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Yu Q, Wang M, Ding X, Han J, Ma H, Li J, Zheng G, Zhang B, Li C. The Expression of P35 Plays a Key Role in the Difference in Apoptosis Induced by AcMNPV Infection in Different Spodoptera exigua Cell Lines. Int J Mol Sci 2023; 24:13228. [PMID: 37686033 PMCID: PMC10487845 DOI: 10.3390/ijms241713228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Revised: 08/12/2023] [Accepted: 08/23/2023] [Indexed: 09/10/2023] Open
Abstract
Baculovirus infection induces apoptosis in host cells, and apoptosis significantly affects virus production. Autographa californica multiple nucleopolyhedrovirus (AcMNPV) can regulate apoptosis, but the regulatory mechanism is unclear. Here, we found that AcMNPV infection induced different apoptosis responses in different Spodoptera exigua cell lines. In the early stages of viral infection (1-6 h), Se-1 cells underwent severe apoptosis, while Se-3 cells underwent very slight apoptosis. In the late stages of viral infection (12-72 h), Se-1 cells continued to undergo apoptosis and formed a large number of apoptotic bodies, while the apoptosis of Se-3 cells was inhibited and no apoptotic bodies were formed. To determine the reasons for the apoptosis differences in the two cell lines, we measured the expression of the six S. exigua cysteine-dependent aspartate specific protease genes (SeCaspase-1 to -6) and the three AcMNPV antiapoptotic protein genes (iap1, iap2 and p35) during viral infection. We found that SeCaspase-1 to -6 were all activated in Se-1 cells and inhibited in Se-3 cells, whereas iap1, iap2 and p35 were all inhibited in Se-1 cells and normally expressed in Se-3 cells. And p35 was expressed earlier than iap1 and iap2 in Se-3 cells. Otherwise, Se-1 and Se-3 cells would all be apoptotic when infected with the recombinant p35 knockout AcMNPV, whereas only Se-1 cells were apoptotic, but Se-3 cells were not apoptotic when infected with the recombinant p35 repair AcMNPV. Combined with the fact that the expression of P35 protein is inhibited in Se-1 cells but normally expressed in Se-3 cells during the infection of recombinant p35 repair AcMNPV, we proposed that the different expression of P35 is an important reason for the apoptosis differences between the two cell lines. We also found that some genes associated with apoptosis can probably regulate the expression of P35. However, the major upstream regulators of P35 and their mechanisms are still unclear and will be studied in the future.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Changyou Li
- Shangdong Engineering Research Center for Environment-Friendly Agricultural Pest Management, Qingdao Agricultural University, Qingdao 266109, China; (Q.Y.); (M.W.); (X.D.); (J.H.); (H.M.); (J.L.); (G.Z.); (B.Z.)
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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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An increase in mitochondrial TOM activates apoptosis to drive retinal neurodegeneration. Sci Rep 2022; 12:21634. [PMID: 36517509 PMCID: PMC9750964 DOI: 10.1038/s41598-022-23280-z] [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] [Received: 04/04/2022] [Accepted: 10/25/2022] [Indexed: 12/23/2022] Open
Abstract
Intronic polymorphic TOMM40 variants increasing TOMM40 mRNA expression are strongly correlated to late onset Alzheimer's Disease. The gene product, hTomm40, encoded in the APOE gene cluster, is a core component of TOM, the translocase that imports nascent proteins across the mitochondrial outer membrane. We used Drosophila melanogaster eyes as an in vivo model to investigate the relationship between elevated Tom40 (the Drosophila homologue of hTomm40) expression and neurodegeneration. Here we provide evidence that an overabundance of Tom40 in mitochondria invokes caspase-dependent cell death in a dose-dependent manner, leading to degeneration of the primarily neuronal eye tissue. Degeneration is contingent on the availability of co-assembling TOM components, indicating that an increase in assembled TOM is the factor that triggers apoptosis and degeneration in a neural setting. Eye death is not contingent on inner membrane translocase components, suggesting it is unlikely to be a direct consequence of impaired import. Another effect of heightened Tom40 expression is upregulation and co-association of a mitochondrial oxidative stress biomarker, DmHsp22, implicated in extension of lifespan, providing new insight into the balance between cell survival and death. Activation of regulated death pathways, culminating in eye degeneration, suggests a possible causal route from TOMM40 polymorphisms to neurodegenerative disease.
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Li Y, Cai J, Du C, Lin Y, Li S, Ma A, Qin Y. Bioinformatic analysis and antiviral effect of Periplaneta americana defensins. Virus Res 2021; 308:198627. [PMID: 34785275 DOI: 10.1016/j.virusres.2021.198627] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 11/01/2021] [Accepted: 11/06/2021] [Indexed: 01/08/2023]
Abstract
Due to the lack of an adaptive immune system, insects rely on innate immune mechanisms to fight against pathogenic infections. Two major innate immune pathways, Toll and IMD, orchestrate anti-pathogen responses by regulating the expression of antimicrobial peptide (AMP) genes. Although the antifungal or antibacterial function of AMPs has been well characterized, the antiviral role of AMPs in insects remains largely unclear. Periplaneta americana (P. americana), or the American cockroach, is used in traditional Chinese medicine as an antiviral agent; however, the underlying mechanism of action of P. americana extracts is unclear. Our previous study showed that the P. americana genome encodes multiple antimicrobial peptide genes. Based on these data, we predicted five novel P. americana defensins (PaDefensins) and analyzed their primary structure, secondary structure, and physicochemical properties. The putative antiviral, antifungal, antibacterial, and anticancer activities suggested that PaDefensin5 is a desirable therapeutic candidate against viral diseases. As the first experimental evidence of the antiviral effects of insect defensins, we also showed the antiviral effect of PaDefensin5 in Drosophila Kc cells and Drosophila embryos in vivo . In conclusion, results of both in silico predictions and subsequent antiviral experiments suggested PaDefensin5 a promising antiviral drug.
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Affiliation(s)
- Ying Li
- Guangdong Provincial Key Laboratory of Insect Developmental Biology and Applied Technology, Institute of Insect Science and Technology & School of Life Sciences, South China Normal University, Guangzhou, China; Guangmeiyuan R&D Center, Guangdong Provincial Key Laboratory of Insect Developmental Biology and Applied Technology, South China Normal University, Meizhou, China
| | - Jie Cai
- Guangdong Provincial Key Laboratory of Insect Developmental Biology and Applied Technology, Institute of Insect Science and Technology & School of Life Sciences, South China Normal University, Guangzhou, China; Guangmeiyuan R&D Center, Guangdong Provincial Key Laboratory of Insect Developmental Biology and Applied Technology, South China Normal University, Meizhou, China
| | - Chunyu Du
- Guangdong Provincial Key Laboratory of Insect Developmental Biology and Applied Technology, Institute of Insect Science and Technology & School of Life Sciences, South China Normal University, Guangzhou, China; Guangmeiyuan R&D Center, Guangdong Provincial Key Laboratory of Insect Developmental Biology and Applied Technology, South China Normal University, Meizhou, China
| | - Yuhua Lin
- Guangdong Provincial Key Laboratory of Insect Developmental Biology and Applied Technology, Institute of Insect Science and Technology & School of Life Sciences, South China Normal University, Guangzhou, China
| | - Sheng Li
- Guangdong Provincial Key Laboratory of Insect Developmental Biology and Applied Technology, Institute of Insect Science and Technology & School of Life Sciences, South China Normal University, Guangzhou, China; Guangmeiyuan R&D Center, Guangdong Provincial Key Laboratory of Insect Developmental Biology and Applied Technology, South China Normal University, Meizhou, China
| | - Anping Ma
- Insititution of chemical surveillance, Guangdong Province Hospital for Occupational Disease Prevention and Treatment, Guangzhou, Guangdong, China
| | - Yiru Qin
- Guangdong Provincial Key Laboratory of Insect Developmental Biology and Applied Technology, Institute of Insect Science and Technology & School of Life Sciences, South China Normal University, Guangzhou, China; Insititution of chemical surveillance, Guangdong Province Hospital for Occupational Disease Prevention and Treatment, Guangzhou, Guangdong, China.
