251
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Abstract
Ubiquitin-positive deposits are histopathologically found in patients with Alzheimer's disease (AD). It is not understood why ubiquitin is accumulated in intra- and extra-cellular deposits or how it is involved in AD pathogenesis. Interestingly, recent evidence, including studies of E2-25K/Hip-2, has elucidated the molecular mechanism of the ubiquitin-proteasome system (UPS) malfunction in AD. The neurotoxicity and proteasome inhibition by Abeta, a main cause of AD pathogenesis, are mediated by increased E2-25K/Hip-2 in the brains of patients with AD. Furthermore, E2-25K/Hip-2 is required for the neurotoxicity that is mediated by a ubiquitin B mutant (UBB+1), which is a potent inhibitor of proteasomes that is found in patients with AD. Intensive research is required to identify the components of the UPS that are involved in AD pathogenesis.
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Affiliation(s)
- Sungmin Song
- Department of Life Science, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
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252
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Abstract
The amyloid-beta precursor protein is proteolytically cleaved by secretases, resulting in a series of fragments, including the amyloid-beta peptide of Alzheimer's disease. The amyloid precursor protein, when membrane anchored, could operate as a receptor. After cleavage, the soluble ectodomain exerts a trophic function in the subventricular zone. The amyloid-beta peptide itself has a depressant role in synaptic transmission, with both physiological and pathological implications. During the past two years, much time has been invested in determining the molecular pathways that regulate the processing and the signal transduction of the amyloid precursor protein. However, the absence of consistent and informative phenotypes in different loss of function animal models make elucidating the molecular actions of the amyloid-beta precursor protein an ongoing challenge.
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Affiliation(s)
- Valérie Wilquet
- Laboratory for Neuronal Cell Biology and Gene Transfer, K.U. Leuven and VIB, Department of Human Genetics, Herestraat 49, 3000 Leuven, Belgium.
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253
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Chin J, Palop JJ, Yu GQ, Kojima N, Masliah E, Mucke L. Fyn kinase modulates synaptotoxicity, but not aberrant sprouting, in human amyloid precursor protein transgenic mice. J Neurosci 2004; 24:4692-7. [PMID: 15140940 PMCID: PMC6729387 DOI: 10.1523/jneurosci.0277-04.2004] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Alzheimer's disease (AD), the most common neurodegenerative disorder, results in progressive degeneration of synapses and aberrant sprouting of axon terminals. The mechanisms underlying these seemingly opposing cellular phenomena are unclear. We hypothesized that Fyn kinase may play a role in one or both of these processes because it is increased in AD brains and because it is involved in synaptic plasticity and axonal outgrowth. We investigated the effects of Fyn on AD-related synaptotoxicity and aberrant axonal sprouting by ablating or overexpressing Fyn in human amyloid precursor protein (hAPP) transgenic mice. On the fyn+/+ background, hAPP/amyloid beta peptide (Abeta) decreased hippocampal levels of synaptophysin-immunoreactive presynaptic terminals (SIPTs), consistent with previous findings. On the fyn-/- background, hAPP/Abeta did not affect SIPTs. SIPT reductions correlated with hippocampal Abeta levels in hAPP/fyn+/+, but not hAPP/fyn-/-, mice suggesting that Fyn provides a critical link between hAPP/Abeta and SIPTs. Furthermore, overexpression of Fyn exacerbated SIPT reductions in hAPP mice. We also found that the susceptibility of mice to hAPP/Abeta-induced premature mortality was decreased by Fyn ablation and increased by Fyn overexpression. In contrast, axonal sprouting in the hippocampus of hAPP mice was unaffected. We conclude that Fyn-dependent pathways are critical in AD-related synaptotoxicity and that the pathogenesis of hAPP/Abeta-induced neuronal alterations may be mechanistically heterogenous.
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Affiliation(s)
- Jeannie Chin
- Gladstone Institute of Neurological Disease and Department of Neurology, University of California, San Francisco, California 94141-9100, USA
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254
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Wang Q, Rowan MJ, Anwyl R. Beta-amyloid-mediated inhibition of NMDA receptor-dependent long-term potentiation induction involves activation of microglia and stimulation of inducible nitric oxide synthase and superoxide. J Neurosci 2004; 24:6049-56. [PMID: 15240796 PMCID: PMC6729673 DOI: 10.1523/jneurosci.0233-04.2004] [Citation(s) in RCA: 153] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2004] [Revised: 05/25/2004] [Accepted: 05/25/2004] [Indexed: 11/21/2022] Open
Abstract
The mechanisms underlying the inhibition of long-term potentiation (LTP) induction by amyloidbeta-peptide (Abeta) were investigated in the medial perforant path of the rat and mouse dentate gyrus in vitro. Evidence is presented in this study that the Abeta-mediated inhibition of LTP induction involves activation of microglia and production of reactive oxygen and nitrogen species. In control slices, Abeta strongly inhibited induction of NMDA receptor-dependent (NMDAR-dependent) LTP, although not induction of NMDAR-independent LTP or long-term depression (LTD). The inhibition of NMDAR-dependent LTP was prevented by minocycline, an agent that prevents activation of microglia. The involvement of inducible nitric oxide synthase (iNOS) was shown by the inability of Abeta to inhibit LTP induction in iNOS knock-out mice and also by the ability of two iNOS inhibitors, aminoguanidine and 1400W, to prevent the Abeta-mediated inhibition of LTP induction. The Abeta-mediated inhibition of LTP induction also was prevented by the superoxide scavenger superoxide dismutase applied together with catalase. Evidence for involvement of superoxide in the action of Abeta on LTP induction was shown by the ability of an inhibitor of NADPH oxidase to prevent the Abeta-mediated inhibition of LTP induction. The study thus provides evidence that the Abeta-mediated inhibition of LTP induction involves an inflammatory-type reaction in which activation of microglia results in the production of nitric oxide and superoxide and thence possibly peroxynitrite, a highly reactive oxidant.
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Affiliation(s)
- Qinwen Wang
- Department of Physiology, Trinity College, Dublin 2, Ireland
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255
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Abstract
Studies on neural networks indicate that the pattern of amnesia that occurs in Alzheimer's disease (AD) can be reproduced by synaptic loss, but only when this loss is accompanied by synaptic scaling, a homeostatic mechanism that maintains the level of excitatory input on postsynaptic neurons. It is suggested that increased cholinergic activity during the early stages of AD contributes to synaptic scaling and that acetylcholinesterase inhibitors improve cognition in AD patients by boosting this mechanism.
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Affiliation(s)
- David H Small
- Laboratory of Molecular Neurobiology, Department of Biochemistry and Molecular Biology, Monash University, Victoria 3800, Australia.
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256
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Wang Q, Walsh DM, Rowan MJ, Selkoe DJ, Anwyl R. Block of long-term potentiation by naturally secreted and synthetic amyloid beta-peptide in hippocampal slices is mediated via activation of the kinases c-Jun N-terminal kinase, cyclin-dependent kinase 5, and p38 mitogen-activated protein kinase as well as metabotropic glutamate receptor type 5. J Neurosci 2004; 24:3370-8. [PMID: 15056716 PMCID: PMC6730034 DOI: 10.1523/jneurosci.1633-03.2004] [Citation(s) in RCA: 375] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The mechanisms of action of human synthetic and naturally secreted cell-derived amyloid beta-peptide (Abeta)(1-42) on the induction of long-term potentiation (LTP) were investigated in the medial perforant path to dentate granule cell synapses in hippocampal slices. Synthetic and cell-derived Abeta strongly inhibited high-frequency stimulation (HFS)-induced LTP at peak HFS and 1 hr after HFS. Cell-derived Abeta was much more potent than synthetic Abeta at inhibiting LTP induction, with threshold concentrations of approximately 1 and 100-200 nm, respectively. The involvement of various kinases in Abeta-mediated inhibition of LTP induction was investigated by applying Abeta in the presence of inhibitors of these kinases. The c-Jun N-terminal kinase (JNK) inhibitor JNKI prevented the block of LTP induction by both synthetic and cell-derived Abeta. The block of LTP induced by synthetic Abeta was also prevented by the JNK inhibitor anthra[1,9-cd]pyrazol-6(2H)-one, the cyclin-dependent kinase 5 (Cdk5) inhibitors butyrolactone and roscovitine, and the p38 MAP kinase (MAPK) inhibitor 4-(4-fluorophenyl)-2-(4-methylsulfonylphenyl)-5-(4-pyridyl)-1H-imidazole but not by the p42-p44 MAP kinase inhibitor 1,4-diamino-2,3-dicyano-1,4-bis(2-aminophenylthio)butadiene. The group I-group II metabotropic glutamate receptor (mGluR) antagonist 2S-2-amino-2-(1S,2S-2-carboxycyclopropyl-1-yl)-3-(xanth-9-yl)propanoic acid and the mGluR5 antagonist methyl-6-(phenylethynyl)pyridine prevented the block of LTP induction by Abeta. However, thealpha7 nicotinic ACh receptor antagonist methylcaconatine did not prevent the inhibition of LTP induction by Abeta. These studies provide evidence that the Abeta-mediated inhibition of LTP induction involves stimulation of the kinases JNK, Cdk5, and p38 MAPK after the activation of both the Abeta receptor(s) and mGluR5.
