scholarly journals Cell Fusion and Syncytium Formation in Betaherpesvirus Infection

Viruses ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1973
Author(s):  
Jiajia Tang ◽  
Giada Frascaroli ◽  
Xuan Zhou ◽  
Jan Knickmann ◽  
Wolfram Brune
Keyword(s):  
Cell Fusion ◽  
Neutralizing Antibodies ◽  
Plasma Membranes ◽  
Cancer Metastasis ◽  
Syncytium Formation ◽  
Tissue Growth ◽  
Viral Envelope ◽  
Cell Cell

Cell–cell fusion is a fundamental and complex process that occurs during reproduction, organ and tissue growth, cancer metastasis, immune response, and infection. All enveloped viruses express one or more proteins that drive the fusion of the viral envelope with cellular membranes. The same proteins can mediate the fusion of the plasma membranes of adjacent cells, leading to the formation of multinucleated syncytia. While cell–cell fusion triggered by alpha- and gammaherpesviruses is well-studied, much less is known about the fusogenic potential of betaherpesviruses such as human cytomegalovirus (HCMV) and human herpesviruses 6 and 7 (HHV-6 and HHV-7). These are slow-growing viruses that are highly prevalent in the human population and associated with several diseases, particularly in individuals with an immature or impaired immune system such as fetuses and transplant recipients. While HHV-6 and HHV-7 are strictly lymphotropic, HCMV infects a very broad range of cell types including epithelial, endothelial, mesenchymal, and myeloid cells. Syncytia have been observed occasionally for all three betaherpesviruses, both during in vitro and in vivo infection. Since cell–cell fusion may allow efficient spread to neighboring cells without exposure to neutralizing antibodies and other host immune factors, viral-induced syncytia may be important for viral dissemination, long-term persistence, and pathogenicity. In this review, we provide an overview of the viral and cellular factors and mechanisms identified so far in the process of cell–cell fusion induced by betaherpesviruses and discuss the possible consequences for cellular dysfunction and pathogenesis.

scholarly journals Mechanical stress impairs pheromone signaling via Pkc1-mediated regulation of the MAPK scaffold Ste5

2019 ◽  
Vol 218 (9) ◽  
pp. 3117-3133 ◽  
Author(s):  
Frank van Drogen ◽  
Ranjan Mishra ◽  
Fabian Rudolf ◽  
Michal J. Walczak ◽  
Sung Sik Lee ◽  
...  
Keyword(s):  
Mechanical Stress ◽  
Cell Fusion ◽  
Polarized Growth ◽  
Conserved Residues ◽  
Cellular Processes ◽  
Pheromone Signaling ◽  
Stress Signals ◽  
Cell Cell

Cells continuously adapt cellular processes by integrating external and internal signals. In yeast, multiple stress signals regulate pheromone signaling to prevent mating under unfavorable conditions. However, the underlying crosstalk mechanisms remain poorly understood. Here, we show that mechanical stress activates Pkc1, which prevents lysis of pheromone-treated cells by inhibiting polarized growth. In vitro Pkc1 phosphorylates conserved residues within the RING-H2 domains of the scaffold proteins Far1 and Ste5, which are also phosphorylated in vivo. Interestingly, Pkc1 triggers dispersal of Ste5 from mating projections upon mechanically induced stress and during cell–cell fusion, leading to inhibition of the MAPK Fus3. Indeed, RING phosphorylation interferes with Ste5 membrane association by preventing binding to the receptor-linked Gβγ protein. Cells expressing nonphosphorylatable Ste5 undergo increased lysis upon mechanical stress and exhibit defects in cell–cell fusion during mating, which is exacerbated by simultaneous expression of nonphosphorylatable Far1. These results uncover a mechanical stress–triggered crosstalk mechanism modulating pheromone signaling, polarized growth, and cell–cell fusion during mating.

scholarly journals TR1.3 Viral Pathogenesis and Syncytium Formation Are Linked to Env-Gag Cooperation

2007 ◽  
Vol 81 (19) ◽  
pp. 10777-10785 ◽  
Author(s):  
Samuel L. Murphy ◽  
Glen N. Gaulton
Keyword(s):  
Cell Fusion ◽  
Leukemia Virus ◽  
Syncytium Formation ◽  
In Vitro Assays ◽  
Functional Requirements ◽  
Fusion Inhibition ◽  
Capillary Endothelial Cells ◽  
Nih 3T3

