title: Mcl-1 depletion in apoptosis elicited by ionizing radiation in peritoneal resident macrophages of C3H mice.
abstract: Remarkably, apoptosis was induced by exposing peritoneal resident macrophages (PRM) of C3H mice, but not other strains of mice, to ionizing radiation. The molecular mechanism of this strain-specific apoptosis in PRM was studied. The apoptosis elicited in C3H mouse PRM 4 h after exposure was effectively blocked by proteasome inhibitors. Irradiation-induced disruption of mitochondrial transmembrane potential and the release of cytochrome c into the cytosol were also suppressed by a proteasome inhibitor but not by a caspase inhibitor. To determine whether the apoptosis occurred due to a depletion of antiapoptotic proteins, Bcl-2 family proteins were examined. Irradiation markedly decreased the level of Mcl-1, but not Bcl-2, Bcl-X(L), Bax, A1, or cIAP1. Mcl-1's depletion was suppressed by a proteasome inhibitor but not by a caspase inhibitor. The amount of Mcl-1 was well correlated with the rate of apoptosis in C3H mouse PRM exposed to irradiation and not affected by irradiation in radioresistant B6 mouse PRM. Irradiation increased rather than decreased the Mcl-1 mRNA expression in C3H mouse PRM. On the other hand, Mcl-1 protein synthesis was markedly suppressed by irradiation. Global protein synthesis was also suppressed by irradiation in C3H mouse PRM but not in B6 mouse PRM. The down-regulation of Mcl-1 expression with Mcl-1-specific small interfering RNA or antisense oligonucleotide significantly induced apoptosis in both C3H and B6 mouse PRM without irradiation. It was concluded that the apoptosis elicited in C3H mouse PRM by ionizing radiation was attributable to the depletion of Mcl-1 through radiation-induced arrest of global protein synthesis.
authors.affiliation: Environmental and Toxicological Sciences Research Group, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan. y_kubota@nirs.go.jp
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Kubota
authors.forename: Keiji
authors.initials: K
authors.lastname: Kinoshita
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Suetomi
authors.forename: Akira
authors.initials: A
authors.lastname: Fujimori
authors.forename: Sentaro
authors.initials: S
authors.lastname: Takahashi
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology / Q000528:radiation effects*; D051017:Apoptosis Regulatory Proteins / Q000096:biosynthesis* / Q000276:immunology; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D045304:Cytochromes c / Q000276:immunology / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects / Q000276:immunology / Q000528:radiation effects*; D005260:Female; D005720:Gamma Rays; D017737:Macrophages, Peritoneal / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008809:Mice, Inbred C3H; D051336:Mitochondrial Membranes / Q000276:immunology / Q000378:metabolism; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D011480:Protease Inhibitors / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D014176:Protein Biosynthesis / Q000187:drug effects / Q000276:immunology / Q000528:radiation effects*; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering / Q000276:immunology / Q000494:pharmacology; D013045:Species Specificity
chemical_list: D051017:Apoptosis Regulatory Proteins; D061945:Caspase Inhibitors; C579094:Mcl1 protein, mouse; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D045304:Cytochromes c; D020169:Caspases; D046988:Proteasome Endopeptidase Complex