Ca super(2+)-Dependent Synaptotagmin Binding to SNAP-25 Is Essential for Ca super(2+)-Triggered Exocytosis

Synaptotagmin is a proposed Ca super(2+) sensor on the vesicle for regulated exocytosis and exhibits Ca super(2+)-dependent binding to phospholipids, syntaxin, and SNAP-25 in vitro, but the mechanisms by which Ca super(2+) triggers membrane fusion is uncertain. Previous studies suggested that SNAP-2...

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Published in:Neuron (Cambridge, Mass.) Mass.), 2002-05, Vol.34 (4), p.599-611
Main Authors: Zhang, X, Kim-Miller, MJ, Fukuda, M, Kowalchyk, JA, Martin, TFJ
Format: Article
Language:English
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Summary:Synaptotagmin is a proposed Ca super(2+) sensor on the vesicle for regulated exocytosis and exhibits Ca super(2+)-dependent binding to phospholipids, syntaxin, and SNAP-25 in vitro, but the mechanisms by which Ca super(2+) triggers membrane fusion is uncertain. Previous studies suggested that SNAP-25 plays a role in the Ca super(2+) regulation of secretion. We found that synaptotagmins I and IX associate with SNAP-25 during Ca super(2+)-dependent exocytosis in PC12 cells, and we identified C-terminal amino acids in SNAP-25 (Asp179, Asp186, Asp193) that are required for Ca super(2+)-dependent synaptotagmin binding. Replacement of SNAP-25 in PC12 cells with SNAP-25 containing C-terminal Asp mutations led to a loss-of-function in regulated exocytosis at the Ca super(2+)-dependent fusion step. These results indicate that the Ca super(2+)-dependent interaction of synaptotagmin with SNAP-25 is essential for the Ca super(2+)-dependent triggering of membrane fusion.
ISSN:0896-6273