Quantitative analyses of EGFR localization and trafficking dynamics in the follicular epithelium

Abstract

To bridge the gap between qualitative and quantitative analyses of the epidermal growth factor receptor (EGFR) in tissues, we generated a sfGFP-tagged EGF receptor (EGFR-sfGFP) in Drosophila. The homozygous fly appears wild type with EGFR expression and activation patterns that are consistent with previous reports in the ovary, early embryo, and imaginal discs. Using ELISA, we quantified an average of 1100, 6200, and 2500 receptors per follicle cell (FC) at stages 8/9, 10, and ≥11 of oogenesis, respectively. Interestingly, the spatial localization of the EGFR to the apical side of the FCs at early stages depended on the TGF-alpha-like ligand Gurken. At later stages, EGFR localized to basolateral positions of the FCs. Finally, we followed the endosomal localization of EGFR in the FCs. The EGFR co-localized with the late endosome, but no significant co-localization of the receptor was found with the early endosome. The EGFR-sfGFP fly is an exciting new resource to study cellular localization and regulation of EGFR in tissues.