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Affiliation(s)
- Qinwen Wang
- Department of Physiology and Pharmacology, Trinity College, Dublin 2, Ireland
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257
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Wang Z, Chang L, Klein WL, Thatcher GRJ, Venton DL. Per-6-substituted-per-6-deoxy β-cyclodextrins Inhibit the Formation of β-Amyloid Peptide Derived Soluble Oligomers. J Med Chem 2004; 47:3329-33. [PMID: 15189029 DOI: 10.1021/jm034224e] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recent studies have indicated that the most important role of beta-amyloid peptide (Abeta) in the etiology of Alzheimer's disease may not be in plaque formation but in the formation of soluble, metastable Abeta(1-42) neurotoxic intermediates (called ADDLs). In the present work we describe the preparation of per-6-amino-6-deoxy-beta-cyclodextrins, which inhibit ADDLs formation in vitro.
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258
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Caillé I, Allinquant B, Dupont E, Bouillot C, Langer A, Müller U, Prochiantz A. Soluble form of amyloid precursor protein regulates proliferation of progenitors in the adult subventricular zone. Development 2004; 131:2173-81. [PMID: 15073156 DOI: 10.1242/dev.01103] [Citation(s) in RCA: 274] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The amyloid precursor protein (APP) is a type I transmembrane protein of unknown physiological function. Its soluble secreted form (sAPP) shows similarities with growth factors and increases the in vitro proliferation of embryonic neural stem cells. As neurogenesis is an ongoing process in the adult mammalian brain, we have investigated a role for sAPP in adult neurogenesis. We show that the subventricular zone (SVZ) of the lateral ventricle, the largest neurogenic area of the adult brain, is a major sAPP binding site and that binding occurs on progenitor cells expressing the EGF receptor. These EGF-responsive cells can be cultured as neurospheres (NS). In vitro, EGF provokes soluble APP (sAPP) secretion by NS and anti-APP antibodies antagonize the EGF-induced NS proliferation. In vivo, sAPP infusions increase the number of EGF-responsive progenitors through their increased proliferation. Conversely, blocking sAPP secretion or downregulating APP synthesis decreases the proliferation of EGF-responsive cells, which leads to a reduction of the pool of progenitors. These results reveal a new function for sAPP as a regulator of SVZ progenitor proliferation in the adult central nervous system.
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Affiliation(s)
- Isabelle Caillé
- CNRS UMR 8542, Ecole Normale Supérieure, 46 rue d'Ulm, 75005 Paris, France
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259
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Abstract
The cerebral reserve hypothesis is a heuristic concept used to explain apparent protection from the onset of cerebral disease and/or cognitive decline in old age. A significant obstacle when investigating the reserve hypothesis is the absence of baseline data with which to compare current cognitive status. We tested the influence of three hypothesized proxies of reserve (education, head size and occupational attainment [OCC]) in 92 volunteers born in 1921, whose cognitive function was measured at age 11 and 79 years, and who underwent brain MRI. The association between each proxy and old age cognitive function was tested, adjusting for variance contributed by childhood mental ability and detrimental age-related pathological changes measured using MRI. The results showed that education and OCC, but not total intracranial volume (TICV), contribute to cerebral reserve and help retain cognitive function in old age. Education was found to contribute between 5 and 6% of the variance found in old age memory function but was found to have no significant association with reasoning abilities. OCC was found to contribute around 5% of the variance found in old age memory function and between 6 and 8% of the variance found in old age reasoning abilities. We conclude that the intellectual challenges experienced during life, such as education and occupation, accumulate reserve and allow cognitive function to be maintained in old age.
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Affiliation(s)
- Roger T Staff
- Department of Bio-Medical Physics and Bioengineering, University of Aberdeen and Aberdeen Royal Infirmary, Foresterhill, UK.
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260
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Kasa P, Papp H, Kasa P, Pakaski M, Balaspiri L. Effects of amyloid-beta on cholinergic and acetylcholinesterase-positive cells in cultured basal forebrain neurons of embryonic rat brain. Brain Res 2004; 998:73-82. [PMID: 14725970 DOI: 10.1016/j.brainres.2003.11.021] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The neurotoxic effects of amyloid-beta(1-42) and amyloid-beta(25-35) (A beta) on cholinergic and acetylcholinesterase-positive neurons were investigated in primary cultures derived from embryonic 18-day-old rat basal forebrain. After various time intervals, the cultures were treated with 1, 5, 10 or 20 microM A beta for different time periods. The cholinergic neurons and their axon terminals were revealed by vesicular acetylcholine transporter immunohistochemistry and the cholinoceptive cells by acetylcholinesterase histochemical staining. To assess the toxic effects of these A beta peptides on the cholinergic neurons, image analysis was applied for quantitative determination of the numbers of axon varicosities/terminals and cells. The results demonstrate that, following treatment with 1 or 5 microM A beta for 5, 10, 30, 60 or 120 min, no changes in vesicular acetylcholine transporter immunohistochemical staining were observed. However, after treatment for 30 min with 10 or 20 microM A beta, the number of stained axon varicosities was reduced, and treatment for 2 h they had disappeared. In contrast, vesicular acetylcholine transporter-positivity could be seen in some of the neuronal perikarya even after 3 days after treatment. The acetylcholinesterase staining was homogeneously distributed in the control neurons. After A beta treatment, the histochemical reaction end-product was detected in some of the neuronal perikarya or in the dendritic processes near to the soma. It is concluded that the neurotoxic effects of A beta appear more rapidly in the cholinergic axon terminals than in the cholinergic and acetylcholinesterase-positive neuronal perikarya.
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Affiliation(s)
- Peter Kasa
- Alzheimer's Disease Research Centre, Department of Psychiatry, University of Szeged, Somogyi B. ut 4., Szeged H-6720, Hungary.
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261
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Hans A, Bajramovic JJ, Syan S, Perret E, Dunia I, Brahic M, Gonzalez-Dunia D. Persistent, non‐cytolytic infection of neurons by Borna disease virus interferes with ERK 1/2 signaling and abrogates BDNF‐induced synaptogenesis. FASEB J 2004; 18:863-5. [PMID: 15033926 DOI: 10.1096/fj.03-0764fje] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Infection of the central nervous system by Borna disease virus (BDV) provides a unique model to study the mechanisms whereby a persistent viral infection can impair neuronal function and cause behavioral diseases reminiscent of mood disorders, schizophrenia, or autism in humans. In the present work, we studied the effect of BDV infection on the response of hippocampal neurons, the main target for this virus, to the neurotrophin BDNF. We showed that persistent infection did not affect neuronal survival or morphology. However, it blocked BDNF-induced ERK 1/2 phosphorylation, despite normal expression of the TrkB BDNF receptor. In addition, BDNF-induced expression of synaptic vesicle proteins was abrogated, which resulted in severely impaired synaptogenesis and defects in synaptic organization. Thus, we provide the first evidence that a virus can interfere specifically with neurotrophin-regulated neuroplasticity, thereby hampering proper neuronal connectivity. These results may help to understand the behavioral disorders associated with BDV infection.
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Affiliation(s)
- Aymeric Hans
- Unité des Virus Lents, CNRS URA 1930, Institut Pasteur, Paris, France
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262
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Therianos S, Zhu M, Pyun E, Coleman PD. Single-channel quantitative multiplex reverse transcriptase-polymerase chain reaction for large numbers of gene products differentiates nondemented from neuropathological Alzheimer's disease. THE AMERICAN JOURNAL OF PATHOLOGY 2004; 164:795-806. [PMID: 14982834 PMCID: PMC1613270 DOI: 10.1016/s0002-9440(10)63168-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 12/04/2003] [Indexed: 10/18/2022]
Abstract
Effective approaches using array technologies are critical to understand the molecular bases of human diseases. The results obtained using such procedures require analysis and validation procedures that are still under development. In the context of Alzheimer's disease, in which the identification of molecular mechanisms of underlying pathologies is vital, we describe a robust assay that is the first real-time reverse transcriptase-polymerase chain reaction-based high-throughput approach that can simultaneously quantitate the expression of a large number of genes at the copy number level from a minute amount of starting material. Using this approach within the human brain, we were able to quantitate as many as 19 genes at a time with only one type of fluorescent probe. The number of genes included can be considerably increased. Examples of consistent changes in Alzheimer's disease within these 19 candidate genes included reductions in targets related to the dendritic and synaptic apparatus. These changes were specific to Alzheimer's disease when compared with Parkinson's disease cases. We also present comparison data with microarray analysis from the same brain region and the same patients. The high sensitivity and reproducibility of this technology coupled with appropriate multivariate analysis is proposed here to form a biotechnology platform that can be widely used for diagnostic purposes as well as basic research.
