Soi3p/Rav1p functions at the early endosome to regulate endocytic trafficking to the vacuole and localization of trans-Golgi network transmembrane proteins

György Sipos, Jason H. Brickner, E. J. Brace, Linyi Chen, Alain Rambourg, Francois Kepes, Robert S. Fuller*

*Corresponding author for this work

Research output: Contribution to journalArticle

25 Scopus citations

Abstract

SOI3 was identified by a mutation, soi3-1, that suppressed a mutant trans-Golgi network (TGN) localization signal in the Kex2p cytosolic tail. SOI3, identical to RAV1, encodes a protein important for regulated assembly of vacuolar ATPase. Here, we show that Soi3/Rav1p is required for transport between the early endosome and the late endosome/prevacuolar compartment (PVC). By electron microscopy, soi3-1 mutants massively accumulated structures that resembled early endosomes. soi3Δ mutants exhibited a kinetic delay in transfer of the endocytic tracer dye FM4-64, from the 14°C endocytic intermediate to the vacuole. The soi3Δ mutation delayed vacuolar degradation but not internalization of the a-factor receptor Ste3p. By density gradient fractionation, Soi3/Rav1p associated as a peripheral protein with membranes of a density characteristic of early endosomes. The soi3 null mutation markedly reduced the rate of Kex2p transport from the TGN to the PVC but had no effect on vacuolar protein sorting or cycling of Vps10p. These results suggest that assembly of vacuolar ATPase at the early endosome is required for transport of both Ste3p and Kex2p from the early endosome to the PVC and support a model in which cycling through the early endosome is part of the normal itinerary of Kex2p and other TGN-resident proteins.

Original languageEnglish (US)
Pages (from-to)3196-3209
Number of pages14
JournalMolecular biology of the cell
Volume15
Issue number7
DOIs
StatePublished - Jul 2004

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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