title: RanBPM has proapoptotic activities that regulate cell death pathways in response to DNA damage.
abstract: Ran-binding protein M (RanBPM) is a nucleocytoplasmic protein previously implicated in various signaling pathways, but whose function remains enigmatic. Here, we provide evidence that RanBPM functions as an activator of apoptotic pathways induced by DNA damage. First, transient expression of RanBPM in HeLa cells induced cell death through caspase activation, and in the long-term, forced expression of RanBPM impaired cell viability. RanBPM COOH-terminal domain stimulated the ability of RanBPM to induce caspase activation, whereas this activity was negatively regulated by the central SPRY domain. Second, small interfering RNA-directed knockdown of RanBPM prevented DNA damage-induced apoptosis, as evidenced by the marked reduction in caspase-3 and caspase-2 activation. This correlated with a magnitude fold increase in the survival of RanBPM-depleted cells. Following ionizing radiation treatment, we observed a progressive relocalization of RanBPM from the nucleus to the cytoplasm, suggesting that the activation of apoptotic pathways by RanBPM in response to ionizing radiation may be regulated by nucleocytoplasmic trafficking. Finally, RanBPM downregulation was associated with a marked decrease of mitochondria-associated Bax, whereas Bcl-2 overall levels were dramatically upregulated. Overall, our results reveal a novel proapoptotic function for RanBPM in DNA damage-induced apoptosis through the regulation of factors involved in the mitochondrial apoptotic pathway.
authors.affiliation: Robarts Research Institute, London, Ontario, Canada N6A 5K8.
authors.forename: Elnaz
authors.initials: E
authors.lastname: Atabakhsh
authors.forename: Dawn M
authors.initials: DM
authors.lastname: Bryce
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Lefebvre
authors.forename: Caroline
authors.initials: C
authors.lastname: Schild-Poulter
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017209:Apoptosis / Q000528:radiation effects; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage; D015536:Down-Regulation / Q000528:radiation effects; D004789:Enzyme Activation / Q000528:radiation effects; D006801:Humans; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000528:radiation effects; D011839:Radiation, Ionizing; D017384:Sequence Deletion; D015398:Signal Transduction / Q000528:radiation effects; D013347:Subcellular Fractions / Q000378:metabolism / Q000528:radiation effects; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D003598:Cytoskeletal Proteins; D009687:Nuclear Proteins; C116005:Ran binding protein 9; D051028:bcl-2-Associated X Protein; D020169:Caspases