ABSTRACT Infection with murine leukemia virus (MLV) TR1.3 or the related molecular construct W102G causes severe neuropathology in vivo. Infection is causally linked to the development of extensive syncytia in brain capillary endothelial cells (BCEC). These viruses also induce cell fusion of murine cell lines, such as SC-1 and NIH 3T3, which are otherwise resistant to MLV-induced syncytium formation. Although the virulence of these viruses maps within the env gene, the mechanism of fusion enhancement is not fully determined. To this end, we examined the capacity of the syncytium-inducing (SI) TR1.3 and W102G MLVs to overcome the fusion inhibitory activity inherent in the full-length Env cytoplasmic tail. These studies showed that the TR1.3 and W102G Envs did not induce premature cleavage of p2E, nor did they override p2E fusion inhibition. Indeed, in the presence of mutations that disrupt p2E function, the TR1.3 and W102G Envs significantly increased the extent of cell fusion compared to that with the non-syncytium-inducing MLV FB29. Surprisingly, we also observed that TR1.3 and W102G Envs failed to elicit syncytium formation in these in vitro assays. Coexpression of gag-pol with env restored syncytium formation, and accordingly, mutations within gag-pol were used to examine the minimal functional requirements for the SI phenotype. The results indicate that both gag-dependent particle budding and cleavage of p2E are required to activate the SI phenotype of TR1.3 and W102G viruses. Collectively, these data suggest that the TR1.3 and W102G viruses induce cell fusion by the fusion-from-without pathway.

scholarly journals CD13 is a critical regulator of cell–cell fusion in osteoclastogenesis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mallika Ghosh ◽  
Tomislav Kelava ◽  
Ivana Vrhovac Madunic ◽  
Ivo Kalajzic ◽  
Linda H. Shapiro
Keyword(s):  
Bone Marrow ◽  
Cell Fusion ◽  
Regulatory Proteins ◽  
Cytoskeletal Organization ◽  
Receptor Endocytosis ◽  
The Stability ◽  
Deficient Mice ◽  
Cell Cell

AbstractThe transmembrane aminopeptidase CD13 is highly expressed in cells of the myeloid lineage, regulates dynamin-dependent receptor endocytosis and recycling and is a necessary component of actin cytoskeletal organization. Here, we show that CD13-deficient mice present a low bone density phenotype with increased numbers of osteoclasts per bone surface, but display a normal distribution of osteoclast progenitor populations in the bone marrow and periphery. In addition, the bone formation and mineral apposition rates are similar between genotypes, indicating a defect in osteoclast-specific function in vivo. Lack of CD13 led to exaggerated in vitro osteoclastogenesis as indicated by significantly enhanced fusion of bone marrow-derived multinucleated osteoclasts in the presence of M-CSF and RANKL, resulting in abnormally large cells containing remarkably high numbers of nuclei. Mechanistically, while expression levels of the fusion-regulatory proteins dynamin and DC-STAMP1 must be downregulated for fusion to proceed, these are aberrantly sustained at high levels even in CD13-deficient mature multi-nucleated osteoclasts. Further, the stability of fusion-promoting proteins is maintained in the absence of CD13, implicating CD13 in protein turnover mechanisms. Together, we conclude that CD13 may regulate cell–cell fusion by controlling the expression and localization of key fusion regulatory proteins that are critical for osteoclast fusion.

scholarly journals CD13 is a Critical Regulator of Cell-cell Fusion in Osteoclastogenesis

2020 ◽  
Author(s):  
Mallika Ghosh ◽  
Ivo Kalajzic ◽  
Hector Leonardo Aguila ◽  
Linda H Shapiro
Keyword(s):  
Bone Marrow ◽  
Bone Formation ◽  
Progenitor Cells ◽  
Cell Fusion ◽  
Formation Rate ◽  
Giant Cells ◽  
Bone Formation Rate ◽  
Cell Cell

