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Nature Research, Nature Structural and Molecular Biology, 7(18), p. 805-812, 2011

DOI: 10.1038/nsmb.2061

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Synaptotagmin-1 may be a distance regulator acting upstream of SNARE nucleation

Journal article published in 2011 by Geert van den Bogaart, Geert van den Bogaart ORCID, Shashi Thutupalli, Jelger H. Risselada, Karsten Meyenberg, Matthew Holt ORCID, Dietmar Riedel, Ulf Diederichsen, Stephan Herminghaus, Helmut Grubmüller, Reinhard Jahn
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

Synaptotagmin-1 triggers Ca(2+)-sensitive, rapid neurotransmitter release by promoting interactions between SNARE proteins on synaptic vesicles and the plasma membrane. How synaptotagmin-1 promotes this interaction is unclear, and the massive increase in membrane fusion efficiency of Ca(2+)-bound synaptotagmin-1 has not been reproduced in vitro. However, previous experiments have been performed at relatively high salt concentrations, screening potentially important electrostatic interactions. Using functional reconstitution in liposomes, we show here that at low ionic strength SNARE-mediated membrane fusion becomes strictly dependent on both Ca(2+) and synaptotagmin-1. Under these conditions, synaptotagmin-1 functions as a distance regulator that tethers the liposomes too far from the plasma membrane for SNARE nucleation in the absence of Ca(2+), but while bringing the liposomes close enough for membrane fusion in the presence of Ca(2+). These results may explain how the relatively weak electrostatic interactions between synaptotagmin-1 and membranes substantially accelerate fusion.