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Affiliation(s)
- Stavros Therianos
- Center for Aging and Developmental Biology, University of Rochester Medical Center, Rochester, New York 14610, USA.
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263
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Fodero LR, Mok SS, Losic D, Martin LL, Aguilar MI, Barrow CJ, Livett BG, Small DH. α7-Nicotinic acetylcholine receptors mediate an Aβ1−42-induced increase in the level of acetylcholinesterase in primary cortical neurones. J Neurochem 2004; 88:1186-93. [PMID: 15009674 DOI: 10.1046/j.1471-4159.2003.02296.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The beta-amyloid protein (Abeta) is the major protein component of amyloid plaques found in the Alzheimer brain. Although there is a loss of acetylcholinesterase (AChE) from both cholinergic and non-cholinergic neurones in the brain of Alzheimer patients, the level of AChE is increased around amyloid plaques. Previous studies using P19 cells in culture and transgenic mice which overexpress human Abeta have suggested that this increase may be due to a direct action of Abeta on AChE expression in cells adjacent to amyloid plaques. The aim of the present study was to examine the mechanism by which Abeta increases levels of AChE in primary cortical neurones. Abeta1-42 was more potent than Abeta1-40 in its ability to increase AChE in primary cortical neurones. The increase in AChE was unrelated to the toxic effects of the Abeta peptides. The effect of Abeta1-42 on AChE was blocked by inhibitors of alpha7 nicotinic acetylcholine receptors (alpha7 nAChRs) as well as by inhibitors of L- or N-type voltage-dependent calcium channels (VDCCs), whereas agonists of alpha7 nAChRs (choline, nicotine) increased the level of AChE. The results demonstrate that the effect of Abeta1-42 on AChE is due to an agonist effect of Abeta1-42 on the alpha7 nAChR.
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Affiliation(s)
- L R Fodero
- Department of Pathology, University of Melbourne, Parkville, Australia
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264
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Miledi R, Dueñas Z, Martinez-Torres A, Kawas CH, Eusebi F. Microtransplantation of functional receptors and channels from the Alzheimer's brain to frog oocytes. Proc Natl Acad Sci U S A 2004; 101:1760-3. [PMID: 14749517 PMCID: PMC341849 DOI: 10.1073/pnas.0308224100] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
About a decade ago, cell membranes from the electric organ of Torpedo and from the rat brain were transplanted to frog oocytes, which thus acquired functional Torpedo and rat neurotransmitter receptors. Nevertheless, the great potential that this method has for studying human diseases has remained virtually untapped. Here, we show that cell membranes from the postmortem brains of humans that suffered Alzheimer's disease can be microtransplanted to the plasma membrane of Xenopus oocytes. We show also that these postmortem membranes carry neurotransmitter receptors and voltage-operated channels that are still functional, even after they have been kept frozen for many years. This method provides a new and powerful approach to study directly the functional characteristics and structure of receptors, channels, and other membrane proteins of the Alzheimer's brain. This knowledge may help in understanding the basis of Alzheimer's disease and also help in developing new treatments.
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Affiliation(s)
- R Miledi
- Department of Neurobiology and Behavior, University of California, Irvine, CA 92697-4550, USA.
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265
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Popescu BO, Cedazo-Minguez A, Benedikz E, Nishimura T, Winblad B, Ankarcrona M, Cowburn RF. γ-Secretase Activity of Presenilin 1 Regulates Acetylcholine Muscarinic Receptor-mediated Signal Transduction. J Biol Chem 2004; 279:6455-64. [PMID: 14625299 DOI: 10.1074/jbc.m306041200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Familial Alzheimer's disease (FAD) presenilin 1 (PS1) mutations give enhanced calcium responses upon different stimuli, attenuated capacitative calcium entry, an increased sensitivity of cells to undergo apoptosis, and increased gamma-secretase activity. We previously showed that the FAD mutation causing an exon 9 deletion in PS1 results in enhanced basal phospholipase C (PLC) activity (Cedazo-Minguez, A., Popescu, B. O., Ankarcrona, M., Nishimura, T., and Cowburn, R. F. (2002) J. Biol. Chem. 277, 36646-36655). To further elucidate the mechanisms by which PS1 interferes with PLC-calcium signaling, we studied the effect of two other FAD PS1 mutants (M146V and L250S) and two dominant negative PS1 mutants (D257A and D385N) on basal and carbachol-stimulated phosphoinositide (PI) hydrolysis and intracellular calcium concentrations ([Ca2+]i) in SH-SY5Y neuroblastoma cells. We found a significant increase in basal PI hydrolysis in PS1 M146V cells but not in PS1 L250S cells. Both PS1 M146V and PS1 L250S cells showed a significant increase in carbachol-induced [Ca2+]i as compared with nontransfected or wild type PS1 transfected cells. The elevated carbachol-induced [Ca2+]i signals were reversed by the PLC inhibitor neomycin, the ryanodine receptor antagonist dantrolene, the general aspartyl protease inhibitor pepstatin A, and the specific gamma-secretase inhibitor N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester. The cells expressing either PS1 D257A or PS1 D385N had attenuated carbachol-stimulated PI hydrolysis and [Ca2+]i responses. In nontransfected or PS1 wild type transfected cells, N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester and pepstatin A also attenuated both carbachol-stimulated PI hydrolysis and [Ca2+]i responses to levels found in PS1 D257A or PS1 D385N dominant negative cells. Our findings suggest that PS1 can regulate PLC activity and that this function is gamma-secretase activity-dependent.
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Affiliation(s)
- Bogdan O Popescu
- Section of Experimental Geriatrics, Karolinska Institutet, Neurotec Department, Kliniskt Forskningscentrum, Novum, 141 86 Huddinge, Sweden
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266
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Abstract
Deciphering the molecular basis of synaptic dysfuction in Alzheimer's disease (AD) has engaged the attention of scientists with diverse backgrounds and interests. The synthesis of experimental findings from neuropathology, biochemistry, genetics, animal modeling and even immunology, has provided a plausible model for the pathogenesis of the disorder. While not universally accepted, the so-called amyloid (or Abeta) hypothesis of AD is well supported scientifically and predicts several specific targets for therapeutic intervention. Some of these are now reaching the clinic, providing the final and most important test for this hypothetical mechanism of disease.
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Affiliation(s)
- Dennis J Selkoe
- Center for Neurological Diseases, Brigham and Women's Hospital, and the Harvard Center for Neurodegeneration and Repair Boston, Massachusetts, USA.
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267
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Yao PJ. Synaptic frailty and clathrin-mediated synaptic vesicle trafficking in Alzheimer's disease. Trends Neurosci 2004; 27:24-9. [PMID: 14698607 DOI: 10.1016/j.tins.2003.10.012] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
- Pamela J Yao
- Laboratory of Neurosciences, National Institute on Aging/NIH, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA.
