title: Bcl-XL is required for heme synthesis during the chemical induction of erythroid differentiation of murine erythroleukemia cells independently of its antiapoptotic function.
abstract: Bcl-X(L) is essential for the survival and normal maturation of erythroid cells, especially at the late stage of erythroid differentiation. It remains unclear whether Bcl-X(L) serves only as a survival factor for erythroid cells or if it can induce a signal for differentiation. We have previously shown that dimethyl sulfoxide (DMSO) induction of erythroid differentiation in murine erythroleukemia (MEL) cells correlates with delay of apoptosis and specific induction of Bcl-X(L). In this study, we investigate the contribution of Bcl-2 and Bcl-X(L) to survival and erythroid differentiation by generating stable MEL transfectants expressing these antiapoptotic regulators. Overexpression of Bcl-2 completely prevented apoptosis of MEL cells before and after DMSO induction, whereas overexpression of Bcl-X(L) only delayed it. Overexpression of Bcl-2 or Bcl-X(L) neither induced spontaneous erythroid differentiation nor accelerated DMSO-induced differentiation. Inhibition of Bcl-X(L) by antisense transcripts accelerated apoptosis in DMSO-treated MEL cells and blocked the synthesis of hemoglobin without altering the growth arrest associated with terminal erythroid differentiation. An antisense oligonucleotide to Bcl-X(L) did not induce apoptosis in MEL cells overexpressing Bcl-2 but greatly decreased their hemoglobin synthesis when treated with DMSO, suggesting that Bcl-X(L) is necessary for erythroid differentiation independently of its antiapoptotic function. Importantly, Bcl-X(L) antisense transcripts prevented heme synthesis but not globin mRNA induction in DMSO-treated MEL cells. Furthermore, inhibition of hemoglobin synthesis by Bcl-X(L) antisense was reversed by addition of exogenous hemin. Finally, Bcl-X(L) localized to mitochondria during MEL erythroid differentiation, suggesting that it may mediate a critical mitochondrial transport function related to heme biosynthesis.
authors.affiliation: INSERM U268-Hôpital Paul-Brousse, Villejuif, France.
authors.forename: Khalid
authors.initials: K
authors.lastname: Hafid-Medheb
authors.forename: Yvette
authors.initials: Y
authors.lastname: Augery-Bourget
authors.forename: Marie-Nathalie
authors.initials: MN
authors.lastname: Minatchy
authors.forename: Nicole
authors.initials: N
authors.lastname: Hanania
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Robert-Lézénès
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004912:Erythrocytes / Q000166:cytology*; D006418:Heme / Q000096:biosynthesis*; D006454:Hemoglobins / Q000096:biosynthesis / Q000187:drug effects; D004915:Leukemia, Erythroblastic, Acute / Q000473:pathology*; D051379:Mice; D020320:Oligoribonucleotides, Antisense / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014162:Transfection; D014407:Tumor Cells, Cultured; D051020:bcl-X Protein
chemical_list: C494812:Bcl2l1 protein, mouse; D006454:Hemoglobins; D020320:Oligoribonucleotides, Antisense; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D006418:Heme; D004121:Dimethyl Sulfoxide