Document 0605
 DOCN  M9550605
 TI    Temperature dependence of cell-cell fusion induced by the envelope
       glycoprotein of human immunodeficiency virus type 1.
 DT    9505
 AU    Frey S; Marsh M; Gunther S; Pelchen-Matthews A; Stephens P; Ortlepp S;
       Stegmann T; Department of Biophysical Chemistry, Biozentrum of the
       University; of Basel, Switzerland.
 SO    J Virol. 1995 Mar;69(3):1462-72. Unique Identifier : AIDSLINE
       MED/95156570
 AB    We investigated cell-cell fusion induced by the envelope glycoprotein of
       human immunodeficiency virus type 1 strain IIIB expressed on the surface
       of CHO cells. These cells formed syncytia when incubated together with
       CD4-positive human lymphoblastoid SupT1 cells or HeLa-CD4 cells but not
       when incubated with CD4-negative cell lines. A new assay for binding and
       fusion was developed by using fluorescent phospholipid analogs that were
       produced in SupT1 cells by metabolic incorporation of BODIPY-labeled
       fatty acids. Fusion occurred as early as 10 min after mixing of labeled
       SupT1 cells with unlabeled CHO-gp160 cells at 37 degrees C. When both
       the fluorescence assay and formation of syncytia were used, fusion of
       SupT1 and HeLa-CD4 cells with CHO-gp160 cells was observed only at
       temperatures above 25 degrees C, confirming recent observations (Y.-K.
       Fu, T.K. Hart, Z.L. Jonak, and P.J. Bugelski, J. Virol. 67:3818-3825,
       1993). This temperature dependence was not observed with influenza
       virus-induced cell-cell fusion, which was quantitatively similar at both
       20 and 37 degrees C, indicating that cell-cell fusion in general is not
       temperature dependent in this range. gp120-CD4-specific cell-cell
       binding was found over the entire 0 to 37 degrees C range but increased
       markedly above 25 degrees C. The enhanced binding and fusion were
       reduced by cytochalasins B and D. Binding of soluble gp120 to
       CD4-expressing cells was equivalent at 37 and 16 degrees C. Together,
       these data indicate that during gp120-gp41-induced syncytium formation,
       initial cell-cell binding is followed by a cytoskeleton-dependent
       increase in the number of gp120-CD4 complexes, leading to an increase in
       the avidity of cell-cell binding. The increased number of gp120-CD4
       complexes is required for fusion, which suggests that the formation of a
       fusion complex consisting of multiple CD4 and gp120-gp41 molecules is a
       step in the fusion mechanism.
 DE    Animal  Antigens, CD4/METABOLISM  *Cell Fusion/DRUG EFFECTS
       Cytochalasin B/PHARMACOLOGY  CHO Cells  Gene Products, env/*PHYSIOLOGY
       Hamsters  HIV Envelope Protein gp120/*PHYSIOLOGY  HIV-1/*PATHOGENICITY
       In Vitro  Protein Precursors/*PHYSIOLOGY  Recombinant Proteins  Support,
       Non-U.S. Gov't  Temperature  JOURNAL ARTICLE

       SOURCE: National Library of Medicine.  NOTICE: This material may be
       protected by Copyright Law (Title 17, U.S.Code).