Tyrosine phosphorylation of Vav in FDCP-hMpl5 cells. (A) Thrombopoietin-induced tyrosine phosphorylation of Vav in FDCP-hMpl5 cells. FDCP-hMpl5 cells (107 cells/mL in PBS, pH 7.4) were lysed by the addition of an equal amount of a buffer containing 2% Triton X-100 before and after exposure to thrombopoietin (100 ng/mL) for various times as indicated. Vav was immunoprecipitated with specific Vav antisera. Immune complexes were resuspended in SDS-sample buffer. Tyrosine phosphorylation of Vav was detected as described in the legend to Fig 1. (B and C) PMA or ionomycin failed to induce tyrosine phosphorylation of Vav. FDCP-hMpl5 lysates were made as described in (A), except PMA (100 nmol/L) (B) or ionomycin (20 nmol/L) (C) was used as a stimulant where indicated.
