Hideyuki Saya

A Novel NE-dlg/SAP102-associated Protein, p51-nedasin, Related to the Amidohydrolase Superfamily, Interferes with the Association between NE-dlg/SAP102 and N-Methyl-d-aspartate Receptor

The membrane-associated guanylate kinase proteins have been known to interact various membrane receptors with their N-terminal segments designated the PDZ domains and to cluster these receptors at the target site of the cell membrane. NE-dlg/SAP102, a neuronal and endocrine tissue-specific MAGUK family protein, was found to be expressed in both dendrites and cell bodies in neuronal cells. Although NE-dlg/SAP102 localized at dendrites was shown to interact with N-methyl-d-aspartate receptor 2B via the PDZ domains to compose postsynaptic density, the binding proteins existing in the cell body of the neuron are still unknown. Here we report the isolation of a novel NE-dlg/SAP102-associated protein, p51-nedasin. Nedasin has a significant homology with amidohydrolase superfamily proteins and shows identical sequences to a recently identified protein that has guanine aminohydrolase activity. Nedasin has four alternative splice variants (S, V1, V2, and V3) that exhibited different C-terminal structures. NE-dlg/SAP102 is shown to interact with only the S form of nedasin which is predominantly expressed in brain. The expression of nedasin in neuronal cells increases in parallel with the progress of synaptogenesis and is mainly detected in cell bodies where it co-localizes with NE-dlg/SAP102. Furthermore, nedasin interferes with the association between NE-dlg/SAP102 and NMDA receptor 2B in vitro. These findings suggest that alternative splicing of nedasin may play a role in the formation and/or structural change in synapses during neuronal development by modifying clustering of neurotransmitter receptors at the synaptic sites.

Study of autoantibodies against advanced glycation endproducts of the Maillard reaction

Abstract Long-term incubation of proteins with reducing sugar proceeds to advanced glycation end products (AGEs). We previously demonstrated the presence of AGE structures in human and animal tissues, and suggested the implication of AGEs in aging and diabetic complications. In this study, we tested whether AGEs present in vivo, such as N e -(carboxymethyl) lysine (CML) adduct, could serve as immunogens for generating autoantibodies. Plasma samples from STZ-induced diabetic rats reacted positively with AGE-proteins as well as CML-BSA, suggesting the presence of autoantibodies against AGE-structures, particularly CML in diabetic rats; the activity of the autoantibody increased with the duration of diabetic states, reflecting the accumulation of AGE proteins in these diabetic rats. An autoantibody fraction purified from the plasma of diabetic patients showed a positive reaction to AGE-proteins as well as to CML proteins, and also to human lens proteins which are known to undergo CML modification in vivo. Patients with renal failure caused by diabetes or nondiabetic pathologies had a higher autoantibody activity against AGE structures than that in normal subjects or diabetic patients without renal failure. These results suggest that AGEs accumulated in vivo serve as immunological epitopes for developing autoantibodies against AGEs, particularly against a CML structure, which might be used as an indicator of diabetic nephropathy or chronic renal failure.