FIGURE 7: A working model for Osh6's role in TGN-LE trafficking. (A) A summary of the maturation of the trans-Golgi network (TGN) and post-Golgi trafficking. The formation of Pma1-vesicles for secretion occurs at late cisternae of the TGN while vesicles carrying carboxylpeptidase Y (CPY) or other vacuolar hydrolases to late endosome (LE) occurs in early cisternae of the TGN [41] (see text for detail). (B) A hypothetical action of up-regulated Osh6. Up-regulation of Osh6 transports more PI4P to the early cisternae of the TGN, which facilitates the TGN-to-LE trafficking since the formation of the CPY-carrying vesicles depends on Gga2-PI4P binding. The accelerated TGN-LE trafficking refurbishes fresh lipids to LE and vacuoles and thus support vacuolar functions. As a side effect, transporting PI4P out of the late cisternae of TGN delays the secretion of Pma1 and leads to the rerouting of Pma1 to LE and vacuoles.

41. Casler JC, Glick BS (2020). A microscopy-based kinetic analysis of yeast vacuolar protein sorting. Elife 9:e56844. 10.7554/eLife.56844