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Wang X, Zhao ZQ, Huang XM, Ding XY, Zhao CX, Li MW, Wu YC, Liu QN, Wang XY. Bmcas-1 plays an important role in response against BmNPV infection in vitro. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2021; 107:e21793. [PMID: 33949719 DOI: 10.1002/arch.21793] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 03/19/2021] [Accepted: 04/05/2021] [Indexed: 06/12/2023]
Abstract
Apoptosis, as one kind of innate immune system, is involved in host response against pathogens innovation. Caspases play a vital role in the execution stage of host cell apoptosis. It has been reported that Bmcaspase-1 (Bmcas-1) has a close relationship with Bombyx mori nucleopolyhedrovirus (BmNPV) infection for its differentially expressed patterns after viral infection. However, its underlying response mechanism is still unclear. The significant differential expression of Bmcas-1 in different tissues of differentially resistant strains revealed its vital role in BmNPV infection. To further validate its role in BmNPV infection, budded virus (BV)-eGFP was analyzed after knockdown and overexpression of Bmcas-1 by small interfering RNA and the pIZT-mCherry vector, respectively. The reproduction of BV-eGFP obviously increased at 72 h after knockdown of Bmcas-1, and decreased after overexpression in BmN cells. Moreover, the conserved functional domain of Cas-1 among different species and the closed evolutionary relationship of Cas-1 in Lepidoptera hinted that Bmcas-1 might be associated with apoptosis, and this was also validated by the apoptosis inducer, Silvestrol, and the inhibitor, Z-DEVD-FMK. Therefore, Bmcas-1 plays an essential antiviral role by activating apoptosis, and this result lays a fundament for clarifying the molecular mechanism of silkworm in response against BmNPV infection and breeding of resistant strains.
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Affiliation(s)
- Xin Wang
- Jiangsu Key Laboratory of Sericultural Biology and Biotechnology, School of Biotechnology, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu, China
| | - Zi-Qin Zhao
- Jiangsu Key Laboratory of Sericultural Biology and Biotechnology, School of Biotechnology, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu, China
| | - Xin-Ming Huang
- Jiangsu Key Laboratory of Sericultural Biology and Biotechnology, School of Biotechnology, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu, China
| | - Xin-Yi Ding
- Jiangsu Key Laboratory of Sericultural Biology and Biotechnology, School of Biotechnology, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu, China
| | - Chun-Xiao Zhao
- Jiangsu Key Laboratory of Sericultural Biology and Biotechnology, School of Biotechnology, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu, China
| | - Mu-Wang Li
- Jiangsu Key Laboratory of Sericultural Biology and Biotechnology, School of Biotechnology, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu, China
- Key Laboratory of Silkworm and Mulberry Genetic Improvement, Ministry of Agriculture and Rural Affairs, Sericultural Research Institute, Chinese Academy of Agricultural Science, Zhenjiang, Jiangsu, China
| | - Yang-Chun Wu
- Jiangsu Key Laboratory of Sericultural Biology and Biotechnology, School of Biotechnology, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu, China
- Key Laboratory of Silkworm and Mulberry Genetic Improvement, Ministry of Agriculture and Rural Affairs, Sericultural Research Institute, Chinese Academy of Agricultural Science, Zhenjiang, Jiangsu, China
| | - Qiu-Ning Liu
- Jiangsu Key Laboratory for Bioresources of Saline Soils, Jiangsu Synthetic Innovation Center for Coastal Bio-agriculture, Jiangsu Provincial Key Laboratory of Coastal Wetland Bioresources and Environmental Protection, School of Wetland, Yancheng, Jiangsu, China
| | - Xue-Yang Wang
- Jiangsu Key Laboratory of Sericultural Biology and Biotechnology, School of Biotechnology, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu, China
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Zhang X, Zhao K, Lan L, Shi N, Nan H, Shi Y, Xu X, Chen H. Improvement of protein production by engineering a novel antiapoptotic baculovirus vector to suppress the expression of Sf-caspase-1 and Tn-caspase-1. Biotechnol Bioeng 2021; 118:2977-2989. [PMID: 33990946 DOI: 10.1002/bit.27807] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 04/13/2021] [Accepted: 04/25/2021] [Indexed: 11/11/2022]
Abstract
The baculovirus expression vector system (BEVS) is an attractive manufacturing platform for recombinant protein production in insect cells. However, baculovirus infection commonly induces host apoptosis in 3-4 days which would subsequently terminate the protein expression. Previous studies have proved that protein production by BEVS can be elevated in apoptosis-suppressed insect cells. We also developed a baculovirus vector in our previous report to inhibit the apoptosis and improve protein production in Sf9 cells. In this study, we designed five short hairpin RNA (shRNA) expression cassettes targeting a conserved region in Spodoptera frugiperda caspase-1 (Sf-caspase-1) and Trichoplusia ni caspase-1 (Tn-caspase-1), and found that introduction of C to T mutations within the stem region of the expression cassette was beneficial for the heterologous protein expression. One of the improved shRNA expression cassettes was knocked into a bacmid with the deletion of several nonessential genes. The novel baculovirus vector demonstrated the ability to suppress cell apoptosis in both Sf9 and High Five cells, and exhibited superior recombinant protein productivity of intracellularly expressed GFP and firefly luciferase and secreted glycoprotein OD-Fc. The antiapoptotic baculovirus vector developed in this study could serve as a useful tool for the protein production in scientific research and pharmaceutical industries.
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Affiliation(s)
- Xiaoyue Zhang
- College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China.,R&D Department, Shaanxi Bacmid Biotechnology Co., Ltd, Yangling, Shaanxi, China
| | - Kaixia Zhao
- College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China
| | - Lan Lan
- College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China
| | - Na Shi
- College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China
| | - Hao Nan
- College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China
| | - Yanan Shi
- College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China
| | - Xiaodong Xu
- College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China
| | - Hongying Chen
- College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China
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Tang XT, Fortuna K, Mendoza Herrera A, Tamborindeguy C. Liberibacter, A Preemptive Bacterium: Apoptotic Response Repression in the Host Gut at the Early Infection to Facilitate Its Acquisition and Transmission. Front Microbiol 2020; 11:589509. [PMID: 33424791 PMCID: PMC7786102 DOI: 10.3389/fmicb.2020.589509] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 12/04/2020] [Indexed: 12/20/2022] Open
Abstract
“Candidatus Liberibacter solanacearum” (Lso) is a phloem-limited Gram-negative bacterium that infects crops worldwide. In North America, two haplotypes of Lso (LsoA and LsoB) are transmitted by the potato psyllid, Bactericera cockerelli (Šulc), in a circulative and persistent manner. Both haplotypes cause damaging plant diseases (e.g., zebra chip in potatoes). The psyllid gut is the first organ Lso encounters and could be a barrier for its transmission. However, little is known about the psyllid gut immune responses triggered upon Lso infection. In this study, we focused on the apoptotic response in the gut of adult potato psyllids at the early stage of Lso infection. We found that there was no evidence of apoptosis induced in the gut of the adult potato psyllids upon infection with either Lso haplotype based on microscopic observations. However, the expression of the inhibitor of apoptosis IAPP5.2 gene (survivin-like) was significantly upregulated during the period that Lso translocated into the gut cells. Interestingly, silencing of IAPP5.2 gene significantly upregulated the expression of two effector caspases and induced apoptosis in the psyllid gut cells. Moreover, RNA interference (RNAi) of IAPP5.2 significantly decreased the Lso titer in the gut of adult psyllids and reduced their transmission efficiency. Taken together, these observations suggest that Lso might repress the apoptotic response in the psyllid guts by inducing the anti-apoptotic gene IAPP5.2 at an early stage of the infection, which may favor Lso acquisition in the gut cells and facilitate its transmission by potato psyllid.
