1.
Substance P activates ADAM9 mRNA expression and induces α-secretase-mediated amyloid precursor protein cleavage.
Source
Institute of Cell Biology and Neurobiology, CNR, Via del Fosso di Fiorano, 65, 00143 Rome, Italy.
Abstract
Altered levels of Substance P (SP), a neuropeptide endowed with neuroprotective and anti-apoptotic properties, were found in brain areas and spinal fluid of Alzheimer's disease (AD) patients. One of the hallmarks of AD is the abnormal extracellular deposition of neurotoxic beta amyloid (Aβ) peptides, derived from the proteolytic processing of amyloidprecursor protein (APP). In the present study, we confirmed, the neurotrophic action of SP in cultured rat cerebellar granule cells (CGCs) and investigated its effects on APP metabolism. Incubation with low (5 mM) potassium induced apoptotic cell death of CGCs and amyloidogenic processing of APP, whereas treatment with SP (200 nM) reverted these effects via NK1 receptors. The non-amyloidogenic effect of SP consisted of reduction of Aβ(1-42), increase of sAPPα and enhanced α-secretase activity, without a significant change in steady-state levels of cellular APP. The intracellular mechanisms whereby SP alters APP metabolism were further investigated by measuring mRNA and/or steady-state protein levels of key enzymes involved with α-, β- and γ-secretase activity. Among them, Adam9, both at the mRNA and protein level, was the only enzyme to be significantly down-regulated following the induction of apoptosis (K5) and up-regulated after SP treatment. In addition to its neuroprotective properties, this study shows that SP is able to stimulate non-amyloidogenic APP processing, thereby reducing the possibility of generation of toxic Aβ peptides in brain.
Copyright © 2011 Elsevier Ltd. All rights reserved.
- PMID:
- 22244942
- [PubMed - as supplied by publisher]
An ELISA-based Method to Quantify the Association of Small Molecules with Aggregated Amyloid Peptides.
Abstract
This paper describes a simple ELISA protocol for quantifying the binding of small molecules to aggregated Amyloid-β (Aβ) peptides. Amyloid-targeting small molecules have attracted wide interest as potential agents for the treatment or diagnosis of neurodegenerative disorders such as Alzheimer´s disease. The lack of general methods to evaluate small molecule-amyloid binding interactions, however, has significantly limited the number of amyloid-targeting molecules that have been studied to date. Here, we demonstrate a general method to quantify small molecule-amyloid binding interactions via a modified quantitative ELISA protocol. A key feature of this protocol is the treatment of commercial ELISA plates with an air plasma to help maintain the desired β-sheet content of the aggregated Aβ upon immobilization of these peptides on to the polystyrene surface. We developed an ELISA-based competition assay on these air plasma-treated plates and evaluated the binding of five previously known amyloid-binding small molecules to aggregated Aβ. We show that this general ELISA-based competition assay can be used to quantify small molecule-amyloid binding interactions in the low nanomolar to low micromolar range, which is the typical range of affinities for many amyloid-targeting diagnostic agents under current development. This simple protocol for quantifying the interaction of small molecules with aggregated Aβ peptides overcomes many limitations of previously reported spectroscopic or radioactivity assays, and may, therefore, facilitate the screening and evaluation of a more structurally diverse set of amyloid-targeting agents than had previously been possible.
- PMID:
- 22243436
- [PubMed - as supplied by publisher]
Amyloid-Derived Peptide Forms Self-Assembled Monolayers on Gold Nanoparticle with a Curvature-Dependent β-Sheet Structure.
Abstract
Using a combination of Fourier transform infrared (FTIR) spectroscopy and solid state nuclear magnetic resonance (SSNMR) techniques, the secondary structure of peptides anchored on gold nanoparticles of different sizes is investigated. The structure of the well studied CALNN-capped nanoparticles is compared to the structure of nanoparticles capped with a new cysteine-terminated peptide, CFGAILSS. The design of that peptide is derived from the minimal amyloidogenic sequence FGAIL of the human islet polypeptide amylin. We demonstrate that CFGAILSS forms extended fibrils in solution. When constrained at a nanoparticle surface, CFGAILSS adopts a secondary structure markedly different from CALNN. Taking into account the surface selection rules, the FTIR spectra of CFGAILSS-capped gold nanoparticles indicate the formation of β-sheets which are more prominent for 25 nm diameter nanoparticles than for 5 nm nanoparticles. No intermolecular 13C-13C dipolar coupling is detected with rotational resonance SSNMR for CALNN-capped nanoparticles while CALNN is in a random coil configuration. Coupling is detected for CFGAILSS-capped gold nanoparticles, however, consistent with an intermolecular 13C-13C distance of 5.0 Å ± 0.3 Å in agreement with intermolecular hydrogen bonding in a parallel β-sheet structure.
