FIG 3.

Investigation of the ability of the identified SLAM mutants to trigger the CDV membrane fusion machinery. (A to C) Cell-cell fusion activity in Vero cells triggered by coexpression of CDV H, CDV F, and cSLAM (or cSLAM mutants). To improve the sensitivity of the assay, the cells were additionally transfected with a plasmid encoding the red fluorescent protein. Images of fluorescence emissions from induced cell-cell fusion in representative fields are shown. The pictures were taken 24 h posttransfection with a confocal microscope (Fluoroview FV1000; Olympus). (D and E) Dark-gray bars show the results for cell surface expression of the wt SLAM and SLAM mutants, determined by treating Vero cells 24 h posttransfection with an anti-HA MAb. After the addition of the secondary antibody, MFI values were recorded by flow cytometry. All values were normalized to the one recorded with the unmodified cSLAM molecule. Means ± SD of data from three independent experiments performed in triplicates are shown. Light-gray bars show the results for quantitative cell-cell fusion assay performed as described in the legend to Fig. 1F.