Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.69 (APC)
 16,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

At the cellular level, Alzheimer's disease (AD) must be the result of neuronal dysfunction and degeneration leading to a reduction in synaptic density. Filamentous deposits of amyloid, which define the disease at the molecular level, occur within perikarya, axons, dendrites, and terminals of neurons as neurofibrillary tangles (NFT), in the extracellular neuropil as amyloid plaques (APC), and around blood vessels as amyloid congophilic angiopathy (ACA). These fibrillar amyloid protein aggregates are also found in the brain of all individuals with Down's syndrome after the age of 30 years. The amyloid deposits apparently occur in the terminal zones of neurons that develop NFT. It is suggested that amyloid deposition is of fundamental significance in AD and that a thorough understanding of amyloid formation will eventually lead to successful therapeutic intervention in AD. As elucidation of the reasons behind amyloid deposition must shed some light on the pathogenesis of AD, we review the current state of knowledge on the nature of the AD amyloid protein, its origin, and its formation. Although there is yet no agreement about the chemical nature of the amyloid protein of NFT, the major constituent of both APC and ACA has been shown to be a 4.5-kD amyloid protein originally termed "beta-protein" or "amyloid A4" which we now denote as "beta A4." Amyloid beta A4 protein is proteolytically derived from a transmembrane protein termed amyloid precursor protein (APP) which is encoded by a widely expressed gene on chromosome 21. Our present results are consistent with the possibility that amyloid formation requires membrane damage or APP molecules that are not or are incorrectly integrated into membranes. To allow the generation of the C-terminus of beta A4, one proteolytic cleavage step has to occur in the sequence that normally forms the transmembrane domain of the APP proteins. This cleavage is crucial for amyloid formation because we could show that the ability of synthetic beta A4 to form amyloid depositions is mainly based on hydrophobic parts of the sequence that have to interact with each other and build up large aggregates under physiologic conditions. Membrane association of APP is expected to interfere with this cleavage and the process of aggregation.
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PMID:Mechanisms of amyloid deposition in Alzheimer's disease. 177 29

Amyloid formation in the brain is diagnostic of Alzheimer's disease (AD). However, it is not known whether amyloidogenesis precedes and possibly causes cell death or is a byproduct of cell lysis. In any event, it is critical to understand the time course of amyloid formation. The mechanism of amyloidogenesis has been studied in a simple in vitro model system which can be modified to dissect the factors which may be important in vivo. The studies described herein deal with two factors which are known to be important in vivo; the length of the beta protein C-terminus and the endogenous molecule apolipoprotein E (apoE). It could be shown that the C-terminal sequence of the beta-amyloid protein is a critical determinant of the rate of amyloid formation. This discovery led us to propose that the production of the C-terminally extended variants may be a pathogenic event in familial AD. The APOE allele has been shown to be a susceptibility factor for non-familial AD. The apoE variants have been shown to be amyloid nucleation inhibitors. These proteins probably serve as endogenous amyloid suppressors.
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PMID:Consequences of the molecular mechanism of amyloid formation for the understanding of the pathogenesis of Alzheimer's disease and the development of therapeutic strategies. 776 39

Potent active-site inhibitors of human tissue factor-Factor VIIa (TF.FVIIa) have been selected from Alzheimer's amyloid beta-protein precursor inhibitor (APPI) Kunitz domain libraries displayed on phage. Eight randomized positions on the extended primary binding loop (P5 through P4') and positions 34 and 39 were examined in three separate libraries. Libraries contained from 3.2 x 10(5) to 3.2 x 10(6) potential variants resulting from replacing up to 5 positions with all 20 amino acids. Following 4 rounds of selection against FVIIa associated with immobilized tissue factor (TF), 12 clones from each library were sequenced. Variants were purified by trypsin affinity chromatography and reverse-phase high performance liquid chromatography, and characterized for their ability to inhibit TF.FVIIa chromogenic activity. Measured apparent equilibrium dissociation constants (Ki*) ranged from about 10 to 500 nM. From sequence and activity data, an overall consensus sequence, TF7I-C, was constructed by site-directed mutagenesis. TF7I-C differed from APPI at 4 key residues, T11P, M17L, S19L, and G39Y, and inhibited TF.FVIIa with a Ki* = 1.9 +/- 0.4 nM, which represented an increase in binding affinity of more than 150-fold compared to APPI. At 40 microM, TF7I-C prolonged the clotting times 3.5-fold in a prothrombin time assay and > 10-fold at 7 microM in an activated partial thromboplastin time assay. Prolongation of the activated partial thromboplastin time correlates with potent inhibition of FXIa (Ki* = 0.8 nM) and plasma kallikrein (Ki* = 1.2 nM). TF7I-C also inhibited plasmin (Ki* = 40 nM) and FXa (Ki* = 55 nM), but not activated protein C, thrombin, or FXIIa (Ki* > 10 microM each).
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PMID:Kunitz domain inhibitors of tissue factor-factor VIIa. I. Potent inhibitors selected from libraries by phage display. 807 37

