Identification of glycosylated proteins in Alzheimer's disease brain.
Item
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Title
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Identification of glycosylated proteins in Alzheimer's disease brain.
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Identifier
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AAI3115259
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identifier
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3115259
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Creator
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Huang, Yu.
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Contributor
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Advisers: Cheng-Xin Gong | Khalid Iqbal
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Date
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2004
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Neuroscience
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Abstract
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Alzheimer's disease (AD) is a common neurodegenerative disorder with unknown molecular pathogenesis. We recently found that in AD brain, tau is also aberrantly glycosylated besides being abnormally hyperphosphorylated, suggesting that the protein glycosylation system might be affected in AD brain. Here, we developed methodologies for isolation of glycoproteins from human brain homogenates. It included membrane protein extraction, ion-exchange chromatography, and lectin affinity chromatographies. By combining these methodologies with mass spectrometry analysis, we identified 12 predominant glycoproteins from AD brain. Nine of these identified proteins are previously characterized proteins and have been reported to be glycosylated. The rest three proteins are unknown proteins that have not yet been purified or characterized, but their primary structures can be deduced from human genome database. Comparison of lectin-stainings of glycoproteins between AD and control brains revealed that two proteins (43 kDa and 35 kDa, respectively) were increased and another 180 kDa protein was decreased in AD brain. One of these proteins, the 43 kDa protein, was identified as human acid ceramidase (AC). Western blot analysis suggested that the increased lectin staining was due to an elevated level of AC rather than elevated glycosylation. Immunohistochemical studies revealed that AC was expressed mainly in neurons and some astrocytes. It also co-localized with neurofibrillary tangles. In addition, we discovered that two inflammation-activated proteins, inhibitor gamma of nuclear factor kappaB (IkappaBgamma) and glial fibrillary acidic protein (GFAP), were up regulated in AD.;Identification of major brain glycoproteins suggests these glycoproteins might play important roles in central nervous system and provide new information to understand the biophysiological functions of brain glycoproteins. Our finding that several glycoproteins are altered in AD brain supports our hypothesis that the glycosylation system might be affected in AD. The accumulation of AC in AD brain and its co-localization with neurofibrillary tangles implied that AC might be involved in pathophysiology of AD. Our discovery that both IkappaBgamma and GFAP are up regulated provides a possible molecular mechanism of inflammation activation of AD brain. Taken together, these studies provide new avenues to understanding the molecular mechanisms of AD.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
