T. Furuyashiki et al., Citron, a Rho-target, interacts with PSD-95/SAP-90 at glutamatergic synapses in the thalamus, J NEUROSC, 19(1), 1999, pp. 109-118
Proteins of the membrane-associated guanylate kinase family play an importa
nt role in the anchoring and clustering of neurotransmitter receptors in th
e postsynaptic density (PSD) at many central synapses. However, relatively
little is known about how these multifunctional scaffold proteins might pro
vide a privileged site for activity- and cell type-dependent specification
of the postsynaptic signaling machinery. Rho signaling pathway has classica
lly been implicated in mechanisms of axonal outgrowth, dendrogenesis, and c
ell migration during neural development, but its contribution remains uncle
ar at the synapses in the mature CNS. Here, we present evidence that Citron
, a Rho-effector in the brain, is enriched in the PSD fraction and interact
s with PSD-95/synapse-associated protein (SAP)-90 both in vivo and in vitro
. Citron colocalization with PSD-95 occurred, not exclusively but certainly
, at glutamatergic synapses in a limited set of neurons, such as the thalam
ic excitatory neurons; Citron expression, however, could not be detected in
the principal neurons of the hippocampus and the cerebellum in the adult m
ouse brain. In a heterologous system, Citron was shown to form a heteromeri
c complex not only with PSD-95 but also with NMDA receptors. Thus, Citron-P
SD-95/SAP-90 interaction may provide a region- and cell type-specific link
between the Rho signaling cascade and the synaptic NMDA receptor complex.