| Co-Investigator(Kenkyū-buntansha) |
AKIGUCHI Ichiro Ryukoku University, Department of Health Control, Director, 健康管理センター, 所長 (30115779)
NODA Makoto Kyoto University, Department of Molecular Oncology, Professor, 医学研究科, 教授 (30146708)
KITAYAMA Hitoshi Kyoto University, Department of Molecular Oncology, Assistant Professor, 医学研究科, 助教授 (30231286)
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| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2004: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2003: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2002: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
Septins are a family of GTPases that form filamentous complex and may provide scaffold or diffusion barrier for other proteins. Although their physiological function in the brain is largely unknown, some septins are associated with neurofibrillary tangles in Alzheimer's disease. In this study, we made immunohistochemical screening to test their possible involvement in synucleinopathy. An antibody directed against a sep4/H5 consistently labeled 50-80% of α-synuclein-positive cytoplasmic deposits in postmortem human brain samples ; Lewy bodies(LBs) in Parkinson's disease and dementia with Lewy bodies, and glial cytoplasmic inclusions(GCIs) in multiple system atrophy. By contrast, five other septins, Nedd5,CDC10,CDCrel-1,Septin6, and Septin7, were not detected in the deposits of the same samples. In a human neuroglioma cell line, transiently expressed Sep4/H5 and α-synuclein partially co-localized in a reticular pattern in the cytoplasm. The two proteins co-immunoprecipitated in the deter
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gent-soluble and -insoluble fractions of mouse neuroblastoma cell lines, and in the soluble fraction of mouse fibroblast cell lines. FLAG-tagged Sept4/H5 and Myc-tagged α-synuclein formed detergent-insoluble complex, and upon treatment with a proteasome inhibitor, they formed Lewy body-like cytoplasmic inclusions. The tagged Sept4/H5 and α-synuclein synergistically accelerated cell death induced by the proteasome inhibitor, and this effect was further enhanced by expression of another Lewy body-associated protein, synphilin-1, tagged with the V5 epitope. Moreover, co-expression of the three proteins (tagged Sept4/H5, α-synuclein, and synphilin-1) was sufficient to induce cell death. These data raise the possibility that Sept4/H5 is involved in the formation of cytoplasmic inclusions as well as induction of cell death in the α-synuclein-associated neurodegenerative disorders. The cooperative insolubilization of Sep4/H5 and α-synuclein may be a biochemical basis for their aggregation as LB/GCI. Less
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