Fig. 4. Internalization and degradation of HhN and Hhc85s independent of Ptc. (A-C) dor⁸ clones induced in UAS-Hh /HhGal4 (A), HhN-GFP/HhGal4 (B) and Hhc85s-GFP/HhGal4 (C) wing discs. The graphs represent a normalized pixel intensity of Ptc, Hh and ß-Gal staining, measured in the area represented by white frames in A-C. The three forms of Hh accumulate in dor⁸ clones, indicating an active process of degradation. There is precise direct correlation between the amounts of accumulated wild type Hh and Ptc in A (see graph), but not in the case of the lipid-unmodified Hh forms, where Ptc is not acculumated (see graphs in B,C). (D-F) dor^8- clones in ap-Gal4/UAS-Hh-GFP (D), ap-Gal4/UAS-HhN-GFP (E) and ap-Gal4/UAS-Hhc85s-GFP (F) wing imaginal discs. There is increased accumulation of HhN-GFP and Hhc85s-GFP in dor^- clones, induced both in the A and P compartments, even when they are located far from their expressing domains (arrows in E,F). However, wild-type Hh-GFP accumulates over a very short range in A compartment dor^- clones (arrows in D) and is never accumulated in P compartment dor^- clones (arrowheads in D). The accumulation of HhN-GFP and Hhc85s-GFP (green) in the P compartment dor^- cells, where Ptc (red) is not present, indicates a process of internalization and degradation independent of Ptc (arrowheads in E,F). This is reinforced by the absence of Ptc accumulation in A compartment dor^- clones in the case of Hhc85s-GFP (arrows in F). In the case of HhN-GFP, the small amount of Ptc accumulation in dor^- clones induced in the A compartment reveals some interaction between HhN and the Ptc receptor (arrows in E). The diagrams on the right-hand side of the figure represent the areas of the disc shown in the confocal panels and the interpretation of the results shown.