Analysis of a membrane-enriched proteome from postmortem human brain tissue in Alzheimer's disease

Article (PDF Available)inPROTEOMICS - CLINICAL APPLICATIONS 6(3-4):201-11 · April 2012with56 Reads
DOI: 10.1002/prca.201100068 · Source: PubMed
Abstract
The present study is a discovery mode proteomics analysis of the membrane-enriched fraction of postmortem brain tissue from Alzheimer's disease (AD) and control cases. This study aims to validate a method to identify new proteins that could be involved in the pathogenesis of AD and potentially serve as disease biomarkers. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to analyze the membrane-enriched fraction of human postmortem brain tissue from five AD and five control cases of similar age. Biochemical validation of specific targets was performed by immunoblotting. One thousand seven hundred and nine proteins were identified from the membrane-enriched fraction of frontal cortex. Label-free quantification by spectral counting and G-test analysis identified 13 proteins that were significantly changed in disease. In addition to Tau (MAPT), two additional proteins found to be enriched in AD, ubiquitin carboxy-terminal hydrolase 1 (UCHL1), and syntaxin-binding protein 1 (Munc-18), were validated through immunoblotting. DISCUSSION AND CLINICAL RELEVANCE: Proteomic analysis of the membrane-enriched fraction of postmortem brain tissue identifies proteins biochemically altered in AD. Further analysis of this subproteome may help elucidate mechanisms behind AD pathogenesis and provide new sources of biomarkers.

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    • "In a previous study, CKBB and respiratory chain complexes activities were both observed to be altered by monoamine-based antidepressants in rat brain (R?us et al., 2012 ). Moreover, overexpression of CKBB has been demonstrated to be associated with AD (Donovan et al., 2012). Our proteomic data and the results of previous studies suggest that BT may disturb energy homeostasis in the CNS of fish, potentially leading to neurodegeneration; however this hypothesis must be tested in additional experiments. "
    [Show abstract] [Hide abstract] ABSTRACT: Benzotriazole (BT) is a high-production volume chemical which has been ubiquitously detected in aquatic environments. Although adverse effects from acute and chronic exposure to BT have been reported, the neurotoxic effect of BT and the mechanisms of toxicity are not well documented. In this study, adult female Chinese rare minnow (Gobiocypris rarus) were exposed to 0.05, 0.5, and 5 mg/L BT for 28 days. The brain proteome showed that BT exposure mainly involved in metabolic process, signal transduction, stress response, cytoskeleton, and transport. Pathway analysis revealed that cellular processes affected by BT included cellular respiration, G-protein signal cascades, Ca²⁺-dependent signaling, cell cycle and apoptosis. Moreover, data on relative mRNA levels demonstrated that genes related to these toxic pathways were also significantly affected by BT. Furthermore, proteins affected by BT such as CKBB, GS, HPCA, VDAC1, and FLOT1A are associated with neurological disorders. Therefore, our finding suggested that BT induced molecular responses in the brain and could provide new insight into BT neurotoxicity in Chinese rare minnow.
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    • "The mechanism by which these mutations lead to the pathological epileptic phenotype is poorly understood and may involve either haploinsufficiency of the wild-type (WT) protein or a gain of pathological function of the mutant allele. In addition, dysregulation of Munc18-1 expression has been associated with other neurological disorders, including Alzheimer's disease (Jacobs et al., 2006; Donovan et al., 2012 ) and Rasmussen encephalitis (Alvarez-Barón et al., 2008). In this study, we reveal a critical new role for Munc18-1 in chaperoning α-synuclein (α- Syn), thereby controlling its aggregative propensity and ability to form toxic α-Syn oligomers. "
    [Show abstract] [Hide abstract] ABSTRACT: Munc18-1 is a key component of the exocytic machinery that controls neurotransmitter release. Munc18-1 heterozygous mutations cause developmental defects and epileptic phenotypes, including infantile epileptic encephalopathy (EIEE), suggestive of a gain of pathological function. Here, we used single-molecule analysis, gene-edited cells, and neurons to demonstrate that Munc18-1 EIEE-causing mutants form large polymers that coaggregate wild-type Munc18-1 in vitro and in cells. Surprisingly, Munc18-1 EIEE mutants also form Lewy body-like structures that contain α-synuclein (α-Syn). We reveal that Munc18-1 binds α-Syn, and its EIEE mutants coaggregate α-Syn. Likewise, removal of endogenous Munc18-1 increases the aggregative propensity of α-Syn(WT) and that of the Parkinson's disease-causing α-Syn(A30P) mutant, an effect rescued by Munc18-1(WT) expression, indicative of chaperone activity. Coexpression of the α-Syn(A30P) mutant with Munc18-1 reduced the number of α-Syn(A30P) aggregates. Munc18-1 mutations and haploinsufficiency may therefore trigger a pathogenic gain of function through both the corruption of native Munc18-1 and a perturbed chaperone activity for α-Syn leading to aggregation-induced neurodegeneration.
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    • "As an alternative, gel-free shotgun MS in conjunction with quantitative proteomic technique, e.g. stable isotope labeling [15, 16] or label-free methods17181920, have recently been used for identification and quantification of proteins involved in the pathogenesis of AD. Furthermore, combining gel-free shotgun MS approaches with protein depletion of high abundant proteins enables detection and quantification of low abundant proteins [21]. "
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