Endothelial Galectin-1 Binds to Specific Glycans on Nipah Virus Fusion Protein and Inhibits Maturation, Mobility, and Function to Block Syncytia Formation

c Proteolytic activation of the fusion protein of the highly pathogenic Nipah virus (NiV F) is a prerequisite for the production of infectious particles and for virus spread via cell-to-cell fusion. Unlike other paramyxoviral fusion proteins, functional NiV F activation requires endocytosis and pH-dependent cleavage at a monobasic cleavage site by endosomal proteases. Using prototype Vero cells, cathepsin L was previously identified to be a cleavage enzyme. Compared to Vero cells, MDCK cells showed substantially higher F cleavage rates in both NiV-infected and NiV F-transfected cells. Surprisingly, this could not be explained either by an increased F endocytosis rate or by elevated cathepsin L activities. On the contrary, MDCK cells did not display any detectable cathepsin L activity. Though we could confirm cathepsin L to be responsible for F activation in Vero cells, inhibitor studies revealed that in MDCK cells, cathepsin B was required for F-protein cleavage and productive replication of pathogenic NiV. Supporting the idea of an efficient F cleavage in early and recycling endosomes of MDCK cells, endocytosed F proteins and cathepsin B colocalized markedly with the endosomal marker proteins early endosomal antigen 1 (EEA-1), Rab4, and Rab11, while NiV F trafficking through late endosomal compartments was not needed for F activation. In summary, this study shows for the first time that endosomal cathepsin B can play a functional role in the activation of highly pathogenic NiV.

Section: Niv F Cleavage Efficiency Varies Between Different Cell Typessupporting

confidence: 84%

Activation of the Nipah Virus Fusion Protein in MDCK Cells Is Mediated by Cathepsin B within the Endosome-Recycling Compartment

Diederich

Sauerhering

Weis

et al. 2012

“…in other studies (7,23,26), to demonstrate that galectin-1 inhibits influenza virus infection by direct binding to galactosecontaining glycans on the viral envelope, inhibiting viral hemagglutination activity, and blocking viral entry. Moreover, compared to previous in vitro studies on the effects of galectin-1 on viral infection (23,30), our study is the first to show in vivo that galectin-1 can ameliorate influenza virus pathogenesis through direct anti-influenza virus activity.…”

Section: Discussionmentioning

confidence: 97%

“…It was shown that recombinant human galectin-1 inhibits cell fusion and syncytial formation mediated by the fusion (F) envelope glycoprotein of Nipah virus through binding to specific N-glycans in the F glycoprotein (23). Such effects were also demonstrated recently in endothelial and neural cells, the targets of Nipah virus infection (7). However, galectin-1 was also reported to increase HIV-1 infectivity through stabilization of virus attachment to host cells (26,30).…”

mentioning

confidence: 94%

Galectin-1 Binds to Influenza Virus and Ameliorates Influenza Virus Pathogenesis

Yang

Chen

Wang

et al. 2011

111

124

Innate immune response is important for viral clearance during influenza virus infection. Galectin-1, which belongs to S-type lectins, contains a conserved carbohydrate recognition domain that recognizes galactosecontaining oligosaccharides. Since the envelope proteins of influenza virus are highly glycosylated, we studied the role of galectin-1 in influenza virus infection in vitro and in mice. We found that galectin-1 was upregulated in the lungs of mice during influenza virus infection. There was a positive correlation between galectin-1 levels and viral loads during the acute phase of viral infection. Cells treated with recombinant human galectin-1 generated lower viral yields after influenza virus infection. Galectin-1 could directly bind to the envelope glycoproteins of influenza A/WSN/33 virus and inhibit its hemagglutination activity and infectivity. It also bound to different subtypes of influenza A virus with micromolar dissociation constant (K d ) values and protected cells against influenza virus-induced cell death. We used nanoparticle, surface plasmon resonance analysis and transmission electron microscopy to further demonstrate the direct binding of galectin-1 to influenza virus. More importantly, we show for the first time that intranasal treatment of galectin-1 could enhance survival of mice against lethal challenge with influenza virus by reducing viral load, inflammation, and apoptosis in the lung. Furthermore, galectin-1 knockout mice were more susceptible to influenza virus infection than wild-type mice. Collectively, our results indicate that galectin-1 has anti-influenza virus activity by binding to viral surface and inhibiting its infectivity. Thus, galectin-1 may be further explored as a novel therapeutic agent for influenza.