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268
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Hartmann J, Erb C, Ebert U, Baumann KH, Popp A, König G, Klein J. Central cholinergic functions in human amyloid precursor protein knock-in/presenilin-1 transgenic mice. Neuroscience 2004; 125:1009-17. [PMID: 15120860 DOI: 10.1016/j.neuroscience.2004.02.038] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/26/2004] [Indexed: 10/26/2022]
Abstract
Alzheimer's disease is characterized by amyloid peptide formation and deposition, neurofibrillary tangles, central cholinergic dysfunction, and dementia; however, the relationship between these parameters is not well understood. We studied the effect of amyloid peptide formation and deposition on central cholinergic function in knock-in mice carrying the human amyloid precursor protein (APP) gene with the Swedish/London double mutation (APP-SL mice) which were crossbred with transgenic mice overexpressing normal (PS1wt) or mutated (M146L; PS1mut) human presenilin-1. APP-SLxPS1mut mice had increased levels of Abeta peptides at 10 months of age and amyloid plaques at 14 months of age while APP-SLxPS1wt mice did not have increased peptide levels and did not develop amyloid plaques. We used microdialysis in 15-27 months old mice to compare hippocampal acetylcholine (ACh) levels in the two mouse lines and found that extracellular ACh levels were slightly but significantly reduced in the APP-SLxPS1mut mice (-26%; P=0.044). Exploratory activity in the open field increased hippocampal ACh release by two-fold in both mouse lines; total and relative increases were not significantly different for the two strains under study. Similarly, infusion of scopolamine (1 microM) increased hippocampal ACh release to a similar extent (3-5-fold) in both groups. High-affinity choline uptake, a measure of the ACh turnover rate, was identical in both mouse lines. Neurons expressing choline acetyltransferase were increased in the septum of APP-SLxPS1mut mice (+26%; P=0.046). We conclude that amyloid peptide production causes a small decrease of extracellular ACh levels. The deposition of amyloid plaques, however, does not impair stimulated ACh release and proceeds without major changes of central cholinergic function.
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Affiliation(s)
- J Hartmann
- Alzheimer Research Group, Bayer Health Care AG, D-42096 Wuppertal, Germany
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269
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Smith IF, Boyle JP, Green KN, Pearson HA, Peers C. Hypoxic remodelling of Ca2+ mobilization in type I cortical astrocytes: involvement of ROS and pro-amyloidogenic APP processing. J Neurochem 2003; 88:869-77. [PMID: 14756807 DOI: 10.1046/j.1471-4159.2003.02212.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Chronic hypoxia (CH) alters Ca2+ homeostasis in various cells and may contribute to disturbed Ca2+ homeostasis of Alzheimer's disease. Here, we have employed microfluorimetric measurements of [Ca2+]i to investigate the mechanism underlying augmentation of Ca2+ signalling by chronic hypoxia in type I cortical astrocytes. Application of bradykinin evoked significantly larger rises of [Ca2+]i in hypoxic cells as compared with control cells. This augmentation was prevented fully by either melatonin (150 micro m) or ascorbic acid (200 micro m), indicating the involvement of reactive oxygen species. Given the association between hypoxia and increased production of amyloid beta peptides (AbetaPs) of Alzheimer's disease, we performed immunofluorescence studies to show that hypoxia caused a marked and consistent increased staining for AbetaPs and presenilin-1 (PS-1). Western blot experiments also confirmed that hypoxia increased PS-1 protein levels. Hypoxic increases of AbetaP production was prevented with inhibitors of either gamma- or beta-secretase. These inhibitors also partially prevented the augmentation of Ca2+ signalling in astrocytes. Our results indicate that chronic hypoxia enhances agonist-evoked rises of [Ca2+]i in cortical astrocytes, and that this can be prevented by antioxidants and appears to be associated with increased AbetaP formation.
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Affiliation(s)
- Ian F Smith
- Institute for Cardiovascular Research School of Biomedical Sciences, University of Leeds, Leeds, UK
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270
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Ghochikyan A, Vasilevko V, Petrushina I, Movsesyan N, Babikyan D, Tian W, Sadzikava N, Ross T, Head E, Cribbs DH, Agadjanyan MG. Generation and characterization of the humoral immune response to DNA immunization with a chimeric beta-amyloid-interleukin-4 minigene. Eur J Immunol 2003; 33:3232-41. [PMID: 14635031 PMCID: PMC1524857 DOI: 10.1002/eji.200324000] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Active immunization with fibrillar beta-amyloid peptide (Abeta(42)) as well as passive transfer of anti-Abeta antibodies significantly reduces Abeta plaque deposition, neuritic dystrophy, and astrogliosis in the brain of mutant amyloid precursor protein (APP)-transgenic mice. Although the mechanism(s) of clearance of Abeta from the brain following active or passive immunization remains to be determined, it is clear that anti-Abeta antibodies are critical for clearance. DNA immunization provides an attractive alternative to direct peptide and adjuvant approaches for inducing a humoral response to Abeta. We constructed a DNA minigene with Abeta fused to mouse interleukin-4 (pAbeta(42)-IL-4) as a molecular adjuvant to generate anti-Abeta antibodies and enhance the Th2-type of immune responses. Gene gun immunizations induced primarily IgG1 and IgG2b anti-Abeta antibodies. Fine epitope analysis with overlapping peptides of the Abeta(42) sequence identified the 1-15 region as a dominant B cell epitope. The DNA minigene-induced anti-Abeta antibodies bound to Abeta plaques in brain tissue from an Alzheimer's disease patient demonstrating functional activity of the antibodies and the potential for therapeutic efficacy.
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Affiliation(s)
- Anahit Ghochikyan
- The Institute for Molecular Medicine, Department of Immunology, Huntington Beach, USA
| | - Vitaly Vasilevko
- The Institute for Molecular Medicine, Department of Immunology, Huntington Beach, USA
| | - Irina Petrushina
- The Institute for Brain Aging and Dementia, University of California, Irvine, USA
| | - Nina Movsesyan
- The Institute for Molecular Medicine, Department of Immunology, Huntington Beach, USA
| | - Davit Babikyan
- The Institute for Molecular Medicine, Department of Immunology, Huntington Beach, USA
| | - Wenqiang Tian
- Department of Molecular Biology and Biochemistry, University of California, Irvine, USA
| | - Nadya Sadzikava
- The Institute for Brain Aging and Dementia, University of California, Irvine, USA
| | - TedM. Ross
- Department of Microbiology and Immunology, East Carolina University School of Medicine, Greenville, USA
| | - Elizabeth Head
- The Institute for Brain Aging and Dementia, University of California, Irvine, USA
| | - David H. Cribbs
- The Institute for Brain Aging and Dementia, University of California, Irvine, USA
| | - Michael G. Agadjanyan
- The Institute for Molecular Medicine, Department of Immunology, Huntington Beach, USA
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271
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Caughey B, Lansbury PT. Protofibrils, pores, fibrils, and neurodegeneration: separating the responsible protein aggregates from the innocent bystanders. Annu Rev Neurosci 2003; 26:267-98. [PMID: 12704221 DOI: 10.1146/annurev.neuro.26.010302.081142] [Citation(s) in RCA: 1263] [Impact Index Per Article: 60.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Many neurodegenerative diseases, including Alzheimer's and Parkinson's and the transmissible spongiform encephalopathies (prion diseases), are characterized at autopsy by neuronal loss and protein aggregates that are typically fibrillar. A convergence of evidence strongly suggests that protein aggregation is neurotoxic and not a product of cell death. However, the identity of the neurotoxic aggregate and the mechanism by which it disables and eventually kills a neuron are unknown. Both biophysical studies aimed at elucidating the precise mechanism of in vitro aggregation and animal modeling studies support the emerging notion that an ordered prefibrillar oligomer, or protofibril, may be responsible for cell death and that the fibrillar form that is typically observed at autopsy may actually be neuroprotective. A subpopulation of protofibrils may function as pathogenic amyloid pores. An analogous mechanism may explain the neurotoxicity of the prion protein; recent data demonstrates that the disease-associated, infectious form of the prion protein differs from the neurotoxic species. This review focuses on recent experimental studies aimed at identification and characterization of the neurotoxic protein aggregates.
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Affiliation(s)
- Byron Caughey
- NIAID, National Institutes of Health, Rocky Mountain Laboratories, Hamilton, Montana, USA.
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272
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Small DH, Fodero LR, Losic D, Chu C, Aguilar MI, Martin LL, Chebib M. Role of A β and the α 7 nicotinic acetylcholine receptor in regulating synaptic plasticity in Alzheimer's disease. Int J Pept Res Ther 2003. [DOI: 10.1007/s10989-004-2390-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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273
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Small DH, Smith AI. Proteases and proteolytic processing in the nervous system: Key targets for drug development. J Neurosci Res 2003. [DOI: 10.1002/jnr.10782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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274
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Age-dependent impairment of somatosensory response in the amyloid precursor protein 23 transgenic mouse model of Alzheimer's disease. J Neurosci 2003. [PMID: 12967984 DOI: 10.1523/jneurosci.23-23-08231.2003] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Quantitative functional magnetic resonance imaging was applied to characterize brain function in amyloid precursor protein 23 (APP23) transgenic mice, which reproduce the neuropathological alterations associated with Alzheimer's disease. Electrical stimulation of the paw led to cerebral blood volume increases in the contralateral somatosensory cortex. In APP23 mice this hemodynamic response decreased with increasing age of the animal and with increasing stimulus amplitude as compared with wild-type animals. The age-dependent dysfunction in APP23 mice may be attributed in part to a compromised cerebrovascular reactivity. Quantitative functional brain mapping that uses standardized sensory inputs should allow for assessment of disease progression and therapy response (e.g., passive immunization against beta-amyloid) in patients also.
