Ca2+ and N-ethylmaleimide-sensitive factor differentially regulate disassembly of SNARE complexes on early endosomes.
J Biol Chem
; 279(18): 18270-6, 2004 Apr 30.
Article
em En
| MEDLINE
| ID: mdl-14769786
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.
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Base de dados:
MEDLINE
Assunto principal:
Fosfoproteínas
/
Endossomos
/
Proteínas de Transporte
/
Cálcio
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Proteínas de Transporte Vesicular
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Proteínas de Membrana
Idioma:
En
Ano de publicação:
2004
Tipo de documento:
Article