Upregulation of cortactin expression in CMK cells in response to differentiation stimulus. (A) CMK cells were treated with PMA (10 nmol/L) for the time period as indicated, lysed, and immunoprecipitated with 4F11. The precipitates were analyzed in an immunoblotting using C001 polyclonal antibody. The detail procedure was described in the Materials and Methods. The data shown here are representative of four experiments. (B) CMK and CMK11-5 cells at an exponential growth stage in serum were analyzed for cortactin expression by immunoblotting analysis. The data are representative of two experiments, showing much more of cortactin proteins in the highly differentiated CMK subclone, CMK11-5. (C) Expression of mRNAs for cortactin and HS1 in PMA-treated CMK cells. The Northern blotting analysis was performed as described in the Materials and Methods. The intensities of mRNA for cortactin and HS1 were normalized with the ribosomal RNA 28S and plotted after a densitometry analysis. The autoradiography of the Northern blot is shown in the inset. The cortactin RNA is shown as a single 3.5-kb transcript, and HS1 RNA is shown as a single 2.0-kb band. The panels on the bottom show ethidium bromide staining of ribosomal RNA in agarose gel as the loading control. The results are representative of three experiments.