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Apoptosis or Antiapoptosis? Interrupted Regulated Cell Death of Host Cells by Ascovirus Infection In Vitro. mBio 2023; 14:e0311922. [PMID: 36744941 PMCID: PMC9973268 DOI: 10.1128/mbio.03119-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Ascoviruses are insect-specific viruses thought to utilize the cellular apoptotic processes of host larvae to produce numerous virion-containing vesicles. In this study, we first determined the biochemical characteristics of ascovirus-infected, in vitro-cultured insect cells and the possible antiapoptotic capacity of ascovirus-infected insect cells. The results indicated that the ascovirus infection in the first 24 h was different from the infection from 48 h to the later infection stages. In the early infection stage, the Spodoptera exigua host cells had high membrane permeability and cleaved gasdermin D (GSDMD) but uncleaved Casp-6 (SeCasp-6). In contrast, the later infection stage had no such increased membrane permeability and had cleaved SeCasp-6. Four different chemicals were used to induce apoptosis at different stages of ascovirus infection: hydrogen peroxide (H2O2) and actinomycin D (ActD) had similar effects on the ascovirus-infected cells, whereas cMYC inhibitors and tumor necrosis factor alpha (TNF-α) plus SM-164 apoptosis inducers (T/S) had similar effects on infected cells. The former two inducers inhibited viral DNA replication in most situations, while the latter two inducers inhibited viral DNA replication in the early stage of infection but promoted viral DNA replication in the later infection stage. Furthermore, immunoblotting assays verified that T/S treatment could increase the expression levels of viral major capsid protein (MCP) and the host inhibitor of apoptosis protein (SeIAP). Coimmunoprecipitation assays revealed interaction between SeIAP and SeCasps, but this interaction was disturbed in ascovirus-infected cells. This study details the in vitro infection process of ascovirus, indicating the utilization of pyroptosis for antiapoptosis cytopathology. IMPORTANCE Clarifying the relationship between different types of viral infections and host regulation of cell death (RCD) can provide insights into the interaction between viruses and host cells. Ascoviruses are insect-specific viruses with apoptosis-utilizing-like infection cytopathology. However, RCD does not only include apoptosis, and while in our previous transmission electron microscopic observations, ascovirus-infected cells did not show typical apoptotic characteristics (unpublished data), in this study, they did show increased membrane permeability. These results indicate that the cytopathology of ascovirus infection is a complex process in which the virus manipulates host RCD. The RCD of insect cells is quite different from that of mammals, and studies on the former are many fewer than those on the latter, especially in the case of RCD in lepidopteran insects. Our results will lay a foundation for understanding the RCD of lepidopteran insects and its function in the process of insect virus infection.
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Dhani S, Zhao Y, Zhivotovsky B. A long way to go: caspase inhibitors in clinical use. Cell Death Dis 2021; 12:949. [PMID: 34654807 PMCID: PMC8519909 DOI: 10.1038/s41419-021-04240-3] [Citation(s) in RCA: 59] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2021] [Revised: 09/15/2021] [Accepted: 09/28/2021] [Indexed: 12/19/2022]
Abstract
Caspases are an evolutionary conserved family of cysteine-dependent proteases that are involved in many vital cellular processes including apoptosis, proliferation, differentiation and inflammatory response. Dysregulation of caspase-mediated apoptosis and inflammation has been linked to the pathogenesis of various diseases such as inflammatory diseases, neurological disorders, metabolic diseases, and cancer. Multiple caspase inhibitors have been designed and synthesized as a potential therapeutic tool for the treatment of cell death-related pathologies. However, only a few have progressed to clinical trials because of the consistent challenges faced amongst the different types of caspase inhibitors used for the treatment of the various pathologies, namely an inadequate efficacy, poor target specificity, or adverse side effects. Importantly, a large proportion of this failure lies in the lack of understanding various caspase functions. To overcome the current challenges, further studies on understanding caspase function in a disease model is a fundamental requirement to effectively develop their inhibitors as a treatment for the different pathologies. Therefore, the present review focuses on the descriptive properties and characteristics of caspase inhibitors known to date, and their therapeutic application in animal and clinical studies. In addition, a brief discussion on the achievements, and current challenges faced, are presented in support to providing more perspectives for further development of successful therapeutic caspase inhibitors for various diseases.
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Affiliation(s)
- Shanel Dhani
- Institute of Environmental Medicine, Karolinska Institutet, Box 210, 17177, Stockholm, Sweden
| | - Yun Zhao
- Institute of Environmental Medicine, Karolinska Institutet, Box 210, 17177, Stockholm, Sweden
| | - Boris Zhivotovsky
- Institute of Environmental Medicine, Karolinska Institutet, Box 210, 17177, Stockholm, Sweden.
- Faculty of Medicine, MV Lomonosov Moscow State University, 119991, Moscow, Russia.
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Rahmani S, Bandani AR. Caspase gene silencing affects the growth and development of Tuta absoluta. BIOCATALYSIS AND AGRICULTURAL BIOTECHNOLOGY 2021. [DOI: 10.1016/j.bcab.2021.102044] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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4
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Identification and Functional Analysis of Apoptotic Protease Activating Factor-1 (Apaf-1) from Spodoptera litura. INSECTS 2021; 12:insects12010064. [PMID: 33450838 PMCID: PMC7828216 DOI: 10.3390/insects12010064] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 01/10/2021] [Accepted: 01/10/2021] [Indexed: 11/17/2022]
Abstract
Apoptotic protease activating factor-1 (Apaf-1) is an adaptor molecule, essential for activating initiator caspase and downstream effector caspases, which directly cause apoptosis. In fruit flies, nematodes, and mammals, Apaf-1 has been extensively studied. However, the structure and function of Apaf-1 in Lepidoptera remain unclear. This study identified a novel Apaf-1 from Spodoptera litura, named Sl-Apaf-1. Sl-Apaf-1 contains three domains: a CARD domain, as well as NOD and WD motifs, and is very similar to mammalian Apaf-1. Interference of Sl-apaf-1 expression in SL-1 cells blocked apoptosis induced by actinomycin D. Overexpression of Sl-apaf-1 significantly enhances apoptosis induced by actinomycin D in Sf9/SL-1/U2OS cells, suggesting that the function of Sl-Apaf-1 is evolutionarily conserved. Furthermore, Sl-Apaf-1 could interact with Sl-caspase-5 (a homologue of mammalian caspase-9) and yielded a binding affinity of 1.37 × 106 M-1 according isothermal titration calorimetry assay. Initiator caspase (procaspase-5) of S. litura could be activated by Sl-Apaf-1 (without WD motif) in vitro, and the activated Sl-caspase-5 could cleave Sl-procaspase-1 (a homologue of caspase-3 in mammals), which directly caused apoptosis. This study demonstrates the key role of Sl-Apaf-1 in the apoptosis pathway, suggesting that the apoptosis pathway in Lepidopteran insects and mammals is conserved.
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Liu H, Zhou K, Yang Z. Identification and functional characterization of SlDronc in Spodoptera littoralis. PeerJ 2020; 8:e10329. [PMID: 33194452 PMCID: PMC7646310 DOI: 10.7717/peerj.10329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 10/19/2020] [Indexed: 11/20/2022] Open
Abstract
Background Apoptosis is responsible for eliminating damaged and virus-infected cells, regulating normal cell turnover, and maintaining the immune system’s development and function. Caspases play a vital role in both mammal and invertebrate apoptosis. Spodoptera littoralis is a generalist insect herbivore that is one of the most destructive pests in tropical and subtropical areas and attacks a wide range of commercially important crops. Although S. littoralis is a model organism in the study of baculovirus infection, its apoptotic pathway has not been explored. Methods We cloned a new caspase gene named sldronc in S. littoralis using Rapid Amplification of cDNA Ends (RACE). We then measured caspase activity on synthetic caspase substrates and S. littoralis’ effector caspase. SlDronc’s function in the apoptotic pathway and its interaction with caspase inhibitors were also tested in SL2 cells. Results We found that the initiator caspase SlDronc cleaved and activated effector caspase in S. littoralis. SlDronc overexpression induced apoptosis in SL2 cells, and Sldronc knockdown decreased apoptosis induced by UV irradiation in SL2 cells. Our results indicate that SlDronc acts as an apoptotic initiator caspase in S. littoralis. Additionally, we found that processed forms of SlDronc increased in the presence of N-terminally truncated S. littoralis inhibitors of apoptosis (SlIAP) and that SlDronc was inhibited by P49. This study contributes to the further understanding of S. littoralis’ apoptotic pathway and may facilitate future studies on baculovirus infection-induced apoptosis.
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Affiliation(s)
- Hao Liu
- State Key Laboratory of Virology, Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, China
| | - Ke Zhou
- State Key Laboratory of Virology, Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, China
| | - Zhouning Yang
- State Key Laboratory of Virology, Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, China
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6
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[Anti-viral responses in insect cells]. Uirusu 2019; 69:47-60. [PMID: 32938894 DOI: 10.2222/jsv.69.47] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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7
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Kong M, Zuo H, Zhu F, Hu Z, Chen L, Yang Y, Lv P, Yao Q, Chen K. The interaction between baculoviruses and their insect hosts. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2018; 83:114-123. [PMID: 29408049 DOI: 10.1016/j.dci.2018.01.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Revised: 01/26/2018] [Accepted: 01/26/2018] [Indexed: 06/07/2023]
Abstract
Baculoviruses are double-stranded circular DNA viruses that infect arthropods via the midgut. Because of their superiority as eukaryotic expression systems and their importance as biopesticides, extensive research on the functions of baculovirus genes as well as on the host response to baculovirus infection has been carried out, including transcriptomic and proteomic analyses of the midgut. The morphological and cellular changes caused by baculovirus infection are also important to better understand the infection pathway. Thanks to these previous studies, we now have a clearer picture of the mechanisms of action of the virus and of host immunity. In this paper, we systematically reviewed studies on the interaction between baculoviruses and their insect hosts. By better understanding these interactions, baculoviruses can be developed for use as more efficient biopesticides to improve agricultural development in the future.
