Skip to main content
NCBI home page
Journal of Virology logoLink to Journal of Virology
. 1995 Nov;69(11):7205–7215. doi: 10.1128/jvi.69.11.7205-7215.1995

The amphotropic and ecotropic murine leukemia virus envelope TM subunits are equivalent mediators of direct membrane fusion: implications for the role of the ecotropic envelope and receptor in syncytium formation and viral entry.

J A Ragheb 1, H Yu 1, T Hofmann 1, W F Anderson 1
PMCID: PMC189642  PMID: 7474142

Abstract

The murine leukemia virus (MuLV) envelope protein was examined to determine which sequences are responsible for the differences in direct membrane fusion observed with the ecotropic and amphotropic MuLV subtypes. These determinants were studied by utilizing amphotropic-ecotropic chimeric envelope proteins that have switched their host range but retain their original fusion domain (TM subunit). Fusion was tested both in rodent cells and in 293 cells bearing the human homolog of the ecotropic MuLV receptor. The results demonstrate that the amphotropic TM is able to mediate cell-to-cell fusion to an extent equivalent to that mediated by the ecotropic TM, indicating that their fusion domains are equivalent. The "murinized" human homolog of the ecotropic receptor supports syncytium formation as well as the native murine receptor. These findings suggest that interactions between the ecotropic envelope protein and conserved sequences in the ecotropic receptor are the principal determinants of syncytium formation. The relationship of the fusion phenotype to pH-dependent infection and the route of viral entry was examined by studying virions bearing the chimeric envelope proteins. Such virions appear to enter cells via a pathway that is directed by the host range-determining region of their envelope rather than by sequences that confer pH dependence. Therefore, the pH dependence of infection may not reflect the initial steps in viral entry. Thus, it appears that both the syncytium phenotype and the route of viral entry are properties of the viral receptor, the amino-terminal half of the ecotropic envelope protein, or the interaction between the two.

