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Abstract
The actin cytoskeleton and its network of associated proteins constitute a physical barrier that viruses must circumvent to gain entry into cells for productive infection. The mechanisms by which the physical signals of infection are sensed by the host to activate an innate immune response are not well understood. The antiviral endoribonuclease RNase L is ubiquitously expressed in a latent form and activated upon binding 2-5A, a unique oligoadenylate produced during viral infections. We provide evidence that RNase L in its inactive form interacts with the actin-binding protein Filamin A to modulate the actin cytoskeleton and inhibit virus entry. Cells lacking either RNase L or Filamin A displayed increased virus entry which was exacerbated in cells lacking both proteins. RNase L deletion mutants that reduced Filamin A interaction displayed a compromised ability to restrict virus entry, supporting the idea of an important role for the RNase L-Filamin A complex in barrier function. Remarkably, both the wild type and a catalytically inactive RNase L mutant were competent to reduce virus entry when transfected into RNase L-deficient cells, indicating that this novel function of RNase L is independent of its enzymatic activity. Virus infection and RNase L activation disrupt its association with Filamin A and release RNase L to mediate its canonical nuclease-dependent antiviral activities. The dual functions of RNase L as a constitutive component of the actin cytoskeleton and as an induced mediator of antiviral signaling and effector functions provide insights into its mechanisms of antiviral activity and opportunities for the development of novel antiviral agents. Cells constantly face and sample pathogens on their outer surface. The actin cytoskeleton and interacting proteins associate with the cell membrane and constitute a barrier to infection. Disruption of the actin cytoskeleton allows viruses to enter the cell and induces innate immune responses to clear infections. The molecular mechanisms that link virus-induced physical perturbations to host defense pathways remain unclear. Our studies identified a novel interaction between the antiviral endoribonuclease RNase L and the actin-binding protein Filamin A that enhances host defense by preventing viral entry into naive cells. This role for RNase L is independent of its enzymatic function. Virus infection alters actin dynamics, disrupts the RNase L-Filamin A complex, and releases RNase L to mediate antiviral signaling and effector functions via its established nucleolytic activities. These dual roles for RNase L provide an efficient strategy to protect cells from infection and rapidly respond upon pathogen exposure.
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Guo L, Li X, Yang S, Xu Y, Tao R, Wulan H, Su C, Han Y. A highly infectious chimeric adenovirus expressing basic fibroblast growth factor exerts potent targeted therapy for rabbit ear chronic ischemic wounds. Plast Reconstr Surg 2014; 134:248e-256e. [PMID: 25068347 DOI: 10.1097/prs.0000000000000364] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
BACKGROUND Poor angiogenesis and impaired proliferation of cells responsible for the repair of chronic ischemic wounds result in impaired wound healing. The continuous and efficient expression of therapeutic factors by means of gene transfection is an ideal adjuvant treatment method to promote cell proliferation and angiogenesis. METHODS A chimeric recombinant adenoviral vector, Ad5F35ET1-bFGF, was constructed that carried the basic fibroblast growth factor (bFGF) gene and used the endothelin-1 promoter to control the targeted expression of bFGF in endothelial cells and fibroblasts. Thus, the authors established a targeted gene therapy for chronic ischemic wounds. RESULTS The chimeric adenovirus Ad5F35ET1-bFGF efficiently infected the endothelin-1-positive endothelial cells and fibroblasts, specifically expressed bFGF, and promoted cell proliferation. In the rabbit wound healing model, the chimeric recombinant adenovirus expressed a high level of bFGF in wound tissues, which continuously promoted angiogenesis and cell proliferation and thus accelerated wound healing. CONCLUSION Targeted gene therapy that uses bFGF as a therapeutic gene provides an effective candidate strategy for the treatment of chronic ischemic wounds.
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Affiliation(s)
- Lingli Guo
- Beijing and Shanghai, People's Republic of China From the Department of Plastic and Reconstructive Surgery, Division of Surgery, Chinese People's Liberation Army General Hospital; and the Department of Molecular Oncology, Eastern Hepatobiliary Surgical Hospital and National Center of Liver Cancer, Second Military Medical University
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53
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Herpes simplex virus internalization into epithelial cells requires Na+/H+ exchangers and p21-activated kinases but neither clathrin- nor caveolin-mediated endocytosis. J Virol 2014; 88:13378-95. [PMID: 25210183 DOI: 10.1128/jvi.03631-13] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
UNLABELLED Herpes simplex virus 1 (HSV-1) is an alphaherpesvirus that has been reported to infect some epithelial cell types by fusion at the plasma membrane but others by endocytosis. To determine the molecular mechanisms of productive HSV-1 cell entry, we perturbed key endocytosis host factors using specific inhibitors, RNA interference (RNAi), or overexpression of dominant negative proteins and investigated their effects on HSV-1 infection in the permissive epithelial cell lines Vero, HeLa, HEp-2, and PtK2. HSV-1 internalization required neither endosomal acidification nor clathrin- or caveolin-mediated endocytosis. In contrast, HSV-1 gene expression and internalization were significantly reduced after treatment with 5-(N-ethyl-N-isopropyl)amiloride (EIPA). EIPA blocks the activity of Na(+)/H(+) exchangers, which are plasma membrane proteins implicated in all forms of macropinocytosis. HSV-1 internalization furthermore required the function of p21-activated kinases that contribute to macropinosome formation. However, in contrast to some forms of macropinocytosis, HSV-1 did not enlist the activities of protein kinase C (PKC), tyrosine kinases, C-terminal binding protein 1, or dynamin to activate its internalization. These data suggest that HSV-1 depends on Na(+)/H(+) exchangers and p21-activated kinases either for macropinocytosis or for local actin rearrangements required for fusion at the plasma membrane or subsequent passage through the actin cortex underneath the plasma membrane. IMPORTANCE After initial replication in epithelial cells, herpes simplex viruses (HSVs) establish latent infections in neurons innervating these regions. Upon primary infection and reactivation from latency, HSVs cause many human skin and neurological diseases, particularly in immunocompromised hosts, despite the availability of effective antiviral drugs. Many viruses use macropinocytosis for virus internalization, and many host factors mediating this entry route have been identified, although the specific perturbation profiles vary for different host and viral cargo. In addition to an established entry pathway via acidic endosomes, we show here that HSV-1 internalization depended on sodium-proton exchangers at the plasma membrane and p21-activated kinases. These results suggest that HSV-1 requires a reorganization of the cortical actin cytoskeleton, either for productive cell entry via pH-independent fusion from macropinosomes or for fusion at the plasma membrane, and subsequent cytosolic passage to microtubules that mediate capsid transport to the nucleus for genome uncoating and replication.
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GASPARINI R, AMICIZIA D, LAI PL, BRAGAZZI NL, PANATTO D. Compounds with anti-influenza activity: present and future of strategies for the optimal treatment and management of influenza. Part I: Influenza life-cycle and currently available drugs. JOURNAL OF PREVENTIVE MEDICINE AND HYGIENE 2014; 55:69-85. [PMID: 25902573 PMCID: PMC4718311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 09/29/2014] [Indexed: 12/01/2022]
Abstract
Influenza is a contagious respiratory acute viral disease characterized by a short incubation period, high fever and respiratory and systemic symptoms. The burden of influenza is very heavy. Indeed, the World Health Organization (WHO) estimates that annual epidemics affect 5-15% of the world's population, causing up to 4-5 million severe cases and from 250,000 to 500,000 deaths. In order to design anti-influenza molecules and compounds, it is important to understand the complex replication cycle of the influenza virus. Replication is achieved through various stages. First, the virus must engage the sialic acid receptors present on the free surface of the cells of the respiratory tract. The virus can then enter the cells by different routes (clathrin-mediated endocytosis or CME, caveolae-dependent endocytosis or CDE, clathrin-caveolae-independent endocytosis, or macropinocytosis). CME is the most usual pathway; the virus is internalized into an endosomal compartment, from which it must emerge in order to release its nucleic acid into the cytosol. The ribonucleoprotein must then reach the nucleus in order to begin the process of translation of its genes and to transcribe and replicate its nucleic acid. Subsequently, the RNA segments, surrounded by the nucleoproteins, must migrate to the cell membrane in order to enable viral assembly. Finally, the virus must be freed to invade other cells of the respiratory tract. All this is achieved through a synchronized action of molecules that perform multiple enzymatic and catalytic reactions, currently known only in part, and for which many inhibitory or competitive molecules have been studied. Some of these studies have led to the development of drugs that have been approved, such as Amantadine, Rimantadine, Oseltamivir, Zanamivir, Peramivir, Laninamivir, Ribavirin and Arbidol. This review focuses on the influenza life-cycle and on the currently available drugs, while potential antiviral compounds for the prevention and treatment of influenza are considered in the subsequent review.
