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Lichtenstein DL, Doronin K, Toth K, Kuppuswamy M, Wold WSM, Tollefson AE. Adenovirus E3-6.7K protein is required in conjunction with the E3-RID protein complex for the internalization and degradation of TRAIL receptor 2. J Virol 2004; 78:12297-307. [PMID: 15507617 PMCID: PMC525093 DOI: 10.1128/jvi.78.22.12297-12307.2004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2004] [Accepted: 06/23/2004] [Indexed: 11/20/2022] Open
Abstract
Adenoviruses (Ads) encode several proteins within the early region 3 (E3) transcription unit that help protect infected cells from elimination by the immune system. Among these immunomodulatory proteins, the receptor internalization and degradation (RID) protein complex, which is composed of the RIDalpha (formerly E3-10.4K) and RIDbeta (formerly E3-14.5K) subunits, stimulates the internalization and degradation of certain members of the tumor necrosis factor (TNF) receptor superfamily, thus blocking apoptosis initiated by Fas and TNF-related apoptosis-inducing ligand (TRAIL). The experiments reported here show that TRAIL receptor 2 (TR2) is cleared from the cell surface in Ad-infected cells. Virus mutants containing deletions that span E3 were used to show that the RID and E3-6.7K proteins are both necessary for the internalization and degradation of TR2, whereas only the RID protein is required for TRAIL receptor 1 downregulation. In addition, replication-defective Ad vectors that express individual E3 proteins were used to establish that the RID and E3-6.7K proteins are sufficient to clear TR2. These data demonstrate that E3-6.7K is an important component of the antiapoptosis arsenal encoded by the E3 transcription unit of subgroup C Ads.
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Affiliation(s)
- Drew L Lichtenstein
- Department of Molecular Microbiology and Immunology, School of Medicine, Saint Louis University, 1402 South Grand Blvd., St. Louis, MO 63104, USA
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Fessler SP, Delgado-Lopez F, Horwitz MS. Mechanisms of E3 Modulation of Immune and Inflammatory Responses. Curr Top Microbiol Immunol 2004; 273:113-35. [PMID: 14674600 DOI: 10.1007/978-3-662-05599-1_4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023]
Abstract
Adenoviruses contain genes that have evolved to control the host immune and inflammatory responses; however, it is not clear whether these genes function primarily to facilitate survival of the virus during acute infection or during its persistent phase. These issues have assumed greater importance as the use of adenoviruses as vectors for gene therapy has been expanded. This review will focus on the mechanism of immune evasion mediated by the proteins encoded within the early region 3 (E3) transcription region, which affect the functions of a number of cell surface receptors including Fas, intracellular cell signaling events involving NF-kappaB, and the secretion of pro-inflammatory molecules such as chemokines. The successful use of E3 genes in facilitating allogeneic transplantation and in preventing autoimmune diabetes in several transgenic mouse models will also be described.
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Affiliation(s)
- S P Fessler
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, New York, NY 10461, USA
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3
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Zanardi TA, Yei S, Lichtenstein DL, Tollefson AE, Wold WSM. Distinct domains in the adenovirus E3 RIDalpha protein are required for degradation of Fas and the epidermal growth factor receptor. J Virol 2003; 77:11685-96. [PMID: 14557654 PMCID: PMC229367 DOI: 10.1128/jvi.77.21.11685-11696.2003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Adenovirus (Ad) types 2 and 5 encode at least five proteins within the E3 transcription unit that help the virus evade the immune system. Two such proteins, RIDalpha (formerly E3-10.4K) and RIDbeta (formerly E3-14.5K), form the RID (receptor internalization and degradation) complex (formerly E3-10.4K/14.5K). RID mediates clearance from the cell surface and lysosomal degradation of a number of important members in the tumor necrosis factor receptor (TNFR) superfamily and the receptor tyrosine kinase receptor family. Affected receptors include Fas, TRAIL (TNF-related apoptosis-inducing ligand) receptor 1 (TR1), TR2, and epidermal growth factor receptor (EGFR). Degradation of Fas and TRAIL receptors protects Ad-infected cells from apoptosis. To investigate the mechanism of action of RIDalpha, 14 mutant RIDalpha proteins, each containing a three- to five-amino-acid deletion, were constructed and then expressed from the E3 region of a replication-competent recombinant Ad in the same context as wild-type RIDalpha. Each mutant protein was characterized with regard to five physical properties associated with wild-type RIDalpha, namely, protein stability, proteolytic cleavage, insertion into the membrane, complex formation with RIDbeta, and transport to the cell surface. Additionally, the mutant proteins were tested for their ability to mediate internalization and degradation of EGFR and Fas and to protect cells from Fas-mediated apoptosis. The majority of mutant RIDalpha proteins (8 out of 14) were physically similar to wild-type RIDalpha. With regard to functional characteristics, the cytoplasmic domain of RIDalpha is largely unimportant for receptor internalization and degradation and the extracellular domain of RIDalpha is important for down-regulation of EGFR but not Fas.