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Affiliation(s)
- Ming Kong
- Institute of Life Sciences, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Huan Zuo
- Institute of Life Sciences, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Feifei Zhu
- Institute of Life Sciences, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Zhaoyang Hu
- Institute of Life Sciences, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Liang Chen
- Institute of Life Sciences, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Yanhua Yang
- Institute of Life Sciences, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Peng Lv
- Institute of Life Sciences, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Qin Yao
- Institute of Life Sciences, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Keping Chen
- Institute of Life Sciences, Jiangsu University, Zhenjiang, Jiangsu 212013, China.
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Wang Z, Xia X, Yang X, Zhang X, Liu Y, Wu D, Fang Y, Liu Y, Xu J, Qiu Y, Zhou X. A picorna-like virus suppresses the N-end rule pathway to inhibit apoptosis. eLife 2017; 6:30590. [PMID: 29231806 PMCID: PMC5739542 DOI: 10.7554/elife.30590] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Accepted: 12/11/2017] [Indexed: 12/21/2022] Open
Abstract
The N-end rule pathway is an evolutionarily conserved proteolytic system that degrades proteins containing N-terminal degradation signals called N-degrons, and has emerged as a key regulator of various processes. Viruses manipulate diverse host pathways to facilitate viral replication and evade antiviral defenses. However, it remains unclear if viral infection has any impact on the N-end rule pathway. Here, using a picorna-like virus as a model, we found that viral infection promoted the accumulation of caspase-cleaved Drosophila inhibitor of apoptosis 1 (DIAP1) by inducing the degradation of N-terminal amidohydrolase 1 (NTAN1), a key N-end rule component that identifies N-degron to initiate the process. The virus-induced NTAN1 degradation is independent of polyubiquitylation but dependent on proteasome. Furthermore, the virus-induced N-end rule pathway suppression inhibits apoptosis and benefits viral replication. Thus, our findings demonstrate that a virus can suppress the N-end rule pathway, and uncover a new mechanism for virus to evade apoptosis.
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Affiliation(s)
- Zhaowei Wang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China.,State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Xiaoling Xia
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China.,State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China.,Guangzhou Key Laboratory of Insect Development Regulation and Application Research, Institute of Insect Science and Technology & School of Life Sciences, South China Normal University, Guangzhou, China
| | - Xueli Yang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China
| | - Xueyi Zhang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China.,State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Yongxiang Liu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China.,State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Di Wu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China.,State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Yuan Fang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China.,State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Yujie Liu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China.,State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Jiuyue Xu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Yang Qiu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Xi Zhou
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China.,State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
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Vaccinia Virus Encodes a Novel Inhibitor of Apoptosis That Associates with the Apoptosome. J Virol 2017; 91:JVI.01385-17. [PMID: 28904196 DOI: 10.1128/jvi.01385-17] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 09/08/2017] [Indexed: 12/29/2022] Open
Abstract
Apoptosis is an important antiviral host defense mechanism. Here we report the identification of a novel apoptosis inhibitor encoded by the vaccinia virus (VACV) M1L gene. M1L is absent in the attenuated modified vaccinia virus Ankara (MVA) strain of VACV, a strain that stimulates apoptosis in several types of immune cells. M1 expression increased the viability of MVA-infected THP-1 and Jurkat cells and reduced several biochemical hallmarks of apoptosis, such as PARP-1 and procaspase-3 cleavage. Furthermore, ectopic M1L expression decreased staurosporine-induced (intrinsic) apoptosis in HeLa cells. We then identified the molecular basis for M1 inhibitory function. M1 allowed mitochondrial depolarization but blocked procaspase-9 processing, suggesting that M1 targeted the apoptosome. In support of this model, we found that M1 promoted survival in Saccharomyces cerevisiae overexpressing human Apaf-1 and procaspase-9, critical components of the apoptosome, or overexpressing only conformationally active caspase-9. In mammalian cells, M1 coimmunoprecipitated with Apaf-1-procaspase-9 complexes. The current model is that M1 associates with and allows the formation of the apoptosome but prevents apoptotic functions of the apoptosome. The M1 protein features 14 predicted ankyrin (ANK) repeat domains, and M1 is the first ANK-containing protein reported to use this inhibitory strategy. Since ANK-containing proteins are encoded by many large DNA viruses and found in all domains of life, studies of M1 may lead to a better understanding of the roles of ANK proteins in virus-host interactions.IMPORTANCE Apoptosis selectively eliminates dangerous cells such as virus-infected cells. Poxviruses express apoptosis antagonists to neutralize this antiviral host defense. The vaccinia virus (VACV) M1 ankyrin (ANK) protein, a protein with no previously ascribed function, inhibits apoptosis. M1 interacts with the apoptosome and prevents procaspase-9 processing as well as downstream procaspase-3 cleavage in several cell types and under multiple conditions. M1 is the first poxviral protein reported to associate with and prevent the function of the apoptosome, giving a more detailed picture of the threats VACV encounters during infection. Dysregulation of apoptosis is associated with several human diseases. One potential treatment of apoptosis-related diseases is through the use of designed ANK repeat proteins (DARPins), similar to M1, as caspase inhibitors. Thus, the study of the novel antiapoptosis effects of M1 via apoptosome association will be helpful for understanding how to control apoptosis using either natural or synthetic molecules.
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Yang Z, Zhou K, Liu H, Wu A, Mei L, Liu Q. SfDredd, a Novel Initiator Caspase Possessing Activity on Effector Caspase Substrates in Spodoptera frugiperda. PLoS One 2016; 11:e0151016. [PMID: 26977926 PMCID: PMC4792459 DOI: 10.1371/journal.pone.0151016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 02/23/2016] [Indexed: 01/11/2023] Open
Abstract
Sf9, a cell line derived from Spodoptera frugiperda, is an ideal model organism for studying insect apoptosis. The first notable study that attempted to identify the apoptotic pathway in Sf9 was performed in 1997 and included the discovery of Sf-caspase-1, an effector caspase of Sf9. However, it was not until 2013 that the first initiator caspase in Sf9, SfDronc, was discovered, and the apoptotic pathway in Sf9 became clearer. In this study, we report another caspase of Sf9, SfDredd. SfDredd is highly similar to insect initiator caspase Dredd homologs. Experimentally, recombinant SfDredd underwent autocleavage and exhibited different efficiencies in cleavage of synthetic caspase substrates. This was attributed to its caspase activity for the predicted active site mutation blocked the above autocleavage and synthetic caspase substrates cleavage activity. SfDredd was capable of not only cleaving Sf-caspase-1 in vitro but also cleaving Sf-caspase-1 and inducing apoptosis when it was co-expressed with Sf-caspase-1 in Sf9 cells. The protein level of SfDredd was increased when Sf9 cells were treated by Actinomycin D, whereas silencing of SfDredd reduced apoptosis and Sf-caspase-1 cleavage induced by Actinomycin D treatment. These results clearly indicate that SfDredd functioned as an apoptotic initiator caspase. Apoptosis induced in Sf9 cells by overexpression of SfDredd alone was not as obvious as that induced by SfDronc alone, and the cleavage sites of Sf-caspase-1 for SfDredd and SfDronc are different. In addition, despite sharing a sequence homology with initiator caspases and possessing weak activity on initiator caspase substrates, SfDredd showed strong activity on effector caspase substrates, making it the only insect caspase reported so far functioning similar to human caspase-2 in this aspect. We believe that the discovery of SfDredd, and its different properties from SfDronc, will improve the understanding of apoptosis pathway in Sf9 cells.
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Affiliation(s)
- Zhouning Yang
- State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, People’s Republic of China
| | - Ke Zhou
- State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, People’s Republic of China
| | - Hao Liu
- State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, People’s Republic of China
| | - Andong Wu
- State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, People’s Republic of China
| | - Long Mei
- State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, People’s Republic of China
| | - Qingzhen Liu
- State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, People’s Republic of China
- * E-mail:
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Baculovirus Inhibitor-of-Apoptosis Op-IAP3 Blocks Apoptosis by Interaction with and Stabilization of a Host Insect Cellular IAP. J Virol 2015; 90:533-44. [PMID: 26491164 DOI: 10.1128/jvi.02320-15] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 10/14/2015] [Indexed: 12/18/2022] Open
Abstract
UNLABELLED Baculovirus-encoded inhibitor of apoptosis (IAP) proteins likely evolved from their host cell IAP homologs, which function as critical regulators of cell death. Despite their striking relatedness to cellular IAPs, including the conservation of two baculovirus IAP repeat (BIR) domains and a C-terminal RING, viral IAPs use an unresolved mechanism to suppress apoptosis in insects. To define this mechanism, we investigated Op-IAP3, the prototypical IAP from baculovirus OpMNPV. We found that Op-IAP3 forms a stable complex with SfIAP, the native, short-lived IAP of host insect Spodoptera frugiperda. Long-lived Op-IAP3 prevented virus-induced SfIAP degradation, which normally causes caspase activation and apoptosis. In uninfected cells, Op-IAP3 also increased SfIAP steady-state levels and extended SfIAP's half-life. Conversely, SfIAP stabilization was lost or reversed in the presence of mutated Op-IAP3 that was engineered for reduced stability. Thus, Op-IAP3 stabilizes SfIAP and preserves its antiapoptotic function. In contrast to SfIAP, Op-IAP3 failed to bind or inhibit native Spodoptera caspases. Furthermore, BIR mutations that abrogate binding of well-conserved IAP antagonists did not affect Op-IAP3's capacity to prevent virus-induced apoptosis. Remarkably, Op-IAP3 also failed to prevent apoptosis when endogenous SfIAP was ablated by RNA silencing. Thus, Op-IAP3 requires SfIAP as a cofactor. Our findings suggest a new model wherein Op-IAP3 interacts directly with SfIAP to maintain its intracellular level, thereby suppressing virus-induced apoptosis indirectly. Consistent with this model, Op-IAP3 has evolved an intrinsic stability that may serve to repress signal-induced turnover and autoubiquitination when bound to its targeted cellular IAP. IMPORTANCE The IAPs were first discovered in baculoviruses because of their potency for preventing apoptosis. However, the antiapoptotic mechanism of viral IAPs in host insects has been elusive. We show here that the prototypical viral IAP, Op-IAP3, blocks apoptosis indirectly by associating with unstable, autoubiquitinating host IAP in such a way that cellular IAP levels and antiapoptotic activities are maintained. This mechanism explains Op-IAP3's requirement for native cellular IAP as a cofactor and the dispensability of caspase inhibition. Viral IAP-mediated preservation of the host IAP homolog capitalizes on normal IAP-IAP interactions and is likely the result of viral IAP evolution in which degron-mediated destabilization and ubiquitination potential have been reduced. This mechanism illustrates another novel means by which DNA viruses incorporate host death regulators that are modified for resistance to host regulatory controls for the purpose of suppressing host cell apoptosis and acquiring replication advantages.
