FIG. 4.

mSos1/2, Grb2, and Shc occur in high-density fractions in sucrose gradients. Sonicates from Ba/F3-Fms or NIH 3T3 cells that were either unstimulated or stimulated with IL-3 for 5 min, CSF-1 for 2 min, or EGF for 1.5 min were fractionated over sucrose gradients. The locations of mSos1/2, Grb2, and Shc in membrane fractions obtained from the gradients were determined by Western blotting using the corresponding antibodies (left). Aliquots from the same sonicates that were applied to sucrose gradients were also analyzed for levels of phosphorylated Erk1/2 to assess the efficiency of growth factor stimulation (right). Each blot is representative of at least three independent experiments.