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Obergfäll D, Wild M, Sommerer M, Barillas Dahm M, Kicuntod J, Tillmanns J, Kögler M, Lösing J, Dhotre K, Müller R, Wangen C, Wagner S, Phan QV, Wiebusch L, Briestenská K, Mistríková J, Kerr-Jones L, Stanton RJ, Voigt S, Hahn F, Marschall M. Cyclin-Dependent Kinase 8 Represents a Positive Regulator of Cytomegalovirus Replication and a Novel Host Target for Antiviral Strategies. Pharmaceutics 2024; 16:1238. [PMID: 39339274 PMCID: PMC11435438 DOI: 10.3390/pharmaceutics16091238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2024] [Revised: 09/19/2024] [Accepted: 09/21/2024] [Indexed: 09/30/2024] Open
Abstract
Background. Cyclin-dependent kinase 8 (CDK8) is a multifaceted regulator and represents a catalytic component of the transcriptional Mediator complex. CDK8 activity, on the one hand, increases transcriptional elongation by the recruitment of Mediator/super elongation complexes, but, on the other hand, negatively regulates CDK7-controlled transcriptional initiation through inactivating cyclin H phosphorylation. Recently, these combined properties of CDK8 have also suggested its rate-limiting importance for herpesviral replication. Objectives. In this paper, we focused on human cytomegalovirus (HCMV) and addressed the question of whether the pharmacological inhibition or knock-down of CDK8 may affect viral replication efficiency in cell culture models. Methods. A number of human and animal herpesviruses, as well as non-herpesviruses, were used to analyze the importance of CDK8 for viral replication in cell culture models, and to assess the antiviral efficacy of CDK8 inhibitors. Results. Using clinically relevant CDK8 inhibitors (CCT-251921, MSC-2530818, and BI-1347), HCMV replication was found strongly reduced even at nanomolar drug concentrations. The EC50 values were consistent for three different HCMV strains (i.e., AD169, TB40, and Merlin) analyzed in two human cell types (i.e., primary fibroblasts and astrocytoma cells), and the drugs comprised a low level of cytotoxicity. The findings highlighted the following: (i) the pronounced in vitro SI values of anti-HCMV activity obtained with CDK8 inhibitors; (ii) a confirmation of the anti-HCMV efficacy by CDK8-siRNA knock-down; (iii) a CDK8-dependent reduction in viral immediate early, early, and late protein levels; (iv) a main importance of CDK8 for viral late-stage replication; (v) several mechanistic aspects, which point to a strong impact on viral progeny production and release, but a lack of CDK8 relevance for viral entry or nuclear egress; (vi) a significant anti-HCMV drug synergy for combinations of inhibitors against host CDK8 and the viral kinase vCDK/pUL97 (maribavir); (vii) finally, a broad-spectrum antiviral activity, as seen for the comparison of selected α-, β-, γ-, and non-herpesviruses. Conclusions. In summary, these novel data provide evidence for the importance of CDK8 as a positive regulator of herpesviral replication efficiency, and moreover, suggest its exploitability as an antiviral target for novel strategies of host-directed drug development.
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Affiliation(s)
- Debora Obergfäll
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (D.O.); (M.W.); (M.S.); (M.B.D.); (J.K.); (J.T.); (M.K.); (J.L.); (K.D.); (R.M.); (C.W.); (S.W.); (F.H.)
| | - Markus Wild
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (D.O.); (M.W.); (M.S.); (M.B.D.); (J.K.); (J.T.); (M.K.); (J.L.); (K.D.); (R.M.); (C.W.); (S.W.); (F.H.)
| | - Mona Sommerer
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (D.O.); (M.W.); (M.S.); (M.B.D.); (J.K.); (J.T.); (M.K.); (J.L.); (K.D.); (R.M.); (C.W.); (S.W.); (F.H.)
| | - Malena Barillas Dahm
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (D.O.); (M.W.); (M.S.); (M.B.D.); (J.K.); (J.T.); (M.K.); (J.L.); (K.D.); (R.M.); (C.W.); (S.W.); (F.H.)
| | - Jintawee Kicuntod
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (D.O.); (M.W.); (M.S.); (M.B.D.); (J.K.); (J.T.); (M.K.); (J.L.); (K.D.); (R.M.); (C.W.); (S.W.); (F.H.)
| | - Julia Tillmanns
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (D.O.); (M.W.); (M.S.); (M.B.D.); (J.K.); (J.T.); (M.K.); (J.L.); (K.D.); (R.M.); (C.W.); (S.W.); (F.H.)
| | - Melanie Kögler
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (D.O.); (M.W.); (M.S.); (M.B.D.); (J.K.); (J.T.); (M.K.); (J.L.); (K.D.); (R.M.); (C.W.); (S.W.); (F.H.)
| | - Josephine Lösing
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (D.O.); (M.W.); (M.S.); (M.B.D.); (J.K.); (J.T.); (M.K.); (J.L.); (K.D.); (R.M.); (C.W.); (S.W.); (F.H.)
| | - Kishore Dhotre
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (D.O.); (M.W.); (M.S.); (M.B.D.); (J.K.); (J.T.); (M.K.); (J.L.); (K.D.); (R.M.); (C.W.); (S.W.); (F.H.)
| | - Regina Müller
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (D.O.); (M.W.); (M.S.); (M.B.D.); (J.K.); (J.T.); (M.K.); (J.L.); (K.D.); (R.M.); (C.W.); (S.W.); (F.H.)
| | - Christina Wangen
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (D.O.); (M.W.); (M.S.); (M.B.D.); (J.K.); (J.T.); (M.K.); (J.L.); (K.D.); (R.M.); (C.W.); (S.W.); (F.H.)
| | - Sabrina Wagner
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (D.O.); (M.W.); (M.S.); (M.B.D.); (J.K.); (J.T.); (M.K.); (J.L.); (K.D.); (R.M.); (C.W.); (S.W.); (F.H.)
| | - Quang V. Phan
- Department of Pediatric Oncology and Hematology, Charité—Universitätsmedizin Berlin, Campus Virchow-Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany; (Q.V.P.); (L.W.)
- Richard Sherwood Laboratory, Brigham and Women’s Hospital, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, USA
| | - Lüder Wiebusch
- Department of Pediatric Oncology and Hematology, Charité—Universitätsmedizin Berlin, Campus Virchow-Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany; (Q.V.P.); (L.W.)
| | - Katarína Briestenská
- Department of Microbiology and Virology, Faculty of Natural Sciences, Comenius University in Bratislava, Ilkovičova 6, 842 15 Bratislava, Slovakia; (K.B.); (J.M.)
- Institute of Virology, Biomedical Research Center, Slovak Academy of Sciences, Dúbravská Cesta 9, 845 05 Bratislava, Slovakia
| | - Jela Mistríková
- Department of Microbiology and Virology, Faculty of Natural Sciences, Comenius University in Bratislava, Ilkovičova 6, 842 15 Bratislava, Slovakia; (K.B.); (J.M.)
- Institute of Virology, Biomedical Research Center, Slovak Academy of Sciences, Dúbravská Cesta 9, 845 05 Bratislava, Slovakia
| | - Lauren Kerr-Jones
- Division of Infection & Immunity, School of Medicine, Cardiff University, Henry Wellcome Building, Heath Park, Cardiff CF14 4XN, UK; (L.K.-J.); (R.J.S.)
| | - Richard J. Stanton
- Division of Infection & Immunity, School of Medicine, Cardiff University, Henry Wellcome Building, Heath Park, Cardiff CF14 4XN, UK; (L.K.-J.); (R.J.S.)
| | - Sebastian Voigt
- University Clinical Center Essen (Universitätsklinikum, AöR), Institute for Virology, Virchowstr. 179, 45147 Essen, Germany;
| | - Friedrich Hahn
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (D.O.); (M.W.); (M.S.); (M.B.D.); (J.K.); (J.T.); (M.K.); (J.L.); (K.D.); (R.M.); (C.W.); (S.W.); (F.H.)
| | - Manfred Marschall
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (D.O.); (M.W.); (M.S.); (M.B.D.); (J.K.); (J.T.); (M.K.); (J.L.); (K.D.); (R.M.); (C.W.); (S.W.); (F.H.)
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Marschall M, Schütz M, Wild M, Socher E, Wangen C, Dhotre K, Rawlinson WD, Sticht H. Understanding the Cytomegalovirus Cyclin-Dependent Kinase Ortholog pUL97 as a Multifaceted Regulator and an Antiviral Drug Target. Cells 2024; 13:1338. [PMID: 39195228 DOI: 10.3390/cells13161338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2024] [Revised: 07/31/2024] [Accepted: 08/06/2024] [Indexed: 08/29/2024] Open
Abstract
Herpesviral protein kinases, such as the therapy-relevant pUL97 of human cytomegalovirus (HCMV), are important for viral replication efficiency as well as pathogenesis, and represent key antiviral drug targets. HCMV pUL97 is a viral cyclin-dependent kinase (CDK) ortholog, as it shares functional and structural properties with human CDKs. Recently, the formation of vCDK/pUL97-cyclin complexes and the phosphorylation of a variety of viral and cellular substrate proteins has been demonstrated. Genetic mapping and structural modeling approaches helped to define two pUL97 interfaces, IF1 and IF2, responsible for cyclin binding. In particular, the regulatory importance of interactions between vCDK/pUL97 and host cyclins as well as CDKs has been highlighted, both as determinants of virus replication and as a novel drug-targeting option. This aspect was substantiated by the finding that virus replication was impaired upon cyclin type H knock-down, and that such host-directed interference also affected viruses resistant to existing therapies. Beyond the formation of binary interactive complexes, a ternary pUL97-cyclin H-CDK7 complex has also been described, and in light of this, an experimental trans-stimulation of CDK7 activity by pUL97 appeared crucial for virus-host coregulation. In accordance with this understanding, several novel antiviral targeting options have emerged. These include kinase inhibitors directed to pUL97, to host CDKs, and to the pUL97-cyclin H interactive complexes. Importantly, a statistically significant drug synergy has recently been reported for antiviral treatment schemes using combinations of pharmacologically relevant CDK7 and vCDK/pUL97 inhibitors, including maribavir. Combined, such findings provide increased options for anti-HCMV control. This review focuses on regulatory interactions of vCDK/pUL97 with the host cyclin-CDK apparatus, and it addresses the functional relevance of these key effector complexes for viral replication and pathogenesis. On this basis, novel strategies of antiviral drug targeting are defined.
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Affiliation(s)
- Manfred Marschall
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - Martin Schütz
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - Markus Wild
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - Eileen Socher
- Institute of Anatomy, Functional and Clinical Anatomy, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Christina Wangen
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - Kishore Dhotre
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - William D Rawlinson
- Serology and Virology Division, NSW Health Pathology Microbiology, Prince of Wales Hospital, and Schools of Biomedical Sciences, Women's and Children's Health, Medicine and Biotechnology and Biomolecular Sciences, University of New South Wales, High Street, Sydney 2050, Australia
| | - Heinrich Sticht
- Division of Bioinformatics, Institute of Biochemistry, FAU, 91054 Erlangen, Germany
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Pastor F, Charles E, Belmudes L, Chabrolles H, Cescato M, Rivoire M, Burger T, Passot G, Durantel D, Lucifora J, Couté Y, Salvetti A. Deciphering the phospho-signature induced by hepatitis B virus in primary human hepatocytes. Front Microbiol 2024; 15:1415449. [PMID: 38841065 PMCID: PMC11150682 DOI: 10.3389/fmicb.2024.1415449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2024] [Accepted: 05/02/2024] [Indexed: 06/07/2024] Open
Abstract
Phosphorylation is a major post-translation modification (PTM) of proteins which is finely tuned by the activity of several hundred kinases and phosphatases. It controls most if not all cellular pathways including anti-viral responses. Accordingly, viruses often induce important changes in the phosphorylation of host factors that can either promote or counteract viral replication. Among more than 500 kinases constituting the human kinome only few have been described as important for the hepatitis B virus (HBV) infectious cycle, and most of them intervene during early or late infectious steps by phosphorylating the viral Core (HBc) protein. In addition, little is known on the consequences of HBV infection on the activity of cellular kinases. The objective of this study was to investigate the global impact of HBV infection on the cellular phosphorylation landscape early after infection. For this, primary human hepatocytes (PHHs) were challenged or not with HBV, and a mass spectrometry (MS)-based quantitative phosphoproteomic analysis was conducted 2- and 7-days post-infection. The results indicated that while, as expected, HBV infection only minimally modified the cell proteome, significant changes were observed in the phosphorylation state of several host proteins at both time points. Gene enrichment and ontology analyses of up- and down-phosphorylated proteins revealed common and distinct signatures induced by infection. In particular, HBV infection resulted in up-phosphorylation of proteins involved in DNA damage signaling and repair, RNA metabolism, in particular splicing, and cytoplasmic cell-signaling. Down-phosphorylated proteins were mostly involved in cell signaling and communication. Validation studies carried out on selected up-phosphorylated proteins, revealed that HBV infection induced a DNA damage response characterized by the appearance of 53BP1 foci, the inactivation of which by siRNA increased cccDNA levels. In addition, among up-phosphorylated RNA binding proteins (RBPs), SRRM2, a major scaffold of nuclear speckles behaved as an antiviral factor. In accordance with these findings, kinase prediction analysis indicated that HBV infection upregulates the activity of major kinases involved in DNA repair. These results strongly suggest that HBV infection triggers an intrinsic anti-viral response involving DNA repair factors and RBPs that contribute to reduce HBV replication in cell culture models.