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Ishimwe E, Hodgson JJ, Clem RJ, Passarelli AL. Reaching the melting point: Degradative enzymes and protease inhibitors involved in baculovirus infection and dissemination. Virology 2015; 479-480:637-49. [PMID: 25724418 DOI: 10.1016/j.virol.2015.01.027] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2014] [Revised: 01/13/2015] [Accepted: 01/30/2015] [Indexed: 10/24/2022]
Abstract
Baculovirus infection of a host insect involves several steps, beginning with initiation of virus infection in the midgut, followed by dissemination of infection from the midgut to other tissues in the insect, and finally culminating in "melting" or liquefaction of the host, which allows for horizontal spread of infection to other insects. While all of the viral gene products are involved in ultimately reaching this dramatic infection endpoint, this review focuses on two particular types of baculovirus-encoded proteins: degradative enzymes and protease inhibitors. Neither of these types of proteins is commonly found in other virus families, but they both play important roles in baculovirus infection. The types of degradative enzymes and protease inhibitors encoded by baculoviruses are discussed, as are the roles of these proteins in the infection process.
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Affiliation(s)
- Egide Ishimwe
- Division of Biology, Kansas State University, 116 Ackert Hall, Manhattan, KS 66506-4901, United States
| | - Jeffrey J Hodgson
- Division of Biology, Kansas State University, 116 Ackert Hall, Manhattan, KS 66506-4901, United States
| | - Rollie J Clem
- Division of Biology, Kansas State University, 116 Ackert Hall, Manhattan, KS 66506-4901, United States.
| | - A Lorena Passarelli
- Division of Biology, Kansas State University, 116 Ackert Hall, Manhattan, KS 66506-4901, United States.
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13
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Gómez Valderrama J, Villamizar L. Baculovirus: Hospederos y especificidad. REVISTA COLOMBIANA DE BIOTECNOLOGÍA 2013. [DOI: 10.15446/rev.colomb.biote.v15n2.41273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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Novel apoptosis suppressor Apsup from the baculovirus Lymantria dispar multiple nucleopolyhedrovirus precludes apoptosis by preventing proteolytic processing of initiator caspase Dronc. J Virol 2013; 87:12925-34. [PMID: 24067961 DOI: 10.1128/jvi.02065-13] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We previously identified a novel baculovirus-encoded apoptosis suppressor, Apsup, from the baculovirus Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV). Apsup inhibits the apoptosis of L. dispar Ld652Y cells triggered by infection with p35-defective Autographa californica MNPV (vAcΔp35) and exposure to actinomycin D or UV light. Here, we examined the functional role of Apsup in apoptosis regulation in insect cells. Apsup prevented apoptosis and the proteolytic processing of L. dispar initiator caspase Dronc (Ld-Dronc) in Ld652Y cells triggered by overexpression of Ld-Dronc, LdMNPV inhibitor-of-apoptosis 3 (IAP3), or Hyphantria cunea MNPV IAP1. In vAcΔp35-infected apoptotic Ld652Y cells, Apsup restricted apoptosis induction and prevented processing of endogenous Ld-Dronc. Conversely, upon RNA interference (RNAi)-mediated silencing of apsup, LdMNPV-infected Ld652Y cells, which typically support high-titer virus replication, underwent apoptosis, accompanied by the processing of endogenous Ld-Dronc. Furthermore, endogenous Ld-Dronc coimmunoprecipitated with transiently expressed Apsup, indicating that Apsup physically interacts with Ld-Dronc. Apsup prevented the apoptosis of Sf9 cells triggered by vAcΔp35 infection but did not inhibit apoptosis or activation of caspase-3-like protease in vAcΔp35-infected Drosophila melanogaster S2 cells. Apsup also inhibited the proteolytic processing of L. dispar effector caspase Ld-caspase-1 in the transient expression assay but did not physically interact with Ld-caspase-1. These results demonstrate that Apsup inhibits apoptosis in Ld652Y cells by preventing the proteolytic processing of Ld-Dronc. Together with our previous findings showing that Apsup prevents the processing of both overexpressed Ld-Dronc and Bombyx mori Dronc, these results also demonstrate that Apsup functions as an effective apoptotic suppressor in various lepidopteran, but not dipteran, insect cells.
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Ying Z, Li A, Lu Z, Wu C, Yin H, Yuan M, Pang Y. The Spodoptera frugiperda effector caspase Sf-caspase-1 becomes unstable following its activation. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2013; 83:195-210. [PMID: 23740663 DOI: 10.1002/arch.21106] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Sf-caspase-1 is the principal effector caspase in Spodoptera frugiperda cells. Like the caspases in other organisms, Sf-caspase-1 is processed by upstream caspases to form an active heterotetramer composed of the p19 and p12 subunits. The regulation of active caspases is crucial for cellular viability. In mammal cells, the subunits and the active form of caspase-3 were rapidly degraded relative to its proenzyme form. In the present study, the S. frugiperda Sf9 cells were transiently transfected with plasmids encoding different fragments of Sf-caspase-1: the pro-Sf-caspase-1 (p37), a prodomain deleted fragment (p31), a fragment containing the large subunit and the prodomain (p25), the large subunit (p19), and the small subunit (p12). Flow cytometry and Western blot analysis revealed that p12, p19, and p25 were unstable in the transfected cells, in contrast to p37 and p31. Lactacystin, a proteasome inhibitor, increased the accumulation of the p19 and p12 subunits, suggesting that the degradation is performed by the ubiquitin-proteasome system. During the activation, the Sf-caspase-1 produces an intermediate form and then undergoes proteolytic processing to form active Sf-caspase-1. We found that both the active and the intermediate form were unstable, indicating that once activated or during its activation, the Sf-caspase-1 was unstable.
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Affiliation(s)
- Zhongfu Ying
- State Key Laboratory of Biocontrol, Sun Yat-sen University, Guangzhou, PR China
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16
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Huang N, Civciristov S, Hawkins CJ, Clem RJ. SfDronc, an initiator caspase involved in apoptosis in the fall armyworm Spodoptera frugiperda. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2013; 43:444-454. [PMID: 23474489 PMCID: PMC3640372 DOI: 10.1016/j.ibmb.2013.02.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 01/31/2013] [Accepted: 02/21/2013] [Indexed: 06/01/2023]
Abstract
Initiator caspases are the first caspases that are activated following an apoptotic stimulus, and are responsible for cleaving and activating downstream effector caspases, which directly cause apoptosis. We have cloned a cDNA encoding an ortholog of the initiator caspase Dronc in the lepidopteran insect Spodoptera frugiperda. The SfDronc cDNA encodes a predicted protein of 447 amino acids with a molecular weight of 51 kDa. Overexpression of SfDronc induced apoptosis in Sf9 cells, while partial silencing of SfDronc expression in Sf9 cells reduced apoptosis induced by baculovirus infection or by treatment with UV or actinomycin D. Recombinant SfDronc exhibited several expected biochemical characteristics of an apoptotic initiator caspase: 1) SfDronc efficiently cleaved synthetic initiator caspase substrates, but had very little activity against effector caspase substrates; 2) mutation of a predicted cleavage site at position D340 blocked autoprocessing of recombinant SfDronc and reduced enzyme activity by approximately 10-fold; 3) SfDronc cleaved the effector caspase Sf-caspase-1 at the expected cleavage site, resulting in Sf-caspase-1 activation; and 4) SfDronc was strongly inhibited by the baculovirus caspase inhibitor SpliP49, but not by the related protein AcP35. These results indicate that SfDronc is an initiator caspase involved in caspase-dependent apoptosis in S. frugiperda, and as such is likely to be responsible for the initiator caspase activity in S. frugiperda cells known as Sf-caspase-X.
