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Keywords:

  • dystroglycan;
  • inhibitory synapse;
  • neuroligin

Abstract

Synaptic scaffolding molecule (S-SCAM) is a synaptic protein, which harbors five or six PSD-95/Discs large/ZO-1 (PDZ), a guanylate kinase and two WW domains. It interacts with NMDA receptor subunits, neuroligin and β-catenin, and is involved in the accumulation of neuroligin at excitatory synapses. In this study, we have demonstrated S-SCAM is localized at inhibitory synapses in rat primary cultured hippocampal neurons. We have identified β-dystroglycan (β-DG) as a binding partner for S-SCAM at inhibitory synapses. WW domains of S-SCAM bind to three sequences of β-DG. We have also revealed that S-SCAM can interact with neuroligin 2, which is known to be exclusively localized at inhibitory synapses. The WW domains and the second PDZ domain of S-SCAM are involved in the interaction with neuroligin 2. β-DG, neuroligin 2 and S-SCAM form a tripartite complex in vitro. Neuroligin 2 is detected in the immunoprecipitates by anti-β-DG antibody from rat brain. S-SCAM, β-DG and neuroligin 2 are partially co-localized in rat hippocampal neurons. These data suggest that S-SCAM is associated with β-DG and neuroligin 2 at inhibitory synapses, and functions as a linker between the dystrophin glycoprotein complex and the neurexin–neuroligin complex.