FIG. 6.

Nef-induced decrease of CD4/p56^lck association at the plasma membrane. (A) HeLa cells coexpressing p56^lck and either WT CD4 or CD4 CC/SS were transfected to achieve Nef expression or treated with PMA. After biotinylation of the cell surface proteins, biotinylated CD4 was immunoprecipitated, as described in Materials and Methods, and both CD4 and p56^lck were visualized by Western blotting, followed by immunodetection in the precipitated material (top) or in cleared lysates (20 μg of protein/lane; bottom). The intensity of the CD4 and p56^lck bands was quantified by densitometry using NIH Image software, and the p56^lck signal was normalized to that of cell surface CD4 (NA, not applicable). (B) Plotted data represent the percentage of the CD4-associated p56^lck signal intensity relative to that of mock-transfected or mock-treated cells expressing WT CD4 (100%) and are representative of three independent experiments.