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Affiliation(s)
- Ning Huang
- Molecular, Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66503
| | - Srgjan Civciristov
- Department of Biochemistry, La Trobe University, Bundoora 3086, Victoria, Australia
| | - Christine J. Hawkins
- Department of Biochemistry, La Trobe University, Bundoora 3086, Victoria, Australia
| | - Rollie J. Clem
- Molecular, Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66503
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Halder UC, Bhowmick R, Roy Mukherjee T, Nayak MK, Chawla-Sarkar M. Phosphorylation drives an apoptotic protein to activate antiapoptotic genes: paradigm of influenza A matrix 1 protein function. J Biol Chem 2013; 288:14554-14568. [PMID: 23548901 DOI: 10.1074/jbc.m112.447086] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
During infection, viral proteins target cellular pathways that regulate cellular innate immune responses and cell death. We demonstrate that influenza A virus matrix 1 protein (M1), an established proapoptotic protein, activates nuclear factor-κB member RelB-mediated survival genes (cIAP1, cIAP2, and cFLIP), a function that is linked with its nuclear translocation during early infection. Death domain-associated protein 6 (Daxx) is a transcription co-repressor of the RelB-responsive gene promoters. During influenza virus infection M1 binds to and stabilizes Daxx protein by preventing its ubiquitination and proteasomal degradation. Binding of M1 with Daxx through its Daxx binding motif prevents binding of RelB and Daxx, resulting in up-regulation of survival genes. This interaction also prevents promoter recruitment of DNA methyltransferases (Dnmt1 and Dnmt3a) and lowers CpG methylation of the survival gene promoters, leading to the activation of these genes. Thus, M1 prevents repressional function of Daxx during infection, thereby exerting a survival role. In addition to its nuclear localization signal, translocation of M1 to the nucleus depends on cellular kinase-mediated phosphorylation as the protein kinase C inhibitor calphostin C effectively down-regulates virus replication. The study reconciles the ambiguity of dual antagonistic function of viral protein and potentiates a possible target to limit virus infection.
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Affiliation(s)
- Umesh Chandra Halder
- Division of Virology, National Institute of Cholera and Enteric Diseases, P-33 C.I.T. Road, Scheme-XM, Beliaghata, Kolkata 700010, India
| | - Rahul Bhowmick
- Division of Virology, National Institute of Cholera and Enteric Diseases, P-33 C.I.T. Road, Scheme-XM, Beliaghata, Kolkata 700010, India
| | - Tapasi Roy Mukherjee
- Division of Virology, National Institute of Cholera and Enteric Diseases, P-33 C.I.T. Road, Scheme-XM, Beliaghata, Kolkata 700010, India
| | - Mukti Kant Nayak
- Department of Zoology, University of Calcutta, 35 Ballygunge Circular Road, Kolkata 700019, India
| | - Mamta Chawla-Sarkar
- Division of Virology, National Institute of Cholera and Enteric Diseases, P-33 C.I.T. Road, Scheme-XM, Beliaghata, Kolkata 700010, India.
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Ikeda M, Yamada H, Hamajima R, Kobayashi M. Baculovirus genes modulating intracellular innate antiviral immunity of lepidopteran insect cells. Virology 2013; 435:1-13. [DOI: 10.1016/j.virol.2012.10.016] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 10/08/2012] [Accepted: 10/08/2012] [Indexed: 12/11/2022]
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Monteiro F, Carinhas N, Carrondo MJT, Bernal V, Alves PM. Toward system-level understanding of baculovirus-host cell interactions: from molecular fundamental studies to large-scale proteomics approaches. Front Microbiol 2012; 3:391. [PMID: 23162544 PMCID: PMC3494084 DOI: 10.3389/fmicb.2012.00391] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 10/23/2012] [Indexed: 01/16/2023] Open
Abstract
Baculoviruses are insect viruses extensively exploited as eukaryotic protein expression vectors. Molecular biology studies have provided exciting discoveries on virus-host interactions, but the application of omic high-throughput techniques on the baculovirus-insect cell system has been hampered by the lack of host genome sequencing. While a broader, systems-level analysis of biological responses to infection is urgently needed, recent advances on proteomic studies have yielded new insights on the impact of infection on the host cell. These works are reviewed and critically assessed in the light of current biological knowledge of the molecular biology of baculoviruses and insect cells.
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Affiliation(s)
- Francisca Monteiro
- Animal Cell Technology Unit, Instituto de Biologia Experimental e Tecnológica Oeiras, Portugal ; Animal Cell Technology Unit, Instituto de Tecnologia Quimica e Biológica Oeiras, Portugal
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20
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Lai YK, Hsu JTA, Chu CC, Chang TY, Pan KL, Lin CC. Enhanced recombinant protein production and differential expression of molecular chaperones in sf-caspase-1-repressed stable cells after baculovirus infection. BMC Biotechnol 2012; 12:83. [PMID: 23134743 PMCID: PMC3505465 DOI: 10.1186/1472-6750-12-83] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Accepted: 11/04/2012] [Indexed: 12/27/2022] Open
Abstract
Background There are few studies that have examined the potential of RNA inference (RNAi) to increase protein production in the baculovirus expression vector system (BEVS). Spodoptera frugiperda (fall armyworm) (Sf)-caspase-1-repressed stable cells exhibit resistance to apoptosis and enhancement of recombinant protein production. However, the mechanism of recombinant protein augmentation in baculovirus-infected Caspase-repressed insect cells has not been elucidated. Results In the current study, we utilized RNAi-mediated Sf-caspase-1-repressed stable cells to clarify how the resistance to apoptosis can enhance both intracellular (firefly luciferase) and extracellular (secreted alkaline phosphatase [SEAP]) recombinant protein production in BEVS. Since the expression of molecular chaperones is strongly associated with the maximal production of exogenous proteins in BEVS, the differential expression of molecular chaperones in baculovirus-infected stable cells was also analyzed in this study. Conclusion The data indicated that the retention of expression of molecular chaperones in baculovirus-infected Sf-caspase-1-repressed stable cells give the higher recombinant protein accumulation.
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Affiliation(s)
- Yiu-Kay Lai
- Institute of Biotechnology, Department of Life Science, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan, R.O.C
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Baculoviruses modulate a proapoptotic DNA damage response to promote virus multiplication. J Virol 2012; 86:13542-53. [PMID: 23035220 DOI: 10.1128/jvi.02246-12] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The baculovirus Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) initiates apoptosis in diverse insects through events triggered by virus DNA (vDNA) replication. To define the proapoptotic pathway and its role in antivirus defense, we investigated the link between the host's DNA damage response (DDR) and apoptosis. We report here that AcMNPV elicits a DDR in the model insect Drosophila melanogaster. Replication of vDNA activated DDR kinases, as evidenced by ATM-driven phosphorylation of the Drosophila histone H2AX homolog (H2Av), a critical regulator of the DDR. Ablation or inhibition of ATM repressed H2Av phosphorylation and blocked virus-induced apoptosis. The DDR kinase inhibitors caffeine and KU55933 also prevented virus-induced apoptosis in cells derived from the permissive AcMNPV host, Spodoptera frugiperda. This block occurred at a step upstream of virus-mediated depletion of the cellular inhibitor-of-apoptosis protein, an event that initiates apoptosis in Spodoptera and Drosophila. Thus, the DDR is a conserved, proapoptotic response to baculovirus infection. DDR inhibition also repressed vDNA replication and reduced virus yields 100,000-fold, demonstrating that the DDR contributes to virus production, despite its recognized antivirus role. In contrast to virus-induced phosphorylation of Drosophila H2Av, AcMNPV blocked phosphorylation of the Spodoptera H2AX homolog (SfH2AX). Remarkably, AcMNPV also suppressed SfH2AX phosphorylation following pharmacologically induced DNA damage. These findings indicate that AcMNPV alters canonical DDR signaling in permissive cells. We conclude that AcMNPV triggers a proapoptotic DDR that is subsequently modified, presumably to stimulate vDNA replication. Thus, manipulation of the DDR to facilitate multiplication is an evolutionarily conserved strategy among DNA viruses of insects and mammals.
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22
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Brand IL, Civciristov S, Taylor NL, Talbo GH, Pantaki-Eimany D, Levina V, Clem RJ, Perugini MA, Kvansakul M, Hawkins CJ. Caspase inhibitors of the P35 family are more active when purified from yeast than bacteria. PLoS One 2012; 7:e39248. [PMID: 22720082 PMCID: PMC3375223 DOI: 10.1371/journal.pone.0039248] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Accepted: 05/22/2012] [Indexed: 11/19/2022] Open
Abstract
Many insect viruses express caspase inhibitors of the P35 superfamily, which prevent defensive host apoptosis to enable viral propagation. The prototypical P35 family member, AcP35 from Autographa californica M nucleopolyhedrovirus, has been extensively studied. Bacterially purified AcP35 has been previously shown to inhibit caspases from insect, mammalian and nematode species. This inhibition occurs via a pseudosubstrate mechanism involving caspase-mediated cleavage of a "reactive site loop" within the P35 protein, which ultimately leaves cleaved P35 covalently bound to the caspase's active site. We observed that AcP35 purifed from Saccharomyces cerevisae inhibited caspase activity more efficiently than AcP35 purified from Escherichia coli. This differential potency was more dramatic for another P35 family member, MaviP35, which inhibited human caspase 3 almost 300-fold more potently when purified from yeast than bacteria. Biophysical assays revealed that MaviP35 proteins produced in bacteria and yeast had similar primary and secondary structures. However, bacterially produced MaviP35 possessed greater thermal stability and propensity to form higher order oligomers than its counterpart purified from yeast. Caspase 3 could process yeast-purified MaviP35, but failed to detectably cleave bacterially purified MaviP35. These data suggest that bacterially produced P35 proteins adopt subtly different conformations from their yeast-expressed counterparts, which hinder caspase access to the reactive site loop to reduce the potency of caspase inhibition, and promote aggregation. These data highlight the differential caspase inhibition by recombinant P35 proteins purified from different sources, and caution that analyses of bacterially produced P35 family members (and perhaps other types of proteins) may underestimate their activity.
