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Numaguchi Y, Tsukakoshi K, Takeuchi N, Suzuki Y, Ikebukuro K, Kawano R. Real-time monitoring of the amyloid β 1-42 monomer-to-oligomer channel transition using a lipid bilayer system. PNAS NEXUS 2024; 3:pgad437. [PMID: 38156289 PMCID: PMC10753159 DOI: 10.1093/pnasnexus/pgad437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Accepted: 12/06/2023] [Indexed: 12/30/2023]
Abstract
This study describes the observation of the transformation of monomeric amyloid β1-42 (Aβ42) into oligomers in a lipid membrane utilizing a lipid bilayer system for electrophysiological measurement. The relevance of oligomers and protofibrils in Alzheimer's disease (AD) is underscored given their significant neurotoxicity. By closely monitoring the shift of Aβ42 from its monomeric state to forming oligomeric channels in phospholipid membranes, we noted that this transformation transpired within a 2-h frame. We manipulated the lipid membrane's constitution with components such as glycerophospholipid, porcine brain total lipid extract, sphingomyelin (SM), and cholesterol (Chol.) to effectively imitate nerve cell membranes. Interesting findings showcased Chol.'s ability to foster stable oligomeric channel formation in the lipid membrane, with SM and GM1 lipids potentially enhancing channel formation as well. Additionally, the study identified the potential of a catechin derivative, epigallocatechin gallate (EGCG), in obstructing oligomerization. With EGCG present in the outer solution of the Aβ42-infused membrane, a noteworthy reduction in channel current was observed, suggesting the successful inhibition of oligomerization. This conclusion held true in both, prior and subsequent, stages of oligomerization. Our findings shed light on the toxicity of oligomers, promising invaluable information for future advancements in AD treatment strategies.
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Affiliation(s)
- Yuri Numaguchi
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Tokyo 184-0011, Japan
| | - Kaori Tsukakoshi
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Tokyo 184-0011, Japan
| | - Nanami Takeuchi
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Tokyo 184-0011, Japan
| | - Yuki Suzuki
- Department of Chemistry for Materials, Graduate School of Engineering, Mie University, Mie 514-0102, Japan
| | - Kazunori Ikebukuro
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Tokyo 184-0011, Japan
| | - Ryuji Kawano
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Tokyo 184-0011, Japan
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2
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Cacciottolo M, Morgan TE, Saffari AA, Shirmohammadi F, Forman HJ, Sioutas C, Finch CE. Traffic-related air pollutants (TRAP-PM) promote neuronal amyloidogenesis through oxidative damage to lipid rafts. Free Radic Biol Med 2020; 147:242-251. [PMID: 31883973 PMCID: PMC7075030 DOI: 10.1016/j.freeradbiomed.2019.12.023] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 12/10/2019] [Accepted: 12/20/2019] [Indexed: 12/21/2022]
Abstract
Traffic-related air pollution particulate matter (TRAP-PM) is associated with increased risk of Alzheimer Disease (AD). Rodent models respond to nano-sized TRAP-PM (nPM) with increased production of amyloid Aβ peptides, concurrently with oxidative damage. Because pro-Aβ processing of the amyloid precursor protein (APP) occurs on subcellular lipid rafts, we hypothesized that oxidative stress from nPM exposure would alter lipid rafts to favor Aβ production. This hypothesis was tested with J20 mice and N2a cells transgenic for hAPPswe (familial AD). Exposure of J20-APPswe mice to nPM for 150 h caused increased lipid oxidation (4-HNE) and increased the pro-amyloidogenic processing of APP in lipid raft fractions in cerebral cortex; the absence of these changes in cerebellum parallels the AD brain region selectivity for Aβ deposits. In vitro, nPM induced similar oxidative responses in N2a-APPswe cells, with dose-dependent production of NO, oxidative damage (4-HNE, 3NT), and lipid raft alterations of APP with increased Aβ peptides. The antioxidant N-acetyl-cysteine (NAC) attenuated nPM-induced oxidative damage and lipid raft alterations of APP processing. These findings identify neuronal lipid rafts as novel targets of oxidative damage in the pro-amyloidogenic effects of air pollution.