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Affiliation(s)
- Tom A Zanardi
- Department of Molecular Microbiology and Immunology, Saint Louis University Health Sciences Center, St. Louis, Missouri 63104, USA
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4
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Lichtenstein DL, Krajcsi P, Esteban DJ, Tollefson AE, Wold WSM. Adenovirus RIDbeta subunit contains a tyrosine residue that is critical for RID-mediated receptor internalization and inhibition of Fas- and TRAIL-induced apoptosis. J Virol 2002; 76:11329-42. [PMID: 12388693 PMCID: PMC136796 DOI: 10.1128/jvi.76.22.11329-11342.2002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The adenovirus-encoded receptor internalization and degradation (RID) protein (previously named E3-10.4K/14.5K), which is composed of RIDalpha and RIDbeta subunits, down-regulates a number of cell surface receptors in the tumor necrosis factor (TNF) receptor superfamily, namely Fas, TRAIL receptor 1, and TRAIL receptor 2. Down-regulation of these "death" receptors protects adenovirus-infected cells from apoptosis induced by the death receptor ligands Fas ligand and TRAIL. RID also down-regulates certain tyrosine kinase cell surface receptors, especially the epidermal growth factor receptor (EGFR). RID-mediated Fas and EGFR down-regulation occurs via endocytosis of the receptors into endosomes followed by transport to and degradation within lysosomes. However, the molecular interactions underlying this function of RID are unknown. To investigate the molecular determinants of RIDbeta that are involved in receptor down-regulation, mutations within the cytoplasmic tail of RIDbeta were constructed and the mutant proteins were analyzed for their capacity to internalize and degrade Fas and EGFR and to protect cells from death receptor ligand-induced apoptosis. The results demonstrated the critical nature of a tyrosine residue near the RIDbeta C terminus; mutation of this residue to alanine abolished RID function. Mutating the tyrosine to phenylalanine did not abolish the function of RID, arguing that phosphorylation of the tyrosine is not required for function. These data suggest that this tyrosine residue forms part of a tyrosine-based sorting signal (Yxxphi). Additional mutations that target another potential sorting motif and several possible protein-protein interaction motifs had no discernible effect on RID function. It was also demonstrated that mutation of serine 116 to alanine eliminated phosphorylation of RIDbeta but did not affect any of the functions of RID that were examined. These results suggest a model in which the tyrosine-based sorting signal in RID plays a role in RID's ability to down-regulate receptors.
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Affiliation(s)
- Drew L Lichtenstein
- Department of Molecular Microbiology and Immunology, Saint Louis University Health Sciences Center, St. Louis, Missouri 63104, USA
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Toth K, Kuppuswamy M, Doronin K, Doronina O, Lichtenstein D, Tollefson A, Wold W. Construction and characterization of E1-minus replication-defective adenovirus vectors that express E3 proteins from the E1 region. Virology 2002; 301:99-108. [PMID: 12359450 DOI: 10.1006/viro.2002.1580] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previous research has indicated that the adenovirus protein complex named RID, derived from the E3 transcription unit, functions to remove the receptors named Fas/Apo1/CD95 (Fas) and epidermal growth factor receptor (EGFR) from the surface of cells. (The RID complex is composed of the RIDalpha and RIDbeta polypeptides, previously named 10.4K and 14.5K, respectively.) In response to RID, Fas and EGFR appear to be internalized into endosomes and degraded in lysosomes. Fas is a death receptor in the tumor necrosis factor (TNF) receptor superfamily. RID inhibits apoptosis via the Fas pathway, presumably because RID gets rid of Fas. Earlier work further showed that another adenovirus E3-coded protein, E3-14.7K, inhibits apoptosis induced by TNF. Most of the above studies have been conducted using viable virus mutants that lack one or more of the genes for RID, E3-14.7K, or E1B-19K (this protein, coded by the E1B transcription unit, also inhibits apoptosis via the TNF and Fas pathways). Some studies have also been conducted with the genes for RID or E3-14.7K transiently or stably transfected into cells. We now report a new approach to studying the E3 genes. We have constructed four E1-minus replication-defective vectors that have all the E3 genes deleted from their natural position and then reinserted, in different permutations, into the deleted E1 region under control of the cytomegalovirus immediate early promoter. Vector Ad/RID only has the genes for RIDalpha and RIDbeta. Vector Ad/14.7K only has the gene for E3-14.7K. Vector Ad/RID/14.7K only has the genes for RIDalpha, RIDbeta, and E3-14.7K. Vector Ad/E3 has all E3 genes, but there are two missense mutations in the gene for Adenovirus Death Protein. These vectors expressed RID and/or E3-14.7K, as expected. The RID-expressing vectors forced the internalization and degradation of Fas and EGFR, and they inhibited apoptosis induced through the Fas pathway. These vectors should be useful reagents to study the E3 proteins.
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Affiliation(s)
- Karoly Toth
- Department of Molecular Microbiology and Immunology, Saint Louis Unversity School of Medicine, Saint Louis, Missouri 63104, USA
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Benedict CA, Norris PS, Prigozy TI, Bodmer JL, Mahr JA, Garnett CT, Martinon F, Tschopp J, Gooding LR, Ware CF. Three adenovirus E3 proteins cooperate to evade apoptosis by tumor necrosis factor-related apoptosis-inducing ligand receptor-1 and -2. J Biol Chem 2001; 276:3270-8. [PMID: 11050095 DOI: 10.1074/jbc.m008218200] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Adenovirus encodes multiple gene products that regulate proapoptotic cellular responses to viral infection mediated by both the innate and adaptive immune systems. The E3-10.4K and 14.5K gene products are known to modulate the death receptor Fas. In this study, we demonstrate that an additional viral E3 protein, 6.7K, functions in the specific modulation of the two death receptors for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). The 6.7K protein is expressed on the cell surface and forms a complex with the 10.4K and 14.5K proteins, and this complex is sufficient to induce down-modulation of TRAIL receptor-1 and -2 from the cell surface and reverse the sensitivity of infected cells to TRAIL-mediated apoptosis. Down-modulation of TRAIL-R2 by the E3 complex is dependent on the cytoplasmic tail of the receptor, but the death domain alone is not sufficient. These results identify a mechanism for viral modulation of TRAIL receptor-mediated apoptosis and suggest the E3 protein complex has evolved to regulate the signaling of selected cytokine receptors.