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Affiliation(s)
- R. GASPARINI
- Department of Health Sciences of Genoa University, Genoa, Italy Inter-University Centre for Research on Influenza and Other Transmitted Diseases (CIRI-IT)
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55
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Teigler JE, Kagan JC, Barouch DH. Late endosomal trafficking of alternative serotype adenovirus vaccine vectors augments antiviral innate immunity. J Virol 2014; 88:10354-63. [PMID: 24991003 PMCID: PMC4178875 DOI: 10.1128/jvi.00936-14] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Accepted: 06/24/2014] [Indexed: 12/26/2022] Open
Abstract
UNLABELLED Adenovirus (Ad) vaccine vectors have found widespread use as vaccine platforms against multiple infections and cancers, and multiple serotypes have been shown to differ significantly in their biological properties and immune phenotypes. Our laboratory and others have previously described differential innate immune stimulation elicited by various Ad serotypes. Here, we show that Ad serotype 5 (Ad5) traffics rapidly to the nucleus following infection, whereas Ad35 and Ad26 accumulate in late endosomes 2 to 8 h postinfection. Innate immune cytokine elicitation by all Ad serotypes was abrogated by blockade of endosomal acidification, cathepsin B, and caspase 1, suggesting that virus interactions with acid-dependent sensors, such as Toll-like receptor- and cathepsin-dependent inflammasome activation in late endosomes, may trigger innate immunity. These data suggest a mechanism by which Ad vectors from various serotypes differentially trigger innate antiviral pathways via distinct intracellular trafficking to late endosomes. IMPORTANCE Adenoviruses (Ad) are widely used for vaccination and gene therapy applications. Importantly, Ad vectors have been shown to differ significantly in their innate immune profiles both in vivo and in vitro. The molecular mechanism that underlies these observed differences has important implications for the development of improved vaccines. In this study, we propose a mechanism in which the degree of late endosomal trafficking of Ad vectors results in differential stimulation of late endosomal pattern recognition receptors.
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Affiliation(s)
- Jeffrey E Teigler
- Center for Virology and Vaccine Research, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
| | - Jonathan C Kagan
- Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA
| | - Dan H Barouch
- Center for Virology and Vaccine Research, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA Ragon Institute of MGH, MIT, and Harvard, Boston, Massachusetts, USA
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56
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Bilkova E, Forstova J, Abrahamyan L. Coat as a dagger: the use of capsid proteins to perforate membranes during non-enveloped DNA viruses trafficking. Viruses 2014; 6:2899-937. [PMID: 25055856 PMCID: PMC4113798 DOI: 10.3390/v6072899] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Revised: 07/09/2014] [Accepted: 07/14/2014] [Indexed: 01/24/2023] Open
Abstract
To get access to the replication site, small non-enveloped DNA viruses have to cross the cell membrane using a limited number of capsid proteins, which also protect the viral genome in the extracellular environment. Most of DNA viruses have to reach the nucleus to replicate. The capsid proteins involved in transmembrane penetration are exposed or released during endosomal trafficking of the virus. Subsequently, the conserved domains of capsid proteins interact with cellular membranes and ensure their efficient permeabilization. This review summarizes our current knowledge concerning the role of capsid proteins of small non-enveloped DNA viruses in intracellular membrane perturbation in the early stages of infection.
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Affiliation(s)
- Eva Bilkova
- Department of Genetics and Microbiology, Faculty of Science, Charles University in Prague, Vinicna 5, 12844, Prague 2, Czech Republic.
| | - Jitka Forstova
- Department of Genetics and Microbiology, Faculty of Science, Charles University in Prague, Vinicna 5, 12844, Prague 2, Czech Republic.
| | - Levon Abrahamyan
- Department of Genetics and Microbiology, Faculty of Science, Charles University in Prague, Vinicna 5, 12844, Prague 2, Czech Republic.
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Nagasawa S, Ogura K, Tsutsuki H, Saitoh H, Moss J, Iwase H, Noda M, Yahiro K. Uptake of Shiga-toxigenic Escherichia coli SubAB by HeLa cells requires an actin- and lipid raft-dependent pathway. Cell Microbiol 2014; 16:1582-601. [PMID: 24844382 DOI: 10.1111/cmi.12315] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Revised: 05/07/2014] [Accepted: 05/08/2014] [Indexed: 02/06/2023]
Abstract
The novel cytotoxic factor subtilase cytotoxin (SubAB) is produced mainly by non-O157 Shiga-toxigenic Escherichia coli (STEC). SubAB cleaves the molecular chaperone BiP/GRP78 in the endoplasmic reticulum (ER), leading to activation of RNA-dependent protein kinase (PKR)-like ER kinase (PERK), followed by caspase-dependent cell death. However, the SubAB uptake mechanism in HeLa cells is unknown. In this study, a variety of inhibitors and siRNAs were employed to characterize the SubAB uptake process. SubAB-induced BiP cleavage was inhibited by high concentrations of Dynasore, and methyl-β-cyclodextrin (mβCD) and Filipin III, but not suppressed in clathrin-, dynamin I/II-, caveolin1- and caveolin2-knockdown cells. We observed that SubAB treatment led to dramatic actin rearrangements, e.g. formation of plasma membrane blebs, with a significant increase in fluid uptake. Confocal microscopy analysis showed that SubAB uptake required actin cytoskeleton remodelling and lipid raft cholesterol. Furthermore, internalized SubAB in cells was found in the detergent-resistant domain (DRM) structure. Interestingly, IPA-3, an inhibitor of serine/threonine kinase p21-activated kinase (PAK1), an important protein of macropinocytosis, directly inhibited SubAB-mediated BiP cleavage and SubAB internalization. Thus, our findings suggest that SubAB uses lipid raft- and actin-dependent, but not clathrin-, caveolin- and dynamin-dependent pathways as its major endocytic translocation route.
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Affiliation(s)
- Sayaka Nagasawa
- Department of Legal Medicine, Graduate School of Medicine, Chiba University, Chiba, 260-8670, Japan
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58
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Hendrickx R, Stichling N, Koelen J, Kuryk L, Lipiec A, Greber UF. Innate immunity to adenovirus. Hum Gene Ther 2014; 25:265-84. [PMID: 24512150 DOI: 10.1089/hum.2014.001] [Citation(s) in RCA: 157] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Human adenoviruses are the most widely used vectors in gene medicine, with applications ranging from oncolytic therapies to vaccinations, but adenovirus vectors are not without side effects. In addition, natural adenoviruses pose severe risks for immunocompromised people, yet infections are usually mild and self-limiting in immunocompetent individuals. Here we describe how adenoviruses are recognized by the host innate defense system during entry and replication in immune and nonimmune cells. Innate defense protects the host and represents a major barrier to using adenoviruses as therapeutic interventions in humans. Innate response against adenoviruses involves intrinsic factors present at constant levels, and innate factors mounted by the host cell upon viral challenge. These factors exert antiviral effects by directly binding to viruses or viral components, or shield the virus, for example, soluble factors, such as blood clotting components, the complement system, preexisting immunoglobulins, or defensins. In addition, Toll-like receptors and lectins in the plasma membrane and endosomes are intrinsic factors against adenoviruses. Important innate factors restricting adenovirus in the cytosol are tripartite motif-containing proteins, nucleotide-binding oligomerization domain-like inflammatory receptors, and DNA sensors triggering interferon, such as DEAD (Asp-Glu-Ala-Asp) box polypeptide 41 and cyclic guanosine monophosphate-adenosine monophosphate synthase. Adenovirus tunes the function of antiviral autophagy, and counters innate defense by virtue of its early proteins E1A, E1B, E3, and E4 and two virus-associated noncoding RNAs VA-I and VA-II. We conclude by discussing strategies to engineer adenovirus vectors with attenuated innate responses and enhanced delivery features.
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Affiliation(s)
- Rodinde Hendrickx
- 1 Institute of Molecular Life Sciences, University of Zurich , CH-8057 Zurich, Switzerland
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59
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Majhen D, Calderon H, Chandra N, Fajardo CA, Rajan A, Alemany R, Custers J. Adenovirus-based vaccines for fighting infectious diseases and cancer: progress in the field. Hum Gene Ther 2014; 25:301-17. [PMID: 24580050 DOI: 10.1089/hum.2013.235] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The field of adenovirology is undergoing rapid change in response to increasing appreciation of the potential advantages of adenoviruses as the basis for new vaccines and as vectors for gene and cancer therapy. Substantial knowledge and understanding of adenoviruses at a molecular level has made their manipulation for use as vaccines and therapeutics relatively straightforward in comparison with other viral vectors. In this review we summarize the structure and life cycle of the adenovirus and focus on the use of adenovirus-based vectors in vaccines against infectious diseases and cancers. Strategies to overcome the problem of preexisting antiadenovirus immunity, which can hamper the immunogenicity of adenovirus-based vaccines, are discussed. When armed with tumor-associated antigens, replication-deficient and oncolytic adenoviruses can efficiently activate an antitumor immune response. We present concepts on how to use adenoviruses as therapeutic cancer vaccines and consider some of the strategies used to further improve antitumor immune responses. Studies that explore the prospect of adenoviruses as vaccines against infectious diseases and cancer are underway, and here we give an overview of the latest developments.
