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Alzheimer's disease (AD) is the first cause of dementia that leads to insidious and progressive loss of memory and cognitive functions. In the early stages of AD, there is a strong correlation between memory impairment and cortical levels of soluble amyloid-β peptide oligomers (Aβ). It has become clear that Aβ disrupt glutamatergic synaptic function, which in turn may lead to the characteristic cognitive deficits. Conversely, experiments in rodents have conforted the notion that Aβo impairs synaptic transmission and plasticity, and that mouse models with increased production of these oligomers display cognitive impairment. Many studies have attempted to determine the mechanisms by which Aβo disrupt synaptic plasticity and mediate their detrimental effect, but the actual pathways are still poorly understood. Here we review this thriving area of research which aims at understanding the mechanisms of synaptic dysfunction in the early phase of AD, and its consequences on the activity of neural circuits. 相似文献
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Ylera F Lurz R Erdmann VA Fürste JP 《Biochemical and biophysical research communications》2002,290(5):1583-1588
Alzheimer's disease is correlated with the deposition of amyloid peptides in the brain of the patients. The amyloid is thus a major target in the search for novel diagnostic and therapeutic approaches. The present work employs in vitro selection to develop new tools for the study of the Alzheimer's disease. The selection strategy enables the design of specific nucleic acids (aptamers) against virtually any target molecule. High-affinity RNA aptamers against the betaA4(1-40) were isolated from a combinatorial library of approximately 10(15) different molecules. The apparent dissociation constants K(d) of these aptamers are 29-48 nM. The binding of the RNA to the amyloid fibrils was confirmed by electron microscopy. The chemical synthesis of these nucleic acids enables tailor-made modifications. By introduction of specific reporter groups these RNAs can become suitable tools for analytical and diagnostic purposes. Thus, this study may introduce a new approach for diagnosis of the Alzheimer's disease. 相似文献
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The PreA4(695) precursor protein of Alzheimer''s disease A4 amyloid is encoded by 16 exons. 总被引:7,自引:0,他引:7
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H G Lemaire J M Salbaum G Multhaup J Kang R M Bayney A Unterbeck K Beyreuther B Müller-Hill 《Nucleic acids research》1989,17(2):517-522
Alzheimer's disease (AD) is characterized by the cerebral deposition of fibrillar aggregates of the amyloid A4 protein. Complementary DNA's coding for the precursor of the amyloid A4 protein have been described. In order to identify the structure of the precursor gene relevant clones from several human genomic libraries were isolated. Sequence analysis of the various clones revealed 16 exons to encode the 695 residue precursor protein (PreA4(695] of Alzheimer's disease amyloid A4 protein. The DNA sequence coding for the amyloid A4 protein is interrupted by an intron. This finding supports the idea that amyloid A4 protein arises by incomplete proteolysis of a larger precursor, and not by aberrant splicing. 相似文献
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Human aminopeptidase N is encoded by 20 exons 总被引:1,自引:0,他引:1
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Soybean trypsin inhibitor, a protein of Mr = 20,000, has been used to assess the degree of inaccessibility of porcine trypsin within the alpha 2-macroglobulin-trypsin complex. The interaction between alpha 2-macroglobulin-bound trypsin and the inhibitor was demonstrated by affinity chromatography and trypsin inhibition. Whereas the free trypsin-inhibitor association is very fast (k = 1.2 X 10(7) M-1 s-1), the reaction between complexed trypsin and inhibitor takes 10 h to reach equilibrium. In addition, alpha 2-macroglobulin reduces, by several orders of magnitude, the affinity of trypsin for the inhibitor. Only one of the two trypsin molecules of the ternary (trypsin)2-alpha 2-macroglobulin complex is readily accessible to soybean inhibitor. It is postulated that the recently discovered proximity of the alpha 2-macroglobulin binding sites (Pochon, F., Favaudon, V., Tourbez-Perrin, M., and Bieth, J. (1981) J. Biol. Chem. 256, 547-550) accounts for this behavior. In the light of these results it is concluded that the proteinase binding sites are localized on the alpha 2-macroglobulin surface and that the two subunits of this protein are either not identical or not symmetrically arranged. 相似文献
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The Kunitz soybean proteinase inhibitors (SBTI-A2) of 13 soybean pure-lines were examined for variation in antitryptic activity. Extraction of the inhibitor from individual seeds, electrophoresis on polyacrylamide gels, and excision of the inhibitor region from the gels were used to prepare inhibitor samples for assay. Protein content of eluate from the gel portions was determined by absorbance at 280 nm after applying corrections for background absorbance due to gel chemicals. Enzyme inhibition and protein content of the gel eluate were used to calculate the specific activity of the inhibitor obtained from each seed. The coefficient of variation for specific activity measurement was about 12%, and analysis of variance on data from 13 pure-lines showed significant variation in inhibitor activity from genetic and environmental sources. There appeared to be three levels of inhibition averaging 21.9, 29.2, and 39.5 specific activity units.This investigation was supported in part by funds from the Illinois Agricultural Experiment Station, National Soybean Processor's Association, and a grant (FR 07030) from the U.S. Public Health Service. 相似文献
