The secretory granule protein syncollin binds to syntaxin in a Ca2(+)-sensitive manner

The membrane proteins synaptobrevin, syntaxin, and SNAP-25 form the core of a ubiquitous fusion machine that interacts with the soluble proteins NSF and alpha-SNAP. During regulated exocytosis, membrane fusion is usually strictly controlled by Ca2+ ions. However, the mechanism by which Ca2+ regulate...

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Bibliographic Details
Published in:Cell 1997-07, Vol.90 (2), p.325-333
Main Authors: Edwardson, J M, An, S, Jahn, R
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
Calcium - pharmacology
Carrier Proteins - analysis
Carrier Proteins - genetics
Carrier Proteins - metabolism
Cell Membrane - chemistry
Cell Membrane - metabolism
Cloning, Molecular
Cytoplasmic Granules - chemistry
Cytoplasmic Granules - metabolism
Detergents
Enzyme Precursors - metabolism
Exocytosis - physiology
Isomerism
Membrane Proteins - analysis
Membrane Proteins - chemistry
Membrane Proteins - genetics
Membrane Proteins - metabolism
Molecular Sequence Data
Nerve Tissue Proteins - metabolism
Octoxynol
Protein Binding - drug effects
Qa-SNARE Proteins
Rats
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Summary:The membrane proteins synaptobrevin, syntaxin, and SNAP-25 form the core of a ubiquitous fusion machine that interacts with the soluble proteins NSF and alpha-SNAP. During regulated exocytosis, membrane fusion is usually strictly controlled by Ca2+ ions. However, the mechanism by which Ca2+ regulates exocytosis is still unclear. Here we show that the membranes of exocrine secretory granules contain an 18-kDa protein, syncollin, that binds to syntaxin at low Ca2+ concentrations and dissociates at concentrations known to stimulate exocytosis. Syncollin has a single hydrophobic domain at its N-terminus and shows no significant homology with any known protein. Recombinant syncollin inhibits fusion in vitro between zymogen granules and pancreatic plasma membranes, and its potency falls as Ca2+ concentration rises. We suggest that syncollin acts as a Ca2(+)-sensitive regulator of exocytosis in exocrine tissues.
ISSN:0092-8674
DOI:10.1016/S0092-8674(00)80340-2