J. M. C. and B. B. contributed equally to this work.
Synaptotagmin 1 is required for vesicular Ca2+/H+-antiport activity
Article first published online: 15 MAY 2013
© 2013 International Society for Neurochemistry
Journal of Neurochemistry
Volume 126, Issue 1, pages 37–46, July 2013
How to Cite
J. Neurochem.(2013) 126, 37–46.
- Issue published online: 20 JUN 2013
- Article first published online: 15 MAY 2013
- Accepted manuscript online: 23 APR 2013 02:38AM EST
- Manuscript Accepted: 17 APR 2013
- Manuscript Revised: 16 APR 2013
- Manuscript Received: 29 MAR 2013
- Swiss FNRS. Grant Number: N°31-057135.99.
- European Commission project Lipidiet. Grant Number: QLK1-CT-2002-00172
- Portuguese Foundation for Science and Technology. Grant Number: FSE-POPH-QREN
- PC12 pheochromocytoma cells;
- synaptic vesicles;
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.