Synaptic scaffolding molecule is involved in the synaptic clustering of neuroligin
Introduction
Synapses are interneuronal cell junctions and have the machinery for cell adhesion. The cell adhesion machinery is composed of cell adhesion molecules (CAMs) and CAM-associated proteins, which link CAMs to the cytoskeleton and assemble various proteins. Synapses have various CAMs, including classic cadherins and neuroligin (Bruses, 2000, Ichtchenko et al., 1995, Yagi and Takeichi, 2000). Neuroligin is a neural cell adhesion molecule, which was identified as a ligand for β-neurexin. Neuroligin is localized at postsynaptic density (PSD) (Song et al., 1999). It mediates heterophilic cell adhesion at synapses through the interaction with neurexin and induces presynaptic development (Dean et al., 2003, Scheiffele et al., 2000). Mutations of human neuroligin genes are implicated in autism and mental retardation (Jamain et al., 2003, Laumonnier et al., 2004). Neuroligin has a PDZ-binding motif at the C-terminus and binds to the PDZ domain of PSD-95 (also called synapse-associated protein 90) (Cho et al., 1992, Irie et al., 1997, Kistner et al., 1993). PSD-95 interacts with N-methyl-d-aspartate receptor (NMDAR) subunits (Kornau et al., 1995). Synaptic scaffolding molecule (S-SCAM) is similar to PSD-95 in a domain organization and also interacts with both of neuroligin and NMDAR subunits (Hirao et al., 1998). We have recently found that β-catenin, a primary partner for classic cadherins, binds S-SCAM, and that the interaction with β-catenin is involved in synaptic localization of S-SCAM. Thereby, S-SCAM is apparently recruited to cadherin-based junction as the first step of synaptic targeting. Because neuroligin is a cell adhesion molecule like cadherins, neuroligin may also position S-SCAM at synapses. However, in our previous study, S-SCAM mutant containing the neuroligin-binding region and lacking the β-catenin-binding region was not recruited to synapses and neuroligin is unlikely to play primary roles to determine synaptic localization of S-SCAM (Nishimura et al., 2002).
To directly address this question, we have here examined whether neuroligin recruits S-SCAM to synapses as β-catenin does or S-SCAM determines synaptic localization of neuroligin. We have also questioned through this study whether S-SCAM and PSD-95 have similar functions in the assembly of synaptic components.
Section snippets
Neuroligin forms large clusters at synapses under co-expression of S-SCAM
When FLAG-neuroligin 1 was expressed by transfection in neurons, it formed small clusters on neurites (Figs. 1Aa and Ba). When HA-S-SCAM was expressed together, FLAG-neuroligin 1 formed larger clusters with HA-S-SCAM (Figs. 1Ab and Bb). Clusters of FLAG-neuroligin 1 alone were close to shafts, and those of FLAG-neuroligin 1 with HA-S-SCAM were protruded from shafts (Fig. 1B). The size of each cluster significantly increased under co-expression of HA-S-SCAM (Figs. 1C and D). Unlike S-SCAM,
Discussion
Neuroligin is a specific ligand of β-neurexin and is localized at postsynaptic membranes (Ichtchenko et al., 1995, Song et al., 1999). Neuroligin binds PSD-95 and S-SCAM at the cytoplasmic tail and interacts with neurexin through the extracellular region (Hirao et al., 1998, Irie et al., 1997). S-SCAM and PSD-95 belong to a family of membrane-associated guanylate kinases and have PDZ and guanylate kinase domains in common (Cho et al., 1992, Hirao et al., 1998, Kistner et al., 1993). S-SCAM has
Antibodies
Rabbit polyclonal anti-S-SCAM, rabbit polyclonal PSD-95, and sheep polyclonal anti-Myc antibodies were described previously (Nishimura et al., 2002). The following antibodies were obtained from commercial sources; mouse monoclonal anti-synaptophysin (Roche Molecular Biochemicals); mouse monoclonal anti-GFP (Santa Cruz Biotechnology); mouse monoclonal anti-PSD-95 (K28/86.2) (Upstate Biotechnology Inc.); rabbit polyclonal anti-synapsin, rabbit polyclonal anti-NMDAR1 and rabbit polyclonal
Acknowledgments
This study was supported by grants-in-aids for Scientific Research (B) and on Priority Areas, and Special Coordination Funds for Promoting Science and Technology from the Ministry of Education, Culture, Sports, Science, and Technology. We thank Dr. Thomas C. Südhof for cDNA of rat neuroligin 1 and Dr. Nils Brose for the monoclonal antibody against neuroligin.
References (42)
- et al.
Role of beta-catenin in synaptic vesicle localization and presynaptic assembly
Neuron
(2003) Cadherin-mediated adhesion at the interneuronal synapse
Curr. Opin. Cell Biol.
(2000)- et al.
The rat brain postsynaptic density fraction contains a homolog of the Drosophila discs-large tumor suppressor protein
Neuron
(1992) - et al.
Characterization of the interaction of a recombinant soluble neuroligin-1 with neurexin-1 beta
J. Biol. Chem.
(2003) - et al.
A model for central synaptic junctional complex formation based on the differential adhesive specificities of the cadherins
Neuron
(1996) - et al.
A novel multiple PDZ domain-containing molecule interacting with N-methyl-d-aspartate receptors and neuronal cell adhesion protein
J. Biol. Chem.
(1998) - et al.
Three isoforms of synaptic scaffolding molecule and their characterization
J. Biol. Chem.
(2000) - et al.
Neuroligin 1: a splice site-specific ligand for β-neurexins
Cell
(1995) - et al.
Interaction of S-SCAM with neural plakophilin-related armadillo-repeat protein/delta-catenin
Biochem. Biophys. Res. Commun.
(1999) - et al.
SAP90, a rat presynaptic protein related to the product of the Drosophila tumor suppressor gene, dlg-A
J. Biol. Chem.
(1993)
X-linked mental retardation and autism are associated with a mutation in the NLGN4 gene, a member of the neuroligin family
Am. J. Hum. Genet.
A multi-protein trafficking complex composed of SAP97, CASK, Veli and Mint1 is associated with inward rectifier Kir2 potassium channels
J. Biol. Chem.
Depolarization drives beta-catenin into neuronal spines promoting changes in synaptic structure and function
Neuron
CRIPT, a novel postsynaptic protein that binds to the third PDZ domain of PSD-95/SAP90
Neuron
Cadherin function is required for axon outgrowth in retinal ganglion cells in vivo
Neuron
Neuroligin expressed in nonneuronal cells triggers presynaptic development in contacting axons
Cell
SAPAPs: a family of PSD-95/SAP90-associated proteins localized at postsynaptic density
J. Biol. Chem.
Molecular modification of N-cadherin in response to synaptic activity
Neuron
A role for the cadherin family of cell adhesion molecules in hippocampal long-term potentiation
Neuron
Cadherin regulates dendritic spine morphogenesis
Neuron
Synaptic adhesion molecules
Curr. Opin. Cell Biol.
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