Regulation of gephyrin assembly and glycine receptor synaptic stability.
Gephyrin is required for the formation of clusters of the glycine receptor (GlyR) in the neuronal postsynaptic membrane. It can make trimers and dimers through its N- and C-terminal G and E domains, respectively. Gephyrin oligomerization could thus create a submembrane lattice providing GlyR-binding sites. We investigated the relationships between the stability of cell surface GlyR and the ability of gephyrin splice variants to form oligomers. Using truncated and full-length gephyrins we found that the 13-amino acid sequence (cassette 5) prevents G domain trimerization. Moreover, E domain dimerization is inhibited by the gephyrin central L domain. All of the gephyrin variants bind GlyR beta subunit cytoplasmic loop with high affinity regardless of their cassette composition. Coexpression experiments in COS-7 cells demonstrated that GlyR bound to gephyrin harboring cassette 5 cannot be stabilized at the cell surface. This gephyrin variant was found to deplete synapses from both GlyR and gephyrin in transfected neurons. These data suggest that the relative expression level of cellular variants influence the overall oligomerization pattern of gephyrin and thus the turnover of synaptic GlyR.
Bedet
Cécile
C
INSERM U789, the Laboratoire de Biologie Cellulaire de la Synapse, Ecole Normale Supérieure, F-75005, Paris, France.
Bruusgaard
Jo C
JC
Vergo
Sandra
S
Groth-Pedersen
Line
L
Eimer
Stefan
S
Triller
Antoine
A
Vannier
Christian
C
D000818:Animals; D019556:COS Cells; D002352:Carrier Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D008565:Membrane Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D009474:Neurons / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018009:Receptors, Glycine / Q000737:chemistry / Q000378:metabolism*; D013569:Synapses / Q000737:chemistry / Q000378:metabolism*
D002352:Carrier Proteins; D008565:Membrane Proteins; D018009:Receptors, Glycine; C073441:gephyrin