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60
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Majhen D, Stojanović N, Vukić D, Pichon C, Leduc C, Osmak M, Ambriović-Ristov A. Increased adenovirus Type 5 mediated transgene expression due to RhoB down-regulation. PLoS One 2014; 9:e86698. [PMID: 24466204 PMCID: PMC3899303 DOI: 10.1371/journal.pone.0086698] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Accepted: 12/13/2013] [Indexed: 01/01/2023] Open
Abstract
Adenovirus type 5 (Ad5) is a non-enveloped DNA virus frequently used as a gene transfer vector. Efficient Ad5 cell entry depends on the availability of its primary receptor, coxsackie and adenovirus receptor, which is responsible for attachment, and integrins, secondary receptors responsible for adenovirus internalization via clathrin-mediated endocytosis. However, efficacious adenovirus-mediated transgene expression also depends on successful trafficking of Ad5 particles to the nucleus of the target cell. It has been shown that changes occurring in tumor cells during development of resistance to anticancer drugs can be beneficial for adenovirus mediated transgene expression. In this study, using an in vitro model consisting of a parental cell line, human laryngeal carcinoma HEp2 cells, and a cisplatin-resistant clone CK2, we investigated the cause of increased Ad5-mediated transgene expression in CK2 as compared to HEp2 cells. We show that the primary cause of increased Ad5-mediated transgene expression in CK2 cells is not modulation of receptors on the cell surface or change in Ad5wt attachment and/or internalization, but is rather the consequence of decreased RhoB expression. We propose that RhoB plays an important role in Ad5 post-internalization events and more particularly in Ad5 intracellular trafficking. To the best of our knowledge, this is the first study showing changed Ad5 trafficking pattern between cells expressing different amount of RhoB, indicating the role of RhoB in Ad5 intracellular trafficking.
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Affiliation(s)
- Dragomira Majhen
- Division of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia
- * E-mail: (DM); (AA)
| | | | - Dunja Vukić
- Division of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia
| | - Chantal Pichon
- Centre de Biophysique Moléculaire CNRS-UPR4301 Affiliated to the Université d'Orléans, Orléans, France
| | - Chloé Leduc
- Centre de Biophysique Moléculaire CNRS-UPR4301 Affiliated to the Université d'Orléans, Orléans, France
| | - Maja Osmak
- Division of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia
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Wilson SS, Wiens ME, Smith JG. Antiviral mechanisms of human defensins. J Mol Biol 2013; 425:4965-80. [PMID: 24095897 PMCID: PMC3842434 DOI: 10.1016/j.jmb.2013.09.038] [Citation(s) in RCA: 198] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2013] [Revised: 09/25/2013] [Accepted: 09/26/2013] [Indexed: 12/21/2022]
Abstract
Defensins are an effector component of the innate immune system with broad antimicrobial activity. Humans express two types of defensins, α- and β-defensins, which have antiviral activity against both enveloped and non-enveloped viruses. The diversity of defensin-sensitive viral species reflects a multitude of antiviral mechanisms. These include direct defensin targeting of viral envelopes, glycoproteins, and capsids in addition to inhibition of viral fusion and post-entry neutralization. Binding and modulation of host cell surface receptors and disruption of intracellular signaling by defensins can also inhibit viral replication. In addition, defensins can function as chemokines to augment and alter adaptive immune responses, revealing an indirect antiviral mechanism. Nonetheless, many questions regarding the antiviral activities of defensins remain. Although significant mechanistic data are known for α-defensins, molecular details for β-defensin inhibition are mostly lacking. Importantly, the role of defensin antiviral activity in vivo has not been addressed due to the lack of a complete defensin knockout model. Overall, the antiviral activity of defensins is well established as are the variety of mechanisms by which defensins achieve this inhibition; however, additional research is needed to fully understand the role of defensins in viral pathogenesis.
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Affiliation(s)
| | | | - Jason G. Smith
- University of Washington School of Medicine, Box 357735, 1705 North East Pacific Street, Seattle, WA 98195, USA
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Uptake of advanced glycation end products by proximal tubule epithelial cells via macropinocytosis. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:2922-2932. [DOI: 10.1016/j.bbamcr.2013.05.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Revised: 05/15/2013] [Accepted: 05/28/2013] [Indexed: 11/15/2022]
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63
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Chen RF, Lee CY. Adenoviruses types, cell receptors and local innate cytokines in adenovirus infection. Int Rev Immunol 2013; 33:45-53. [PMID: 24127823 DOI: 10.3109/08830185.2013.823420] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Adenovirus is a common infectious pathogen in both children and adults. It is a significant cause of morbidity in immunocompetent people living in crowded living conditions and of mortality in immunocompromised hosts. It has more recently become a popular vehicle for gene therapy applications. The host response to wild-type infection and gene therapy vector exposure involves both virus entry receptor and the innate immune systems. Cell-mediated recognition of viruses via capsid components has received significant attention, principally thought to be regulated by the coxsackievirus-adenovirus receptor (CAR), CD46, integrins and heparin sulfate-containing proteoglycans. Antiviral innate immune responses are initiated by the infected cell, which activates the interferon response to block viral replication, while simultaneously releasing chemokines to attract neutrophils and NK cells. This review discusses the innate immune response primarily during wild-type adenovirus infection because this serves as the basis for understanding the response during both natural infection and exposure to adenovirus vectors.
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Affiliation(s)
- Rong-Fu Chen
- 1Department of Medical Research and Development, Show Chwan Health Care System, Changhua, Taiwan
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64
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Caveolin-1 associated adenovirus entry into human corneal cells. PLoS One 2013; 8:e77462. [PMID: 24147000 PMCID: PMC3795695 DOI: 10.1371/journal.pone.0077462] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Accepted: 09/09/2013] [Indexed: 12/27/2022] Open
Abstract
The cellular entry of viruses represents a critical area of study, not only for viral tropism, but also because viral entry dictates the nature of the immune response elicited upon infection. Epidemic keratoconjunctivitis (EKC), caused by viruses within human adenovirus species D (HAdV-D), is a severe, ocular surface infection associated with corneal inflammation. Clathrin-mediated endocytosis has previously been shown to play a critical role in entry of other HAdV species into many host cell types. However, HAdV-D endocytosis into corneal cells has not been extensively studied. Herein, we show an essential role for cholesterol rich, lipid raft microdomains and caveolin-1, in the entry of HAdV-D37 into primary human corneal fibroblasts. Cholesterol depletion using methyl-β-cyclodextrin (MβCD) profoundly reduced viral infection. When replenished with soluble cholesterol, the effect of MβCD was reversed, allowing productive viral infection. HAdV-D37 DNA was identified in caveolin-1 rich endosomal fractions after infection. Src kinase activity was also increased in caveolin-1 rich endosomal fractions after infection, and Src phosphorylation and CXCL1 induction were both decreased in caveolin-1-/- mice corneas compared to wild type mice. siRNA knock down of caveolin-1 in corneal cells reduced chemokine induction upon viral infection, and caveolin-1-/- mouse corneas showed reduced cellular entry of HAdV-D37. As a control, HAdV-C2, a non-corneal pathogen, appeared to utilize the caveolar pathway for entry into A549 cells, but failed to infect corneal cells entirely, indicating virus and cell specific tropism. Immuno-electron microscopy confirmed the presence of caveolin-1 in HAdV-D37-containing vesicles during the earliest stages of viral entry. Collectively, these experiments indicate for the first time that HAdV-D37 uses a lipid raft mediated caveolin-1 associated pathway for entry into corneal cells, and connects the processes of viral entry with downstream proinflammatory cell signaling.
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65
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A direct and versatile assay measuring membrane penetration of adenovirus in single cells. J Virol 2013; 87:12367-79. [PMID: 24027314 DOI: 10.1128/jvi.01833-13] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Endocytosis is the most prevalent entry port for viruses into cells, but viruses must escape from the lumen of endosomes to ensure that viral genomes reach a site for replication and progeny formation. Endosomal escape also helps viruses bypass endolysosomal degradation and presentation to certain Toll-like intrinsic immunity receptors. The mechanisms for cytosolic delivery of nonenveloped viruses or nucleocapsids from enveloped viruses are poorly understood, in part because no quantitative assays are readily available which directly measure the penetration of viruses into the cytosol. Following uptake by clathrin-mediated endocytosis or macropinocytosis, the nonenveloped adenoviruses penetrate from endosomes to the cytosol, and they traffic with cellular motors on microtubules to the nucleus for replication. In this report, we present a novel single-cell imaging assay which quantitatively measures individual cytosolic viruses and distinguishes them from endosomal viruses or viruses at the plasma membrane. Using this assay, we showed that the penetration of human adenoviruses of the species C and B occurs rapidly after virus uptake. Efficient penetration does not require acidic pH in endosomes. This assay is versatile and can be adapted to other adenoviruses and members of other nonenveloped and enveloped virus families.