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Affiliation(s)
- Florentin Pastor
- International Center for Research in Infectiology (CIRI), INSERM U1111, Université Claude Bernard Lyon, CNRS, UMR5308, ENS, Lyon, France
| | - Emilie Charles
- International Center for Research in Infectiology (CIRI), INSERM U1111, Université Claude Bernard Lyon, CNRS, UMR5308, ENS, Lyon, France
| | - Lucid Belmudes
- Université Grenoble Alpes, CEA, INSERM, UA13 BGE, CEA, CNRS, FR2048, Grenoble, France
| | - Hélène Chabrolles
- International Center for Research in Infectiology (CIRI), INSERM U1111, Université Claude Bernard Lyon, CNRS, UMR5308, ENS, Lyon, France
| | - Marion Cescato
- International Center for Research in Infectiology (CIRI), INSERM U1111, Université Claude Bernard Lyon, CNRS, UMR5308, ENS, Lyon, France
| | | | - Thomas Burger
- Université Grenoble Alpes, CEA, INSERM, UA13 BGE, CEA, CNRS, FR2048, Grenoble, France
| | - Guillaume Passot
- Service de Chirurgie Générale et Oncologique, Hôpital Lyon Sud, Hospices Civils de Lyon Et CICLY, EA3738, Université Claude Bernard Lyon, Lyon, France
| | - David Durantel
- International Center for Research in Infectiology (CIRI), INSERM U1111, Université Claude Bernard Lyon, CNRS, UMR5308, ENS, Lyon, France
| | - Julie Lucifora
- International Center for Research in Infectiology (CIRI), INSERM U1111, Université Claude Bernard Lyon, CNRS, UMR5308, ENS, Lyon, France
| | - Yohann Couté
- Université Grenoble Alpes, CEA, INSERM, UA13 BGE, CEA, CNRS, FR2048, Grenoble, France
| | - Anna Salvetti
- International Center for Research in Infectiology (CIRI), INSERM U1111, Université Claude Bernard Lyon, CNRS, UMR5308, ENS, Lyon, France
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Al Tarrass M, Belmudes L, Koça D, Azemard V, Liu H, Al Tabosh T, Ciais D, Desroches-Castan A, Battail C, Couté Y, Bouvard C, Bailly S. Large-scale phosphoproteomics reveals activation of the MAPK/GADD45β/P38 axis and cell cycle inhibition in response to BMP9 and BMP10 stimulation in endothelial cells. Cell Commun Signal 2024; 22:158. [PMID: 38439036 PMCID: PMC10910747 DOI: 10.1186/s12964-024-01486-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Accepted: 01/11/2024] [Indexed: 03/06/2024] Open
Abstract
BACKGROUND BMP9 and BMP10 are two major regulators of vascular homeostasis. These two ligands bind with high affinity to the endothelial type I kinase receptor ALK1, together with a type II receptor, leading to the direct phosphorylation of the SMAD transcription factors. Apart from this canonical pathway, little is known. Interestingly, mutations in this signaling pathway have been identified in two rare cardiovascular diseases, hereditary hemorrhagic telangiectasia and pulmonary arterial hypertension. METHODS To get an overview of the signaling pathways modulated by BMP9 and BMP10 stimulation in endothelial cells, we employed an unbiased phosphoproteomic-based strategy. Identified phosphosites were validated by western blot analysis and regulated targets by RT-qPCR. Cell cycle analysis was analyzed by flow cytometry. RESULTS Large-scale phosphoproteomics revealed that BMP9 and BMP10 treatment induced a very similar phosphoproteomic profile. These BMPs activated a non-canonical transcriptional SMAD-dependent MAPK pathway (MEKK4/P38). We were able to validate this signaling pathway and demonstrated that this activation required the expression of the protein GADD45β. In turn, activated P38 phosphorylated the heat shock protein HSP27 and the endocytosis protein Eps15 (EGF receptor pathway substrate), and regulated the expression of specific genes (E-selectin, hyaluronan synthase 2 and cyclooxygenase 2). This study also highlighted the modulation in phosphorylation of proteins involved in transcriptional regulation (phosphorylation of the endothelial transcription factor ERG) and cell cycle inhibition (CDK4/6 pathway). Accordingly, we found that BMP10 induced a G1 cell cycle arrest and inhibited the mRNA expression of E2F2, cyclinD1 and cyclinA1. CONCLUSIONS Overall, our phosphoproteomic screen identified numerous proteins whose phosphorylation state is impacted by BMP9 and BMP10 treatment, paving the way for a better understanding of the molecular mechanisms regulated by BMP signaling in vascular diseases.
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Affiliation(s)
- Mohammad Al Tarrass
- Biosanté Unit U1292, Grenoble Alpes University, CEA, Grenoble, 38000, France
| | - Lucid Belmudes
- Grenoble Alpes University, CEA, INSERM, UA13 BGE, CNRS, CEA, FR2048, Grenoble, France
| | - Dzenis Koça
- Biosanté Unit U1292, Grenoble Alpes University, CEA, Grenoble, 38000, France
| | - Valentin Azemard
- Biosanté Unit U1292, Grenoble Alpes University, CEA, Grenoble, 38000, France
| | - Hequn Liu
- Biosanté Unit U1292, Grenoble Alpes University, CEA, Grenoble, 38000, France
| | - Tala Al Tabosh
- Biosanté Unit U1292, Grenoble Alpes University, CEA, Grenoble, 38000, France
| | - Delphine Ciais
- Biosanté Unit U1292, Grenoble Alpes University, CEA, Grenoble, 38000, France
- Present address: Université Côte d'Azur, CNRS, INSERM, iBV, Nice, France
| | | | - Christophe Battail
- Biosanté Unit U1292, Grenoble Alpes University, CEA, Grenoble, 38000, France
- Grenoble Alpes University, CEA, INSERM, UA13 BGE, CNRS, CEA, FR2048, Grenoble, France
| | - Yohann Couté
- Grenoble Alpes University, CEA, INSERM, UA13 BGE, CNRS, CEA, FR2048, Grenoble, France
| | - Claire Bouvard
- Biosanté Unit U1292, Grenoble Alpes University, CEA, Grenoble, 38000, France
| | - Sabine Bailly
- Biosanté Unit U1292, Grenoble Alpes University, CEA, Grenoble, 38000, France.
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Tillmanns J, Kicuntod J, Lösing J, Marschall M. 'Getting Better'-Is It a Feasible Strategy of Broad Pan-Antiherpesviral Drug Targeting by Using the Nuclear Egress-Directed Mechanism? Int J Mol Sci 2024; 25:2823. [PMID: 38474070 DOI: 10.3390/ijms25052823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2024] [Revised: 02/24/2024] [Accepted: 02/26/2024] [Indexed: 03/14/2024] Open
Abstract
The herpesviral nuclear egress represents an essential step of viral replication efficiency in host cells, as it defines the nucleocytoplasmic release of viral capsids. Due to the size limitation of the nuclear pores, viral nuclear capsids are unable to traverse the nuclear envelope without a destabilization of this natural host-specific barrier. To this end, herpesviruses evolved the regulatory nuclear egress complex (NEC), composed of a heterodimer unit of two conserved viral NEC proteins (core NEC) and a large-size extension of this complex including various viral and cellular NEC-associated proteins (multicomponent NEC). Notably, the NEC harbors the pronounced ability to oligomerize (core NEC hexamers and lattices), to multimerize into higher-order complexes, and, ultimately, to closely interact with the migrating nuclear capsids. Moreover, most, if not all, of these NEC proteins comprise regulatory modifications by phosphorylation, so that the responsible kinases, and additional enzymatic activities, are part of the multicomponent NEC. This sophisticated basis of NEC-specific structural and functional interactions offers a variety of different modes of antiviral interference by pharmacological or nonconventional inhibitors. Since the multifaceted combination of NEC activities represents a highly conserved key regulatory stage of herpesviral replication, it may provide a unique opportunity towards a broad, pan-antiherpesviral mechanism of drug targeting. This review presents an update on chances, challenges, and current achievements in the development of NEC-directed antiherpesviral strategies.
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Affiliation(s)
- Julia Tillmanns
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - Jintawee Kicuntod
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - Josephine Lösing
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - Manfred Marschall
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
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Borges PHO, Ferreira SB, Silva FP. Recent Advances on Targeting Proteases for Antiviral Development. Viruses 2024; 16:366. [PMID: 38543732 PMCID: PMC10976044 DOI: 10.3390/v16030366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Revised: 02/21/2024] [Accepted: 02/24/2024] [Indexed: 05/23/2024] Open
Abstract
Viral proteases are an important target for drug development, since they can modulate vital pathways in viral replication, maturation, assembly and cell entry. With the (re)appearance of several new viruses responsible for causing diseases in humans, like the West Nile virus (WNV) and the recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), understanding the mechanisms behind blocking viral protease's function is pivotal for the development of new antiviral drugs and therapeutical strategies. Apart from directly inhibiting the target protease, usually by targeting its active site, several new pathways have been explored to impair its activity, such as inducing protein aggregation, targeting allosteric sites or by inducing protein degradation by cellular proteasomes, which can be extremely valuable when considering the emerging drug-resistant strains. In this review, we aim to discuss the recent advances on a broad range of viral proteases inhibitors, therapies and molecular approaches for protein inactivation or degradation, giving an insight on different possible strategies against this important class of antiviral target.
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Affiliation(s)
- Pedro Henrique Oliveira Borges
- Laboratory of Organic Synthesis and Biological Prospecting, Chemistry Institute, Federal University of Rio de Janeiro, Rio de Janeiro 21941-909, Brazil;
- Laboratory of Experimental and Computational Biochemistry of Drugs, Oswaldo Cruz Institute, Fiocruz, Rio de Janeiro 21040-900, Brazil
| | - Sabrina Baptista Ferreira
- Laboratory of Organic Synthesis and Biological Prospecting, Chemistry Institute, Federal University of Rio de Janeiro, Rio de Janeiro 21941-909, Brazil;
| | - Floriano Paes Silva
- Laboratory of Experimental and Computational Biochemistry of Drugs, Oswaldo Cruz Institute, Fiocruz, Rio de Janeiro 21040-900, Brazil
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Sucharita S, Krishnagopal A, van Drunen Littel-van den Hurk S. Comprehensive Analysis of the Tegument Proteins Involved in Capsid Transport and Virion Morphogenesis of Alpha, Beta and Gamma Herpesviruses. Viruses 2023; 15:2058. [PMID: 37896835 PMCID: PMC10611259 DOI: 10.3390/v15102058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 09/21/2023] [Accepted: 09/21/2023] [Indexed: 10/29/2023] Open
Abstract
Herpesviruses are enveloped and have an amorphous protein layer surrounding the capsid, which is termed the tegument. Tegument proteins perform critical functions throughout the viral life cycle. This review provides a comprehensive and comparative analysis of the roles of specific tegument proteins in capsid transport and virion morphogenesis of selected, well-studied prototypes of each of the three subfamilies of Herpesviridae i.e., human herpesvirus-1/herpes simplex virus-1 (Alphaherpesvirinae), human herpesvirus-5/cytomegalovirus (Betaherpesvirinae) and human herpesvirus -8/Kaposi's sarcomavirus (Gammaherpesvirinae). Most of the current knowledge is based on alpha herpesviruses, in particular HSV-1. While some tegument proteins are released into the cytoplasm after virus entry, several tegument proteins remain associated with the capsid and are responsible for transport to and docking at the nucleus. After replication and capsid formation, the capsid is enveloped at the nuclear membrane, which is referred to as primary envelopment, followed by de-envelopment and release into the cytoplasm. This requires involvement of at least three tegument proteins. Subsequently, multiple interactions between tegument proteins and capsid proteins, other tegument proteins and glycoproteins are required for assembly of the virus particles and envelopment at the Golgi, with certain tegument proteins acting as the central hub for these interactions. Some redundancy in these interactions ensures appropriate morphogenesis.
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Affiliation(s)
- Soumya Sucharita
- Biochemistry, Microbiology and Immunology, College of Medicine, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada; (S.S.); (A.K.)
- Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, SK S7N 5E3, Canada
| | - Akshaya Krishnagopal
- Biochemistry, Microbiology and Immunology, College of Medicine, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada; (S.S.); (A.K.)
- Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, SK S7N 5E3, Canada
| | - Sylvia van Drunen Littel-van den Hurk
- Biochemistry, Microbiology and Immunology, College of Medicine, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada; (S.S.); (A.K.)
- Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, SK S7N 5E3, Canada
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8
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Tillmanns J, Häge S, Borst EM, Wardin J, Eickhoff J, Klebl B, Wagner S, Wangen C, Hahn F, Socher E, Marschall M. Assessment of Covalently Binding Warhead Compounds in the Validation of the Cytomegalovirus Nuclear Egress Complex as an Antiviral Target. Cells 2023; 12:cells12081162. [PMID: 37190072 DOI: 10.3390/cells12081162] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 04/06/2023] [Accepted: 04/06/2023] [Indexed: 05/17/2023] Open
Abstract
Herpesviral nuclear egress is a regulated process of viral capsid nucleocytoplasmic release. Due to the large capsid size, a regular transport via the nuclear pores is unfeasible, so that a multistage-regulated export pathway through the nuclear lamina and both leaflets of the nuclear membrane has evolved. This process involves regulatory proteins, which support the local distortion of the nuclear envelope. For human cytomegalovirus (HCMV), the nuclear egress complex (NEC) is determined by the pUL50-pUL53 core that initiates multicomponent assembly with NEC-associated proteins and capsids. The transmembrane NEC protein pUL50 serves as a multi-interacting determinant that recruits regulatory proteins by direct and indirect contacts. The nucleoplasmic core NEC component pUL53 is strictly associated with pUL50 in a structurally defined hook-into-groove complex and is considered as the potential capsid-binding factor. Recently, we validated the concept of blocking the pUL50-pUL53 interaction by small molecules as well as cell-penetrating peptides or an overexpression of hook-like constructs, which can lead to a pronounced degree of antiviral activity. In this study, we extended this strategy by utilizing covalently binding warhead compounds, originally designed as binders of distinct cysteine residues in target proteins, such as regulatory kinases. Here, we addressed the possibility that warheads may likewise target viral NEC proteins, building on our previous crystallization-based structural analyses that revealed distinct cysteine residues in positions exposed from the hook-into-groove binding surface. To this end, the antiviral and NEC-binding properties of a selection of 21 warhead compounds were investigated. The combined findings are as follows: (i) warhead compounds exhibited a pronounced anti-HCMV potential in cell-culture-based infection models; (ii) computational analysis of NEC primary sequences and 3D structures revealed cysteine residues exposed to the hook-into-groove interaction surface; (iii) several of the active hit compounds exhibited NEC-blocking activity, as shown at the single-cell level by confocal imaging; (iv) the clinically approved warhead drug ibrutinib exerted a strong inhibitory impact on the pUL50-pUL53 core NEC interaction, as demonstrated by the NanoBiT assay system; and (v) the generation of recombinant HCMV ∆UL50-ΣUL53, allowing the assessment of viral replication under conditional expression of the viral core NEC proteins, was used for characterizing viral replication and a mechanistic evaluation of ibrutinib antiviral efficacy. Combined, the results point to a rate-limiting importance of the HCMV core NEC for viral replication and to the option of exploiting this determinant by the targeting of covalently NEC-binding warhead compounds.
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Affiliation(s)
- Julia Tillmanns
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - Sigrun Häge
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - Eva Maria Borst
- Institute of Virology, Hannover Medical School, 30625 Hannover, Germany
| | - Julia Wardin
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - Jan Eickhoff
- Lead Discovery Center GmbH (LDC), 44227 Dortmund, Germany
| | - Bert Klebl
- Lead Discovery Center GmbH (LDC), 44227 Dortmund, Germany
- The Norwegian College of Fishery Science UiT, The Arctic University of Norway, 9037 Tromsø, Norway
| | - Sabrina Wagner
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - Christina Wangen
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - Friedrich Hahn
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - Eileen Socher
- Institute of Anatomy, Functional and Clinical Anatomy, FAU, 91054 Erlangen, Germany
| | - Manfred Marschall
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
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Kicuntod J, Häge S, Lösing J, Kopar S, Muller YA, Marschall M. An antiviral targeting strategy based on the inducible interference with cytomegalovirus nuclear egress complex. Antiviral Res 2023; 212:105557. [PMID: 36796541 DOI: 10.1016/j.antiviral.2023.105557] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2022] [Revised: 02/09/2023] [Accepted: 02/13/2023] [Indexed: 02/16/2023]
Abstract
The nucleocytoplasmic capsid egress of herpesviruses like the human cytomegalovirus (HCMV) is based on a uniquely regulated process. The core nuclear egress complex (NEC) of HCMV, represented by the pUL50-pUL53 heterodimer, is able to oligomerize and thus to build hexameric lattices. Recently, we and others validated the NEC as a novel target for antiviral strategies. So far, the experimental targeting approaches included the development of NEC-directed small molecules, cell-penetrating peptides and NEC-directed mutagenesis. Our postulate states that an interference with the hook-into-groove interaction of pUL50-pUL53 prevents NEC formation and strictly limits viral replication efficiency. Here, we provide an experimental proof-of-concept of the antiviral strategy: the inducible intracellular expression of a NLS-Hook-GFP construct exerted a pronounced level of antiviral activity. The data provide evidence for the following points: (i) generation of a primary fibroblast population with inducible NLS-Hook-GFP expression showed nuclear localization of the construct, (ii) interaction between NLS-Hook-GFP and the viral core NEC was found specific for cytomegaloviruses but not for other herpesviruses, (iii) construct overexpression exerted a strong antiviral activity against three strains of HCMV, (iv) confocal imaging demonstrated the interference with NEC nuclear rim formation in HCMV-infected cells, and (v) quantitative nuclear egress assay confirmed the block of viral nucleocytoplasmic transition and, consequently, an inhibitory effect onto viral cytoplasmic virion assembly complex (cVAC). Combined, data confirmed that the specific interference with protein-protein interaction of the HCMV core NEC represents an efficient antiviral targeting strategy.
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Affiliation(s)
- Jintawee Kicuntod
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.
| | - Sigrun Häge
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.
| | - Josephine Lösing
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.
| | - Serli Kopar
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.
| | - Yves A Muller
- Division of Biotechnology, Department of Biology, FAU, Erlangen, Germany.
| | - Manfred Marschall
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.
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Lösing J, Häge S, Schütz M, Wagner S, Wardin J, Sticht H, Marschall M. 'Shared-Hook' and 'Changed-Hook' Binding Activities of Herpesviral Core Nuclear Egress Complexes Identified by Random Mutagenesis. Cells 2022; 11:cells11244030. [PMID: 36552794 PMCID: PMC9776765 DOI: 10.3390/cells11244030] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 12/07/2022] [Accepted: 12/09/2022] [Indexed: 12/15/2022] Open
Abstract
Herpesviruses replicate their genomes and assemble their capsids in the host cell nucleus. To progress towards morphogenesis in the cytoplasm, herpesviruses evolved the strategy of nuclear egress as a highly regulated process of nucleo-cytoplasmic capsid transition. The process is conserved among α-, β- and γ-herpesviruses and involves the formation of a core and multicomponent nuclear egress complex (NEC). Core NEC is assembled by the interaction between the nucleoplasmic hook protein, i.e., pUL53 (human cytomegalovirus, HCMV), and the integral membrane-associated groove protein, i.e., pUL50. Our study aimed at the question of whether a panherpesviral NEC scaffold may enable hook-into-groove interaction across herpesviral subfamilies. For this purpose, NEC constructs were generated for members of all three subfamilies and analyzed for multi-ligand interaction using a yeast two-hybrid (Y2H) approach with randomized pUL53 mutagenesis libraries. The screening identified ten library clones displaying cross-viral shared hook-into-groove interaction. Interestingly, a slightly modified Y2H screening strategy provided thirteen further changed-hook pUL53 clones having lost parental pUL50 interaction but gained homolog interaction. In addition, we designed a sequence-predicted hybrid construct based on HCMV and Epstein-Barr virus (EBV) core NEC proteins and identified a cross-viral interaction phenotype. Confirmation was provided by applying protein-protein interaction analyses in human cells, such as coimmunoprecipitation settings, confocal nuclear rim colocalization assays, and HCMV ΔUL53 infection experiments with pUL53-complementing cells. Combined, the study provided the first examples of cross-viral NEC interaction patterns and revealed a higher yield of human cell-confirmed binding clones using a library exchange rate of 3.4 than 2.7. Thus, the study provides improved insights into herpesviral NEC protein binding specificities of core NEC formation. This novel information might be exploited to gain a potential target scaffold for the development of broadly acting NEC-directed inhibitory small molecules.
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Affiliation(s)
- Josephine Lösing
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - Sigrun Häge
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - Martin Schütz
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - Sabrina Wagner
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - Julia Wardin
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - Heinrich Sticht
- Division of Bioinformatics, Institute of Biochemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
| | - Manfred Marschall
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany
- Correspondence: ; Tel.: +49-9131-85-26089
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11
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Turner DL, Mathias RA. The human cytomegalovirus decathlon: Ten critical replication events provide opportunities for restriction. Front Cell Dev Biol 2022; 10:1053139. [PMID: 36506089 PMCID: PMC9732275 DOI: 10.3389/fcell.2022.1053139] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2022] [Accepted: 11/10/2022] [Indexed: 11/27/2022] Open
Abstract
Human cytomegalovirus (HCMV) is a ubiquitous human pathogen that can cause severe disease in immunocompromised individuals, transplant recipients, and to the developing foetus during pregnancy. There is no protective vaccine currently available, and with only a limited number of antiviral drug options, resistant strains are constantly emerging. Successful completion of HCMV replication is an elegant feat from a molecular perspective, with both host and viral processes required at various stages. Remarkably, HCMV and other herpesviruses have protracted replication cycles, large genomes, complex virion structure and complicated nuclear and cytoplasmic replication events. In this review, we outline the 10 essential stages the virus must navigate to successfully complete replication. As each individual event along the replication continuum poses as a potential barrier for restriction, these essential checkpoints represent potential targets for antiviral development.
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Affiliation(s)
- Declan L. Turner
- Department of Microbiology, Infection and Immunity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
| | - Rommel A. Mathias
- Department of Microbiology, Infection and Immunity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
- Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC, Australia
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12
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‘Come Together’—The Regulatory Interaction of Herpesviral Nuclear Egress Proteins Comprises both Essential and Accessory Functions. Cells 2022; 11:cells11111837. [PMID: 35681532 PMCID: PMC9180862 DOI: 10.3390/cells11111837] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Revised: 05/31/2022] [Accepted: 06/01/2022] [Indexed: 02/01/2023] Open
Abstract
Herpesviral nuclear egress is a fine-tuned regulatory process that defines the nucleocytoplasmic release of viral capsids. Nuclear capsids are unable to traverse via nuclear pores due to the fact of their large size; therefore, herpesviruses evolved to develop a vesicular transport pathway mediating the transition across the two leaflets of the nuclear membrane. The entire process involves a number of regulatory proteins, which support the local distortion of the nuclear envelope. In the case of the prototype species of β-Herpesvirinae, the human cytomegalovirus (HCMV), the nuclear egress complex (NEC) is determined by the core proteins pUL50 and pUL53 that oligomerize, form capsid docking lattices and mediate multicomponent assembly with NEC-associated viral and cellular proteins. The NEC-binding principle is based on the hook-into-groove interaction through an N-terminal hook-like pUL53 protrusion that embraces an α-helical pUL50 binding groove. Thus far, the function and characteristics of herpesviral core NECs have been well studied and point to the groove proteins, such as pUL50, as the multi-interacting, major determinants of NEC formation and egress. This review provides closer insight into (i) sequence and structure conservation of herpesviral core NEC proteins, (ii) experimentation on cross-viral core NEC interactions, (iii) the essential functional roles of hook and groove proteins for viral replication, (iv) an establishment of assay systems for NEC-directed antiviral research and (v) the validation of NEC as putative antiviral drug targets. Finally, this article provides new insights into the conservation, function and antiviral targeting of herpesviral core NEC proteins and, into the complex regulatory role of hook and groove proteins during the assembly, egress and maturation of infectious virus.
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The Oligomeric Assemblies of Cytomegalovirus Core Nuclear Egress Proteins Are Associated with Host Kinases and Show Sensitivity to Antiviral Kinase Inhibitors. Viruses 2022; 14:v14051021. [PMID: 35632762 PMCID: PMC9146606 DOI: 10.3390/v14051021] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 05/03/2022] [Accepted: 05/09/2022] [Indexed: 02/04/2023] Open
Abstract
The nucleo-cytoplasmic capsid egress of herpesviruses is a unique regulated process that ensures the efficiency of viral replication and release. For human cytomegalovirus (HCMV), the core of the nuclear egress complex (NEC) consists of the pUL50–pUL53 heterodimer that is able to oligomerize and thus to build hexameric lattices. These structures determine capsid binding and multicomponent protein interaction including NEC-associated host factors. The underlying characteristic of the core NEC formation is based on the N-terminal hook structure of pUL53 that binds into an alpha-helical groove of pUL50, and is thus described as a hook-into-groove interaction. This central regulatory element has recently been validated as a target of antiviral strategies, and first NEC-targeted prototypes of inhibitory small molecules were reported by our previous study. Here, we further analyzed the oligomerization properties of the viral NEC through an approach of chemical protein cross-linking. Findings were as follows: (i) a cross-link approach demonstrated the oligomeric state of the HCMV core NEC using material from HCMV-infected or plasmid-transfected cells, (ii) a Western blot-based identification of NEC-associated kinases using the cross-linked multicomponent NECs was successful, and (iii) we demonstrated the NEC-inhibitory and antiviral activity of specific inhibitors directed to these target kinases. Combined, the results strongly underline the functional importance of the oligomerization of the HCMV-specific NEC that is both phosphorylation-dependent and sensitive to antiviral kinase inhibitors.
