RT Journal Article
SR Electronic
T1 Vertebrate-specific sequences in the gephyrin E-domain regulate cytosolic aggregation and postsynaptic clustering
JF Journal of Cell Science
JO J. Cell Sci.
FD The Company of Biologists Ltd
SP 1371
OP 1382
DO 10.1242/jcs.003905
VO 120
IS 8
A1 Lardi-Studler, Barbara
A1 Smolinsky, Birthe
A1 Petitjean, Caroline M.
A1 Koenig, Franziska
A1 Sidler, Corinne
A1 Meier, Jochen C.
A1 Fritschy, Jean-Marc
A1 Schwarz, Guenter
YR 2007
UL http://jcs.biologists.org/content/120/8/1371.abstract
AB Gephyrin is a multifunctional protein contributing to molybdenum cofactor (Moco) synthesis and postsynaptic clustering of glycine and GABAA 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 GABAA-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 GABAA 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.