Semliki Forest virus induced cell-cell fusion at neutral extracellular pH

1990 ◽  
Vol 10 (4) ◽  
pp. 363-374 ◽  
Author(s):  
Christoph Kempf ◽  
Marcel R. Michel ◽  
Adames Omar ◽  
Pia Jentsch ◽  
Andreas Morell
Keyword(s):  
Cell Fusion ◽  
Semliki Forest Virus ◽  
Covalent Modification ◽  
Surface Proteins ◽  
Acidic Ph ◽  
Fusion Event ◽  
Cell Surface Proteins ◽  
Infected Cells ◽  
Peptide Segments ◽  
Cell Cell

Semliki Forest virus-induced cell-cell fusion from within was considered to exclusively occur at mildly acidic pH (<6.2). Data of this study show that such cell fusion can also be triggered by transient acidification of the cytoplasm of infected cells at an extracellular, neutral pH. Results were obtained by utilizing NH4Cl pulses combined with covalent modification of cell surface proteins. The observation implies a revision of the current consensus regarding the mechanism of Semliki Forest virus induced cell-cell fusion. We propose a model in which at least two peptide segments of the viral spike protein E1 may be involved in triggering the fusion event.

scholarly journals Cholesterol and host cell surface proteins contribute to cell-cell fusion induced by the Burkholderia type VI secretion system 5

PLoS ONE ◽  
2017 ◽  
Vol 12 (10) ◽  
pp. e0185715 ◽  
Author(s):  
Liam Whiteley ◽  
Maria Haug ◽  
Kristina Klein ◽  
Matthias Willmann ◽  
Erwin Bohn ◽  
...  
Keyword(s):  
Cell Surface ◽  
Host Cell ◽  
Cell Fusion ◽  
Secretion System ◽  
Surface Proteins ◽  
Type Vi Secretion System ◽  
Cell Surface Proteins ◽  
Type Vi Secretion ◽  
Host Cell Surface ◽  
Cell Cell

Dynamic changes in plasma membrane properties of semliki forest virus infected cells related to cell fusion

1988 ◽  
Vol 8 (3) ◽  
pp. 241-254 ◽  
Author(s):  
C. Kempf ◽  
M. R. Michel ◽  
U. Kohler ◽  
H. Koblet ◽  
H. Oetliker
Keyword(s):  
Plasma Membrane ◽  
Membrane Potential ◽  
Membrane Fusion ◽  
Cell Fusion ◽  
Semliki Forest Virus ◽  
Membrane Properties ◽  
Acidic Ph ◽  
Dynamic Changes ◽  
Infected Cells

The mechanism of the processes leading to membrane fusion is as yet unknown. In this report we demonstrate that changes in membrane potential and potassium fluxes correlate with Semliki Forest virus induced cell-cell fusion at mildly acidic pH. The changes observed occur only at pH's below 6.2 corresponding to values required to trigger the fusion process. A possible role of these alterations of the plasma membrane related to membrane fusion phenomena is discussed.

scholarly journals Virus-Mediated Cell-Cell Fusion

2020 ◽  
Vol 21 (24) ◽  
pp. 9644
Author(s):  
Héloïse Leroy ◽  
Mingyu Han ◽  
Marie Woottum ◽  
Lucie Bracq ◽  
Jérôme Bouchet ◽  
...  
Keyword(s):  
Cell Fusion ◽  
Fusion Proteins ◽  
Target Cells ◽  
Special Focus ◽  
Human Pathogens ◽  
General Process ◽  
Tissue Organization ◽  
Donor Cells ◽  
Infected Cells ◽  
Cell Cell

Cell-cell fusion between eukaryotic cells is a general process involved in many physiological and pathological conditions, including infections by bacteria, parasites, and viruses. As obligate intracellular pathogens, viruses use intracellular machineries and pathways for efficient replication in their host target cells. Interestingly, certain viruses, and, more especially, enveloped viruses belonging to different viral families and including human pathogens, can mediate cell-cell fusion between infected cells and neighboring non-infected cells. Depending of the cellular environment and tissue organization, this virus-mediated cell-cell fusion leads to the merge of membrane and cytoplasm contents and formation of multinucleated cells, also called syncytia, that can express high amount of viral antigens in tissues and organs of infected hosts. This ability of some viruses to trigger cell-cell fusion between infected cells as virus-donor cells and surrounding non-infected target cells is mainly related to virus-encoded fusion proteins, known as viral fusogens displaying high fusogenic properties, and expressed at the cell surface of the virus-donor cells. Virus-induced cell-cell fusion is then mediated by interactions of these viral fusion proteins with surface molecules or receptors involved in virus entry and expressed on neighboring non-infected cells. Thus, the goal of this review is to give an overview of the different animal virus families, with a more special focus on human pathogens, that can trigger cell-cell fusion.

scholarly journals Osmotic Balance Regulates Cell Fusion during Mating in Saccharomyces cerevisiae

