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1.
Proc Natl Acad Sci U S A ; 98(25): 14675-80, 2001 Dec 04.
Article in English | MEDLINE | ID: mdl-11724968

ABSTRACT

Memory impairment progressing to dementia is the main clinical symptom of Alzheimer's disease (AD). AD is characterized histologically by the presence of beta-amyloid (Abeta) plaques and neurofibrillary tangles in specific brain regions. Although Abeta derived from the Abeta precursor protein (beta-APP) is believed to play a central etiological role in AD, it is not clear whether soluble and/or fibrillar forms are responsible for the memory deficit. We have generated and previously described mice expressing human wild-type beta-APP(751) isoform in neurons. These transgenic mice recapitulate early histopathological features of AD and form Abeta deposits but no plaques. Here we describe a specific and progressive learning and memory impairment in these animals. In the Morris water maze, a spatial memory task sensitive to hippocampal damage, one pedigree already showed significant differences in acquisition in 3-month-old mice that increased in severity with age and were expressed clearly in 6-month- and 2-year-old animals. The second transgenic pedigree displayed a milder impairment with a later age of onset. Performance deficits significantly decreased during the 6 days of training in young but not in aged transgenic animals. Both pedigrees of the transgenic mice differed from wild-type mice by less expressed increase of escape latencies after the platform position had been changed in the reversal experiment and by failure to prefer the goal quadrant in probe trials. Both pedigrees performed at wild-type level in a number of other tests (open field exploration and passive and active place avoidance). The results suggest that plaque formation is not a necessary condition for the neuronal beta-APP(751) transgene-induced memory impairment, which may be caused by beta-APP overexpression, isoform misexpression, or elevated soluble Abeta.


Subject(s)
Aging/genetics , Aging/physiology , Amyloid beta-Protein Precursor/genetics , Amyloid beta-Protein Precursor/physiology , Learning/physiology , Alzheimer Disease/etiology , Alzheimer Disease/pathology , Alzheimer Disease/psychology , Animals , Disease Models, Animal , Exploratory Behavior/physiology , Humans , Male , Maze Learning/physiology , Mice , Mice, Transgenic , Plaque, Amyloid/pathology , Spatial Behavior/physiology
2.
Mol Biotechnol ; 18(1): 1-10, 2001 May.
Article in English | MEDLINE | ID: mdl-11439695

ABSTRACT

Proteases play a critical role in many cellular functions and have been an attractive therapeutic target due to their involvement in a number of disease processes. One prominent example is the secretases responsible for the generation of amyloid beta peptide, which is believed to be central for the development of Alzheimer's disease. It is therefore desirable to identify and characterize these proteases. We have developed a novel functional approach for identification of proteases and modulators by coupling the protease activity to caspase-mediated apoptosis. Here we show the proof of principle for this approach using beta-secretase as an example. We provide data showing that 1. A modified caspase-3 containing beta-secretase cleavage site induces apoptosis in 293T cells. 2. The modified caspase-3 induced apoptosis is correlated with the susceptibility of beta-secretase recognition sequence to beta-secretase. 3. In vivo beta-secretase competitors BACE2 and BACE2(D110A) prevent the modified caspase-3 induced cell death. Therefore, this approach can be a useful tool in studies of proteolytic cleavage provided only that the protease recognition sequence is known.


Subject(s)
Amyloid beta-Peptides/chemistry , Aspartic Acid Endopeptidases , Biochemistry/methods , Endopeptidases/analysis , Endopeptidases/chemistry , Glycoproteins/chemistry , Membrane Proteins/chemistry , Alzheimer Disease/diagnosis , Amyloid Precursor Protein Secretases , Apoptosis , Binding, Competitive , Blotting, Western , Caspase 3 , Caspases/metabolism , Cell Line , Cloning, Molecular , Glycoproteins/metabolism , Humans , Membrane Proteins/metabolism , Mutagenesis, Site-Directed , Protein Binding , Time Factors , Transfection
3.
J Biol Chem ; 276(33): 30701-7, 2001 Aug 17.
Article in English | MEDLINE | ID: mdl-11402035

ABSTRACT

The majority of familial Alzheimer's disease cases have been attributed to mutations in the presenilin 1 (PS1) gene. PS1 is synthesized as an inactive holoprotein that undergoes endoproteolytic processing to generate a functional N- and C-terminal heterodimer (NTF and CTF, respectively). We identified a single residue in PS1, Ser(397), which regulates the CTF levels in a population of dimer that has a rapid turnover. This residue is part of a highly conserved glycogen synthase kinase-3beta (GSK-3beta) consensus phosphorylation site within the loop domain of PS1. Site-directed mutagenesis at the Ser(397) position increased levels of PS1 CTF but not NTF or holoprotein. Similar increases in only CTF levels were seen when cells expressing wild type PS1 were treated with lithium chloride, an inhibitor of GSK-3beta. Both wild type and PS1 S397A CTF displayed a biphasic turnover, reflecting rapidly degraded and stable populations. Rapid turnover was delayed for mutant PS1 S397A, causing increased CTF. These data demonstrate that PS1 NTF.CTF endoproteolytic fragments are generated in excess, that phosphorylation at Ser(397) by GSK-3beta regulates the discard of excess CTF, and that the disposal of surplus NTF is mediated by an independent mechanism. Overall, the results indicate that production of active NTF.CTF dimer is more complex than limited endoproteolysis of PS1 holoprotein and instead involves additional regulatory events.