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275
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Role of Aβ and the α7 nicotinic acetylcholine receptor in regulating synaptic plasticity in Alzheimer's disease. Int J Pept Res Ther 2003. [DOI: 10.1007/bf02442570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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276
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Song S, Kim SY, Hong YM, Jo DG, Lee JY, Shim SM, Chung CW, Seo SJ, Yoo YJ, Koh JY, Lee MC, Yates AJ, Ichijo H, Jung YK. Essential Role of E2-25K/Hip-2 in Mediating Amyloid-β Neurotoxicity. Mol Cell 2003; 12:553-63. [PMID: 14527403 DOI: 10.1016/j.molcel.2003.08.005] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The ubiquitin/proteasome system has been proposed to play an important role in Alzheimer's disease (AD) pathogenesis. However, the critical factor(s) modulating both amyloid-beta peptide (Abeta) neurotoxicity and ubiquitin/proteasome system in AD are not known. We report the isolation of an unusual ubiquitin-conjugating enzyme, E2-25K/Hip-2, as a mediator of Abeta toxicity. The expression of E2-25K/Hip-2 was upregulated in the neurons exposed to Abeta(1-42) in vivo and in culture. Enzymatic activity of E2-25K/Hip-2 was required for both Abeta(1-42) neurotoxicity and inhibition of proteasome activity. E2-25K/Hip-2 functioned upstream of apoptosis signal-regulating kinase 1 (ASK1) and c-Jun N-terminal kinase (JNK) in Abeta(1-42) toxicity. Further, the ubiquitin mutant, UBB+1, a potent inhibitor of the proteasome which is found in Alzheimer's brains, was colocalized and functionally interacted with E2-25K/Hip-2 in mediating neurotoxicity. These results suggest that E2-25K/Hip-2 is a crucial factor in regulating Abeta neurotoxicity and could play a role in the pathogenesis of Alzheimer's disease.
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Affiliation(s)
- Sungmin Song
- Department of Life Science, Kwangju Institute of Science and Technology, Kwangju 500-712, South Korea
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277
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Abstract
Glutamate is the major transmitter of the brain and is involved in all aspects of cognitive function since it is the transmitter of cortical and hippocampal pyramidal neurones. Furthermore, glutamate and glutamate receptors are involved in long-term potentiation, a process believed to underlie learning and memory. Histological studies indicate loss of pyramidal neurones and their synapses in Alzheimer's disease (AD), this together with biochemical evidence suggests presynaptic (and postsynaptic) glutamatergic hypoactivity. This represents a 'double blow' as the activity of glutamatergic neurones is heavily influenced by the cholinergic system, which is also dysfunctional in AD. The clinical relevance of these changes is emphasised because glutamatergic and cholinergic dysfunction are strong correlates of cognitive decline in AD. The mechanism by which glutamatergic (and cholinergic) cells die is likely to be a combination of necrosis and apoptosis caused by a range of factors which include tangle formation and the effects of too much and too little glutamatergic neurotransmission.
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Affiliation(s)
- Paul T Francis
- Centre for Neuroscience Research, King's College London, London, UK.
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278
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Abstract
The amyloid precursor protein and the proteases cleaving this protein are important players in the pathogenesis of Alzheimer's disease via the generation of the amyloid peptide. Physiologically, the amyloid precursor protein is implied in axonal vesicular trafficking and the proteases are implicated in developmentally important signaling pathways, most significantly those involving regulated intramembrane proteolysis or RIP. We discuss the cell biology behind the amyloid and tangle hypothesis for Alzheimer's disease, drawing on the many links to the fields of cell biology and developmental biology that have been established in the recent years.
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Affiliation(s)
- Wim Annaert
- Neuronal Cell Biology Laboratory, Flanders Interuniversity Institute for Biotechnology (VIB) and Catholic University of Leuven, Center for Human Genetics Herestraat 49, Belgium
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279
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Gu Z, Zhong P, Yan Z. Activation of muscarinic receptors inhibits beta-amyloid peptide-induced signaling in cortical slices. J Biol Chem 2003; 278:17546-56. [PMID: 12606559 DOI: 10.1074/jbc.m209892200] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Deposition of fibrillar aggregates of the beta-amyloid peptide (Abeta) is a key pathologic feature during the early stage of Alzheimer's disease. The initial neuronal responses to Abeta in cortical circuits and the regulation of Abeta-induced signaling remain unclear. In this study, we found that exposure of cortical slices to Abeta(1-42) or Abeta(25-35) induced a marked increase in the activation of protein kinase C (PKC) and Ca(2+)/calmodulin-dependent kinase II (CaMKII), two enzymes critically involved in a variety of cellular functions. Activation of M1 muscarinic receptors, but not nicotinic receptors, significantly inhibited the Abeta activation of PKC and CaMKII. Increasing inhibitory transmission mimicked the M1 effect on Abeta, whereas blocking GABA(A) receptors eliminated the M1 action. Moreover, electrophysiological evidence shows that application of Abeta to cortical slices induced action potential firing and enhanced excitatory postsynaptic currents, whereas muscarinic agonists potently increased inhibitory postsynaptic currents. These results suggest that Abeta activates PKC and CaMKII through enhancing excitatory activity in glutamatergic synaptic networks. Activation of M1 receptors inhibits Abeta signaling by enhancing the counteracting GABA(ergic) inhibitory transmission. Thus the muscarinic reversal of the Abeta-induced biochemical and physiological changes provides a potential mechanism for the treatment of Alzheimer's disease with cholinergic enhancers.
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Affiliation(s)
- Zhenglin Gu
- Department of Physiology and Biophysics, State University of New York at Buffalo, School of Medicine and Biomedical Sciences, Buffalo, New York 14214, USA
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280
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Turner PR, O'Connor K, Tate WP, Abraham WC. Roles of amyloid precursor protein and its fragments in regulating neural activity, plasticity and memory. Prog Neurobiol 2003; 70:1-32. [PMID: 12927332 DOI: 10.1016/s0301-0082(03)00089-3] [Citation(s) in RCA: 483] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Amyloid-beta precursor protein (APP) is a membrane-spanning protein with a large extracellular domain and a much smaller intracellular domain. It is the source of the amyloid-beta (Abeta) peptide found in neuritic plaques of Alzheimer's disease (AD) patients. Because Abeta shows neurotoxic properties, and because familial forms of AD promote Abeta accumulation, a massive international research effort has been aimed at understanding the mechanisms of Abeta generation, catabolism and toxicity. APP, however, is an extremely complex molecule that may be a functionally important molecule in its full-length configuration, as well as being the source of numerous fragments with varying effects on neural function. For example, one fragment derived from the non-amyloidogenic processing pathway, secreted APPalpha (sAPPalpha), is neuroprotective, neurotrophic and regulates cell excitability and synaptic plasticity, while Abeta appears to exert opposing effects. Less is known about the neural functions of other fragments, but there is a growing interest in understanding the basic biology of APP as it has become recognized that alterations in the functional activity of the APP fragments during disease states will have complex effects on cell function. Indeed, it has been proposed that reductions in the level or activity of certain APP fragments, in addition to accumulation of Abeta, may play a critical role in the cognitive dysfunction associated with AD, particularly early in the course of the disease. To test and modify this hypothesis, it is important to understand the roles that full-length APP and its fragments normally play in neuronal structure and function. Here we review evidence addressing these fundamental questions, paying particular attention to the contributions that APP fragments play in synaptic transmission and neural plasticity, as these may be key to understanding their effects on learning and memory. It is clear from this literature that APP fragments, including Abeta, can exert a powerful regulation of key neural functions including cell excitability, synaptic transmission and long-term potentiation, both acutely and over the long-term. Furthermore, there is a small but growing literature confirming that these fragments correspondingly regulate behavioral learning and memory. These data indicate that a full account of cognitive dysfunction in AD will need to incorporate the actions of the full complement of APP fragments. To this end, there is an urgent need for a dedicated research effort aimed at understanding the behavioral consequences of altered levels and activity of the different APP fragments as a result of experience and disease.
