title: Mitochondrial localization and pro-apoptotic effects of the interferon-inducible protein ISG12a.
abstract: ISG12a is one of the most highly induced genes following treatment of cells with type I interferons (IFNs). The encoded protein belongs to a family of poorly characterized, low molecular weight IFN-inducible proteins that includes 6-16 (G1P3), 1-8U (IFITM3), and 1-8D (IFITM2). Our studies demonstrate that the ISG12a protein associates with or inserts into the mitochondrial membrane. Transient expression of ISG12a led to decreased viable cell numbers and enhanced sensitivity to DNA-damage induced apoptosis, effects that were blocked by Bcl-2 co-expression or treatment with a pan-caspase inhibitor. ISG12a enhanced etoposide induced cytochrome c release, Bax activation and loss of mitochondrial membrane potential. siRNA-mediated inhibition of ectopic ISG12a protein expression prevented the sensitization to etoposide-induced apoptosis and also decreased the ability of IFN-beta pretreatment to sensitize cells to etoposide, thereby demonstrating a role for ISG12a in this process. These data suggest that ISG12a contributes to IFN-dependent perturbation of normal mitochondrial function, thus adding ISG12a to a growing list of IFN-induced proteins that impact cellular apoptosis.
authors.affiliation: Department of Biological Sciences, The University of Toledo, Toledo, OH 43606, USA.
authors.forename: Shaun
authors.initials: S
authors.lastname: Rosebeck
authors.forename: Douglas W
authors.initials: DW
authors.lastname: Leaman
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D005354:Fibrosarcoma / Q000648:ultrastructure; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*
chemical_list: C406887:IFI27 protein, human; D008565:Membrane Proteins; D020169:Caspases