The role of the C2A domain of synaptotagmin 1 in asynchronous neurotransmitter release.
Amino Acid Substitution
Animals
Animals, Genetically Modified
Binding Sites
/ genetics
Calcium
/ metabolism
Drosophila Proteins
/ chemistry
Drosophila melanogaster
/ genetics
Genes, Insect
Mutagenesis, Site-Directed
Neurotransmitter Agents
/ metabolism
Protein Domains
Synaptic Transmission
Synaptic Vesicles
/ metabolism
Synaptotagmin I
/ chemistry
Journal
PloS one
ISSN: 1932-6203
Titre abrégé: PLoS One
Pays: United States
ID NLM: 101285081
Informations de publication
Date de publication:
2020
2020
Historique:
received:
19
02
2020
accepted:
24
04
2020
entrez:
15
5
2020
pubmed:
15
5
2020
medline:
8
8
2020
Statut:
epublish
Résumé
Following nerve stimulation, there are two distinct phases of Ca2+-dependent neurotransmitter release: a fast, synchronous release phase, and a prolonged, asynchronous release phase. Each of these phases is tightly regulated and mediated by distinct mechanisms. Synaptotagmin 1 is the major Ca2+ sensor that triggers fast, synchronous neurotransmitter release upon Ca2+ binding by its C2A and C2B domains. It has also been implicated in the inhibition of asynchronous neurotransmitter release, as blocking Ca2+ binding by the C2A domain of synaptotagmin 1 results in increased asynchronous release. However, the mutation used to block Ca2+ binding in the previous experiments (aspartate to asparagine mutations, sytD-N) had the unintended side effect of mimicking Ca2+ binding, raising the possibility that the increase in asynchronous release was directly caused by ostensibly constitutive Ca2+ binding. Thus, rather than modulating an asynchronous sensor, sytD-N may be mimicking one. To directly test the C2A inhibition hypothesis, we utilized an alternate C2A mutation that we designed to block Ca2+ binding without mimicking it (an aspartate to glutamate mutation, sytD-E). Analysis of both the original sytD-N mutation and our alternate sytD-E mutation at the Drosophila neuromuscular junction showed differential effects on asynchronous release, as well as on synchronous release and the frequency of spontaneous release. Importantly, we found that asynchronous release is not increased in the sytD-E mutant. Thus, our work provides new mechanistic insight into synaptotagmin 1 function during Ca2+-evoked synaptic transmission and demonstrates that Ca2+ binding by the C2A domain of synaptotagmin 1 does not inhibit asynchronous neurotransmitter release in vivo.
Identifiants
pubmed: 32407359
doi: 10.1371/journal.pone.0232991
pii: PONE-D-20-04881
pmc: PMC7224543
doi:
Substances chimiques
Drosophila Proteins
0
Neurotransmitter Agents
0
Synaptotagmin I
0
Calcium
SY7Q814VUP
Types de publication
Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.
Langues
eng
Sous-ensembles de citation
IM
Pagination
e0232991Déclaration de conflit d'intérêts
The authors have declared that no competing interests exist.
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