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Elife. 2017 Aug 29;6. pii: e27441. doi: 10.7554/eLife.27441.

Circular oligomerization is an intrinsic property of synaptotagmin.

Author information

1
Departments of Cell Biology, Yale University School of Medicine, New Haven, United States.
2
Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, United Kingdom.
3
Departments of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, United States.
4
Laboratoire de Physique Statistique, UMR CNRS 8550 Associée aux Universités Paris 6 et Paris 7, Paris, France.

Abstract

Previously, we showed that synaptotagmin1 (Syt1) forms Ca2+-sensitive ring-like oligomers on membranes containing acidic lipids and proposed a potential role in regulating neurotransmitter release (Zanetti et al., 2016). Here, we report that Syt1 assembles into similar ring-like oligomers in solution when triggered by naturally occurring polyphosphates (PIP2 and ATP) and magnesium ions (Mg2+). These soluble Syt1 rings were observed by electron microscopy and independently demonstrated and quantified using fluorescence correlation spectroscopy. Oligomerization is triggered when polyphosphates bind to the polylysine patch in C2B domain and is stabilized by Mg2+, which neutralizes the Ca2+-binding aspartic acids that likely contribute to the C2B interface in the oligomer. Overall, our data show that ring-like polymerization is an intrinsic property of Syt1 with reasonable affinity that can be triggered by the vesicle docking C2B-PIP2 interaction and raise the possibility that Syt1 rings could pre-form on the synaptic vesicle to facilitate docking.

KEYWORDS:

E. coli; electron microscopy; membrane fusion; neuroscience; neurotransmitters

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