Synaptic neuropeptide release induced by octopamine without Ca2+ entry into the nerve terminal
Dinara Shakiryanova1, Geoffrey M Zettel, Tingting Gu
1Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA.
Summary
Octopamine triggers neuropeptide release from Drosophila neurons without external calcium. This process relies on cAMP-dependent protein kinase and internal calcium stores, not just calcium entry.
Area of Science:
- Neuroscience
- Molecular Biology
- Cellular Signaling
Background:
- Synaptic neurotransmitter release typically depends on calcium influx into nerve terminals.
- Neuropeptide release mechanisms are less understood, especially under conditions lacking extracellular calcium.
Purpose of the Study:
- To investigate the mechanism of octopamine-evoked neuropeptide release in Drosophila motoneurons.
- To determine the role of calcium and cyclic AMP signaling pathways in this non-canonical release process.
Main Methods:
- Utilized genetic and pharmacological approaches in Drosophila.
- Investigated the involvement of extracellular and intracellular calcium sources.
- Assessed the contribution of cAMP-dependent signaling pathways, including protein kinase and EPAC.
Main Results:
- Octopamine robustly evoked neuropeptide release independently of extracellular calcium.
- The process critically required cAMP-dependent protein kinase activation.
- Endoplasmic reticulum calcium release, mediated by ryanodine and IP3 receptors, was essential.
- EPAC (exchange protein activated by cAMP) played a minor role.
Conclusions:
- Octopamine-evoked neuropeptide release in Drosophila motoneurons bypasses the need for extracellular calcium.
- This release is driven by a synergistic signaling cascade involving cAMP-dependent protein kinase and intracellular calcium mobilization.
- Highlights a novel neuromodulatory mechanism for synaptic transmission.
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