FIG. 13.

Effect of various cytoplasmic mutations on CD2-mediated activation of MAP kinase. HL60 cells expressing CD2/299, CD2/305, CD2/P→A, or CD2/WT were activated for the indicated periods of time with 10 ng of PMA per ml (squares) or an activating pair of CD2-specific MAbs (circles). The cells were lysed and immunoprecipitated with an ERK-2-specific polyclonal antibody, and the MBP-specific kinase activity was assessed as described in Materials and Methods. For each stimulation condition, ERK-2 activity levels (as assessed by quantitation of the autoradiograph with a PhosphorImager) were normalized to the ERK-2 kinase activity in cells stimulated for 0 min, which was given an arbitrary value of 1. Results from one representative experiment of five total are shown.