Hahn, Alexander S.

[["dc.bibliographiccitation.artnumber","e00002-21"],["dc.bibliographiccitation.issue","9"],["dc.bibliographiccitation.journal","Journal of Virology"],["dc.bibliographiccitation.volume","95"],["dc.contributor.author","Hörnich, Bojan F."],["dc.contributor.author","Großkopf, Anna K."],["dc.contributor.author","Schlagowski, Sarah"],["dc.contributor.author","Tenbusch, Matthias"],["dc.contributor.author","Kleine-Weber, Hannah"],["dc.contributor.author","Neipel, Frank"],["dc.contributor.author","Stahl-Hennig, Christiane"],["dc.contributor.author","Hahn, Alexander S."],["dc.contributor.editor","Gallagher, Tom"],["dc.date.accessioned","2022-10-06T13:25:30Z"],["dc.date.available","2022-10-06T13:25:30Z"],["dc.date.issued","2021"],["dc.description.abstract","Cell-cell fusion allows viruses to infect neighboring cells without the need to produce free virus and contributes to tissue damage by creating virus-infected syncytia. Our results demonstrate that the S2′ cleavage site is essential for activation by TMPRSS2 and unravel important differences between SARS-CoV and SARS-CoV-2, among those, greater dependence of SARS-CoV-2 on ACE2 expression and activation by metalloproteases for cell-cell fusion."],["dc.description.abstract","ABSTRACT\n Severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) infects cells through interaction of its spike protein (SARS2-S) with angiotensin-converting enzyme 2 (ACE2) and activation by proteases, in particular transmembrane protease serine 2 (TMPRSS2). Viruses can also spread through fusion of infected with uninfected cells. We compared the requirements of ACE2 expression, proteolytic activation, and sensitivity to inhibitors for SARS2-S-mediated and SARS-CoV-S (SARS1-S)-mediated cell-cell fusion. SARS2-S-driven fusion was moderately increased by TMPRSS2 and strongly by ACE2, while SARS1-S-driven fusion was strongly increased by TMPRSS2 and less so by ACE2 expression. In contrast to that of SARS1-S, SARS2-S-mediated cell-cell fusion was efficiently activated by batimastat-sensitive metalloproteases. Mutation of the S1/S2 proteolytic cleavage site reduced effector cell-target cell fusion when ACE2 or TMPRSS2 was limiting and rendered SARS2-S-driven cell-cell fusion more dependent on TMPRSS2. When both ACE2 and TMPRSS2 were abundant, initial target cell-effector cell fusion was unaltered compared to that of wild-type (wt) SARS2-S, but syncytia remained smaller. Mutation of the S2 cleavage (S2′) site specifically abrogated activation by TMPRSS2 for both cell-cell fusion and SARS2-S-driven pseudoparticle entry but still allowed for activation by metalloproteases for cell-cell fusion and by cathepsins for particle entry. Finally, we found that the TMPRSS2 inhibitor bromhexine, unlike the inhibitor camostat, was unable to reduce TMPRSS2-activated cell-cell fusion by SARS1-S and SARS2-S. Paradoxically, bromhexine enhanced cell-cell fusion in the presence of TMPRSS2, while its metabolite ambroxol exhibited inhibitory activity under some conditions. On Calu-3 lung cells, ambroxol weakly inhibited SARS2-S-driven lentiviral pseudoparticle entry, and both substances exhibited a dose-dependent trend toward weak inhibition of authentic SARS-CoV-2.\n \n IMPORTANCE\n Cell-cell fusion allows viruses to infect neighboring cells without the need to produce free virus and contributes to tissue damage by creating virus-infected syncytia. Our results demonstrate that the S2′ cleavage site is essential for activation by TMPRSS2 and unravel important differences between SARS-CoV and SARS-CoV-2, among those, greater dependence of SARS-CoV-2 on ACE2 expression and activation by metalloproteases for cell-cell fusion. Bromhexine, reportedly an inhibitor of TMPRSS2, is currently being tested in clinical trials against coronavirus disease 2019. Our results indicate that bromhexine enhances fusion under some conditions. We therefore caution against the use of bromhexine in high dosages until its effects on SARS-CoV-2 spike activation are better understood. The related compound ambroxol, which similarly to bromhexine is clinically used as an expectorant, did not exhibit activating effects on cell-cell fusion. Both compounds exhibited weak inhibitory activity against SARS-CoV-2 infection at high concentrations, which might be clinically attainable for ambroxol."],["dc.description.sponsorship"," Deutsche Forschungsgemeinschaft https://doi.org/10.13039/501100001659"],["dc.description.sponsorship"," Wilhelm Sander-Stiftung https://doi.org/10.13039/100008672"],["dc.identifier.doi","10.1128/JVI.00002-21"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/114857"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-602"],["dc.relation.eissn","1098-5514"],["dc.relation.issn","0022-538X"],["dc.relation.orgunit","Deutsches Primatenzentrum"],["dc.rights.uri","https://doi.org/10.1128/ASMCopyrightv2"],["dc.title","SARS-CoV-2 