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14
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Wild M, Hahn F, Brückner N, Schütz M, Wangen C, Wagner S, Sommerer M, Strobl S, Marschall M. Cyclin-Dependent Kinases (CDKs) and the Human Cytomegalovirus-Encoded CDK Ortholog pUL97 Represent Highly Attractive Targets for Synergistic Drug Combinations. Int J Mol Sci 2022; 23:ijms23052493. [PMID: 35269635 PMCID: PMC8910733 DOI: 10.3390/ijms23052493] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 02/15/2022] [Accepted: 02/22/2022] [Indexed: 12/13/2022] Open
Abstract
Human cytomegalovirus (HCMV) is a pathogenic human herpesvirus associated with serious, potentially life-threatening symptoms in the immunocompromised or immunonaïve host. The limitations encountered by antiviral therapy options currently available include a narrow panel of accessible targets, the induction of viral drug resistance as well as severe drug dosage-mediated side-effects. Improved drug-targeting strategies to resolve these issues are the focus of our investigations. In particular, pharmaceutical kinase inhibitors (PKIs), either directed to host kinases or directed to the viral protein kinase pUL97, have been considered to overcome these restrictions. Recently, we reported the identification of a synergistic combination of two PKIs directed to host cyclin-dependent kinase 7 (CDK7) and viral CDK ortholog pUL97. Here, we substantiate these findings with the following results: (i) true drug synergy was exhibited by various chemical classes of PKI pairs directed to pUL97 and CDK7; (ii) no putative amplification of cytotoxicity by these drug combinations was observed; (iii) a reduction in drug dosage levels for synergistic combinations was defined on a quantitative basis and compared to monotreatments; (iv) the quantities of target proteins CDK7 and pUL97 expressed in HCMV-infected cells were assessed by confocal imaging, indicating a strong down-modulation of CDK7 levels as a result of synergistic drug treatment; (v) the functional importance of these target kinases, both binding to cyclin H, was illustrated by assessing HCMV replication under the viral genomic deletion of ORF-UL97 or cellular cyclin knock-out; (vi) new combinations of HCMV-specific drug synergy were demonstrated for solely host-directed treatments using PKIs against CDK2, CDK7, CDK8 and/or CDK9 and (vii) a triple PKI combination provided further support for the synergy approach. With these combined findings, this study highlights the potential of therapeutic drug combinations of approved, developmental and preclinical PKIs for expanding future options for anti-HCMV therapy.
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Affiliation(s)
- Markus Wild
- Institute for Clinical and Molecular Virology, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (M.W.); (F.H.); (N.B.); (M.S.); (C.W.); (S.W.); (M.S.)
| | - Friedrich Hahn
- Institute for Clinical and Molecular Virology, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (M.W.); (F.H.); (N.B.); (M.S.); (C.W.); (S.W.); (M.S.)
| | - Nadine Brückner
- Institute for Clinical and Molecular Virology, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (M.W.); (F.H.); (N.B.); (M.S.); (C.W.); (S.W.); (M.S.)
| | - Martin Schütz
- Institute for Clinical and Molecular Virology, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (M.W.); (F.H.); (N.B.); (M.S.); (C.W.); (S.W.); (M.S.)
| | - Christina Wangen
- Institute for Clinical and Molecular Virology, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (M.W.); (F.H.); (N.B.); (M.S.); (C.W.); (S.W.); (M.S.)
| | - Sabrina Wagner
- Institute for Clinical and Molecular Virology, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (M.W.); (F.H.); (N.B.); (M.S.); (C.W.); (S.W.); (M.S.)
| | - Mona Sommerer
- Institute for Clinical and Molecular Virology, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (M.W.); (F.H.); (N.B.); (M.S.); (C.W.); (S.W.); (M.S.)
| | - Stefan Strobl
- 4SC AG/4SC Discovery GmbH, Fraunhoferstraße 22, 82152 Planegg-Martinsried, Germany;
- BioNTech SE, Am Klopferspitz 19a, 82152 Planegg-Martinsried, Germany
| | - Manfred Marschall
- Institute for Clinical and Molecular Virology, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054 Erlangen, Germany; (M.W.); (F.H.); (N.B.); (M.S.); (C.W.); (S.W.); (M.S.)
- Correspondence: ; Tel.: +49-9131-8526089
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15
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Tyl MD, Betsinger CN, Cristea IM. Virus-host protein interactions as footprints of human cytomegalovirus replication. Curr Opin Virol 2022; 52:135-147. [PMID: 34923282 PMCID: PMC8844139 DOI: 10.1016/j.coviro.2021.11.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 11/24/2021] [Indexed: 02/03/2023]
Abstract
Human cytomegalovirus (HCMV) is a pervasive β-herpesvirus that causes lifelong infection. The lytic replication cycle of HCMV is characterized by global organelle remodeling and dynamic virus-host interactions, both of which are necessary for productive HCMV replication. With the advent of new technologies for investigating protein-protein and protein-nucleic acid interactions, numerous critical interfaces between HCMV and host cells have been identified. Here, we review temporal and spatial virus-host interactions that support different stages of the HCMV replication cycle. Understanding how HCMV interacts with host cells during entry, replication, and assembly, as well as how it interfaces with host cell metabolism and immune responses promises to illuminate processes that underlie the biology of infection and the resulting pathologies.
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Affiliation(s)
- Matthew D. Tyl
- Department of Molecular Biology, Princeton University, Lewis Thomas Laboratory, Washington Road, Princeton, NJ 08544, USA
| | - Cora N. Betsinger
- Department of Molecular Biology, Princeton University, Lewis Thomas Laboratory, Washington Road, Princeton, NJ 08544, USA
| | - Ileana M. Cristea
- Department of Molecular Biology, Princeton University, Lewis Thomas Laboratory, Washington Road, Princeton, NJ 08544, USA,Corresponding author and lead contact: Ileana M. Cristea, 210 Lewis Thomas Laboratory, Department of Molecular Biology, Princeton University, Princeton, NJ 08544, Tel: 6092589417, Fax: 6092584575,
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16
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Schweininger J, Kriegel M, Häge S, Conrad M, Alkhashrom S, Lösing J, Weiler S, Tillmanns J, Egerer-Sieber C, Decker A, Lenac Roviš T, Eichler J, Sticht H, Marschall M, Muller YA. The crystal structure of the varicella-zoster Orf24-Orf27 nuclear egress complex spotlights multiple determinants of herpesvirus subfamily specificity. J Biol Chem 2022; 298:101625. [PMID: 35074430 PMCID: PMC8867122 DOI: 10.1016/j.jbc.2022.101625] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 01/07/2022] [Accepted: 01/10/2022] [Indexed: 11/24/2022] Open
Abstract
Varicella-zoster virus (VZV) is a human pathogen from the α-subfamily of herpesviruses. The VZV Orf24-Orf27 complex represents the essential viral core nuclear egress complex (NEC) that orchestrates the egress of the preassembled virus capsids from the nucleus. While previous studies have primarily emphasized that the architecture of core NEC complexes is highly conserved among herpesviruses, the present report focuses on subfamily-specific structural and functional features that help explain the differences in the autologous versus nonautologous interaction patterns observed for NEC formation across herpesviruses. Here, we describe the crystal structure of the Orf24-Orf27 complex at 2.1 Å resolution. Coimmunoprecipitation and confocal imaging data show that Orf24-Orf27 complex formation displays some promiscuity in a herpesvirus subfamily-restricted manner. At the same time, analysis of thermodynamic parameters of NEC formation of three prototypical α-, β-, and γ herpesviruses, i.e., VZV, human cytomegalovirus (HCMV), and Epstein–Barr virus (EBV), revealed highly similar binding affinities for the autologous interaction with specific differences in enthalpy and entropy. Computational alanine scanning, structural comparisons, and mutational data highlight intermolecular interactions shared among α-herpesviruses that are clearly distinct from those seen in β- and γ-herpesviruses, including a salt bridge formed between Orf24-Arg167 and Orf27-Asp126. This interaction is located outside of the hook-into-groove interface and contributes significantly to the free energy of complex formation. Combined, these data explain distinct properties of specificity and permissivity so far observed in herpesviral NEC interactions. These findings will prove valuable in attempting to target multiple herpesvirus core NECs with selective or broad-acting drug candidates.
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Sanchez V, Britt W. Human Cytomegalovirus Egress: Overcoming Barriers and Co-Opting Cellular Functions. Viruses 2021; 14:v14010015. [PMID: 35062219 PMCID: PMC8778548 DOI: 10.3390/v14010015] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 12/06/2021] [Accepted: 12/16/2021] [Indexed: 12/11/2022] Open
Abstract
The assembly of human cytomegalovirus (HCMV) and other herpesviruses includes both nuclear and cytoplasmic phases. During the prolonged replication cycle of HCMV, the cell undergoes remarkable changes in cellular architecture that include marked increases in nuclear size and structure as well as the reorganization of membranes in cytoplasm. Similarly, significant changes occur in cellular metabolism, protein trafficking, and cellular homeostatic functions. These cellular modifications are considered integral in the efficient assembly of infectious progeny in productively infected cells. Nuclear egress of HCMV nucleocapsids is thought to follow a pathway similar to that proposed for other members of the herpesvirus family. During this process, viral nucleocapsids must overcome structural barriers in the nucleus that limit transit and, ultimately, their delivery to the cytoplasm for final assembly of progeny virions. HCMV, similar to other herpesviruses, encodes viral functions that co-opt cellular functions to overcome these barriers and to bridge the bilaminar nuclear membrane. In this brief review, we will highlight some of the mechanisms that define our current understanding of HCMV egress, relying heavily on the current understanding of egress of the more well-studied α-herpesviruses, HSV-1 and PRV.
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Affiliation(s)
- Veronica Sanchez
- Department of Pediatrics, University of Alabama School of Medicine, Birmingham, AL 35294, USA;
- Correspondence:
| | - William Britt
- Department of Pediatrics, University of Alabama School of Medicine, Birmingham, AL 35294, USA;
- Department of Microbiology, University of Alabama School of Medicine, Birmingham, AL 35294, USA
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18
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Hahn F, Hamilton ST, Wangen C, Wild M, Kicuntod J, Brückner N, Follett JEL, Herrmann L, Kheimar A, Kaufer BB, Rawlinson WD, Tsogoeva SB, Marschall M. Development of a PROTAC-Based Targeting Strategy Provides a Mechanistically Unique Mode of Anti-Cytomegalovirus Activity. Int J Mol Sci 2021; 22:12858. [PMID: 34884662 PMCID: PMC8657773 DOI: 10.3390/ijms222312858] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 11/24/2021] [Accepted: 11/24/2021] [Indexed: 12/31/2022] Open
Abstract
Human cytomegalovirus (HCMV) is a major pathogenic herpesvirus that is prevalent worldwide and it is associated with a variety of clinical symptoms. Current antiviral therapy options do not fully satisfy the medical needs; thus, improved drug classes and drug-targeting strategies are required. In particular, host-directed antivirals, including pharmaceutical kinase inhibitors, might help improve the drug qualities. Here, we focused on utilizing PROteolysis TArgeting Chimeras (PROTACs), i.e., hetero-bifunctional molecules containing two elements, namely a target-binding molecule and a proteolysis-inducing element. Specifically, a PROTAC that was based on a cyclin-dependent kinase (CDK) inhibitor, i.e., CDK9-directed PROTAC THAL-SNS032, was analyzed and proved to possess strong anti-HCMV AD169-GFP activity, with values of EC50 of 0.030 µM and CC50 of 0.175 µM (SI of 5.8). Comparing the effect of THAL-SNS032 with its non-PROTAC counterpart SNS032, data indicated a 3.7-fold stronger anti-HCMV efficacy. This antiviral activity, as illustrated for further clinically relevant strains of human and murine CMVs, coincided with the mid-nanomolar concentration range necessary for a drug-induced degradation of the primary (CDK9) and secondary targets (CDK1, CDK2, CDK7). In addition, further antiviral activities were demonstrated, such as the inhibition of SARS-CoV-2 replication, whereas other investigated human viruses (i.e., varicella zoster virus, adenovirus type 2, and Zika virus) were found insensitive. Combined, the antiviral quality of this approach is seen in its (i) mechanistic uniqueness; (ii) future options of combinatorial drug treatment; (iii) potential broad-spectrum activity; and (iv) applicability in clinically relevant antiviral models. These novel data are discussed in light of the current achievements of anti-HCMV drug development.