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Affiliation(s)
- Mafalda Cacciottolo
- Leonard Davis School of Gerontology, University of Southern California, Los Angeles, CA, USA
| | - Todd E Morgan
- Leonard Davis School of Gerontology, University of Southern California, Los Angeles, CA, USA
| | - Arian A Saffari
- Viterbi School of Engineering, University of Southern California, Los Angeles, CA, USA
| | - Farimah Shirmohammadi
- Viterbi School of Engineering, University of Southern California, Los Angeles, CA, USA
| | - Henry Jay Forman
- Leonard Davis School of Gerontology, University of Southern California, Los Angeles, CA, USA
| | - Costantinos Sioutas
- Viterbi School of Engineering, University of Southern California, Los Angeles, CA, USA
| | - Caleb E Finch
- Leonard Davis School of Gerontology, University of Southern California, Los Angeles, CA, USA; Dornsife College, Dept. Biological Sciences, University of Southern California, Los Angeles, CA, USA.
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3
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Kumar A, Sivanandam TM, Thakur MK. Presenilin 2 overexpression is associated with apoptosis in Neuro2a cells. Transl Neurosci 2016; 7:71-75. [PMID: 28123824 PMCID: PMC5234515 DOI: 10.1515/tnsci-2016-0011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 06/09/2016] [Indexed: 01/21/2023] Open
Abstract
Presenilin 1 (PS1) and PS2 are evolutionarily conserved transmembrane proteins of the aspartyl protease family. Initially, they were reported to be associated with the early onset of familial, early-onset Alzheimer’s disease. PS1 has been implicated in several crucial brain functions including developmental processes, synaptic plasticity, and processing of various molecules, while PS2 has been poorly studied and is considered to be a compensatory partner of PS1. Certain controversial reports have suggested that PS2 has a role in apoptosis, though the underlying mechanism is not clear. To ascertain the role of PS2 in apoptosis, mouse neuroblastoma cells (Neuro2a) were transfected with a cDNA construct encoding full length mouse PS2 and analyzed for viability, expression of PS1, PS2, Bax and p53, Bax protein, and status of chromatin condensation. Our results showed reduced viability, condensed chromatin and higher expression of Bax at mRNA and protein levels, but no change in the expression of p53 and PS1 in PS2-overexpressing Neuro2a cells. Thus, it is evident that PS2, independent of PS1, is associated with apoptosis via a Bax-mediated pathway. These findings might help in the understanding of the involvement of PS2 in apoptosis and its associated brain disorders.
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Affiliation(s)
- Ashish Kumar
- Laboratory of Biochemistry and Molecular Biology, Brain Research Centre, Department of Zoology, Banaras Hindu University, Varanasi 221 005, India; Centre for Genomics, Jiwaji University, Gwalior 474 011, India
| | - T M Sivanandam
- Laboratory of Biochemistry and Molecular Biology, Brain Research Centre, Department of Zoology, Banaras Hindu University, Varanasi 221 005, India
| | - M K Thakur
- Laboratory of Biochemistry and Molecular Biology, Brain Research Centre, Department of Zoology, Banaras Hindu University, Varanasi 221 005, India
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4
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Gudey SK, Wallenius A, Landström M. Regulated intramembrane proteolysis of the TGFβ type I receptor conveys oncogenic signals. Future Oncol 2014; 10:1853-61. [PMID: 24597658 DOI: 10.2217/fon.14.45] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Cancer cells produce high levels of TGFβ, a multipotent cytokine. Binding of TGFβ to its cell surface receptors, the transmembrane serine/threonine kinases TβRII and TβRI, causes phosphorylation and activation of intracellular latent Smad transcription factors. Nuclear Smads act in concert with specific transcription factors to reprogram epithelial cells to become invasive mesenchymal cells. TGFβ also propagates non-canonical signals, so it is crucial to have a better understanding of the underlying molecular mechanisms which favor this pathway. Here we highlight our recent discovery that TGFβ promotes the proteolytic cleavage of TβRI in cancer cells, resulting in the liberation and nuclear translocation of its intracellular domain, acting as co-regulator to transcribe pro-invasive genes. This newly identified oncogenic TGFβ pathway resembles the Notch signaling pathway. We discuss our findings in relation to Notch and provide a short overview of other growth factors that transduce signals via nuclear translocation of their cell surface receptors.