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Affiliation(s)
- Xiao-Tian Tang
- Department of Entomology, Texas A&M University, College Station, TX, United States
| | - Kelsy Fortuna
- Department of Entomology, Texas A&M University, College Station, TX, United States
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Yeh PA, Liu YH, Chu WC, Liu JY, Sun YH. Glial expression of disease-associated poly-glutamine proteins impairs the blood-brain barrier in Drosophila. Hum Mol Genet 2019; 27:2546-2562. [PMID: 29726932 DOI: 10.1093/hmg/ddy160] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 04/25/2018] [Indexed: 12/25/2022] Open
Abstract
Expansion of poly-glutamine (polyQ) stretches in several proteins has been linked to neurodegenerative diseases. The effects of polyQ-expanded proteins on neurons have been extensively studied, but their effects on glia remain unclear. We found that expression of distinct polyQ proteins exclusively in all glia or specifically in the blood-brain barrier (BBB) and blood-retina barrier (BRB) glia caused cell-autonomous impairment of BBB/BRB integrity, suggesting that BBB/BRB glia are most vulnerable to polyQ-expanded proteins. Furthermore, we also found that BBB/BRB leakage in Drosophila is reflected in reversed waveform polarity on the basis of electroretinography (ERG), making ERG a sensitive method to detect BBB/BRB leakage. The polyQ-expanded protein Atxn3-84Q forms aggregates, induces BBB/BRB leakage, restricts Drosophila lifespan and reduces the level of Repo (a pan-glial transcriptional factor required for glial differentiation). Expression of Repo in BBB/BRB glia can rescue BBB/BRB leakage, suggesting that the reduced expression of Repo is important for the effect of polyQ on BBB/BRB impairment. Coexpression of the chaperon HSP40 and HSP70 effectively rescues the effects of Atxn3-84Q, indicating that polyQ protein aggregation in glia is deleterious. Intriguingly, coexpression of wild-type Atxn3-27Q can also rescue BBB/BRB impairment, suggesting that normal polyQ protein may have a protective function.
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Affiliation(s)
- Po-An Yeh
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.,Department of Bioscience Technology, Chung Yuan Christian University, Chung Li, Taiwan
| | - Ya-Hsin Liu
- Department of Life Sciences, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan
| | - Wei-Chen Chu
- Laboratory for Morphogenetic Signaling, RIKEN Center for Biosystems Dynamics Research (BDR), Chuou-ku, Kobe, Japan
| | - Jia-Yu Liu
- Graduate Institute of Clinical Medicine, Taipei Medical University, Taipei, Taiwan
| | - Y Henry Sun
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
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McLaughlin CN, Perry-Richardson JJ, Coutinho-Budd JC, Broihier HT. Dying Neurons Utilize Innate Immune Signaling to Prime Glia for Phagocytosis during Development. Dev Cell 2019; 48:506-522.e6. [PMID: 30745142 DOI: 10.1016/j.devcel.2018.12.019] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 11/19/2018] [Accepted: 12/21/2018] [Indexed: 02/06/2023]
Abstract
Glia continuously survey neuronal health during development, providing trophic support to healthy neurons while rapidly engulfing dying ones. These diametrically opposed functions necessitate a foolproof mechanism enabling glia to unambiguously identify those neurons to support versus those to engulf. To ensure specificity, glia are proposed to interact with dying neurons via a series of carefully choreographed steps. However, these crucial interactions are largely obscure. Here we show that dying neurons and glia communicate via Toll-receptor-regulated innate immune signaling. Neuronal apoptosis drives processing and activation of the Toll-6 ligand, Spätzle5. This cue activates a dSARM-mediated Toll-6 transcriptional pathway in glia, which controls the expression of the Draper engulfment receptor. Pathway loss drives early-onset neurodegeneration, underscoring its functional importance. Our results identify an upstream priming signal that prepares glia for phagocytosis. Thus, a core innate immune pathway plays an unprecedented role setting the valence of neuron-glia interactions during development.
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Affiliation(s)
- Colleen N McLaughlin
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA.
| | - Jahci J Perry-Richardson
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | | | - Heather T Broihier
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA.
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Khan C, Muliyil S, Rao BJ. Genome Damage Sensing Leads to Tissue Homeostasis in Drosophila. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2019; 345:173-224. [PMID: 30904193 DOI: 10.1016/bs.ircmb.2018.12.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
DNA repair is a critical cellular process required for the maintenance of genomic integrity. It is now well appreciated that cells employ several DNA repair pathways to take care of distinct types of DNA damage. It is also well known that a cascade of signals namely DNA damage response or DDR is activated in response to DNA damage which comprise cellular responses, such as cell cycle arrest, DNA repair and cell death, if the damage is irreparable. There is also emerging literature suggesting a cross-talk between DNA damage signaling and several signaling networks within a cell. Moreover, cell death players themselves are also well known to engage in processes outside their canonical function of apoptosis. This chapter attempts to build a link between DNA damage, DDR and signaling from the studies mainly conducted in mammals and Drosophila model systems, with a special emphasis on their relevance in overall tissue homeostasis and development.
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Affiliation(s)
- Chaitali Khan
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India
| | - Sonia Muliyil
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India
| | - B J Rao
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India.
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Baena-Lopez LA, Arthurton L, Bischoff M, Vincent JP, Alexandre C, McGregor R. Novel initiator caspase reporters uncover previously unknown features of caspase-activating cells. Development 2018; 145:dev170811. [PMID: 30413561 PMCID: PMC6288387 DOI: 10.1242/dev.170811] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Accepted: 10/31/2018] [Indexed: 12/30/2022]
Abstract
The caspase-mediated regulation of many cellular processes, including apoptosis, justifies the substantial interest in understanding all of the biological features of these enzymes. To complement functional assays, it is crucial to identify caspase-activating cells in live tissues. Our work describes novel initiator caspase reporters that, for the first time, provide direct information concerning the initial steps of the caspase activation cascade in Drosophila tissues. One of our caspase sensors capitalises on the rapid subcellular localisation change of a fluorescent marker to uncover novel cellular apoptotic events relating to the actin-mediated positioning of the nucleus before cell delamination. The other construct benefits from caspase-induced nuclear translocation of a QF transcription factor. This feature enables the genetic manipulation of caspase-activating cells and reveals the spatiotemporal patterns of initiator caspase activity. Collectively, our sensors offer experimental opportunities not available by using previous reporters and have proven useful to illuminate previously unknown aspects of caspase-dependent processes in apoptotic and non-apoptotic cellular scenarios.
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Affiliation(s)
- Luis Alberto Baena-Lopez
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxfordshire, OX1 3RE, UK
| | - Lewis Arthurton
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxfordshire, OX1 3RE, UK
| | - Marcus Bischoff
- Biomolecular Sciences Research Complex, University of St Andrews, North Haugh, St Andrews, Fife, Scotland, KY16 9ST, UK
| | | | | | - Reuben McGregor
- Faculty of Medical and Health Sciences, Molecular Medicine & Pathology, The University of Auckland, M&HS Building 502, 85 Park Road, Grafton, Auckland 1023, New Zealand
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Development of a baculovirus vector carrying a small hairpin RNA for suppression of sf-caspase-1 expression and improvement of recombinant protein production. BMC Biotechnol 2018; 18:24. [PMID: 29720159 PMCID: PMC5930690 DOI: 10.1186/s12896-018-0434-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 04/11/2018] [Indexed: 12/31/2022] Open
Abstract
Background The Baculovirus expression vector system (BEVS) is a transient expression platform for recombinant protein production in insect cells. Baculovirus infection of insect cells will shutoff host translation and induce apoptosis and lead to the termination of protein expression. Previous reports have demonstrated the enhancement of protein yield in BEVS using stable insect cell lines expressing interference RNA to suppress the expression of caspase-1. Results In this study, short-hairpin RNA (shRNA) expression cassettes targeting Spodoptera frugiperda caspase-1 (Sf-caspase-1) were constructed and inserted into an Autographa californica multiple nucleopolyhedrovirus (AcMNPV) vector. Using the recombinant baculovirus vectors, we detected the suppression of Sf-caspase-1 expression and cell apoptosis. Green fluorescent protein (GFP), Discosoma sp. Red (DsRed) and firefly luciferase were then expressed as reporter proteins. The results showed that suppression of apoptosis enhanced the accumulation of exogenous proteins at 2 and 3 days post infection. After 4 days post infection, the activity of the reporter proteins remained higher in BEVS using the baculovirus carrying shRNA in comparison with the control without shRNA, but the accumulated protein levels showed no obvious difference between them, suggesting that apoptosis suppression resulted in improved protein folding rather than translation efficiency at the very late stage of baculovirus infection. Conclusions The baculovirus vector developed in this study would be a useful tool for the production of active proteins suitable for structural and functional studies or pharmaceutical applications in Sf9 cells, and it also has the potential to be adapted for the improvement of protein expression in different insect cell lines that can be infected by AcMNPV.
