Ca2+ and N-Ethylmaleimide-sensitive Factor Differentially Regulate Disassembly of SNARE Complexes on Early Endosomes
| Autor: | Wei Sun, James A. McNew, Andrew J. Bean, Qing Yan, Thomas A. Vida |
|---|---|
| Rok vydání: | 2004 |
| Předmět: |
Synaptosomal-Associated Protein 25
Endosome Vesicular Transport Proteins Nerve Tissue Proteins Endosome lumen Endosomes Membrane Fusion Biochemistry R-SNARE Proteins chemistry.chemical_compound Humans Receptor N-Ethylmaleimide-Sensitive Proteins Molecular Biology Endosomal Sorting Complexes Required for Transport Endosomal membrane Qa-SNARE Proteins N-Ethylmaleimide Membrane Proteins Bafilomycin Cell Biology Phosphoproteins Cell biology Membrane chemistry Calcium Carrier Proteins SNARE Proteins SNARE complex HeLa Cells Protein Binding |
| Zdroj: | Journal of Biological Chemistry. 279:18270-18276 |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.m400093200 |
| Popis: | The endosome-associated protein Hrs inhibits the homotypic fusion of early endosomes. A helical region of Hrs containing a Q-SNARE motif mediates this effect as well as its endosomal membrane association via SNAP-25, an endosomal receptor for Hrs. Hrs inhibits formation of an early endosomal SNARE complex by displacing VAMP-2 from the complex, suggesting a mechanism by which Hrs inhibits early endosome fusion. We examined the regulation of endosomal SNARE complexes to probe how Hrs may function as a negative regulator. We show that although NSF dissociates the VAMP-2.SNAP-25.syntaxin 13 complex, it has no effect on the Hrs-containing complex. Whereas Ca(2+) dissociates the Hrs-containing complex but not the VAMP-2-containing SNARE complex. This is the first demonstration of differential regulation of R/Q-SNARE and all Q-SNARE-containing SNARE complexes. Ca(2+) also reverses the Hrs-induced inhibition of early endosome fusion in a tetanus toxin-sensitive manner and removes Hrs from early endosomal membranes. Moreover, Hrs inhibition of endosome fusion and its endosomal localization are sensitive to bafilomycin, implying a role for luminal Ca(2+). Thus, Hrs may bind a SNARE protein on early endosomal membranes negatively regulating trans-SNARE pairing and endosomal fusion. The release of Ca(2+) from the endosome lumen dissociates Hrs, allowing a VAMP-2-containing complex to form enabling fusion. |
| Databáze: | OpenAIRE |
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