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 b-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 b-dystroglycan (b-DG) as a binding partner for S-SCAM at inhibitory synapses. WW domains of S-SCAM bind to three sequences of b-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. b-DG, neuroligin 2 and S-SCAM form a tripartite complex in vitro. Neuroligin 2 is detected in the immunoprecipitates by anti-b-DG antibody from rat brain. S-SCAM, b-DG and neuroligin 2 are partially co-localized in rat hippocampal neurons. These data suggest that S-SCAM is associated with b-DG and neuroligin 2 at inhibitory synapses, and functions as a linker between the dystrophin glycoprotein complex and the neurexin-neuroligin complex. Keywords: dystroglycan, inhibitory synapse, neuroligin. Abbreviations used: ADH1, alcohol dehydrogenase 1; BHK, baby hamster kidney; BSA, bovine serum albumin; b-DG, b-dystroglycan; DEAE, diethylaminoethyl; Div, day in vitro; GFP, green fluorescent protein; GK, guanylate kinase; GST, glutathione-S-transferase; MAGI, membrane-associated guanylate kinase with inverted organization; MBP, maltose-binding protein; MDCK, Madine-Darby canine kidney; NL2, neuroligin 2; NR1, NMDA receptor subunit 1; PBS, phosphate-buffered saline; PDZ, PSD-95/Discs large/ZO-1; PSD-95, postsynaptic density-95; SAPAP1, Synapse-associated protein 90/PSD-95-associated protein 1; SH3, src homology 3; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; S-SCAM, synaptic scaffolding molecule; VGAT, vesicular GABA transporter; YFP, yellow fluorescent protein; ZO-1, zonula occludens-1.