Fig. 4. Sulfation analysis of retrograde transport in Vps26 siRNA-treated cells. (A,B) Western blot (A) and sufation analysis (B) performed on HeLa cells transfected with siRNAs targeting Vps26. Three different siRNA sequences (Seq.1, Seq.2, Seq.3) have been used, which all induced the downregulation of Vps26 expression. Loss of Vps26 expression correlated with inhibition of Shiga toxin transport to TGN/Golgi membranes. Results are given as the mean ± s.e.m. of three determinations. (C) Dose-response experiment with siRNA number 3. A correlation was observed between the expression levels of Vps26 (as determined by western blotting) and retrograde Shiga toxin trafficking (as determined by sulfation analysis). Linear-regression analysis shows that both variables are linked with a probability higher than 99%.