GFP-RAB11 and mCherry-STX13 largely overlap in Ap3d1^−/−/Pldn^−/− cells or cells expressing SNARE binding mutants of AP-3 and BLOC-1. Ap3d1^−/−/Pldn^−/− cells that were untransduced (-) or reconstituted with AP-3δ^mut1 and Pldn^mut1 were transiently transfected to express GFP-RAB11 and mCherry-STX13 and analyzed by live-cell spinning disk microscopy. (A) Most endosomal structures in Ap3d1^−/−/Pldn^−/− cells contain both GFP-RAB11 and mCherry-STX13; most structures were punctate (arrows), and very few endosomal tubules were observed. (B and C) Two examples of GFP-RAB11 and mCherry-STX13 localization in Ap3d1^−/−/Pldn^−/− cells expressing AP-3δ^mut1 and Pldn^mut1. GFP-RAB11 and mCherry-STX13 colocalize to a subpopulation of endosomal structures, including both punctate structures (arrows) and long tubules (arrowheads). Scale bar, 5 µm. Insets are magnified 3.5-fold. Inset scale bar, 1 µm.