Intramolecular domain dynamics regulate synaptic MAGUK protein interactions.

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Postsynaptic density-95 (PSD-95) is a MAGUK family scaffold protein crucial for organizing synaptic transmission.
• Its multi-domain structure, featuring PDZ and SH3-GK domains, facilitates the assembly of protein complexes at synapses.

Purpose of the Study:

• To investigate how ligand binding to PSD-95's PDZ domains influences its intramolecular structure and subsequent complex formation.
• To identify novel PSD-95 interactors and elucidate the hierarchical mechanism of PSD-95 complex assembly.

Main Methods:

• Utilized CRIPT-derived PDZ3 ligands to probe PSD-95 structure-function relationships.
• Employed biochemical assays to identify and characterize PSD-95 interactors.
• Investigated protein complex formation in rat hippocampal neurons.

Main Results:

• Binding of PDZ3 ligands to PSD-95's third PDZ domain induces conformational changes in the SH3-GK tandem domain.
• Identified context-dependent binding of PSD-95 interactors to the SH3-GK domain.
• Established Gnb5 (G protein subunit beta 5) as a PSD-95 interactor at dendritic spines, with binding mediated by the PSD-95 GK domain and triggered by PDZ3 ligand interaction.

Conclusions:

• PSD-95 complex formation is regulated by a hierarchical binding mechanism initiated by ligand engagement with PDZ domains.
• Conformational changes in PSD-95 dictate its interaction with downstream partners like Gnb5, influencing synaptic organization.