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Affiliation(s)
- Ingo L. Brand
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria, Australia
| | - Srgjan Civciristov
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria, Australia
| | - Nicole L. Taylor
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria, Australia
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria, Australia
| | - Gert H. Talbo
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria, Australia
| | - Delara Pantaki-Eimany
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria, Australia
| | - Vita Levina
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria, Australia
| | - Rollie J. Clem
- Division of Biology, Kansas State University, Manhattan, Kansas, United States of America
| | - Matthew A. Perugini
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria, Australia
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria, Australia
| | - Marc Kvansakul
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria, Australia
| | - Christine J. Hawkins
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria, Australia
- Murdoch Children's Research Institute, Royal Children's Hospital, Parkville, Australia
- * E-mail:
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Abstract
Viral infection constitutes an unwanted intrusion that needs to be eradicated by host cells. On one hand, one of the first protective barriers set up to prevent viral replication, spread or persistence involves the induction of apoptotic cell death that aims to limit the availability of the cellular components for viral amplification. On the other hand, while they completely depend on the host molecular machinery, viruses also need to evade the cellular responses that are meant to destroy them. The existence of numerous antiapoptotic products within the viral kingdom proves that apoptosis constitutes a major threat that should better be bypassed. Among the different strategies developed to deal with apoptosis, one is based on what viruses do best: backfiring the cell on itself. Several unrelated viruses have been described to take advantage of apoptosis induction by expressing proteins targeted by caspases, the key effectors of apoptotic cell death. Caspase cleavage of these proteins results in various consequences, from logical apoptosis inhibition to more surprising enhancement or attenuation of viral replication. The present review aims at discussing the characterization and relevance of this post-translational modification that adds a new complexity in the already intricate host-apoptosis-virus triangle.
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Brand IL, Green MM, Civciristov S, Pantaki-Eimany D, George C, Gort TR, Huang N, Clem RJ, Hawkins CJ. Functional and biochemical characterization of the baculovirus caspase inhibitor MaviP35. Cell Death Dis 2011; 2:e242. [PMID: 22170098 PMCID: PMC3252740 DOI: 10.1038/cddis.2011.127] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Many viruses express proteins which prevent the host cell death that their infection would otherwise provoke. Some insect viruses suppress host apoptosis through the expression of caspase inhibitors belonging to the P35 superfamily. Although a number of P35 relatives have been identified, Autographa californica (Ac) P35 and Spodoptera littoralis (Spli) P49 have been the most extensively characterized. AcP35 was found to inhibit caspases via a suicide substrate mechanism: the caspase cleaves AcP35 within its ‘reactive site loop' then becomes trapped, irreversibly bound to the cleaved inhibitor. The Maruca vitrata multiple nucleopolyhedrovirus encodes a P35 family member (MaviP35) that exhibits 81% identity to AcP35. We found that this relative shared with AcP35 the ability to inhibit mammalian and insect cell death. Caspase-mediated cleavage within the MaviP35 reactive site loop occurred at a sequence distinct from that in AcP35, and the inhibitory profiles of the two P35 relatives differed. MaviP35 potently inhibited human caspases 2 and 3, DCP-1, DRICE and CED-3 in vitro, but (in contrast to AcP35) only weakly suppressed the proteolytic activity of the initiator human caspases 8, 9 and 10. Although MaviP35 inhibited the AcP35-resistant caspase DRONC in yeast, and was sensitive to cleavage by DRONC in vitro, MaviP35 failed to inhibit the proteolytic activity of bacterially produced DRONC in vitro.
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Affiliation(s)
- I L Brand
- Department of Biochemistry, La Trobe University, Bundoora, Victoria, Australia
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Wang Y, Choi JY, Roh JY, Liu Q, Tao XY, Park JB, Kim JS, Je YH. Genomic sequence analysis of granulovirus isolated from the tobacco cutworm, Spodoptera litura. PLoS One 2011; 6:e28163. [PMID: 22132235 PMCID: PMC3223241 DOI: 10.1371/journal.pone.0028163] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Accepted: 11/02/2011] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Spodoptera litura is a noctuid moth that is considered an agricultural pest. The larvae feed on a wide range of plants and have been recorded on plants from 40 plant families (mostly dicotyledons). It is a major pest of many crops. To better understand Spodoptera litura granulovirus (SpliGV), the nucleotide sequence of the SpliGV DNA genome was determined and analyzed. METHODOLOGY/PRINCIPAL FINDINGS The genome of the SpliGV was completely sequenced. The nucleotide sequence of the SpliGV genome was 124,121 bp long with 61.2% A+T content and contained 133 putative open reading frames (ORFs) of 150 or more nucleotides. The 133 putative ORFs covered 86.3% of the genome. Among these, 31 ORFs were conserved in most completely sequenced baculovirus genomes, 38 were granulovirus (GV)-specific, and 64 were present in some nucleopolyhedroviruses (NPVs) and/or GVs. We proved that 9 of the ORFs were SpliGV specific. CONCLUSIONS/SIGNIFICANCE The genome of SpliGV is 124,121 bp in size. One hundred thirty-three ORFs that putatively encode proteins of 50 or more amino acid residues with minimal overlap were determined. No chitinase or cathepsin genes, which are involved in the liquefaction of the infected host, were found in the SpliGV genome, explaining why SpliGV-infected insects do not degrade in a typical manner. The DNA photolyase gene was first found in the genus Granulovirus. When phylogenic relationships were analyzed, the SpliGV was most closely related to Trichoplusia ni granulovirus (TnGV) and Xestia c-nigrum granulovirus (XecnGV), which belong to the Type I-granuloviruses (Type I-GV).
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Affiliation(s)
- Yong Wang
- Department of Agricultural Biotechnology, College of Agriculture and Life Sciences, Seoul National University, Seoul, Korea
| | - Jae Young Choi
- Department of Agricultural Biotechnology, College of Agriculture and Life Sciences, Seoul National University, Seoul, Korea
| | - Jong Yul Roh
- Department of Agricultural Biotechnology, College of Agriculture and Life Sciences, Seoul National University, Seoul, Korea
| | - Qin Liu
- Department of Agricultural Biotechnology, College of Agriculture and Life Sciences, Seoul National University, Seoul, Korea
| | - Xue Ying Tao
- Department of Agricultural Biotechnology, College of Agriculture and Life Sciences, Seoul National University, Seoul, Korea
| | - Jong Bin Park
- Department of Agricultural Biotechnology, College of Agriculture and Life Sciences, Seoul National University, Seoul, Korea
| | - Jae Su Kim
- Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul, Korea
| | - Yeon Ho Je
- Department of Agricultural Biotechnology, College of Agriculture and Life Sciences, Seoul National University, Seoul, Korea
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Suganuma I, Ushiyama T, Yamada H, Iwamoto A, Kobayashi M, Ikeda M. Cloning and characterization of a dronc homologue in the silkworm, Bombyx mori. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2011; 41:909-921. [PMID: 21911060 DOI: 10.1016/j.ibmb.2011.08.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Revised: 08/25/2011] [Accepted: 08/29/2011] [Indexed: 05/31/2023]
Abstract
We cloned and characterized a novel Bombyx mori homologue (bm-dronc) of Drosophila melanogaster dronc (dm-dronc), which could encode a polypeptide of 438 amino acid residues. Bm-Dronc shares relatively low amino acid sequence identities of 25% and 26% with Dm-Dronc and Aedes aegypti Dronc (Aa-Dronc), respectively. Bm-Dronc has the sequence QACRG surrounding the catalytic site (C), which is consistent with the QAC(R/Q/G)(G/E) consensus sequence in most caspases but distinct from the sequences PFCRG and SICRG of Dm-Dronc and Aa-Dronc, respectively. Bm-Dronc possesses a long N-terminal prodomain containing a caspase recruitment domain (CARD), a p20 domain and a p10 domain, exhibiting cleavage activities on synthetic substrates Ac-VDVAD-AMC, Ac-IETD-AMC and Ac-LEHD-AMC, which are preferred by human initiator caspases-2, -8 and -9, respectively. Bm-Dronc transiently expressed in insect cells and Escherichia coli cells underwent spontaneous cleavage and caused apoptosis and stimulation of caspase-3-like protease activity in various lepidopteran cell lines, but not in the dipteran cell line D. melanogaster S2. The apoptosis and the stimulation of caspase-3-like protease activity induced by Bm-Dronc overexpression were abrogated upon transfection with either a double-stranded RNA against bm-dronc or a plasmid expressing functional anti-apoptotic protein Hycu-IAP3 encoded by the baculovirus Hyphantria cunea multiple nucleopolyhedrovirus (MNPV). Apoptosis induction in BM-N cells by infection with a p35-defective Autographa californica MNPV or exposure to actinomycin D and UV promoted the cleavage of Bm-Dronc. These results indicate that Bm-Dronc serves as the initiator caspase responsible for the induction of caspase-dependent apoptosis.
