title: Evidence for microRNA-31 dependent Bim-Bax interaction preceding mitochondrial Bax translocation during radiation-induced apoptosis.
abstract: Downregulation of microRNA-31 has been linked with enhanced stress resistance, while its overexpression leads to cell death. In this study, we found mediatory role of microRNA-31 in γ-radiation-induced apoptosis in a model insect cell line Sf9 carrying well-conserved apoptotic machinery. Mature microRNA-31 is perfectly conserved amongst insects; hence we used biotinylated probes designed from Bombyx mori sequence for its successful detection in Sf9 cells. Target identification using Bombyx mori 3'UTRs predicted miR-31's potential role in Lepidopteran apoptosis, which prompted us to investigate alterations in its expression during radiation-induced cell death. We found significant overexpression of Sf-miR-31 following lethal dose (1,000Gy-3,000Gy) irradiation. Its mediatory role was finally confirmed as antisense-microRNA-31 could successfully inhibit radiation-induced cytochrome-c release, caspase-3 activation and apoptosis. While Bax/Bcl-2 expression remained unchanged, lethal radiation doses induced Bim overexpression and direct Bim-Bax interaction (co-immunoprecipitation) which is not yet unequivocally demonstrated during apoptosis. Quite important, these events were found to be dependent on radiation-induced miR-31 overexpression, as antisense-miR-31 inhibited both the responses and resulted in significant inhibition of cell death. Pro-apoptotic role of miR-31 was further confirmed when miR-31 mimic induced apoptosis involving similar Bim/Bax alterations. Therefore, our study reveals an important mediatory role of miR-31 in radiation-induced cell death.
authors.affiliation: Natural Radiation Response Mechanisms Group, Division of Radiation Biosciences, Institute of Nuclear Medicine &Allied Sciences, Brig. S.K. Mazumdar Road, Timarpur, Delhi-110054, India.
authors.forename: Ashish
authors.initials: A
authors.lastname: Kumar
authors.affiliation: Natural Radiation Response Mechanisms Group, Division of Radiation Biosciences, Institute of Nuclear Medicine &Allied Sciences, Brig. S.K. Mazumdar Road, Timarpur, Delhi-110054, India.
authors.forename: Soma
authors.initials: S
authors.lastname: Ghosh
authors.affiliation: Natural Radiation Response Mechanisms Group, Division of Radiation Biosciences, Institute of Nuclear Medicine &Allied Sciences, Brig. S.K. Mazumdar Road, Timarpur, Delhi-110054, India.
authors.forename: Sudhir
authors.initials: S
authors.lastname: Chandna
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D017209:Apoptosis / Q000528:radiation effects*; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D000072224:Bcl-2-Like Protein 11; D053148:Caspase 3 / Q000378:metabolism; D016000:Cluster Analysis; D045304:Cytochromes c / Q000378:metabolism; D005720:Gamma Rays; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D035683:MicroRNAs / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D016376:Oligonucleotides, Antisense / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D061987:Sf9 Cells; D018411:Spodoptera; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D020413:3' Untranslated Regions; D051017:Apoptosis Regulatory Proteins; D000072224:Bcl-2-Like Protein 11; D008565:Membrane Proteins; D035683:MicroRNAs; D016376:Oligonucleotides, Antisense; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D045304:Cytochromes c; D053148:Caspase 3