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Affiliation(s)
- Shyam Kumar Gudey
- Department of Medical Biosciences, Pathology, Umeå University, SE-901 85 Umeå, Sweden
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5
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Santos LO, Garcia-Gomes AS, Catanho M, Sodre CL, Santos ALS, Branquinha MH, d'Avila-Levy CM. Aspartic peptidases of human pathogenic trypanosomatids: perspectives and trends for chemotherapy. Curr Med Chem 2014; 20:3116-33. [PMID: 23298141 PMCID: PMC3837538 DOI: 10.2174/0929867311320250007] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Accepted: 12/27/2012] [Indexed: 12/13/2022]
Abstract
Aspartic peptidases are proteolytic enzymes present in many organisms like vertebrates, plants, fungi, protozoa and in some retroviruses such as human immunodeficiency virus (HIV). These enzymes are involved in important metabolic processes in microorganisms/virus and play major roles in infectious diseases. Although few studies have been performed in order to identify and characterize aspartic peptidase in trypanosomatids, which include the etiologic agents of leishmaniasis, Chagas’ disease and sleeping sickness, some beneficial properties of aspartic peptidase inhibitors have been described on fundamental biological events of these pathogenic agents. In this context, aspartic peptidase inhibitors (PIs) used in the current chemotherapy against HIV (e.g., amprenavir, indinavir, lopinavir, nelfinavir, ritonavir and saquinavir) were able to inhibit the aspartic peptidase activity produced by different species of Leishmania. Moreover, the treatment of Leishmania promastigotes with HIV PIs induced several perturbations on the parasite homeostasis, including loss of the motility and arrest of proliferation/growth. The HIV PIs also induced an increase in the level of reactive oxygen species and the appearance of irreversible morphological alterations, triggering parasite death pathways such as programed cell death (apoptosis) and uncontrolled autophagy. The blockage of physiological parasite events as well as the induction of death pathways culminated in its incapacity to adhere, survive and escape of phagocytic cells. Collectively, these results support the data showing that parasites treated with HIV PIs have a significant reduction in the ability to cause in vivo infection. Similarly, the treatment of Trypanosoma cruzi cells with pepstatin A showed a significant inhibition on both aspartic peptidase activity and growth as well as promoted several and irreversible morphological changes. These studies indicate that aspartic peptidases can be promising targets in trypanosomatid cells and aspartic proteolytic inhibitors can be benefic chemotherapeutic agents against these human pathogenic microorganisms.
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Affiliation(s)
- L O Santos
- Laboratório de Biologia Molecular e Doenças Endêmicas, Instituto Oswaldo Cruz-IOC, Fundação Oswaldo Cruz-FIOCRUZ, Rio de Janeiro, Brazil
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6
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Schedin-Weiss S, Inoue M, Teranishi Y, Yamamoto NG, Karlström H, Winblad B, Tjernberg LO. Visualizing active enzyme complexes using a photoreactive inhibitor for proximity ligation--application on γ-secretase. PLoS One 2013; 8:e63962. [PMID: 23717518 PMCID: PMC3663845 DOI: 10.1371/journal.pone.0063962] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 04/09/2013] [Indexed: 11/20/2022] Open
Abstract
Here, we present a highly sensitive method to study protein-protein interactions and subcellular location selectively for active multicomponent enzymes. We apply the method on γ-secretase, the enzyme complex that catalyzes the cleavage of the amyloid precursor protein (APP) to generate amyloid β-peptide (Aβ), the major causative agent in Alzheimer disease (AD). The novel assay is based on proximity ligation, which can be used to study protein interactions in situ with very high sensitivity. In traditional proximity ligation assay (PLA), primary antibody recognition is typically accompanied by oligonucleotide-conjugated secondary antibodies as detection probes. Here, we first performed PLA experiments using antibodies against the γ-secretase components presenilin 1 (PS1), containing the catalytic site residues, and nicastrin, suggested to be involved in substrate recognition. To selectively study the interactions of active γ-secretase, we replaced one of the primary antibodies with a photoreactive γ-secretase inhibitor containing a PEG linker and a biotin group (GTB), and used oligonucleotide-conjugated streptavidin as a probe. Interestingly, significantly fewer interactions were detected with the latter, novel, assay, which is a reasonable finding considering that a substantial portion of PS1 is inactive. In addition, the PLA signals were located more peripherally when GTB was used instead of a PS1 antibody, suggesting that γ-secretase matures distal from the perinuclear ER region. This novel technique thus enables highly sensitive protein interaction studies, determines the subcellular location of the interactions, and differentiates between active and inactive γ-secretase in intact cells. We suggest that similar PLA assays using enzyme inhibitors could be useful also for other enzyme interaction studies.
