title: Synaptotagmin-1 binds to PIP(2)-containing membrane but not to SNAREs at physiological ionic strength.
abstract: The Ca(2+) sensor synaptotagmin-1 is thought to trigger membrane fusion by binding to acidic membrane lipids and SNARE proteins. Previous work has shown that binding is mediated by electrostatic interactions that are sensitive to the ionic environment. However, the influence of divalent or polyvalent ions, at physiological concentrations, on synaptotagmin's binding to membranes or SNAREs has not been explored. Here we show that binding of rat synaptotagmin-1 to membranes containing phosphatidylinositol 4,5-bisphosphate (PIP2) is regulated by charge shielding caused by the presence of divalent cations. Surprisingly, polyvalent ions such as ATP and Mg(2+) completely abrogate synaptotagmin-1 binding to SNAREs regardless of the presence of Ca(2+). Altogether, our data indicate that at physiological ion concentrations Ca(2+)-dependent synaptotagmin-1 binding is confined to PIP2-containing membrane patches in the plasma membrane, suggesting that membrane interaction of synaptotagmin-1 rather than SNARE binding triggers exocytosis of vesicles.
authors.affiliation: Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.
authors.forename: Yongsoo
authors.identifier: http://orcid.org/0000-0001-8336-8051
authors.initials: Y
authors.lastname: Park
authors.affiliation: Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA.
authors.forename: Jong Bae
authors.initials: JB
authors.lastname: Seo
authors.affiliation: Department of Chemistry, Center for Membrane Biology, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Alicia
authors.initials: A
authors.lastname: Fraind
authors.affiliation: Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.
authors.forename: Angel
authors.initials: A
authors.lastname: Pérez-Lara
authors.affiliation: Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.
authors.forename: Halenur
authors.initials: H
authors.lastname: Yavuz
authors.affiliation: Department of Physics and Astronomy, Center for Theoretical Physics, Seoul National University, Seoul, Republic of Korea.
authors.forename: Kyungreem
authors.initials: K
authors.lastname: Han
authors.affiliation: Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA.
authors.forename: Seung-Ryoung
authors.initials: SR
authors.lastname: Jung
authors.affiliation: Biomolecular Spectroscopy and Single-Molecule Detection Research Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
authors.forename: Iman
authors.initials: I
authors.lastname: Kattan
authors.affiliation: Biomolecular Spectroscopy and Single-Molecule Detection Research Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.|Department of Biophysical Chemistry, Institute for Physical and Theoretical Chemistry, University of Braunschweig, Braunschweig, Germany.
authors.forename: Peter Jomo
authors.initials: PJ
authors.lastname: Walla
authors.affiliation: Department of Physics and Astronomy, Center for Theoretical Physics, Seoul National University, Seoul, Republic of Korea.
authors.forename: MooYoung
authors.initials: M
authors.lastname: Choi
authors.affiliation: Department of Chemistry, Center for Membrane Biology, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: David S
authors.initials: DS
authors.lastname: Cafiso
authors.affiliation: Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA.
authors.forename: Duk-Su
authors.initials: DS
authors.lastname: Koh
authors.affiliation: Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Jahn
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002413:Cations, Divalent / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D002837:Chromaffin Granules / Q000378:metabolism; D002852:Chromatography, Ion Exchange; D005089:Exocytosis / Q000502:physiology*; D005454:Fluorescence Polarization; D031541:Fluorescence Resonance Energy Transfer; D008958:Models, Molecular; D008962:Models, Theoretical; D018408:Patch-Clamp Techniques; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D011487:Protein Conformation; D051381:Rats; D050600:SNARE Proteins / Q000378:metabolism; D013057:Spectrum Analysis; D050863:Synaptotagmin I / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D002413:Cations, Divalent; D019269:Phosphatidylinositol 4,5-Diphosphate; D050600:SNARE Proteins; D050863:Synaptotagmin I; C494312:Syt1 protein, rat; D002118:Calcium