1997 ◽  
Vol 138 (5) ◽  
pp. 961-974 ◽  
Author(s):  
Jennifer Philips ◽  
Ira Herskowitz
Keyword(s):  
Cell Wall ◽  
Cell Fusion ◽  
Cell Contact ◽  
Fusion Event ◽  
Glycerol Facilitator ◽  
Fusion Defect ◽  
Osmotic Balance ◽  
Glycerol 3 Phosphate Dehydrogenase ◽  
Gpd1 Gene ◽  
Cell Cell

Successful zygote formation during yeast mating requires cell fusion of the two haploid mating partners. To ensure that cells do not lyse as they remodel their cell wall, the fusion event is both temporally and spatially regulated: the cell wall is degraded only after cell–cell contact and only in the region of cell–cell contact. To understand how cell fusion is regulated, we identified mutants defective in cell fusion based upon their defect in mating to a fus1 fus2 strain (Chenevert, J., N. Valtz, and I. Herskowitz. 1994. Genetics 136:1287–1297). Two of these cell fusion mutants are defective in the FPS1 gene, which codes for a glycerol facilitator (Luyten, K., J. Albertyn, W.F. Skibbe, B.A. Prior, J. Ramos, J.M. Thevelein, and S. Hohmann. 1995. EMBO [Eur. Mol. Biol. Organ.] J. 14:1360–1371). To determine whether inability to maintain osmotic balance accounts for the defect in cell fusion in these mutants, we analyzed the behavior of an fps1Δ mutant with reduced intracellular glycerol levels because of a defect in the glycerol-3-phosphate dehydrogenase (GPD1) gene (Albertyn, J., S. Hohmann, J.M. Thevelein, and B.A. Prior. 1994. Mol. Cell. Biol. 14:4135– 4144): deletion of GPD1 partially suppressed the cell fusion defect of fps1 mutants. In contrast, overexpression of GPD1 exacerbated the defect. The fusion defect could also be partially suppressed by 1 M sorbitol. These observations indicate that the fusion defect of fps1 mutants results from inability to regulate osmotic balance and provide evidence that the osmotic state of the cell can regulate fusion. We have also observed that mutants expressing hyperactive protein kinase C exhibit a cell fusion defect similar to that of fps1 mutants. We propose that Pkc1p regulates cell fusion in response to osmotic disequilibrium. Unlike fps1 mutants, fus1 and fus2 mutants are not influenced by expression of GPD1 or by 1 M sorbitol. Their fusion defect is thus unlikely to result from altered osmotic balance.

scholarly journals Specific Biarsenical Labeling of Cell Surface Proteins Allows Fluorescent- and Biotin-tagging of Amyloid Precursor Protein and Prion Proteins

2009 ◽  
Vol 20 (1) ◽  
pp. 233-244 ◽  
Author(s):  
Yuzuru Taguchi ◽  
Zhen-Dan Shi ◽  
Brian Ruddy ◽  
David W. Dorward ◽  
Lois Greene ◽  
...  
Keyword(s):  
Cell Surface ◽  
Amyloid Precursor Protein ◽  
Extracellular Proteins ◽  
Surface Proteins ◽  
Precursor Protein ◽  
Cysteine Protease Inhibitor ◽  
Steric Effects ◽  
Cell Surface Proteins ◽  
Infected Cells ◽  
Fluorescent Tagging

Fluorescent tagging is a powerful tool for imaging proteins in living cells. However, the steric effects imposed by fluorescent tags impair the behavior of many proteins. Here, we report a novel technique, Instant with DTT, EDT, And Low temperature (IDEAL)-labeling, for rapid and specific FlAsH-labeling of tetracysteine-tagged cell surface proteins by using prion protein (PrP) and amyloid precursor protein (APP) as models. In prion-infected cells, FlAsH-labeled tetracysteine-tagged PrP converted from the normal isoform (PrPsen) to the disease-associated isoform (PrPres), suggesting minimal steric effects of the tag. Pulse-chase analysis of PrP and APP by fluorescent gel imaging demonstrated the utility of IDEAL labeling in investigating protein metabolism by identifying an as-yet-unrecognized C-terminal fragment (C3) of PrPsen and by characterizing the kinetics of PrPres and APP metabolism. C3 generation and N-terminal truncation of PrPres were inhibited by the anti-prion compound E64, a cysteine protease inhibitor. Surprisingly, E64 did not inhibit the synthesis of new PrPres, providing insight into the mechanism by which E64 reduces steady-state PrPres levels in prion-infected cells. To expand the versatility of tetracysteine tagging, we created new Alexa Fluor- and biotin-conjugated tetracysteine-binding molecules that were applied to imaging PrP endocytosis and ultrastructural localization. IDEAL-labeling extends the use of biarsenical derivatives to extracellular proteins and beyond microscopic imaging.

