title: PtdInsP2and PtdSer cooperate to trap synaptotagmin-1 to the plasma membrane in the presence of calcium.
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 (fromRattus norvegicusand expressed inEscherichia coli) binds to PtdIns(4,5)P2via a polybasic lysine patch in the C2B domain, which may promote the priming or 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 an increase in the affinity of the polybasic lysine patch to phosphatidylinositol-4,5-bisphosphate (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.
authors: Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
authors: Ángel
authors: 0000-0002-2736-3501
authors: Á
authors: Pérez-Lara
authors: Department of Chemistry and Center for Membrane Biology, University of Virginia, Charlottesville, United States.
authors: Anusa
authors: A
authors: Thapa
authors: Department of Chemistry and Center for Membrane Biology, University of Virginia, Charlottesville, United States.
authors: Sarah B
authors: SB
authors: Nyenhuis
authors: Department of Chemistry and Center for Membrane Biology, University of Virginia, Charlottesville, United States.
authors: David A
authors: DA
authors: Nyenhuis
authors: Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
authors: Partho
authors: P
authors: Halder
authors: Department of Molecular Enzymology, Göttingen Center for Molecular Biosciences, Georg-August University Göttingen, Göttingen, Germany.
authors: Michael
authors: M
authors: Tietzel
authors: Department of Molecular Enzymology, Göttingen Center for Molecular Biosciences, Georg-August University Göttingen, Göttingen, Germany.
authors: Kai
authors: K
authors: Tittmann
authors: Department of Chemistry and Center for Membrane Biology, University of Virginia, Charlottesville, United States.
authors: David S
authors: DS
authors: Cafiso
authors: Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
authors: Reinhard
authors: 0000-0003-1542-3498
authors: R
authors: Jahn
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D010718:Phosphatidylserines / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D050863:Synaptotagmin I / Q000235:genetics / Q000378:metabolism*
chemical_list: D019269:Phosphatidylinositol 4,5-Diphosphate; D010718:Phosphatidylserines; D011994:Recombinant Proteins; D050863:Synaptotagmin I; D002118:Calcium
keywords: E. coli; biophysics; exocytosis; kinetics; neuroscience; rat; structural biology; synaptotagmin; thermodynamics