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66
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Wong LLY, Lam IPY, Wong TYN, Lai WL, Liu HF, Yeung LL, Ching YP. IPA-3 inhibits the growth of liver cancer cells by suppressing PAK1 and NF-κB activation. PLoS One 2013; 8:e68843. [PMID: 23894351 PMCID: PMC3716906 DOI: 10.1371/journal.pone.0068843] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Accepted: 06/03/2013] [Indexed: 12/19/2022] Open
Abstract
Hepatocellular carcinoma (HCC) is one of the major malignancies worldwide and is associated with poor prognosis due to the high incidences of metastasis and tumor recurrence. Our previous study showed that overexpression of p21-activated protein kinase 1 (PAK1) is frequently observed in HCC and is associated with a more aggressive tumor behavior, suggesting that PAK1 is a potential therapeutic target in HCC. In the current study, an allosteric small molecule PAK1 inhibitor, IPA-3, was evaluated for the potential in suppressing hepatocarcinogenesis. Consistent with other reports, inhibition of PAK1 activity was observed in several human HCC cell lines treated with various dosages of IPA-3. Using cell proliferation, colony formation and BrdU incorporation assays, we demonstrated that IPA-3 treatment significantly inhibited the growth of HCC cells. The mechanisms through which IPA-3 treatment suppresses HCC cell growth are enhancement of apoptosis and blockage of activation of NF-κB. Furthermore, our data suggested that IPA-3 not only inhibits the HCC cell growth, but also suppresses the metastatic potential of HCC cells. Nude mouse xenograft assay demonstrated that IPA-3 treatment significantly reduced the tumor growth rate and decreased tumor volume, indicating that IPA-3 can suppress the in vivo tumor growth of HCC cells. Taken together, our demonstration of the potential preclinical efficacy of IPA-3 in HCC provides the rationale for cancer therapy.
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Affiliation(s)
- Leo Lap-Yan Wong
- Department of Anatomy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- Center for Cancer Research, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Ian Pak-Yan Lam
- Department of Anatomy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- Center for Cancer Research, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Tracy Yuk-Nar Wong
- Department of Anatomy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Wai-Lung Lai
- Department of Anatomy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- Center for Cancer Research, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Heong-Fai Liu
- Department of Anatomy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Lam-Lung Yeung
- Department of Chemistry, Hong Kong University of Science and Technology, Hong Kong, China
| | - Yick-Pang Ching
- Department of Anatomy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- State Key Laboratory of Liver Research, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- State Key Laboratory of Brain and Cognitive Science, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- * E-mail:
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Mercer J, Greber UF. Virus interactions with endocytic pathways in macrophages and dendritic cells. Trends Microbiol 2013; 21:380-8. [PMID: 23830563 DOI: 10.1016/j.tim.2013.06.001] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Revised: 06/03/2013] [Accepted: 06/05/2013] [Indexed: 12/20/2022]
Abstract
Macrophages and dendritic cells (DCs) are at the front line of defence against fungi, bacteria, and viruses. Together with physical barriers, such as mucus and a range of antimicrobial compounds, they constitute a major part of the intrinsic and innate immune systems. They have elaborate features, including pattern recognition receptors (PRRs) and specialized endocytic mechanisms, cytokines and chemokines, and the ability to call on reserves. As masters of manipulation and counter-attack, viruses shunt intrinsic and innate recognition, enter immune cells, and spread from these cells throughout an organism. Here, we review mechanisms by which viruses subvert endocytic and pathogen-sensing functions of macrophages and DCs, while highlighting possible strategic advantages of infecting cells normally tuned into pathogen destruction.
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Affiliation(s)
- Jason Mercer
- Eidgenössische Technische Hochschule (ETH) Zürich, Institute of Biochemistry, Schafmattstr. 18, CH-8093, Zürich, Switzerland.
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68
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Aslan JE, Baker SM, Loren CP, Haley KM, Itakura A, Pang J, Greenberg DL, David LL, Manser E, Chernoff J, McCarty OJT. The PAK system links Rho GTPase signaling to thrombin-mediated platelet activation. Am J Physiol Cell Physiol 2013; 305:C519-28. [PMID: 23784547 DOI: 10.1152/ajpcell.00418.2012] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Regulation of the platelet actin cytoskeleton by the Rho family of small GTPases is essential for the proper maintenance of hemostasis. However, little is known about how intracellular platelet activation from Rho GTPase family members, including Rac, Cdc42, and Rho, translate into changes in platelet actin structures. To better understand how Rho family GTPases coordinate platelet activation, we identified platelet proteins associated with Rac1, a Rho GTPase family member, and actin regulatory protein essential for platelet hemostatic function. Mass spectrometry analysis revealed that upon platelet activation with thrombin, Rac1 associates with a set of effectors of the p21-activated kinases (PAKs), including GIT1, βPIX, and guanine nucleotide exchange factor GEFH1. Platelet activation by thrombin triggered the PAK-dependent phosphorylation of GIT1, GEFH1, and other PAK effectors, including LIMK1 and Merlin. PAK was also required for the thrombin-mediated activation of the MEK/ERK pathway, Akt, calcium signaling, and phosphatidylserine (PS) exposure. Inhibition of PAK signaling prevented thrombin-induced platelet aggregation and blocked platelet focal adhesion and lamellipodia formation in response to thrombin. Together, these results demonstrate that the PAK signaling system is a key orchestrator of platelet actin dynamics, linking Rho GTPase activation downstream of thrombin stimulation to PAK effector function, MAP kinase activation, calcium signaling, and PS exposure in platelets.
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Affiliation(s)
- Joseph E Aslan
- Department of Biomedical Engineering, Oregon Health & Science University, Portland, Oregon, USA
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69
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Aslan JE, Itakura A, Haley KM, Tormoen GW, Loren CP, Baker SM, Pang J, Chernoff J, McCarty OJT. p21 activated kinase signaling coordinates glycoprotein receptor VI-mediated platelet aggregation, lamellipodia formation, and aggregate stability under shear. Arterioscler Thromb Vasc Biol 2013; 33:1544-51. [PMID: 23640496 DOI: 10.1161/atvbaha.112.301165] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
OBJECTIVE Rho GTPase proteins play a central role in regulating the dynamics of the platelet actin cytoskeleton. Yet, little is known regarding how Rho GTPase activation coordinates platelet activation and function. In this study, we aimed to characterize the role of the Rho GTPase effector, p21 activated kinase (PAK), in platelet activation, lamellipodia formation, and aggregate formation under shear. APPROACH AND RESULTS Stimulation of platelets with the glycoprotein receptor VI agonist, collagen-related peptide, rapidly activated PAK in a time course preceding phosphorylation of PAK substrates, LIM domain kinase LIMK1 and the MAPK/ERK kinase MEK, and the subsequent activation of MAPKs and Akt. Pharmacological inhibitors of PAK blocked signaling events downstream of PAK and prevented platelet secretion as well as platelet aggregation in response to collagen-related peptide. PAK inhibitors also prevented PAK activation and platelet spreading on collagen surfaces. PAK was also required for the formation of platelet aggregates and to maintain aggregate stability under physiological shear flow conditions. CONCLUSIONS These results suggest that PAK serves as an orchestrator of platelet functional responses after activation downstream of the platelet collagen receptor, glycoprotein receptor VI.
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Affiliation(s)
- Joseph E Aslan
- Department of Biomedical Engineering, Division of Hematology and Medical Oncology, Oregon Health & Science University, Portland, OR 97239, USA.
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Sun E, He J, Zhuang X. Live cell imaging of viral entry. Curr Opin Virol 2013; 3:34-43. [PMID: 23395264 PMCID: PMC3587724 DOI: 10.1016/j.coviro.2013.01.005] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 12/14/2012] [Accepted: 01/21/2013] [Indexed: 12/17/2022]
Abstract
Viral entry encompasses the initial steps of infection starting from virion host cell attachment to viral genome release. Given the dynamic interactions between the virus and the host, many questions related to viral entry can be directly addressed by live cell imaging. Recent advances in fluorescent labeling of viral and cellular components, fluorescence microscopy with high sensitivity and spatiotemporal resolution, and image analysis enabled studies of a broad spectrum across many viral entry steps, including virus-receptor interactions, internalization, intracellular transport, genomic release, nuclear transport, and cell-to-cell transmission. Collectively, these live cell imaging studies have not only enriched our understandings of the viral entry mechanisms, but also provided novel insights into basic cellular biology processes.
