Uptake of the purified grB molecule is dependent on dynamin and the CI-MPR. HeLa-DynWT or DN cells were treated to suppress (+tet) or induce (–tet) overexpression from the transfected dynamin cDNA. The relative mean fluorescence intensity was determined by flow cytometry. (A) Cells were incubated with grB-A488 at 37° C for up to 1 hour, and viable cells were analyzed. (B) Representative flow cytometry data of grB-A488 uptake in HeLa-DynDN cells. The mean fluorescence intensity (MFI) is noted along the right-hand side of the histogram charts for cells—untreated at 60 minutes or exposed to grB-A488 from 0 to 60 minutes. (C) HeLa-DynDN cells were incubated with grB-A488 under normal conditions (–), or in the presence of 10 mM G6P or M6P, and viable cells were analyzed. (D) Cells displaying negligible or high surface levels of the CI-MPR (CI-MPR^– or CI-MPR⁺, respectively) or HeLa-Dyn cells were surface labeled for the CI-MPR. The mean ± SD of 4 (A), 3 (C), or 5 (D) independent experiments is shown (*.01 < P < .05; ***P < .001).