Mw. Black et Hrb. Pelham, A selective transport route from golgi to late endosomes that requires theyeast GGA proteins, J CELL BIOL, 151(3), 2000, pp. 587-600
Pep12p is a yeast syntaxin located primarily in late endosomes. Using mutag
enesis of a green fluorescent protein chimera we have identified a sorting
signal FSDSPEF, which is required for transport of Pep12p from the exocytic
pathway to late endosomes, from which it can, when overexpressed, reach th
e vacuole. When this signal is mutated, Pep12p instead passes to early endo
somes, a step that is determined by its transmembrane domain. Surprisingly,
Pep12p is then specifically retained in early endosomes and does not go on
to late endosomes.
By testing appropriate chimeras in mutant strains, we found that FSDSPEF-de
pendent sorting was abolished in strains lacking Gga1p and Gga2p, Golgi-ass
ociated coat proteins with homology to gamma adaptin, In the gga1 gga2 doub
le mutant endogenous Pep12p cofractionated with the early endosome marker T
lg1p, and recycling of Snc1p through early endosomes was defective. Pep12p
sorting was also defective in cells lacking the clathrin heavy or light cha
in. We suggest that specific and direct delivery of proteins to early and l
ate endosomes is required to maintain the functional heterogeneity of the e
ndocytic pathway and that the GGA proteins, probably in association with cl
athrin, help create vesicles destined for late endosomes.