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Affiliation(s)
- Friedrich Hahn
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (C.W.); (M.W.); (J.K.); (N.B.)
| | - Stuart T. Hamilton
- Serology and Virology Division, NSW Health Pathology Microbiology, Prince of Wales Hospital, Schools of Women’s and Children’s Health, Medicine and Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2031, Australia; (S.T.H.); (J.E.L.F.); (W.D.R.)
| | - Christina Wangen
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (C.W.); (M.W.); (J.K.); (N.B.)
| | - Markus Wild
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (C.W.); (M.W.); (J.K.); (N.B.)
| | - Jintawee Kicuntod
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (C.W.); (M.W.); (J.K.); (N.B.)
| | - Nadine Brückner
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (C.W.); (M.W.); (J.K.); (N.B.)
| | - Jasmine E. L. Follett
- Serology and Virology Division, NSW Health Pathology Microbiology, Prince of Wales Hospital, Schools of Women’s and Children’s Health, Medicine and Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2031, Australia; (S.T.H.); (J.E.L.F.); (W.D.R.)
| | - Lars Herrmann
- Institute of Organic Chemistry I, FAU, 91058 Erlangen, Germany; (L.H.); (S.B.T.)
| | - Ahmed Kheimar
- Institute of Virology, Freie Universität Berlin, 14163 Berlin, Germany; (A.K.); (B.B.K.)
| | - Benedikt B. Kaufer
- Institute of Virology, Freie Universität Berlin, 14163 Berlin, Germany; (A.K.); (B.B.K.)
| | - William D. Rawlinson
- Serology and Virology Division, NSW Health Pathology Microbiology, Prince of Wales Hospital, Schools of Women’s and Children’s Health, Medicine and Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2031, Australia; (S.T.H.); (J.E.L.F.); (W.D.R.)
| | - Svetlana B. Tsogoeva
- Institute of Organic Chemistry I, FAU, 91058 Erlangen, Germany; (L.H.); (S.B.T.)
| | - Manfred Marschall
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (C.W.); (M.W.); (J.K.); (N.B.)
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19
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Häge S, Büscher N, Pakulska V, Hahn F, Adrait A, Krauter S, Borst EM, Schlötzer-Schrehardt U, Couté Y, Plachter B, Marschall M. The Complex Regulatory Role of Cytomegalovirus Nuclear Egress Protein pUL50 in the Production of Infectious Virus. Cells 2021; 10:3119. [PMID: 34831342 PMCID: PMC8625744 DOI: 10.3390/cells10113119] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 11/04/2021] [Accepted: 11/05/2021] [Indexed: 11/30/2022] Open
Abstract
The regulation of the nucleocytoplasmic release of herpesviral capsids is defined by the process of nuclear egress. Due to their large size, nuclear capsids are unable to traverse via nuclear pores, so that herpesviruses evolved to develop a vesicular transport pathway mediating their transition through both leaflets of the nuclear membrane. This process involves regulatory proteins, which support the local distortion of the nuclear envelope. For human cytomegalovirus (HCMV), the nuclear egress complex (NEC) is determined by the pUL50-pUL53 core that initiates multicomponent assembly with NEC-associated proteins and capsids. Hereby, pUL50 serves as a multi-interacting determinant that recruits several viral and cellular factors by direct and indirect contacts. Recently, we generated an ORF-UL50-deleted recombinant HCMV in pUL50-complementing cells and obtained first indications of putative additional functions of pUL50. In this study, we produced purified ΔUL50 particles under both complementing (ΔUL50C) and non-complementing (ΔUL50N) conditions and performed a phenotypical characterization. Findings were as follows: (i) ΔUL50N particle preparations exhibited a clear replicative defect in qPCR-based infection kinetics compared to ΔUL50C particles; (ii) immuno-EM analysis of ΔUL50C did not reveal major changes in nuclear distribution of pUL53 and lamin A/C; (iii) mass spectrometry-based quantitative proteomics showed a large concordance of protein contents in the NIEP fractions of ΔUL50C and ΔUL50N particles, but virion fraction was close to the detection limit for ΔUL50N; (iv) confocal imaging of viral marker proteins of immediate early (IE) and later phases of ΔUL50N infection indicated a very low number of cells showing an onset of viral lytic protein expression; and, finally (v) quantitative measurements of encapsidated genomes provided evidence for a substantial reduction in the DNA contents in ΔUL50N compared to ΔUL50C particles. In summary, the results point to a complex and important regulatory role of the HCMV nuclear egress protein pUL50 in the maturation of infectious virus.
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Affiliation(s)
- Sigrun Häge
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany;
| | - Nicole Büscher
- Institute for Virology and Forschungszentrum für Immuntherapie, University Medical Center of the Johannes Gutenberg-University Mainz, 55131 Mainz, Germany; (N.B.); (S.K.); (B.P.)
| | - Victoria Pakulska
- Institut National de la Santé et de la Recherche Médicale (INSERM), University Grenoble Alpes, CEA, UMR BioSanté U1292, CNRS, CEA, FR2048, 38000 Grenoble, France; (V.P.); (A.A.); (Y.C.)
| | - Friedrich Hahn
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany;
| | - Annie Adrait
- Institut National de la Santé et de la Recherche Médicale (INSERM), University Grenoble Alpes, CEA, UMR BioSanté U1292, CNRS, CEA, FR2048, 38000 Grenoble, France; (V.P.); (A.A.); (Y.C.)
| | - Steffi Krauter
- Institute for Virology and Forschungszentrum für Immuntherapie, University Medical Center of the Johannes Gutenberg-University Mainz, 55131 Mainz, Germany; (N.B.); (S.K.); (B.P.)
| | - Eva Maria Borst
- Institute of Virology, Hannover Medical School (MHH), 30625 Hannover, Germany;
| | | | - Yohann Couté
- Institut National de la Santé et de la Recherche Médicale (INSERM), University Grenoble Alpes, CEA, UMR BioSanté U1292, CNRS, CEA, FR2048, 38000 Grenoble, France; (V.P.); (A.A.); (Y.C.)
| | - Bodo Plachter
- Institute for Virology and Forschungszentrum für Immuntherapie, University Medical Center of the Johannes Gutenberg-University Mainz, 55131 Mainz, Germany; (N.B.); (S.K.); (B.P.)
| | - Manfred Marschall
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany;
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20
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Methodological Development of a Multi-Readout Assay for the Assessment of Antiviral Drugs against SARS-CoV-2. PATHOGENS (BASEL, SWITZERLAND) 2021; 10:pathogens10091076. [PMID: 34578109 PMCID: PMC8466411 DOI: 10.3390/pathogens10091076] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 07/30/2021] [Accepted: 08/23/2021] [Indexed: 02/07/2023]
Abstract
Currently, human infections with the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) are accelerating the ongoing spread of the pandemic. Several innovative types of vaccines have already been developed, whereas effective options of antiviral treatments still await a scientific implementation. The development of novel anti-SARS-CoV-2 drug candidates demands skillful strategies and analysis systems. Promising results have been achieved with first generation direct-acting antivirals targeting the viral polymerase RdRp or the protease 3CLpro. Such recently approved or investigational drugs like remdesivir and GC376 represent a basis for further development and optimization. Here, we establish a multi-readout assay (MRA) system that enables the antiviral assessment and mechanistic characterization of novel test compounds, drug repurposing and combination treatments. Our SARS-CoV-2-specific MRA combines the quantitative measurement of several parameters of virus infection, such as the intracellular production of proteins and genomes, enzymatic activities and virion release, as well as the use of reporter systems. In this regard, the antiviral efficacy of remdesivir and GC376 has been investigated in human Caco-2 cells. The readouts included the use of spike- and double-strand RNA-specific monoclonal antibodies for in-cell fluorescence imaging, a newly generated recombinant SARS-CoV-2 reporter virus d6YFP, the novel 3CLpro-based FRET CFP::YFP and the previously reported FlipGFP reporter assays, as well as viral genome-specific RT-qPCR. The data produced by our MRA confirm the high antiviral potency of these two drugs in vitro. Combined, this MRA approach may be applied for broader analyses of SARS-CoV-2-specific antivirals, including compound screenings and the characterization of selected drug candidates.
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21
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Functional Relevance of the Interaction between Human Cyclins and the Cytomegalovirus-Encoded CDK-Like Protein Kinase pUL97. Viruses 2021; 13:v13071248. [PMID: 34198986 PMCID: PMC8310212 DOI: 10.3390/v13071248] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 06/17/2021] [Accepted: 06/22/2021] [Indexed: 02/07/2023] Open
Abstract
The replication of human cytomegalovirus (HCMV) is characterized by a complex network of virus–host interaction. This involves the regulatory viral protein kinase pUL97, which represents a viral cyclin-dependent kinase ortholog (vCDK) combining typical structural and functional features of host CDKs. Notably, pUL97 interacts with the three human cyclin types T1, H and B1, whereby the binding region of cyclin T1 and the region conferring oligomerization of pUL97 were both assigned to amino acids 231–280. Here, we addressed the question of whether recombinant HCMVs harboring deletions in this region were impaired in cyclin interaction, kinase functionality or viral replication. To this end, recombinant HCMVs were generated by traceless BACmid mutagenesis and were phenotypically characterized using a methodological platform based on qPCR, coimmunoprecipitation, in vitro kinase assay (IVKA), Phos-tag Western blot and confocal imaging analysis. Combined data illustrate the following: (i) infection kinetics of all three recombinant HCMVs, i.e., ORF-UL97 ∆231–255, ∆256–280 and ∆231–280, showed impaired replication efficiency compared to the wild type, amongst which the largest deletion exhibited the most pronounced defect; (ii) specifically, this mutant ∆231–280 showed a loss of interaction with cyclin T1, as demonstrated by CoIP and confocal imaging; (iii) IVKA and Phos-tag analyses revealed strongly affected kinase activity for ∆231–280, with strong impairment of both autophosphorylation and substrate phosphorylation, but less pronounced impairments for ∆231–255 and ∆256–280; and (iv) a bioinformatic assessment of the pUL97–cyclin T1 complex led to the refinement of our current binding model. Thus, the results provide initial evidence for the functional importance of the pUL97–cyclin interaction concerning kinase activity and viral replication fitness.
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22
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Alkhashrom S, Kicuntod J, Häge S, Schweininger J, Muller YA, Lischka P, Marschall M, Eichler J. Exploring the Human Cytomegalovirus Core Nuclear Egress Complex as a Novel Antiviral Target: A New Type of Small Molecule Inhibitors. Viruses 2021; 13:v13030471. [PMID: 33809234 PMCID: PMC7998563 DOI: 10.3390/v13030471] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 03/08/2021] [Accepted: 03/09/2021] [Indexed: 12/15/2022] Open
Abstract
Nuclear egress is an essential process in the replication of human cytomegalovirus (HCMV), as it enables the migration of newly formed viral capsids from the nucleus into the cytoplasm. Inhibition of the HCMV core nuclear egress complex (core NEC), composed of viral proteins pUL50 and pUL53, has been proposed as a potential new target for the treatment of HCMV infection and disease. Here, we present a new type of small molecule inhibitors of HCMV core NEC formation, which inhibit the pUL50-pUL53 interaction at nanomolar concentrations. These inhibitors, i.e., verteporfin and merbromin, were identified through the screening of the Prestwick Chemical Library® of approved drug compounds. The inhibitory effect of merbromin is both compound- and target-specific, as no inhibition was seen for other mercury-organic compounds. Furthermore, merbromin does not inhibit an unrelated protein-protein interaction either. More importantly, merbromin was found to inhibit HCMV infection of cells in three different assays, as well as to disrupt HCMV NEC nuclear rim formation. Thus, while not being an ideal drug candidate by itself, merbromin may serve as a blueprint for small molecules with high HCMV core NEC inhibitory potential, as candidates for novel anti-herpesviral drugs.
