Fig. 4. The extracellular domain of Grk is released from the oocyte and internalized in follicle cells. (A) Structure of mbGrkmyc. (B) All eggs laid by UASp-mbGrkmyc/nos-Gal4 females have a strongly dorsalized eggshell. (C,D) Confocal sections showing UASp-mbGrkmyc/nos-Gal4 egg chambers stained with an anti-Grk antibody that detects the N-terminal region of the protein (C), or with an anti-Myc antibody that recognizes the intracellular region of the protein (D). While the uptake of the extracellular domain of Grk is clearly visible in follicle cells (C), the intracellular domain of Grk remains confined to the oocyte (D). Grk and Myc are in green, and actin is in red. (E) Western blot probed with anti-Myc antibody reveals a cleavage of mbGrkmyc. Lane 2 is a protein lysate from UASp-mbGrkmyc/nos-Gal4 ovaries in which two new bands are detected (arrows). The higher band corresponds to the full-length mbGrkmyc protein whereas the lower one corresponds to a cleaved form. These two bands are absent in extracts from wild-type ovaries (lane 1).
