A. JEG-3 cells were transfected with Flag-M4 alone (white bars) or with either Rab5WT (black bars) or Rab5S34N (dominant-negative; grey bars). B. JEG-3 cells were transfected with either Flag-M4 alone (white bars) or with either Rab11aWT (black bars) or Rab11aS25N (dominant-negative; grey bars). C. JEG-3 cells were transfected with Flag-M4 alone (white bars) and either Rab15WT (black bars), Rab15N121I (dominant-negative; dark grey bars), Rab15T22N (dominant-negative; medium grey bars), or Rab15Q67L (constitutively active; light grey bars). Following transfection, cells were stimulated for 0, 15, or 30 minutes with 1mM carbachol. Internalization of M4 receptors was measured using the binding of [3H]NMS to intact cells as described in ‘Experimental Procedures.’ Data represent the means ± S.E. of four to ten independent experiments, each performed in triplicate.