Scheme 1.

Scheme depicting the processing and degradation of tyrosinase within melanocytes. After maturation in the Golgi, tyrosinase is trafficked either to melanosomes for melanin synthesis or to the degradation machinery. The proteolysis of tyrosinase is divided into two pathways, that is, one integrated into the ERAD in the UPS whereas the other is integrated into the endosomal/lysosomal degradation system. Whether mature tyrosinase that integrates into the ERAD transports back to the ER or bypasses the ER is still unknown. In addition, the intracellular location where the ubiquitination of tyrosinase occurs remains to be determined (adapted from Figure 3 of [1]).