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PMID: 18596236 Published · ppublish English Journal Article Research Support, N.I.H., Extramural

UNC-18 promotes both the anterograde trafficking and synaptic function of syntaxin.

Molecular biology of the cell ·Vol. 19 ·No. 9 ·2008-09-00 ·Pages 3836-46

McEwen JM, Kaplan JM

Abstract

The SM protein UNC-18 has been proposed to regulate several aspects of secretion, including synaptic vesicle docking, priming, and fusion. Here, we show that UNC-18 has a chaperone function in neurons, promoting anterograde transport of the plasma membrane soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein Syntaxin-1. In unc-18 mutants, UNC-64 (Caenorhabditis elegans Syntaxin-1) accumulates in neuronal cell bodies. Colocalization studies and analysis of carbohydrate modifications both suggest that this accumulation occurs in the endoplasmic reticulum. This trafficking defect is specific for UNC-64 Syntaxin-1, because 14 other SNARE proteins and two active zone markers were unaffected. UNC-18 binds to Syntaxin through at least two mechanisms: binding to closed Syntaxin, or to the N terminus of Syntaxin. It is unclear which of these binding modes mediates UNC-18 function in neurons. The chaperone function of UNC-18 was eliminated in double mutants predicted to disrupt both modes of Syntaxin binding, but it was unaffected in single mutants. By contrast, mutations predicted to disrupt UNC-18 binding to the N terminus of Syntaxin caused significant defects in locomotion behavior and responsiveness to cholinesterase inhibitors. Collectively, these results demonstrate the UNC-18 acts as a molecular chaperone for Syntaxin transport in neurons and that the two modes of UNC-18 binding to Syntaxin are involved in different aspects of UNC-18 function.

MeSH Terms
Animals Caenorhabditis elegans Caenorhabditis elegans Proteins/metabolism Endoplasmic Reticulum/metabolism Gene Expression Regulation Glycoside Hydrolases/metabolism Green Fluorescent Proteins/metabolism Models, Biological Mutation Neurons/metabolism Phosphoproteins/metabolism Protein Structure, Tertiary Protein Transport Qa-SNARE Proteins/metabolism Synapses/metabolism Vesicular Transport Proteins/metabolism
Chemicals
Caenorhabditis elegans Proteins Phosphoproteins Qa-SNARE Proteins Unc-18 protein, C elegans Vesicular Transport Proteins Green Fluorescent Proteins Glycoside Hydrolases
Authors & Affiliations
2 authors, click to expand affiliations / ORCID
McEwen Jason M
Department of Molecular Biology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
Kaplan Joshua M
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Article Info
Journal
Molecular biology of the cell
Abbr.
Mol Biol Cell
ISSN
1939-4586
DOI
10.1091/mbc.e08-02-0160
Published
2008-09-00
Epub
2008-00-02
Pages
3836-46
Language
English
Region
United States
NLM ID
9201390
PMCID
PMC2526711
Subset
IM
Grants
NIGMS NIH HHS · R01 GM054728 · United States
NIGMS NIH HHS · GM-54728 · United States
External Links
PubMed source DOI: 10.1091/mbc.e08-02-0160 PMC Full Text View journal details
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