Calcium ions are required for cell fusion mediated by the CD4-human immunodeficiency virus type 1 envelope glycoprotein interaction.

AUTOR(ES)

Dimitrov, D S

RESUMO

Calcium ions are required for fusion of a wide variety of artificial and biological membranes. To examine the role of calcium ions for cell fusion mediated by interactions between CD4 and the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (gp120-gp41), we used two experimental systems: (i) cells expressing gp120-gp41 and its receptor CD4, both encoded by recombinant vaccinia viruses, and (ii) chronically infected cells producing low levels of HIV-1. Fusion was measured by counting the number of syncytia and by monitoring the redistribution of fluorescence dyes by video microscopy. Syncytia did not form in solutions without calcium ions. Addition of calcium ions partially restored the formation of syncytia. EDTA and EGTA [ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid] blocked syncytium formation in culture media containing calcium ions. Membrane fusion as monitored by fluorescence dye redistribution also required calcium ions. Cell fusion increased with an increase in calcium ion concentration from 100 microM to 10 mM but was not affected by magnesium ions in the concentration range from 0 to 30 mM. Fibrinogen and fibronectin did not promote fusion in the absence or presence of Ca2+. Binding of soluble CD4 to gp120-gp41-expressing cells was not affected by Ca2+ and Mg2+. We conclude that Ca2+ is involved in postbinding steps in cell fusion mediated by the CD4-HIV-1 envelope glycoprotein interaction.

Documentos Relacionados

• Cell fusion mediated by interaction of a hybrid CD4.CD8 molecule with the human immunodeficiency virus type 1 envelope glycoprotein does occur after a long lag time.
• Human immunodeficiency virus envelope glycoprotein/CD4-mediated fusion of nonprimate cells with human cells.
• CD4 molecules with a diversity of mutations encompassing the CDR3 region efficiently support human immunodeficiency virus type 1 envelope glycoprotein-mediated cell fusion.
• Photoinactivation and kinetics of membrane fusion mediated by the human immunodeficiency virus type 1 envelope glycoprotein.
• Temperature dependence of cell-cell fusion induced by the envelope glycoprotein of human immunodeficiency virus type 1.