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The primary structure of a 61-amino-acid residue peptide from the pancreas of the European eel (Anguilla anguilla) has been established as E E K S G(5)L Y R K P(10)S C G E M(15)S A M H A(20)C P M N F(25)A P V C G(30)T D G N T(35)Y P N E C(40)S L C F Q(45)R Q N T K(50)T D I L I(55)T K D D R(60)C. There was no indication of microheterogeneity. This peptide shows structural similarity to pancreatic secretory trypsin inhibitors from several mammalian species and to a cholecystokinin-releasing peptide isolated from rat pancreatic juice. A comparison of the amino acid sequences of the peptides has identified a domain in the central region of the molecules that has been strongly conserved during evolution. In contrast, the amino acid sequence in the region corresponding to the reactive centre of the mammalian trypsin inhibitors is very poorly conserved in the eel peptide. The P1-P1' reactive site lysine-isoleucine (or arginine-isoleucine) bond in the mammalian trypsin inhibitors is replaced by a methionine-asparagine bond. This region does, however, show limited homology to the reactive centre of human alpha 1-protease inhibitor suggesting that the eel peptide may function as an inhibitor of other proteolytic enzymes in the pancreas. 相似文献
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There is a growing body of evidence to support a role for oxidative stress in Alzheimer's disease (AD), with increased levels of lipid peroxidation, DNA and protein oxidation products (HNE, 8-HO-guanidine and protein carbonyls respectively) in AD brains. The brain is a highly oxidative organ consuming 20% of the body's oxygen despite accounting for only 2% of the total body weight. With normal ageing the brain accumulates metals ions such iron (Fe), zinc (Zn) and copper (Cu). Consequently the brain is abundant in antioxidants to control and prevent the detrimental formation of reactive oxygen species (ROS) generated via Fenton chemistry involving redox active metal ion reduction and activation of molecular oxygen. In AD there is an over accumulation of the Amyloid beta peptide (Abeta), this is the result of either an elevated generation from amyloid precursor protein (APP) or inefficient clearance of Abeta from the brain. Abeta can efficiently generate reactive oxygen species in the presence of the transition metals copper and iron in vitro. Under oxidative conditions Abeta will form stable dityrosine cross-linked dimers which are generated from free radical attack on the tyrosine residue at position 10. There are elevated levels of urea and SDS resistant stable linked Abeta oligomers as well as dityrosine cross-linked peptides and proteins in AD brain. Since soluble Abeta levels correlate best with the degree of degeneration [C.A. McLean, R.A. Cherny, F.W. Fraser, S.J. Fuller, M.J. Smith, K. Beyreuther, A.I. Bush, C.L. Masters, Soluble pool of Abeta amyloid as a determinant of severity of neurodegeneration in Alzheimer's disease, Ann. Neurol. 46 (1999) 860-866] we suggest that the toxic Abeta species corresponds to a soluble dityrosine cross-linked oligomer. Current therapeutic strategies using metal chelators such as clioquinol and desferrioxamine have had some success in altering the progression of AD symptoms. Similarly, natural antioxidants curcumin and ginkgo extract have modest but positive effects in slowing AD development. Therefore, drugs that target the oxidative pathways in AD could have genuine therapeutic efficacy. 相似文献
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A technique for isolation of the trypsin inhibitor from soya beans (Kunitz inhibitor) was developed with affinity chromatography as a main step, the immobilized antibodies of the inhibitor being used as a sorbent. The inhibitor obtained was homogeneous according to the data of electrophoresis in PAAG and had the specific activity equal to that of an inhibitor preparation obtained by affinity chromatography on trypsin-sepharose. 相似文献
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Benseny-Cases N Cócera M Cladera J 《Biochemical and biophysical research communications》2007,361(4):916-921
Abeta(1-40) is one of the main components of the fibrils found in amyloid plaques, a hallmark of brains affected by Alzheimer's disease. It is known that prior to the formation of amyloid fibrils in which the peptide adopts a well-ordered intermolecular beta-sheet structure, peptide monomers associate forming low and high molecular weight oligomers. These oligomers have been previously described in electron microscopy, AFM, and exclusion chromatography studies. Their specific secondary structures however, have not yet been well established. A major problem when comparing aggregation and secondary structure determinations in concentration-dependent processes such as amyloid aggregation is the different concentration range required in each type of experiment. In the present study we used the dye Thioflavin T (ThT), Fourier-transform infrared spectroscopy, and electron microscopy in order to structurally characterize the different aggregated species which form during the Abeta(1-40) fibril formation process. A unique sample containing 90microM peptide was used. The results show that oligomeric species which form during the lag phase of the aggregation kinetics are a mixture of unordered, helical, and intermolecular non-fibrillar beta-structures. The number of oligomers and the amount of non-fibrillar beta-structures grows throughout the lag phase and during the elongation phase these non-fibrillar beta-structures are transformed into fibrillar (amyloid) beta-structures, formed by association of high molecular weight intermediates. 相似文献
