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A specific negatively charged sequence confers intramolecular regulation on Munc13-1 function in synaptic exocytosis
Kexu Zhao1, Li Zhang2, Mengshi Lei1
1Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.
Summary
Munc13-1
Area of Science:
- Neuroscience
- Cell Biology
- Molecular Biology
Background:
- Munc13 proteins regulate neurotransmitter and hormone secretion via SNARE complex assembly.
- Neuronal Munc13 isoforms have N-terminal regions critical for neurotransmitter release and plasticity, but their function is unclear.
Purpose of the Study:
- To investigate the function of a novel N-terminal sequence in Munc13-1 and its role in regulating neurotransmitter release.
Main Methods:
- Identified a negatively charged polyE sequence in Munc13-1.
- Investigated polyE binding to the MUN domain and its effect on SNARE complex assembly.
- Utilized pseudophosphorylated mutations to disrupt polyE-MUN interaction.
- Assessed the impact of Ca2+ ions on polyE-MUN interaction and Munc13-1 activity.
Main Results:
- A Munc13-1 specific polyE sequence inhibits MUN domain activity through charge-charge interactions.
- Disrupting the polyE-MUN interaction enhances neurotransmitter release.
- Calcium ions (Ca2+) bind to polyE, competing with MUN and reducing inhibition at physiologically relevant concentrations.
Conclusions:
- Munc13-1 exists in an autoinhibited state via the polyE-MUN interaction.
- Presynaptic Ca2+ influx and/or MUN domain modifications relieve this autoinhibition, facilitating neurotransmitter release and short-term plasticity.
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