Calcium-dependent Transmitter Secretion From Fibroblasts: Modulation by Synaptotagmin I

Neuron. 1995 Sep;15(3):689-96. doi: 10.1016/0896-6273(95)90156-6.


Following endocytic uptake of acetylcholine (ACh), CHO fibroblasts exhibit Ca(2+)-dependent spontaneous quantal ACh release and depolarization-evoked ACh release, as detected by a whole-cell voltage-clamped myocyte in contact with the fibroblast. CHO fibroblasts transfected with synaptotagmin I, an integral membrane protein of synaptic vesicles, showed a reduced spontaneous quantal ACh release and an enhanced Ca(2+)-evoked ACh release, as compared with control cells. Biochemical and ultrastructural studies of endocytic activity using horseradish peroxidase as a marker further confirmed the inhibitory action of synaptotagmin I on spontaneous vesicular exocytosis and on elevated exocytosis induced by Ca2+. Through inhibition of exocytosis at the resting intracellular concentration of Ca2+ and removal of the inhibition upon depolarization-induced Ca2+ entry, synaptotagmin I could enhance the efficiency of excitation-secretion coupling.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acetylcholine / metabolism*
  • Adenosine Triphosphate / pharmacology
  • Animals
  • CHO Cells
  • Calcium / pharmacology*
  • Calcium-Binding Proteins*
  • Cells, Cultured
  • Cricetinae
  • Endocytosis / drug effects
  • Exocytosis
  • Fibroblasts / drug effects
  • Fibroblasts / physiology*
  • Fibroblasts / ultrastructure
  • Horseradish Peroxidase / metabolism
  • Membrane Glycoproteins / genetics
  • Membrane Glycoproteins / pharmacology*
  • Microscopy, Electron
  • Muscles / physiology
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / pharmacology*
  • Synaptotagmin I
  • Synaptotagmins
  • Transfection
  • Xenopus


  • Calcium-Binding Proteins
  • Membrane Glycoproteins
  • Nerve Tissue Proteins
  • Synaptotagmin I
  • Synaptotagmins
  • Adenosine Triphosphate
  • Horseradish Peroxidase
  • Acetylcholine
  • Calcium