1. Cis- and frans-membrane interactions of synaptotagmin-1.
- Author
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Vennekate, Wensi, Schröder, Sabrina, Lin, Chao-Chen, van den Bogaart, Geert, Grunwald, Matthias, Jahn, Reinhard, and Walla, Peter Jomo
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SYNAPTOTAGMINS ,NEURAL transmission ,CELL membranes ,NEURONS ,BINDING sites ,COMPETITION (Biology) ,NEUROBIOLOGY ,FLUORESCENCE spectroscopy - Abstract
In neurotransmission synaptotagmin-1 tethers synaptic vesicles to the presynaptic plasma membrane by binding to acidic membrane lipids and SNAREs and promotes rapid SNARE-mediated fusion upon Ca
2+ triggering. However, recent studies suggested that upon membrane contact synaptotagmin may not only bind in trans to the target membrane but also in eis to its own membrane. Using a sensitive membrane tethering assay we have now dissected the structural requirements and concentration ranges for Ca2+ -dependent and -independent c/s-binding and trans-tethering in the presence and absence of acidic phospholipids and SNAREs. Using variants of membrane-anchored synaptotagmin in which the Ca2+ -binding sites in the C2 domains and a basic cluster involved in membrane binding were disrupted we show that Ca2+ -depen-dent c/s-binding prevents trans-interactions if the c;'s-membrane contains 12-20% anionic phospholipids. Similarly, no trans-interactions were observable using soluble C2AB-domain fragments at comparable concentrations. At saturating concentrations, however, tethering was observed with soluble C2AB domains, probably due to crowding on the vesicle surface and competition for binding sites. We conclude that trans-interactions of synaptotagmin considered to be essential for its function are controlled by a delicate balance between eis- and trans-binding, which may play an important modulatory role in synaptic transmission. [ABSTRACT FROM AUTHOR]- Published
- 2012
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