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Affiliation(s)
- Ikue Suganuma
- Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan
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Courtiade J, Pauchet Y, Vogel H, Heckel DG. A comprehensive characterization of the caspase gene family in insects from the order Lepidoptera. BMC Genomics 2011; 12:357. [PMID: 21740565 PMCID: PMC3141678 DOI: 10.1186/1471-2164-12-357] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Accepted: 07/08/2011] [Indexed: 11/22/2022] Open
Abstract
Background The cell suicide pathway of apoptosis is a necessary event in the life of multicellular organisms. It is involved in many biological processes ranging from development to the immune response. Evolutionarily conserved proteases, called caspases, play a central role in regulating apoptosis. Reception of death stimuli triggers the activation of initiator caspases, which in turn activate the effector caspases. In Lepidoptera, apoptosis is crucial in processes such as metamorphosis or defending against baculovirus infection. The discovery of p35, a baculovirus protein inhibiting caspase activity, has led to the characterization of the first lepidopteran caspase, Sf-Caspase-1. Studies on Sf-Caspase-1 mode of activation suggested that apoptosis in Lepidoptera requires a cascade of caspase activation, as demonstrated in many other species. Results In order to get insights into this gene family in Lepidoptera, we performed an extensive survey of lepidopteran-derived EST datasets. We identified 66 sequences distributed among 27 species encoding putative caspases. Phylogenetic analyses showed that Lepidoptera possess at least 5 caspases, for which we propose a unified nomenclature. According to homology to their Drosophila counterparts and their primary structure, we determined that Lep-Caspase-1, -2 and -3 are putative effector caspases, whereas Lep-Caspase-5 and -6 are putative initiators. The likely function of Lep-Caspase-4 remains unclear. Lep-Caspase-2 is absent from the silkworm genome and appears to be noctuid-specific, and to have arisen from a tandem duplication of the Caspase-1 gene. In the tobacco hawkmoth, 3 distinct transcripts encoding putative Caspase-4 were identified, suggesting at least 2 duplication events in this species. Conclusions The basic repertoire of five major types of caspases shared among Lepidoptera seems to be smaller than for most other groups studied to date, but gene duplication still plays a role in lineage-specific increases in diversity, just as in Diptera and mammals.
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Affiliation(s)
- Juliette Courtiade
- Department of Entomology, Max Planck Institute for Chemical Ecology, Jena, Germany
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28
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van Domselaar R, Bovenschen N. Cell death-independent functions of granzymes: hit viruses where it hurts. Rev Med Virol 2011; 21:301-14. [PMID: 21714121 DOI: 10.1002/rmv.697] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2011] [Revised: 05/03/2011] [Accepted: 05/06/2011] [Indexed: 12/24/2022]
Abstract
Granule exocytosis by cytotoxic lymphocytes is the key mechanism of our immune response to eliminate virus-infected cells. These lytic granules contain the pore-forming protein perforin and a set of five serine proteases called granzymes (GrA, GrB, GrH, GrK, GrM) that display distinct substrate specificities. Granzymes have mostly been studied for their ability to induce cell death. However, viruses have evolved many inhibitors to effectively block apoptosis. Evidence is emerging that granzymes also use noncytotoxic strategies to inhibit viral replication and potential viral reactivation from latency. Granzymes directly cleave viral or host cell proteins that are required in the viral life cycle. Furthermore, granzymes induce a pro-inflammatory cytokine response to create an antiviral environment. In this review, we summarize and discuss these novel strategies by which the immune system counteracts viral infections, and we will address the potential therapeutic applications that could emerge from this intriguing mechanism.
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Affiliation(s)
- Robert van Domselaar
- Department of Pathology, University Medical Center Utrecht, Utrecht, the Netherlands
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Active depletion of host cell inhibitor-of-apoptosis proteins triggers apoptosis upon baculovirus DNA replication. J Virol 2011; 85:8348-58. [PMID: 21653668 DOI: 10.1128/jvi.00667-11] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Apoptosis is an important antivirus defense by virtue of its impact on virus multiplication and pathogenesis. To define molecular mechanisms by which viruses are detected and the apoptotic response is initiated, we examined the antiviral role of host inhibitor-of-apoptosis (IAP) proteins in insect cells. We report here that the principal IAPs, DIAP1 and SfIAP, of the model insects Drosophila melanogaster and Spodoptera frugiperda, respectively, are rapidly depleted and thereby inactivated upon infection with the apoptosis-inducing baculovirus Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV). Virus-induced loss of these host IAPs triggered caspase activation and apoptotic death. Elevation of IAP levels by ectopic expression repressed caspase activation. Loss of host IAP in both species was triggered by AcMNPV DNA replication. By using selected inhibitors, we found that virus-induced IAP depletion was mediated in part by the proteasome but not by caspase cleavage. Consistent with this conclusion, mutagenic disruption of the SfIAP RING motif, which acts as an E3 ubiquitin ligase, stabilized SfIAP during infection. Importantly, SfIAP was also stabilized upon the removal of its 99-residue N-terminal leader, which serves as a critical determinant of IAP turnover. These data indicated that a host pathway initiated by virus DNA replication and acting through instability motifs embedded within IAP triggers IAP depletion and thereby causes apoptosis. Taken together, the results of our study suggest that host modulation of cellular IAP levels is a conserved mechanism by which insects mount an apoptotic antiviral response. Thus, host IAPs may function as critical sentinels of virus invasion in insects.
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Wang XF, Zhang BQ, Xu HJ, Cui YJ, Xu YP, Zhang MJ, Han YS, Lee YS, Bao YY, Zhang CX. ODV-associated proteins of the Pieris rapae granulovirus. J Proteome Res 2011; 10:2817-27. [PMID: 21517121 DOI: 10.1021/pr2000804] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Alphabaculovirus (lepidopteran-specific nucleopolyhedroviruses, NPV) and Betabaculovirus (granuloviruses, GV) are two main genera of the family Baculoviridae. The virion proteomes of Alphabaculovirus have been well studied; however, the Betabaculovirus virion compositions remain unclear. Pieris rapae granulovirus (PrGV) can kill larvae of P. rapae, a worldwide and important pest of mustard family crops. In this study, the occlusion-derived virus (ODV)-associated proteins of PrGV were identified using three mass spectrometry (MS) approaches. The MS analyses demonstrated that 47 proteins were present in PrGV-ODV. Of the 47 PrGV-ODV proteins, 33 have homologues identified previously in other baculovirus ODV/BVs, whereas 14 (P10, Pr21, Pr29, Pr35, Pr42, Pr54, P45/48, Pr83, Pr84, Pr89, Pr92, Pr111, Pr114 and FGF3) were newly identified ODV proteins. Seven of the 14 newly identified ODV proteins are specific to Betabaculovirus, including Pr35, Pr42, Pr54, Pr83, Pr84, Pr111 and Pr114. Furthermore, the data derived from these MS approaches were validated by immunoblotting analysis using antisera prepared from 11 randomly selected recombinant PrGV-ODV proteins (including 5 Betabaculovirus-unique proteins). Comparison analyses revealed the similar and different compositions between Betabaculovirus and Alphabaculovirus virions, which deepen our understanding of the baculovirus virion structure and provide helpful information on Betabaculovirus--host interaction studies.
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Affiliation(s)
- Xiao-Feng Wang
- Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Ministry of Agriculture, Institute of Insect Science, Zhejiang-California International Nanosystem Institute, Zhejiang University, Hangzhou 310058, China
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31
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Heliothis zea nudivirus 1 gene hhi1 induces apoptosis which is blocked by the Hz-iap2 gene and a noncoding gene, pag1. J Virol 2011; 85:6856-66. [PMID: 21543471 DOI: 10.1128/jvi.01843-10] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Heliothis zea nudivirus 1 (HzNV-1 or Hz-1 virus), previously regarded as a nonoccluded baculovirus, recently has been placed in the Nudivirus genus. This virus generates HzNV-1 HindIII-I 1 (hhi1) and many other transcripts during productive viral infection; during latent viral infection, however, persistency-associated gene 1 (pag1) is the only gene expressed. In this report, we used transient expression assays to show that hhi1 can trigger strong apoptosis in transfected cells, which can be blocked, at least partially, by the inhibitor of apoptosis genes Autographa californica iap2 (Ac-iap2) and H. zea iap2 (Hz-iap2). In addition to these two genes, unexpectedly, pag1, which encodes a noncoding RNA with no detectable protein product, was found to efficiently suppress hhi1-induced apoptosis. The assay of pro-Sf-caspase-1 processing by hhi1 transfection did not detect the small P12 subunit at any of the time intervals tested, suggesting that hhi1 of HzNV-1 induces apoptosis through alternative caspase pathways.
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32
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Bakhrat A, Pritchett T, Peretz G, McCall K, Abdu U. Drosophila Chk2 and p53 proteins induce stage-specific cell death independently during oogenesis. Apoptosis 2011; 15:1425-34. [PMID: 20838898 DOI: 10.1007/s10495-010-0539-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
Abstract
In Drosophila, the checkpoint protein-2 kinase (DmChk2) and its downstream effector protein, Dmp53, are required for DNA damage-mediated cell cycle arrest, DNA repair and apoptosis. In this study we focus on understanding the function of these two apoptosis inducing factors during ovarian development. We found that expression of Dmp53, but not DmChk2, led to loss of ovarian stem cells. We demonstrate that expression of DmChk2, but not Dmp53, induced mid-oogenesis cell death. DmChk2 induced cell death was not suppressed by Dmp53 mutant, revealing for the first time that in Drosophila, over-expression of DmChk2 can induce cell death which is independent of Dmp53. We found that over-expression of caspase inhibitors such as DIAP1, p35 and p49 did not suppress DmChk2- and Dmp53-induced cell death. Thus, our study reveals stage-specific effects of Dmp53 and DmChk2 in oogenesis. Moreover, our results demonstrate that although DmChk2 and Dmp53 affect different stages of ovarian development, loss of ovarian stem cells by p53 expression and mid-oogenesis cell death induced by DmChk2 do not require caspase activity.