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Affiliation(s)
- Sophia Schedin-Weiss
- KI-Alzheimer Disease Research Center-KI-ADRC, Karolinska Institutet, Department of Neurobiology, Care Sciences and Society-NVS, Novum Level 5, Stockholm, Sweden.
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7
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Abstract
The Notch signaling pathway is activated in the majority of T cell acute lymphoblastic leukemias (T-ALL). Adding to the complexity of Notch signaling in hematopoiesis, recently in Nature, Klinakis et al. (2011) demonstrate a tumor-suppressor function for the Notch pathway in myeloid malignancy.
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8
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Nacher JC, Schwartz JM. Modularity in protein complex and drug interactions reveals new polypharmacological properties. PLoS One 2012; 7:e30028. [PMID: 22279562 PMCID: PMC3261189 DOI: 10.1371/journal.pone.0030028] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Accepted: 12/12/2011] [Indexed: 11/18/2022] Open
Abstract
Recent studies have highlighted the importance of interconnectivity in a large range of molecular and human disease-related systems. Network medicine has emerged as a new paradigm to deal with complex diseases. Connections between protein complexes and key diseases have been suggested for decades. However, it was not until recently that protein complexes were identified and classified in sufficient amounts to carry out a large-scale analysis of the human protein complex system. We here present the first systematic and comprehensive set of relationships between protein complexes and associated drugs and analyzed their topological features. The network structure is characterized by a high modularity, both in the bipartite graph and in its projections, indicating that its topology is highly distinct from a random network and that it contains a rich and heterogeneous internal modular structure. To unravel the relationships between modules of protein complexes, drugs and diseases, we investigated in depth the origins of this modular structure in examples of particular diseases. This analysis unveils new associations between diseases and protein complexes and highlights the potential role of polypharmacological drugs, which target multiple cellular functions to combat complex diseases driven by gain-of-function mutations.
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Affiliation(s)
- Jose C Nacher
- Department of Complex and Intelligent Systems, Future University Hakodate, Hokkaido, Japan.
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9
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Pyridazine-derived γ-secretase modulators. Bioorg Med Chem Lett 2011; 21:4016-9. [DOI: 10.1016/j.bmcl.2011.04.143] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Revised: 04/08/2011] [Accepted: 04/29/2011] [Indexed: 11/23/2022]
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10
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Wan Z, Hall A, Sang Y, Xiang JN, Yang E, Smith B, Harrison DC, Yang G, Yu H, Price HS, Wang J, Hawkins J, Lau LF, Johnson MR, Li T, Zhao W, Mitchell WL, Su X, Zhang X, Zhou Y, Jin Y, Tong Z, Cheng Z, Hussain I, Elliott JD, Matsuoka Y. Pyridine-derived γ-secretase modulators. Bioorg Med Chem Lett 2011; 21:4832-5. [PMID: 21742495 DOI: 10.1016/j.bmcl.2011.06.042] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2011] [Revised: 06/07/2011] [Accepted: 06/10/2011] [Indexed: 11/30/2022]
Abstract
SAR of a novel series of pyridine-derived γ-secretase modulators is described. Compound 5 was found to be a potent modulator in vitro, which on further profiling, was found to decrease Aβ42 and Aβ40, and maintain (or increase) the levels of total Aβ. Furthermore, representative compounds 1 and 5 demonstrated in vivo efficacy to lower Aβ42 in the brain without altering Notch processing in the peripheral.