and SARS-CoV Spike-Mediated Cell-Cell Fusion Differ in Their Requirements for Receptor Expression and Proteolytic Activation"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","e1008979"],["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","PLOS Pathogens"],["dc.bibliographiccitation.volume","17"],["dc.contributor.author","Großkopf, Anna K."],["dc.contributor.author","Schlagowski, Sarah"],["dc.contributor.author","Fricke, Thomas"],["dc.contributor.author","Ensser, Armin"],["dc.contributor.author","Desrosiers, Ronald C."],["dc.contributor.author","Hahn, Alexander S."],["dc.contributor.editor","Zheng, Zhi-Ming"],["dc.date.accessioned","2022-10-06T13:26:22Z"],["dc.date.available","2022-10-06T13:26:22Z"],["dc.date.issued","2021"],["dc.description.abstract","The rhesus monkey rhadinovirus (RRV), a γ2-herpesvirus of rhesus macaques, shares many biological features with the human pathogenic Kaposi’s sarcoma-associated herpesvirus (KSHV). Both viruses, as well as the more distantly related Epstein-Barr virus, engage cellular receptors from the Eph family of receptor tyrosine kinases (Ephs). However, the importance of the Eph interaction for RRV entry varies between cell types suggesting the existence of Eph-independent entry pathways. We therefore aimed to identify additional cellular receptors for RRV by affinity enrichment and mass spectrometry. We identified an additional receptor family, the Plexin domain containing proteins 1 and 2 (Plxdc1/2) that bind the RRV gH/gL glycoprotein complex. Preincubation of RRV with soluble Plxdc2 decoy receptor reduced infection by ~60%, while overexpression of Plxdc1 and 2 dramatically enhanced RRV susceptibility and cell-cell fusion of otherwise marginally permissive Raji cells. While the Plxdc2 interaction is conserved between two RRV strains, 26–95 and 17577, Plxdc1 specifically interacts with RRV 26–95 gH. The Plxdc interaction is mediated by a short motif at the N-terminus of RRV gH that is partially conserved between isolate 26–95 and isolate 17577, but absent in KSHV gH. Mutation of this motif abrogated the interaction with Plxdc1/2 and reduced RRV infection in a cell type-specific manner. Taken together, our findings characterize Plxdc1/2 as novel interaction partners and entry receptors for RRV and support the concept of the N-terminal domain of the gammaherpesviral gH/gL complex as a multifunctional receptor-binding domain. Further, Plxdc1/2 usage defines an important biological difference between KSHV and RRV."],["dc.description.sponsorship"," Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659"],["dc.description.sponsorship"," Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659"],["dc.description.sponsorship"," Wilhelm Sander-Stiftung http://dx.doi.org/10.13039/100008672"],["dc.description.sponsorship","Interdisciplinary Center for Clinical Research Erlangen"],["dc.description.sponsorship"," Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659"],["dc.description.sponsorship"," National Institutes of Health http://dx.doi.org/10.13039/100000002"],["dc.description.sponsorship"," Foundation for the National Institutes of Health http://dx.doi.org/10.13039/100000009"],["dc.identifier.doi","10.1371/journal.ppat.1008979"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/115069"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-602"],["dc.relation.eissn","1553-7374"],["dc.relation.orgunit","Deutsches Primatenzentrum"],["dc.rights.uri","http://creativecommons.org/licenses/by/4.0/"],["dc.title","Plxdc family members are novel receptors for the rhesus monkey rhadinovirus (RRV)"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","e1006912"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","PLoS Pathogens"],["dc.bibliographiccitation.volume","14"],["dc.contributor.author","Großkopf, Anna K."],["dc.contributor.author","Ensser, Armin"],["dc.contributor.author","Neipel, Frank"],["dc.contributor.author","Jungnickl, Doris"],["dc.contributor.author","Schlagowski, Sarah"],["dc.contributor.author","Desrosiers, Ronald C."],["dc.contributor.author","Hahn, Alexander S."],["dc.contributor.editor","Hutt-Fletcher, Lindsey"],["dc.date.accessioned","2022-10-06T13:26:22Z"],["dc.date.available","2022-10-06T13:26:22Z"],["dc.date.issued","2018"],["dc.description.sponsorship"," Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659"],["dc.description.sponsorship","Interdisciplinary Center for Clinical Research Erlangen (IZKF)"],["dc.description.sponsorship"," Wilhelm Sander-Stiftung http://dx.doi.org/10.13039/100008672"],["dc.description.sponsorship"," Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659"],["dc.description.sponsorship","Interdisciplinary Center for Clinical Research Erlangen (IZKF)"],["dc.description.sponsorship"," Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659"],["dc.description.sponsorship"," Deutsches