Fig. 6. Melanosomal protein trafficking and aberrant processing seen in various types of OCA. The disruption of tyrosinase trafficking occurs at the level of the ER in OCA1 and OCA3, and at the immediate post-Golgi level in OCA2. The results of this study show that in OCA4, tyrosinase processing and trafficking is disrupted and that the enzyme is abnormally secreted from the cells within vesicles before delivery to early melanosomes.