Shc proteins are localized on endoplasmic reticulum membranes and are redistributed after tyrosine kinase receptor activation

The intracellular localization of She proteins was analyzed by immunofluorescence and immunoelectron microscopy in normal cells and cells expressing the epidermal growth factor receptor or the EGFR/erbB2 chimera. In unstimulated cells, the immunolabeling was localized in the central perinuclear area of the cell and mostly associated with the cytosolic side of rough endoplasmic reticulum membranes. Upon epidermal growth factor treatment and receptor tyrosine kinase activation, the immunolabeling became peripheral and was found to be associated,vith the cytosolic surface of the plasma membrane and endocytic structures, such as coated pits and endosomes, and with the peripheral cytosol. Receptor activation in cells expressing phosphorylation-defective mutants of She and erbB-2 kinase showed that receptor autophosphorylation, but not She phosphorylation, is required for redistribution of She proteins. The rough endoplasmic reticulum localization of She proteins in unstimulated cells and their massive recruitment to the plasma membrane, endocytic structures, and peripheral cytosol following receptor tyrosine kinase activation could account for multiple putative functions of the adaptor protein.