Synaptotagmin 1 is required for vesicular Ca2+/H+-antiport activity

Authors

  • Joao Miguel Cordeiro,

    1. Neurosciences fondamentales, Faculté de Médecine, Université de Genève, Genève, Switzerland
    2. Departamento de Biologia and CESAM, Universidade de Aveiro, Aveiro, Portugal
    Current affiliation:
    1. J. Miguel Cordeiro;Lab. Farmacologia e Neurobiologia, ICBAS, Universidade do Porto, 4050-313 Porto, Portugal
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    • J. M. C. and B. B. contributed equally to this work.
  • Bernadett Boda,

    1. Neurosciences fondamentales, Faculté de Médecine, Université de Genève, Genève, Switzerland
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    • J. M. C. and B. B. contributed equally to this work.
  • Paula P. Gonçalves,

    1. Departamento de Biologia and CESAM, Universidade de Aveiro, Aveiro, Portugal
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  • Yves Dunant

    Corresponding author
    • Neurosciences fondamentales, Faculté de Médecine, Université de Genève, Genève, Switzerland
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Address correspondence and reprint requests to Yves Dunant, Université de Genève, Faculté de Médecine, Centre Médical Universitaire, 1211–Genève 4, Switzerland. E-mail: a_y.dunant@bluewin.ch

Abstract

A low-affinity Ca2+/H+-antiport was described in the membrane of mammalian brain synaptic vesicles. Electrophysiological studies showed that this antiport contributes to the extreme brevity of excitation-release coupling in rapid synapses. Synaptotagmin-1, a vesicular protein interacting with membranes upon low-affinity Ca2+-binding, plays a major role in excitation-release coupling, by synchronizing calcium entry with fast neurotransmitter release. Here, we report that synaptotagmin-1 is necessary for expression of the vesicular Ca2+/H+-antiport. We measured Ca2+/H+-antiport activity in vesicles and granules of pheochromocytoma PC12 cells by three methods: (i) Ca2+-induced dissipation of the vesicular H+-gradient; (ii) bafilomycin-sensitive calcium accumulation and (iii) pH-jump-induced calcium accumulation. The results were congruent and highly significant: Ca2+/H+-antiport activity is detectable only in acidic organelles expressing functional synaptotagmin–1. In contrast, synaptotagmin-1-deficient cells – and cells where transgenically encoded synaptotagmin-1 was acutely photo-inactivated – were devoid of any Ca2+/H+-antiport activity. Therefore, in addition to its previously described functions, synaptotagmin-1 is involved in a rapid vesicular Ca2+ sequestration through a Ca2+/H+ antiport.

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