Mechanism and function of synaptotagmin-mediated membrane apposition
Enfu Hui1, Jon D Gaffaney, Zhao Wang
1Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin, Madison, Wisconsin, USA.
Nature Structural & Molecular Biology
|June 7, 2011
Summary
Synaptotagmin-1 uses Ca(2+) to aggregate membranes via trans interactions, promoting SNARE-mediated fusion. It also directly assembles t-SNARE proteins, driving neurotransmitter release.
Area of Science:
- Neuroscience
- Molecular Biology
- Biochemistry
Background:
- Synaptotagmin-1 acts as a Ca(2+) sensor crucial for synchronous neurotransmitter release.
- Its membrane-aggregating property, a known biochemical function, lacked mechanistic understanding.
- The role of synaptotagmin-1 in membrane fusion and SNARE complex regulation was unclear.
Purpose of the Study:
- To elucidate the mechanism by which synaptotagmin-1 aggregates membranes in response to Ca(2+).
- To determine the functional significance of synaptotagmin-1-mediated membrane aggregation in SNARE-driven membrane fusion.
- To investigate the direct role of synaptotagmin-1 in SNARE protein assembly and fusion competency.
Main Methods:
- Investigated synaptotagmin-1's membrane aggregation mechanism using trans interactions between molecules on separate membranes.
- Correlated Ca(2+)-dependent synaptotagmin-1 aggregation with stimulation of SNARE-mediated membrane fusion.
- Utilized artificial membrane aggregation and a modified fusion assay to assess synaptotagmin-1's role in fusion and SNARE assembly.
Main Results:
- Synaptotagmin-1-mediated vesicle aggregation is driven by trans interactions between synaptotagmin-1 molecules on different membranes.
- Ca(2+)-bound synaptotagmin-1's vesicle aggregation ability strongly correlates with its stimulation of SNARE-mediated fusion.
- Synaptotagmin-1 directly promotes the assembly of individual t-SNARE proteins into fusion-competent heterodimers, independent of aggregation.
Conclusions:
- Ca(2+)-bound synaptotagmin-1 regulates membrane fusion through both membrane aggregation and direct SNARE complex assembly.
- Membrane aggregation and SNARE assembly are key Ca(2+)-regulated aspects of fusion catalyzed by SNAREs.
- Synaptotagmin-1 integrates Ca(2+) signaling with the SNARE machinery to control neurotransmitter release.
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