Model for AP-1 and KIF13A function in Tyrp1 sorting and endosome positioning. AP-1 is recruited to endosomes through its interaction with the sorting signal in the cytoplasmic domain of Tyrp1 (step 1). Further interaction of AP-1 with KIF13A (step 2) facilitates endosome tubulation and extension to the periphery of the cell along microtubules (MT). The endosomal tubules coated with AP-1 contact melanosomes with which they can fuse to deliver cargo (step 3).