Spontaneous and evoked synaptic vesicle release arises from a single releasable pool
Junxiu Duan,
Martin Kahms,
Ana Steinhoff,
Jürgen Klingauf
Affiliations
Junxiu Duan
Department of Cellular Biophysics, Institute of Medical Physics and Biophysics, University of Münster, Robert-Koch-Str. 31, 48149 Münster, Germany; Center for Soft Nanoscience SoN, University of Münster, Busso-Peus-Str.10, 48149 Münster, Germany; Cells in Motion Interfaculty Center, University of Münster, 48149 Münster, Germany; CiM Graduate School of the Cells in Motion Interfaculty Centre and the International Max Planck Research School, 48149 Münster, Germany
Martin Kahms
Department of Cellular Biophysics, Institute of Medical Physics and Biophysics, University of Münster, Robert-Koch-Str. 31, 48149 Münster, Germany; Center for Soft Nanoscience SoN, University of Münster, Busso-Peus-Str.10, 48149 Münster, Germany; Cells in Motion Interfaculty Center, University of Münster, 48149 Münster, Germany
Ana Steinhoff
Department of Cellular Biophysics, Institute of Medical Physics and Biophysics, University of Münster, Robert-Koch-Str. 31, 48149 Münster, Germany; Center for Soft Nanoscience SoN, University of Münster, Busso-Peus-Str.10, 48149 Münster, Germany; Cells in Motion Interfaculty Center, University of Münster, 48149 Münster, Germany; CiM Graduate School of the Cells in Motion Interfaculty Centre and the International Max Planck Research School, 48149 Münster, Germany
Jürgen Klingauf
Department of Cellular Biophysics, Institute of Medical Physics and Biophysics, University of Münster, Robert-Koch-Str. 31, 48149 Münster, Germany; Center for Soft Nanoscience SoN, University of Münster, Busso-Peus-Str.10, 48149 Münster, Germany; Cells in Motion Interfaculty Center, University of Münster, 48149 Münster, Germany; Corresponding author
Summary: The quantal content of an evoked postsynaptic response is typically determined by dividing it by the average spontaneous miniature response. However, this approach is challenged by the notion that different synaptic vesicle pools might drive spontaneous and evoked release. Here, we “silence” synaptic vesicles through pharmacological alkalinization and subsequently rescue them by optogenetic acidification. We find that such silenced synaptic vesicles, retrieved during evoked or spontaneous activity, cross-deplete the complementary release mode in a fully reversible manner. A fluorescently tagged version of the endosomal SNARE protein Vti1a, which has been suggested to identify a separate pool of spontaneously recycling synaptic vesicles, is trafficked to synaptic vesicles significantly only upon overexpression but not when endogenously tagged by CRISPR-Cas9. Thus, both release modes draw synaptic vesicles from the same readily releasable pool.