Primatenzentrum http://dx.doi.org/10.13039/501100004938"],["dc.description.sponsorship"," National Institutes of Health http://dx.doi.org/10.13039/100000002"],["dc.identifier.doi","10.1371/journal.ppat.1006912"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/115068"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-602"],["dc.relation.eissn","1553-7374"],["dc.relation.orgunit","Deutsches Primatenzentrum"],["dc.rights.uri","http://creativecommons.org/licenses/by/4.0/"],["dc.title","A conserved Eph family receptor-binding motif on the gH/gL complex of Kaposi’s sarcoma-associated herpesvirus and rhesus monkey rhadinovirus"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","e02113-21"],["dc.bibliographiccitation.issue","6"],["dc.bibliographiccitation.journal","mBio"],["dc.bibliographiccitation.volume","12"],["dc.contributor.author","Hörnich, Bojan F."],["dc.contributor.author","Großkopf, Anna K."],["dc.contributor.author","Dcosta, Candice J."],["dc.contributor.author","Schlagowski, Sarah"],["dc.contributor.author","Hahn, Alexander S."],["dc.contributor.editor","Palese, Peter"],["dc.date.accessioned","2022-10-06T13:25:47Z"],["dc.date.available","2022-10-06T13:25:47Z"],["dc.date.issued","2021"],["dc.description.abstract","IFITM proteins are the first line of defense against infection by many pathogens and may also have therapeutic importance, as they, among other effectors, mediate the antiviral effect of interferons. Neither their function against herpesviruses nor their mechanism of action is well understood."],["dc.description.abstract","ABSTRACT\n The interferon-induced transmembrane proteins (IFITMs) are broad-spectrum antiviral proteins that inhibit the entry of enveloped viruses. We analyzed the effect of IFITMs on the gamma-2 herpesviruses Kaposi’s sarcoma-associated herpesvirus (KSHV) and the closely related rhesus monkey rhadinovirus (RRV). We used CRISPR/Cas9-mediated gene knockout to generate A549 cells, human foreskin fibroblasts (HFF), and human umbilical vein endothelial cells (HUVEC) with combined IFITM1/2/3 knockout and identified IFITMs as cell-dependent inhibitors of KSHV and RRV infection in A549 cells and HFF but not HUVEC. IFITM overexpression revealed IFITM1 as the relevant IFITM that inhibits KSHV and RRV infection. Fluorescent KSHV particles did not pronouncedly colocalize with IFITM-positive compartments. However, we found that KSHV and RRV glycoprotein-mediated cell-cell fusion is enhanced upon IFITM1/2/3 knockout. Taken together, we identified IFITM1 as a cell-dependent restriction factor of KSHV and RRV that acts at the level of membrane fusion. Of note, our results indicate that recombinant IFITM overexpression may lead to results that are not representative for the situation at endogenous levels. Strikingly, we observed that the endotheliotropic KSHV circumvents IFITM-mediated restriction in HUVEC despite high IFITM expression, while influenza A virus (IAV) glycoprotein-driven entry into HUVEC is potently restricted by IFITMs even in the absence of interferon. Mechanistically, we found that KSHV colocalizes less with IFITM1 and IFITM2 in HUVEC than in A549 cells immediately after attachment, potentially contributing to the observed difference in restriction.\n \n IMPORTANCE\n IFITM proteins are the first line of defense against infection by many pathogens and may also have therapeutic importance, as they, among other effectors, mediate the antiviral effect of interferons. Neither their function against herpesviruses nor their mechanism of action is well understood. We report here that in some cells but not in, for example, primary umbilical vein endothelial cells, IFITM1 restricts KSHV and RRV and that, mechanistically, this is likely effected by reducing the fusogenicity of the cell membrane. Further, we demonstrate potent inhibition of IAV glycoprotein-driven infection of cells of extrapulmonary origin by high constitutive IFITM expression."],["dc.description.sponsorship"," Deutsche Forschungsgemeinschaft https://doi.org/10.13039/501100001659"],["dc.description.sponsorship"," Wilhelm Sander-Stiftung https://doi.org/10.13039/100008672"],["dc.identifier.doi","10.1128/mBio.02113-21"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/114913"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-602"],["dc.relation.eissn","2150-7511"],["dc.relation.orgunit","Deutsches Primatenzentrum"],["dc.rights.uri","https://creativecommons.org/licenses/by/4.0/"],["dc.title","Interferon-Induced Transmembrane Proteins Inhibit Infection by the Kaposi’s Sarcoma-Associated Herpesvirus and the Related Rhesus Monkey Rhadinovirus in a Cell-Specific Manner"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","e00064-19"],["dc.bibliographiccitation.issue","15"],["dc.bibliographiccitation.journal","Journal of