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M Gross 《Current biology : CB》2012,22(10):R381-R384
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High molecular weight Alzheimer's disease amyloid peptide immunoreactivity in human serum and CSF is an immunoglobulin G 总被引:8,自引:0,他引:8
W M Pardridge H V Vinters B L Miller W W Tourtellotte J B Eisenberg J Yang 《Biochemical and biophysical research communications》1987,145(1):241-248
A radioimmunoassay (RIA) was developed to detect the 4200 Dalton amyloid (A4) peptide or it's precursor (A4P) in human serum or cerebrospinal fluid (CSF). A synthetic peptide containing the first 28 amino acids of the 43 amino acid A4 peptide was covalently coupled to bovine thyroglobulin and a polyclonal antiserum in rabbits was prepared. This antiserum was specific for vascular amyloid and neuritic plaques in Alzheimer's disease brain as detected by immunoperoxidase. The synthetic peptide, which has a tyrosine at residue 10, was iodinated with chloramine T and [125I]iodine and was purified to homogeneity by C4 reverse phase high performance liquid chromatography (HPLC). Extraction of human serum over a C18 Sep Pak cartridge indicated immunoreactive A4 peptide was not detectable in human serum. Conversely, high molecular weight A4 peptide immunoreactivity was detectable in human serum, at a concentration of 8.9 +/- 1.2 pmol-eq./ml, and in human CSF, at a concentration of 0.25 +/- 0.01 pmol-eq./ml, giving a CSF/serum ratio of 3.2%. The immunoreactivity in human serum was nearly completely removed by affinity deletion of serum immunoglobulin G (IgG), but not by affinity removal of IgA or IgM. Serum immunoreactivity was decreased 90% in hypogammaglobulinemia, and was increased 83% in human cord serum. There was no statistical difference in serum A4 immunoreactivity in Alzheimer's serum or CSF. Serum immunoreactivity in Down's syndrome was increased 50%. These studies indicate the high molecular weight A4P immunoreactivity in human serum or CSF is an IgG. Whether the A4 precursor in Alzheimer's disease is, in fact, an IgG, or whether there is an antibody in human serum and CSF that cross reacts with the A4 precursor cannot be determined until the serum immunoreactivity is purified and structurally characterized. 相似文献
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A I Bush R N Martins B Rumble R Moir S Fuller E Milward J Currie D Ames A Weidemann P Fischer 《The Journal of biological chemistry》1990,265(26):15977-15983
Western blots of normal human platelets, employing a monoclonal antibody raised against the full-length amyloid precursor protein of Alzheimer's disease (APP695), revealed major bands of 100-110 and 120-130 kDa in both cytosolic, membrane, and released fractions. These species were similar in size to forms seen in brain preparations and in plasma. There was no difference in Western blots of platelet preparations from Alzheimer patients compared with controls. Purified platelet amyloid precursor proteins were sequenced and shown to be amino terminally homogeneous. Immunohistochemistry localized the antigen to the platelet and megakaryocyte and demonstrated weak immunostaining of some lymphocytes. Immunoprecipitation of material released from platelets demonstrated that sedimentable full-length APP with the carboxyl-terminal epitope, and soluble APP lacking the carboxyl-terminal epitope, may exist in the circulation. Western blots and carboxyl-terminal and amino-terminal APP radioimmunoassay of material released by platelets in response to stimulation revealed that platelets release APP during degranulation. The function of platelet APP is yet to be determined, but the present studies suggest a role in regulation of the coagulation cascade or in platelet aggregation. 相似文献
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Protease-specificity of Kunitz inhibitor domain of Alzheimer's disease amyloid protein precursor 总被引:1,自引:0,他引:1
H Kido A Fukutomi J Schilling Y Wang B Cordell N Katunuma 《Biochemical and biophysical research communications》1990,167(2):716-721
The putative inhibitor domain of Alzheimer's disease amyloid protein precursor was purified from E. coli containing a synthetic gene encoding the Kunitz domain. The purified protein (A4 inhibitor) inhibited the activity of trypsin, forming a 1:1 molar complex with the enzyme. It also strongly inhibited plasmin (Ki = 7.5 x 10(-11) M) from human serum and tryptase (Ki = 2.2 x 10(-10) M) from rat mast cells (tryptase M). In addition, it inhibited rat pancreatic trypsin, alpha-chymotrypsin and kallikrein and human serum kallikrein, but did not inhibit rat chymase, pancreatic elastase, alpha-thrombin, urokinase, papain or cathepsin B. 相似文献