title: Triggered Ca2+ influx is required for extended synaptotagmin 1-induced ER-plasma membrane tethering.
abstract: The extended synaptotagmins (E-Syts) are ER proteins that act as Ca(2+)-regulated tethers between the ER and the plasma membrane (PM) and have a putative role in lipid transport between the two membranes. Ca(2+) regulation of their tethering function, as well as the interplay of their different domains in such function, remains poorly understood. By exposing semi-intact cells to buffers of variable Ca(2+) concentrations, we found that binding of E-Syt1 to the PI(4,5)P2-rich PM critically requires its C2C and C2E domains and that the EC50 of such binding is in the low micromolar Ca(2+) range. Accordingly, E-Syt1 accumulation at ER-PM contact sites occurred only upon experimental manipulations known to achieve these levels of Ca(2+) via its influx from the extracellular medium, such as store-operated Ca(2+) entry in fibroblasts and membrane depolarization in β-cells. We also show that in spite of their very different physiological functions, membrane tethering by E-Syt1 (ER to PM) and by synaptotagmin (secretory vesicles to PM) undergo a similar regulation by plasma membrane lipids and cytosolic Ca(2+).
authors.affiliation: Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT, USA Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT, USA olof.idevall@mcb.uu.se pietro.decamilli@yale.edu.
authors.forename: Olof
authors.initials: O
authors.lastname: Idevall-Hagren
authors.affiliation: Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT, USA Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT, USA.
authors.forename: Alice
authors.initials: A
authors.lastname: Lü
authors.affiliation: Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden.
authors.forename: Beichen
authors.initials: B
authors.lastname: Xie
authors.affiliation: Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT, USA Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT, USA olof.idevall@mcb.uu.se pietro.decamilli@yale.edu.
authors.forename: Pietro
authors.initials: P
authors.lastname: De Camilli
mesh_terms: D000818:Animals; D019556:COS Cells; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D002522:Chlorocebus aethiops; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D050863:Synaptotagmin I / Q000235:genetics / Q000378:metabolism*
chemical_list: D019269:Phosphatidylinositol 4,5-Diphosphate; D050863:Synaptotagmin I; D002118:Calcium
keywords: Orai1; PLC; STIM1; membrane contact sites; tricalbin