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Affiliation(s)
- Eileen Sun
- Program in Virology, Harvard Medical School, Boston, MA 02115, United States
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72
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Wolfrum N, Greber UF. Adenovirus signalling in entry. Cell Microbiol 2012; 15:53-62. [PMID: 23083122 DOI: 10.1111/cmi.12053] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Revised: 10/12/2012] [Accepted: 10/15/2012] [Indexed: 12/15/2022]
Abstract
Viruses carry nucleic acids between and within host cells. Invariably, virus attachment to host cells leads to activation of cell signalling. These so-called forward signals emerge from interactions with cell surface receptors or cytosolic proteins and elicit profound responses in the cells, for example induction of growth or innate immunity responses. They can enhance or suppress infection. In addition, viruses receive signals from the cell. These reverse signals can impact on the structure of the virus leading to genome uncoating. They can enhance infection or inactivate virus, for example by facilitating degradation. Here we discuss the nature and mechanisms by which forward and reverse signals emerge and affect the outcome of human adenovirus infections. We describe how human adenoviruses use cell surface receptors for forward signalling to activate cell growth, intracellular transport or innate immune response. We also discuss how adenoviruses use acto-myosin, integrins or microtubule-based kinesin motors for reverse signalling to facilitate their stepwise uncoating programme.
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Affiliation(s)
- Nina Wolfrum
- Institute of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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73
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Japanese encephalitis virus infects neuronal cells through a clathrin-independent endocytic mechanism. J Virol 2012; 87:148-62. [PMID: 23055570 DOI: 10.1128/jvi.01399-12] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Japanese encephalitis virus (JEV) is a mosquito-borne pathogenic flavivirus responsible for acute viral encephalitis in humans. The cellular entry of JEV is poorly characterized in terms of molecular requirements and pathways. Here we present a systematic study of the internalization mechanism of JEV in fibroblasts and neuroblastoma cells. To verify the roles of distinct pathways of cell entry, we used fluorescently labeled virus particles, a combination of pharmacological inhibitors, RNA interference (RNAi), and dominant-negative (DN) mutants of regulatory proteins involved in endocytosis. Our study demonstrates that JEV infects fibroblasts in a clathrin-dependent manner, but it deploys a clathrin-independent mechanism to infect neuronal cells. The clathrin-independent pathway requires dynamin and plasma membrane cholesterol. Virus binding to neuronal cells leads to rapid actin rearrangements and an intact and dynamic actin cytoskeleton, and the small GTPase RhoA plays an important role in viral entry. Immunofluorescence analysis of viral colocalization with endocytic markers showed that JEV traffics through Rab5-positive early endosomes and that release of the viral nucleocapsid occurs at the level of the early and not the late endosomes.
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74
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Conserved fiber-penton base interaction revealed by nearly atomic resolution cryo-electron microscopy of the structure of adenovirus provides insight into receptor interaction. J Virol 2012; 86:12322-9. [PMID: 22951835 DOI: 10.1128/jvi.01608-12] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Adenovirus (Ad) cell attachment is initiated by the attachment of the fiber protein to a primary receptor (usually CAR or CD46). This event is followed by the engagement of the penton base protein with a secondary receptor (integrin) via its loop region, which contains an Arg-Gly-Asp (RGD) motif, to trigger virus internalization. To understand the well-orchestrated adenovirus cell attachment process that involves the fiber and the penton base, we reconstructed the structure of an Ad5F35 capsid, comprising an adenovirus type 5 (Ad5) capsid pseudotyped with an Ad35 fiber, at a resolution of approximately 4.2 Å. The fiber-penton base interaction in the cryo-electron microscopic (cryo-EM) structure of Ad5F35 is similar to that in the cryo-EM structure of Ad5, indicating that the fiber-penton base interaction of adenovirus is conserved. Our structure also confirms that the C-terminal segment of the fiber tail domain constitutes the bottom trunk of the fiber shaft. Based on the conserved fiber-penton base interaction, we have proposed a model for the interaction of Ad5F35 with its primary and secondary receptors. This model could provide insight for designing adenovirus gene delivery vectors.
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75
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Vaccination with adenovirus serotypes 35, 26, and 48 elicits higher levels of innate cytokine responses than adenovirus serotype 5 in rhesus monkeys. J Virol 2012; 86:9590-8. [PMID: 22787208 DOI: 10.1128/jvi.00740-12] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Adenovirus (Ad) vaccine vectors have proven highly immunogenic in multiple experimental models, but the innate immune responses induced by these vectors remain poorly characterized. Here we report innate cytokine responses to 5 different Ad vectors in 26 rhesus monkeys. Vaccination with adenovirus serotype 35 (Ad35), Ad26, and Ad48 induced substantially higher levels of antiviral (gamma interferon [IFN-γ], 10-kDa gamma interferon-induced protein [IP-10]) and proinflammatory (interleukin 1 receptor antagonist [IL-1RA], IL-6) cytokines than vaccination with Ad5 on day 1 following immunization. In vitro studies with capsid chimeric vectors and receptor-blocking monoclonal antibodies suggested that fiber-receptor interactions, as well as other capsid components, were critical for triggering these innate responses. Moreover, multiple cell populations, including dendritic cells, monocytes/macrophages, and T lymphocytes, contributed to these innate cytokine profiles. These data demonstrate that Ad35, Ad26, and Ad48, which utilize CD46 as their primary cellular receptor, induce significantly greater innate cytokine responses than Ad5, which uses the coxsackievirus and adenovirus receptor (CAR). These differences in innate triggering result in markedly different immunologic milieus for the subsequent generation of adaptive immune responses by these vaccine vectors.
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76
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Mercer J, Helenius A. Gulping rather than sipping: macropinocytosis as a way of virus entry. Curr Opin Microbiol 2012; 15:490-9. [PMID: 22749376 DOI: 10.1016/j.mib.2012.05.016] [Citation(s) in RCA: 151] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Revised: 05/25/2012] [Accepted: 05/31/2012] [Indexed: 12/18/2022]
Abstract
Macropinocytosis has emerged as a major endocytic mechanism in the cell entry of animal viruses. The process differs fundamentally from other endocytic mechanisms involved in virus internalization. By activating growth factor receptors or other signaling molecules, plasma membrane-bound viruses trigger the activation of a signaling pathway. When amplified, this causes a transient, global change in cell behavior. The consequences of this change include the actin-dependent formation of membrane protrusions, the elevation of non-specific uptake of fluid, and the internalization of membrane together with surface-bound ligands and particles including viruses. Recent studies show that this strategy is used by a variety of enveloped and non-enveloped viruses.
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Affiliation(s)
- Jason Mercer
- ETH Zürich, Institute of Biochemistry, Zürich, Switzerland.
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77
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Sun Y, Tien P. From endocytosis to membrane fusion: emerging roles of dynamin in virus entry. Crit Rev Microbiol 2012; 39:166-79. [PMID: 22737978 DOI: 10.3109/1040841x.2012.694412] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Dynamin, a large guanosine triphosphatase (GTPase), has been implicated in virus entry, but its mechanisms of action are controversial. The entry procedure of most enveloped viruses involves endocytosis and membrane fusion. Dynamin has been suggested to act both as a regulatory GTPase by controlling the early stages of clathrin-mediated endocytosis (CME), which is an important endocytic pathway utilized by many viruses, and as a mechanochemical enzyme that induces membrane fission and pinches endocytic vesicles off from the cellular plasma membrane in later stages in several endocytic pathways, including CME. In addition to its involvement in virus endocytosis, dynamin has also been proposed to participate in membrane fusion between the virus and endosomes following endocytosis. Crystal structures and cryo-electron micrography (cryo-EM) have elucidated the structure of dynamin, which led to development of a mechanochemical model of how dynamin-mediated membrane fission occurs. Based on this, we propose a hypothetical model that explains how dynamin facilitates virus membrane fusion and discuss its roles in virus entry.
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Affiliation(s)
- Yeping Sun
- Center for Molecular Virology, CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
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78
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Abstract
Defensins are small, multifunctional cationic peptides. They typically contain six conserved cysteines whose three intramolecular disulfides stabilize a largely β-sheet structure. This review of human α-defensins begins by describing their evolution, including their likely relationship to the Big Defensins of invertebrates, and their kinship to the β-defensin peptides of many if not all vertebrates, and the θ-defensins found in certain non-human primates. We provide a short history of the search for leukocyte-derived microbicidal molecules, emphasizing the roles played by luck (good), preconceived notions (mostly bad), and proper timing (essential). The antimicrobial, antiviral, antitoxic, and binding properties of human α-defensins are summarized. The structural features of α-defensins are described extensively and their functional contributions are assessed. The properties of HD6, an enigmatic Paneth cell α-defensin, are contrasted with those of the four myeloid α-defensins (HNP1-4) and of HD5, the other α-defensin of human Paneth cells. The review ends with a decalogue that may assist researchers or students interested in α-defensins and related aspects of neutrophil function.
