Figure 1.

Effect of Nef on the surface expression of indicator proteins containing dileucine- or tyrosine-based sorting motifs. 293 cells were transfected with plasmids encoding the transmembrane indicator proteins Tac, IL-2 receptor-α chain (0.25 μg) (A); TTMb, a chimera containing the extracellular and transmembrane domains of Tac fused to a cytoplasmic domain containing a tyrosine-based motif (2.5 μg) (B and D); or Tac-DKQTLL, a fusion protein in which the dileucine-based motif DKQTLL is appended to the C terminus of the Tac cytoplasmic domain (2 μg) (C). A plasmid encoding the GFP (0.5 μg) was included as a transfection marker. Cells were stained with anti-CD25 (which recognizes Tac) conjugated to PE and analyzed by flow cytometry. The mean PE fluorescence (surface level of Tac) for each GFP channel number (transfection efficiency) is plotted for 293 cells transfected with each of the Tac indicator proteins with and without competitors. +Nef cells were transfected with 15 μg of Nef expression vector. +Lamp cells were transfected with 15 μg of Lamp1 expression vector.