- PMID:
- 22242947
- [PubMed - as supplied by publisher]
Probing Structural Features of Alzheimer's Amyloid-β Pores in Bilayers Using Site-Specific Amino Acid Substitutions.
Source
Department of Bioengineering, Department of Mechanical and Aerospace Engineering, and Material Science Program, University of California, San Diego , La Jolla, California 92093, United States.
Abstract
A current hypothesis for the pathology of Alzheimer's disease (AD) proposes that amyloid-β (Aβ) peptides induce uncontrolled, neurotoxic ion flux across cellular membranes. The mechanism of ion flux is not fully understood because no experiment-based Aβ channel structures at atomic resolution are currently available (only a few polymorphic states have been predicted by computational models). Structural models and experimental evidence lend support to the view that the Aβ channel is an assembly of loosely associated mobile β-sheet subunits. Here, using planar lipid bilayers and molecular dynamics (MD) simulations, we show that amino acid substitutions can be used to infer which residues are essential for channel structure. We created two Aβ(1-42) peptides with point mutations: F19P and F20C. The substitution of Phe19 with Pro inhibited channel conductance. MD simulation suggests a collapsed pore of F19P channels at the lower bilayer leaflet. The kinks at the Pro residues in the pore-lining β-strands induce blockage of the solvated pore by the N-termini of the chains. The cysteine mutant is capable of forming channels, and the conductance behavior of F20C channels is similar to that of the wild type. Overall, the mutational analysis of the channel activity performed in this work tests the proposition that the channels consist of a β-sheet rich organization, with the charged/polar central strand containing the mutation sites lining the pore, and the C-terminal strands facing the hydrophobic lipid tails. A detailed understanding of channel formation and its structure should aid studies of drug design aiming to control unregulated Aβ-dependent ion fluxes.
- PMID:
- 22242635
- [PubMed - as supplied by publisher]
β-Amyloid peptide is internalized into chick retinal neurons and alters the distribution of myosin Vb.
Source
Instituto de Bioquímica Médica - Universidade Federal do Rio de Janeiro; Departamento de Biociências da Atividade Física - Escola da Educação Física e Desportos - Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-902, Brazil.
Abstract
The most common neurodegenerative disorder afflicting the aging human population is Alzheimer's disease. A major hallmark of Alzheimer's disease is dementia from a loss of neuronal function, attributed to the presence and accumulation of β-amyloid peptide into senile plaques. Preceding senile plaque formation, abnormalities in axons can be observed as changes in morphologies and intracellular trafficking. Recently, it has been recognized that β-amyloid also accumulates within neurons and this intraneuronal β-amyloid accumulation has been reported to be critical in the disruption of synapses and cognitive function. Here we report on the internalization of a fluorescently labeled β-amyloidpeptide into cultured chick retinal neurons. The pattern of β-amyloid distribution during the time course of incubation is reminiscent of the endocytic pathway. Furthermore, the distribution of the internalized β-amyloid peptide converges with that of myosin Vb and both relocalize from the axon to cell body. These observations are consistent with the hypothesis that Alzheimer's disease proceeds as a result of an imbalance between β-amyloid production and β-amyloid clearance, suggesting a role for myosin Vb in this process. © 2012 Wiley Periodicals, Inc.
Copyright © 2012 Wiley Periodicals, Inc.
A novel study on amyloid beta peptide 40, 42 and 40/42 ratio in Saudi autistics.
