Fig. 8. Retrograde transport of CTxB appears to be unaffected in SNX1-suppressed cells. Control and SNX1-suppressed cell were subjected to a CTxB-toxin-uptake assay using Alexa555-conjugated CTxB (red channel). The toxin was surface-bound at 4°C and then either fixed directly (A) or allowed to internalize at 37°C for the indicated times. Fixed cells were immunolabeled with anti-SNX1 (Alexa488, green channel). (B) After 15 minutes, CTxB was found on vesicular structures where it extensively colocalized with SNX1. The toxin displayed a similar vesicular appearance in SNX1-suppressed cells. (C,D) At later time points the toxin was found accumulated in the juxtanuclear area to similar extents in both control and SNX1-suppressed cells, where it colocalized with giantin (E). (F) Colocalization analysis of giantin and STxB in control cells (13±6% colocalization; 94 of 200 evaluated cells with detectable Alexa555-CTxB label), SNX1-suppressed cells (26±13%; 71 of 149 cells with label) and SNX2-suppressed cells (15±8%; 21 of 43 cells with label) using MetaMorph. Values are given as the mean ± standard deviation (s.d.); bars, 20 µm.