Endocytic trafficking of activated EGFR is AP-2 dependent and occurs through preformed clathrin spots

The removal of the epidermal growth factor receptor (EGFR) from the cell surface by endocytosis is triggered by receptor activation, but many facets of EGFR trafficking remain unresolved. We employed total internal fluorescence microscopy to elucidate the dynamics of activated EGFR at the cell surface through live-cell imaging. The results of these studies demonstrate that: (1) EGFR does not localize to caveolae in live cells either before or after activation; (2) EGFR does localize to clathrin-coated pits, but only after activation; (3) activation does not result in the formation of new clathrin-coated pits; (4) activated EGFR clusters at sites of preformed clathrin lattices; (5) The AP-2 complex is involved in the internalization of activated EGFR. Using imaging techniques to show the endocytic sorting of activated EGFR for the first time in live cells, these studies suggest a refinement of the model for EGFR entry.