Full Text

The Full Text of this article is available as a PDF (2.9 MB).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Albritton L. M., Bowcock A. M., Eddy R. L., Morton C. C., Tseng L., Farrer L. A., Cavalli-Sforza L. L., Shows T. B., Cunningham J. M. The human cationic amino acid transporter (ATRC1): physical and genetic mapping to 13q12-q14. Genomics. 1992 Mar;12(3):430–434. doi: 10.1016/0888-7543(92)90431-q. [DOI] [PubMed] [Google Scholar]
  2. Albritton L. M., Kim J. W., Tseng L., Cunningham J. M. Envelope-binding domain in the cationic amino acid transporter determines the host range of ecotropic murine retroviruses. J Virol. 1993 Apr;67(4):2091–2096. doi: 10.1128/jvi.67.4.2091-2096.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Albritton L. M., Tseng L., Scadden D., Cunningham J. M. A putative murine ecotropic retrovirus receptor gene encodes a multiple membrane-spanning protein and confers susceptibility to virus infection. Cell. 1989 May 19;57(4):659–666. doi: 10.1016/0092-8674(89)90134-7. [DOI] [PubMed] [Google Scholar]
  4. Andersen K. B. A domain of murine retrovirus surface protein gp70 mediates cell fusion, as shown in a novel SC-1 cell fusion system. J Virol. 1994 May;68(5):3175–3182. doi: 10.1128/jvi.68.5.3175-3182.1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Andersen K. B., Nexø B. A. Entry of murine retrovirus into mouse fibroblasts. Virology. 1983 Feb;125(1):85–98. doi: 10.1016/0042-6822(83)90065-x. [DOI] [PubMed] [Google Scholar]
  6. Andersen K. B. The fate of the surface protein gp70 during entry of retrovirus into mouse fibroblasts. Virology. 1985 Apr 15;142(1):112–120. doi: 10.1016/0042-6822(85)90426-x. [DOI] [PubMed] [Google Scholar]
  7. Battini J. L., Heard J. M., Danos O. Receptor choice determinants in the envelope glycoproteins of amphotropic, xenotropic, and polytropic murine leukemia viruses. J Virol. 1992 Mar;66(3):1468–1475. doi: 10.1128/jvi.66.3.1468-1475.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Eiden M. V., Farrell K., Warsowe J., Mahan L. C., Wilson C. A. Characterization of a naturally occurring ecotropic receptor that does not facilitate entry of all ecotropic murine retroviruses. J Virol. 1993 Jul;67(7):4056–4061. doi: 10.1128/jvi.67.7.4056-4061.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Eiden M. V., Farrell K., Wilson C. A. Glycosylation-dependent inactivation of the ecotropic murine leukemia virus receptor. J Virol. 1994 Feb;68(2):626–631. doi: 10.1128/jvi.68.2.626-631.1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Green N., Shinnick T. M., Witte O., Ponticelli A., Sutcliffe J. G., Lerner R. A. Sequence-specific antibodies show that maturation of Moloney leukemia virus envelope polyprotein involves removal of a COOH-terminal peptide. Proc Natl Acad Sci U S A. 1981 Oct;78(10):6023–6027. doi: 10.1073/pnas.78.10.6023. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Heard J. M., Danos O. An amino-terminal fragment of the Friend murine leukemia virus envelope glycoprotein binds the ecotropic receptor. J Virol. 1991 Aug;65(8):4026–4032. doi: 10.1128/jvi.65.8.4026-4032.1991. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Henderson L. E., Sowder R., Copeland T. D., Smythers G., Oroszlan S. Quantitative separation of murine leukemia virus proteins by reversed-phase high-pressure liquid chromatography reveals newly described gag and env cleavage products. J Virol. 1984 Nov;52(2):492–500. doi: 10.1128/jvi.52.2.492-500.1984. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Jones J. S., Risser R. Cell fusion induced by the murine leukemia virus envelope glycoprotein. J Virol. 1993 Jan;67(1):67–74. doi: 10.1128/jvi.67.1.67-74.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Kadan M. J., Sturm S., Anderson W. F., Eglitis M. A. Detection of receptor-specific murine leukemia virus binding to cells by immunofluorescence analysis. J Virol. 1992 Apr;66(4):2281–2287. doi: 10.1128/jvi.66.4.2281-2287.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Kavanaugh M. P., Miller D. G., Zhang W., Law W., Kozak S. L., Kabat D., Miller A. D. Cell-surface receptors for gibbon ape leukemia virus and amphotropic murine retrovirus are inducible sodium-dependent phosphate symporters. Proc Natl Acad Sci U S A. 1994 Jul 19;91(15):7071–7075. doi: 10.1073/pnas.91.15.7071. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Kim J. W., Closs E. I., Albritton L. M., Cunningham J. M. Transport of cationic amino acids by the mouse ecotropic retrovirus receptor. Nature. 1991 Aug 22;352(6337):725–728. doi: 10.1038/352725a0. [DOI] [PubMed] [Google Scholar]