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Affiliation(s)
- C A Benedict
- Division of Molecular Immunology and the Division of Developmental Immunology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121, USA
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7
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Crooks D, Kil SJ, McCaffery JM, Carlin C. E3-13.7 integral membrane proteins encoded by human adenoviruses alter epidermal growth factor receptor trafficking by interacting directly with receptors in early endosomes. Mol Biol Cell 2000; 11:3559-72. [PMID: 11029055 PMCID: PMC15013 DOI: 10.1091/mbc.11.10.3559] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Animal cell viruses provide valuable model systems for studying many normal cellular processes, including membrane protein sorting. The focus of this study is an integral membrane protein encoded by the E3 transcription region of human adenoviruses called E3-13.7, which diverts recycling EGF receptors to lysosomes without increasing the rate of receptor internalization or intrinsic receptor tyrosine kinase activity. Although E3-13.7 can be found on the plasma membrane when it is overexpressed, its effect on EGF receptor trafficking suggests that the plasma membrane is not its primary site of action. Using cell fractionation and immunocytochemical experimental approaches, we now report that the viral protein is located predominantly in early endosomes and limiting membranes of endosome-to-lysosome transport intermediates called multivesicular endosomes. We also demonstrate that E3-13.7 physically associates with EGF receptors undergoing E3-13.7-mediated down-regulation in early endosomes. Receptor-viral protein complexes then dissociate, and EGF receptors proceed to lysosomes, where they are degraded, while E3-13.7 is retained in endosomes. We conclude that E3-13.7 is a resident early endocytic protein independent of EGF receptor expression, because it has identical intracellular localization in mouse cells lacking endogenous receptors and cells expressing a human cytomegalovirus-driven receptor cDNA. Finally, we demonstrate that EGF receptor residues 675-697 are required for E3-13.7-mediated down-regulation. Interestingly, this sequence includes a known EGF receptor leucine-based lysosomal sorting signal used during ligand-induced trafficking, which is also conserved in the viral protein. E3-13.7, therefore, provides a novel model system for determining the molecular basis of selective membrane protein transport in the endocytic pathway. Our studies also suggest new paradigms for understanding EGF receptor sorting in endosomes and adenovirus pathogenesis.
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Affiliation(s)
- D Crooks
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
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Abstract
Adenovirus is a human pathogen that infects mainly respiratory and gastrointestinal epithelia. While the pathology caused by this virus is generally not life threatening in immunocompetent individuals, there is a large literature describing its ability to establish a persistent infection. These persistent infections typically occur in apparently healthy individuals with no outward signs of disease. Such a long term and benign interaction between virus and immune system requires adenoviruses to dampen host antiviral effector mechanisms that would otherwise eliminate the virus and cause immune-mediated pathology to the host. Adenovirus devotes a significant portion of its genome to gene products whose sole function seems to be the modulation of host immune responses. This review focuses on what is currently understood about how these immunomodulatory mechanisms work and how they might play a role in maintaining the virus in a persistent state.
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Affiliation(s)
- J A Mahr
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
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9
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Harrod KS, Hermiston TW, Trapnell BC, Wold WS, Whitsett JA. Lung-specific expression of adenovirus E3-14.7K in transgenic mice attenuates adenoviral vector-mediated lung inflammation and enhances transgene expression. Hum Gene Ther 1998; 9:1885-98. [PMID: 9741427 DOI: 10.1089/hum.1998.9.13-1885] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Herein, we report that the adenovirus E3-14.7K protein inhibits the inflammatory response to adenovirus in transgenic mice in which the E3-14.7K gene was selectively expressed in the respiratory epithelium, using the human surfactant protein C (SP-C) promoter. E3-14.7K mRNA and protein were detected specifically in the lungs of SPC/E3-14.7K transgenic mice. Responses of the transgenic mice to Av1Luc1, an E1-E3-deleted Ad vector encoding the luciferase reporter gene, were examined, including vector transgene expression and lung inflammation. In wild-type mice, luciferase activity declined rapidly and was lost 14 days following Av1Luc1 administration. The loss of luciferase activity was associated with pulmonary infiltration by macrophages and lymphocytes. In heterozygous SPC/E3-14.7K mice, luciferase activity was increased by 7 days compared with control littermates, and pulmonary infiltration by macrophages was decreased. In homozygous (+/+) SPC/E3-14.7K mice, luciferase activity was increased 7, 14, and 21 days following administration compared with wild-type mice, and lung inflammation was markedly reduced. After Av1Luc1 administration, PCNA staining of bronchiolar and alveolar respiratory epithelial cells was decreased in SPC/E3-14.7K transgenic mice, indicating decreased epithelial cell proliferation, a finding consistent with the observed reduction in inflammation. CD4 and CD8 lymphocyte populations were only mildly altered, while humoral responses to adenoviral vectors were unchanged in the SPC/E3-14.7K mice. The E3-14.7K protein expressed selectively in respiratory epithelial cells suppresses Ad-induced pulmonary epithelial cell cytotoxicity and lung inflammation in vivo and prolongs reporter gene expression.
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Affiliation(s)
- K S Harrod
- Division of Pulmonary Biology, Children's Hospital Medical Center, Cincinnati, OH 45229, USA
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10
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Adenovirus E3 Proteins: 14.7K, RID, and gp19K Inhibit Immune-Induced Cell Death; Adenovirus Death Protein Promotes Cell Death. ACTA ACUST UNITED AC 1998. [DOI: 10.1006/smvy.1998.0156] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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11
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Shisler J, Yang C, Walter B, Ware CF, Gooding LR. The adenovirus E3-10.4K/14.5K complex mediates loss of cell surface Fas (CD95) and resistance to Fas-induced apoptosis. J Virol 1997; 71:8299-306. [PMID: 9343182 PMCID: PMC192288 DOI: 10.1128/jvi.71.11.8299-8306.1997] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Cytotoxic T cells use Fas (CD95), a member of the tumor necrosis factor (TNF) receptor superfamily, to eliminate virus-infected cells by activation of the apoptotic pathway for cell death. The adenovirus E3 region encodes several proteins that modify immune defenses, including TNF-dependent cell death, which may allow this virus to establish a persistent infection. Here we show that, as an early event during infection, the adenovirus E3-10.4K/14.5K complex selectively induces loss of Fas surface expression and blocks Fas-induced apoptosis of virus-infected cells. Loss of surface Fas occurs within the first 4 h postinfection and is not due to decreased production of Fas protein. The decrease in surface Fas is distinct from the 10.4K/14.5K-mediated loss of the epidermal growth factor receptor on the same cells, because intracellular stores of Fas are not affected. Further, 10.4K/14.5K, which was previously shown to protect against TNF cytolysis, does not induce a loss of TNF receptor, indicating that this complex mediates more than one function to block host defense mechanisms. These results suggest yet another mechanism by which adenovirus modulates host cytotoxic responses that may contribute to persistent infection by human adenoviruses.
