Crkl and c-Cbl were coimmunoprecipitated from the lysates from FDCP-hMpl5 cells stimulated by thrombopoietin. (A and B) Crkl immunoprecipitates from thrombopoietin-treated FDCP-hMpl5 cells contain a tyrosine phosphorylated 120-kD protein (*). FDCP-hMpl5 cells were lysed at the indicated times by the addition of an equal amount of a buffer containing 2% Triton X-100 before and after exposure to thrombopoietin (100 ng/mL). Tyrosine-phosphorylated proteins (A) and Crkl (B) in the Crkl immunoprecipitates were detected as described in Fig 1. Lane 1, resting FDCP-hMpl5 cells; lanes 2 through 5, the lysates from FDCP-hMpl5 cells 1, 5, 10, and 30 minutes after stimulation with thrombopoietin. (C) Crkl immunoprecipitate from thrombopoietin-stimulated FDCP-hMpl5 cells contains c-Cbl. FDCP-hMpl5 cells were lysed by the addition of an equal amount of a buffer containing 2% Triton X-100 before and 10 minutes after exposure to thrombopoietin (100 ng/mL). c-Cbl (upper panel) and Crkl (lower panel) in the Crkl immunoprecipitates were detected as described in Fig 1.