Fig. 5. Arrow captures Wingless but less efficiently than Frizzled2. (A,A') Transfection of Frizzled2 leads to strong accumulation (compare the GFP signal on transfected cells with that on untransfected cells). (A) Anti-HA, which reveals transfected Frizzled2; (A') GFP-Wingless. (B,B') Transfection of Arrow in S2 cells causes weak (but significant) accumulation of exogenously added GFP-Wingless at the cell surface. Arrow is labelled in red (with anti-HA) and GFP-Wingless is shown in green. (A',B') Transfected cells are marked with an arrowhead and untransfected cells by an asterisk. Cells were kept at 4°C throughout to prevent endocytosis. Anti-HA was used to detect both transfected receptors to ensure that cells with similar expression levels would be compared. Samples were processed in parallel. (C) GFP-Wg binding to S2 cells transfected with Frizzled2 (top) or Arrow (bottom), as quantified by fluorescence intensity after immunocytochemistry using an anti-GFP antibody. Histograms show the percentage of cells (y-axis) with a given fluorescence intensity expressed in arbitrary units (x-axis). The maximum fluorescence recorded in Arrow-overexpressing cells is almost threefold less than that in Frizzled2-overexpressing cells. (D) Increased accumulation of Wingless onto Arrow-expressing (driven by dpp-Gal4) cells in a disc compromised for dynamin activity (shi[ts] hemizygote at 32°C for 3 hours). There is a faint stripe of Wingless accumulation in the dpp expression domain.