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Affiliation(s)
- Paul R Turner
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
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281
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Bendiske J, Bahr BA. Lysosomal activation is a compensatory response against protein accumulation and associated synaptopathogenesis--an approach for slowing Alzheimer disease? J Neuropathol Exp Neurol 2003; 62:451-63. [PMID: 12769185 DOI: 10.1093/jnen/62.5.451] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Previous reports suggest that age-related lysosomal disturbances contribute to Alzheimer-type accumulations of protein species, blockage of axonal/dendritic transport, and synaptic decline. Here, we tested the hypothesis that lysosomal enzymes are upregulated as a compensatory response to pathogenic protein accumulation. In the hippocampal slice model, tau deposits and amyloidogenic fragments induced by the lysosomal inhibitor chloroquine were accompanied by disrupted microtubule integrity and by corresponding declines in postsynaptic glutamate receptors and the presynaptic marker synaptophysin. In the same slices, cathepsins B, D, and L, beta-glucuronidase, and elastase were upregulated by 70% to 135%. To address whether this selective activation of the lysosomal system represents compensatory signaling, N-Cbz-L-phenylalanyl-L-alanyl-diazomethylketone (PADK) was used to enhance the lysosome response, generating 4- to 8-fold increases in lysosomal enzymes. PADK-mediated lysosomal modulation was stable for weeks while synaptic components remained normal. When PADK and chloroquine were co-infused, chloroquine no longer increased cellular tau levels. To assess pre-existing pathology, chloroquine was applied for 6 days after which its removal resulted in continued degeneration. In contrast, enhancing lysosomal activation by replacing chloroquine after 6 days with PADK led to clearance of accumulated protein species and restored microtubule integrity. Transport processes lost during chloroquine exposure were consequently re-established, resulting in marked recovery of synaptic components. These data indicate that compensatory activation of lysosomes follows protein accumulation events, and that lysosomal modulation represents a novel approach for treating Alzheimer disease and other protein deposition diseases.
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Affiliation(s)
- Jennifer Bendiske
- Department of Pharmaceutical Sciences and the Neurosciences Program, University of Connecticut, Stors, Connecticut, USA
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282
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Reilly JF, Games D, Rydel RE, Freedman S, Schenk D, Young WG, Morrison JH, Bloom FE. Amyloid deposition in the hippocampus and entorhinal cortex: quantitative analysis of a transgenic mouse model. Proc Natl Acad Sci U S A 2003; 100:4837-42. [PMID: 12697936 PMCID: PMC153642 DOI: 10.1073/pnas.0330745100] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Various transgenic mouse models of Alzheimer's disease (AD) have been developed that overexpress mutant forms of amyloid precursor protein in an effort to elucidate more fully the potential role of beta-amyloid (A beta) in the etiopathogenesis of the disease. The present study represents the first complete 3D reconstruction of A beta in the hippocampus and entorhinal cortex of PDAPP transgenic mice. A beta deposits were detected by immunostaining and thioflavin fluorescence, and quantified by using high-throughput digital image acquisition and analysis. Quantitative analysis of amyloid load in hippocampal subfields showed a dramatic increase between 12 and 15 months of age, with little or no earlier detectable deposition. Three-dimensional reconstruction in the oldest brains visualized previously unrecognized sheets of A beta coursing through the hippocampus and cerebral cortex. In contrast with previous hypotheses, compact plaques form before significant deposition of diffuse A beta, suggesting that different mechanisms are involved in the deposition of diffuse amyloid and the aggregation into plaques. The dentate gyrus was the hippocampal subfield with the greatest amyloid burden. Sublaminar distribution of A beta in the dentate gyrus correlated most closely with the termination of afferent projections from the lateral entorhinal cortex, mirroring the selective vulnerability of this circuit in human AD. This detailed temporal and spatial analysis of A beta and compact amyloid deposition suggests that specific corticocortical circuits express selective, but late, vulnerability to the pathognomonic markers of amyloid deposition, and can provide a basis for detecting prior vulnerability factors.
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283
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Abstract
The regulated intramembrane proteolysis of the amyloid precursor protein (APP) that results in the generation of a toxic 40 to 42 amino acid fragment, Abeta, and a C-terminal intracellular fragment stands central in the pathogenesis of Alzheimer's disease. The fibrillar Abeta peptide is extracellularly deposited in plaques in the amygdala, the hippocampus, and the neocortex of affected individuals. The APP intracellular fragment binds to transcription factors and is translocated to the nucleus, where it influences transcription. Regulated intramembrane proteolysis of APP is dependent on the activity of a multimeric protein complex of which the essential components are presenilin, nicastrin, PEN-2, and APH-1. Further research into this emerging field of presenilin-dependent APP proteolysis within the plane of the membrane might reveal the necessity of an additional transport step-bringing substrate and enzyme together-before APP can actually be processed.
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Affiliation(s)
- Geert Van Gassen
- Neuronal Member Trafficking Laboratory, Department of Human Genetics, Flanders Interuniversity Institute of Biotechnology (VIB04), Gasthuisberg, KULeuven, Herestraat 49, B-3000 Leuven, Belgium
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284
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Butowt R, von Bartheld CS. Connecting the dots: trafficking of neurotrophins, lectins and diverse pathogens by binding to the neurotrophin receptor p75NTR. Eur J Neurosci 2003; 17:673-80. [PMID: 12603257 DOI: 10.1046/j.1460-9568.2003.02497.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The common receptor for neurotrophins, p75, has important roles in internalization and trafficking of neurotrophins along axons. Recent studies show that an astonishing array of proteins, including lectins, pathogens and neurotoxins, bind the p75 receptor, suggesting that they can hijack and utilize this receptor for trafficking between neuronal populations within the nervous system. Such pathogens include the neurologically important rabies viruses, prion proteins, beta-amyloid and possibly tetanus toxin. These proteins may hijack existing transport machineries designed to traffick neurotrophins, thus allowing the infiltration and distribution of pathogens and toxins among vulnerable neuronal populations with devastating effects, as seen in rabies, prion encephalopathies, Alzheimer's disease and tetanic muscle spasm. The discovery of an entry and transport machinery that is potentially shared between pathogens and neurotrophins sheds light ono trafficking systems in the nervous system and may assist the design of novel therapeutic avenues that prevent or slow the progression of diverse chronic and acute neurological disorders.
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Affiliation(s)
- Rafal Butowt
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
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285
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Subasinghe S, Unabia S, Barrow CJ, Mok SS, Aguilar MI, Small DH. Cholesterol is necessary both for the toxic effect of Abeta peptides on vascular smooth muscle cells and for Abeta binding to vascular smooth muscle cell membranes. J Neurochem 2003; 84:471-9. [PMID: 12558967 DOI: 10.1046/j.1471-4159.2003.01552.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Accumulation of beta amyloid (Abeta) in the brain is central to the pathogenesis of Alzheimer's disease. Abeta can bind to membrane lipids and this binding may have detrimental effects on cell function. In this study, surface plasmon resonance technology was used to study Abeta binding to membranes. Abeta peptides bound to synthetic lipid mixtures and to an intact plasma membrane preparation isolated from vascular smooth muscle cells. Abeta peptides were also toxic to vascular smooth muscle cells. There was a good correlation between the toxic effect of Abeta peptides and their membrane binding. 'Ageing' the Abeta peptides by incubation for 5 days increased the proportion of oligomeric species, and also increased toxicity and the amount of binding to lipids. The toxicities of various Abeta analogs correlated with their lipid binding. Significantly, binding was influenced by the concentration of cholesterol in the lipid mixture. Reduction of cholesterol in vascular smooth muscle cells not only reduced the binding of Abeta to purified plasma membrane preparations but also reduced Abeta toxicity. The results support the view that Abeta toxicity is a direct consequence of binding to lipids in the membrane. Reduction of membrane cholesterol using cholesterol-lowering drugs may be of therapeutic benefit because it reduces Abeta-membrane binding.
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286
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Novel therapeutic approach for the treatment of Alzheimer's disease by peripheral administration of agents with an affinity to beta-amyloid. J Neurosci 2003. [PMID: 12514198 DOI: 10.1523/jneurosci.23-01-00029.2003] [Citation(s) in RCA: 236] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Plaques containing beta-amyloid (Abeta) peptides are one of the pathological features of Alzheimer's disease, and the reduction of Abeta is considered a primary therapeutic target. Amyloid clearance by anti-Abeta antibodies has been reported after immunization, and recent data have shown that the antibodies may act as a peripheral sink for Abeta, thus altering the periphery/brain dynamics. Here we show that peripheral treatment with an agent that has high affinity for Abeta (gelsolin or GM1) but that is unrelated to an antibody or immune modulator reduced the level of Abeta in the brain, most likely because of a peripherally acting effect. We propose that in general, compounds that sequester plasma Abeta could reduce or prevent brain amyloidosis, which would enable the development of new therapeutic agents that are not limited by the need to penetrate the brain or evoke an immune response.