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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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14
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Ibar C, Glavic Á. Drosophila p115 is required for Cdk1 activation and G2/M cell cycle transition. Mech Dev 2017; 144:191-200. [PMID: 28396045 DOI: 10.1016/j.mod.2017.04.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 03/28/2017] [Accepted: 04/07/2017] [Indexed: 11/25/2022]
Abstract
Golgi complex inheritance and its relationship with the cell cycle are central in cell biology. Golgi matrix proteins, known as golgins, are one of the components that underlie the shape and functionality of this organelle. In mammalian cells, golgins are phosphorylated during mitosis to allow fragmentation of the Golgi ribbon and they also participate in spindle dynamics; both processes are required for cell cycle progression. Little is known about the function of golgins during mitosis in metazoans in vivo. This is particularly significant in Drosophila, in which the Golgi architecture is distributed in numerous units scattered throughout the cytoplasm, in contrast with mammalian cells. We examined the function of the ER/cis-Golgi golgin p115 during the proliferative phase of the Drosophila wing imaginal disc. Knockdown of p115 decreased tissue size. This phenotype was not caused by programmed cell death or cell size reductions, but by a reduction in the final cell number due to an accumulation of cells at the G2/M transition. This phenomenon frequently allows mitotic bypass and re-replication of DNA. These outcomes are similar to those observed following the partial loss of function of positive regulators of Cdk1 in Drosophila. In agreement with this, Cdk1 activation was reduced upon p115 knockdown. Interestingly, these phenotypes were fully rescued by Cdk1 overexpression and partially rescued by Myt1 depletion, but not by String (also known as Cdc25) overexpression. Additionally, we confirmed the physical interaction between p115 and Cdk1, suggesting that the formation of a complex where both proteins are present is essential for the full activation of Cdk1 and thus the correct progression of mitosis in proliferating tissues.
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Affiliation(s)
- Consuelo Ibar
- FONDAP Center for Genome Regulation, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Santiago, Chile.
| | - Álvaro Glavic
- FONDAP Center for Genome Regulation, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Santiago, Chile.
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15
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Abstract
Apoptosis is a physiological program of cell suicide conserved in invertebrates and vertebrates. Apoptosis is crucial to the normal development of organisms and in tissue homeostasis by promoting elimination of unwanted cells, including damaged or virus-infected cells. Due to the importance of programmed cell death for the survival of the organism, a tight regulation is exerted at various activation levels of the cell-death machinery. The utilization of the baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) to identify genes that inhibit the apoptotic process will be described using a transfection-based approach, illustrated by identification of the p49 gene.
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Affiliation(s)
- Nor Chejanovsky
- Entomology Department, Institute of Plant Protection, The Volcani Center, POB 6, Bet Dagan, 50250, Israel.
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16
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Nguyen D, Fayol O, Buisine N, Lecorre P, Uguen P. Functional Interaction between HEXIM and Hedgehog Signaling during Drosophila Wing Development. PLoS One 2016; 11:e0155438. [PMID: 27176767 PMCID: PMC4866710 DOI: 10.1371/journal.pone.0155438] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 04/28/2016] [Indexed: 12/13/2022] Open
Abstract
Studying the dynamic of gene regulatory networks is essential in order to understand the specific signals and factors that govern cell proliferation and differentiation during development. This also has direct implication in human health and cancer biology. The general transcriptional elongation regulator P-TEFb regulates the transcriptional status of many developmental genes. Its biological activity is controlled by an inhibitory complex composed of HEXIM and the 7SK snRNA. Here, we examine the function of HEXIM during Drosophila development. Our key finding is that HEXIM affects the Hedgehog signaling pathway. HEXIM knockdown flies display strong phenotypes and organ failures. In the wing imaginal disc, HEXIM knockdown initially induces ectopic expression of Hedgehog (Hh) and its transcriptional effector Cubitus interuptus (Ci). In turn, deregulated Hedgehog signaling provokes apoptosis, which is continuously compensated by apoptosis-induced cell proliferation. Thus, the HEXIM knockdown mutant phenotype does not result from the apoptotic ablation of imaginal disc; but rather from the failure of dividing cells to commit to a proper developmental program due to Hedgehog signaling defects. Furthermore, we show that ci is a genetic suppressor of hexim. Thus, HEXIM ensures the integrity of Hedgehog signaling in wing imaginal disc, by a yet unknown mechanism. To our knowledge, this is the first time that the physiological function of HEXIM has been addressed in such details in vivo.
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Affiliation(s)
- Duy Nguyen
- UMR-S1174, Univ. Paris-Sud, Inserm, Université Paris-Saclay, Bât. 440, 91405 Orsay, France
| | - Olivier Fayol
- UMR-S1174, Univ. Paris-Sud, Inserm, Université Paris-Saclay, Bât. 440, 91405 Orsay, France
| | | | - Pierrette Lecorre
- UMR-S1174, Univ. Paris-Sud, Inserm, Université Paris-Saclay, Bât. 440, 91405 Orsay, France
| | - Patricia Uguen
- UMR-S1174, Univ. Paris-Sud, Inserm, Université Paris-Saclay, Bât. 440, 91405 Orsay, France
- * E-mail:
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17
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Abstract
For the purpose of this work, insect biotechnology, which is also known as yellow biotechnology, is the use of insects as well as insect-derived cells or molecules in medical (red biotechnology), agricultural (green biotechnology), and industrial (white) biotechnology. It is based on the application of biotechnological techniques on insects or their cells to develop products or services for human use. Such products are then applied in agriculture, medicine, and industrial biotechnology. Insect biotechnology has proven to be a useful resource in diverse industries, especially for the production of industrial enzymes including chitinases and cellulases, pharmaceuticals, microbial insecticides, insect genes, and many other substances. Insect cells (ICs), and particularly lepidopteran cells, constitute a competitive strategy to mammalian cells for the manufacturing of biotechnology products. Among the wide range of methods and expression hosts available for the production of biotech products, ICs are ideal for the production of complex proteins requiring extensive posttranslational modification. The progress so far made in insect biotechnology essentially derives from scientific breakthroughs in molecular biology, especially with the advances in techniques that allow genetic manipulation of organisms and cells. Insect biotechnology has grown tremendously in the last 30 years.
