TY - JOUR
T1 - Doc2 proteins are not required for the increased spontaneous release rate in synaptotagmin-1-deficient neurons
AU - Díez-Arazola, Rocío
AU - Meijer, Marieke
AU - Bourgeois-Jaarsma, Quentin
AU - Niels Cornelisse, L.
AU - Verhage, Matthijs
AU - Groffen, Alexander J.
N1 - Funding Information: This study was financially supported by the Netherlands Organization for Health Research and Development (ZonMW Projects 91207032, 91113022, and 09150161810052) and the EU in the European Neuroscience Campus Network(Cycle4,Project3).WethankJokeWortel,DesireeSchut,RobbertZalm,JoostHoetjes,IngridSaarloos,and Publisher Copyright: © 2020 the authors
PY - 2020/3/25
Y1 - 2020/3/25
N2 - Regulated secretion is controlled by Ca 2+ sensors with different affinities and subcellular distributions. Inactivation of Syt1 (synaptotagmin-1), the main Ca 2+ sensor for synchronous neurotransmission in many neurons, enhances asynchronous and spontaneous release rates, suggesting that Syt1 inhibits other sensors with higher Ca 2+ affinities and/or lower cooperativities. Such sensors could include Doc2a and Doc2b, which have been implicated in spontaneous and asynchronous neurotransmitter release and compete with Syt1 for binding SNARE complexes. Here, we tested this hypothesis using triple-knock-out mice. Inactivation of Doc2a and Doc2b in Syt1-deficient neurons did not reduce the high spontaneous release rate. Overexpression of Doc2b variants in triple-knock-out neurons reduced spontaneous release but did not rescue synchronous release. A chimeric construct in which the C2AB domain of Syt1 was substituted by that of Doc2b did not support synchronous release either. Conversely, the soluble C2AB domain of Syt1 did not affect spontaneous release. We conclude that the high spontaneous release rate in synaptotagmin-deficient neurons does not involve the binding of Doc2 proteins to Syt1 binding sites in the SNARE complex. Instead, our results suggest that the C2AB domains of Syt1 and Doc2b specifically support synchronous and spontaneous release by separate mechanisms. (Both male and female neurons were studied without sex determination).
AB - Regulated secretion is controlled by Ca 2+ sensors with different affinities and subcellular distributions. Inactivation of Syt1 (synaptotagmin-1), the main Ca 2+ sensor for synchronous neurotransmission in many neurons, enhances asynchronous and spontaneous release rates, suggesting that Syt1 inhibits other sensors with higher Ca 2+ affinities and/or lower cooperativities. Such sensors could include Doc2a and Doc2b, which have been implicated in spontaneous and asynchronous neurotransmitter release and compete with Syt1 for binding SNARE complexes. Here, we tested this hypothesis using triple-knock-out mice. Inactivation of Doc2a and Doc2b in Syt1-deficient neurons did not reduce the high spontaneous release rate. Overexpression of Doc2b variants in triple-knock-out neurons reduced spontaneous release but did not rescue synchronous release. A chimeric construct in which the C2AB domain of Syt1 was substituted by that of Doc2b did not support synchronous release either. Conversely, the soluble C2AB domain of Syt1 did not affect spontaneous release. We conclude that the high spontaneous release rate in synaptotagmin-deficient neurons does not involve the binding of Doc2 proteins to Syt1 binding sites in the SNARE complex. Instead, our results suggest that the C2AB domains of Syt1 and Doc2b specifically support synchronous and spontaneous release by separate mechanisms. (Both male and female neurons were studied without sex determination).
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U2 - https://doi.org/10.1523/JNEUROSCI.0309-19.2020
DO - https://doi.org/10.1523/JNEUROSCI.0309-19.2020
M3 - Article
C2 - 32098902
SN - 0270-6474
VL - 40
SP - 2606
EP - 2617
JO - Journal of neuroscience
JF - Journal of neuroscience
IS - 13
ER -