Molecular basis of gephyrin clustering at inhibitory synapses: role of G- and E-domain interactions.
Gephyrin is a bifunctional modular protein that, in neurons, clusters glycine receptors and gamma-aminobutyric acid, type A receptors in the postsynaptic membrane of inhibitory synapses. By x-ray crystallography and cross-linking, the N-terminal G-domain of gephyrin has been shown to form trimers and the C-terminal E-domain dimers, respectively. Gephyrin therefore has been proposed to form a hexagonal submembranous lattice onto which inhibitory receptors are anchored. Here, crystal structure-based substitutions at oligomerization interfaces revealed that both G-domain trimerization and E-domain dimerization are essential for the formation of higher order gephyrin oligomers and postsynaptic gephyrin clusters. Insertion of the alternatively spliced C5' cassette into the G-domain inhibited clustering by interfering with trimerization, and mutation of the glycine receptor beta-subunit binding region prevented the localization of the clusters at synaptic sites. Together our findings show that domain interactions mediate gephyrin scaffold formation.
Saiyed
Taslimarif
T
Department of Neurochemistry, Max Planck Institute for Brain Research, Frankfurt, Main, Germany.
Paarmann
Ingo
I
Schmitt
Bertram
B
Haeger
Svenja
S
Sola
Maria
M
Schmalzing
Günther
G
Weissenhorn
Winfried
W
Betz
Heinrich
H
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary / Q000502:physiology; D011963:Receptors, GABA-A / Q000235:genetics / Q000378:metabolism; D018009:Receptors, Glycine / Q000378:metabolism; D013569:Synapses / Q000235:genetics / Q000378:metabolism*; D014981:Xenopus
D002352:Carrier Proteins; D008565:Membrane Proteins; D046912:Multiprotein Complexes; D011963:Receptors, GABA-A; D018009:Receptors, Glycine; C073441:gephyrin