UNC-108/Rab2 regulates postendocytic trafficking in Caenorhabditis elegans

Mol Biol Cell. 2008 Jul;19(7):2682-95. doi: 10.1091/mbc.e07-11-1120. Epub 2008 Apr 23.

Abstract

After endocytosis, membrane proteins are often sorted between two alternative pathways: a recycling pathway and a degradation pathway. Relatively little is known about how trafficking through these alternative pathways is differentially regulated. Here, we identify UNC-108/Rab2 as a regulator of postendocytic trafficking in both neurons and coelomocytes. Mutations in the Caenorhabditis elegans Rab2 gene unc-108, caused the green fluorescent protein (GFP)-tagged glutamate receptor GLR-1 (GLR-1::GFP) to accumulate in the ventral cord and in neuronal cell bodies. In neuronal cell bodies of unc-108/Rab2 mutants, GLR-1::GFP was found in tubulovesicular structures that colocalized with markers for early and recycling endosomes, including Syntaxin-13 and Rab8. GFP-tagged Syntaxin-13 also accumulated in the ventral cord of unc-108/Rab2 mutants. UNC-108/Rab2 was not required for ubiquitin-mediated sorting of GLR-1::GFP into the multivesicular body (MVB) degradation pathway. Mutations disrupting the MVB pathway and unc-108/Rab2 mutations had additive effects on GLR-1::GFP levels in the ventral cord. In coelomocytes, postendocytic trafficking of the marker Texas Red-bovine serum albumin was delayed. These results demonstrate that UNC-108/Rab2 regulates postendocytic trafficking, most likely at the level of early or recycling endosomes, and that UNC-108/Rab2 and the MVB pathway define alternative postendocytic trafficking mechanisms that operate in parallel. These results define a new function for Rab2 in protein trafficking.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Caenorhabditis elegans / physiology*
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / physiology*
  • Cloning, Molecular
  • Endocytosis
  • Endosomes / metabolism
  • Glycoside Hydrolases / metabolism
  • Green Fluorescent Proteins / metabolism
  • Models, Biological
  • Mutation*
  • Neurons / metabolism
  • Protein Transport
  • Qa-SNARE Proteins / metabolism
  • Synapses / metabolism
  • Transgenes
  • rab GTP-Binding Proteins / genetics
  • rab GTP-Binding Proteins / physiology*
  • rab2 GTP-Binding Protein / genetics
  • rab2 GTP-Binding Protein / physiology*

Substances

  • Caenorhabditis elegans Proteins
  • Qa-SNARE Proteins
  • Green Fluorescent Proteins
  • Glycoside Hydrolases
  • UNC-108 protein, C elegans
  • rab GTP-Binding Proteins
  • rab2 GTP-Binding Protein