Abstract
ABSTRACT: Objectives: We examined whether plasma concentrations of amyloid beta (Abeta) as protein derivatives play a central role in the etiology of autistic features. Design and Methods: Concentrations of human Abeta (1-42), Abeta (1-40), and Abeta (40/42) in the plasma of 52 autistic children (aged 3-16 years) and 36 age-matched control subjects were determined by using the ELISA technique and were compared. Results: Compared to control subjects, autistic children exhibited significantly lower concentrations of both Abeta (1-40) and Abeta (1-42) and lower Abeta (40/42) concentration ratio. Receiver operating characteristics curve (ROC) analysis showed that these measurements of Abeta peptides showed high specificity and sensitivity in distinguishing autistic children from control subjects. Conclusions: Lower concentrations of Abeta (1-42) and Abeta (1-40) were attributed to loss of Abeta equilibrium between the brain and blood, an imbalance that may lead to failure to draw Abeta from the brain and/or impairment of beta- and gamma- secretase's concentration or kinetics as enzymes involving in Abeta production.
Presenilin Is the Molecular Target of Acidic γ-Secretase Modulators in Living Cells.
Source
Department of Neuropathology, Heinrich-Heine-University, Duesseldorf, Germany.
Abstract
The intramembrane-cleaving protease γ-secretase catalyzes the last step in the generation of toxic amyloid-β (Aβ)peptides and is a principal therapeutic target in Alzheimer's disease. Both preclinical and clinical studies have demonstrated that inhibition of γ-secretase is associated with prohibitive side effects due to suppression of Notch processing and signaling. Potentially safer are γ-secretase modulators (GSMs), which are small molecules that selectively lower generation of the highly amyloidogenic Aβ42 peptides but spare Notch processing. GSMs with nanomolar potency and favorable pharmacological properties have been described, but the molecular mechanism of GSMs remains uncertain and both the substrate amyloid precursor protein (APP) and subunits of the γ-secretase complex have been proposed as the molecular target of GSMs. We have generated a potent photo-probe based on an acidic GSM that lowers Aβ42 generation with an IC(50) of 290 nM in cellular assays. By combining in vivo photo-crosslinking with affinity purification, we demonstrated that this probe binds the N-terminal fragment of presenilin (PSEN), the catalytic subunit of the γ-secretase complex, in living cells. Labeling was not observed for APP or any of the other γ-secretase subunits. Binding was readily competed by structurally divergent acidic and non-acidic GSMs suggesting a shared mode of action. These findings indicate that potent acidic GSMs target presenilin to modulate the enzymatic activity of the γ-secretase complex.
Effects of NK-4 in a Transgenic Mouse Model of Alzheimer's Disease.
Source
Research Center, Hayashibara Biochemical Laboratories, Inc., Okayama, Japan.
Abstract
Beta-amyloid (Aβ) peptides are considered to play a major role in the pathogenesis of Alzheimer's disease (AD) and molecules that can prevent pathways of Aβ toxicity may be potential therapeutic agents for treatment of AD. We have previously reported that NK-4, a cyanine photosensitizing dye, displays neurotrophic and antioxidant activities. In this study, we report the effects of NK-4 on the toxicity of Aβ and on cognitive function and Aβ concentration in a transgenic mouse model of AD (Tg2576). In vitro, NK-4 effectively protected neuronal cells from toxicity induced by Aβ. In addition, it displayed profound inhibitory activities on Aβ fibril formation. In vivo, Tg2576 mice received an intraperitoneal injection at 100 or 500 µg/kg of NK-4 once a day, five times a week for 9 months. Administration of NK-4 to the mice attenuated impairment of recognition memory, associative memory, and learning ability, as assessed by a novel object recognition test, a passive avoidance test, and a water maze test, respectively. NK-4 decreased the brain Aβ concentration while increasing the plasma amyloid level in a dose-dependent manner. NK-4 also improved memory impairments of ICR mice induced by direct intracerebroventricular administration of Aβ. These lines of evidence suggest that NK-4 may affect multiple pathways of amyloid pathogenesis and could be useful for treatment of AD.
Aβ delays fibrin clot lysis by altering fibrin structure and attenuating plasminogen binding to fibrin.
Source
Laboratory of Neurobiology and Genetics, The Rockefeller University, New York, NY, United States.