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Affiliation(s)
- Robert I Lehrer
- Department of Medicine and Molecular Biology Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1688, USA.
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79
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Yumoto R, Suzuka S, Oda K, Nagai J, Takano M. Endocytic uptake of FITC-albumin by human alveolar epithelial cell line A549. Drug Metab Pharmacokinet 2012; 27:336-43. [PMID: 22214936 DOI: 10.2133/dmpk.dmpk-11-rg-127] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The uptake mechanism of FITC-labeled albumin (FITC-albumin) was examined in human alveolar epithelial cell line A549. FITC-albumin uptake by A549 cells was time- and temperature-dependent, and was markedly suppressed at 4°C compared with that at 37°C. The uptake was saturable, and was mediated by a high-affinity, low-capacity system and by a low-affinity, high-capacity system. In the following experiments, we focused on the low-affinity system. FITC-albumin uptake was markedly inhibited by metabolic inhibitors and by a vacuolar H⁺-ATPase, bafilomycin A₁. The uptake was inhibited by clathrin-mediated endocytosis inhibitors (phenylarsine oxide and chlorpromazine). Potassium depletion and hypertonicity that inhibit clathrin-mediated endocytosis also decreased FITC-albumin uptake. On the other hand, caveolae-mediated endocytosis inhibitors (indomethacin and nystatin) did not affect FITC-albumin uptake. In addition, FITC-albumin uptake was inhibited by macropinocytosis inhibitors such as 5-(N-ethyl-N-isopropyl) amiloride. These results suggest that the low-affinity system of FITC-albumin uptake is mediated by endocytosis in A549 cells, predominantly via a clathrin-mediated pathway. Macropinocytosis, but not caveolae-mediated endocytosis, may also be involved. Considering our previous findings, albumin may be transported by a similar mechanism and/or pathway in rat and human alveolar epithelial cells.
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Affiliation(s)
- Ryoko Yumoto
- Department of Pharmaceutics and Therapeutics, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan
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80
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Chan PM, Manser E. PAKs in Human Disease. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 106:171-87. [DOI: 10.1016/b978-0-12-396456-4.00011-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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81
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Fejer G, Freudenberg M, Greber UF, Gyory I. Adenovirus-triggered innate signalling pathways. Eur J Microbiol Immunol (Bp) 2011; 1:279-88. [PMID: 24516734 DOI: 10.1556/eujmi.1.2011.4.3] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Accepted: 10/15/2011] [Indexed: 02/06/2023] Open
Abstract
Adenoviruses are important infectious agents and also emerging vectors in different biomedical applications. These viruses elicit a strong innate and adaptive immune response, which influences both the course of disease and the success of the applied vectors. Several Toll-like Receptor (TLR)-dependent and -independent mechanisms contribute to these responses. Understanding of the involved viral and cellular factors is crucial for the treatment of various adenovirus diseases and the optimal design of adenovirus vector applications. Here we summarize our current understanding of the complex nature of adenovirus-induced innate immune mechanisms.
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82
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The actin cytoskeleton as a barrier to virus infection of polarized epithelial cells. Viruses 2011; 3:2462-77. [PMID: 22355449 PMCID: PMC3280511 DOI: 10.3390/v3122462] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 12/07/2011] [Accepted: 12/15/2011] [Indexed: 12/12/2022] Open
Abstract
Many diverse viruses target a polarized epithelial monolayer during host invasion. The polarized epithelium is adept at restricting the movement of solutes, ions, macromolecules, and pathogens across the mucosa. This regulation can be attributed to the presence of a junctional complex between adjacent cells and to an intricate network of actin filaments that provides support to the subapical membrane and stabilizes intercellular junctions. It is therefore not surprising that many viruses have evolved highly varied strategies to dissolve or modulate the cortical actin meshwork to promote infection of polarized cells. In this review, we will discuss the cell biological properties of the actin cytoskeleton in polarized epithelial cells and review the known mechanisms utilized by viral pathogens to manipulate this system in order to facilitate their infection.
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83
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Avidity binding of human adenovirus serotypes 3 and 7 to the membrane cofactor CD46 triggers infection. J Virol 2011; 86:1623-37. [PMID: 22130529 DOI: 10.1128/jvi.06181-11] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The species B human adenoviruses (HAdVs) infect cells upon attaching to CD46 or desmoglein 2 (DSG-2) by one or several of their 12 fiber knob trimers (FKs). To test whether DSG-2 and CD46 simultaneously serve as virus receptors for adenovirus type 3 (Ad3), we performed individual and combined CD46/DSG-2 loss-of-function studies in human lung A549 and 16HBE14o cells. Our results suggest that in these cells, DSG-2 functions as a major attachment receptor for Ad3, whereas CD46 exerts a minor contribution to virus attachment and uptake in the range of ∼10%. However, in other cells the role of CD46 may be more pronounced depending on, e.g., the expression levels of the receptors. To test if avidity allows Ad3/7 to use CD46 as a receptor, we performed gain-of-function studies. The cell surface levels of ectopically expressed CD46 in CHO or human M010119 melanoma cells lacking DSG-2 positively correlated with Ad3/7 infections, while Ad11/35 infections depended on CD46 but less on CD46 levels. Antibody-cross-linked soluble CD46 blocked Ad3/7/11/35 infections, while soluble CD46 alone blocked Ad11/35 but not Ad3/7. Soluble Ad3/7-FKs poorly inhibited Ad3/7 infection of CHO-CD46 cells, illustrating that Ad3/7-FKs bind with low affinity to CD46. This was confirmed by Biacore studies. Ad3/7-FK binding to immobilized CD46 at low density was not detected, unlike that of Ad11/35-FK. At higher CD46 densities, however, Ad3/7-FK bound to CD46 with only 15-fold-higher dissociation constants than those of Ad11/35-FK. These data show that an avidity mechanism for Ad3/7 binding to CD46 leads to infection of CD46-positive cells.
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84
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Vaccinia extracellular virions enter cells by macropinocytosis and acid-activated membrane rupture. EMBO J 2011; 30:3647-61. [PMID: 21792173 PMCID: PMC3181475 DOI: 10.1038/emboj.2011.245] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Accepted: 06/29/2011] [Indexed: 11/12/2022] Open
Abstract
Double membrane-bound vaccinia extracellular virions actively promote their own macropinocytosis. This, followed by acid-induced rupture of the outer membrane in endocytic vesicles, exposes the inner membrane for fusion with the endocytic membrane and release into the cytosol. Vaccinia virus (VACV), the model poxvirus, produces two types of infectious particles: mature virions (MVs) and extracellular virions (EVs). EV particles possess two membranes and therefore require an unusual cellular entry mechanism. By a combination of fluorescence and electron microscopy as well as flow cytometry, we investigated the cellular processes that EVs required to infect HeLa cells. We found that EV particles were endocytosed, and that internalization and infection depended on actin rearrangements, activity of Na+/H+ exchangers, and signalling events typical for the macropinocytic mechanism of endocytosis. To promote their internalization, EVs were capable of actively triggering macropinocytosis. EV infection also required vacuolar acidification, and acid exposure in endocytic vacuoles was needed to disrupt the outer EV membrane. Once exposed, the underlying MV-like particle presumably fused its single membrane with the limiting vacuolar membrane. Release of the viral core into the host cell cytosol allowed for productive infection.
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Hampson IN, Oliver AW, Hampson L. Targeting activated Rho proteins: a new approach for treatment of HPV and other virus-related cancers? Expert Rev Anticancer Ther 2011; 11:973-6. [DOI: 10.1586/era.11.86] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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86
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Meng H, Yang S, Li Z, Xia T, Chen J, Ji Z, Zhang H, Wang X, Lin S, Huang C, Zhou ZH, Zink JI, Nel AE. Aspect ratio determines the quantity of mesoporous silica nanoparticle uptake by a small GTPase-dependent macropinocytosis mechanism. ACS NANO 2011; 5:4434-47. [PMID: 21563770 PMCID: PMC3125420 DOI: 10.1021/nn103344k] [Citation(s) in RCA: 253] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Although the aspect ratio (AR) of engineered nanomaterials (ENMs) is one of the key physicochemical parameters that could determine biological outcome, not much is understood about how AR contributes to shaping biological outcome. By using a mesoporous silica nanoparticle (MSNP) library that has been constructed to cover a range of different lengths, we could demonstrate that the AR of rod-shaped particles determines the rate and abundance of MSNP uptake by a macropinocytosis process in HeLa and A549 cancer cell lines. MSNPs with an AR of 2.1-2.5 were taken up in larger quantities compared to shorter or longer length rods by a process that is sensitive to amiloride, cytochalasin D, azide, and 4 °C inhibition. The rods with intermediary AR also induced the maximal number of filopodia, actin polymerization, and activation of small GTP-binding proteins (e.g., Rac1, CDC42) that involve assembly of the actin cytoskeleton and filopodia formation. When assessing the role of AR in the delivery of paclitaxel or camptothecin, the rods with AR 2.1-2.5 were clearly more efficient for drug delivery and generation of cytotoxic killing in HeLa cells. All considered, our data suggest an active sensoring mechanism by which HeLa and A549 cells are capable of detecting AR differences in MSNP to the extent that accelerated macropinocytosis can be used to achieve more efficient drug delivery.