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Affiliation(s)
- Chandrasekar Raman
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas USA
| | - Marian R. Goldsmith
- Biological Sciences Department Center for Biotech. and Life Sciences, University of Rhode Island, Kingston, Rhode Island USA
| | - Tolulope A. Agunbiade
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut USA
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18
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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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19
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Saias L, Swoger J, D’Angelo A, Hayes P, Colombelli J, Sharpe J, Salbreux G, Solon J. Decrease in Cell Volume Generates Contractile Forces Driving Dorsal Closure. Dev Cell 2015; 33:611-21. [DOI: 10.1016/j.devcel.2015.03.016] [Citation(s) in RCA: 90] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 08/18/2014] [Accepted: 03/16/2015] [Indexed: 01/06/2023]
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20
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Akagawa H, Hara Y, Togane Y, Iwabuchi K, Hiraoka T, Tsujimura H. The role of the effector caspases drICE and dcp-1 for cell death and corpse clearance in the developing optic lobe in Drosophila. Dev Biol 2015; 404:61-75. [PMID: 26022392 DOI: 10.1016/j.ydbio.2015.05.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2014] [Revised: 05/13/2015] [Accepted: 05/16/2015] [Indexed: 02/02/2023]
Abstract
In the developing Drosophila optic lobe, cell death occurs via apoptosis and in a distinctive spatio-temporal pattern of dying cell clusters. We analyzed the role of effector caspases drICE and dcp-1 in optic lobe cell death and subsequent corpse clearance using mutants. Neurons in many clusters required either drICE or dcp-1 and each one is sufficient. This suggests that drICE and dcp-1 function in cell death redundantly. However, dying neurons in a few clusters strictly required drICE but not dcp-1, but required drICE and dcp-1 when drICE activity was reduced via hypomorphic mutation. In addition, analysis of the mutants suggests an important role of effecter caspases in corpse clearance. In both null and hypomorphic drICE mutants, greater number of TUNEL-positive cells were observed than in wild type, and many TUNEL-positive cells remained until later stages. Lysotracker staining showed that there was a defect in corpse clearance in these mutants. All the results suggested that drICE plays an important role in activating corpse clearance in dying cells, and that an additional function of effector caspases is required for the activation of corpse clearance as well as that for carrying out cell death.
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Affiliation(s)
- Hiromi Akagawa
- Developmental Biology, Tokyo University of Agriculture and Technology, 3-5-8, Saiwai-cho, Fuchu-shi, Tokyo 183-8509, Japan; Department of Biological Production Science, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan
| | - Yusuke Hara
- Developmental Biology, Tokyo University of Agriculture and Technology, 3-5-8, Saiwai-cho, Fuchu-shi, Tokyo 183-8509, Japan
| | - Yu Togane
- Developmental Biology, Tokyo University of Agriculture and Technology, 3-5-8, Saiwai-cho, Fuchu-shi, Tokyo 183-8509, Japan
| | - Kikuo Iwabuchi
- Department of Biological Production Science, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan
| | - Tsuyoshi Hiraoka
- Department of Biological Production Science, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan
| | - Hidenobu Tsujimura
- Developmental Biology, Tokyo University of Agriculture and Technology, 3-5-8, Saiwai-cho, Fuchu-shi, Tokyo 183-8509, Japan.
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21
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Insect inhibitor-of-apoptosis (IAP) proteins are negatively regulated by signal-induced N-terminal degrons absent within viral IAP proteins. J Virol 2015; 89:4481-93. [PMID: 25653450 DOI: 10.1128/jvi.03659-14] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
UNLABELLED Inhibitor-of-apoptosis (IAP) proteins are key regulators of the innate antiviral response by virtue of their capacity to respond to signals affecting cell survival. In insects, wherein the host IAP provides a primary restriction to apoptosis, diverse viruses trigger rapid IAP depletion that initiates caspase-mediated apoptosis, thereby limiting virus multiplication. We report here that the N-terminal leader of two insect IAPs, Spodoptera frugiperda SfIAP and Drosophila melanogaster DIAP1, contain distinct instability motifs that regulate IAP turnover and apoptotic consequences. Functioning as a protein degron, the cellular IAP leader dramatically shortened the life span of a long-lived viral IAP (Op-IAP3) when fused to its N terminus. The SfIAP degron contains mitogen-activated kinase (MAPK)-like regulatory sites, responsible for MAPK inhibitor-sensitive phosphorylation of SfIAP. Hyperphosphorylation correlated with increased SfIAP turnover independent of the E3 ubiquitin-ligase activity of the SfIAP RING, which also regulated IAP stability. Together, our findings suggest that the SfIAP phospho-degron responds rapidly to a signal-activated kinase cascade, which regulates SfIAP levels and thus apoptosis. The N-terminal leader of dipteran DIAP1 also conferred virus-induced IAP depletion by a caspase-independent mechanism. DIAP1 instability mapped to previously unrecognized motifs that are not found in lepidopteran IAPs. Thus, the leaders of cellular IAPs from diverse insects carry unique signal-responsive degrons that control IAP turnover. Rapid response pathways that trigger IAP degradation and initiate apoptosis independent of canonical prodeath gene (Reaper-Grim-Hid) expression may provide important innate immune advantages. Furthermore, the elimination of these response motifs within viral IAPs, including those of baculoviruses, explains their unusual stability and their potent antiapoptotic activity. IMPORTANCE Apoptosis is an effective means by which a host controls virus infection. In insects, inhibitor-of-apoptosis (IAP) proteins act as regulatory sentinels by responding to cellular signals that determine the fate of infected cells. We discovered that lepidopteran (moth and butterfly) IAPs, which are degraded upon baculovirus infection, are controlled by a conserved phosphorylation-sensitive degron within the IAP N-terminal leader. The degron likely responds to virus-induced kinase-specific signals for degradation through SKP1/Cullin/F-box complex-mediated ubiquitination. Such signal-induced destruction of cellular IAPs is distinct from degradation caused by well-known IAP antagonists, which act to expel IAP-bound caspases. The major implication of this study is that insects have multiple signal-responsive mechanisms by which the sentinel IAPs are actively degraded to initiate host apoptosis. Such diversity of pathways likely provides insects with rapid and efficient strategies for pathogen control. Furthermore, the absence of analogous degrons in virus-encoded IAPs explains their relative stability and antiapoptotic potency.
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22
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Wong HWS, Shaukat Z, Wang J, Saint R, Gregory SL. JNK signaling is needed to tolerate chromosomal instability. Cell Cycle 2013; 13:622-31. [PMID: 24335260 DOI: 10.4161/cc.27484] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Chromosomal instability (CIN), as a common feature of tumors, represents a potential therapeutic target if ways can be found to specifically cause apoptosis in unstably dividing cells. We have previously shown that if signaling through the JNK pathway is reduced, apoptosis is triggered in models of chromosomal instability induced by loss of the spindle checkpoint. Here we identify components upstream and downstream of JNK that are able to mediate this effect, and test the involvement of p53 and DNA damage in causing apoptosis when JNK signaling is reduced in CIN cells. We show that cell cycle progression timing has a strong effect on the apoptosis seen when JNK signaling is reduced in genetically unstable cells: a shortened G 2 phase enhances the apoptosis, while lengthening G 2 rescues the JNK-deficient CIN cell death phenotype. Our findings suggest that chromosomal instability represents a significant stress to dividing cells, and that without JNK signaling, cells undergo apoptosis because they lack a timely and effective response to DNA damage.
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Affiliation(s)
- Heidi W-S Wong
- Department of Genetics; University of Melbourne; Melbourne, VIC, Australia
| | - Zeeshan Shaukat
- School of Molecular and Biomedical Sciences; University of Adelaide; Adelaide, SA, Australia
| | - Jianbin Wang
- Department of Genetics; University of Melbourne; Melbourne, VIC, Australia
| | - Robert Saint
- Department of Genetics; University of Melbourne; Melbourne, VIC, Australia; School of Molecular and Biomedical Sciences; University of Adelaide; Adelaide, SA, Australia
| | - Stephen L Gregory
- School of Molecular and Biomedical Sciences; University of Adelaide; Adelaide, SA, Australia
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23
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Thumbi DK, Béliveau C, Cusson M, Lapointe R, Lucarotti CJ. Comparative genome sequence analysis of Choristoneura occidentalis Freeman and C. rosaceana Harris (Lepidoptera: Tortricidae) alphabaculoviruses. PLoS One 2013; 8:e68968. [PMID: 23861954 PMCID: PMC3702617 DOI: 10.1371/journal.pone.0068968] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Accepted: 06/08/2013] [Indexed: 11/29/2022] Open
Abstract
The complete genome sequences of Choristoneura occidentalis and C. rosaceana nucleopolyhedroviruses (ChocNPV and ChroNPV, respectively) (Baculoviridae: Alphabaculovirus) were determined and compared with each other and with those of other baculoviruses, including the genome of the closely related C. fumiferana NPV (CfMNPV). The ChocNPV genome was 128,446 bp in length (1147 bp smaller than that of CfMNPV), had a G+C content of 50.1%, and contained 148 open reading frames (ORFs). In comparison, the ChroNPV genome was 129,052 bp in length, had a G+C content of 48.6% and contained 149 ORFs. ChocNPV and ChroNPV shared 144 ORFs in common, and had a 77% sequence identity with each other and 96.5% and 77.8% sequence identity, respectively, with CfMNPV. Five homologous regions (hrs), with sequence similarities to those of CfMNPV, were identified in ChocNPV, whereas the ChroNPV genome contained three hrs featuring up to 14 repeats. Both genomes encoded three inhibitors of apoptosis (IAP-1, IAP-2, and IAP-3), as reported for CfMNPV, and the ChocNPV IAP-3 gene represented the most divergent functional region of this genome relative to CfMNPV. Two ORFs were unique to ChocNPV, and four were unique to ChroNPV. ChroNPV ORF chronpv38 is a eukaryotic initiation factor 5 (eIF-5) homolog that has also been identified in the C. occidentalis granulovirus (ChocGV) and is believed to be the product of horizontal gene transfer from the host. Based on levels of sequence identity and phylogenetic analysis, both ChocNPV and ChroNPV fall within group I alphabaculoviruses, where ChocNPV appears to be more closely related to CfMNPV than does ChroNPV. Our analyses suggest that it may be appropriate to consider ChocNPV and CfMNPV as variants of the same virus species.