Abstract
Alzheimer's disease is characterized by the presence of increased levels of the beta-amyloid peptide (Aβ) in the brain parenchyma and cerebral blood vessels. This accumulated Aβ can bind to fibrin(ogen) and render fibrin clots more resistant to degradation. Here, we demonstrate that Aβ(42) specifically binds to fibrin and induces a tighter fibrin network characterized by thinner fibers and increased resistance to lysis. Aβ(42)-induced structural changes cannot be the sole mechanism of delayed lysis, however, since Aβ overlaid on normal pre-formed clots also binds to fibrin and delays lysis without altering clot structure. In this regard, we show that Aβ interferes with the binding of plasminogen to fibrin, which could impair plasmin generation and fibrin degradation. Indeed, plasmin generation by tPA, but not streptokinase, is slowed in fibrin clots containing Aβ(42), and clot lysis by plasmin, but not trypsin, is delayed. Notably, plasmin and tPA activities, as well as tPA-dependent generation of plasmin in solution, are not decreased in the presence of Aβ(42). Our results indicate the existence of two mechanisms of Aβ(42) involvement in delayed fibrinolysis: 1) through the induction of a tighter fibrin network composed of thinner fibers; and 2) through inhibition of plasmin(ogen)'s binding to fibrin.
Peptides for therapy and diagnosis of Alzheimer's disease.
Source
Dieter Willbold, Forschungszentrum Jülich, ICS-6, D-52425 Jülich, Germany. d.willbold@fz-juelich.de.
Abstract
Alzheimer's disease (AD) is a progressive neurodegenerative disorder with devastating effects. The greatest risk factor to develop AD is age. Today, only symptomatic therapies are available. Additionally, AD can be diagnosed with certainty only post mortem, whereas the diagnosis "probable AD" can be established earliest when severe clinical symptoms appear. Specific neuropathological changes like neurofibrillary tangles and amyloid plaques define AD. Amyloid plaques are mainly composed of the amyloid-β peptide (Aβ). Several lines of evidence suggest that the progressive concentration and subsequent aggregation and accumulation of Aβ play a fundamental role in the disease progress. Therefore, substances which bind to Aβ and influence aggregation thereof are of great interest. An enormous number of organic substances for therapeutic purposes are described. This review focuses on peptides developed for diagnosis and therapy of AD and discusses the pre- and disadvantages of peptide drugs.
- PMID:
- 22236121
- [PubMed - as supplied by publisher]
Amyloid-β oligomers induce differential gene expression in adult human brain slices.
Source
Federal University of Rio de Janeiro, Brazil;
Abstract
Cognitive decline in Alzheimers disease (AD) is increasingly attributed to the neuronal impact of soluble oligomers of theamyloid-β peptide (AβOs). Current knowledge on the molecular and cellular mechanisms underlying the toxicity of AβOs stems largely from rodent-derived cell/tissue culture experiments or from transgenic models of AD, which do not necessarily recapitulate the complexity of the human disease. Here, we used DNA microarray and RT-PCR to investigate changes in transcription in adult human cortical slices exposed to sub-lethal doses of AβOs. Results revealed a set of 27 genes that showed consistent differential expression upon exposure of slices from three different donors to AβOs. Functional classification of differentially expressed genes revealed that AβOs impact pathways important for neuronal physiology and known to be dysregulated in AD, including vesicle trafficking, cell adhesion, actin cytoskeleton dynamics and insulin signaling. Most genes (70%) were down-regulated by AβO treatment, suggesting a predominantly inhibitory effect on the corresponding pathways. Significantly, AβOs induced downregulation of synaptophysin, a presynaptic vesicle membrane protein, suggesting a mechanism by which oligomers cause synapse failure. Results provide insight into early mechanisms of pathogenesis of AD, and suggest that the neuronal pathways affected by AβOs may be targets for development of novel diagnostic or therapeutic approaches.
Structural Basis of β-Amyloid-Dependent Synaptic Dysfunctions.
Source
Max Planck Research Unit for Enzymology of Protein Folding, & MLU, Weinbergweg 22, 06120 Halle (Saale) (Germany).
Abstract
Learn about Alzheimer: The molecular conformation of a toxic β-amyloid oligomer structure was determined by NMR spectroscopy. The measurements show a N-terminal β strand that controls the partitioning between oligomer and protofibril formation. Targeting the N-terminus of the peptide neutralizes Aβ-dependent neuronal dysfunctions. The data have important implications for understanding the structural basis of Alzheimer's disease.
Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
[Compensatory function of transthyretin in Alzheimer's disease].
