title: Bim(L) displacing Bcl-x(L) promotes Bax translocation during TNFalpha-induced apoptosis.
abstract: Bcl-2 family proteins are implicated as essential regulators in tumor necrosis factor-alpha (TNFalpha)-induced apoptosis. Bim(L), a BH3-only member of Bcl-2 family, can directly or indirectly activate the proapoptotic Bax and the subsequent mitochondrial apoptotic pathway. However, the molecular mechanism of Bim(L) activating Bax activation during TNFalpha-induced apoptosis is not fully understood. In this study, the role of Bim(L) in Bax activation during TNFalpha-induced apoptosis was investigated in differentiated PC12 and MCF7 cells, with real-time single-cell analysis. The experimental results show that Bax translocated to mitochondria and cytochrome c (Cyt c) released from mitochondria after TNFalpha treatment. Furthermore, SP600125 (specific inhibitor of JNK) could inhibit the Cyt c release from mitochondria. Co-immunoprecipitation results show that, the interaction between Bcl-x(L) and Bax decreased after TNFalpha treatment, while that between Bcl-x(L) and Bim(L) increased. Bax did not co-immunoprecipitate with Bim(L) before or after the TNFalpha treatment. In addition, the increased interaction between Bim(L) and Bcl-x(L) was dynamically monitored by using fluorescence resonance energy transfer (FRET) technique. Most importantly, there was no evidence of Bim(L) redistribution to mitochondria until cell apoptosis. By comprehensively analyzing these data, it is concluded that Bim(L) displaces Bcl-x(L) in the mitochondria and promotes Bax translocation during TNFalpha-induced apoptosis.
authors.affiliation: MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, South China Normal University, Guangzhou 510631, China.
authors.forename: Lan
authors.initials: L
authors.lastname: Zhang
authors.forename: Da
authors.initials: D
authors.lastname: Xing
authors.forename: Miaojuan
authors.initials: M
authors.lastname: Chen
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D000072224:Bcl-2-Like Protein 11; D001693:Biological Transport, Active / Q000187:drug effects; D045744:Cell Line, Tumor; D045304:Cytochromes c / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D016716:PC12 Cells; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology*; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism*; D051020:bcl-X Protein / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; C494826:BAX protein, human; C494811:BCL2L1 protein, human; C000606775:BCL2L11 protein, human; C494828:Bax protein, rat; D000072224:Bcl-2-Like Protein 11; C494813:Bcl2l1 protein, rat; C000606778:Bcl2l11 protein, rat; D017931:DNA Primers; D008164:Luminescent Proteins; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D014409:Tumor Necrosis Factor-alpha; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D045304:Cytochromes c