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Vol. 19, Issue 7, 2682-2695, July 2008

This Article Full Text Full Text (PDF) Supplemental Materials All Versions of this Article: E07-11-1120v1 19/7/2682    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Chun, D. K. Articles by Kaplan, J. M. PubMed PubMed Citation Articles by Chun, D. K. Articles by Kaplan, J. M.

UNC-108/Rab2 Regulates Postendocytic Trafficking in Caenorhabditis elegans

Denise K. Chun^*, Jason M. McEwen^*,, Michelle Burbea, and Joshua M. Kaplan

Department of Molecular Biology, Massachusetts General Hospital, and Department of Genetics, Harvard Medical School, Boston MA 02114

Submitted November 8, 2007; Revised April 8, 2008; Accepted April 11, 2008
Monitoring Editor: Sandra Lemmon

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.

* These authors contributed equally to this work.

Present address: Department of Biological Chemistry, University of California Los Angeles, Los Angeles, CA 90095.

Address correspondence to: Joshua M. Kaplan (kaplan{at}molbio.mgh.harvard.edu)