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

Item Type:Article
Title:Vertebrate-specific sequences in the gephyrin E-domain regulate cytosolic aggregation and postsynaptic clustering
Creators Name:Lardi-Studler, B. and Smolinsky, B. and Petitjean, C.M. and Koenig, F. and Sidler, C. and Meier, J.C. and Fritschy, J.M. and Schwarz, G.
Abstract:Gephyrin is a multifunctional protein contributing to molybdenum cofactor (Moco) synthesis and postsynaptic clustering of glycine and GABA(A) receptors. It contains three major functional domains (G-C-E) and forms cytosolic aggregates and postsynaptic clusters by unknown mechanisms. Here, structural determinants of gephyrin aggregation and clustering were investigated by neuronal transfection of EGFP-tagged deletion and mutant gephyrin constructs. EGFP-gephyrin formed postsynaptic clusters containing endogenous gephyrin and GABA(A)-receptors. Isolated GC- or E-domains failed to aggregate and exerted dominant-negative effects on endogenous gephyrin clustering. A construct interfering with intermolecular E-domain dimerization readily auto-aggregated but showed impaired postsynaptic clustering. Finally, two mutant constructs with substitution of vertebrate-specific E-domain sequences with homologue bacterial MoeA sequences uncovered a region crucial for gephyrin clustering. One construct failed to aggregate, but retained Moco biosynthesis capacity, demonstrating the independence of gephyrin enzymatic activity and aggregation. Reinserting two vertebrate-specific residues restored gephyrin aggregation and increased formation of postsynaptic clusters containing GABA(A) receptors at the expense of PSD-95 clusters - a marker of glutamatergic synapses. These results underscore the key role of specific E-domain regions distinct from the known dimerization interface for controlling gephyrin aggregation and postsynaptic clustering and suggest that formation of gephyrin clusters influences the homeostatic balance between inhibitory and excitatory synapses.
Keywords:Inhibitory neurotransmission, GABAergic synapse, GABAA receptors, Glycine receptors, Postsynaptic density, Gene transfection, Animals, Rats
Source:Journal of Cell Science
Publisher:Company of Biologists
Number:Pt 8
Page Range:1371-1382
Date:15 April 2007
Official Publication:https://doi.org/10.1242/jcs.003905
PubMed:View item in PubMed

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