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Affiliation(s)
- Sewar Alkhashrom
- Division of Medicinal Chemistry, Department of Chemistry and Pharmacy, University of Erlangen-Nürnberg (FAU), 91058 Erlangen, Germany;
| | - Jintawee Kicuntod
- Institute for Clinical and Molecular Virology, University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (J.K.); (S.H.); (M.M.)
| | - Sigrun Häge
- Institute for Clinical and Molecular Virology, University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (J.K.); (S.H.); (M.M.)
| | - Johannes Schweininger
- Division of Biotechnology, Department of Biology, University of Erlangen-Nürnberg (FAU), 91052 Erlangen, Germany; (J.S.); (Y.A.M.)
| | - Yves A. Muller
- Division of Biotechnology, Department of Biology, University of Erlangen-Nürnberg (FAU), 91052 Erlangen, Germany; (J.S.); (Y.A.M.)
| | - Peter Lischka
- AiCuris Anti-Infective Cures GmbH, 42117 Wuppertal, Germany;
| | - Manfred Marschall
- Institute for Clinical and Molecular Virology, University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (J.K.); (S.H.); (M.M.)
| | - Jutta Eichler
- Division of Medicinal Chemistry, Department of Chemistry and Pharmacy, University of Erlangen-Nürnberg (FAU), 91058 Erlangen, Germany;
- Correspondence: ; Tel.: +49-9131-856-5466
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23
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Häge S, Sonntag E, Svrlanska A, Borst EM, Stilp AC, Horsch D, Müller R, Kropff B, Milbradt J, Stamminger T, Schlötzer-Schrehardt U, Marschall M. Phenotypical Characterization of the Nuclear Egress of Recombinant Cytomegaloviruses Reveals Defective Replication upon ORF-UL50 Deletion but Not pUL50 Phosphosite Mutation. Viruses 2021; 13:v13020165. [PMID: 33499341 PMCID: PMC7911381 DOI: 10.3390/v13020165] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 01/15/2021] [Accepted: 01/19/2021] [Indexed: 12/19/2022] Open
Abstract
Nuclear egress is a common herpesviral process regulating nucleocytoplasmic capsid release. For human cytomegalovirus (HCMV), the nuclear egress complex (NEC) is determined by the pUL50-pUL53 core that regulates multicomponent assembly with NEC-associated proteins and capsids. Recently, NEC crystal structures were resolved for α-, β- and γ-herpesviruses, revealing profound structural conservation, which was not mirrored, however, by primary sequence and binding properties. The NEC binding principle is based on hook-into-groove interaction through an N-terminal hook-like pUL53 protrusion that embraces an α-helical pUL50 binding groove. So far, pUL50 has been considered as the major kinase-interacting determinant and massive phosphorylation of pUL50-pUL53 was assigned to NEC formation and functionality. Here, we addressed the question of phenotypical changes of ORF-UL50-mutated HCMVs. Surprisingly, our analyses did not detect a predominant replication defect for most of these viral mutants, concerning parameters of replication kinetics (qPCR), viral protein production (Western blot/CoIP) and capsid egress (confocal imaging/EM). Specifically, only the ORF-UL50 deletion rescue virus showed a block of genome synthesis during late stages of infection, whereas all phosphosite mutants exhibited marginal differences compared to wild-type or revertants. These results (i) emphasize a rate-limiting function of pUL50 for nuclear egress, and (ii) demonstrate that mutations in all mapped pUL50 phosphosites may be largely compensated. A refined mechanistic concept points to a multifaceted nuclear egress regulation, for which the dependence on the expression and phosphorylation of pUL50 is discussed.
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Affiliation(s)
- Sigrun Häge
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (S.H.); (E.S.); (A.S.); (D.H.); (R.M.); (B.K.); (J.M.)
| | - Eric Sonntag
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (S.H.); (E.S.); (A.S.); (D.H.); (R.M.); (B.K.); (J.M.)
| | - Adriana Svrlanska
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (S.H.); (E.S.); (A.S.); (D.H.); (R.M.); (B.K.); (J.M.)
| | - Eva Maria Borst
- Institute of Virology, Hannover Medical School (MHH), 30625 Hannover, Germany;
| | - Anne-Charlotte Stilp
- Institute for Virology, Ulm University Medical Center, 89081 Ulm, Germany; (A.-C.S.); (T.S.)
| | - Deborah Horsch
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (S.H.); (E.S.); (A.S.); (D.H.); (R.M.); (B.K.); (J.M.)
| | - Regina Müller
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (S.H.); (E.S.); (A.S.); (D.H.); (R.M.); (B.K.); (J.M.)
| | - Barbara Kropff
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (S.H.); (E.S.); (A.S.); (D.H.); (R.M.); (B.K.); (J.M.)
| | - Jens Milbradt
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (S.H.); (E.S.); (A.S.); (D.H.); (R.M.); (B.K.); (J.M.)
| | - Thomas Stamminger
- Institute for Virology, Ulm University Medical Center, 89081 Ulm, Germany; (A.-C.S.); (T.S.)
| | | | - Manfred Marschall
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (S.H.); (E.S.); (A.S.); (D.H.); (R.M.); (B.K.); (J.M.)
- Correspondence: ; Tel.: +49-9131-8526089
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24
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Marschall M, Häge S, Conrad M, Alkhashrom S, Kicuntod J, Schweininger J, Kriegel M, Lösing J, Tillmanns J, Neipel F, Eichler J, Muller YA, Sticht H. Nuclear Egress Complexes of HCMV and Other Herpesviruses: Solving the Puzzle of Sequence Coevolution, Conserved Structures and Subfamily-Spanning Binding Properties. Viruses 2020; 12:v12060683. [PMID: 32599939 PMCID: PMC7354485 DOI: 10.3390/v12060683] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 06/19/2020] [Accepted: 06/23/2020] [Indexed: 12/11/2022] Open
Abstract
Herpesviruses uniquely express two essential nuclear egress-regulating proteins forming a heterodimeric nuclear egress complex (core NEC). These core NECs serve as hexameric lattice-structured platforms for capsid docking and recruit viral and cellular NEC-associated factors that jointly exert nuclear lamina as well as membrane-rearranging functions (multicomponent NEC). The regulation of nuclear egress has been profoundly analyzed for murine and human cytomegaloviruses (CMVs) on a mechanistic basis, followed by the description of core NEC crystal structures, first for HCMV, then HSV-1, PRV and EBV. Interestingly, the highly conserved structural domains of these proteins stand in contrast to a very limited sequence conservation of the key amino acids within core NEC-binding interfaces. Even more surprising, although a high functional consistency was found when regarding the basic role of NECs in nuclear egress, a clear specification was identified regarding the limited, subfamily-spanning binding properties of core NEC pairs and NEC multicomponent proteins. This review summarizes the evolving picture of the relationship between sequence coevolution, structural conservation and properties of NEC interaction, comparing HCMV to α-, β- and γ-herpesviruses. Since NECs represent substantially important elements of herpesviral replication that are considered as drug-accessible targets, their putative translational use for antiviral strategies is discussed.
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Affiliation(s)
- Manfred Marschall
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg, Medical Center, 91054 Erlangen, Germany; (S.H.); (J.K.); (J.L.); (J.T.); (F.N.)
- Correspondence: ; Tel.: +49-9131-85-26089
| | - Sigrun Häge
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg, Medical Center, 91054 Erlangen, Germany; (S.H.); (J.K.); (J.L.); (J.T.); (F.N.)
| | - Marcus Conrad
- Division of Bioinformatics, Institute of Biochemistry, Friedrich-Alexander University of Erlangen-Nürnberg, 91054 Erlangen, Germany; (M.C.); (H.S.)
| | - Sewar Alkhashrom
- Division of Medicinal Chemistry, Department of Chemistry and Pharmacy, Friedrich-Alexander University of Erlangen-Nürnberg, 91058 Erlangen, Germany; (S.A.); (J.E.)
| | - Jintawee Kicuntod
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg, Medical Center, 91054 Erlangen, Germany; (S.H.); (J.K.); (J.L.); (J.T.); (F.N.)
| | - Johannes Schweininger
- Division of Biotechnology, Department of Biology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91052 Erlangen, Germany; (J.S.); (M.K.); (Y.A.M.)
| | - Mark Kriegel
- Division of Biotechnology, Department of Biology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91052 Erlangen, Germany; (J.S.); (M.K.); (Y.A.M.)
| | - Josephine Lösing
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg, Medical Center, 91054 Erlangen, Germany; (S.H.); (J.K.); (J.L.); (J.T.); (F.N.)
| | - Julia Tillmanns
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg, Medical Center, 91054 Erlangen, Germany; (S.H.); (J.K.); (J.L.); (J.T.); (F.N.)
| | - Frank Neipel
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg, Medical Center, 91054 Erlangen, Germany; (S.H.); (J.K.); (J.L.); (J.T.); (F.N.)
| | - Jutta Eichler
- Division of Medicinal Chemistry, Department of Chemistry and Pharmacy, Friedrich-Alexander University of Erlangen-Nürnberg, 91058 Erlangen, Germany; (S.A.); (J.E.)
| | - Yves A. Muller
- Division of Biotechnology, Department of Biology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91052 Erlangen, Germany; (J.S.); (M.K.); (Y.A.M.)
| | - Heinrich Sticht
- Division of Bioinformatics, Institute of Biochemistry, Friedrich-Alexander University of Erlangen-Nürnberg, 91054 Erlangen, Germany; (M.C.); (H.S.)
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The Human Cytomegalovirus Transmembrane Protein pUL50 Induces Loss of VCP/p97 and Is Regulated by a Small Isoform of pUL50. J Virol 2020; 94:JVI.00110-20. [PMID: 32321808 DOI: 10.1128/jvi.00110-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 04/10/2020] [Indexed: 11/20/2022] Open
Abstract
The human cytomegalovirus (HCMV) UL50 gene encodes a transmembrane protein, pUL50, which acts as a core component of the nuclear egress complex (NEC) for nucleocapsids. Recently, pUL50 has been shown to have NEC-independent activities: downregulation of IRE1 to repress the unfolded protein response and degradation of UBE1L to inhibit the protein ISG15 modification pathway. Here, we demonstrate that a 26-kDa N-terminal truncated isoform of pUL50 (UL50-p26) is expressed from an internal methionine at amino acid position 199 and regulates the activity of pUL50 to induce the loss of valosin-containing protein (VCP/p97). A UL50(M199V) mutant virus expressing pUL50(M199V) but not UL50-p26 showed delayed growth at a low multiplicity of infection. There was also delayed accumulation of the viral immediate early 2 (IE2) protein in the mutant virus, and this correlated with the reduced expression of VCP/p97, which promotes IE2 expression. Infection with mutant virus did not significantly alter ISGylation levels. In transient expression assays, pUL50 induced VCP/p97 loss posttranscriptionally, and this was dependent on the presence of its transmembrane domain. In contrast, UL50-p26 did not destabilize VCP/p97 but, rather, inhibited pUL50-mediated VCP/p97 loss and the associated major IE gene suppression. Both pUL50 and UL50-p26 interacted with VCP/p97, although UL50-p26 did so more weakly than pUL50. UL50-p26 interacted with pUL50, and this interaction was much stronger than the pUL50 self-interaction. Furthermore, UL50-p26 was able to interfere with the pUL50-VCP/p97 interaction. Our study newly identifies UL50-p26 expression during HCMV infection and suggests a regulatory role for UL50-p26 in blocking pUL50-mediated VCP/p97 loss by associating with pUL50.IMPORTANCE Targeting the endoplasmic reticulum (ER) by viral proteins may affect ER-associated protein homeostasis. During human cytomegalovirus (HCMV) infection, pUL50 targets the ER through its transmembrane domain and moves to the inner nuclear membrane (INM) to form the nuclear egress complex (NEC), which facilitates capsid transport from the nucleus to the cytoplasm. Here, we demonstrate that pUL50 induces the loss of valosin-containing protein (VCP/p97), which promotes the expression of viral major immediate early gene products, in a manner dependent on its membrane targeting but that a small isoform of pUL50 is expressed to negatively regulate this pUL50 activity. This study reports a new NEC-independent function of pUL50 and highlights the fine regulation of pUL50 activity by a smaller isoform for efficient viral growth.
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A quantitative nuclear egress assay to investigate the nucleocytoplasmic capsid release of human cytomegalovirus. J Virol Methods 2020; 283:113909. [PMID: 32544419 DOI: 10.1016/j.jviromet.2020.113909] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 06/05/2020] [Accepted: 06/07/2020] [Indexed: 11/21/2022]
Abstract
Nuclear egress is a rate-limiting step of herpesviral replication, restricting the nucleocytoplasmic transport of viral capsids. The process is regulated by two viral nuclear egress proteins (core NEC pUL50-pUL53), which recruit additional cellular and viral proteins. The multicomponent NEC mediates disassembly of the nuclear lamina barrier and the docking of nuclear capsids. The quantitation of nuclear egress has been accomplished by electron microscopic analysis, but is generally hampered by the low number of detectable cytoplasmic capsids. A newly established method for the quantitation of viral nuclear egress improves the characterization of viral mutants, host cell permissiveness and antiviral drug efficacy. In this study, various strains of human cytomegalovirus (HCMV) were used to measure the replication efficiencies in primary human fibroblasts, applying methods of cell fractionation, DNase digestion, sucrose cushions and quantitative PCR. Several stages of optimization led to a reliable quantitative assay that allowed the characterization of viral nuclear egress efficacy. Using this assay, recovery of the nuclear egress of a NEC-defective HCMV mutant was quantitatively assessed by applying an inducible NEC-expressing fibroblast culture for trans-complementation. This novel assay system can be further used to accurately quantitate and characterize the functionality of nuclear egress of HCMV or other herpesviruses.
