Binding of either AP-3δ to VAMP7 or Pldn to STX13 is necessary for TYRP1 localization to melanosomes. (A–F) Pldn^−/− melan-pa melanocytes (A) or Ap3d1^−/−/Pldn^−/− melanocytes that were either untransduced (B) or stably transduced to express the indicated WT (black) or SNARE binding mutant (magenta) variants of AP-3δ and Pldn (C–F) were fixed, immunolabeled for STX13 and TYRP1, and analyzed by dIFM and brightfield microscopy. Shown are corresponding brightfield images (left), individual labels for TYRP1 and STX13, and merged images of TYRP1/STX13 and (for pigmented cells) of TYRP1/pigment granules pseudocolored magenta (right). Boxed regions are magnified fivefold in the insets. Arrows, TYRP1/STX13 overlap; arrowheads, TYRP1 label that does not overlap with STX13 (overlaps with pigment granules in C–E). Scale bars, 5 µm; inset scale bars, 1 µm. (G and H) Quantification of percentage overlap of TYRP1 with melanin (G) or STX13 (H) from dIFM/brightfield analyses of Pldn^−/− cells and Ap3d1^−/−/Pldn^−/− cells that were untransduced or express the indicated pairs of WT or SNARE binding mutant forms of AP-3δ and Pldn. Data represent mean ± SEM across 10–22 cells for each sample over three experiments. ***, P < 0.001; ****, P < 0.0001; nonsignificant differences between values are not indicated in H.