Ric1p and the Ypt6p GTPase function in a common pathway required for localization of trans-Golgi network membrane proteins

Mol Biol Cell. 2001 Jan;12(1):13-26. doi: 10.1091/mbc.12.1.13.

Abstract

In Saccharomyces cerevisiae, clathrin is necessary for localization of trans-Golgi network (TGN) membrane proteins, a process that involves cycling of TGN proteins between the TGN and endosomes. To characterize further TGN protein localization, we applied a screen for mutations that cause severe growth defects in combination with a temperature-sensitive clathrin heavy chain. This screen yielded a mutant allele of RIC1. Cells carrying a deletion of RIC1 (ric1Delta) mislocalize TGN membrane proteins Kex2p and Vps10p to the vacuole. Delivery to the vacuole occurs in ric1Delta cells also harboring end3Delta to block endocytosis, indicative of a defect in retrieval to the TGN rather than sorting to endosomes. SYS1, originally discovered as a multicopy suppressor of defects caused by the absence of the Rab GTPase YPT6, was identified as a multicopy suppressor of ric1Delta. Further comparison of ric1Delta and ypt6Delta cells demonstrated identical phenotypes. Multicopy plasmids expressing v-SNAREs Gos1p or Ykt6p, but not other v- and t-SNAREs, partially suppressed phenotypes of ric1Delta and ypt6Delta cells. SLY1-20, a dominant activator of the cis-Golgi network t-SNARE Sed5p, also functioned as a multicopy suppressor. Because Gos1p and Ykt6p interact with Sed5p, these results raise the possibility that TGN membrane protein localization requires Ric1p- and Ypt6p-dependent retrieval to the cis-Golgi network.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Fungal Proteins / pharmacology
  • GTP Phosphohydrolases / metabolism
  • GTP Phosphohydrolases / pharmacology
  • Guanine Nucleotide Exchange Factors
  • Intracellular Membranes / chemistry
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Membrane Proteins / pharmacology
  • Monomeric GTP-Binding Proteins / genetics
  • Monomeric GTP-Binding Proteins / metabolism*
  • Monomeric GTP-Binding Proteins / pharmacology
  • Phenotype
  • Protein Transport / drug effects
  • Qb-SNARE Proteins
  • SNARE Proteins
  • Saccharomyces cerevisiae / chemistry
  • Saccharomyces cerevisiae Proteins*
  • Suppression, Genetic / drug effects
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Transformation, Genetic
  • Vesicular Transport Proteins*
  • trans-Golgi Network / chemistry*
  • trans-Golgi Network / genetics
  • trans-Golgi Network / metabolism

Substances

  • Fungal Proteins
  • GOS1 protein, S cerevisiae
  • Guanine Nucleotide Exchange Factors
  • Membrane Proteins
  • Qb-SNARE Proteins
  • RIC1 protein, S cerevisiae
  • SNARE Proteins
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors
  • Vesicular Transport Proteins
  • GTP Phosphohydrolases
  • Monomeric GTP-Binding Proteins
  • YPT6 protein, S cerevisiae