AbstractIn vertebrates, bone formation is dynamically controlled by the activity of two specialized cell types: the bone-generating osteoblasts and bone-degrading osteoclasts. Osteoblasts produce the soluble receptor activator of NFκB ligand (RANKL) that binds to its receptor RANK on the surface of osteoclast precursor cells to promote osteoclastogenesis, a process that involves cell-cell fusion and assembly of molecular machinery to ultimately degrade the bone. CD13 is a transmembrane aminopeptidase that is highly expressed in cells of myeloid lineage has been shown to regulate dynamin-dependent receptor endocytosis and recycling and is a necessary component of actin cytoskeletal organization. In the present study, we show that CD13-deficient mice display a normal distribution of osteoclast progenitor populations in the bone marrow, but present a low bone density phenotype. Further, the endosteal bone formation rate is similar between genotypes, indicating a defect in osteoclast-specific function in vivo. Loss of CD13 led to exaggerated in vitro osteoclastogenesis as indicated by significantly enhanced fusion of bone marrow-derived multinucleated osteoclasts in the presence of M-CSF and RANKL, resulting in abnormally large cells with remarkably high numbers of nuclei with a concomitant increase in bone resorption activity. Similarly, we also observed increased formation of multinucleated giant cells (MGC) in CD13KO bone marrow progenitor cells stimulated with IL-4 and IL-13, suggesting that CD13 may regulate cell-cell fusion events via a common pathway, independent of RANKL signaling. Mechanistically, while expression levels of the fusion-regulatory proteins dynamin and DC-STAMP are normally downregulated as fusion progresses in fusion-competent mononucleated progenitor cells, in the absence of CD13 they are uniformly sustained at high levels, even in mature multi-nucleated osteoclasts. Taken together, we conclude that CD13 may regulate cell-cell fusion by controlling expression and localization of key fusion proteins that are critical for both osteoclast and MGC fusion.

scholarly journals ARHGEF18/p114RhoGEF coordinates PKA/CREB signaling and actomyosin remodeling to drive trophoblast cell-cell fusion during placenta morphogenesis

2020 ◽  
Author(s):  
Robert Beal ◽  
Ana Alonso-Carriazo Fernandez ◽  
Dimitris K. Grammatopoulos ◽  
Karl Matter ◽  
Maria S. Balda
Keyword(s):  
Gene Expression ◽  
Cell Fusion ◽  
Rho Gtpases ◽  
Rho Gtpase ◽  
Trophoblast Cell ◽  
Cell Junctions ◽  
Nucleotide Exchange ◽  
Cell Cell

SUMMARYCoordination of cell-cell adhesion, actomyosin dynamics and gene expression is crucial for morphogenetic processes underlying tissue and organ development. Rho GTPases are main regulators of the cytoskeleton and adhesion. They are activated by guanine nucleotide exchange factors in a spatially and temporally controlled manner. However, the roles of these Rho GTPase activators during complex developmental processes are still poorly understood. ARHGEF18/p114RhoGEF is a tight junction-associated RhoA activator that forms complexes with myosin II, and regulates actomyosin contractility. Here we show that p114RhoGEF/ ARHGEF18 is required for mouse syncytiotrophoblast differentiation and placenta development. In vitro and in vivo experiments identify that p114RhoGEF controls expression of AKAP12, a protein regulating PKA signalling, and is required for PKA-induced actomyosin remodelling, CREB-driven gene expression of proteins required for trophoblast differentiation, and, hence, trophoblast cell-cell fusion. Our data thus indicate that p114RhoGEF links actomyosin dynamics and cell-cell junctions to PKA/CREB signalling, gene expression and cell-cell fusion.

scholarly journals Anti-Glycoprotein H Antibody Impairs the Pathogenicity of Varicella-Zoster Virus in Skin Xenografts in the SCID Mouse Model

2009 ◽  
Vol 84 (1) ◽  
pp. 141-152 ◽  
Author(s):  
Susan E. Vleck ◽  
Stefan L. Oliver ◽  
Mike Reichelt ◽  
Jaya Rajamani ◽  
Leigh Zerboni ◽  
...  
Keyword(s):  
Varicella Zoster Virus ◽  
Neutralizing Antibodies ◽  
Plasma Membranes ◽  
Virus Entry ◽  
Varicella Zoster ◽  
Virus Particles ◽  
Early Endosomes ◽  
Glycoprotein H