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Affiliation(s)
- Huan Meng
- Division of NanoMedicine, Department of Medicine, University of California, Los Angeles, CA 90095
| | - Sui Yang
- Department of Chemistry & Biochemistry, University of California, Los Angeles, CA 90095
| | - Zongxi Li
- Department of Chemistry & Biochemistry, University of California, Los Angeles, CA 90095
| | - Tian Xia
- Division of NanoMedicine, Department of Medicine, University of California, Los Angeles, CA 90095
| | - Justin Chen
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA 90095
| | - Zhaoxia Ji
- California NanoSystems Institute, University of California, Los Angeles, CA 90095
| | - Haiyuan Zhang
- Division of NanoMedicine, Department of Medicine, University of California, Los Angeles, CA 90095
| | - Xiang Wang
- Division of NanoMedicine, Department of Medicine, University of California, Los Angeles, CA 90095
| | - Sijie Lin
- Division of NanoMedicine, Department of Medicine, University of California, Los Angeles, CA 90095
| | - Connie Huang
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA 90095
| | - Z. Hong Zhou
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA 90095
- California NanoSystems Institute, University of California, Los Angeles, CA 90095
| | - Jeffrey I. Zink
- Department of Chemistry & Biochemistry, University of California, Los Angeles, CA 90095
- California NanoSystems Institute, University of California, Los Angeles, CA 90095
| | - Andre E. Nel
- Division of NanoMedicine, Department of Medicine, University of California, Los Angeles, CA 90095
- California NanoSystems Institute, University of California, Los Angeles, CA 90095
- Corresponding Author: Andre E. Nel, M.D., Department of Medicine, Division of NanoMedicine, UCLA School of Medicine, 52-175 CHS, 10833 Le Conte Ave, Los Angeles, CA 90095-1680. Tel: (310) 825-6620, Fax: (310) 206-8107,
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87
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Late-penetrating viruses. Curr Opin Virol 2011; 1:35-43. [PMID: 22440565 DOI: 10.1016/j.coviro.2011.05.004] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Revised: 05/11/2011] [Accepted: 05/12/2011] [Indexed: 01/08/2023]
Abstract
Many enveloped and non-enveloped animal viruses delay the penetration into the cytosol of host cells until they have arrived to endocytic vacuoles deep in the cytoplasm. The late timing is generally determined by a low pH-threshold for the acid-activated penetration process (pH 6.2-4.9), but there can be a combination of other reasons for a delay. Since late-penetrating viruses (L-PVs) must be sorted into the degradative pathway, they are particularly sensitive to perturbations that interfere with molecular sorting and proper maturation of endosomes, including switching of Rabs, formation of intraluminal vesicles, and microtubule-mediated transport. In this short review, we focus on L-PVs from several virus families, and their interactions with the endocytic machinery.
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88
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Gerlier D. Emerging zoonotic viruses: new lessons on receptor and entry mechanisms. Curr Opin Virol 2011; 1:27-34. [PMID: 22440564 PMCID: PMC7102697 DOI: 10.1016/j.coviro.2011.05.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2011] [Revised: 05/20/2011] [Accepted: 05/24/2011] [Indexed: 11/27/2022]
Abstract
Viruses enter the host cell by binding cellular receptors that allow appropriate delivery of the viral genome. Although the horizontal propagation of viruses feeds the continuous emergence of novel pathogenic viruses, the genetic variation of cellular receptors can represent a challenging barrier. The SARS coronavirus, henipaviruses and filoviruses are zoonotic RNA viruses that use bats as their reservoir. Their lethality for man has fostered extensive research both on the cellular receptors they use and their entry pathways. These studies have allowed new insights into the diversity of the molecular mechanisms underlying both virus entry and pathogenesis.
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Affiliation(s)
- Denis Gerlier
- Human Virology, INSERM, U758, Ecole Normale Supérieure de Lyon, Lyon, F-69007, France.
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89
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Henaff D, Salinas S, Kremer EJ. An adenovirus traffic update: from receptor engagement to the nuclear pore. Future Microbiol 2011; 6:179-92. [PMID: 21366418 DOI: 10.2217/fmb.10.162] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Adenoviruses have a bipolar nature: they are ubiquitous pathogens that occasionally cause life-threatening diseases or they can be engineered into powerful gene transfer vectors. The goal of this article is to summarize the most recent advances in adenovirus receptor engagement, internalization, endosomal maturation, endosomal escape and trafficking to the nuclear pore. A better understanding of this initial part of the adenovirus lifecycle may identify new mechanistic-based treatments for adenovirus-induced diseases and help in the engineering of more efficient vectors.
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Affiliation(s)
- Daniel Henaff
- Institut de Génétique Moléculaire de Montpellier, CNRS UMR 5535, 34293 Montpellier, France
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90
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Multimerization of adenovirus serotype 3 fiber knob domains is required for efficient binding of virus to desmoglein 2 and subsequent opening of epithelial junctions. J Virol 2011; 85:6390-402. [PMID: 21525338 DOI: 10.1128/jvi.00514-11] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Recently, we identified desmoglein 2 (DSG2) as the main receptor for a group of species B adenoviruses (Ads), including Ad3, a serotype that is widely distributed in the human population (H. Wang et al., Nat. Med. 17:96-104, 2011). In this study, we have attempted to delineate structural details of the Ad3 interaction with DSG2. For CAR- and CD46-interacting Ad serotypes, attachment to cells can be completely blocked by an excess of recombinant fiber knob protein, while soluble Ad3 fiber knob only inefficiently blocks Ad3 infection. We found that the DSG2-interacting domain(s) within Ad3 is formed by several fiber knob domains that have to be in the spatial constellation that is present in viral particles. Based on this finding, we generated a small recombinant, self-dimerizing protein containing the Ad3 fiber knob (Ad3-K/S/Kn). Ad3-K/S/Kn bound to DSG2 with high affinity and blocked Ad3 infection. We demonstrated by confocal immunofluorescence and transmission electron microscopy analyses that Ad3-K/S/Kn, through its binding to DSG2, triggered the transient opening of intercellular junctions in epithelial cells. The pretreatment of epithelial cells with Ad3-K/S/Kn resulted in increased access to receptors that are localized in or masked by epithelial junctions, e.g., CAR or Her2/neu. Ad3-K/S/Kn treatment released CAR from tight junctions and thus increased the transduction of epithelial cells by a serotype Ad5-based vector. Furthermore, the pretreatment of Her2/neu-positive breast cancer cells with Ad3-K/S/Kn increased the killing of cancer cells by the Her2/neu-targeting monoclonal antibody trastuzumab (Herceptin). This study widens our understanding of how Ads achieve high avidity to their receptors and the infection of epithelial tissue. The small recombinant protein Ad3-K/S/Kn has practical implications for the therapy of epithelial cancer and gene/drug delivery to normal epithelial tissues.
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91
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Khan AG, Pickl-Herk A, Gajdzik L, Marlovits TC, Fuchs R, Blaas D. Entry of a heparan sulphate-binding HRV8 variant strictly depends on dynamin but not on clathrin, caveolin, and flotillin. Virology 2011; 412:55-67. [DOI: 10.1016/j.virol.2010.12.042] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Revised: 10/22/2010] [Accepted: 12/22/2010] [Indexed: 02/08/2023]
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92
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Stepwise loss of fluorescent core protein V from human adenovirus during entry into cells. J Virol 2010; 85:481-96. [PMID: 21047958 DOI: 10.1128/jvi.01571-10] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Human adenoviruses (Ads) replicate and assemble particles in the nucleus. They organize a linear double-strand DNA genome into a condensed core with about 180 nucleosomes, by the viral proteins VII (pVII), pX, and pV attaching the DNA to the capsid. Using reverse genetics, we generated a novel, nonconditionally replicating Ad reporter by inserting green fluorescent protein (GFP) at the amino terminus of pV. Purified Ad2-GFP-pV virions had an oversized complete genome and incorporated about 38 GFP-pV molecules per virion, which is about 25% of the pV levels in Ad2. GFP-pV cofractionated with the DNA core, like pV, and newly synthesized GFP-pV had a subcellular localization indistinguishable from that of pV, indicating that GFP-pV is a valid reporter for pV. Ad2-GFP-pV completed the replication cycle, although at lower yields than Ad2. Incoming GFP-pV (or pV) was not imported into the nucleus. Virions lost GFP-pV at two points during the infection process: at entry into the cytosol and at the nuclear pore complex, where capsids disassemble. Disassembled capsids, positive for the conformation-specific antihexon antibody R70, were devoid of GFP-pV. The loss of GFP-pV was reduced by the macrolide antibiotic leptomycin B (LMB), which blocks nuclear export and adenovirus attachment to the nuclear pore complex. LMB inhibited the appearance of R70 epitopes on Ad2 and Ad2-GFP-pV, indicating that the loss of GFP-pV from Ad2-GFP-pV is an authentic step in the adenovirus uncoating program. Ad2-GFP-pV is genetically complete and hence enables detailed analyses of infection and spreading dynamics in cells and model organisms or assessment of oncolytic adenoviral potential.