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Affiliation(s)
- Anna Bakhrat
- Department of Life Sciences, Ben-Gurion University, 84105 Beer-Sheva, Israel
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33
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Induction of reaper ortholog mx in mosquito midgut cells following baculovirus infection. Cell Death Differ 2011; 18:1337-45. [PMID: 21331076 DOI: 10.1038/cdd.2011.8] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Many vertebrate and insect viruses possess antiapoptotic genes that are required for their infectivity. This led to the hypothesis that apoptosis is an innate immunoresponse important for limiting virus infections. The role of apoptosis may be especially important in insect antiviral defense because of the lack of adaptive immunity. However, the cellular mechanism that elicits apoptosis in response to viral infection in insects has not been determined. Using an in vivo infection system with the mosquito baculovirus CuniNPV (Culex nigripalpus nucleopolyhedrovirus), we demonstrated that michelob_x (mx), the mosquito ortholog of Drosophila proapoptotic gene reaper, is specifically induced in larval midgut cells following viral infection. Interestingly, the dynamics of mx induction corresponds with the outcome of the infection. In the permissive mosquito C. quinquefasciatus, a slow induction of mx failed to induce prompt apoptosis, and the infected cells eventually undergo necrosis with heavy loads of encapsulated viruses. In contrast, in the refractory mosquito Aedes aegypti, a rapid induction of mx within 30 min p.i. is followed by apoptosis within 2-6 h p.i., suggesting a possible role for apoptosis in limiting viral infection. When the execution of apoptosis was delayed by caspase inhibitors, viral gene expression became detectable in the A. aegypti larvae.
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34
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Shahidi-Noghabi S, Van Damme EJM, Iga M, Smagghe G. Exposure of insect midgut cells to Sambucus nigra L. agglutinins I and II causes cell death via caspase-dependent apoptosis. JOURNAL OF INSECT PHYSIOLOGY 2010; 56:1101-1107. [PMID: 20230823 DOI: 10.1016/j.jinsphys.2010.03.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2010] [Revised: 03/03/2010] [Accepted: 03/04/2010] [Indexed: 05/28/2023]
Abstract
Sambucus nigra agglutinins I and II, further referred to as SNA-I and SNA-II, are two ricin-related lectins from elderberry. SNA-I is a chimeric lectin composed of an A-chain with enzymatic activity and a B-chain with carbohydrate-binding activity, and therefore belongs to the group of type 2 ribosome-inactivating proteins. In contrast, SNA-II consists only of carbohydrate-binding B-chains. The physiological effect of SNA-I was tested on different insect cell lines (midgut, ovary, fat body, embryo). In sensitive midgut CF-203 cells, SNA-I induced cell death with typical characteristics such as cell shrinkage, plasma membrane blebbing, nuclear condensation and DNA fragmentation. The effect was dose-dependent with 50% death of 4-day-exposed cells at 3nM. SNA-I exposure induced caspase-3 like activities, suggesting that SNA-I can induce the apoptotic pathway. Interestingly, the hololectin SNA-II also induced apoptosis in CF-203 cells at similar doses with the same physiological events. SNA-I and SNA-II both induced caspase-dependent apoptosis at low concentrations (nM order), leading to typical symptoms of cell death in sensitive cells. This effect seems independent from the catalytic activity of the A-chain, but depends on the carbohydrate-binding B-chain.
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Affiliation(s)
- Shahnaz Shahidi-Noghabi
- Laboratory of Agrozoology, Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, Ghent, Belgium
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35
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Host insect inhibitor-of-apoptosis SfIAP functionally replaces baculovirus IAP but is differentially regulated by Its N-terminal leader. J Virol 2010; 84:11448-60. [PMID: 20739517 DOI: 10.1128/jvi.01311-10] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The inhibitor-of-apoptosis (IAP) proteins encoded by baculoviruses bear a striking resemblance to the cellular IAP homologs of their invertebrate hosts. By virtue of the acquired selective advantage of blocking virus-induced apoptosis, baculoviruses may have captured cellular IAP genes that subsequently evolved for virus-specific objectives. To compare viral and host IAPs, we defined antiapoptotic properties of SfIAP, the principal cellular IAP of the lepidopteran host Spodoptera frugiperda. We report here that SfIAP prevented virus-induced apoptosis as well as viral Op-IAP3 (which is encoded by the Orgyia pseudotsugata nucleopolyhedrovirus) when overexpressed from the baculovirus genome. Like Op-IAP3, SfIAP blocked apoptosis at a step prior to caspase activation. Both of the baculovirus IAP repeats (BIRs) were required for SfIAP function. Moreover, deletion of the C-terminal RING motif generated a loss-of-function SfIAP that interacted and dominantly interfered with wild-type SfIAP. Like Op-IAP3, wild-type SfIAP formed intracellular homodimers, suggesting that oligomerization is a functional requirement for both cellular and viral IAPs. SfIAP possesses a ∼100-residue N-terminal leader domain, which is absent among all viral IAPs. Remarkably, deletion of the leader yielded a fully functional SfIAP with dramatically increased protein stability. Thus, the SfIAP leader contains an instability motif that may confer regulatory options for cellular IAPs that baculovirus IAPs have evolved to bypass for maximal stability and antiapoptotic potency. Our findings that SfIAP and viral IAPs have common motifs, share multiple biochemical properties including oligomerization, and act at the same step to block apoptosis support the hypothesis that baculoviral IAPs were derived by acquisition of host insect IAPs.
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36
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Functional analysis of Spodoptera litura nucleopolyhedrovirus p49 gene during Autographa californica nucleopolyhedrovirus infection of SpLi-221 cells. Virus Genes 2010; 41:441-9. [DOI: 10.1007/s11262-010-0520-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2010] [Accepted: 07/31/2010] [Indexed: 10/19/2022]
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37
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Identification and functional analysis of the putative anti-apoptotic gene iap4 of Spodoptera litura nucleopolyhedrovirus. Virus Genes 2010; 41:298-304. [DOI: 10.1007/s11262-010-0513-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Accepted: 07/01/2010] [Indexed: 11/28/2022]
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38
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Yan F, Xia D, lv S, Qi Y, Xu H. Functional analysis of the orf390 gene of the White Spot Syndrome Virus. Virus Res 2010; 151:39-44. [DOI: 10.1016/j.virusres.2010.03.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Revised: 03/23/2010] [Accepted: 03/24/2010] [Indexed: 10/19/2022]
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39
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Galluzzi L, Kepp O, Morselli E, Vitale I, Senovilla L, Pinti M, Zitvogel L, Kroemer G. Viral strategies for the evasion of immunogenic cell death. J Intern Med 2010; 267:526-42. [PMID: 20433579 DOI: 10.1111/j.1365-2796.2010.02223.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Viral strategies for the evasion of immunogenic cell death (Symposium). J Intern Med 2010; 267: 526-542. Driven by co-evolutionary forces, viruses have refined a wide arsenal of strategies to interfere with the host defences. On one hand, viruses can block/retard programmed cell death in infected cells, thereby suppressing one of the most ancient mechanisms against viral dissemination. On the other hand, multiple viral factors can efficiently trigger the death of infected cells and uninfected cells from the immune system, which favours viral spreading and prevents/limits an active antiviral response, respectively. Moreover, several viruses are able to inhibit the molecular machinery that drives the translocation of calreticulin to the surface of dying cells. Thereby, viruses block the exposure of an engulfment signal that is required for the efficient uptake of dying cells by dendritic cells and for the induction of the immune response. In this review, we discuss a variety of mechanisms by which viruses interfere with the cell death machinery and, in particular, by which they subvert immunogenic cell death.
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40
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41
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Functional analysis of the Autographa californica nucleopolyhedrovirus IAP1 and IAP2. ACTA ACUST UNITED AC 2009; 52:761-70. [PMID: 19727595 DOI: 10.1007/s11427-009-0105-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2008] [Accepted: 09/22/2008] [Indexed: 10/20/2022]
Abstract
The Autographa californica nucleopolyhedrovirus (AcMNPV) contains three apoptosis suppressor genes: p35, iap1 and iap2. AcMNPV P35 functions as a pancaspase inhibitor, but the function of IAP1 and IAP2 has not been entirely resolved. In this paper, we analyze the function of IAP1 and IAP2 in detail. AcMNPV with p35-deletion inhibited the apoptosis of BTI-Tn-5B1-4 (Tn-Hi5) cells induced by a Helicoverpa armigera single nucleocapsid NPV (HearNPV) infection and rescued the replication of HearNPV and BV production in these cells. Transient-expression experiments indicated that both IAP1 and IAP2 suppress apoptosis of Tn-Hi5 cells during HearNPV infection. Recombinant HearNPVs expressing AcMNPV iap1, iap2 and p35, respectively, not only prevented apoptosis but also allowed HearNPV to replicate in Tn-Hi5 cells. However, the iap1, iap2 and p35 genes when expressed in HearNPV were unable to rescue BV production. These results indicate that both AcMNPV iap1 and iap2 function independently as apoptosis inhibitors of and are potential host range factors.
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42
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Baculovirus DNA replication-specific expression factors trigger apoptosis and shutoff of host protein synthesis during infection. J Virol 2009; 83:11123-32. [PMID: 19706708 DOI: 10.1128/jvi.01199-09] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Apoptosis is an important antivirus defense. To define the poorly understood pathways by which invertebrates respond to viruses by inducing apoptosis, we have identified replication events that trigger apoptosis in baculovirus-infected cells. We used RNA silencing to ablate factors required for multiplication of Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV). Transfection with double-stranded RNA (dsRNA) complementary to the AcMNPV late expression factors (lefs) that are designated as replicative lefs (lef-1, lef-2, lef-3, lef-11, p143, dnapol, and ie-1/ie-0) blocked virus DNA synthesis and late gene expression in permissive Spodoptera frugiperda cells. dsRNAs specific to designated nonreplicative lefs (lef-8, lef-9, p47, and pp31) blocked late gene expression without affecting virus DNA replication. Thus, both classes of lefs functioned during infection as defined. Silencing the replicative lefs prevented AcMNPV-induced apoptosis of Spodoptera cells, whereas silencing the nonreplicative lefs did not. Thus, the activity of replicative lefs or virus DNA replication is sufficient to trigger apoptosis. Confirming this conclusion, AcMNPV-induced apoptosis was suppressed by silencing the replicative lefs in cells from a divergent species, Drosophila melanogaster. Silencing replicative but not nonreplicative lefs also abrogated AcMNPV-induced shutdown of host protein synthesis, suggesting that virus DNA replication triggers inhibition of host biosynthetic processes and that apoptosis and translational arrest are linked. Our findings suggest that baculovirus DNA replication triggers a host cell response similar to the DNA damage response in vertebrates, which causes translational arrest and apoptosis. Pathways for detecting virus invasion and triggering apoptosis may therefore be conserved between insects and mammals.