Alzheimer's disease-related presenilins are thought to be involved in Notch signaling during embryonic development and/or cellular differentiation. Proteins mediating the cellular functions of the presenilins are still unknown. We utilized the yeast two-hybrid system to identify an interacting armadillo protein, termed p0071, that binds specifically to the hydrophilic loop of presenilin 1. In vivo, the presenilins constitutively undergo proteolytic processing, forming two stable fragments. Here, we show that the C-terminal fragment of presenilin 1 directly binds to p0071. Nine out of 10 armadillo repeats in p0071 are essential for mediating this interaction. Since armadillo proteins, like beta-catenin and APC, are known to participate in cellular signaling, p0071 may function as a mediator of presenilin 1 in signaling events.
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PMID:Direct interaction of Alzheimer's disease-related presenilin 1 with armadillo protein p0071. 1009 85

We performed a cross-sectional case-control study among 295 subjects with dementia and 406 control subjects drawn from participants of the Rotterdam Study, a population-based cohort study among subjects aged 55 years or over, and from participants of the Rotterdam Stroke Databank, a hospital-based stroke registry, to evaluate the association of the factor V Leiden mutation and activated protein C (APC) response with dementia and its subtypes. The risk of dementia was 2.11-fold increased among carriers of factor V Leiden mutation relative to subjects lacking factor V Leiden mutation (95% confidence interval, CI, 0.93-4.77). The increased risks of vascular dementia and of Alzheimer's disease were 4.28 (95% CI 1.26-14.5) and 2.15 (95% CI 0.82-5.63), respectively. No association was found for APC response. We showed a nonsignificant twofold increased risk of dementia among subjects with factor V Leiden. The association appeared to be stronger for vascular dementia.
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PMID:Response to activated protein C in subjects with and without dementia. The Dutch Vascular Factors in Dementia Study. 1042 68

Glycogen synthase kinase 3 (GSK-3), an element of the Wnt signalling pathway, plays a key role in numerous cellular processes including cell proliferation, embryonic development, and neuronal functions. It is directly involved in diseases such as cancer (by controlling apoptosis and the levels of beta-catenin and cyclin D1), Alzheimer's disease (tau hyperphosphorylation), and diabetes (as a downstream element of insulin action, GSK-3 regulates glycogen and lipid synthesis). We describe here a rapid and efficient method for the purification of GSK-3 by affinity chromatography on an immobilized fragment of axin. Axin is a docking protein which interacts with GSK-3ss, beta-catenin, phosphatase 2A, and APC. A polyhistidine-tagged axin peptide (residues 419-672) was produced in Escherichia coli and either immobilized on Ni-NTA agarose beads or purified and immobilized on CNBr-activated Sepharose 4B. These "Axin-His6" matrices were found to selectively bind recombinant rat GSK-3 beta and native GSK-3 from yeast, sea urchin embryos, and porcine brain. The affinity-purified enzymes displayed high kinase activity. This single step purification method provides a convenient tool to follow the status of GSK-3 (protein level, phosphorylation state, kinase activity) under various physiological settings. It also provides a simple and efficient way to purify large amounts of active recombinant or native GSK-3 for screening purposes.
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PMID:Purification of GSK-3 by affinity chromatography on immobilized axin. 1108 79

Pulmonary surfactant is essential for respiration and lung host defence and is composed of 80-90% lipids, mainly dipalmitoylphosphatidylcholine (DPPC). Surfactant protein C (SP-C) constitutes 1-2% of the surfactant mass, and is one of the most hydrophobic peptides yet isolated. SP-C residues 9-34 form an alpha-helix with a central poly-valine segment, which perfectly matches the thickness of a fluid DPPC bilayer. The palmitoyl groups linked to Cys-5 and Cys-6 of SP-C increase the capacity of the peptide to promote lipid adsorption at an air/liquid interface, and augment the mechanical stability of SP-C/lipid mixtures. SP-C undergoes alpha-helix-->beta-sheet transition and forms amyloid fibrils. NMR and MS studies show that the poly-valine helix is kinetically stabilized, and that once it unfolds, formation of beta-sheet aggregates is significantly faster than refolding. alpha-Helix unfolding is accelerated after removal of the palmitoyl groups. Secondary structure prediction of SP-C yields beta-strand conformation of the poly-valine part. A database search revealed similar discordance between experimentally determined helices and predicted beta-strands for other amyloid-forming proteins, including the prion protein associated with spongiform encephalopathies, and the amyloid-beta (Abeta) peptide associated with Alzheimer's disease. For Abeta and SP-C, removal of the helix/strand discordance by residue replacements abrogates fibril formation in vitro.
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PMID:Membrane properties and amyloid fibril formation of lung surfactant protein C. 1149 36

