Exocyst complex subunit sec8 binds to postsynaptic density protein-95 (PSD-95): a novel interaction regulated by cypin (cytosolic PSD-95 interactor)

• Published in: Biochemical journal Vol. 373; no. Pt 1; pp. 49 - 55
• Main Authors: Riefler, Gary M, Balasingam, Gaithri, Lucas, Kenyatta G, Wang, Sheng, Hsu, Shu-Chan, Firestein, Bonnie L
• Format: Journal Article
• Language: English
• Published: England 01.07.2003
• Subjects: Amino Acid Sequence; Animals; Base Sequence; Binding Sites; Brain - metabolism; Carrier Proteins - chemistry; Carrier Proteins - isolation & purification; Carrier Proteins - metabolism; Cloning, Molecular; Disks Large Homolog 4 Protein; DNA Primers; Escherichia coli - genetics; Guanine Deaminase; Intracellular Signaling Peptides and Proteins; Membrane Proteins; Molecular Sequence Data; Nerve Tissue Proteins - chemistry; Nerve Tissue Proteins - isolation & purification; Nerve Tissue Proteins - metabolism; Neurites - physiology; PC12 Cells; Polymerase Chain Reaction; Protein Subunits - metabolism; Rats; Recombinant Fusion Proteins - chemistry; Recombinant Fusion Proteins - isolation & purification; Recombinant Fusion Proteins - metabolism; Vesicular Transport Proteins
• DOI: 10.1042/bj20021838
• ISSN: 0264-6021

The PDZ domains of postsynaptic density (PSD) protein-95 play a role in the localization of PSD-95 and binding partners to neuronal synapses. The identification of binding partners to these PDZ domains can help us in understanding how signalling complexes are assembled. We observed that one of the subunits in the sec6/8 or exocyst complex, sec8, contains a C-terminal consensus sequence for PDZ binding. Sec8 binds to PDZ1-2 of PSD-95, and this binding can be competed with a peptide that binds to PDZ1 and PDZ2 in the peptide-binding site. In addition, binding of sec8 is dependent on its C-terminal-binding sequence namely Thr-Thr-Val (TTV). Immunoblotting of rat tissue extracts shows that sec8 and PSD-95 are enriched in the same brain regions, and sec8 and PSD-95 have the same subcellular distribution in pheochromocytoma cells, suggesting that these proteins may interact in vivo. Immunoprecipitation studies of sec8 and PSD-95 in brain provide further evidence of a sec8 and PSD-95 interaction. Furthermore, the cytosolic PSD-95 interactor competes with sec8 for interaction with PSD-95. Taken together, our results suggest that the cytosolic PSD-95 interactor may function to regulate the ability of sec8 to bind to PSD-95.