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Couté Y, Kraut A, Zimmermann C, Büscher N, Hesse AM, Bruley C, De Andrea M, Wangen C, Hahn F, Marschall M, Plachter B. Mass Spectrometry-Based Characterization of the Virion Proteome, Phosphoproteome, and Associated Kinase Activity of Human Cytomegalovirus. Microorganisms 2020; 8:microorganisms8060820. [PMID: 32486127 PMCID: PMC7357008 DOI: 10.3390/microorganisms8060820] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 05/28/2020] [Accepted: 05/28/2020] [Indexed: 12/17/2022] Open
Abstract
The assembly of human cytomegalovirus (HCMV) virions is an orchestrated process that requires, as an essential prerequisite, the complex crosstalk between viral structural proteins. Currently, however, the mechanisms governing the successive steps in the constitution of virion protein complexes remain elusive. Protein phosphorylation is a key regulator determining the sequential changes in the conformation, binding, dynamics, and stability of proteins in the course of multiprotein assembly. In this review, we present a comprehensive map of the HCMV virion proteome, including a refined view on the virion phosphoproteome, based on previous publications supplemented by new results. Thus, a novel dataset of viral and cellular proteins contained in HCMV virions is generated, providing a basis for future analyses of individual phosphorylation steps and sites involved in the orchestrated assembly of HCMV virion-specific multiprotein complexes. Finally, we present the current knowledge on the activity of pUL97, the HCMV-encoded and virion-associated kinase, in phosphorylating viral and host proteins.
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Affiliation(s)
- Yohann Couté
- University Grenoble Alpes, CEA, Inserm, BIG-BGE, 38000 Grenoble, France; (A.K.); (A.-M.H.); (C.B.)
- Correspondence: (Y.C.); (B.P.); Tel.: +33-4-38789461 (Y.C.); +49-6131-179232 (B.P.)
| | - Alexandra Kraut
- University Grenoble Alpes, CEA, Inserm, BIG-BGE, 38000 Grenoble, France; (A.K.); (A.-M.H.); (C.B.)
| | - Christine Zimmermann
- Institute for Virology and Forschungszentrum für Immuntherapie, University Medical Center of the Johannes Gutenberg-University Mainz, Obere Zahlbacher Str. 67, D-55131 Mainz, Germany; (C.Z.); (N.B.)
| | - Nicole Büscher
- Institute for Virology and Forschungszentrum für Immuntherapie, University Medical Center of the Johannes Gutenberg-University Mainz, Obere Zahlbacher Str. 67, D-55131 Mainz, Germany; (C.Z.); (N.B.)
| | - Anne-Marie Hesse
- University Grenoble Alpes, CEA, Inserm, BIG-BGE, 38000 Grenoble, France; (A.K.); (A.-M.H.); (C.B.)
| | - Christophe Bruley
- University Grenoble Alpes, CEA, Inserm, BIG-BGE, 38000 Grenoble, France; (A.K.); (A.-M.H.); (C.B.)
| | - Marco De Andrea
- Department of Public Health and Pediatric Sciences, Turin Medical School, University of Turin, 10126 Turin, and CAAD – Center for Translational Research on Autoimmune and Allergic Disease, Novara Medical School, 28100 Novara, Italy;
| | - Christina Wangen
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (C.W.); (F.H.); (M.M.)
| | - Friedrich Hahn
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (C.W.); (F.H.); (M.M.)
| | - Manfred Marschall
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany; (C.W.); (F.H.); (M.M.)
| | - Bodo Plachter
- Institute for Virology and Forschungszentrum für Immuntherapie, University Medical Center of the Johannes Gutenberg-University Mainz, Obere Zahlbacher Str. 67, D-55131 Mainz, Germany; (C.Z.); (N.B.)
- Correspondence: (Y.C.); (B.P.); Tel.: +33-4-38789461 (Y.C.); +49-6131-179232 (B.P.)
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The Cytomegalovirus Protein Kinase pUL97:Host Interactions, Regulatory Mechanisms and Antiviral Drug Targeting. Microorganisms 2020; 8:microorganisms8040515. [PMID: 32260430 PMCID: PMC7232230 DOI: 10.3390/microorganisms8040515] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 04/02/2020] [Accepted: 04/02/2020] [Indexed: 12/25/2022] Open
Abstract
Human cytomegalovirus (HCMV) expresses a variety of viral regulatory proteins that undergo close interaction with host factors including viral-cellular multiprotein complexes. The HCMV protein kinase pUL97 represents a viral cyclin-dependent kinase ortholog (vCDK) that determines the efficiency of HCMV replication via phosphorylation of viral and cellular substrates. A hierarchy of functional importance of individual pUL97-mediated phosphorylation events has been discussed; however, the most pronounced pUL97-dependent phenotype could be assigned to viral nuclear egress, as illustrated by deletion of the UL97 gene or pharmacological pUL97 inhibition. Despite earlier data pointing to a cyclin-independent functionality, experimental evidence increasingly emphasized the role of pUL97-cyclin complexes. Consequently, the knowledge about pUL97 involvement in host interaction, viral nuclear egress and additional replicative steps led to the postulation of pUL97 as an antiviral target. Indeed, validation experiments in vitro and in vivo confirmed the sustainability of this approach. Consequently, current investigations of pUL97 in antiviral treatment go beyond the known pUL97-mediated ganciclovir prodrug activation and henceforward include pUL97-specific kinase inhibitors. Among a number of interesting small molecules analyzed in experimental and preclinical stages, maribavir is presently investigated in clinical studies and, in the near future, might represent a first kinase inhibitor applied in the field of antiviral therapy.
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Terhune SS, Jung Y, Cataldo KM, Dash RK. Network mechanisms and dysfunction within an integrated computational model of progression through mitosis in the human cell cycle. PLoS Comput Biol 2020; 16:e1007733. [PMID: 32251461 PMCID: PMC7162553 DOI: 10.1371/journal.pcbi.1007733] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 04/16/2020] [Accepted: 02/12/2020] [Indexed: 12/20/2022] Open
Abstract
The cellular protein-protein interaction network that governs cellular proliferation (cell cycle) is highly complex. Here, we have developed a novel computational model of human mitotic cell cycle, integrating diverse cellular mechanisms, for the purpose of generating new hypotheses and predicting new experiments designed to help understand complex diseases. The pathogenic state investigated is infection by a human herpesvirus. The model starts at mitotic entry initiated by the activities of Cyclin-dependent kinase 1 (CDK1) and Polo-like kinase 1 (PLK1), transitions through Anaphase-promoting complex (APC/C) bound to Cell division cycle protein 20 (CDC20), and ends upon mitotic exit mediated by APC/C bound to CDC20 homolog 1 (CDH1). It includes syntheses and multiple mechanisms of degradations of the mitotic proteins. Prior to this work, no such comprehensive model of the human mitotic cell cycle existed. The new model is based on a hybrid framework combining Michaelis-Menten and mass action kinetics for the mitotic interacting reactions. It simulates temporal changes in 12 different mitotic proteins and associated protein complexes in multiple states using 15 interacting reactions and 26 ordinary differential equations. We have defined model parameter values using both quantitative and qualitative data and using parameter values from relevant published models, and we have tested the model to reproduce the cardinal features of human mitosis determined experimentally by numerous laboratories. Like cancer, viruses create dysfunction to support infection. By simulating infection of the human herpesvirus, cytomegalovirus, we hypothesize that virus-mediated disruption of APC/C is necessary to establish a unique mitotic collapse with sustained CDK1 activity, consistent with known mechanisms of virus egress. With the rapid discovery of cellular protein-protein interaction networks and regulatory mechanisms, we anticipate that this model will be highly valuable in helping us to understand the network dynamics and identify potential points of therapeutic interventions.
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Affiliation(s)
- Scott S. Terhune
- Departments of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- Department of Biomedical Engineering, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Yongwoon Jung
- Department of Biomedical Engineering, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Katie M. Cataldo
- Departments of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Ranjan K. Dash
- Department of Biomedical Engineering, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
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Phosphosite Analysis of the Cytomegaloviral mRNA Export Factor pUL69 Reveals Serines with Critical Importance for Recruitment of Cellular Proteins Pin1 and UAP56/URH49. J Virol 2020; 94:JVI.02151-19. [PMID: 31969433 DOI: 10.1128/jvi.02151-19] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Accepted: 01/13/2020] [Indexed: 01/04/2023] Open
Abstract
Human cytomegalovirus (HCMV) encodes the viral mRNA export factor pUL69, which facilitates the cytoplasmic accumulation of mRNA via interaction with the cellular RNA helicase UAP56 or URH49. We reported previously that pUL69 is phosphorylated by cellular CDKs and the viral CDK-like kinase pUL97. Here, we set out to identify phosphorylation sites within pUL69 and to characterize their importance. Mass spectrometry-based phosphosite mapping of pUL69 identified 10 serine/threonine residues as phosphoacceptors. Surprisingly, only a few of these sites localized to the N terminus of pUL69, which could be due to the presence of additional posttranslational modifications, like arginine methylation. As an alternative approach, pUL69 mutants with substitutions of putative phosphosites were analyzed by Phos-tag SDS-PAGE. This demonstrated that serines S46 and S49 serve as targets for phosphorylation by pUL97. Furthermore, we provide evidence that phosphorylation of these serines mediates cis/trans isomerization by the prolyl isomerase Pin1, thus forming a functional Pin1 binding motif. Surprisingly, while abrogation of the Pin1 motif did not affect the replication of recombinant cytomegaloviruses, mutation of serines next to the interaction site for UAP56/URH49 strongly decreased viral replication. This was correlated with a loss of UAP56/URH49 recruitment. Intriguingly, the critical serines S13 and S15 were located within a sequence resembling the UAP56 binding motif (UBM) of cellular mRNA adaptor proteins like REF and UIF. We propose that betaherpesviral mRNA export factors have evolved an extended UAP56/URH49 recognition sequence harboring phosphorylation sites to increase their binding affinities. This may serve as a strategy to successfully compete with cellular mRNA adaptor proteins for binding to UAP56/URH49.IMPORTANCE The multifunctional regulatory protein pUL69 of human cytomegalovirus acts as a viral RNA export factor with a critical role in efficient replication. Here, we identify serine/threonine phosphorylation sites for cellular and viral kinases within pUL69. We demonstrate that the pUL97/CDK phosphosites within alpha-helix 2 of pUL69 are crucial for its cis/trans isomerization by the cellular protein Pin1. Thus, we identified pUL69 as the first HCMV-encoded protein that is phosphorylated by cellular and viral serine/threonine kinases in order to serve as a substrate for Pin1. Furthermore, our study revealed that betaherpesviral mRNA export proteins contain extended binding motifs for the cellular mRNA adaptor proteins UAP56/URH49 harboring phosphorylated serines that are critical for efficient viral replication. Knowledge of the phosphorylation sites of pUL69 and the processes regulated by these posttranslational modifications is important in order to develop antiviral strategies based on a specific interference with pUL69 phosphorylation.
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Patterns of Autologous and Nonautologous Interactions Between Core Nuclear Egress Complex (NEC) Proteins of α-, β- and γ-Herpesviruses. Viruses 2020; 12:v12030303. [PMID: 32168891 PMCID: PMC7150769 DOI: 10.3390/v12030303] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 03/06/2020] [Indexed: 12/12/2022] Open
Abstract
Nuclear egress is a regulated process shared by α-, β- and γ-herpesviruses. The core nuclear egress complex (NEC) is composed of the membrane-anchored protein homologs of human cytomegalovirus (HCMV) pUL50, murine cytomegalovirus (MCMV) pM50, Epstein-Barr virus (EBV) BFRF1 or varicella zoster virus (VZV) Orf24, which interact with the autologous NEC partners pUL53, pM53, BFLF2 or Orf27, respectively. Their recruitment of additional proteins leads to the assembly of a multicomponent NEC, coordinately regulating viral nucleocytoplasmic capsid egress. Here, the functionality of VZV, HCMV, MCMV and EBV core NECs was investigated by coimmunoprecipitation and confocal imaging analyses. Furthermore, a recombinant MCMV, harboring a replacement of ORF M50 by UL50, was analyzed both in vitro and in vivo. In essence, core NEC interactions were strictly limited to autologous NEC pairs and only included one measurable nonautologous interaction between the homologs of HCMV and MCMV. A comparative analysis of MCMV-WT versus MCMV-UL50-infected murine fibroblasts revealed almost identical phenotypes on the levels of protein and genomic replication kinetics. In infected BALB/c mice, virus spread to lung and other organs was found comparable between these viruses, thus stating functional complementarity. In conclusion, our study underlines that herpesviral core NEC proteins are functionally conserved regarding complementarity of core NEC interactions, which were found either virus-specific or restricted within subfamilies.
