PtdInsP2 and PtdSer cooperate to trap synaptotagmin-1 to the plasma membrane in the presence of calcium

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Abstract

The Ca²⁺-sensor synaptotagmin-1 that triggers neuronal exocytosis binds to negatively charged membrane lipids (mainly phosphatidylserine, PtdSer, and phosphoinositides, PtdIns) but the molecular details of this process are not fully understood. Using quantitative thermodynamic, kinetic and structural methods we show that synaptotagmin-1 (from Rattus norvegicus and expressed in E.coli) binds to PtdIns(4,5)P₂ via a polybasic lysine patch in the C2B domain, which may promote priming/docking of synaptic vesicles. Ca²⁺ neutralizes the negative charges of the Ca²⁺ binding sites, resulting in the penetration of synaptotagmin-1 into the membrane, via binding of PtdSer, and the increase of the affinity of the polybasic lysine patch to PtdIns(4,5)P₂. These Ca²⁺-induced events decrease the dissociation rate of synaptotagmin-1 membrane binding while the association rate remains unchanged. We conclude that both membrane penetration and the increased residence time of synaptotagmin-1 at the plasma membrane are crucial for triggering exocytotic membrane fusion.

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Ángel Pérez-Lara

Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany

Competing interests
No competing interests declared.

"This ORCID iD identifies the author of this article:" 0000-0002-2736-3501
Anusa Thapa

Department of Chemistry and Center for Membrane Biology, University of Virginia, Charlottesville, United States

Competing interests
No competing interests declared.
Sarah B Nyenhuis

Department of Chemistry and Center for Membrane Biology, University of Virginia, Charlottesville, United States

Competing interests
No competing interests declared.
David A Nyenhuis

Department of Chemistry and Center for Membrane Biology, University of Virginia, Charlottesville, United States

Competing interests
No competing interests declared.
Partho Halder

Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany

Competing interests
No competing interests declared.
Michael Tietzel

Department of Molecular Enzymology, Göttingen Center for Molecular Biosciences, Georg-August University Göttingen, Göttingen, Germany

Competing interests
No competing interests declared.
Kai Tittmann

Department of Molecular Enzymology, Göttingen Center for Molecular Biosciences, Georg-August University, Göttingen, Germany

Competing interests
No competing interests declared.
David S Cafiso

Department of Chemistry and Center for Membrane Biology, University of Virginia, Charlottesville, United States

For correspondence
cafiso@virginia.edu

Competing interests
No competing interests declared.
Reinhard Jahn

Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany

For correspondence
rjahn@gwdg.de

Competing interests
Reinhard Jahn, Reviewing editor, eLife.

"This ORCID iD identifies the author of this article:" 0000-0003-1542-3498

Funding

National Institutes of Health (P01 GM072694)

David S Cafiso
Reinhard Jahn

Deutsche Forschungsgemeinschaft (SFB803)

Ángel Pérez-Lara
Partho Halder
Reinhard Jahn

Max-Planck-Gesellschaft (Postdoctoral Fellowship)

Ángel Pérez-Lara
Partho Halder

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

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