Cytoplasm to vacuole trafficking of aminopeptidase I requires a t-SNARE-Sec1p complex composed of Tlg2p and Vps45p

Hagai Abeliovich, Tamara Darsow, Scott D. Emr*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

109 Scopus citations

Abstract

Aminopeptidase I (API) is imported into the yeast vacuole/lysosome by a constitutive non-classical vesicular transport mechanism, the cytoplasm to vacuole targeting (Cvt) pathway. Newly synthesized precursor API is sequestered in double-membrane cytoplasmic Cvt vesicles. The Cvt vesicles fuse with the vacuole, releasing single-membrane Cvt bodies containing pro-API into the vacuolar lumen, and maturation of API occurs when the Cvt body is degraded, releasing mature API. Under starvation conditions, API is transported to the vacuole by macroautophagy, an inducible, nonselective mechanism that shares many similarities with the Cvt pathway. Here we show that Tlg2p, a member of the syntaxin family of t-SNARE proteins, and Vps45p, a Sec1p homologue, are required in the constitutive Cvt pathway, hut not in inducible macroautophagy. Fractionation and protease protection experiments indicate that Tlg2p is required prior to or at the step of API segregation into the Cvt vesicle. Thus, the early Vps45-Tlg2p-dependent step of the Cvt pathway appears to be mechanistically distinct from the comparable stage in macroautophagy. Vps45p associates with both the Tlg2p and Pep12p t-SNAREs, but API maturation is not blocked in a pep12(ts) mutant, indicating that Vps45p independently regulates the function of multiple t-SNARES at distinct trafficking steps.

Original languageAmerican English
Pages (from-to)6005-6016
Number of pages12
JournalEMBO Journal
Volume18
Issue number21
DOIs
StatePublished - 1 Nov 1999
Externally publishedYes

Keywords

  • Autophagy
  • Cvt
  • Rapamycin
  • Sec1p
  • Tlg2 t-SNARE

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