p210 is degraded through the proteasome-mediated pathway in SHP-2^Δ/Δ cells. Bcr-Abl–transduced SHP-2^Δ/Δ cells were treated with proteasome inhibitor lactacystin at the indicated concentrations for 8 hours (A) or with lactacystin (10 μM) for the indicated time periods (B). Cells were lysed in RIPA lysis buffer supplemented with 0.1% SDS. Cell lysates were prepared and then examined with anti–c-Abl IB. Blots were stripped and reimmunoblotted with anti–SHP-1 Ab to monitor protein loading. Shown are representative results of 3 independent experiments.