FIGURE 3.

The role of ubiquitin in endocytosis and degradation. Continuous PM protein sorting from the PM to the TGN/EE occur regardless of its ubiquitination status (1) Alternatively, PM protein mono-ubiquination might promote endocytosis of the PM proteins to EE/TGN (1), whereas deubiquitination could favor recycling (2) back to the PM. K63-linked polyubiquitination of PM proteins might promote endocytic sorting from the PM to EE/TGN (1). Alternatively, the PM proteins could be subject to K63-linked polyubiquitination at endosomes and in any case polyubiquitination PM proteins would then be sorted via MVBs into the lytic vacuole. This step involves further ESCRT components (3).