Vertebrate-specific sequences in the gephyrin E-domain regulate cytosolic aggregation and postsynaptic clustering

Area of Science:

• Neuroscience
• Molecular Biology
• Synaptic Plasticity

Background:

• Gephyrin is crucial for Moco synthesis and inhibitory receptor clustering.
• Its aggregation and clustering mechanisms are poorly understood.
• Gephyrin has three domains: G, C, and E.

Purpose of the Study:

• Investigate structural determinants of gephyrin aggregation and clustering.
• Identify regions critical for postsynaptic clustering.
• Understand the relationship between gephyrin enzymatic activity and aggregation.

Main Methods:

• Neuronal transfection of EGFP-tagged gephyrin deletion and mutant constructs.
• Analysis of gephyrin aggregation and postsynaptic clustering.
• Substitution of vertebrate E-domain sequences with bacterial MoeA sequences.

Main Results:

• EGFP-gephyrin formed postsynaptic clusters with endogenous gephyrin and GABA(A)-receptors.
• Isolated domains failed to aggregate; E-domain dimerization interference caused aggregation but impaired clustering.
• Mutant constructs identified a key region for gephyrin clustering, independent of Moco synthesis.
• Restoring vertebrate-specific residues enhanced gephyrin aggregation and GABA(A) receptor clusters, reducing PSD-95 clusters.

Conclusions:

• Specific E-domain regions, distinct from the dimerization interface, control gephyrin aggregation and clustering.
• Gephyrin aggregation is independent of its Moco biosynthesis enzymatic activity.
• Gephyrin cluster formation influences the balance between inhibitory and excitatory synapses.