Ectopic expression of a kinase-inactive Lyn mutant inhibits SCF-induced proliferation.

(A) Transfection of normal mast cells with kinase-inactive Lyn inhibits SCF-induced growth. Normal murine BMMCs were transfected with either kinase-inactive (KI) human Lyn (▴) or vector (V) control (▪) DNA. Twenty-four hours after transfection, lysates were prepared, and equivalent cell units were resolved by SDS-PAGE, transferred to Immobilon, and immunoblotted with antibody specific for human Lyn (upper panel). At the same time, cells were also assessed for SCF-induced [³H]-thymidine incorporation in QBSF-58 media (lower panel). Data represent the mean and standard deviation of triplicate wells. (B) Kinase-inactive Lyn inhibits SCF-induced growth, but wild-type Lyn does not. Normal murine BMMCs were transfected with K275L human Lyn (KI), vector control (V), or wild-type (WT) Lyn. Twenty-four hours after transfection, lysates were generated, resolved by SDS-PAGE, transferred to Immobilon, and immunoblotted with antibody specific for human Lyn (upper panel). Cells were also assessed for [³H]-thymidine incorporation in response to 100 ng/mL SCF (lower panel). Data represent the mean and standard deviation of triplicate wells.