title: GSIV serine/threonine kinase can induce apoptotic cell death via p53 and pro-apoptotic gene Bax upregulation in fish cells.
abstract: Previous studies have shown that GSIV induces apoptotic cell death through upregulation of the pro-apoptotic genes Bax and Bak in Grouper fin cells (GF-1 cells). However, the role of viral genome-encoded protein(s) in this death process remains unknown. In this study, we demonstrated that the Giant seaperch iridovirus (GSIV) genome encoded a serine/threonine kinase (ST kinase) protein, and induced apoptotic cell death via a p53-mediated Bax upregulation approach and a downregulation of Bcl-2 in fish cells. The ST kinase expression profile was identified through Western blot analyses, which indicated that expression started at day 1 h post-infection (PI), increased up to day 3, and then decreased by day 5 PI. This profile indicated the role of ST kinase expression during the early and middle phases of viral replication. We then cloned the ST kinase gene and tested its function in fish cells. The ST kinase was transiently expressed and used to investigate possible novel protein functions. The transient expression of ST kinase in GF-1 cells resulted in apoptotic cell features, as revealed with Terminal deoxynucleotidyl transferase biotin-dUTP nick-end labeling (TUNEL) assays and Hoechst 33258 staining at 24 h (37 %) and 48 h post-transfection (PT) (49 %). Then, through studies on the mechanism of cell death, we found that ST kinase overexpression could upregulate the anti-stress gene p53 and the pro-apoptotic gene Bax at 48 h PT. Interestingly, this upregulation of p53 and Bax also correlated to alterations in the mitochondria function that induced loss of mitochondrial membrane potential (MMP) and activated the initiator caspase-9 and the effector caspase-3 in the downstream. Moreover, when the p53-dependent transcriptional downstream gene was blocked by a specific transcriptional inhibitor, it was found that pifithrin-α not only reduced Bax expression, but also averted cell death in GF-1 cells during the ST kinase overexpression. Taken altogether, these results suggested that aquatic GSIV ST kinase could induce apoptosis via upregulation of p53 and Bax expression, resulting in mitochondrial disruption, which activated a downstream caspases-mediated cell death pathway.
authors.affiliation: Laboratory of Molecular Virology and Biotechnology, Institute of Biotechnology, Department of Biotechnology and Bioindustry Sciences, National Cheng Kung University, No 1. University Road, Tainan City, 701, Taiwan, ROC.|Department of Life Sciences, College of Bioscience and Biotechnology, National Cheng Kung University, No. 1. University Road, Tainan City, 701, Taiwan, ROC.
authors.forename: Latif
authors.initials: L
authors.lastname: Reshi
authors.affiliation: Laboratory Department of Food Science and Technology, Chin Nan University of Pharmacy and Science, Tainan, 717, Taiwan, ROC.
authors.forename: Horng-Cherng
authors.initials: HC
authors.lastname: Wu
authors.affiliation: Laboratory of Marine Molecular Biology and Biotechnology, Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, 115, Taiwan, ROC.
authors.forename: Jen-Leih
authors.initials: JL
authors.lastname: Wu
authors.affiliation: Department of Life Sciences, College of Bioscience and Biotechnology, National Cheng Kung University, No. 1. University Road, Tainan City, 701, Taiwan, ROC.
authors.forename: Hao-Ven
authors.initials: HV
authors.lastname: Wang
authors.affiliation: Laboratory of Molecular Virology and Biotechnology, Institute of Biotechnology, Department of Biotechnology and Bioindustry Sciences, National Cheng Kung University, No 1. University Road, Tainan City, 701, Taiwan, ROC. jrhong@mail.ncku.edu.tw.
authors.forename: Jiann-Ruey
authors.initials: JR
authors.lastname: Hong
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000502:physiology*; D001492:Bass; D052160:Benzothiazoles / Q000494:pharmacology; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D002460:Cell Line; D004789:Enzyme Activation; D020287:In Situ Nick-End Labeling; D017994:Iridovirus / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D053078:Membrane Potential, Mitochondrial / Q000502:physiology*; D008928:Mitochondria / Q000473:pathology*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D014050:Toluene / Q000031:analogs & derivatives / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis*; D051028:bcl-2-Associated X Protein / Q000096:biosynthesis*
chemical_list: D052160:Benzothiazoles; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D014050:Toluene; C121565:pifithrin; D017346:Protein Serine-Threonine Kinases; D053148:Caspase 3; D053453:Caspase 9
keywords: Bax; Grouper sea preach virus; Mitochondrial membrane potential loss; Serine/threonine kinase; Upregulation; p53