Fig. 8. Influence of Rab18 and Rab18-S22N on ER-Golgi cycling of Galtase-YFP and p58-YFP in COS7 cells. (A) Frames from representative photobleach sequences acquired with a confocal microscope as described in Materials and Methods. (B) Frames from similar representative photobleach sequences taken from cells expressing p58-YFP. Cells doubly transfected with p58-YFP and CFP-Rab18-S22N or CFP-Rab18 had a similar appearance. (C) Representative recovery curves showing Golgi-associated Galtase-YFP fluorescence as a function of time in cells singly expressing Galtase-YFP or doubly transfected with Galtase-YFP and CFP-Rab18-S22N. (D) Representative recovery curves show Golgi-associated p58-YFP fluorescence as a function of time in cells singly transfected with p58-YFP or double transfected with p58-YFP and CFP-Rab18 or CFP-Rab18-S22N. Experimental design was as in C. (E) A simple model using pseudo-first-order kinetics to describe cycling of resident Golgi proteins between the ER and Golgi in these experiments. (F) Mean Golgi residence times calculated from photobleach recovery curves and ratios of Golgi/total cellular fluorescence (n>20) transfected with the indicated constructs (Galtase or p58-YFP, CFP-Rab18 or CFP-Rab18-S22N). (G) Mean ER residence times determined from the same cells shown in F. Error bars show s.e.m.