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The septin Sept5/CDCrel-1 competes with alpha-SNAP for binding to the SNARE complex
Crestina L Beites1, Kristen A Campbell, William S Trimble
1Programme in Cell Biology, Hospital for Sick Children, 555 University Avenue, Toronto, Canada M5G 1X8.
The Biochemical Journal
|September 10, 2004
Summary
Septin 5 (Sept5) interacts with syntaxin 1A, a SNARE protein, potentially regulating vesicle fusion. This interaction, dependent on the SNARE complex, suggests Sept5 as a novel regulator of exocytosis in the brain.
Area of Science:
- Cell biology
- Neuroscience
- Protein interactions
Background:
- Soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor (SNARE) proteins mediate vesicle fusion.
- Regulation of SNARE-mediated exocytosis is not fully understood.
- Septins are a conserved family of proteins with largely unknown functions in mammals.
Purpose of the Study:
- Identify novel regulators of SNARE proteins.
- Investigate the interaction between septin 5 (Sept5) and syntaxin 1A.
- Elucidate the role of Sept5 in regulating exocytosis.
Main Methods:
- Protein interaction mapping to identify Sept5 domains for syntaxin binding.
- Analysis of Sept5 binding to syntaxin within different protein complexes (nSec1-syntaxin, SNARE complex, 7 S complex).
Main Results:
- Septin 5 (Sept5) binds to the SNARE domain of syntaxin 1A.
- Sept5 binding to syntaxin is dependent on the formation of a SNARE complex.
- Sept5 cannot bind to syntaxin when it is part of an nSec1-syntaxin complex.
- Alpha-SNAP binding to the SNARE complex occludes Sept5 interaction.
Conclusions:
- Septin 5 (Sept5) is a novel SNARE-interacting protein predominantly expressed in the brain.
- Sept5 may regulate exocytosis by modulating the availability of SNARE proteins through its interaction with syntaxin 1A.
- The interaction of Sept5 with syntaxin is regulated by the assembly state of the SNARE complex.