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      Different host cell proteases activate the SARS-coronavirus spike-protein for cell–cell and virus–cell fusion

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          Abstract

          Severe acute respiratory syndrome coronavirus (SARS-CoV) poses a considerable threat to human health. Activation of the viral spike (S)-protein by host cell proteases is essential for viral infectivity. However, the cleavage sites in SARS-S and the protease(s) activating SARS-S are incompletely defined. We found that R667 was dispensable for SARS-S-driven virus–cell fusion and for SARS-S-activation by trypsin and cathepsin L in a virus–virus fusion assay. Mutation T760R, which optimizes the minimal furin consensus motif 758-RXXR-762, and furin overexpression augmented SARS-S activity, but did not result in detectable SARS-S cleavage. Finally, SARS-S-driven cell–cell fusion was independent of cathepsin L, a protease essential for virus–cell fusion. Instead, a so far unknown leupeptin-sensitive host cell protease activated cellular SARS-S for fusion with target cells expressing high levels of ACE2. Thus, different host cell proteases activate SARS-S for virus–cell and cell–cell fusion and SARS-S cleavage at R667 and 758-RXXR-762 can be dispensable for SARS-S activation.

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          Most cited references28

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          Identification of a Novel Coronavirus in Patients with Severe Acute Respiratory Syndrome

          The severe acute respiratory syndrome (SARS) has recently been identified as a new clinical entity. SARS is thought to be caused by an unknown infectious agent. Clinical specimens from patients with SARS were searched for unknown viruses with the use of cell cultures and molecular techniques. A novel coronavirus was identified in patients with SARS. The virus was isolated in cell culture, and a sequence 300 nucleotides in length was obtained by a polymerase-chain-reaction (PCR)-based random-amplification procedure. Genetic characterization indicated that the virus is only distantly related to known coronaviruses (identical in 50 to 60 percent of the nucleotide sequence). On the basis of the obtained sequence, conventional and real-time PCR assays for specific and sensitive detection of the novel virus were established. Virus was detected in a variety of clinical specimens from patients with SARS but not in controls. High concentrations of viral RNA of up to 100 million molecules per milliliter were found in sputum. Viral RNA was also detected at extremely low concentrations in plasma during the acute phase and in feces during the late convalescent phase. Infected patients showed seroconversion on the Vero cells in which the virus was isolated. The novel coronavirus might have a role in causing SARS. Copyright 2003 Massachusetts Medical Society
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            A novel coronavirus associated with severe acute respiratory syndrome.

            A worldwide outbreak of severe acute respiratory syndrome (SARS) has been associated with exposures originating from a single ill health care worker from Guangdong Province, China. We conducted studies to identify the etiologic agent of this outbreak. We received clinical specimens from patients in seven countries and tested them, using virus-isolation techniques, electron-microscopical and histologic studies, and molecular and serologic assays, in an attempt to identify a wide range of potential pathogens. None of the previously described respiratory pathogens were consistently identified. However, a novel coronavirus was isolated from patients who met the case definition of SARS. Cytopathological features were noted in Vero E6 cells inoculated with a throat-swab specimen. Electron-microscopical examination revealed ultrastructural features characteristic of coronaviruses. Immunohistochemical and immunofluorescence staining revealed reactivity with group I coronavirus polyclonal antibodies. Consensus coronavirus primers designed to amplify a fragment of the polymerase gene by reverse transcription-polymerase chain reaction (RT-PCR) were used to obtain a sequence that clearly identified the isolate as a unique coronavirus only distantly related to previously sequenced coronaviruses. With specific diagnostic RT-PCR primers we identified several identical nucleotide sequences in 12 patients from several locations, a finding consistent with a point-source outbreak. Indirect fluorescence antibody tests and enzyme-linked immunosorbent assays made with the new isolate have been used to demonstrate a virus-specific serologic response. This virus may never before have circulated in the U.S. population. A novel coronavirus is associated with this outbreak, and the evidence indicates that this virus has an etiologic role in SARS. Because of the death of Dr. Carlo Urbani, we propose that our first isolate be named the Urbani strain of SARS-associated coronavirus. Copyright 2003 Massachusetts Medical Society
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              CD209L (L-SIGN) is a receptor for severe acute respiratory syndrome coronavirus.

