Cell fusion

Elegant studies have been carried out to investigate the structural and biochemical aspects of virus-cell fusion. Although influenza virus hemagglutinin and human immunodeficiency virus (HIV) gpl20 have been the best-studied models, numerous examples of this class I type fusion mechanism have been described. These experiments have shown that fusion is initiated by the formation of a trimeric coiled-coil helix adjacent to the fusion peptide on the virus exterior, the insertion of this fusion peptide into the host cell membrane, and the subsequent formation of a six-helix bundle (Skehel and Wiley, 1998). 

Unfortunately, there are no structures available for either the flaviviruses or alphaviruses under conditions approximating the fusion state. For both groups of viruses, entry is believed to occur following attachment of the virus to the cellular receptor and internalization of the particle into an endosome (Kielian, 1995 Heinz and Allison, 2001). Acidification of the endosome results in rearrangement of envelope proteins and subsequent insertion of the fusion peptide into the endosomal membrane (Levy-Mintz and Kielian, 1991 Allison et al., 2001). Ultimately this results in fusion of cellular and viral membranes and release of the nucleocapsid core and genome RNA into the cytoplasm of the infected cell. In vitro experiments 

Although structural studies of enveloped viruses have lagged behind those of nonenveloped viruses, progress in combining high-resolution cryo-EM results with independently derived atomic structures of virion components has provided pseudo-atomic resolution structures. In terms of whole virus particles, the greatest advances have been accomplished with spherical icosahedral enveloped viruses from the 

Aliperti, G., and Schlesinger, M. J. (1978). Evidence for an autoprotease activity of Sindbis virus capsid protein. Virology 90, 366-369. 

Allison, S. L., Schalich.J., Stiasny, K., Mandl, C. W., Kunz, C., and Heinz, F. X. (1995). Oligomeric rearrangement of tick-borne encephalitis virus envelope proteins induced by an acidic pH./ Virol. 69, 695-700. 

A number of protocols have been described for the generation of mouse hybrid-omas and workers have their own particular protocol. We have used a standard procedure for the fusion of mouse and rat myelomas with considerable success over the last twenty years and this is described in Protocol 7. Basically, 10 lymphocytes are mixed with 2 x 10 mouse myeloma cells or 5 X lO Y3 cells in a round-bottomed tube and pelleted by centrifugation. Then the cells are fused by the addition of 1 ml of 50% PEG 1500 and plated into HAT selection medium to allow the growth of the hybridomas generated. 

HT medium add 1 ml of HT to 100 ml of DMEM containing 10% PCS Feeder cells for fosion coltures and cloning of hybridomas (essential for fusions using rat myelomas) rat fibroblast cell lines derived from the xiphistemae of various strains are suspended in DMEM and irradiated with about 30 Gy (3000 rad) of X- or gamma rays, then frozen in 95% FCS, 5% DMSO, and stored in liquid nitrogen as aliquots of 5 x 10 cells. Use one aliquot for each 200 ml of HAT or HT medium. Alternatively, use thymocytes from spleen donors. 

Freezer medium freshly prepared 5% dimethyl sulfoxide, 95% FCS 

Mix 10 viable lymphocytes with 2 x 10 mouse myeloma cells or 5 x 10 rat myeloma cells in a 10 ml capped centrifuge tube and centrifuge for 3 min at 400 g. 

Pour off the supernatant, drain carefully with a Pasteur pipette, then release the cell pellet by gently tapping the tube on the bench. 

---

Zell-verschmel2ung, /. cell fusion, -wand, /. cell wall. -woUe, /. staple fiber, staple rayon artificial wool. 

Wild C, GreenweU T, Matthews T (1993) A synthetic peptide from HlV-1 gp41 is a potent inhibitor of virus-mediated cell-cell fusion, AIDS Res Hum Retroviruses 9 1051-1053... 

Poly(ethylene glycol) (PEG) is a polymer of considerable interest due to several properties, including solubility in both water and many organic solvents, non-toxicity and ability to induce cell fusion, and it has found many biological applications [59]. Despite its poor mechanical strength, attaching PEG chains onto mechanically strong materials, such as fibrils [60], is one way to harness its properties [61]. 

Further studies on the mechanism of resistance of aminoglycoside antibiotics focused on resistance genes existing in antibiotic-producer strains (mainly by Drs. Y. Okami and Kunimoto Hotta), and gradually clarified the relationship between the antibiotic-producing and -regulating mechanism. During this search, indolizomycin (1984) was discovered by cell fusion of two kinds of strains. 

The method involves cell fusion, and the resulting permanent cell line is called a hybridoma. Typically, B cells are obtained from the spleen of a mouse (or other suitable animal) previously injected with an antigen or mixture of antigens (eg, foreign cells). The B cells are... 

The cell fusion mixture is transferred to a culture medium containing hypoxanthine, aminopterin and thymidine (HAT medium). Unflised myeloma cells are unable to grow as they lack HGPRT. Unflised normal spleen cells can grow but their proliferahon is limited and they eventually die out. The hybridoma cell can proliferate in the HAT medium as the normal spleen cell supplies the enzyme which enables the hybridoma to utilize extracellular hypoxanthine. 

Pontow SE, Heyden NV, Wei S, Ratner L. Actin cytoskeletal reorganizations and coreceptor-mediated activation of rac during human immunodeficiency virus-induced cell fusion. J Virol 2004 78(13) 7138-7147. 

III. VIRUS-CELL FUSION INHIBITORS LECTINS, ALBUMINS, AND TRITERPENE DERIVATIVES... 

Despite their widely varying origin and structure, these different classes of compounds seem to be targeted at the virus-cell fusion process, although the exact mechanism by which the compounds inhibit fusion,... 

Nakashima H, Masuda M, Murakami T, Koyanagi Y, Matsumoto A, Fujii N, Yamamoto N. Anti-human immunodeficiency virus activity of a novel synthetic peptide, T22 ([Tyr-5,12,Lys-7]polyphemusin II) a possible inhibitor of virus-cell fusion. Antimicrob Agents Chemother 1992 36 1249 — 1255. 

Matsui, S-I., Yoshida, H Weinfeld, H., and Sandbeig, A. A. (1972). Induction of prophase in interphase nuclei by cell fusion with metaphase cells. J. Cell Biol. 54 120-132. 

Mohler, W. A., and Blau, H. M. (1996). Gene expression and cell fusion analyzed by lacZ complementation in mammalian cells. Proc. Natl. Acad. Sci. USA 93, 12423-12427. 

My hypothesis otherwise remains what it was in 1993 - the epithelial component originated from an epithelial animal and the amoeboid component originated from an amoeboid animal equipped with a protocnidocysts, and possibly already living as an intracellular parasite on the epithelial animal during some stage of its life cycle. One or another device for cell fusion would have to be invoked to explain how an amoeba and an epithelium... 

Cell fusion may underlie some observations of grafted cells 514 COMMON STEM CELL THERAPY CHALLENGES 514 CONCLUSIONS 514... 

Vassilopoulos,G., Wang, P. R. and Russell, D.W. Transplanted bone marrow forms liver by cell fusion. Nature422 901-904, 2003. 

Wang, X., Willenbring, H., Akkari, Y. et al. Cell fusion is the princple source of bone marrow derived hepatocytes. Nature 422 897-901, 2003. 

Cell-enclosing pressure vessel, 73 426 Cell-free hemoglobin, 4 113 Cell fusion, 3 816... 

---