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. 2009 Nov 30;285(6):4122–4129. doi: 10.1074/jbc.M109.016964

FIGURE 5.

FIGURE 5.

Efr and Gfr function redundantly for the O-fucosylation of Notch. A–O, the expression of wg (magenta in A, C, D, F, G, I, J, L, M, and O) in wild-type or various mutant wing discs of late third-instar larvae that ectopically express fng and GFP (green in B, C, E, F, H, I, K, L, N, and O). The expression of fng and GFP was driven by ptc-Gal4. A–C, a wild-type wing disc; D–F, Gfr1/Gfr1; G–I, Efr1/Y; J–L, Efr1/Y;;Gfr1/Gfr1; M–O, GmdH78/GmdH78. GFP shows the regions ectopically expressing fng. J and M show the ectopic expression of fng failed to induce ectopic wg expression (arrows). C, F, I, L, and O are merged images of A and B, D and E, G and H, J and K, and M and N, respectively. P, two pathways for transporting GDP-fucose to the ER, where the O-fucosylation of Notch occurs in Drosophila. GDP-mannose-4,6-dehydratase (Gmd) and GDP-4-keto-6-deoxymannose epimerase/reductase (FX) convert GDP-fucose from GDP-mannose in the cytoplasm (arrows at left). GDP-fucose is then transported into the ER or Golgi by two GDP-fucose transporters, Efr and Gfr, respectively. GDP-fucose is incorporated by Gfr into the Golgi, where it is used for the fucosylation of N-glycans. GDP-fucose that is incorporated into the Golgi by Gfr is also transported to the ER, possibly by retrograde vesicular transport. In the ER, where the O-fucosylation of Notch occurs, GDP-fucose is used as a donor of fucose for this modification of Notch. Bar, 100 μm.