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Affiliation(s)
- J Shisler
- Department of Microbiology, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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12
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Dimitrov T, Krajcsi P, Hermiston TW, Tollefson AE, Hannink M, Wold WS. Adenovirus E3-10.4K/14.5K protein complex inhibits tumor necrosis factor-induced translocation of cytosolic phospholipase A2 to membranes. J Virol 1997; 71:2830-7. [PMID: 9060638 PMCID: PMC191407 DOI: 10.1128/jvi.71.4.2830-2837.1997] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
We have reported that three adenovirus (Ad) proteins, named E3-10.4K/14.5K, E3-14.7K, and E1B-19K, independently inhibit tumor necrosis factor (TNF)-induced apoptosis in Ad-infected cells. E3-10.4K/14.5K and E3-14.7K also inhibit TNF-induced release of arachidonic acid (AA). TNF-induced apoptosis and AA release are thought to require TNF-activation of the 85-kDa cytosolic phospholipase A2 (cPLA2). cPLA2 normally exists in a latent form in the cytosol; it is activated by phosphorylation by mitogen-activated protein kinase, and in the presence of agents that mobilize intracellular Ca2+, cPLA2 translocates to membranes where it cleaves AA from membrane phospholipids. We now report that TNF induces translocation of cPLA2 from the cytosol to membranes in Ad-infected human A549 cells and that E3-10.4K/14.5K but not E3-14.7K or E1B-19K is required to inhibit TNF-induced translocation of cPLA2. Ad infection also inhibited TNF-induced release of AA. Under the same conditions, Ad infection did not inhibit TNF-induced phosphorylation of cPLA2 or TNF activation of NFkappaB. Ad infection also inhibited cPLA2 translocation in response to the Ca2+ ionophore A23187 and to cycloheximide, but this inhibition did not require E3-10.4K/14.5K. Ad infection did not inhibit cPLA2 translocation in response to interleukin-1beta or platelet-derived growth factor. We propose that E3-10.4K/14.5K inhibits TNF-induced AA release and apoptosis by directly or indirectly inhibiting TNF-induced translocation of cPLA2 from the cytosol to membranes. AA formed by cPLA2 can be metabolized to prostaglandins, leukotrienes, and lipoxyns, molecules that amplify inflammation. E3-10.4K/14.5K probably functions in Ad infections to inhibit both TNF-induced apoptosis and inflammation.
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Affiliation(s)
- T Dimitrov
- Department of Molecular Microbiology and Immunology, St. Louis University School of Medicine, Missouri 63104, USA
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13
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Krajcsi P, Dimitrov T, Hermiston TW, Tollefson AE, Ranheim TS, Vande Pol SB, Stephenson AH, Wold WS. The adenovirus E3-14.7K protein and the E3-10.4K/14.5K complex of proteins, which independently inhibit tumor necrosis factor (TNF)-induced apoptosis, also independently inhibit TNF-induced release of arachidonic acid. J Virol 1996; 70:4904-13. [PMID: 8763993 PMCID: PMC190440 DOI: 10.1128/jvi.70.8.4904-4913.1996] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Tumor necrosis factor (TNF) is an inflammatory cytokine that inhibits the replication of many viruses in cultured cells. We have reported that adenovirus (Ad) infection of TNF-resistant mouse cells renders them susceptible to lysis by TNF and that two sets of proteins encoded by the E3 transcription unit block TNF cytolysis. The E3 protein sets are named E3-14.7K (14,700 kDa) and E3-10.4K/14.5K (a complex of two proteins of 10,400 and 14,500 kDa). TNF activation of the 85-kDa cytosolic phospholipase A2 (cPLA2) is thought to be essential for TNF cytolysis (i.e.,TNF-induced apoptosis). Here we provide evidence that cPLA2 is important in the response of Ad-infected cells to TNF and that the mechanism by which E3-14.7K and E3-10.4K/14.5K inhibit TNF cytolysis is by inhibiting TNF activation of cPLA2. cPLA2 cleaves arachidonic acid (AA) specifically from membrane phospholipids; therefore, cPLA2 activity was measured by the release of 3H-AA from cells prelabeled with 3H-AA. Uninfected cells or cells infected with wild-type Ad were not lysed and did not release 3H-AA in response to TNF. In contrast, TNF treatment induced cytolysis and 3H-AA release in uninfected cells sensitized to TNF by treatment with cycloheximide and also in infected cells sensitized to TNF by expression of E1A. In C127 cells, in which either E3-14.7K or E3-10.4K/14.5K inhibits TNF cytolysis, either set of proteins inhibited TNF-induced release of 3H-AA. In C3HA cells, in which E3-14.7K but not E3-10.4K/14.5K prevents TNF cytolysis, E3-14.7K but not E3-10.4K/14.5K prevented TNF-induced release of 3H-AA. When five virus mutants with lesions in E3-14.7K were examined, there was a perfect correlation between a mutant's ability to inhibit both TNF-induced cytolysis and release of 3H-AA. E3-14.7K expressed in two stably transfected C127 cell lines prevented both TNF-cycloheximide-induced cytolysis and release of 3H-AA. The E3 proteins also prevented TNF-induced cytolysis and release of 3H-AA in mouse L929 cells, which are spontaneously sensitive to TNF. TNF cytolysis was blocked by dexamethasone, an inhibitor of PLA2 activity, and by nordihydroquaiaretic acid, which inhibits the metabolism of AA to the leukotrienes. Indomethacin, which blocks the formation of prostaglandins from AA, did not inhibit TNF cytolysis. The leukotrienes and prostaglandins are amplifiers of the inflammatory response. We propose that E3-14.7K and E3-10.4K/14.5K function independently in Ad infection to inhibit both cytolysis and inflammation induced by TNF.