Abstract
Alzheimer's disease (AD) is the most common form of age-related primary neurodegenerative diseases characterized by progressive memory loss, aphasia, and intellectual and mental breakdown. Pathogenesis of AD is based on the early synaptic dysfunction following neurodegeneration and neuronal death. According to modern concepts, the development of neuropathological processes is due to progressively deposited intermediates of amyloid fibrils that represent oligomers consisting of short peptide named amyloid beta protein (Abeta). In this context, it is reasonable to propose that one of the compensatory mechanisms of AD might be inhibition of Abeta oligomerization by sequestration or clearance of Abeta. Experiments with transgenic animals and epidemiological studies demonstrate that major protein of cerebrospinal fluid, transthyretin, is a natural neuroprotector that inhibits Abeta amyloid formation and restore cognitive functions. The study of Abeta-transthyretin complexes allowed to create peptides that are mimetics of transthyretin. These mimetics inhibit amyloid formation in vitro and, therefore, could be used in therapeutic treatment of AD.
- PMID:
- 22232933
- [PubMed - in process]
Proteomic changes in cerebrospinal fluid of presymptomatic and affected persons carrying familial Alzheimer disease mutations.
Source
Mary S. Easton Center for Alzheimer's Disease Research, 10911 Weyburn Ave, Ste 200, Los Angeles, CA 90095. jringman@mednet.ucla.edu.
Abstract
OBJECTIVE:
To identify cerebrospinal fluid (CSF) protein changes in persons who will develop familial Alzheimer disease (FAD) due to PSEN1 and APP mutations, using unbiased proteomics.
DESIGN:
We compared proteomic profiles of CSF from individuals with FAD who were mutation carriers (MCs) and related noncarriers (NCs). Abundant proteins were depleted and samples were analyzed using liquid chromatography-electrospray ionization-mass spectrometry on a high-resolution time-of-flight instrument. Tryptic peptides were identified by tandem mass spectrometry. Proteins differing in concentration between the MCs and NCs were identified.
SETTING:
A tertiary dementia referral center and a proteomic biomarker discovery laboratory.
PARTICIPANTS:
Fourteen FAD MCs (mean age, 34.2 years; 10 are asymptomatic, 12 have presenilin-1 [PSEN1 ] gene mutations, and 2 have amyloid precursor protein [APP ] gene mutations) and 5 related NCs (mean age, 37.6 years).
RESULTS:
Fifty-six proteins were identified, represented by multiple tryptic peptides showing significant differences between MCs and NCs (46 upregulated and 10 downregulated); 40 of these proteins differed when the analysis was restricted to asymptomatic individuals. Fourteen proteins have been reported in prior proteomic studies in late-onset AD, including amyloid precursor protein, transferrin, α(1)β-glycoprotein, complement components, afamin precursor, spondin 1, plasminogen, hemopexin, and neuronal pentraxin receptor. Many other proteins were unique to our study, including calsyntenin 3, AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) 4 glutamate receptor, CD99 antigen, di- N-acetyl-chitobiase, and secreted phosphoprotein 1.
CONCLUSIONS:
We found much overlap in CSF protein changes between individuals with presymptomatic and symptomatic FAD and those with late-onset AD. Our results are consistent with inflammation and synaptic loss early in FAD and suggest new presymptomatic biomarkers of potential usefulness in drug development.
Characterization of Insulin Degrading Enzyme and Other Amyloid-β Degrading Proteases in Human Serum: A Role in Alzheimer's Disease?
Source
Departments of Pharmacology and Experimental Therapeutics, Boston University Medical Campus, Boston, MA, USA Departments of Anesthesiology, The Second People's Hospital of Shenzhen, PR China.
Abstract
Sporadic Alzheimer's disease (AD) patients have low amyloid-β peptide (Aβ) clearance in the central nervous system. The peripheral Aβ clearance may also be important but its role in AD remains unclear. We aimed to study the Aβ degrading proteases including insulin degrading enzyme (IDE), angiotensin converting enzyme (ACE) and others in blood. Using the fluorogenic substrate V (a substrate of IDE and other metalloproteases), we showed that human serum degraded the substrate V, and the activity was inhibited by adding increasing dose of Aβ. The existence of IDE activity was demonstrated by the inhibition of insulin, amylin, or EDTA, and further confirmed by immunocapture of IDE using monoclonal antibodies. The involvement of ACE was indicated by the ability of the ACE inhibitor, lisinopril, to inhibit the substrate V degradation. To test the variations of substrate V degradation in humans, we used serum samples from a homebound elderly population with cognitive diagnoses. Compared with the elderly who had normal cognition, those with probable AD and amnestic mild cognitive impairment (amnestic MCI) had lower peptidase activities. Probable AD or amnestic MCI as an outcome remained negatively associated with serum substrate V degradation activity after adjusting for the confounders. The elderly with probable AD had lower serum substrate V degradation activity compared with those who had vascular dementia. The blood proteases mediating Aβ degradation may be important for the AD pathogenesis. More studies are needed to specify each Aβ degrading protease in blood as a useful biomarker and a possible treatment target for AD.
