q000494:pharmacology; D015870:Gene Expression; D005786:Gene Expression Regulation; D006918:Hydroxyurea / Q000494:pharmacology; D007377:Interleukin-3 / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008727:Methotrexate / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008970:Molecular Weight; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics; D015398:Signal Transduction; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
C494827:Bax protein, mouse; C494812:Bcl2l1 protein, mouse; D004791:Enzyme Inhibitors; D007377:Interleukin-3; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D005467:Floxuridine; D019869:Phosphatidylinositol 3-Kinases; D020169:Caspases; D002945:Cisplatin; D006918:Hydroxyurea; D008727:Methotrexate