Amyloid fibrils are polymers composed of proteins in beta-sheet conformation, which are found in at least 20 diseases for which no cure is available. These diseases include Alzheimer's disease and spongiform encephalopathies, in which the amyloid beta-peptide and the prion protein (PrP), respectively, form amyloid. All fibrils are morphologically very similar although the native structures of the corresponding proteins are widely different. Proteins that are not known to form fibrils in vivo can do so under conditions where unfolding intermediates are well populated. This indicates that fibril formation can arise from most, if not all, polypeptide chains under certain conditions, and that nature has found ways to avoid fibrillogenic protein conformations. In support of this, it was recently found that unpaired beta-strands present in native proteins are prevented from forming intermolecular beta-sheets, by strategic placement of prolines and charged residues for example. Structural studies of the lung surfactant-associated protein C (SP-C) have revealed determinants for amyloid fibril formation. The poly-valine alpha-helix of SP-C spontaneously converts to beta-sheet aggregates in vitro and SP-C amyloid fibrils are found in pulmonary alveolar proteinosis. A beta, PrP, and SP-C harbour an alpha-helix which is strongly predicted to form a beta-strand, and in all cases investigated so far such alpha-helix/beta-sheet discordance correlates with the ability to form beta-sheet aggregates and fibrils.
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PMID:Molecular determinants for amyloid fibril formation: lessons from lung surfactant protein C. 1284 70

The anaphase-promoting complex/cyclosome (APC/C) is a key E3 ubiquitin ligase complex that functions in regulating cell cycle transitions in proliferating cells and has, as revealed recently, novel roles in postmitotic neurons. Regulated by its activator Cdh1 (or Hct1), whose level is high in postmitotic neurons, APC/C seems to have multiple functions at different cellular locations, modulating diverse processes such as synaptic development and axonal growth. These processes do not, however, appear to be directly connected to cell cycle regulation. It is now shown that Cdh1-APC/C activity may also have a basic role in suppressing cyclin B levels, thus preventing terminally differentiated neurons from aberrantly re-entering the cell cycle. The result of an aberrant cyclin B-induced S-phase entry, at least for some of these neurons, would be death via apoptosis. Cdh1 thus play an active role in maintaining the terminally differentiated, non-cycling state of postmitotic neurons--a function that could become impaired in Alzheimer's and other neurodegenerative diseases.
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PMID:Cdh1-APC/C, cyclin B-Cdc2, and Alzheimer's disease pathology. 1625 8

Non-steroidal antirheumatics (NSA) belong to the most often prescribed drugs. Certain observation studies indicate that they are used by 20 to 30% of population of developed countries. The most common NSA's adverse effects are gastrointestinal complications. Coxibs have been developed as an alternative to conventional non-selective NSA; with similar efficacy, they should reduce the risk of development of gastrointestinal complications. In the few last years, possible toxicity of coxibs and other non-steroidal antirheumatics has been widely discussed. The VIGOR study, which was performed 6 years ago, showed five times higher incidence of nonfatal myocardial infarction in patients with rofecoxib therapy as compared with naproxen. Afterwards, there was much debate about rofecoxib, and coxibs in general, whose cardiotoxicity was supported and confuted at the same time. Possible cardioprotective effect of naproxen was discussed too. Later on, results of the APPROVE study (Adenoma Polyp Prevention on Vioxx) made Merck & Co., Inc. withdraw rofecoxib from all markets voluntarily. In the end of 2004, three controversial studies on celecoxib were published. Although the first study (Adenoma Prevention with Celecoxib study, APC) showed higher cardiovascular risk of celecoxib, the second study (Prevention of Adenomatosus Polyps, PreSAP) did not verify these results. Surprisingly, the third study (Alzheimer Disease and Prevention Trial, ADAPT) proved 50% increase of the risk of cardiovascular (CV) toxicity of naproxen. In the last year, researchers have tried to decide whether CV toxicity is a class effect of coxib group or a class effect of all NSA. Many observation studies proved higher CV risk both of coxibs (particularly rofecoxib) and non-selective NSA including naproxen. These new findings moved the American FDA (Food and Drug Administration) to publish guidance concerning higher CV risk of all coxibs and NSA. For the time being, the EMEA (European Agency for Evaluation of Medicinal Products) does not change its attitude to NSA; coxibs are contraindicated in patients with ischemic heart disease, cerebrovascular disease and peripheral artery disease; they should be used with caution in high-risk patients. Final assessment of the problems of CV toxicity of NSA and coxibs will be a case of a long-term randomized study focused on the incidence of cardiovascular adverse effects.
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PMID:[Problems of cardiovascular toxicity of coxibs and non-selective NSA]. 1696 8


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