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Affiliation(s)
- Zehong Wan
- Research and Development, GlaxoSmithKline Pharmaceuticals, 898 Halei Road, Zhangjiang Hi-tech Park, Pudong, Shanghai 201023, China.
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11
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Oda A, Tamaoka A, Araki W. Oxidative stress up-regulates presenilin 1 in lipid rafts in neuronal cells. J Neurosci Res 2010; 88:1137-45. [PMID: 19885829 DOI: 10.1002/jnr.22271] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Oxidative stress is associated with beta-amyloid peptide (A beta) accumulation in the brains of Alzheimer's disease patients. A beta is generated upon the sequential proteolytic cleavage of transmembrane amyloid precursor protein (APP) by two membrane-bound proteases, beta-secretase (BACE1) and the gamma-secretase complex comprising presenilin 1 (PS1), nicastrin, APH-1 and PEN-2. Recent evidence suggests that significant amounts of BACE1 and gamma-secretase components localize in the cholesterol-rich region of membranes known as lipid rafts, where A beta production occurs preferentially. In this study, we investigated the effects of oxidative stress on the BACE1 and gamma-secretase components in lipid rafts using human neuroblastoma SH-SY5Y cells exposed to ethacrynic acid (EA), a compound that induces cellular glutathione depletion. Following exposure of cells to EA, heme oxygenase-1, a marker protein of oxidative stress, was strongly induced. Moreover, treatment with EA resulted in a significant increase in PS1 protein levels, but not those of nicastrin, APH-1, PEN-2 or BACE1, in both cell lysates and the lipid raft fraction. This increase in PS1 protein expression was prevented by co-treatment with an antioxidant, N-acetylcysteine (NAC). EA additionally induced a significant increase in PS1 mRNA expression, which was inhibited by NAC. Finally, EA treatment was found to promote A beta secretion from cells expressing Swedish mutant APP. It appears that in our cell culture model, oxidative stress enhances PS1 protein levels in lipid rafts via up-regulation of PS1 transcription, which may constitute the mechanism underlying the oxidative stress-associated promotion of A beta production.
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Affiliation(s)
- Akiko Oda
- Department of Demyelinating Disease and Aging, National Institute of Neuroscience, NCNP, Tokyo, Japan
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12
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Piperidine-derived γ-secretase modulators. Bioorg Med Chem Lett 2010; 20:1306-11. [DOI: 10.1016/j.bmcl.2009.08.072] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2009] [Revised: 08/19/2009] [Accepted: 08/20/2009] [Indexed: 11/23/2022]
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13
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Lin HB, Yang XM, Li TJ, Cheng YF, Zhang HT, Xu JP. Memory deficits and neurochemical changes induced by C-reactive protein in rats: implication in Alzheimer's disease. Psychopharmacology (Berl) 2009; 204:705-14. [PMID: 19263040 DOI: 10.1007/s00213-009-1499-2] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Accepted: 02/19/2009] [Indexed: 11/24/2022]
Abstract
RATIONALE C-reactive protein (CRP), an acute phase protein that is released in response to inflammatory stimuli, is implicated in Alzheimer's disease (AD). However, the role of CRP in memory deficits associated with AD remains unclear. OBJECTIVE Experiments were carried out to determine whether CRP impaired memory and altered neurochemical measures associated with AD. METHODS The effects of intra-cerebroventricular administration of CRP or beta-amyloid peptide 25-35 (Abeta(25-35)) on memory performance were evaluated using rat Morris water-maze and step-through passive avoidance tests; the levels of inflammatory cytokines (interleukin-1beta (IL-1beta), IL-6, and tumor necrosis factor (TNF-alpha)), endogenous CRP, and markers of the endogenous production of Abeta, including amyloid precursor protein (APP), presenilins (PS-1 and PS-2), and beta-site of APP cleaving enzyme (BACE), were also determined in brain regions using real-time reverse transcriptase polymerase chain reaction (RT-PCR) and Western blotting analysis. RESULTS Treatment with CRP (25.6 microg/rat) or Abeta(25-35) (10 microg/rat) 2 weeks ahead produced impairment of long-term memory in both animal tests. Real-time RT-PCR revealed increases in messenger RNA levels of APP, IL-1beta, IL-6, TNF-alpha, and CRP in the cerebral cortex and hippocampus and those of PS-1 and PS-2 in the cerebral cortex produced by treatment with CRP or Abeta(25-35). Immunoblotting analysis showed that while expression of APP was increased in both the cerebral cortex and the hippocampus, expression of IL-1beta, BACE, and TNF-alpha was increased only in the hippocampus. CONCLUSIONS The results suggest that CRP contributes to memory loss and early phase of pathogenesis of AD. CRP can be a novel target for therapeutic intervention of AD.