Virology"],["dc.bibliographiccitation.volume","93"],["dc.contributor.author","Großkopf, Anna K."],["dc.contributor.author","Schlagowski, Sarah"],["dc.contributor.author","Hörnich, Bojan F."],["dc.contributor.author","Fricke, Thomas"],["dc.contributor.author","Desrosiers, Ronald C."],["dc.contributor.author","Hahn, Alexander S."],["dc.contributor.editor","Jung, Jae U."],["dc.date.accessioned","2022-10-06T13:25:31Z"],["dc.date.available","2022-10-06T13:25:31Z"],["dc.date.issued","2019"],["dc.description.abstract","Infection of B cells is relevant for two KSHV-associated malignancies, the plasmablastic variant of multicentric Castleman’s disease and PEL. Therefore, elucidating the process of B cell infection is important for the understanding of KSHV pathogenesis. While the high-affinity receptor for the gH/gL glycoprotein complex, EphA2, has been shown to function as an entry receptor for various types of adherent cells, the gH/gL complex can also interact with other Eph receptor tyrosine kinases with lower avidity. We analyzed the Eph interactions required for infection of BJAB cells, a model for B cell infection by KSHV. We identified EphA7 as the principal Eph receptor for infection of BJAB cells by KSHV and the related rhesus monkey rhadinovirus. While two analyzed PEL cell lines exhibited high EphA2 and low EphA7 expression, a third PEL cell line, BCBL-1, showed high EphA7 and low EphA2 expression, indicating a possible relevance for KSHV pathology."],["dc.description.abstract","ABSTRACT\n Kaposi’s sarcoma-associated herpesvirus (KSHV) is the causative agent of Kaposi’s sarcoma and is associated with two B cell malignancies, primary effusion lymphoma (PEL) and the plasmablastic variant of multicentric Castleman’s disease. On several adherent cell types, EphA2 functions as a cellular receptor for the gH/gL glycoprotein complex of KSHV. KSHV gH/gL also has previously been found to interact weakly with other members of the Eph family of receptor tyrosine kinases (Ephs), and other A-type Ephs have been shown to be able to compensate for the absence of EphA2 using overexpression systems. However, whether these interactions are of functional consequence at endogenous protein levels has remained unclear so far. Here, we demonstrate for the first time that endogenously expressed EphA7 in BJAB B cells is critical for the cell-to-cell transmission of KSHV from producer iSLK cells to BJAB target cells. The BJAB lymphoblastoid cell line often serves as a model for B cell infection and expresses only low levels of all Eph family receptors other than EphA7. Endogenous EphA7 could be precipitated from the cellular lysate of BJAB cells using recombinant gH/gL, and knockout of EphA7 significantly reduced transmission of KSHV into BJAB target cells. Knockout of EphA5, the second most expressed A-type Eph in BJAB cells, had a similar, although less pronounced, effect on KSHV infection. Receptor function of EphA7 was conserved for cell-free infection by the related rhesus monkey rhadinovirus (RRV), which is relatively even more dependent on EphA7 for infection of BJAB cells.\n \n IMPORTANCE\n Infection of B cells is relevant for two KSHV-associated malignancies, the plasmablastic variant of multicentric Castleman’s disease and PEL. Therefore, elucidating the process of B cell infection is important for the understanding of KSHV pathogenesis. While the high-affinity receptor for the gH/gL glycoprotein complex, EphA2, has been shown to function as an entry receptor for various types of adherent cells, the gH/gL complex can also interact with other Eph receptor tyrosine kinases with lower avidity. We analyzed the Eph interactions required for infection of BJAB cells, a model for B cell infection by KSHV. We identified EphA7 as the principal Eph receptor for infection of BJAB cells by KSHV and the related rhesus monkey rhadinovirus. While two analyzed PEL cell lines exhibited high EphA2 and low EphA7 expression, a third PEL cell line, BCBL-1, showed high EphA7 and low EphA2 expression, indicating a possible relevance for KSHV pathology."],["dc.description.sponsorship"," HHS | National Institutes of Health https://doi.org/10.13039/100000002"],["dc.description.sponsorship"," Deutsche Forschungsgemeinschaft https://doi.org/10.13039/501100001659"],["dc.identifier.doi","10.1128/JVI.00064-19"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/114859"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-602"],["dc.relation.eissn","1098-5514"],["dc.relation.issn","0022-538X"],["dc.relation.orgunit","Deutsches Primatenzentrum"],["dc.rights.uri","https://journals.asm.org/non-commercial-tdm-license"],["dc.title","EphA7 Functions as Receptor on BJAB Cells for Cell-to-Cell Transmission of the Kaposi's Sarcoma-Associated Herpesvirus and for Cell-Free Infection by the Related Rhesus Monkey Rhadinovirus"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]