ABSTRACT Varicella-zoster virus (VZV) infection is usually mild in healthy individuals but can cause severe disease in immunocompromised patients. Prophylaxis with varicella-zoster immunoglobulin can reduce the severity of VZV if given shortly after exposure. Glycoprotein H (gH) is a highly conserved herpesvirus protein with functions in virus entry and cell-cell spread and is a target of neutralizing antibodies. The anti-gH monoclonal antibody (MAb) 206 neutralizes VZV in vitro. To determine the requirement for gH in VZV pathogenesis in vivo, MAb 206 was administered to SCID mice with human skin xenografts inoculated with VZV. Anti-gH antibody given at 6 h postinfection significantly reduced the frequency of skin xenograft infection by 42%. Virus titers, genome copies, and lesion size were decreased in xenografts that became infected. In contrast, administering anti-gH antibody at 4 days postinfection suppressed VZV replication but did not reduce the frequency of infection. The neutralizing anti-gH MAb 206 blocked virus entry, cell fusion, or both in skin in vivo. In vitro, MAb 206 bound to plasma membranes and to surface virus particles. Antibody was internalized into vacuoles within infected cells, associated with intracellular virus particles, and colocalized with markers for early endosomes and multivesicular bodies but not the trans-Golgi network. MAb 206 blocked spread, altered intracellular trafficking of gH, and bound to surface VZV particles, which might facilitate their uptake and targeting for degradation. As a consequence, antibody interference with gH function would likely prevent or significantly reduce VZV replication in skin during primary or recurrent infection.

scholarly journals Characterization of Human Cytomegalovirus Glycoprotein-Induced Cell-Cell Fusion

2005 ◽  
Vol 79 (12) ◽  
pp. 7827-7837 ◽  
Author(s):  
Eric R. Kinzler ◽  
Teresa Compton
Keyword(s):  
Cell Lines ◽  
Human Cytomegalovirus ◽  
Neutralizing Antibodies ◽  
Syncytium Formation ◽  
Viral Envelope ◽  
Host Cell Membrane ◽  
Cellular Factors ◽  
A Cell ◽  
Cell Cell

ABSTRACT Human cytomegalovirus (CMV) infection is dependent on the functions of structural glycoproteins at multiple stages of the viral life cycle. These proteins mediate the initial attachment and fusion events that occur between the viral envelope and a host cell membrane, as well as virion-independent cell-cell spread of the infection. Here we have utilized a cell-based fusion assay to identify the fusogenic glycoproteins of CMV. To deliver the glycoprotein genes to various cell lines, we constructed recombinant retroviruses encoding gB, gH, gL, and gO. Cells expressing individual CMV glycoproteins did not form multinucleated syncytia. Conversely, cells expressing gH/gL showed pronounced syncytium formation, although expression of gH or gL alone had no effect. Anti-gH neutralizing antibodies prevented syncytium formation. Coexpression of gB and/or gO with gH/gL did not yield detectably increased numbers of syncytia. For verification, these results were recapitulated in several cell lines. Additionally, we found that fusion was cell line dependent, as nonimmortalized fibroblast strains did not fuse under any conditions. Thus, the CMV gH/gL complex has inherent fusogenic activity that can be measured in certain cell lines; however, fusion in fibroblast strains may involve a more complex mechanism involving additional viral and/or cellular factors.

scholarly journals Human immunodeficiency virus 1 (HIV-1) envelope-dependent cell–cell fusion modulation by HIV-positive sera is related to disease progression

2005 ◽  
Vol 86 (7) ◽  
pp. 1961-1966 ◽  
Author(s):  
L. Huerta ◽  
G. Gómez-Icazbalceta ◽  
L. Soto-Ramírez ◽  
M. Viveros-Rogel ◽  
R. Rodríguez ◽  
...  
Keyword(s):  
Cell Fusion ◽  
Cell Damage ◽  
Hiv Positive ◽  
Immunodeficiency Virus ◽  
Load Removal ◽  
Dependent Cell ◽  
Hiv 1 ◽  
Cell Cell