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Affiliation(s)
- Huan-Bing Lin
- Department of Pharmacology, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, 510515, People's Republic of China
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Abstract
The structure-function relationships of aspartic peptidases (APs) (EC 3.4.23.X) have been extensively investigated, yet much remains to be elucidated regarding the various molecular mechanisms of these enzymes. Over the past years, APs have received considerable interest for food applications (e.g. cheese, fermented foods) and as potential targets for pharmaceutical intervention in human diseases including hypertension, cancer, Alzheimer's disease, AIDS (acquired immune deficiency syndrome), and malaria. A deeper understanding of the structure and function of APs, therefore, will have a direct impact on the design of peptidase inhibitors developed to treat such diseases. Most APs are synthesized as zymogens which contain an N-terminal prosegment (PS) domain that is removed at acidic pH by proteolytic cleavage resulting in the active enzyme. While the nature of the AP PS function is not entirely understood, the PS can be important in processes such as the initiation of correct folding, protein stability, blockage of the active site, pH-dependence of activation, and intracellular sorting of the zymogen. This review summarizes the current knowledge of AP PS function (especially within the A1 family), with particular emphasis on protein folding, cellular sorting, and inhibition.
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Chen X, Ulintz PJ, Simon ES, Williams JA, Andrews PC. Global topology analysis of pancreatic zymogen granule membrane proteins. Mol Cell Proteomics 2008; 7:2323-36. [PMID: 18682380 DOI: 10.1074/mcp.m700575-mcp200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The zymogen granule is the specialized organelle in pancreatic acinar cells for digestive enzyme storage and regulated secretion and is a classic model for studying secretory granule function. Our long term goal is to develop a comprehensive architectural model for zymogen granule membrane (ZGM) proteins that would direct new hypotheses for subsequent functional studies. Our initial proteomics analysis focused on identification of proteins from purified ZGM (Chen, X., Walker, A. K., Strahler, J. R., Simon, E. S., Tomanicek-Volk, S. L., Nelson, B. B., Hurley, M. C., Ernst, S. A., Williams, J. A., and Andrews, P. C. (2006) Organellar proteomics: analysis of pancreatic zymogen granule membranes. Mol. Cell. Proteomics 5, 306-312). In the current study, a new global topology analysis of ZGM proteins is described that applies isotope enrichment methods to a protease protection protocol. Our results showed that tryptic peptides of ZGM proteins were separated into two distinct clusters according to their isobaric tag for relative and absolute quantification (iTRAQ) ratios for proteinase K-treated versus control zymogen granules. The low iTRAQ ratio cluster included cytoplasm-orientated membrane and membrane-associated proteins including myosin V, vesicle-associated membrane proteins, syntaxins, and all the Rab proteins. The second cluster having unchanged ratios included predominantly luminal proteins. Because quantification is at the peptide level, this technique is also capable of mapping both cytoplasm- and lumen-orientated domains from the same transmembrane protein. To more accurately assign the topology, we developed a statistical mixture model to provide probabilities for identified peptides to be cytoplasmic or luminal based on their iTRAQ ratios. By implementing this approach to global topology analysis of ZGM proteins, we report here an experimentally constrained, comprehensive topology model of identified zymogen granule membrane proteins. This model contributes to a firm foundation for developing a higher order architecture model of the ZGM and for future functional studies of individual ZGM proteins.
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Affiliation(s)
- Xuequn Chen
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.
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