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Affiliation(s)
- P Krajcsi
- Department of Molecular Microbiology and Immunology, St. Louis University Schoolof Medicine, Missouri 63104, USA
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14
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Sparer TE, Tripp RA, Dillehay DL, Hermiston TW, Wold WS, Gooding LR. The role of human adenovirus early region 3 proteins (gp19K, 10.4K, 14.5K, and 14.7K) in a murine pneumonia model. J Virol 1996; 70:2431-9. [PMID: 8642671 PMCID: PMC190086 DOI: 10.1128/jvi.70.4.2431-2439.1996] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Products of human adenovirus (Ad) early region 3 (E3) inhibit both specific (cytotoxic T lymphocytes [CTLs]) and innate (tumor necrosis factor alpha [TNF-alpha]) immune responses in vitro. The E3 gp19K protein prevents CTL recognition of Ad-infected fibroblasts by sequestering major histocompatibility complex class I proteins in the endoplasmic reticulum. E3 proteins 10.4K, 14.5K, and 14.7K function to protect infected cells from TNF-alpha cytolysis. To address the in vivo functions of these proteins, Ad mutants that lack the E3 genes encoding these proteins were inoculated intranasally into C57BL/10SnJ (H-2b) mice. Mutants that lack the gp19K gene failed to alter CTL generation or to affect Ad-induced pulmonary infiltrates. Since gamma interferon (IFN-gamma) is capable of overcoming gp19K suppression of CTL lysis in vitro, mice were depleted of IFN-gamma and inoculated with gp19K mutants. Even when IFN-gamma was depleted, gp19K was incapable of altering pulmonary lesions. These resuls are not in accord with the function of gp19K in vitro and suggest that gp19K does not affect immune recognition in vivo during an acute virus infection, yet they do not exclude the possibility that gp19K blocks immune recognition of Ad during a persistent infection. In contrast, when mice were inoculated with Ad mutants that lack the TNF resistance genes (14.7K and either 10.4K or 14.5K), there was a marked increase in alveolar infiltration and no change in the amounts of perivascular/peribronchiolar infiltration compared with wild-type-Ad-induced pathology. These findings demonstrate the importance of TNF susceptibility and TNF by-products for recruiting inflammatory cells into the lungs during Ad infections.
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Affiliation(s)
- T E Sparer
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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15
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Hawkins LK, Wilson-Rawls J, Wold WS. Region E3 of subgroup B human adenoviruses encodes a 16-kilodalton membrane protein that may be a distant analog of the E3-6.7K protein of subgroup C adenoviruses. J Virol 1995; 69:4292-8. [PMID: 7769690 PMCID: PMC189168 DOI: 10.1128/jvi.69.7.4292-4298.1995] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
There is an open reading frame in the E3 transcription unit of adenovirus type 3 (Ad3) and Ad7 that could encode a protein of 16 kDa (16K protein). Ad3 and Ad7 are members of subgroup B of human adenoviruses. Using a rabbit antipeptide antiserum, we show that the 16K protein is expressed in Ad3- and Ad7-infected cells at early and late stages of infection; it is not expressed in cells infected with an Ad7 mutant that deletes the 16K gene. The 16K protein was also transcribed and translated in vitro from DNA containing the open reading frame for the 16K protein. The 16K protein has two hydrophobic domains typical of integral membrane proteins; consistent with this, we detected 16K in the crude membrane but not the cytosol cellular fractions. Although 16K has two potential sites for Asn-linked glycosylation, the protein is not glycosylated. The 16K gene is located in the same position in region E3 as the gene for the 6.7K protein of subgroup C adenoviruses (Ad2 and Ad5). E3-6.7K is an Asn-linked integral membrane glycoprotein, localized in the endoplasmic reticulum, whose function is unknown. The 16K protein has a putative transmembrane domain located in the same place in 16K as is the transmembrane domain in 6.7K, and the C-terminal portion of 16K is partially homologous to the C-terminal cytoplasmic domain of 6.7K; we suggest that these domains in 16K and 6.7K may have a similar function. The N-terminal 102 residues in 16K are not found in 6.7K; these residues may have a function that is unique to the 16K protein. In common with all known E3 proteins, the 16K protein is dispensable for virus replication in cultured cells; this suggests that the 16K protein may function in virus-host interactions.
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Affiliation(s)
- L K Hawkins
- Department of Molecular Microbiology and Immunology, St. Louis University Health Sciences Center, Missouri 63104, USA
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16
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Stewart AR, Tollefson AE, Krajcsi P, Yei SP, Wold WS. The adenovirus E3 10.4K and 14.5K proteins, which function to prevent cytolysis by tumor necrosis factor and to down-regulate the epidermal growth factor receptor, are localized in the plasma membrane. J Virol 1995; 69:172-81. [PMID: 7983708 PMCID: PMC188561 DOI: 10.1128/jvi.69.1.172-181.1995] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The adenovirus type 2 and 5 E3 10,400- and 14,500-molecular-weight (10.4K and 14.5K) proteins are both required to protect some cell lines from lysis by tumor necrosis factor and to down-regulate the epidermal growth factor receptor. We have shown previously that both 10.4K and 14.5K are integral membrane proteins and that 14.5K is phosphorylated and O glycosylated. The 10.4K protein coimmunoprecipitates with 14.5K, indicating that the two proteins function as a complex. Here we show, using immunofluorescence and two different cell surface-labeling techniques, that both proteins are localized in the plasma membrane. In addition, we show that trafficking of each protein to the plasma membrane depends on concomitant expression of the other protein. Finally, neither protein could be immunoprecipitated from conditioned media, indicating that neither is secreted. Taken together, these results suggest that the plasma membrane is the site at which 10.4K and 14.5K function to inhibit cytolysis by tumor necrosis factor and to down-regulate the epidermal growth factor receptor.