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Affiliation(s)
- David K. Thumbi
- Natural Resources Canada, Canadian Forest Service – Atlantic Forestry Centre, Fredericton, New Brunswick, Canada
- Sylvar Technologies Inc., Fredericton, New Brunswick, Canada
| | - Catherine Béliveau
- Natural Resources Canada, Canadian Forest Service – Laurentian Forestry Centre, Québec, Quebec, Canada
| | - Michel Cusson
- Natural Resources Canada, Canadian Forest Service – Laurentian Forestry Centre, Québec, Quebec, Canada
| | - Renée Lapointe
- Sylvar Technologies Inc., Fredericton, New Brunswick, Canada
| | - Christopher J. Lucarotti
- Natural Resources Canada, Canadian Forest Service – Atlantic Forestry Centre, Fredericton, New Brunswick, Canada
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24
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Liu B, Behura SK, Clem RJ, Schneemann A, Becnel J, Severson DW, Zhou L. P53-mediated rapid induction of apoptosis conveys resistance to viral infection in Drosophila melanogaster. PLoS Pathog 2013; 9:e1003137. [PMID: 23408884 PMCID: PMC3567152 DOI: 10.1371/journal.ppat.1003137] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Accepted: 12/03/2012] [Indexed: 11/30/2022] Open
Abstract
Arthropod-borne pathogens account for millions of deaths each year. Understanding the genetic mechanisms controlling vector susceptibility to pathogens has profound implications for developing novel strategies for controlling insect-transmitted infectious diseases. The fact that many viruses carry genes that have anti-apoptotic activity has long led to the hypothesis that induction of apoptosis could be a fundamental innate immune response. However, the cellular mechanisms mediating the induction of apoptosis following viral infection remained enigmatic, which has prevented experimental verification of the functional significance of apoptosis in limiting viral infection in insects. In addition, studies with cultured insect cells have shown that there is sometimes a lack of apoptosis, or the pro-apoptotic response happens relatively late, thus casting doubt on the functional significance of apoptosis as an innate immunity. Using in vivo mosquito models and the native route of infection, we found that there is a rapid induction of reaper-like pro-apoptotic genes within a few hours following exposure to DNA or RNA viruses. Recapitulating a similar response in Drosophila, we found that this rapid induction of apoptosis requires the function of P53 and is mediated by a stress–responsive regulatory region upstream of reaper. More importantly, we showed that the rapid induction of apoptosis is responsible for preventing the expression of viral genes and blocking the infection. Genetic changes influencing this rapid induction of reaper-like pro-apoptotic genes led to significant differences in susceptibility to viral infection. Arthropod-borne pathogens account for millions of deaths each year. Understanding the genetic mechanisms controlling arthropod susceptibility to pathogens has profound implications for developing novel strategies for controlling insect-transmitted infectious diseases. Although it was postulated that apoptosis (a genetically controlled form of cellular suicide) may play a very important role in insect innate immunity against viral infection, direct evidence has been lacking due to the lack of knowledge on the regulatory pathways responsible for the induction of apoptosis following viral infection. In this study, we found that there is a rapid induction of pro-apoptotic genes within 1–3 hours of exposure to virus. This rapid pro-apoptotic response was only observed in live animals but not in cultured cells. Genetic analysis indicated that animals lacking this rapid pro-apoptotic response were hypersensitive to viral infection. Thus our work provides unequivocal evidence indicating that rapid induction of apoptosis plays a very important role in mediating insect resistance to viral infection.
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Affiliation(s)
- Bo Liu
- Department of Molecular Genetics and Microbiology & UF Shands Cancer Center, College of Medicine, University of Florida, Gainesville, Florida, United States of America
| | - Susanta K. Behura
- Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Rollie J. Clem
- Division of Biology, Kansas State University, Manhattan, Kansas, United States of America
| | - Anette Schneemann
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - James Becnel
- Center for Medical, Agricultural and Veterinary Entomology, USDA/ARS, Gainesville, Florida, United States of America
| | - David W. Severson
- Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Lei Zhou
- Department of Molecular Genetics and Microbiology & UF Shands Cancer Center, College of Medicine, University of Florida, Gainesville, Florida, United States of America
- * E-mail:
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25
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Rudrapatna VA, Bangi E, Cagan RL. Caspase signalling in the absence of apoptosis drives Jnk-dependent invasion. EMBO Rep 2013; 14:172-7. [PMID: 23306653 DOI: 10.1038/embor.2012.217] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Revised: 12/04/2012] [Accepted: 12/12/2012] [Indexed: 11/09/2022] Open
Abstract
Tumours evolve several mechanisms to evade apoptosis, yet many resected carcinomas show significantly elevated caspase activity. Moreover, caspase activity is positively correlated with tumour aggression and adverse patient outcome. These observations indicate that caspases might have a functional role in promoting tumour invasion and metastasis. Using a Drosophila model of invasion, we show that precise effector caspase activity drives cell invasion without initiating apoptosis. Affected cells express the matrix metalloprotinase Mmp1 and invade by activating Jnk. Our results link Jnk and effector caspase signalling during the invasive process and suggest that tumours under apoptotic stresses from treatment, immune surveillance or intrinsic signals might be induced further along the metastatic cascade.
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Affiliation(s)
- Vivek A Rudrapatna
- Department of Developmental and Regenerative Biology, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, New York 10029, USA
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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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The tumor suppressor Caliban regulates DNA damage-induced apoptosis through p53-dependent and -independent activity. Oncogene 2012; 32:3857-66. [PMID: 22964637 DOI: 10.1038/onc.2012.395] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Revised: 06/04/2012] [Accepted: 07/20/2012] [Indexed: 12/18/2022]
Abstract
We previously identified Caliban (Clbn) as the Drosophila homolog of human Serologically defined colon cancer antigen 1 gene and demonstrated that it could function as a tumor suppressor in human non-small-cell lung cancer (NSCLC) cells, although its mode of action was unknown. Herein, we identify roles for Clbn in DNA damage response. We generate clbn knockout flies using homologous recombination and demonstrate that they have a heightened sensitivity to irradiation. We show that normal Clbn function facilitates both p53-dependent and -independent DNA damage-induced apoptosis. Clbn coordinates different apoptosis pathways, showing a two-stage upregulation following DNA damage. Clbn has proapoptotic functions, working with both caspase and the proapoptotic gene Hid. Finally, ecotopic expression of clbn(+) in NSCLC cells suppresses tumor formation in athymic nude mice. We conclude that Caliban is a regulator of DNA damage-induced apoptosis, functioning as a tumor suppressor in both p53-dependent and -independent pathways.
