Sdk binds and regulates WRC localization and activity via its conserved C-terminal motif. (A) sdk mutant MARCM clones stained for SCAR, 26 h APF. (B) SCAR levels decrease cell-autonomously in the clones. SCAR levels at contacts: Mann-Whitney U test, P = .0356; SCAR levels at vertices/full contacts: Mann-Whitney U test, P = .1753; n = 30 WT contacts and 40 sdkΔ15contacts across three retinas each. (C and D) HA::Sdk expressing clones in retina, 26 h APF (C) and third instar wing imaginal disc (D). SCAR levels decrease cell-autonomously in the clones. (E–G) GMR-GAL4 (E), GMR>HA::Sdk (F), and GMR>HA::SdkΔCT (G) retinas stained for SCAR, 32 h APF. SCAR levels decrease broadly in the GMR>HA::Sdk eyes but are normal in HA::SdkΔCT eyes. Mechanosensory bristles do not express GMR-GAL4 (arrowheads). (H) Detection of Sdk–SCAR interaction using a GST pulldown assay. Left: Expression of GST alone, GST fused to the Sdk ICD (GST-SdkICD), and GST fused to the Sdk ICD with a deleted C-terminal motif (GST-SdkICDΔCT) were assessed using Coomassie-stained gels. Right: Equal levels of GST, GST-SdkICD, and GST-SdkICDΔCT were used to pull down SCAR from S2 cell lysates. SCAR formed a complex with SdkICD but not with the SdkICDΔCT deletion mutant. The experiment was repeated three times, and one representative result is shown. (I) Quantification of eye phenotypes induced by HA::Sdk and HA::SdkICDΔCT. Deletion of the Sdk C-terminal sequence motif reversed HA::Sdk induced phenotypes. χ2 test; **, P < 0.01; ***, P = 0.0001; ****, P < 0.0001. Scale bar, 10 μm. Source data are available for this figure: SourceData F4.