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Affiliation(s)
- A R Stewart
- Department of Molecular Microbiology and Immunology, St. Louis University School of Medicine, Missouri 63104
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17
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Affiliation(s)
- W S Wold
- Department of Molecular Microbiology and Immunology, St. Louis University School of Medicine, MO 63104, USA
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18
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Adenovirus E3 protein causes constitutively internalized epidermal growth factor receptors to accumulate in a prelysosomal compartment, resulting in enhanced degradation. Mol Cell Biol 1994. [PMID: 8196613 DOI: 10.1128/mcb.14.6.3695] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have previously identified and characterized an integral membrane protein coded for by the early transcription region 3 (E3) of human group C adenoviruses that down-regulates the epidermal growth factor receptor (EGFR). The goal of this study was to characterize the early receptor trafficking events leading to enhanced EGFR degradation in adenovirus-infected cells. Specifically, we wished to determine whether adenovirus increases the rate of EGFR internalization or alters the subcellular compartmentalization of internalized EGFRs. Once the optimal time for measuring early trafficking events was determined, surface EGFRs were labeled with a cleavable biotin reagent to measure internalization rates and with a receptor-specific monoclonal antibody (MAb) conjugated to colloidal gold for intracellular localization studies. We first showed that the rate of EGFR internalization in adenovirus-infected cells is indistinguishable from the constitutive internalization rate for unoccupied EGFRs. The possibility that the E3 protein can affect trafficking of EGFRs internalized at a low constitutive rate was further supported by studies showing that adenovirus-mediated down-regulation occurs independently of EGFR oligomerization and intrinsic EGFR tyrosine kinase activity, which are required for efficient ligand-induced internalization. Other tyrosine kinases inhibited by genistein are also not required for adenovirus-induced down-regulation. When the intracellular localization of EGFRs during adenovirus-mediated down-regulation was examined by electron microscopy, there was a threefold increase in the number of EGFRs localized to multivesicular bodies. The multivesicular body has been proposed to be important for regulating intracellular membrane protein sorting, since trafficking patterns for receptors that recycle and receptors that are degraded diverge in this organelle. These data therefore suggest that adenovirus may enhance EGFR degradation by causing constitutively internalized EGFRs to accumulate in a prelysosomal compartment. This is the first example of a mechanism that efficiently down-regulates EGFR without significantly increasing the rate of internalization or that does not require EGFR tyrosine kinase activity. Since viral proteins often mimic or modify a host counterpart, this suggests that there are normal physiological conditions when receptor destruction without tyrosine signalling is beneficial.
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19
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Hoffman P, Carlin C. Adenovirus E3 protein causes constitutively internalized epidermal growth factor receptors to accumulate in a prelysosomal compartment, resulting in enhanced degradation. Mol Cell Biol 1994; 14:3695-706. [PMID: 8196613 PMCID: PMC358737 DOI: 10.1128/mcb.14.6.3695-3706.1994] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
We have previously identified and characterized an integral membrane protein coded for by the early transcription region 3 (E3) of human group C adenoviruses that down-regulates the epidermal growth factor receptor (EGFR). The goal of this study was to characterize the early receptor trafficking events leading to enhanced EGFR degradation in adenovirus-infected cells. Specifically, we wished to determine whether adenovirus increases the rate of EGFR internalization or alters the subcellular compartmentalization of internalized EGFRs. Once the optimal time for measuring early trafficking events was determined, surface EGFRs were labeled with a cleavable biotin reagent to measure internalization rates and with a receptor-specific monoclonal antibody (MAb) conjugated to colloidal gold for intracellular localization studies. We first showed that the rate of EGFR internalization in adenovirus-infected cells is indistinguishable from the constitutive internalization rate for unoccupied EGFRs. The possibility that the E3 protein can affect trafficking of EGFRs internalized at a low constitutive rate was further supported by studies showing that adenovirus-mediated down-regulation occurs independently of EGFR oligomerization and intrinsic EGFR tyrosine kinase activity, which are required for efficient ligand-induced internalization. Other tyrosine kinases inhibited by genistein are also not required for adenovirus-induced down-regulation. When the intracellular localization of EGFRs during adenovirus-mediated down-regulation was examined by electron microscopy, there was a threefold increase in the number of EGFRs localized to multivesicular bodies. The multivesicular body has been proposed to be important for regulating intracellular membrane protein sorting, since trafficking patterns for receptors that recycle and receptors that are degraded diverge in this organelle. These data therefore suggest that adenovirus may enhance EGFR degradation by causing constitutively internalized EGFRs to accumulate in a prelysosomal compartment. This is the first example of a mechanism that efficiently down-regulates EGFR without significantly increasing the rate of internalization or that does not require EGFR tyrosine kinase activity. Since viral proteins often mimic or modify a host counterpart, this suggests that there are normal physiological conditions when receptor destruction without tyrosine signalling is beneficial.
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Affiliation(s)
- P Hoffman
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4970
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20
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Hoffman BL, Takishima K, Rosner MR, Carlin C. Adenovirus and protein kinase C have distinct molecular requirements for regulating epidermal growth factor receptor trafficking. J Cell Physiol 1993; 157:535-43. [PMID: 8253865 DOI: 10.1002/jcp.1041570313] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The ligand-activated tyrosine kinase receptor for epidermal growth factor (EGF) is down-regulated by an integral membrane protein coded for by the E3 early transcription unit of group C adenoviruses. The E3 protein appears to block recycling of constitutively internalized receptors, causing them instead to traffic to lysosomes where they are degraded. Expression of functional EGF receptors is also regulated by protein kinase C (PKC), which directly phosphorylates the EGF receptor at Thr-654. The goal of this study was to determine potential interactions between PKC and the E3 protein, since membrane-bound PKC activity is elevated by the adenovirus E1A protein. Our results show that although tumor promoters which activate PKC cause a coordinate induction of E3 protein synthesis and EGF receptor degradation, the E3 protein-induced pathway for receptor down-regulation functions independently of PKC and other kinases that are inhibited by staurosporine. This suggests that in contrast to other mechanisms that modulate receptor expression (i.e., ligand and PKC), the E3 protein is not regulated by phosphorylation but is constitutively active. We also report that adenovirus-mediated degradation is the preferred pathway in infected cells stimulated with 12-O-tetradecanoylphorbol-13-acetate (TPA) to induce receptor recycling.