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Barbosa Viana AA, Pelegrini PB, Grossi-de-Sá MF. Plant biofarming: Novel insights for peptide expression in heterologous systems. Biopolymers 2012. [DOI: 10.1002/bip.22089] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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29
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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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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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31
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Muliyil S, Krishnakumar P, Narasimha M. Spatial, temporal and molecular hierarchies in the link between death, delamination and dorsal closure. Development 2011; 138:3043-54. [PMID: 21693520 DOI: 10.1242/dev.060731] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Dead cells in most epithelia are eliminated by cell extrusion. Here, we explore whether cell delamination in the amnioserosa, a seemingly stochastic event that results in the extrusion of a small fraction of cells and known to provide a force for dorsal closure, is contingent upon the receipt of an apoptotic signal. Through the analysis of mutant combinations and the profiling of apoptotic signals in situ, we establish spatial, temporal and molecular hierarchies in the link between death and delamination. We show that although an apoptotic signal is necessary and sufficient to provide cell-autonomous instructions for delamination, its induction during natural delamination occurs downstream of mitochondrial fragmentation. We further show that apoptotic regulators can influence both delamination and dorsal closure cell non-autonomously, presumably by influencing tissue mechanics. The spatial heterogeneities in delamination frequency and mitochondrial morphology suggest that mechanical stresses may underlie the activation of the apoptotic cascade through their influence on mitochondrial dynamics. Our results document for the first time the temporal propagation of an apoptotic signal in the context of cell behaviours that accomplish morphogenesis during development. They highlight the importance of mitochondrial dynamics and tissue mechanics in its regulation. Together, they provide novel insights into how apoptotic signals can be deployed to pattern tissues.
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Affiliation(s)
- Sonia Muliyil
- Department of Biological Sciences, Tata Institute of Fundamental Research, Colaba, Mumbai, India
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32
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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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33
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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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34
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Kopek BG, Settles EW, Friesen PD, Ahlquist P. Nodavirus-induced membrane rearrangement in replication complex assembly requires replicase protein a, RNA templates, and polymerase activity. J Virol 2010; 84:12492-503. [PMID: 20943974 PMCID: PMC3004334 DOI: 10.1128/jvi.01495-10] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Accepted: 10/04/2010] [Indexed: 12/22/2022] Open
Abstract
Positive-strand RNA [(+)RNA] viruses invariably replicate their RNA genomes on modified intracellular membranes. In infected Drosophila cells, Flock House nodavirus (FHV) RNA replication complexes form on outer mitochondrial membranes inside ∼50-nm, virus-induced spherular invaginations similar to RNA replication-linked spherules induced by many (+)RNA viruses at various membranes. To better understand replication complex assembly, we studied the mechanisms of FHV spherule formation. FHV has two genomic RNAs; RNA1 encodes multifunctional RNA replication protein A and RNA interference suppressor protein B2, while RNA2 encodes the capsid proteins. Expressing genomic RNA1 without RNA2 induced mitochondrial spherules indistinguishable from those in FHV infection. RNA1 mutation showed that protein B2 was dispensable and that protein A was the only FHV protein required for spherule formation. However, expressing protein A alone only "zippered" together the surfaces of adjacent mitochondria, without inducing spherules. Thus, protein A is necessary but not sufficient for spherule formation. Coexpressing protein A plus a replication-competent FHV RNA template induced RNA replication in trans and membrane spherules. Moreover, spherules were not formed when replicatable FHV RNA templates were expressed with protein A bearing a single, polymerase-inactivating amino acid change or when wild-type protein A was expressed with a nonreplicatable FHV RNA template. Thus, unlike many (+)RNA viruses, the membrane-bounded compartments in which FHV RNA replication occurs are not induced solely by viral protein(s) but require viral RNA synthesis. In addition to replication complex assembly, the results have implications for nodavirus interaction with cell RNA silencing pathways and other aspects of virus control.
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Affiliation(s)
- Benjamin G. Kopek
- Institute for Molecular Virology, Howard Hughes Medical Institute, University of Wisconsin—Madison, Madison, Wisconsin
| | - Erik W. Settles
- Institute for Molecular Virology, Howard Hughes Medical Institute, University of Wisconsin—Madison, Madison, Wisconsin
| | - Paul D. Friesen
- Institute for Molecular Virology, Howard Hughes Medical Institute, University of Wisconsin—Madison, Madison, Wisconsin
| | - Paul Ahlquist
- Institute for Molecular Virology, Howard Hughes Medical Institute, University of Wisconsin—Madison, Madison, Wisconsin
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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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Abstract
Cellular apoptosis induced by T cells is mainly mediated by two pathways. One, granule exocytosis utilizes perforin/granzymes. The other involves signaling through death receptors of the TNF-alpha R super-family, especially FasL. Perforin plays a central role in apoptosis induced by granzymes. However, the mechanisms of perforin-mediated cytotoxicity are still not elucidated completely. Perforin is not only a pore-forming protein, but also performs multiple biological functions or perforin performs one biological function (cytolysis), but has multiple biological implications in the cellular immune responses, including regulation of proliferation of CD8+ CTLs.
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Affiliation(s)
- Fang Zhou
- Department of Neurology, 300 Jefferson Hospital for Neurosciences Building, Thomas Jefferson University, 900 Walnut Street, Philadelphia, PA 19107, USA. [corrected]
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37
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Kong M, Zhang YL, Chen X, Chen HJ. Expression of Helicobacter pylori γ-glutamyltransferase in silkworm cells using a baculovirus expression system. Shijie Huaren Xiaohua Zazhi 2009; 17:2996-3000. [DOI: 10.11569/wcjd.v17.i29.2996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To express the Helicobacter pylori (H. pylori) γ-glutamyltransferase (GGT) in silkworm cells using a baculovirus expression system and analyze its activity in vitro.
METHODS: The structure characteristics of the H. pylori ggt gene was analyzed using biological informatics software. The genomic DNA of H. pylori was extracted and used as template to amplify the ggt genes encoding proteins with and without signal peptide by polymerase chain reaction (PCR). After sequencing, the amplified ggt gene encoding protein without signal peptide was fused with a green fluorescent protein (GFP) sequence. Subsequently, the two amplicons and the fusion sequence were cloned into the baculovirus transfer vector pFastBac1, respectively. Bac-to-Bac baculovirus system was then used to generate recombinant virus DNA. Recombinant virus DNA was transfected into silkworm BmN cells to obtain recombinant viruses. The viruses were harvested and used to infect BmN cells again. After infection, BmN cells were harvested to detect protein expression and enzymatic activity. Fluorescence was observed in infected cells using a fluorescence microscope.
RESULTS: The ggt genes encoding proteins with and without signal peptide were successfully cloned by PCR. Sequencing results indicated that no mutations occurred. All the three recombinant viruses obtained could express GGT. The activity of GGT expressed by the recombinant viruses harboring the ggt genes encoding proteins with and without signal peptide and the fusion sequence was 3.61, 10.50 and 9.31 U/L, respectively. Western blot assay demonstrated the expression of GGT-GFP fusion protein. Fluorescent microscopy showed that the fluorescence was distributed throughout the whole cell, indicating that GGT expression is not confined to a certain organelle.
CONCLUSION: GGT with enzymatic activity can be expressed in silkworm cells using the baculovirus expression system.
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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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40
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Neuronal susceptibility to GRIM in Drosophila melanogaster measures the rate of genetic changes that scale to lifespan. Mech Ageing Dev 2009; 130:281-9. [PMID: 19428445 DOI: 10.1016/j.mad.2009.01.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2008] [Revised: 12/22/2008] [Accepted: 01/10/2009] [Indexed: 11/21/2022]
Abstract
Gene expression in Drosophila melanogaster changes significantly throughout life and some of these changes can be delayed by lowering ambient temperature and also by dietary restriction. These two interventions are known to slow the rate of aging as well as the accumulation of damage. It is unknown, however, whether gene expression changes that occur during development and early adult life make an animal more vulnerable to death. Here we develop a method capable of measuring the rate of programmed genetic changes during young adult life in D. melanogaster and show that these changes can be delayed or accelerated in a manner that is predictive of longevity. We show that temperature shifts and dietary restriction, which slow the rate of aging in D. melanogaster, extend the window of neuronal susceptibility to GRIM over-expression in a way that scales to lifespan. We propose that this susceptibility can be used to test compounds and genetic manipulations that alter the onset of senescence by changing the programmed timing of gene expression that correlates and may be causal to aging.
