MAGUIN, a novel neuronal membrane-associated guanylate kinase-interacting protein

Postsynaptic density (PSD)-95/Synapse-associated protein (SAP) 90 and synap tic scaffolding molecule (S-SCAM) are neuronal membrane-associated guanylat e kinases. Because PSD-95/SAP90 and S-SCAM function as synaptic scaffolding proteins, identification of ligands for these proteins is important to elu cidate the structure of synaptic junctions. Here, we report a novel protein interacting with the PDZ domains of PSD-95/SAP90 and S-SCAM and named it M AGUIN-1 (membrane-associated guanylate kinase-interacting protein-1). MAGUI N-1 has one sterile alpha motif, one PDZ, and one plekstrin homology domain . MAGUIN-1 is localized at the plasma membrane via the plekstrin homology d omain and the C-terminal region and interacts with PSD-95/SAP90 and S-SCAM via a C-terminal PDZ domain-binding moth, MAGUIN-1 has a short isoform, MAG UIN-2, which lacks a PDZ domain-binding motif, MAGUINs are expressed in neu rons and localized in the cell body and neurites and are coimmunoprecipitat ed with PSD-95/SAP90 and S-SCAM hom rat crude synaptosome. MAGUIN-1 may pla y an important role with PSD-95/SAP90 and S-SCAM to assemble the components of synaptic junctions.