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. 2022 Apr 28;10:895853. doi: 10.3389/fcell.2022.895853

FIGURE 1.

FIGURE 1

Overview of unconventional protein secretion (UPS) pathways in mammals and plants, with a description of proteins following different UPS routes. From left to right: UPS type I, UPS type II, and UPS type III are used by leaderless proteins which employ different methods to go through the plasma membrane (PM). In type III autophagosomes are inserted to represent the crosstalk between UPS and autophagy (see Paragraph 1.1.3). The scheme of UPS type IV represents the destiny of SP/transmembrane domain-containing proteins translocated in the ER, the next journey to the plasma membrane in mammals, and the direct delivery to the vacuole in plants. However, such proteins normally traffic along the conventional secretory pathway and transit through the Golgi apparatus.