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287
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Fisher A, Brandeis R, Haring R, Bar-Ner N, Kliger-Spatz M, Natan N, Sonego H, Marcovitch I, Pittel Z. Impact of muscarinic agonists for successful therapy of Alzheimer's disease. JOURNAL OF NEURAL TRANSMISSION. SUPPLEMENTUM 2003:189-202. [PMID: 12456063 DOI: 10.1007/978-3-7091-6139-5_18] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2023]
Abstract
The M1 muscarinic agonists AF102B, AF150(S) & AF267B--i) restored cognitive impairments in several animal models for AD with an excellent safety margin; ii) elevated alpha-APPs levels; iii) attenuated vicious cycles induced by A beta, and inhibited A beta- and oxidative stress-induced apoptosis; and iv) decreased tau hyperphosphorylation. AF150(S) and AF267B were more effectve than rivastigmine and nicotine in restoring memory impairments in mice with small hippocampi. In apolipoprotein E-knockout mice, AF150(S) restored cognitive impairments and cholinergic hypofunction and decreased tau hyperphosphorylation. In aged microcebes, AF150(S) restored cognitive and behavioral impairments and decreased tau hyperphosphorylation, paired helical filaments and astrogliosis. In rabbits, AF267B & AF150(S) decreased CSF A beta(1-42 & 1-40), while AF102B reduced A beta(1-40). Finally AF102B decreased CSF A beta(total) in AD patients. Taken together, M1 agonists may represent a unique therapy in AD due to their beneficial effects on three major hallmarks of AD--cholinergic hypofunction, A beta and tau protein hyperphosphorylation.
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Affiliation(s)
- A Fisher
- Israel Institute for Biological Research, Ness-Ziona, Israel.
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288
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Uchida Y. Overexpression of full-length but not N-terminal truncated isoform of microtubule-associated protein (MAP) 1B accelerates apoptosis of cultured cortical neurons. J Biol Chem 2003; 278:366-71. [PMID: 12376528 DOI: 10.1074/jbc.m210091200] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
beta-amyloid (Abeta) is presumed to play a pathogenic role in Alzheimer's disease (AD). However, there is an imperfect correlation between Abeta deposition and neuronal loss or dementia. To clarify neuronal responses to Abeta, Abeta-induced gene expression in cultured cortical neurons was analyzed by differential display followed by Northern blotting. Here we report that nonaggregated or aggregated Abeta induced microtubule-associated protein 1B (MAP1B) mRNA, especially the alternative transcript containing exon 3U, before disruption of the cell membrane by Abeta. An alternative transcript containing exon 3U is translated into an N-terminal truncated shorter isoform of MAP1B. Transfection experiments reveal that overexpression of this isoform does not accelerate neurite outgrowth or apoptosis of cortical neurons. In contrast, overexpression of MAP1B fragments containing the N-terminal 126 amino acids promoted neurite outgrowth and neuronal apoptosis. These results suggest that Abeta does not induce deleterious full-length MAP1B directly, but overexpression of full-length MAP1B might act as an effector of cell death in neurodegenerative disorders related to cytoskeletal abnormalities.
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Affiliation(s)
- Yoko Uchida
- Gene Expression Research Group, Division of Neuroscience and Brain Function, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakaecho, Itabashiku, Tokyo 173-0015, Japan.
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289
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Golde TE. Alzheimer disease therapy: can the amyloid cascade be halted? J Clin Invest 2003; 111:11-8. [PMID: 12511580 PMCID: PMC151845 DOI: 10.1172/jci17527] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Affiliation(s)
- Todd E Golde
- Department of Neuroscience, Mayo Clinic Jacksonville, Jacksonville, Florida 32224, USA.
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290
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Kim HJ, Chae SC, Lee DK, Chromy B, Lee SC, Park YC, Klein WL, Krafft GA, Hong ST. Selective neuronal degeneration induced by soluble oligomeric amyloid beta protein. FASEB J 2003; 17:118-20. [PMID: 12424218 DOI: 10.1096/fj.01-0987fje] [Citation(s) in RCA: 163] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The prevailing amyloid hypothesis for Alzheimer's disease (AD) holds that amyloid beta-protein (Abeta) causes neuronal degeneration by forming neurotoxic fibrillar structures. Yet, many aspects of AD pathology and symptoms are not well explained by this hypothesis. Here, we present evidence that neurotoxicity of soluble oligomeric Abeta closely corresponds to the selective neurodegeneration so distinctly manifest in AD. Selectivity was first observed in vitro, where only the human central nervous system neuronal cells were susceptible to soluble oligomeric Abeta. Furthermore, in mouse cerebral slice treated with soluble oligomeric Abeta, selective regiospecific toxicity was evident in the hippocampal CA1, a division important for memory, but not in the CA3 subfield. The fibrillar Abeta, however, killed neurons in all regions of the cerebral slice cultures and also in cerebellar slices. Remarkably, even at the highest soluble oligomeric Abeta concentrations, cerebellar neurons were completely spared, consistent with one of the hallmark features of AD pathology. Our observation of the selective neurodegeneration of soluble oligomeric Abeta to neurons involved in cognitive function may provide a new opportunity for the development of an effective AD therapy as well as elucidating the pathological mechanism of AD.
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Affiliation(s)
- Hyeon-Jin Kim
- Research Division, Jinis Biopharmaceuticals Co., Chonju, Chonbuk, South Korea
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291
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292
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Kawahara M. Aluminum-Induced Conformational Changes of .BETA.-Amyloid Protein and the Pathogenesis of Alzheimer's Disease. ACTA ACUST UNITED AC 2003. [DOI: 10.1248/jhs.49.341] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Masahiro Kawahara
- Department of Analytical Chemistry, School of Pharmaceutical Sciences, Kyushu University of Health and Welfare
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293
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Greenfield S, Vaux DJ. Parkinson's disease, Alzheimer's disease and motor neurone disease: identifying a common mechanism. Neuroscience 2002; 113:485-92. [PMID: 12150769 DOI: 10.1016/s0306-4522(02)00194-x] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Although Alzheimer's disease, Parkinson's disease, and motor neurone disease are distinct disorders, there could be a common neurodegenerative mechanism that characterises the death of selective neurone populations in each case. We propose that this mechanism could be an aberrantly activated, developmental process involving a non-classical, non-enzymatic action of acetylcholinesterase mediated via a short linear motif near the C-terminal end of the molecule. Since this motif has a highly conserved homology with part of the amyloid precursor protein, it may be particularly attractive as a target for novel therapeutic strategies in neurodegeneration.
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Affiliation(s)
- S Greenfield
- University Department of Pharmacology, Mansfield Road, OX1 3QT, Oxford, UK.
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294
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Abstract
Multiple lines of evidence implicate lysosomes in a variety of pathogenic events that produce neurodegeneration. Genetic mutations that cause specific enzyme deficiencies account for more than 40 lysosomal storage disorders. These mostly pre-adult diseases are associated with abnormal brain development and mental retardation. Such disorders are characterized by intracellular deposition and protein aggregation, events also found in age-related neurodegenerative diseases including (i) Alzheimer's disease and related tauopathies (ii) Lewy body disorders and synucleinopathies such as Parkinson's disease, and (iii) Huntington's disease and other polyglutamine expansion disorders. Of particular interest for this review is evidence that alterations to the lysosomal system contribute to protein deposits associated with different types of age-related neurodegeneration. Lysosomes are in fact highly susceptible to free radical oxidative stress in the aging brain, leading to the gradual loss of their processing capacity over the lifespan of an individual. Several studies point to this lysosomal disturbance as being involved in amyloidogenic processing, formation of paired helical filaments, and the aggregation of alpha-synuclein and mutant huntingtin proteins. Most notably, experimentally induced lysosomal dysfunction, both in vitro and in vivo, recapitulates important pathological features of age-related diseases including the link between protein deposition and synaptic loss.
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Affiliation(s)
- Ben A Bahr
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs, CT 06269-2092, USA.