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Affiliation(s)
- B L Hoffman
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106
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21
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Wold WS. Adenovirus genes that modulate the sensitivity of virus-infected cells to lysis by TNF. J Cell Biochem 1993; 53:329-35. [PMID: 8300750 DOI: 10.1002/jcb.240530410] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
TNF is a key inflammatory cytokine with antiviral properties. Human adenoviruses encode several intracellular proteins that mediate the effects of TNF. Expression of the adenovirus immediate early E1A proteins induces viral genes and a host of cellular genes, drives G0 cells into S-phase, and induces apoptosis and susceptibility to TNF-induced apoptosis. The adenovirus E1B-19K protein inhibits both E1A- and TNF-induced apoptosis. The E3-14.7K protein and the E3-10.4K/14.5K complex of proteins inhibit TNF- but not E1A-induced apoptosis. The E3 14.7K and 10.4K/14.5K proteins inhibit TNF activation of cytosolic phospholipase A2 (cPLA2), which may explain how they inhibit TNF cytolysis. Since eicosinoids produced from arachidonic acid (the product of cPLA2) are potent mediators of inflammation, the E3 proteins may block the inflammatory response to adenovirus infection. These adenovirus proteins should be novel tools to understand adenovirus pathogenesis, TNF signal transduction, and TNF cytolysis.
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Affiliation(s)
- W S Wold
- Department of Molecular Microbiology and Immunology, St. Louis University, Missouri 63104
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22
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Sipos L, von Heijne G. Predicting the topology of eukaryotic membrane proteins. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 213:1333-40. [PMID: 8099327 DOI: 10.1111/j.1432-1033.1993.tb17885.x] [Citation(s) in RCA: 228] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We show that the so-called 'positive inside' rule, i.e. the observation that positively charged amino acids tend to be more prevalent in cytoplasmic than in extra-cytoplasmic segments in transmembrane proteins [von Heijne, G. (1986) EMBO J. 5, 3021-3027], seems to hold for all polar segments in multi-spanning eukaryotic membrane proteins irrespective of their position in the sequence and hence can be used in conjunction with hydrophobicity analysis to predict their transmembrane topology. Further, as suggested by others, we confirm that the net charge difference across the first transmembrane segment correlates well with its orientation [Hartmann, E., Rapoport, T. A. and Lodish H. F. (1989) Proc. Natl Acad. Sci. USA 86, 5786-5790], and that the overall amino-acid composition of long polar segments can also be used to predict their cytoplasmic or extra-cytoplasmic location [Nakashima, H. and Nishikawa, K. (1992) FEBS Lett. 303, 141-146]. We present an approach to the topology prediction problem for eukaryotic membrane proteins based on a combination of these methods.
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Affiliation(s)
- L Sipos
- Department of Theoretical Physics, Royal Institute of Technology, Stockholm, Sweden
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23
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Kuivinen E, Hoffman BL, Hoffman PA, Carlin CR. Structurally related class I and class II receptor protein tyrosine kinases are down-regulated by the same E3 protein coded for by human group C adenoviruses. J Cell Biol 1993; 120:1271-9. [PMID: 8094718 PMCID: PMC2119731 DOI: 10.1083/jcb.120.5.1271] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Receptor tyrosine kinases (RTKs) are grouped into subcategories based on shared sequence and structural features. Human group C adenoviruses down-regulate EGF receptors, which are members of the class I family of RTKs, during the early stages of infection. Adenovirus appears to utilize a nonsaturable intracellular pathway since it causes EGF-R down-regulation even in cells that significantly overexpress EGF-R. Adenovirus-induced down-regulation is mediated by a small hydrophobic molecule coded for by the E3 early transcription region that has recently been localized to plasma membrane. Here we examine intracellular trafficking of other RTKs in adenovirus-infected cells, to better understand the molecular basis for the action of the E3 protein. Although p185c-neu, which is a class I RTK closely related to the EGF receptor, is down-regulated in cells expressing physiological concentrations of this molecule, it is not down-regulated in tumor cell lines that significantly overexpress p185c-neu. Cell surface receptors for insulin and IGF1, which are class II RTKs, are also reduced in cells expressing the E3 protein, although to a slightly lesser extent than the EGF receptor. Moreover, whereas EGF receptors are degraded between 3- and 9-h postinfection, insulin and IGF1 receptors are degraded between 6- and 12-h postinfection under identical conditions. In contrast to the class I and class II RTKs, there is no difference in the expression of the class III receptors for PDGF and aFGF in cells infected with a virus with an intact E3 region versus a virus mutant with an internal deletion in the relevant E3 gene. These results suggest that the E3 protein provides an internalization and degradative sorting signal for some class I and class II RTKs, although down-regulation of class II RTKs is somewhat less efficient. Molecular recognition of class I and class II RTKs during adenovirus infection may not be due strictly to amino acid structure, however, since EGF-R but not p185c-neu is down-regulated in cells where it is significantly overexpressed.