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43
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Thiem SM. Baculovirus genes affecting host function. In Vitro Cell Dev Biol Anim 2009; 45:111-26. [PMID: 19247726 DOI: 10.1007/s11626-008-9170-5] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2008] [Accepted: 12/20/2008] [Indexed: 12/24/2022]
Abstract
Baculoviruses are insect-specific viruses. These large DNA viruses encode many genes in addition to those required to replicate and build new virions. These auxiliary genes provide selective advantages to the virus for invading and infecting host insects. Eight of these genes, which help the virus overcome insect defenses against invasion, are discussed. These include genes whose products help the virus traverse physical or physiological barriers and those that overcome host immune defenses.
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Affiliation(s)
- Suzanne M Thiem
- Department of Entomology, Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48825, USA.
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44
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45
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Hebert CG, Valdes JJ, Bentley WE. Investigating apoptosis: characterization and analysis of Trichoplusia ni-caspase-1 through overexpression and RNAi mediated silencing. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2009; 39:113-124. [PMID: 19027856 DOI: 10.1016/j.ibmb.2008.10.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2008] [Revised: 10/15/2008] [Accepted: 10/21/2008] [Indexed: 05/27/2023]
Abstract
In both mammals and invertebrates, caspases play a critical role in apoptosis. Although Lepidopteron caspases have been widely studied in Spodoptera frugiperda cells, this is not the case for Trichoplusia ni cells, despite their widespread use for the production of recombinant protein and differences in baculovirus infectivity between the two species. We have cloned, expressed, purified and characterized Tn-caspase-1 in several situations: in its overexpression, in silencing via RNA interference (RNAi), during baculovirus infection, and in interactions with baculovirus protein p35. Overexpression can transiently increase caspase activity in T. ni (High Five) cells, while silencing results in a greater than 6-fold decrease. The reduction in caspase activity resulted in a reduction in the level of apoptosis, demonstrating the ability to affect apoptosis by modulating Tn-caspase-1. During baculovirus infection, caspase activity remains low until approximately 5 days post infection, at which point it increases dramatically, though not in those cells treated with dsRNA. Our results demonstrate that Tn-caspase-1 is presumably the principal effector caspase present in High Five cells, and that it is inhibited by baculovirus protein p35. Finally, our results indicate differences between RNAi and p35 as effector molecules for modulating caspase activity and apoptosis during cell growth and baculovirus infection.
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Affiliation(s)
- Colin G Hebert
- Center for Biosystems Research, University of Maryland Biotechnology Institute, 5115 Plant Science Building, College Park, MD 20742, USA
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46
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Sahdev S, Saini KS, Hasnain SE. Baculovirus P35 protein: An overview of its applications across multiple therapeutic and biotechnological arenas. Biotechnol Prog 2009; 26:301-12. [DOI: 10.1002/btpr.339] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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47
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Abstract
To prolong cell viability and facilitate replication, viruses have evolved multiple mechanisms to inhibit the host apoptotic response. Cellular proteases such as caspases and serine proteases are instrumental in promoting apoptosis. Thus, these enzymes are logical targets for virus-mediated modulation to suppress cell death. Four major classes of viral inhibitors antagonize caspase function: serpins, p35 family members, inhibitor of apoptosis proteins, and viral FLICE-inhibitory proteins. Viruses also subvert activity of the serine proteases, granzyme B and HtrA2/Omi, to avoid cell death. The combined efforts of viruses to suppress apoptosis suggest that this response should be avoided at all costs. However, some viruses utilize caspases during replication to aid virus protein maturation, progeny release, or both. Hence, a multifaceted relationship exists between viruses and the apoptotic response they induce. Examination of these interactions contributes to our understanding of both virus pathogenesis and the regulation of apoptotic enzymes in normal cellular functions.
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Affiliation(s)
- Sonja M Best
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 59840, USA.
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48
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Transactivator IE1 is required for baculovirus early replication events that trigger apoptosis in permissive and nonpermissive cells. J Virol 2008; 83:262-72. [PMID: 18945761 DOI: 10.1128/jvi.01827-08] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Immediate early viral protein IE1 is a potent transcriptional activator encoded by baculoviruses. Although the requirement of IE1 for multiplication of Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) is well established, the functional roles of IE1 during infection are unclear. Here, we used RNA interference to ablate IE1, plus its splice variant IE0, and thereby define in vivo activities of these early proteins, including gene-specific regulation and induction of host cell apoptosis. Confirming an essential replicative role, simultaneous ablation of IE1 and IE0 by gene-specific double-stranded RNAs inhibited AcMNPV late gene expression, reduced yields of budded virus by more than 1,000-fold, and blocked production of occluded virus particles. Depletion of IE1 and IE0 had no effect on early expression of the envelope fusion protein gene gp64 but abolished early expression of the caspase inhibitor gene p35, which is required for prevention of virus-induced apoptosis. Thus, IE1 is a positive, gene-specific transactivator. Whereas an AcMNPV p35 deletion mutant caused widespread apoptosis in permissive Spodoptera frugiperda cells, ablation of IE1 and IE0 prevented this apoptosis. Silencing of ie-1 also prevented AcMNPV-induced apoptosis in nonpermissive Drosophila melanogaster cells. Thus, de novo synthesis of IE1 is required for virus-induced apoptosis. We concluded that IE1 causes apoptosis directly or contributes indirectly by promoting virus replication events that subsequently trigger cell death. This study reveals that IE1 is a gene-selective transcriptional activator which is required not only for expedition of virus multiplication but also for blocking of its own proapoptotic activity by upregulation of baculovirus apoptotic suppressors.
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49
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Yu Q, Lin T, Feng G, Yang K, Pang Y. Functional analysis of the putative antiapoptotic genes, p49 and iap4, of Spodoptera litura nucleopolyhedrovirus with RNAi. J Gen Virol 2008; 89:1873-1880. [DOI: 10.1099/vir.0.2008/001008-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A homology search of a public database revealed that Spodoptera litura nucleopolyhedrovirus (SpltNPV) possesses two putative, antiapoptotic genes, p49 and inhibitor of apoptosis 4 (iap4), but their function has not been investigated in its native host cells. In the present study, we used RNA interference (RNAi) to silence the expression of Splt-iap4 and Splt-p49, independently or together, to determine their roles during the SpltNPV life cycle. RT-PCR analysis and Western blot analysis showed the target gene expression had been knocked out in the SpltNPV-infected SpLi-221 cells after treatment with Splt-p49 or Splt-iap4 double-stranded RNA (dsRNA), respectively, confirming that the two genes were effectively silenced. In SpltNPV-infected cells treated with Splt-p49 dsRNA, apoptosis was observed beginning at 14 h, and almost all cells had undergone apoptosis by 48 h. In contrast, budded virus production and polyhedra formation progressed normally in infected cells treated with Splt-iap4 dsRNA. Cell viability analysis showed that Splt-IAP4 had no synergistic effect on the inhibition of apoptosis of SpLi-221 cells induced by SpltNPV infection. Interestingly, after Splt-iap4 dsRNA treatment, cells did not congregate like those infected with SpltNPV in the early infection phase, implying an unknown role of baculovirus iap4. Our results determine that Splt-p49 is necessary to prevent apoptosis; however, Splt-iap4 has no antiapoptotic function during SpltNPV infection.
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Affiliation(s)
- Qian Yu
- State Key Laboratory of Biocontrol, Sun Yat-sen University, Guangzhou 510275, PR China
| | - Tiehao Lin
- State Key Laboratory of Biocontrol, Sun Yat-sen University, Guangzhou 510275, PR China
| | - Guozhong Feng
- State Key Laboratory of Biocontrol, Sun Yat-sen University, Guangzhou 510275, PR China
| | - Kai Yang
- State Key Laboratory of Biocontrol, Sun Yat-sen University, Guangzhou 510275, PR China
| | - Yi Pang
- State Key Laboratory of Biocontrol, Sun Yat-sen University, Guangzhou 510275, PR China
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50
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Tseng YK, Wu MS, Hou RF. Induction of apoptosis in SF21 cell line by conditioned medium of the entomopathogenic fungus, Nomuraea rileyi, through Sf-caspase-1 signaling pathway. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2008; 68:206-214. [PMID: 18395831 DOI: 10.1002/arch.20242] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The apoptosis in SF-21 cell line can be induced by the conditioned medium (CM) of the entomopathogenic fungus, Nomuraea rileyi, based on changes in morphology and formation of apoptotic bodies in cultured cells, and with the onset of DNA fragmentation as shown by TUNEL staining and agarose electrophoresis. Moreover, the induction of apoptosis in SF-21 cells was inhibited by adding the inhibitor of effector caspase, viz. z-DEVD-fmk, to the CM, indicating that Sf-caspase-1 is involved in this apoptosis. Similarly, the inhibitor of initiator caspase, viz., z-VAD-fmk, inhibited apoptosis. Therefore, both initiator and effector caspases are possibly involved in the apoptosis of SF-21 cells. In addition, we detected Sf-caspase-1 activity in the process of apoptosis in SF-21 cells, suggesting that the effector caspase in SF-21 is similar to that found in mammalian cells. Our results also indicated that the apoptosis found in this line is accomplished through a Sf-caspase-1 signaling pathway.
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Affiliation(s)
- Yu-Kai Tseng
- Department of Entomology, National Chung Hsing University, Taichung, Taiwan 402, Republic of China
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