Mechanism of antibody stimulation of hexose transport in rat myoblasts

1984 ◽  
Vol 62 (5) ◽  
pp. 255-265 ◽  
Author(s):  
Theodore C. Y. Lo ◽  
Vincent Duronio
Keyword(s):  
Cell Surface ◽  
Covalent Modification ◽  
Membrane Receptors ◽  
Surface Proteins ◽  
Specific Cell ◽  
Activation Process ◽  
Hexose Transport ◽  
Antibody Treatment ◽  
Cell Surface Proteins ◽  
Membrane Components

We have recently demonstrated that exposure of rat myoblasts to anti-rat myoblast antiserum results in two- to three-fold activation of hexose transport. The present communication reports the possible mechanism(s) by which specific antibody can bring about such activation. Studies with Fab and Fc fragments indicate that the binding of Fab to specific cell surface component(s) is not sufficient to trigger activation of hexose transport; the immunoglobulin G (IgG) mediated dimerization of membrane components is required for this process. Although cytochalasin D has no effect on hexose transport in control and antibody-treated cells, pretreatment of cells with this inhibitor prevents antibody-mediated activation of hexose transport. It may be inferred from this observation that proper disposition of membrane components is required for the dimerization of membrane receptors. Since this activation of hexose transport is an irreversible process, it is possible that covalent modification of membrane components may have occurred as a result of antibody treatment. Pretreatment of cells with ammonium chloride or methylamine is found to abolish the antibody-mediated activation of hexose transport, even though these inhibitors have no effect on hexose transport in control and antibody-treated cells. These inhibitors may be acting on transglutaminase and (or) on some other proteins involved in the activation process. Several lines of evidence suggest that limited proteolytic cleavage of membrane components may be involved in the antibody-mediated activation of hexose transport. First, pretreatment with several protease inhibitors prevents activation of hexose transport. Second, several cell surface proteins are missing in antibody-treated cells. Third, limited proteolysis of cell surface proteins with trypsin can also bring about activation of hexose transport. In view of the fact that proteolytic activity cannot be detected in various IgG and serum preparations, it seems likely that endogenous membrane associated proteases may be involved in this activation process.

scholarly journals Development of a Novel High-Throughput Surrogate Assay to Measure HIV Envelope/CCR5/CD4-Mediated Viral/Cell Fusion Using BacMam Baculovirus Technology

2003 ◽  
Vol 8 (4) ◽  
pp. 463-470 ◽  
Author(s):  
Stephen Jenkinson ◽  
David C. Mc Coy ◽  
Sandy A. Kerner ◽  
Robert G. Ferris ◽  
Wendell K. Lawrence ◽  
...  
Keyword(s):  
Host Cell ◽  
Cell Fusion ◽  
High Throughput ◽  
Viral Envelope ◽  
Host Cells ◽  
Luciferase Reporter ◽  
Viral Fusion ◽  
Fusion Event ◽  
Surrogate Assay ◽  
Cell Cell

The initial event by which M-tropic HIV strains gain access to cells is via interaction of the viral envelope protein gp120 with the host cell CCR5 coreceptor and CD4. Inhibition of this event reduces viral fusion and entry into cells in vitro. The authors have employed BacMam baculovirus-mediated gene transduction to develop a cell/cell fusion assay that mimics the HIV viral/cell fusion process and allows high-throughput quantification of this fusion event. The assay design uses human osteosarcoma (HOS) cells stably transfected with cDNAs expressing CCR5, CD4, and long terminal repeat (LTR)-luciferase as the recipient host cell. An HEK-293 cell line transduced with BacMam viral constructs to express the viral proteins gp120, gp41, tat, and rev represents the virus. Interaction of gp120 with CCR5/CD4 results in the fusion of the 2 cells and transfer of tat to the HOS cell cytosol; tat, in turn, binds to the LTR region on the luciferase reporter and activates transcription, resulting in an increase in cellular luciferase activity. In conclusion, the cell/cell fusion assay developed has been demonstrated to be a robust and reproducible high-throughput surrogate assay that can be used to assess the effects of compounds on gp120/CCR5/CD4-mediated viral fusion into host cells.

Inductive regulation of cell fusion in leech

Development ◽  
1999 ◽  
Vol 126 (15) ◽  
pp. 3381-3390 ◽  
Author(s):  
D.E. Isaksen ◽  
N.J. Liu ◽  
D.A. Weisblat
Keyword(s):  
Cell Fusion ◽  
Critical Period ◽  
Ribonuclease A ◽  
Fusion Event ◽  
Ricin A Chain ◽  
Helobdella Robusta ◽  
A Cell ◽  
A Chain ◽  
Ricin A ◽  
Cell Cell

Cell-cell fusion is a component of many different developmental processes, but little is known about how cell-cell fusion is regulated. Here we investigate the regulation of a stereotyped cell-cell fusion event that occurs among the endodermal precursor cells of the glossiphoniid leech Helobdella robusta. We find that this fusion event is regulated inductively by a cell that does not itself fuse. We also show that biochemical arrest (by microinjection with ricin A chain or ribonuclease A) of the inducer or either of the fusion partners prevents fusion, but only if the arrest is initiated during a critical period long before the time at which fusion normally occurs. If the arrest occurs after this critical period, fusion occurs on schedule. These results suggest that both fusion partners play active roles in the process and that neither the induction nor the fusion itself requires concomitant protein synthesis.

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