Identification of Putative Molecular Imaging Probes for BACE-1 by Accounting for Protein Flexibility in Virtual Screening.
Source
Center for Molecular Medicine, School of Life Science and Biotechnology, Dalian University of Technology, Dalian, PR China.
Abstract
β-secretase (BACE-1), an enzyme critical in the process of amyloid-β (Aβ) peptides deposition in human brain, is closely associated with the onset and progression of Alzheimer's disease (AD). A strong need exists, therefore, to identify molecular imaging probes homing at BACE-1 for use with positron emission tomography (PET) that is recognized as an effective tool for detecting AD. Through this imaging, an early diagnosis of AD could be made. Herein, to identify suitable molecular probes for use with PET, we searched the Molecular Imaging and Contrast Agent Database (MICAD), an online database warehousing scientific information regarding molecular imaging and contrast agents, and applied a virtual screening approach against the different confirmations of BACE-1 obtained from the World Wide Protein Database. The lack of considering receptor flexibility is a key drawback in virtual screening for drug discovery. Therefore, we incorporated protein flexibility into the virtual screening by using an ensemble of 143 experimental BACE-1 structures derived from the Protein Data Bank. Finally, the best performing affinity was recorded and used in the ranking of each ligand. To the best of our knowledge, this is the first virtual screening approach used to identify four new molecular probes that could target BACE-1 with favorable affinity, a discovery that can lead to the development of new PET probes for the early detection and therapy of AD. However, the actual utility of these probes can only be ascertained after in vitro and in vivo investigations.
Therapeutic Albumin Binding to Remove Amyloid-β
Source
Instituto Grifols S.A., Research & Development Area, Polígon Llevant, Parets del Vallès, Barcelona, Spain.
Abstract
Clearance of plasma amyloid-β (Aβ) through plasma exchange and replacement with therapeutic albumin to facilitate net Aβ efflux from the brain to plasma is a novel approach for the treatment of Alzheimer's disease. Therefore, thorough characterization of the capacity of therapeutic albumin to bind Aβ is warranted. In this study, Aβ40 and Aβ42 were quantified by commercial ELISA or Araclon ABtest® in samples of Grifols' therapeutic albumin (Albutein®) 5%, 20%, and 25%. The capacity of Albutein® to bind Aβ was assessed by: a) ELISA in serially diluted therapeutic albumin (0-45 mg/ml protein concentration) to which 80 pg/ml of synthetic Aβ peptide (sAβ40 or sAβ42) were added; b) ELISA in samples of the therapeutic albumin containing serially diluted sAβ40 or sAβ42 (60-400 pg/ml); and c) surface plasmon resonance (SPR) for sAβ42 binding. The Aβ content in Albutein® was below the quantification threshold of the ELISA tests (<25 to <62.5 pg/ml) and ABtest® (<3.125 pg/ml). Quantification of exogenously added sAβ42 decreased in parallel with increasing protein concentration (59-78% at 45 mg/ml albumin). Recovery of sAβ serially diluted in Albutein® was ∼60% for sAβ40 and ∼70% for sAβ42, but was ∼100% in control samples without albumin. The KD by SPR analysis for sAβ42 interaction with Albutein® was 1.72 ± 0.24 × 10-6 M. In conclusion, Grifols' therapeutic albumin has undetectable content of Aβ40 and Aβ42. Moreover, Grifols' therapeutic albumin consistently binds peptidescontaining the primary sequence of human Aβ.
Amyloid-β Protein Precursor Regulates Phosphorylation and Cellular Compartmentalization of Microtubule Associated Protein Tau.
Source
Dipartimento di Oncologia, Biologia e Genetica, Università degli Studi di Genova, Genova, Italy.
