QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

Vol. 19, Issue 12, 5093-5103, December 2008

This Article Full Text Full Text (PDF) Supplemental Materials All Versions of this Article: E08-03-0235v1 19/12/5093    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Lynch, K. L. Articles by Martin, T. F.J. Search for Related Content PubMed PubMed Citation Articles by Lynch, K. L. Articles by Martin, T. F.J.

Synaptotagmin-1 Utilizes Membrane Bending and SNARE Binding to Drive Fusion Pore Expansion

Kara L. Lynch^*, Roy R.L. Gerona^*, Dana M. Kielar^*, Sascha Martens, Harvey T. McMahon, and Thomas F.J. Martin^*

*Department of Biochemistry, University of Wisconsin, Madison, WI 53706; and Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 2QH, United Kingdom

Submitted March 4, 2008; Revised September 2, 2008; Accepted September 10, 2008
Monitoring Editor: Patrick J. Brennwald

In regulated vesicle exocytosis, SNARE protein complexes drive membrane fusion to connect the vesicle lumen with the extracellular space. The triggering of fusion pore formation by Ca²⁺ is mediated by specific isoforms of synaptotagmin (Syt), which employ both SNARE complex and membrane binding. Ca²⁺ also promotes fusion pore expansion and Syts have been implicated in this process but the mechanisms involved are unclear. We determined the role of Ca²⁺-dependent Syt-effector interactions in fusion pore expansion by expressing Syt-1 mutants selectively altered in Ca²⁺-dependent SNARE binding or in Ca²⁺-dependent membrane insertion in PC12 cells that lack vesicle Syts. The release of different-sized fluorescent peptide-EGFP vesicle cargo or the vesicle capture of different-sized external fluorescent probes was used to assess the extent of fusion pore dilation. We found that PC12 cells expressing partial loss-of-function Syt-1 mutants impaired in Ca²⁺-dependent SNARE binding exhibited reduced fusion pore opening probabilities and reduced fusion pore expansion. Cells with gain-of-function Syt-1 mutants for Ca²⁺-dependent membrane insertion exhibited normal fusion pore opening probabilities but the fusion pores dilated extensively. The results indicate that Syt-1 uses both Ca²⁺-dependent membrane insertion and SNARE binding to drive fusion pore expansion.

Address correspondence to: Thomas F.J. Martin (tfmartin{at}wisc.edu)

This article has been cited by other articles:

				M. Nojiri, K. M. Loyet, V. A. Klenchin, G. Kabachinski, and T. F. J. Martin CAPS Activity in Priming Vesicle Exocytosis Requires CK2 Phosphorylation J. Biol. Chem., July 10, 2009; 284(28): 18707 - 18714. [Abstract] [Full Text] [PDF]