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Cazorla-Vázquez S, Steingruber M, Marschall M, Engel FB. Human cytomegaloviral multifunctional protein kinase pUL97 impairs zebrafish embryonic development and increases mortality. Sci Rep 2019; 9:7219. [PMID: 31076608 PMCID: PMC6510723 DOI: 10.1038/s41598-019-43649-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 04/26/2019] [Indexed: 12/27/2022] Open
Abstract
Cytomegalovirus is a worldwide-distributed human pathogen, which is the leading cause of congenital virus infection, affecting 0.5 to 2% of live births. To date, it is largely unclear which molecular mechanisms underlie the symptomatic outcomes. This is mainly due to species specificity and limited homology among cytomegalovirus genomes. As it is not possible to infect model organisms with human cytomegalovirus, the aim of this study was to develop a heterologous system allowing in the future the elucidation of the pathological role of individual viral proteins. As a model organism the zebrafish has been chosen due to its ease of manipulation and characterization as well as its large offspring. As cytomegalovirus model protein, pUL97 was characterized because it is multiply involved in virus-host interaction. Here, we show in zebrafish embryos, that (i) pUL97 can be expressed in zebrafish, (ii) increasing pUL97 expression levels quantitatively correlate with both minor and major pathological defects, (iii) pUL97 expression impairs cell cycle progression and induces cell death, (iv) active pUL97, but not an inactive mutant, induces excess mortality, and (v) co-administration of a pUL97 inhibitor reduces embryonic pathology. Collectively, these data indicate the suitability of zebrafish to elucidate the pathological role of human cytomegaloviral proteins.
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Affiliation(s)
- Salvador Cazorla-Vázquez
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Schwabachanlage 12, 91052, Erlangen, Germany
| | - Mirjam Steingruber
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054, Erlangen, Germany
| | - Manfred Marschall
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Schlossgarten 4, 91054, Erlangen, Germany
| | - Felix B Engel
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Schwabachanlage 12, 91052, Erlangen, Germany.
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Steingruber M, Keller L, Socher E, Ferre S, Hesse AM, Couté Y, Hahn F, Büscher N, Plachter B, Sticht H, Marschall M. Cyclins B1, T1, and H differ in their molecular mode of interaction with cytomegalovirus protein kinase pUL97. J Biol Chem 2019; 294:6188-6203. [PMID: 30782840 DOI: 10.1074/jbc.ra118.007049] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 02/08/2019] [Indexed: 12/19/2022] Open
Abstract
Human cytomegalovirus (HCMV) is a common β-herpesvirus causing life-long latent infections. HCMV replication interferes with cell cycle regulation in host cells because the HCMV-encoded cyclin-dependent kinase (CDK) ortholog pUL97 extensively phosphorylates the checkpoint regulator retinoblastoma protein. pUL97 also interacts with cyclins B1, T1, and H, and recent findings have strongly suggested that these interactions influence pUL97 substrate recognition. Interestingly, here we detected profound mechanistic differences among these pUL97-cyclin interactions. Our study revealed the following. (i) pUL97 interacts with cyclins B1 and H in a manner dependent on pUL97 activity and HCMV-specific cyclin modulation, respectively. (ii) The phosphorylated state of both proteins is an important determinant of the pUL97-cyclin B1 interaction. (iii) Activated phospho-Thr-315 cyclin H is up-regulated during HCMV replication. (iv) Thr-315 phosphorylation is independent of intracellular pUL97 or CDK7 activity. (v) pUL97-mediated in vitro phosphorylation is detectable for cyclin B1 but not H. (vi) Mutual transphosphorylation between pUL97 and CDK7 is not detectable, and an MS-based phosphosite analysis indicated that pUL97 might unexpectedly not be phosphorylated in its T-loop. (vii) The binary complexes pUL97-cyclin H and CDK7-cyclin H as well as the ternary complex pUL97-cyclin-H-CDK7 are detectable in an assembly-based CoIP approach. (viii) pUL97 self-interaction can be bridged by the transcriptional cyclins T1 or H but not by the classical cell cycle-regulating B1 cyclin. Combined, our findings unravel a number of cyclin type-specific differences in pUL97 interactions and suggest a multifaceted regulatory impact of cyclins on HCMV replication.
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Affiliation(s)
- Mirjam Steingruber
- From the Institute for Clinical and Molecular Virology, 91054 Erlangen, Germany.
| | - Lena Keller
- From the Institute for Clinical and Molecular Virology, 91054 Erlangen, Germany
| | - Eileen Socher
- Division of Bioinformatics, Institute of Biochemistry Friedrich-Alexander University of Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Sabrina Ferre
- the Université Grenoble Alpes, CEA, Inserm, BIG-BGE, 38000 Grenoble, France
| | - Anne-Marie Hesse
- the Université Grenoble Alpes, CEA, Inserm, BIG-BGE, 38000 Grenoble, France
| | - Yohann Couté
- the Université Grenoble Alpes, CEA, Inserm, BIG-BGE, 38000 Grenoble, France
| | - Friedrich Hahn
- From the Institute for Clinical and Molecular Virology, 91054 Erlangen, Germany
| | - Nicole Büscher
- the Institute for Virology, University Medical Center of the Johannes Gutenberg-University Mainz, 55131 Mainz, Germany
| | - Bodo Plachter
- the Institute for Virology, University Medical Center of the Johannes Gutenberg-University Mainz, 55131 Mainz, Germany
| | - Heinrich Sticht
- Division of Bioinformatics, Institute of Biochemistry Friedrich-Alexander University of Erlangen-Nürnberg, 91054 Erlangen, Germany.
| | - Manfred Marschall
- From the Institute for Clinical and Molecular Virology, 91054 Erlangen, Germany.
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Transmembrane Protein pUL50 of Human Cytomegalovirus Inhibits ISGylation by Downregulating UBE1L. J Virol 2018; 92:JVI.00462-18. [PMID: 29743376 DOI: 10.1128/jvi.00462-18] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 05/04/2018] [Indexed: 02/08/2023] Open
Abstract
Interferon-stimulated gene 15 (ISG15) encodes a ubiquitin-like protein that can be conjugated to proteins via an enzymatic cascade involving the E1, E2, and E3 enzymes. ISG15 expression and protein ISGylation modulate viral infection; however, the viral mechanisms regulating the function of ISG15 and ISGylation are not well understood. We recently showed that ISGylation suppresses the growth of human cytomegalovirus (HCMV) at multiple steps of the virus life cycle and that the virus-encoded pUL26 protein inhibits protein ISGylation. In this study, we demonstrate that the HCMV UL50-encoded transmembrane protein, a component of the nuclear egress complex, also inhibits ISGylation. pUL50 interacted with UBE1L, an E1-activating enzyme for ISGylation, and (to a lesser extent) with ISG15, as did pUL26. However, unlike pUL26, pUL50 caused proteasomal degradation of UBE1L. The UBE1L level induced in human fibroblast cells by interferon beta treatment or virus infection was reduced by pUL50 expression. This activity of pUL50 involved the transmembrane (TM) domain within its C-terminal region, although pUL50 could interact with UBE1L in a manner independent of the TM domain. Consistently, colocalization of pUL50 with UBE1L was observed in cells treated with a proteasome inhibitor. Furthermore, we found that RNF170, an endoplasmic reticulum (ER)-associated ubiquitin E3 ligase, interacted with pUL50 and promoted pUL50-mediated UBE1L degradation via ubiquitination. Our results demonstrate a novel role for the pUL50 transmembrane protein of HCMV in the regulation of protein ISGylation.IMPORTANCE Proteins can be conjugated covalently by ubiquitin or ubiquitin-like proteins, such as SUMO and ISG15. ISG15 is highly induced in viral infection, and ISG15 conjugation, termed ISGylation, plays important regulatory roles in viral growth. Although ISGylation has been shown to negatively affect many viruses, including human cytomegalovirus (HCMV), viral countermeasures that might modulate ISGylation are not well understood. In the present study, we show that the transmembrane protein encoded by HCMV UL50 inhibits ISGylation by causing proteasomal degradation of UBE1L, an E1-activating enzyme for ISGylation. This pUL50 activity requires membrane targeting. In support of this finding, RNF170, an ER-associated ubiquitin E3 ligase, interacts with pUL50 and promotes UL50-mediated UBE1L ubiquitination and degradation. Our results provide the first evidence, to our knowledge, that viruses can regulate ISGylation by directly targeting the ISGylation E1 enzyme.
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Milbradt J, Sonntag E, Wagner S, Strojan H, Wangen C, Lenac Rovis T, Lisnic B, Jonjic S, Sticht H, Britt WJ, Schlötzer-Schrehardt U, Marschall M. Human Cytomegalovirus Nuclear Capsids Associate with the Core Nuclear Egress Complex and the Viral Protein Kinase pUL97. Viruses 2018; 10:v10010035. [PMID: 29342872 PMCID: PMC5795448 DOI: 10.3390/v10010035] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 01/05/2018] [Accepted: 01/10/2018] [Indexed: 02/07/2023] Open
Abstract
The nuclear phase of herpesvirus replication is regulated through the formation of regulatory multi-component protein complexes. Viral genomic replication is followed by nuclear capsid assembly, DNA encapsidation and nuclear egress. The latter has been studied intensely pointing to the formation of a viral core nuclear egress complex (NEC) that recruits a multimeric assembly of viral and cellular factors for the reorganization of the nuclear envelope. To date, the mechanism of the association of human cytomegalovirus (HCMV) capsids with the NEC, which in turn initiates the specific steps of nuclear capsid budding, remains undefined. Here, we provide electron microscopy-based data demonstrating the association of both nuclear capsids and NEC proteins at nuclear lamina budding sites. Specifically, immunogold labelling of the core NEC constituent pUL53 and NEC-associated viral kinase pUL97 suggested an intranuclear NEC-capsid interaction. Staining patterns with phospho-specific lamin A/C antibodies are compatible with earlier postulates of targeted capsid egress at lamina-depleted areas. Important data were provided by co-immunoprecipitation and in vitro kinase analyses using lysates from HCMV-infected cells, nuclear fractions, or infectious virions. Data strongly suggest that nuclear capsids interact with pUL53 and pUL97. Combined, the findings support a refined concept of HCMV nuclear trafficking and NEC-capsid interaction.
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Affiliation(s)
- Jens Milbradt
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg, Erlangen 91054, Germany.
| | - Eric Sonntag
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg, Erlangen 91054, Germany.
| | - Sabrina Wagner
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg, Erlangen 91054, Germany.
| | - Hanife Strojan
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg, Erlangen 91054, Germany.
| | - Christina Wangen
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg, Erlangen 91054, Germany.
| | - Tihana Lenac Rovis
- Department of Histology and Embryology, Faculty of Medicine, University of Rijeka, Rijeka 51000, Croatia.
| | - Berislav Lisnic
- Department of Histology and Embryology, Faculty of Medicine, University of Rijeka, Rijeka 51000, Croatia.
| | - Stipan Jonjic
- Department of Histology and Embryology, Faculty of Medicine, University of Rijeka, Rijeka 51000, Croatia.
| | - Heinrich Sticht
- Division of Bioinformatics, Institute of Biochemistry, Friedrich-Alexander University of Erlangen-Nürnberg, Erlangen 91054, Germany.
| | - William J Britt
- Departments of Pediatrics and Microbiology, School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
| | | | - Manfred Marschall
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg, Erlangen 91054, Germany.
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Bailer SM. Venture from the Interior-Herpesvirus pUL31 Escorts Capsids from Nucleoplasmic Replication Compartments to Sites of Primary Envelopment at the Inner Nuclear Membrane. Cells 2017; 6:cells6040046. [PMID: 29186822 PMCID: PMC5755504 DOI: 10.3390/cells6040046] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 11/21/2017] [Accepted: 11/22/2017] [Indexed: 01/29/2023] Open
Abstract
Herpesviral capsid assembly is initiated in the nucleoplasm of the infected cell. Size constraints require that newly formed viral nucleocapsids leave the nucleus by an evolutionarily conserved vescular transport mechanism called nuclear egress. Mature capsids released from the nucleoplasm are engaged in a membrane-mediated budding process, composed of primary envelopment at the inner nuclear membrane and de-envelopment at the outer nuclear membrane. Once in the cytoplasm, the capsids receive their secondary envelope for maturation into infectious virions. Two viral proteins conserved throughout the herpesvirus family, the integral membrane protein pUL34 and the phosphoprotein pUL31, form the nuclear egress complex required for capsid transport from the infected nucleus to the cytoplasm. Formation of the nuclear egress complex results in budding of membrane vesicles revealing its function as minimal virus-encoded membrane budding and scission machinery. The recent structural analysis unraveled details of the heterodimeric nuclear egress complex and the hexagonal coat it forms at the inside of budding vesicles to drive primary envelopment. With this review, I would like to present the capsid-escort-model where pUL31 associates with capsids in nucleoplasmic replication compartments for escort to sites of primary envelopment thereby coupling capsid maturation and nuclear egress.
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Affiliation(s)
- Susanne M. Bailer
- Institute for Interfacial Engineering and Plasma Technology IGVP, University of Stuttgart, Stuttgart 70174, Germany;
- Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB, Stuttgart 70569, Germany;
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