  17. Klement V., Rowe W. P., Hartley J. W., Pugh W. E. Mixed culture cytopathogenicity: a new test for growth of murine leukemia viruses in tissue culture. Proc Natl Acad Sci U S A. 1969 Jul;63(3):753–758. doi: 10.1073/pnas.63.3.753. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Lambertenghi G., De Harven E., Sato T., Tennant J. R. Electron microscope study of a B A L B-c leukemia virus in cell culture systems. Cancer Res. 1972 Jun;32(6):1108–1116. [PubMed] [Google Scholar]
  19. Lenz J., Crowther R., Straceski A., Haseltine W. Nucleotide sequence of the Akv env gene. J Virol. 1982 May;42(2):519–529. doi: 10.1128/jvi.42.2.519-529.1982. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Markowitz D., Goff S., Bank A. A safe packaging line for gene transfer: separating viral genes on two different plasmids. J Virol. 1988 Apr;62(4):1120–1124. doi: 10.1128/jvi.62.4.1120-1124.1988. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Marsh M., Helenius A. Virus entry into animal cells. Adv Virus Res. 1989;36:107–151. doi: 10.1016/S0065-3527(08)60583-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. McClure M. O., Sommerfelt M. A., Marsh M., Weiss R. A. The pH independence of mammalian retrovirus infection. J Gen Virol. 1990 Apr;71(Pt 4):767–773. doi: 10.1099/0022-1317-71-4-767. [DOI] [PubMed] [Google Scholar]
  23. Miller A. D., Buttimore C. Redesign of retrovirus packaging cell lines to avoid recombination leading to helper virus production. Mol Cell Biol. 1986 Aug;6(8):2895–2902. doi: 10.1128/mcb.6.8.2895. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Miller D. G., Edwards R. H., Miller A. D. Cloning of the cellular receptor for amphotropic murine retroviruses reveals homology to that for gibbon ape leukemia virus. Proc Natl Acad Sci U S A. 1994 Jan 4;91(1):78–82. doi: 10.1073/pnas.91.1.78. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Miyamoto K., Gilden R. V. Electron microscopic studies of tumor viruses. I. Entry of murine leukemia virus into mouse embryo fibroblasts. J Virol. 1971 Mar;7(3):395–406. doi: 10.1128/jvi.7.3.395-406.1971. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Morgan R. A., Nussbaum O., Muenchau D. D., Shu L., Couture L., Anderson W. F. Analysis of the functional and host range-determining regions of the murine ectropic and amphotropic retrovirus envelope proteins. J Virol. 1993 Aug;67(8):4712–4721. doi: 10.1128/jvi.67.8.4712-4721.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Nussbaum O., Roop A., Anderson W. F. Sequences determining the pH dependence of viral entry are distinct from the host range-determining region of the murine ecotropic and amphotropic retrovirus envelope proteins. J Virol. 1993 Dec;67(12):7402–7405. doi: 10.1128/jvi.67.12.7402-7405.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Ott D., Friedrich R., Rein A. Sequence analysis of amphotropic and 10A1 murine leukemia viruses: close relationship to mink cell focus-inducing viruses. J Virol. 1990 Feb;64(2):757–766. doi: 10.1128/jvi.64.2.757-766.1990. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Ott D., Rein A. Basis for receptor specificity of nonecotropic murine leukemia virus surface glycoprotein gp70SU. J Virol. 1992 Aug;66(8):4632–4638. doi: 10.1128/jvi.66.8.4632-4638.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Park B. H., Matuschke B., Lavi E., Gaulton G. N. A point mutation in the env gene of a murine leukemia virus induces syncytium formation and neurologic disease. J Virol. 1994 Nov;68(11):7516–7524. doi: 10.1128/jvi.68.11.7516-7524.1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
  31. Pinter A., Fleissner E. Structural studies of retroviruses: characterization of oligomeric complexes of murine and feline leukemia virus envelope and core components formed upon cross-linking. J Virol. 1979 Apr;30(1):157–165. doi: 10.1128/jvi.30.1.157-165.1979. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Pinter A., Honnen W. J. Characterization of structural and immunological properties of specific domains of Friend ecotropic and dual-tropic murine leukemia virus gp70s. J Virol. 1984 Feb;49(2):452–458. doi: 10.1128/jvi.49.2.452-458.1984. [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Pinter A., Honnen W. J. Comparison of structural domains of gp70s of ecotropic Akv and dualtropic MCF-247 MuLVs. Virology. 1983 Aug;129(1):40–50. doi: 10.1016/0042-6822(83)90394-x. [DOI] [PubMed] [Google Scholar]