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93
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Unity and diversity in the human adenoviruses: exploiting alternative entry pathways for gene therapy. Biochem J 2010; 431:321-36. [DOI: 10.1042/bj20100766] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Human Ads (adenoviruses) have been extensively utilized for the development of vectors for gene transfer, as they infect many cell types and do not integrate their genome into host-cell chromosomes. In addition, they have been widely studied as cytolytic viruses, termed oncolytic adenoviruses in cancer therapy. Ads are non-enveloped viruses with a linear double-stranded DNA genome of 30–38 kb which encodes 30–40 genes. At least 52 human Ad serotypes have been identified and classified into seven species, A–G. The Ad capsid has icosahedral symmetry and is composed of 252 capsomers, of which 240 are located on the facets of the capsid and consist of a trimeric hexon protein and the remaining 12 capsomers, the pentons, are at the vertices and comprise the penton base and projecting fibre protein. The entry of Ads into human cells is a two-step process. In the first step, the fibre protein mediates a primary interaction with the cell, effectively tethering the virus particle to the cell surface via a cellular attachment protein. The penton base then interacts with cell-surface integrins, leading to virus internalization. This interaction of the fibre protein with a number of cell-surface molecules appears to be important in determining the tropism of adenoviruses. Ads from all species, except species B and certain serotypes of species D, utilize CAR (coxsackie and adenovirus receptor) as their primary cellular-attachment protein, whereas most species B Ads use CD46, a complement regulatory protein. Such species-specific differences, as well as adaptations or modifications of Ads required for applications in gene therapy, form the major focus of the present review.
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94
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Jurgeit A, Moese S, Roulin P, Dorsch A, Lötzerich M, Lee WM, Greber UF. An RNA replication-center assay for high content image-based quantifications of human rhinovirus and coxsackievirus infections. Virol J 2010; 7:264. [PMID: 20937137 PMCID: PMC2958916 DOI: 10.1186/1743-422x-7-264] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Accepted: 10/11/2010] [Indexed: 01/17/2023] Open
Abstract
Background Picornaviruses are common human and animal pathogens, including polio and rhinoviruses of the enterovirus family, and hepatits A or food-and-mouth disease viruses. There are no effective countermeasures against the vast majority of picornaviruses, with the exception of polio and hepatitis A vaccines. Human rhinoviruses (HRV) are the most prevalent picornaviruses comprising more than one hundred serotypes. The existing and also emerging HRVs pose severe health risks for patients with asthma or chronic obstructive pulmonary disease. Here, we developed a serotype-independent infection assay using a commercially available mouse monoclonal antibody (mabJ2) detecting double-strand RNA. Results Immunocytochemical staining for RNA replication centers using mabJ2 identified cells that were infected with either HRV1A, 2, 14, 16, 37 or coxsackievirus (CV) B3, B4 or A21. MabJ2 labeled-cells were immunocytochemically positive for newly synthesized viral capsid proteins from HRV1A, 14, 16, 37 or CVB3, 4. We optimized the procedure for detection of virus replication in settings for high content screening with automated fluorescence microscopy and single cell analysis. Our data show that the infection signal was dependent on multiplicity, time and temperature of infection, and the mabJ2-positive cell numbers correlated with viral titres determined in single step growth curves. The mabJ2 infection assay was adapted to determine the efficacy of anti-viral compounds and small interfering RNAs (siRNAs) blocking enterovirus infections. Conclusions We report a broadly applicable, rapid protocol to measure infection of cultured cells with enteroviruses at single cell resolution. This assay can be applied to a wide range of plus-sense RNA viruses, and hence allows comparative studies of viral infection biology without dedicated reagents or procedures. This protocol also allows to directly compare results from small compound or siRNA infection screens for different serotypes without the risk of assay specific artifacts.
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Affiliation(s)
- Andreas Jurgeit
- Institute of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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95
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Saeed MF, Kolokoltsov AA, Albrecht T, Davey RA. Cellular entry of ebola virus involves uptake by a macropinocytosis-like mechanism and subsequent trafficking through early and late endosomes. PLoS Pathog 2010; 6:e1001110. [PMID: 20862315 PMCID: PMC2940741 DOI: 10.1371/journal.ppat.1001110] [Citation(s) in RCA: 334] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Accepted: 08/17/2010] [Indexed: 12/17/2022] Open
Abstract
Zaire ebolavirus (ZEBOV), a highly pathogenic zoonotic virus, poses serious public health, ecological and potential bioterrorism threats. Currently no specific therapy or vaccine is available. Virus entry is an attractive target for therapeutic intervention. However, current knowledge of the ZEBOV entry mechanism is limited. While it is known that ZEBOV enters cells through endocytosis, which of the cellular endocytic mechanisms used remains unclear. Previous studies have produced differing outcomes, indicating potential involvement of multiple routes but many of these studies were performed using noninfectious surrogate systems such as pseudotyped retroviral particles, which may not accurately recapitulate the entry characteristics of the morphologically distinct wild type virus. Here we used replication-competent infectious ZEBOV as well as morphologically similar virus-like particles in specific infection and entry assays to demonstrate that in HEK293T and Vero cells internalization of ZEBOV is independent of clathrin, caveolae, and dynamin. Instead the uptake mechanism has features of macropinocytosis. The binding of virus to cells appears to directly stimulate fluid phase uptake as well as localized actin polymerization. Inhibition of key regulators of macropinocytosis including Pak1 and CtBP/BARS as well as treatment with the drug EIPA, which affects macropinosome formation, resulted in significant reduction in ZEBOV entry and infection. It is also shown that following internalization, the virus enters the endolysosomal pathway and is trafficked through early and late endosomes, but the exact site of membrane fusion and nucleocapsid penetration in the cytoplasm remains unclear. This study identifies the route for ZEBOV entry and identifies the key cellular factors required for the uptake of this filamentous virus. The findings greatly expand our understanding of the ZEBOV entry mechanism that can be applied to development of new therapeutics as well as provide potential insight into the trafficking and entry mechanism of other filoviruses. Filoviruses, including Zaire ebolavirus (ZEBOV), are among the most pathogenic viruses known. Our understanding of how these viruses enter into host cells is very limited. A deeper understanding of this process would enable the design of better targeted antiviral therapies. This study defines in detail, key steps of ZEBOV cellular uptake and trafficking into cells using wild type virus as well as the host factors that are responsible for permitting virus entry into cells. Our data indicated that the primary mechanism of ZEBOV uptake is a macropinocytosis-like process that delivers the virus to early endosomes and subsequently to late endosomes. These findings aid in our understanding of how filoviruses infect cells and suggest that disruption of macropinocytosis may be useful in treatment of infection.
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Affiliation(s)
- Mohammad F. Saeed
- Department of Microbiology & Immunology, The University of Texas Medical Branch, Galveston, Texas, United States of America
- Galveston National Laboratory, The University of Texas Medical Branch, Galveston, Texas, United States of America
- Institute of Human Infection and Immunity, The University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Andrey A. Kolokoltsov
- Department of Microbiology & Immunology, The University of Texas Medical Branch, Galveston, Texas, United States of America
- Galveston National Laboratory, The University of Texas Medical Branch, Galveston, Texas, United States of America
- Institute of Human Infection and Immunity, The University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Thomas Albrecht
- Department SK, Building 37, NASA, Houston, Texas, United States of America
| | - Robert A. Davey
- Department of Microbiology & Immunology, The University of Texas Medical Branch, Galveston, Texas, United States of America
- Galveston National Laboratory, The University of Texas Medical Branch, Galveston, Texas, United States of America
- Institute of Human Infection and Immunity, The University of Texas Medical Branch, Galveston, Texas, United States of America
- * E-mail:
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