GluRδ2 assembles four neurexins into trans-synaptic triad to trigger synapse formation
Sung-Jin Lee1, Takeshi Uemura, Tomoyuki Yoshida
1Department of Molecular Neurobiology and Pharmacology, Graduate School of Medicine, University of Tokyo, Tokyo 113-0033, Japan.
Summary
Glutamate receptor δ2 (GluRδ2) tetramers, through cerebellin precursor protein 1 (Cbln1), cluster neurexins (NRXNs) to trigger synapse formation. This molecular mechanism is key for understanding neural wiring and brain function.
Area of Science:
- Neuroscience
- Molecular Biology
- Cell Biology
Background:
- Synapse formation is crucial for neural wiring, higher brain functions, and understanding mental disorders.
- The trans-synaptic interaction involving postsynaptic glutamate receptor δ2 (GluRδ2), presynaptic neurexins (NRXNs), and cerebellin precursor protein 1 (Cbln1) mediates cerebellar synapse formation.
Purpose of the Study:
- To elucidate the molecular mechanisms by which the trans-synaptic triad of GluRδ2, Cbln1, and NRXNs induces synapse formation.
- To determine the stoichiometry and assembly process of the synaptogenic complex.
Main Methods:
- In vitro incubation of cultured mouse cerebellar granule cells (GCs) with purified protein components.
- Analysis of protein-ligand interactions using gel filtration and isothermal titration calorimetry.
- Investigation of Cbln1 mutants to assess binding site specificities.
Main Results:
- Tetrameric GluRδ2, but not dimeric GluRδ2 N-terminal domain (NTD), stimulated presynaptic protein accumulation.
- Binding analyses revealed differential and independent interactions within the GluRδ2-Cbln1-NRXN complex.
- The synaptogenic triad assembles with a stoichiometry of 1:2:4 for tetrameric GluRδ2:hexameric Cbln1:monomeric NRXN.
Conclusions:
- GluRδ2 acts as the primary trigger for synapse formation by initiating the clustering of NRXNs via the Cbln1-mediated triad.
- The specific stoichiometry and assembly mechanism highlight a precise molecular architecture for initiating synaptic connections.
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