Arp2/3 and Pls3 are required for the correct translocation of TrkB to the cell surface. (A) Control and Smn^−/−;SMN2 growth cones stained against Arp3 (gray), Pls3 (cyan) and F-actin (Phalloidin, yellow). Normalized mean gray values of Arp3 (N = 4, n = 130; U-Mann–Whitney, ***P ≤ 0.001). (B) Maximum intensity projections of SIM images of control and Smn^−/−;SMN2 growth cones stained against Arp3 (magenta), Pls3 (cyan) and F-actin (Phalloidin, yellow). (C) shLuci and shPls3 growth cones stained against Arp3 (gray) and F-actin (Phalloidin, yellow). Normalized mean gray values of Arp3 (N = 3, n = 90; U-Mann–Whitney, P **** ≤ 0.0001). (D) Growth cones from control and Smn^−/−;SMN2 motoneurons transduced with LV-mCh and LV-hPLS3 stained against Arp3 (gray) and F-actin (Phalloidin, yellow). Normalized mean gray values of Arp3 (N = 3, n = 90; ANOVA Kruskal–Wallis, P ** ≤ 0.01; P **** ≤ 0.0001). (E) Growth cones from control and Smn^−/−;SMN2 motoneurons that were pre-treated with 50 µM CK-666 and stained against surface TrkB (gray) and Synaptophysin-1 (SYP, magenta). Normalized mean gray values of surface TrkB in control and Smn^−/−;SMN2 terminals pre-treated with CK-666 and subjected to the recovery assay (N = 4, n = 83; ANOVA Kruskal–Wallis, ****P ≤ 0.0001). (F) Growth cones from Smn^−/−;SMN2 motoneurons transduced with LV-hPLS3 that were pre-treated with CK-666 and stained against surface TrkB (gray) and SYP (magenta). Normalized mean gray values of surface TrkB in LV-hPLS3 transduced Smn^−/−;SMN2 terminals (LV-mCh data not shown) pre-treated with CK-666 and subjected to the recovery assay (N = 3, n = 72; ANOVA Kruskal–Wallis, **P ≤ 0.01; ***P ≤ 0.001; ****P ≤ 0.0001). Data are presented as scatter dot plot with bar. Bar represents the mean ± SEM. Scale bars: 5 µm.