FIG. 4.

HRG induces ErbB-2 and Stat3 cytoplasmic colocalization. (A) Cells were treated with HRG for 10 min or left untreated. ErbB-2 (green) and Stat3 (red) were localized as described in Materials and Methods. The same cells are shown in each row, and images in the right panel were formed by superimposition of images from the other two panels in the same row. Nuclei were stained with DAPI (4′,6-diamidino-2-phenylindole) (blue). HRG-induced colocalization of ErbB-2 and Stat3 is denoted by yellow coloration in the cytoplasm. The images are representative of three experiments. Bars, 5 μm. (B) C4HD cells were treated as described for panel A, and nuclear and cytosolic fractions were prepared. Fifty micrograms of protein from nuclear extracts and 25 μg protein from cytosolic extracts were analyzed by Western blotting for ErbB-2 and Stat3 expression. Membranes were then stripped and hybridized with an anti-p85 phosphatidylinositol 3-kinase (PI-3K) subunit antibody or an anti-retinoblastoma (Rb) antibody in order to control for cellular fractionation efficiency. W, Western blot. The data are representative of two experiments.