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Affiliation(s)
- E Kuivinen
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4970
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24
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Scaria A, Tollefson AE, Saha SK, Wold WS. The E3-11.6K protein of adenovirus is an Asn-glycosylated integral membrane protein that localizes to the nuclear membrane. Virology 1992; 191:743-53. [PMID: 1448922 DOI: 10.1016/0042-6822(92)90250-s] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The 11,600 MW (101 amino acids; 11.6K) protein of adenovirus 2 (Ad2) is a protein of unknown function which is synthesized in low amounts during early stages of infection but in very high amounts at late stages. The 11.6K protein migrates as three major groupings of diffuse bands of ca. 14K, 21K, and 31K on SDS-PAGE, indicating that 11.6K undergoes post-translational modification. We show here that 11.6K is Asn-glycosylated with complex (endo H-resistant) oligosaccharides and that 11.6K is an integral membrane protein. Immunofluorescence indicated that 11.6K initially is associated with the endoplasmic reticulum and Golgi apparatus and that it ultimately localizes to the nuclear membrane. The 11.6K protein is predicted to have a single signal-anchor sequence at residues 41-62 and only one potential Asn-linked glycosylation site at residue 14; thus, 11.6K must be oriented in the membranes with its NH2-terminus in the lumen and its COOH-terminus in the cytoplasm. The signal-anchor and glycosylation features of 11.6K are preserved in Ad2 and Ad5 (group C), and in Ad3 and Ad7 (group B), but the sequence of 11.6K is more diverged among these serotypes than is the sequence of most other adenovirus proteins.
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Affiliation(s)
- A Scaria
- Department of Molecular Microbiology and Immunology, St. Louis University School of Medicine, Missouri 63104
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25
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Hoffman P, Yaffe M, Hoffman B, Yei S, Wold W, Carlin C. Characterization of the adenovirus E3 protein that down-regulates the epidermal growth factor receptor. Evidence for intermolecular disulfide bonding and plasma membrane localization. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)42237-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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26
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Abstract
There is an open reading frame between ATG291 and TGA612 in the early region E3 transcription unit of adenovirus 2 (Ad2) that could encode a protein of 12,500 MW (12.5K). To address whether this protein is synthesized, we generated an antiserum against a TrpE-12.5K fusion protein which was expressed in Escherichia coli. This antiserum immunoprecipitated a doublet of about 12.5K apparent MW from [35S]Cys-labeled cells infected with Ad2, Ad5, and various mutants in other E3 genes. Mutants in the 12.5K gene did not produce this protein, and an in-frame deletion mutant showed a protein with a corresponding decrease in size. Cell-free translation of hybridization-purified RNA indicated that 12.5K is coded by E3 mRNA i. mRNA i is relatively scarce, and 12.5K is synthesized in correspondingly small amounts. The 12.5K protein was synthesized at early and late stages of infection in comparable amounts. Pulse-chase experiments indicated that 12.5K has a half-life of about 10 hr. The function of 12.5K is unknown, and the 12.5K gene can be deleted without affecting virus growth in cell culture. However, 12.5K is likely to be important in vivo because the gene is highly conserved in both Ad2 and Ad5 (group C adenoviruses), and also in Ad3 (group B).
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Affiliation(s)
- L K Hawkins
- Institute for Molecular Virology, St. Louis University School of Medicine, Missouri 63110
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Krajcsi P, Tollefson AE, Wold WS. The E3-14.5K integral membrane protein of adenovirus that is required for down-regulation of the EGF receptor and for prevention of TNF cytolysis is O-glycosylated but not N-glycosylated. Virology 1992; 188:570-9. [PMID: 1533979 DOI: 10.1016/0042-6822(92)90511-m] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The adenovirus E3-14.5K protein is a cytoplasmic integral membrane protein that functions in concert with the E3-10.4K protein to down-regulate the epidermal growth factor receptor and to prevent tumor necrosis factor cytolysis in adenovirus-infected cells. The 14.5K protein migrates as multiple bands in SDS-PAGE, indicating that it undergoes post-translational modification. The 14.5K protein is known to be phosphorylated on serine. We show here that 14.5K can be metabolically labeled with [3H]glucosamine, that the label is labile to alkali, and that the SDS-PAGE band pattern is simplified in a cell line that is defective in O-glycosylation. Thus, 14.5K is O-glycosylated, probably at a single site in the NH2-terminal lumenal domain. The protein was not metabolically labeled with [3H]mannose, and its SDS-PAGE band pattern was not affected by tunicamycin treatment in vivo or endo F treatment in vitro; thus, 14.5K is not N-glycosylated. There was no evidence that the 10.4K protein is glycosylated, and the 10.4K protein was not required for glycosylation of 14.5K. Virtually all 14.5K molecules appear to contain the core disaccharide Gal beta 1-3GalNAc alpha 1-Ser/Thr which is commonly found on mucin-type O-glycoproteins, and neuraminidase digestion experiments indicated that this disaccharide contains terminal sialic acid.
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Affiliation(s)
- P Krajcsi
- Institute for Molecular Virology, St. Louis University School of Medicine, Missouri 63110
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28
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Krajcsi P, Wold WS. The adenovirus E3-14.5K protein which is required for prevention of TNF cytolysis and for down-regulation of the EGF receptor contains phosphoserine. Virology 1992; 187:492-8. [PMID: 1532104 DOI: 10.1016/0042-6822(92)90451-t] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The E3-14.5K and E3-10.4K proteins form a complex and function to down-regulate the epidermal growth factor receptor and to prevent tumor necrosis factor cytolysis in adenovirus-infected cells. Both 14.5K and 10.4K are cytoplasmic membrane proteins with a Ccyt orientation in the membrane. We show here that 14.5K is phosphorylated on serine residues in cells infected by adenoviruses that synthesize both 14.5K and 10.4K. 14.5K is phosphorylated on both serine and threonine in cells infected by a mutant that does not synthesize 10.4K; thus, the presence or absence of 10.4K affects the phosphorylation of 14.5K. Phosphotyrosine was not detected. 14.5K is also phosphorylated when translated in vitro in a rabbit reticulocyte extract. Both in vivo and in vitro, at least one of the phosphorylation sites is near the C-terminus, in the cytoplasmic domain of 14.5K. This C-terminal region of 14.5K is the most conserved among Ad5, Ad2, Ad3, and Ad7, and it is essential for 14.5K to prevent tumor necrosis factor cytolysis.
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Affiliation(s)
- P Krajcsi
- Institute for Molecular Virology, St. Louis University School of Medicine, Missouri 63110
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