Fusion of CD4+ cells by HIV-1 envelope proteins (Env) is a mechanism of virus spread and cell damage. Production of antibodies able to influence cell–cell fusion in vivo may affect the course of the infection. The effect of sera from 49 HIV-1-positive patients was tested on an in vitro fusion assay using Env-expressing and normal Jurkat T cells labelled with DiI and DiO dyes, and flow cytometry for quantification of cell–cell fusion. Sera varied in their activity on fusion: 69·4 % inhibited, 24·5 % had no effect and 6·1 % enhanced cell fusion. Fusion activity correlated positively with the CD4+ T-cell count and inversely with the viral load. Removal of IgG or IgM from sera reduced or eliminated inhibition and enhancing activities, respectively. Antibodies with inhibitory activity predominate in early and intermediate stages of infection, whereas loss of inhibition or enhancement of fusion correlates with progression to AIDS.

scholarly journals BST2/Tetherin Overexpression Modulates Morbillivirus Glycoprotein Production to Inhibit Cell–Cell Fusion

Viruses ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 692 ◽  
Author(s):  
James T. Kelly ◽  
Stacey Human ◽  
Joseph Alderman ◽  
Fatoumatta Jobe ◽  
Leanne Logan ◽  
...  
Keyword(s):  
Cell Fusion ◽  
Measles Virus ◽  
Viral Fusion ◽  
Large Reduction ◽  
Glycosyl Phosphatidylinositol ◽  
Species Specific ◽  
Syncytia Formation ◽  
Cell Cell

The measles virus (MeV), a member of the genus Morbillivirus, is an established pathogen of humans. A key feature of morbilliviruses is their ability to spread by virus–cell and cell–cell fusion. The latter process, which leads to syncytia formation in vitro and in vivo, is driven by the viral fusion (F) and haemagglutinin (H) glycoproteins. In this study, we demonstrate that MeV glycoproteins are sensitive to inhibition by bone marrow stromal antigen 2 (BST2/Tetherin/CD317) proteins. BST2 overexpression causes a large reduction in MeV syncytia expansion. Using quantitative cell–cell fusion assays, immunolabeling, and biochemistry we further demonstrate that ectopically expressed BST2 directly inhibits MeV cell–cell fusion. This restriction is mediated by the targeting of the MeV H glycoprotein, but not other MeV proteins. Using truncation mutants, we further establish that the C-terminal glycosyl-phosphatidylinositol (GPI) anchor of BST2 is required for the restriction of MeV replication in vitro and cell–cell fusion. By extending our study to the ruminant morbillivirus peste des petits ruminants virus (PPRV) and its natural host, sheep, we also confirm this is a broad and cross-species specific phenotype.

scholarly journals Transcriptional suppression of AMPKα1 promotes breast cancer metastasis upon oncogene activation

2020 ◽  
Vol 117 (14) ◽  
pp. 8013-8021 ◽  
Author(s):  
Yong Yi ◽  
Deshi Chen ◽  
Juan Ao ◽  
Wenhua Zhang ◽  
Jianqiao Yi ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cell Adhesion ◽  
Cancer Metastasis ◽  
Kinase Activity ◽  
Critical Role ◽  
Breast Cancer Metastasis ◽  
Transcription Control ◽  
Cell Cell

AMP-activated protein kinase (AMPK) functions as an energy sensor and is pivotal in maintaining cellular metabolic homeostasis. Numerous studies have shown that down-regulation of AMPK kinase activity or protein stability not only lead to abnormality of metabolism but also contribute to tumor development. However, whether transcription regulation of AMPK plays a critical role in cancer metastasis remains unknown. In this study, we demonstrate that AMPKα1 expression is down-regulated in advanced human breast cancer and is associated with poor clinical outcomes. Transcription of AMPKα1 is inhibited on activation of PI3K and HER2 through ΔNp63α. Ablation of AMPKα1 expression or inhibition of AMPK kinase activity leads to disruption of E-cadherin-mediated cell–cell adhesion in vitro and increased tumor metastasis in vivo. Furthermore, restoration of AMPKα1 expression significantly rescues PI3K/HER2-induced disruption of cell–cell adhesion, cell invasion, and cancer metastasis. Together, these results demonstrate that the transcription control is another layer of AMPK regulation and suggest a critical role for AMPK in regulating cell–cell adhesion and cancer metastasis.

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