MIPP affects the activation states of Rab5 and Rab7, but not Rac1 or Arf6. In separate experiments U251 cells were treated with 10 μM MIPP for the indicated periods of time and then harvested for pull down assays to measure the relative amounts of active Rac1 (A), Arf6 (B), Rab5 (C) or Rab7 (D), as described in Materials and Methods. In each case the values for active GTPase (left graph) or active/total GTPase (right graph) were expressed as the percent of the corresponding values for parallel control cultures that received an equivalent volume of vehicle (DMSO), indicated by the dashed line in each graph. As an additional control, the studies of Rab7 were conducted with cells treated with the inactive compound III instead of MIPP (E). Results are the means (± SD) compiled from three separate experiments. Values marked with an asterisk were significant at p ≤ 0.05 compared with the controls.