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295
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McLaurin J, Cecal R, Kierstead ME, Tian X, Phinney AL, Manea M, French JE, Lambermon MHL, Darabie AA, Brown ME, Janus C, Chishti MA, Horne P, Westaway D, Fraser PE, Mount HTJ, Przybylski M, St George-Hyslop P. Therapeutically effective antibodies against amyloid-beta peptide target amyloid-beta residues 4-10 and inhibit cytotoxicity and fibrillogenesis. Nat Med 2002; 8:1263-9. [PMID: 12379850 DOI: 10.1038/nm790] [Citation(s) in RCA: 328] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2002] [Accepted: 10/01/2002] [Indexed: 11/09/2022]
Abstract
Immunization of transgenic mouse models of Alzheimer disease using amyloid-beta peptide (Abeta) reduces both the Alzheimer disease-like neuropathology and the spatial memory impairments of these mice. However, a therapeutic trial of immunization with Abeta42 in humans was discontinued because a few patients developed significant meningo-encephalitic cellular inflammatory reactions. Here we show that beneficial effects in mice arise from antibodies selectively directed against residues 4-10 of Abeta42, and that these antibodies inhibit both Abeta fibrillogenesis and cytotoxicity without eliciting an inflammatory response. These findings provide the basis for improved immunization antigens as well as attempts to design small-molecule mimics as alternative therapies.
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Affiliation(s)
- J McLaurin
- Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Ontario, Canada.
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296
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Abstract
In its earliest clinical phase, Alzheimer's disease characteristically produces a remarkably pure impairment of memory. Mounting evidence suggests that this syndrome begins with subtle alterations of hippocampal synaptic efficacy prior to frank neuronal degeneration, and that the synaptic dysfunction is caused by diffusible oligomeric assemblies of the amyloid beta protein.
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Affiliation(s)
- Dennis J Selkoe
- Center for Neurologic Diseases, Brigham and Women's Hospital, and the Harvard Center for Neurodegeneration and Repair, Boston, MA 02115, USA.
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297
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Liu Y, Qin L, Wilson BC, An L, Hong JS, Liu B. Inhibition by naloxone stereoisomers of beta-amyloid peptide (1-42)-induced superoxide production in microglia and degeneration of cortical and mesencephalic neurons. J Pharmacol Exp Ther 2002; 302:1212-9. [PMID: 12183682 DOI: 10.1124/jpet.102.035956] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previously we reported that naloxone stereoisomers, in an opioid receptor-independent manner, attenuated the inflammation-mediated degeneration of dopaminergic neurons by inhibition of the activation of microglia, the resident immune cells in the brain. Recently we discovered that beta-amyloid peptide Abeta (1-42) exhibited enhanced neurotoxicity toward both cortical and mesencephalic neurons through the activation of microglia and production of superoxide. The purpose of this study was to determine whether naloxone isomers had any effect on Abeta (1-42)-induced neurodegeneration. Pretreatment of either cortical or mesencephalic neuron-glia cultures with 1 to 10 microM (-)-naloxone, prior to treatment for up to 11 days with 0.1 to 3 microM Abeta (1-42), afforded significant neuroprotection as judged by neurotransmitter uptake, immunocytochemical analysis, and cell counting. More importantly, (+)-naloxone, the ineffective enantiomer of (-)-naloxone in binding opioid receptors, was equally effective in affording neuroprotection. Mechanistically, inhibition of Abeta (1-42)-induced production of superoxide in microglia underlay the neuroprotective effect of naloxone stereoisomers. Moreover, neuroprotection and inhibition of Abeta (1-42)-induced superoxide production was also achieved with naloxone methiodide, a charged analog with quaternary amine, suggesting that the site of action for naloxone isomers is at the cell surface of microglia. These results demonstrated that naloxone isomers, through mechanisms unrelated to the opioid receptors, were capable of inhibiting Abeta (1-42)-induced microglial activation and degeneration of both cortical and mesencephalic neurons. Combined with our previous observations with inflammagen-induced neurodegeneration, naloxone analogs, especially (+)-naloxone, may have potential therapeutic efficacy for the treatment of Alzheimer's and Parkinson's disease.
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Affiliation(s)
- Yuxin Liu
- Neuropharmacology Section, Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences/NIH, Research Triangle Park, NC 27709, USA.
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298
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Kourie JI, Henry CL. Ion channel formation and membrane-linked pathologies of misfolded hydrophobic proteins: the role of dangerous unchaperoned molecules. Clin Exp Pharmacol Physiol 2002; 29:741-53. [PMID: 12165037 DOI: 10.1046/j.1440-1681.2002.03737.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. Protein-membrane interaction includes the interaction of proteins with intrinsic receptors and ion transport pathways and with membrane lipids. Several hypothetical interaction models have been reported for peptide-induced membrane destabilization, including hydrophobic clustering, electrostatic interaction, electrostatic followed by hydrophobic interaction, wedge x type incorporation and hydrophobic mismatch. 2. The present review focuses on the hypothesis of protein interaction with lipid membranes of those unchaperoned positively charged and misfolded proteins that have hydrophobic regions. We advance the hypothesis that protein misfolding that leads to the exposure of hydrophobic regions of proteins renders them potentially cytotoxic. Such proteins include prion, amyloid beta protein (AbetaP), amylin, calcitonin, serum amyloid and C-type natriuretic peptides. These proteins have the ability to interact with lipid membranes, thereby inducing membrane damage and cell malfunction. 3. We propose that the most significant mechanism of membrane damage induced by hydrophobic misfolded proteins is mediated via the formation of ion channels. The hydrophobicity based toxicity of several proteins linked to neurodegenerative pathologies is similar to those observed for antibacterial toxins and viral proteins. 4. It is hypothesized that the membrane damage induced by amyloids, antibacterial toxins and viral proteins represents a common mechanism for cell malfunction, which underlies the associated pathologies and cytotoxicity of such proteins.
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Affiliation(s)
- Joseph I Kourie
- Membrane Transport Group, Department of Chemistry, The Faculties, The Australian National University, Science Road, Canberra, ACT 0200, Australia. joseph.kourie@@anu.edu.au
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299
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Ikegaya Y, Matsuura S, Ueno S, Baba A, Yamada MK, Nishiyama N, Matsuki N. Beta-amyloid enhances glial glutamate uptake activity and attenuates synaptic efficacy. J Biol Chem 2002; 277:32180-6. [PMID: 12070161 DOI: 10.1074/jbc.m203764200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although amyloid beta-protein (A beta) has long been implicated in the pathogenesis of Alzheimer's disease, little is known about the mechanism by which A beta causes dementia. A beta leads to neuronal cell death in vivo and in vitro, but recent evidence suggests that the property of the amnesic characteristic of Alzheimer's disease can be explained by a malfunction of synapses rather than a loss of neurons. Here we show that prolonged treatment with A beta augments the glutamate clearance ability of cultured astrocytes and induces a dramatic decrease in glutamatergic synaptic activity of neurons cocultured with the astrocytes. Biotinylation assay revealed that the enhancement of glutamate uptake activity was associated with an increase in cell-surface expression of GLAST, a subtype of glial glutamate transporters, without apparent changes in the total amount of GLAST. This phenomenon was blocked efficiently by actin-disrupting agents. Thus, A beta-induced actin-dependent GLAST redistribution and relevant synaptic malfunction may be a cellular basis for the amnesia of Alzheimer's disease.
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Affiliation(s)
- Yuji Ikegaya
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan.
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300
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Niwa K, Kazama K, Younkin L, Younkin SG, Carlson GA, Iadecola C. Cerebrovascular autoregulation is profoundly impaired in mice overexpressing amyloid precursor protein. Am J Physiol Heart Circ Physiol 2002; 283:H315-23. [PMID: 12063304 DOI: 10.1152/ajpheart.00022.2002] [Citation(s) in RCA: 209] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The amyloid-beta (A beta) peptide, which is derived from the amyloid precursor protein (APP), is involved in the pathogenesis of Alzheimer's dementia and impairs endothelium-dependent vasodilation in cerebral vessels. We investigated whether cerebrovascular autoregulation, i.e., the ability of the cerebral circulation to maintain flow in the face of changes in mean arterial pressure (MAP), is impaired in transgenic mice that overexpress APP and A beta. Neocortical cerebral blood flow (CBF) was monitored by laser-Doppler flowmetry in anesthetized APP(+) and APP(-) mice. MAP was elevated by intravenous infusion of phenylephrine and reduced by controlled exsanguination. In APP(-) mice, autoregulation was preserved. However, in APP(+) mice, autoregulation was markedly disrupted. The magnitude of the disruption was linearly related to brain A beta concentration. The failure of autoregulation was paralleled by impairment of the CBF response to endothelium-dependent vasodilators. Thus A beta disrupts a critical homeostatic mechanism of the cerebral circulation and renders CBF highly dependent on MAP. The resulting alterations in cerebral perfusion may play a role in the brain dysfunction and periventricular white-matter changes associated with Alzheimer's dementia.
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Affiliation(s)
- Kiyoshi Niwa
- Department of Neurology, University of Minnesota, Minneapolis, Minnesota 55455, USA
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