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Abstract
DNA damage or unprotected telomeres can trigger apoptosis via signaling pathways that directly sense abnormal DNA structures and activate the p53 transcription factor. We describe a p53-independent mechanism that acts in parallel to the canonical DNA damage response pathway in Drosophila to induce apoptosis after exposure to ionizing radiation. Following recovery from damage-induced cell cycle arrest, p53 mutant cells activate the JNK pathway and expression of the pro-apoptotic gene hid. Mutations in grp, a cell cycle checkpoint gene, and puc, a negative regulator of the JNK pathway, sensitize p53 mutant cells to ionizing radiation (IR)-induced apoptosis. Induction of chromosome aberrations by DNA damage generates cells with segmental aneuploidy and heterozygous for mutations in ribosomal protein genes. p53-independent apoptosis limits the formation of these aneuploid cells following DNA damage. We propose that reduced copy number of haploinsufficient genes following chromosome damage activates apoptosis and helps maintain genomic integrity.
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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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43
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Insect cell culture and applications to research and pest management. In Vitro Cell Dev Biol Anim 2009; 45:93-105. [DOI: 10.1007/s11626-009-9181-x] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2008] [Accepted: 01/05/2009] [Indexed: 12/11/2022]
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44
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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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45
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Biphasic modulation of apoptotic pathways in Cryptosporidium parvum-infected human intestinal epithelial cells. Infect Immun 2008; 77:837-49. [PMID: 19075026 DOI: 10.1128/iai.00955-08] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The impact of Cryptosporidium parvum infection on host cell gene expression was investigated by microarray analysis with an in vitro model using human ileocecal HCT-8 adenocarcinoma cells. We found changes in 333 (2.6%) transcripts at at least two of the five (6, 12, 24, 48, and 72 h) postinfection time points. Fifty-one of the regulated genes were associated with apoptosis and were grouped into five clusters based on their expression patterns. Early in infection (6 and 12 h), genes with antiapoptotic roles were upregulated and genes with apoptotic roles were downregulated. Later in infection (24, 48, and 72 h), proapoptotic genes were induced and antiapoptotic genes were downregulated, suggesting a biphasic regulation of apoptosis: antiapoptotic state early and moderately proapoptotic state late in infection. This transcriptional profile matched the actual occurrence of apoptosis in the infected cultures. Apoptosis was first detected at 12 h postinfection and increased to a plateau at 24 h, when 20% of infected cells showed nuclear condensation. In contrast, experimental silencing of Bcl-2 induced apoptosis in 50% of infected cells at 12 h postinfection. This resulted in a decrease in the infection rate and a reduction in the accumulation of meront-containing cells. To test the significance of the moderately proapoptotic state late in the infection, we inhibited apoptosis using pancaspase inhibitor Z-VAD-FMK. This treatment also affected the progression of C. parvum infection, as reinfection, normally seen late (24 h to 48 h), did not occur and accumulation of mature meronts was impaired. Control of host apoptosis is complex and crucial to the life of C. parvum. Apoptosis control has at least two components, early inhibition and late moderate promotion. For a successful infection, both aspects appear to be required.
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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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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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Abstract
Apoptosis is a common cellular response to virus infection. However, many viruses have evolved strategies, such as the expression of anti-apoptotic proteins, to combat this response. One such family of anti-apoptotic viral proteins is the p35 family of caspase inhibitors, which are expressed by certain insect viruses. Expression of p35 prevents the host cell from undergoing apoptosis, thereby allowing for propagation of the virus. p35 family members are potent inhibitors of caspases. Members of the family fall into one of three groups that inhibit different classes of caspases. Since the discovery of the first p35 gene in 1991, the anti-apoptotic function of this protein family has been studied extensively. This unique type of protease inhibitor has proven to be extremely useful in the study of apoptosis in experimental settings ranging from nematodes to mammals.
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Affiliation(s)
- John C Means
- Molecular, Cellular & Developmental Biology Program, Arthropod Genomics Center, Division of Biology, Ackert Hall, Kansas State University, Manhattan, KS 66506, USA
| | - Rollie J Clem
- Molecular, Cellular & Developmental Biology Program, Arthropod Genomics Center, Division of Biology, Ackert Hall, Kansas State University, Manhattan, KS 66506, USA
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49
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Inhibition of apoptosis in Cryptosporidium parvum-infected intestinal epithelial cells is dependent on survivin. Infect Immun 2008; 76:3784-92. [PMID: 18519556 DOI: 10.1128/iai.00308-08] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Cryptosporidium parvum is an obligate intracellular protozoan capable of causing severe diarrheal disease in a wide variety of mammals, including humans. C. parvum infection has been associated with induction of apoptosis in exposed epithelial cells, and we now demonstrate that apoptosis is restricted to a subset of cells actively infected with C. parvum. Approximately 20% of the infected cells underwent apoptosis within 48 h of infection, suggesting that the majority of the infected cells are rescued from apoptosis. C. parvum infection resulted in low-level activation of multiple members of the caspase family, including caspase-2, -3, -4, -6, -8, and -9. The kinetics of caspase activation correlated with apoptosis over a 48-h time course. Pan caspase inhibitors reduced apoptosis of epithelial cells infected by C. parvum. Furthermore, C. parvum infection inhibited staurosporine-induced apoptosis and caspase-3/7 activation at 24 h and 48 h. Infection with C. parvum led to upregulation of genes encoding inhibitors of apoptosis proteins (IAPs), including c-IAP1, c-IAP2, XIAP, and survivin. Knockdown of survivin gene expression, but not that of c-IAP1, c-IAP2, or XIAP expression, increased caspase-3/7 activity as well as apoptosis of infected cells and decreased C. parvum 18S rRNA levels. These data suggest that the apoptotic response of infected intestinal epithelial cells is actively suppressed by C. parvum via upregulation of survivin, favoring parasite infection.
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50
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Reactive-site cleavage residues confer target specificity to baculovirus P49, a dimeric member of the P35 family of caspase inhibitors. J Virol 2008; 82:7504-14. [PMID: 18508888 DOI: 10.1128/jvi.00231-08] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Baculovirus proteins P49 and P35 are potent suppressors of apoptosis in diverse organisms. Although related, P49 and P35 inhibit initiator and effector caspases, respectively, during infection of permissive insect cells. The molecular basis of this novel caspase specificity is unknown. To advance strategies for selective inhibition of the cell death caspases, we investigated biochemical differences between these baculovirus substrate inhibitors. We report here that P49 and P35 use similar mechanisms for stoichiometric inhibition that require caspase cleavage of their reactive site loops (RSL) and chemical contributions of a conserved N-terminal cysteine to stabilize the resulting inhibitory complex. Our data indicated that P49 functions as a homodimer that simultaneously binds two caspases. In contrast, P35 is a monomeric, monovalent inhibitor. P49 and P35 also differ in their RSL caspase recognition sequences. We tested the role of the P(4)-P(1) recognition motif for caspase specificity by monitoring virus-induced proteolytic processing of Sf-caspase-1, the principal effector caspase of the host insect Spodoptera frugiperda. When P49's TVTD recognition motif was replaced with P35's DQMD motif, P49 was impaired for inhibition of the initiator caspase that cleaves and activates pro-Sf-caspase-1 and instead formed a stable inhibitory complex with active Sf-caspase-1. In contrast, the effector caspase specificity of P35 was unaltered when P35's DQMD motif was replaced with TVTD. We concluded that the TVTD recognition motif is required but not sufficient for initiator caspase inhibition by P49. Our findings demonstrate a critical role for the P(4)-P(1) recognition site in caspase specificity by P49 and P35 and indicate that additional determinants are involved in target selection.
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