Lck and MAL travel in the same transport vesicles destined for the plasma membrane. (A) Jurkat cells stably expressing GFP-MAL were subjected to double label immunofluorescence analysis to detect GFP-MAL and endogenous Lck. (B) Cells were transfected with Lck-GFP and the distribution of Lck-GFP was analyzed 20 h later. A densitometric analysis of the distribution of Lck-GFP along the line in each type of cell is shown on the right panels. Arrows indicate the position of the periphery of the cell. (C) Jurkat cells stably expressing GFP-MAL were transiently transfected with plasmid DNA expressing Lck-Cherry and subjected to time-lapse videomicroscopy. The processes occurring within the region indicated by the dashed square are shown at higher magnification in the bottom panels. Solid and empty arrowheads indicate two vesicles transporting MAL and Lck together to the plasma membrane. Numbers indicate time in seconds. The plot on the right shows a high correlation of the colocalization of MAL and Lck throughout the time-lapse experiment (Pearson's correlation coefficient = 0.945).