title: The Non-structural Protein of Crimean-Congo Hemorrhagic Fever Virus Disrupts the Mitochondrial Membrane Potential and Induces Apoptosis.
abstract: Viruses have developed distinct strategies to overcome the host defense system. Regulation of apoptosis in response to viral infection is important for virus survival and dissemination. Like other viruses, Crimean-Congo hemorrhagic fever virus (CCHFV) is known to regulate apoptosis. This study, for the first time, suggests that the non-structural protein NSs of CCHFV, a member of the genus Nairovirus, induces apoptosis. In this report, we demonstrated the expression of CCHFV NSs, which contains 150 amino acid residues, in CCHFV-infected cells. CCHFV NSs undergoes active degradation during infection. We further demonstrated that ectopic expression of CCHFV NSs induces apoptosis, as reflected by caspase-3/7 activity and cleaved poly(ADP-ribose) polymerase, in different cell lines that support CCHFV replication. Using specific inhibitors, we showed that CCHFV NSs induces apoptosis via both intrinsic and extrinsic pathways. The minimal active region of the CCHFV NSs protein was determined to be 93-140 amino acid residues. Using alanine scanning, we demonstrated that Leu-127 and Leu-135 are the key residues for NSs-induced apoptosis. Interestingly, CCHFV NSs co-localizes in mitochondria and also disrupts the mitochondrial membrane potential. We also demonstrated that Leu-127 and Leu-135 are important residues for disruption of the mitochondrial membrane potential by NSs. Therefore, these results indicate that the C terminus of CCHFV NSs triggers mitochondrial membrane permeabilization, leading to activation of caspases, which, ultimately, leads to apoptosis. Given that multiple factors contribute to apoptosis during CCHFV infection, further studies are needed to define the involvement of CCHFV NSs in regulating apoptosis in infected cells.
authors.affiliation: From the Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, Singapore, the Institute of Molecular and Cell Biology, Agency for Science, Technology, and Research, Singapore.
authors.forename: Bhaskar
authors.initials: B
authors.lastname: Barnwal
authors.affiliation: the Public Health Agency of Sweden, 17182 Solna, Sweden.
authors.forename: Helen
authors.initials: H
authors.lastname: Karlberg
authors.affiliation: the Public Health Agency of Sweden, 17182 Solna, Sweden, the Karolinska Institute, 17177 Stockholm, Sweden, and the National Veterinary Institute, 75651 Uppsala, Sweden.
authors.forename: Ali
authors.initials: A
authors.lastname: Mirazimi
authors.affiliation: From the Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, Singapore, the Institute of Molecular and Cell Biology, Agency for Science, Technology, and Research, Singapore, Yee_Joo_TAN@NUHS.edu.sg.
authors.forename: Yee-Joo
authors.initials: YJ
authors.lastname: Tan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D003225:Hemorrhagic Fever Virus, Crimean-Congo / Q000737:chemistry*; D006479:Hemorrhagic Fever, Crimean / Q000821:virology; D006801:Humans; D007930:Leucine / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects*; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection; D017361:Viral Nonstructural Proteins / Q000737:chemistry / Q000494:pharmacology*; D014779:Virus Replication / Q000187:drug effects
chemical_list: D050505:Mutant Proteins; D017361:Viral Nonstructural Proteins; D007930:Leucine
keywords: Crimean-Congo hemorrhagic fever virus; apoptosis; caspase; mitochondria; mitochondrial membrane potential; non-structural protein; proteasome