Abstract
Tau is a multifunctional protein detected in different cellular compartments in neuronal and non-neuronal cells. When hyperphosphorylated and aggregated in atrophic neurons, tau is considered the culprit for neuronal death in familial and sporadic tauopathies. With regards to Alzheimer's disease (AD) pathogenesis, it is not yet established whether entangled tau represents a cause or a consequence of neurodegeneration. In fact, it is unquestionably accepted thatamyloid-β protein precursor (AβPP) plays a pivotal role in the genesis of the disease, and it is postulated that the formation of toxic amyloid-β peptides from AβPP is the primary event that subsequently induces abnormal tau phosphorylation. In this work, we show that in the brain of AD patients there is an imbalance between the nuclear and the cytoskeletal pools of phospho-tau. We observed that in non-AD subjects, there is a stable pool of phospho-tau which remains strictly confined to neuronal nuclei, while nuclear localization of phospho-tau is significantly underrepresented in neurons of AD patients bearing neurofibrillary tangles. A specific phosphorylation of tau is required during mitosis in vitro and in vivo, likely via a Grb2-ERK1/2 signaling cascade. In differentiated neuronal A1 cells, the overexpression of AβPP modulates tau phosphorylation, altering the ratio between cytoskeletal and nuclear pools, and correlates with cell death. Altogether our data provide evidence that AβPP, in addition to amyloid formation, modulates the phosphorylation of tau and its subcellular compartmentalization, an event that may lead to the formation of neurofibrillary tangles and to neurodegeneration when occurring in postmitotic neurons.
Monitoring blood flow alterations in the Tg2576 mouse model of Alzheimer's disease by in vivo magnetic resonance angiography at 17.6T.
Source
SSNMR, Leiden Institute of Chemistry, Gorlaeus Laboratoria, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
Abstract
Many neurodegenerative diseases including Alzheimer's disease are linked to abnormalities in the vascular system. In AD, the deposition of amyloid β (Aβ) peptide in the cerebral vessel walls, known as cerebral amyloid angiopathy (CAA) is frequently observed, leading to blood flow abnormalities. Visualization of the changes in vascular structure is important for early diagnosis and treatment. Blood vessels can be imaged non-invasively by magnetic resonance angiography (MRA). In this study we optimized high resolution MRA at 17.6T to longitudinally monitor morphological changes in cerebral arteries in a Tg2576 mouse model, a widely used model of AD. Our results at 17.6T show that MRA significantly benefits from the ultra-high magnetic field strength especially to visualize smaller vessels. Visual and quantitative analysis of MRA results revealed severe blood flow defects in large and medium sized arteries in Tg2576 mice. In particular blood flow defects were observed in the middle cerebral artery (MCA) and in the anterior communicating artery (AComA) in Tg2576 mice. Histological data show that Aβ levels in the vessel wall may be responsible for impaired cerebral blood flow, thereby contributing to the early progression of AD. To our knowledge this is the first ultra-high field MRA study monitoring blood flow alterations longitudinally in living Tg2576 mice, consequently providing a powerful tool to test new therapeutic intervention related to CAA in a mouse model of AD.
Copyright © 2011 Elsevier Inc. All rights reserved.
Measurement of beta amyloid peptides in specific cells using a photo thin-film transistor.
Abstract
ABSTRACT: The existence of beta-amyloid [Abeta] peptides in the brain has been regarded as the most archetypal biomarker of Alzheimer's disease [AD]. Recently, an early clinical diagnosis has been considered a great importance in identifying people who are at high risk of AD. However, no microscale electronic sensing devices for the detection of Abeta peptides have been developed yet. In this study, we propose an effective method to evaluate a small quantity of Abeta peptides labeled with fluorescein isothiocyanate [FITC] using a photosensitive field-effect transistor [p-FET] with an on-chip single-layer optical filter. To accurately evaluate the quantity of Abeta peptides within the cells cultured on the p-FET device, we measured the photocurrents which resulted from the FITC-conjugated Abeta peptides expressed from the cells and measured the number of photons of the fluorochrome in the cells using a photomultiplier tube. Thus, we evaluated the correlation between the generated photocurrents and the number of emitted photons. We also evaluated the correlation between the number of emitted photons and the amount of FITC by measuring the FITC volume using AFM. Finally, we estimated the quantity of Abeta peptides of the cells placed on the p-FET sensing area on the basis of the binding ratio between FITC molecules and Abeta peptides.
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