Genetic dissection of early endosomal recycling highlights a TORC1-independent role for Rag GTPases

J Cell Biol. 2017 Oct 2;216(10):3275-3290. doi: 10.1083/jcb.201702177. Epub 2017 Aug 2.

Abstract

Endocytosed cell surface membrane proteins rely on recycling pathways for their return to the plasma membrane. Although endosome-to-plasma membrane recycling is critical for many cellular processes, much of the required machinery is unknown. We discovered that yeast has a recycling route from endosomes to the cell surface that functions efficiently after inactivation of the sec7-1 allele of Sec7, which controls transit through the Golgi. A genetic screen based on an engineered synthetic reporter that exclusively follows this pathway revealed that recycling was subject to metabolic control through the Rag GTPases Gtr1 and Gtr2, which work downstream of the exchange factor Vam6. Gtr1 and Gtr2 control the recycling pathway independently of TORC1 regulation through the Gtr1 interactor Ltv1. We further show that the early-endosome recycling route and its control though the Vam6>Gtr1/Gtr2>Ltv1 pathway plays a physiological role in regulating the abundance of amino acid transporters at the cell surface.

MeSH terms

  • Adaptor Proteins, Vesicular Transport / genetics
  • Adaptor Proteins, Vesicular Transport / metabolism
  • Endosomes* / genetics
  • Endosomes* / metabolism
  • Guanine Nucleotide Exchange Factors / genetics
  • Guanine Nucleotide Exchange Factors / metabolism
  • Mechanistic Target of Rapamycin Complex 1
  • Monomeric GTP-Binding Proteins* / genetics
  • Monomeric GTP-Binding Proteins* / metabolism
  • Multiprotein Complexes* / metabolism
  • Saccharomyces cerevisiae Proteins* / genetics
  • Saccharomyces cerevisiae Proteins* / metabolism
  • Saccharomyces cerevisiae* / genetics
  • Saccharomyces cerevisiae* / metabolism
  • TOR Serine-Threonine Kinases* / metabolism

Substances

  • Adaptor Proteins, Vesicular Transport
  • GTR2 protein, S cerevisiae
  • Gtr1 protein, S cerevisiae
  • Guanine Nucleotide Exchange Factors
  • LTV1 protein, S cerevisiae
  • Multiprotein Complexes
  • Saccharomyces cerevisiae Proteins
  • Sec7 guanine nucleotide exchange factors
  • VAM6 protein, S cerevisiae
  • TOR Serine-Threonine Kinases
  • Mechanistic Target of Rapamycin Complex 1
  • Monomeric GTP-Binding Proteins