FIG. 2.

Lck is degraded after T-cell activation in the absence of active Hsp90. (A) Human PBMC were activated for various lengths of time with anti-CD3- and anti-CD28-coated polystyrene beads either in the absence or presence of the Hsp90 inhibitor GA. PBMC were pretreated with GA for 30 min before activation. Cells were lysed and immunoblotted for Lck. (B) PBMC were activated as described in panel A in the absence or presence of GA and the proteasome inhibitor epoxomycin (Epox) as indicated. Cells were pretreated with epoxomycin for 90 min and with GA for 30 min before activation. Cell lysates were immunoblotted for Lck. The 56-kDa as well as the phosphorylated 59-kDa form of Lck are indicated.