“…Vascular endothelial cells express several galectin family members, including galectin-1 and -9. For example, infection of vascular endothelial cells with Ebola virus results in endothelial cell activation (9) and increased expression of galectin-1 (10,11). Infection of endothelial cells with Dengue virus induces expression of galectin-9 (12), as does binding of double-stranded RNA to Toll-like receptor 3 on endothelial cells (13).…”

mentioning

confidence: 99%

“…Using NiV-F/G-pseudotyped particles, our labs previously demonstrated that galectin-1 produced by endothelial cells can inhibit endothelial cell syncytium formation mediated by NiV-G and NiV-F (11,24). In these studies, galectin-1 reduced NiV-F mediated fusion of endothelial cells by interfering with NiV-F maturation, reducing lateral mobility of NiV-F on the plasma membrane and inhibiting the conformational change in NiV-F triggered by receptor binding to NiV-G that is necessary for cellcell fusion (11).…”

mentioning

confidence: 99%

Timing of Galectin-1 Exposure Differentially Modulates Nipah Virus Entry and Syncytium Formation in Endothelial Cells

Garner

Yun

Pernet

et al. 2015

Self Cite

Nipah virus (NiV) is a deadly emerging enveloped paramyxovirus that primarily targets human endothelial cells. Endothelial cells express the innate immune effector galectin-1 that we have previously shown can bind to specific N-glycans on the NiV envelope fusion glycoprotein (F). NiV-F mediates fusion of infected endothelial cells into syncytia, resulting in endothelial disruption and hemorrhage. Galectin-1 is an endogenous carbohydrate-binding protein that binds to specific glycans on NiV-F to reduce endothelial cell fusion, an effect that may reduce pathophysiologic sequelae of NiV infection. However, galectins play multiple roles in regulating host-pathogen interactions; for example, galectins can promote attachment of HIV to T cells and macrophages and attachment of HSV-1 to keratinocytes but can also inhibit influenza entry into airway epithelial cells. Using live Nipah virus, in the present study, we demonstrate that galectin-1 can enhance NiV attachment to and infection of primary human endothelial cells by bridging glycans on the viral envelope to host cell glycoproteins. In order to exhibit an enhancing effect, galectin-1 must be present during the initial phase of virus attachment; in contrast, addition of galectin-1 postinfection results in reduced production of progeny virus and syncytium formation. Thus, galectin-1 can have dual and opposing effects on NiV infection of human endothelial cells. While various roles for galectin family members in microbial-host interactions have been described, we report opposing effects of the same galectin family member on a specific virus, with the timing of exposure during the viral life cycle determining the outcome. IMPORTANCENipah virus is an emerging pathogen that targets endothelial cells lining blood vessels; the high mortality rate (up to 70%) in Nipah virus infections results from destruction of these cells and resulting catastrophic hemorrhage. Host factors that promote or prevent Nipah virus infection are not well understood. Endogenous human lectins, such as galectin-1, can function as pattern recognition receptors to reduce infection and initiate immune responses; however, lectins can also be exploited by microbes to enhance infection of host cells. We found that galectin-1, which is made by inflamed endothelial cells, can both promote Nipah virus infection of endothelial cells by "bridging" the virus to the cell, as well as reduce production of progeny virus and reduce endothelial cell fusion and damage, depending on timing of galectin-1 exposure. This is the first report of spatiotemporal opposing effects of a host lectin for a virus in one type of host cell. N ipah virus (NiV) is an emerging zoonotic paramyxovirus that targets endothelial and neural cells. Infection with NiV can result in a severe encephalitic or respiratory syndrome with case fatality rates ranging from 40 to 100% in humans (1, 2). Although initial outbreaks involved transmission from bats to pigs and then from pigs to humans, more recent outbreaks have been shown to involve...