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Synaptotagmin IV regulates glial glutamate release
Qi Zhang1, Mitsunori Fukuda, Elisabeth Van Bockstaele
1Department of Neuroscience, Room 215, Stemmler Hall, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
Summary
Calcium-binding synaptotagmin IV (Syt IV) is found in brain astrocytes and regulates glutamate release. This suggests Syt IV-mediated gliotransmission plays a role in hippocampus-dependent memory.
Area of Science:
- Neuroscience
- Molecular Biology
- Cell Biology
Background:
- Calcium-binding synaptotagmins (Syts) are conserved membrane proteins, with Syt I known for synaptic transmission.
- Syt IV is upregulated by neuronal activity and linked to motor and memory deficits, but its function is unclear.
Purpose of the Study:
- To investigate the function and localization of Syt IV in the brain.
- To explore the role of Syt IV in glial cells and its contribution to synaptic regulation and memory.
Main Methods:
- Screening of Syts I-XIII for brain enrichment.
- Localization studies of Syt IV in astroglia.
- RNA interference to reduce Syt IV in astrocytes.
- Analysis of Ca(2+)-dependent glutamate release and gliotransmission.
- Functional assessment in Syt IV knockout mice.
Main Results:
- Syt IV is localized in astroglial processes, not presynaptic terminals.
- Reduced Syt IV in astrocytes impairs Ca(2+)-dependent glutamate release (gliotransmission).
- Syt IV C2B domain mutants inhibit Ca(2+)-regulated, but not osmolarity-induced, glial glutamate release.
- Syt IV knockout mice show hippocampus-dependent memory deficits.
Conclusions:
- Syt IV is predominantly expressed in astrocytes and mediates Ca(2+)-regulated gliotransmission.
- Syt IV-dependent gliotransmission is a novel pathway potentially contributing to hippocampus-based memory formation and function.