              Angiotensin-converting enzyme 2 (ACE2) is a receptor for SARS-CoV, the novel coronavirus that causes severe acute respiratory syndrome [Li, W. Moore, M. J., Vasilieva, N., Sui, J., Wong, S. K., Berne, M. A., Somasundaran, M., Sullivan, J. L., Luzuriaga, K., Greenough, T. C., et al. (2003) Nature 426, 450-454]. We have identified a different human cellular glycoprotein that can serve as an alternative receptor for SARS-CoV. A human lung cDNA library in vesicular stomatitis virus G pseudotyped retrovirus was transduced into Chinese hamster ovary cells, and the cells were sorted for binding of soluble SARS-CoV spike (S) glycoproteins, S(590) and S(1180). Clones of transduced cells that bound SARS-CoV S glycoprotein were inoculated with SARS-CoV, and increases in subgenomic viral RNA from 1-16 h or more were detected by multiplex RT-PCR in four cloned cell lines. Sequencing of the human lung cDNA inserts showed that each of the cloned cell lines contained cDNA that encoded human CD209L, a C-type lectin (also called L-SIGN). When the cDNA encoding CD209L from clone 2.27 was cloned and transfected into Chinese hamster ovary cells, the cells expressed human CD209L glycoprotein and became susceptible to infection with SARS-CoV. Immunohistochemistry showed that CD209L is expressed in human lung in type II alveolar cells and endothelial cells, both potential targets for SARS-CoV. Several other enveloped viruses including Ebola and Sindbis also use CD209L as a portal of entry, and HIV and hepatitis C virus can bind to CD209L on cell membranes but do not use it to mediate virus entry. Our data suggest that the large S glycoprotein of SARS-CoV may use both ACE2 and CD209L in virus infection and pathogenesis.
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                Author and article information

                Contributors
                Journal
                Virology
                Virology
                Virology
                Elsevier Inc.
                0042-6822
                1096-0341
                23 March 2011
                10 May 2011
                23 March 2011
                : 413
                : 2
                : 265-274
                Affiliations
                [a ]Blood Systems Research Institute and Department of Laboratory Medicine, University of California, San Francisco, CA, USA
                [b ]Institute of Virology, Hannover Medical School, 30625 Hannover, Germany
                [c ]Institute for Virology, University Hospital Erlangen, 91054 Erlangen, Germany
                [d ]Nikolaus-Fiebiger-Center, University Hospital Erlangen, 91054 Erlangen, Germany
                [e ]Department of Microbiology, University of Pennsylvania, PA 19104–6076, USA
                [f ]Department of Medical Microbiology and Virology, University of Kiel, 24105 Kiel, Germany
                [g ]German Primate Center, Infection Biology Unit, 37077 Göttingen, Germany
                Author notes
                [* ]Correspondence to: G. Simmons, Blood Systems Research Institute, 270 Masonic Ave, San Francisco, CA, USA. Fax: +1 415 567 5899. gsimmons@ 123456bloodsystems.org
                [** ]Correspondence to: S. Pöhlmann, German Primate Research Center, Kellnerweg 4, 37077 Göttingen, Germany. Fax: + 49 551 3851 184. s.poehlmann@ 123456dpz.eu
                [1]

                G.S., S.B. and I.G. contributed equally to this work.

                Article
                S0042-6822(11)00092-4
                10.1016/j.virol.2011.02.020
                3086175
                21435673
                fa1bff4c-138f-422b-99ab-30f89b9efaff
                Copyright © 2011 Elsevier Inc. All rights reserved.

                Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.

                History
                : 3 December 2010
                : 21 December 2010
                : 24 February 2011
                Categories
                Article

                Microbiology & Virology
                sars coronavirus,spike protein,proteolytic cleavage,cathepsin l,furin
                Microbiology & Virology
                sars coronavirus, spike protein, proteolytic cleavage, cathepsin l, furin

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