  34. Ragheb J. A., Anderson W. F. Uncoupled expression of Moloney murine leukemia virus envelope polypeptides SU and TM: a functional analysis of the role of TM domains in viral entry. J Virol. 1994 May;68(5):3207–3219. doi: 10.1128/jvi.68.5.3207-3219.1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
  35. Ragheb J. A., Anderson W. F. pH-independent murine leukemia virus ecotropic envelope-mediated cell fusion: implications for the role of the R peptide and p12E TM in viral entry. J Virol. 1994 May;68(5):3220–3231. doi: 10.1128/jvi.68.5.3220-3231.1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
  36. Rein A., Mirro J., Haynes J. G., Ernst S. M., Nagashima K. Function of the cytoplasmic domain of a retroviral transmembrane protein: p15E-p2E cleavage activates the membrane fusion capability of the murine leukemia virus Env protein. J Virol. 1994 Mar;68(3):1773–1781. doi: 10.1128/jvi.68.3.1773-1781.1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
  37. Rowe W. P., Pugh W. E., Hartley J. W. Plaque assay techniques for murine leukemia viruses. Virology. 1970 Dec;42(4):1136–1139. doi: 10.1016/0042-6822(70)90362-4. [DOI] [PubMed] [Google Scholar]
  38. Shinnick T. M., Lerner R. A., Sutcliffe J. G. Nucleotide sequence of Moloney murine leukaemia virus. Nature. 1981 Oct 15;293(5833):543–548. doi: 10.1038/293543a0. [DOI] [PubMed] [Google Scholar]
  39. Stoye J. P., Coffin J. M. The four classes of endogenous murine leukemia virus: structural relationships and potential for recombination. J Virol. 1987 Sep;61(9):2659–2669. doi: 10.1128/jvi.61.9.2659-2669.1987. [DOI] [PMC free article] [PubMed] [Google Scholar]
  40. White J. M. Membrane fusion. Science. 1992 Nov 6;258(5084):917–924. doi: 10.1126/science.1439803. [DOI] [PubMed] [Google Scholar]
  41. Wilson C. A., Eiden M. V. Viral and cellular factors governing hamster cell infection by murine and gibbon ape leukemia viruses. J Virol. 1991 Nov;65(11):5975–5982. doi: 10.1128/jvi.65.11.5975-5982.1991. [DOI] [PMC free article] [PubMed] [Google Scholar]
  42. Wilson C. A., Marsh J. W., Eiden M. V. The requirements for viral entry differ from those for virally induced syncytium formation in NIH 3T3/DTras cells exposed to Moloney murine leukemia virus. J Virol. 1992 Dec;66(12):7262–7269. doi: 10.1128/jvi.66.12.7262-7269.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
  43. Witte O. N., Tsukamoto-Adey A., Weissman I. L. Cellular maturation of oncornavirus glycoproteins: topological arrangement of precursor and product forms in cellular membranes. Virology. 1977 Feb;76(2):539–553. doi: 10.1016/0042-6822(77)90236-7. [DOI] [PubMed] [Google Scholar]
  44. Witte O. N., Wirth D. F. Structure of the murine leukemia virus envelope glycoprotein precursor. J Virol. 1979 Feb;29(2):735–743. doi: 10.1128/jvi.29.2.735-743.1979. [DOI] [PMC free article] [PubMed] [Google Scholar]
  45. Yoshimoto T., Yoshimoto E., Meruelo D. Identification of amino acid residues critical for infection with ecotropic murine leukemia retrovirus. J Virol. 1993 Mar;67(3):1310–1314. doi: 10.1128/jvi.67.3.1310-1314.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
  46. Yoshimoto T., Yoshimoto E., Meruelo D. Molecular cloning and characterization of a novel human gene homologous to the murine ecotropic retroviral receptor. Virology. 1991 Nov;185(1):10–17. doi: 10.1016/0042-6822(91)90748-z. [DOI] [PubMed] [Google Scholar]
  47. Yu H., Soong N., Anderson W. F. Binding kinetics of ecotropic (Moloney) murine leukemia retrovirus with NIH 3T3 cells. J Virol. 1995 Oct;69(10):6557–6562. doi: 10.1128/jvi.69.10.6557-6562.1995. [DOI] [PMC free article] [PubMed] [Google Scholar]
  48. van Zeijl M., Johann S. V., Closs E., Cunningham J., Eddy R., Shows T. B., O'Hara B. A human amphotropic retrovirus receptor is a second member of the gibbon ape leukemia virus receptor family. Proc Natl Acad Sci U S A. 1994 Feb 1;91(3):1168–1172. doi: 10.1073/pnas.91.3.1168. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from Journal of Virology are provided here courtesy of American Society for Microbiology (ASM)

RESOURCES