A role for Yip1p in COPII vesicle biogenesis

J Cell Biol. 2003 Oct 13;163(1):57-69. doi: 10.1083/jcb.200306118.

Abstract

Yeast Ypt1p-interacting protein (Yip1p) belongs to a conserved family of transmembrane proteins that interact with Rab GTPases. We encountered Yip1p as a constituent of ER-derived transport vesicles, leading us to hypothesize a direct role for this protein in transport through the early secretory pathway. Using a cell-free assay that recapitulates protein transport from the ER to the Golgi complex, we find that affinity-purified antibodies directed against the hydrophilic amino terminus of Yip1p potently inhibit transport. Surprisingly, inhibition is specific to the COPII-dependent budding stage. In support of this in vitro observation, strains bearing the temperature-sensitive yip1-4 allele accumulate ER membranes at a nonpermissive temperature, with no apparent accumulation of vesicle intermediates. Genetic interaction analyses of the yip1-4 mutation corroborate a function in ER budding. Finally, ordering experiments show that preincubation of ER membranes with COPII proteins decreases sensitivity to anti-Yip1p antibodies, indicating an early requirement for Yip1p in vesicle formation. We propose that Yip1p has a previously unappreciated role in COPII vesicle biogenesis.

Publication types

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

MeSH terms

  • COP-Coated Vesicles / metabolism*
  • Fungal Proteins / metabolism*
  • Golgi Apparatus / metabolism
  • Membrane Proteins
  • Microscopy, Electron
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae / ultrastructure
  • Saccharomyces cerevisiae Proteins
  • Vesicular Transport Proteins

Substances

  • Fungal Proteins
  • Membrane Proteins
  • Saccharomyces cerevisiae Proteins
  • Vesicular Transport Proteins
  • Yip1 protein, S cerevisiae