Subject(s)
Calcium-Calmodulin-Dependent Protein Kinases/physiology , Membrane Proteins/analysis , Peptide Fragments/analysis , Amino Acid Motifs , Amino Acid Sequence , Cells, Cultured , Dimerization , Glycogen Synthase Kinase 3 , Glycogen Synthase Kinases , Humans , Membrane Proteins/chemistry , Molecular Sequence Data , Phosphorylation , Presenilin-1
4.
Neuroreport ; 12(6): 1265-70, 2001 May 08.
Article in English | MEDLINE | ID: mdl-11338204

ABSTRACT

A beta deposition in the APPV717F transgenic model of Alzheimer's pathology involves apolipoprotein E (apoE). We measured soluble and insoluble apoE in brain region extracts at an early and late stage of plaque development. The apoE levels in the insoluble fraction were greatly elevated in the hippocampus and cortex of aged transgenic animals but were unchanged in wild type or young APPV717F animals. Soluble apoE levels were unaltered. A beta levels were also measured and a positive correlation between apoE and A beta in the insoluble fraction was observed. ApoE transcription was increased approximately 3-fold in the hippocampus of 17-month-old APPV717F mice, suggesting a region-specific upregulation of apoE transcription in the brains of APPV717F mice to compensate for apoE sequestered with fibrillar A beta.


Subject(s)
Alzheimer Disease/metabolism , Amyloid beta-Protein Precursor/metabolism , Apolipoproteins E/metabolism , Brain/metabolism , Disease Models, Animal , Alleles , Amyloid beta-Peptides/metabolism , Animals , Enzyme-Linked Immunosorbent Assay , Mice , Mice, Inbred C57BL , Mice, Knockout , Mice, Transgenic , Solubility
5.
J Biol Chem ; 276(10): 7366-75, 2001 Mar 09.
Article in English | MEDLINE | ID: mdl-11104755

ABSTRACT

The majority of cases with early onset familial Alzheimer's disease have been attributed to mutations in the presenilin 1 (PS1) gene. PS1 protein is a component of a high molecular weight membrane-bound complex that also contains beta-catenin. The physiological relevance of the association between PS1 and beta-catenin remains controversial. In this study, we report the identification and functional characterization of a highly conserved glycogen synthase kinase-3beta consensus phosphorylation site within the hydrophilic loop domain of PS1. Site-directed mutagenesis, together with in vitro and in vivo phosphorylation assays, indicates that PS1 residues Ser(353) and Ser(357) are glycogen synthase kinase-3beta targets. Substitution of one or both of these residues greatly reduces the ability of PS1 to associate with beta-catenin. By disrupting this interaction, we demonstrate that the association between PS1 and beta-catenin has no effect on Abeta peptide production, beta-catenin stability, or cellular susceptibility to apoptosis. Significantly, in the absence of PS1/beta-catenin association, we found no alteration in beta-catenin signaling using induction of this pathway by exogenous expression of Wnt-1 or beta-catenin and a Tcf/Lef transcriptional assay. These results argue against a pathologically relevant role for the association between PS1 and beta-catenin in familial Alzheimer's disease.


Subject(s)
Calcium-Calmodulin-Dependent Protein Kinases/chemistry , Cytoskeletal Proteins/chemistry , Membrane Proteins/chemistry , Signal Transduction , Trans-Activators , Alzheimer Disease/metabolism , Amino Acid Motifs , Amino Acid Sequence , Amyloid beta-Peptides/chemistry , Apoptosis , Binding Sites , Blotting, Western , Cell Death , Cell Line , Cell Nucleus/metabolism , Cytoskeletal Proteins/metabolism , Cytoskeletal Proteins/physiology , Cytosol/metabolism , DNA, Complementary/metabolism , Genetic Vectors , Glycogen Synthase Kinase 3 , Glycogen Synthase Kinases , Humans , Luciferases/metabolism , Membrane Proteins/genetics , Membrane Proteins/physiology , Microscopy, Fluorescence , Models, Molecular , Molecular Sequence Data , Mutagenesis, Site-Directed , Mutation , Peptide Fragments/chemistry , Phosphorylation , Precipitin Tests , Presenilin-1 , Protein Binding , Protein Structure, Tertiary , Sequence Homology, Amino Acid , Serine/chemistry , Transfection , beta Catenin
6.
Neurobiol Aging ; 22(6): 895-902, 2001.
Article in English | MEDLINE | ID: mdl-11754996

ABSTRACT

Transgenic APPV717F mice, homozygous for a human minigene encoding the V717F familial Alzheimer's disease mutation, develop Abeta plaques similar to those seen in Alzheimer patients and show evidence of neuronal cell drop out in CA2-3 regions of the hippocampus at 8 months of age and older. Interleukin-1 (IL-1)beta (IL-1beta) converting enzyme (ICE) is a cysteine protease (caspase-1) that processes inactive (33 kDa) pro-IL-1beta to the active (17 kDa) inflammatory cytokine. We used immunohistochemistry, RT-PCR, and DNA cleavage (TUNEL) analysis to show progressive, age-associated increases in ICE mRNA levels, in the numbers of ICE-immunoreactive glia, and in the numbers of neurons showing evidence of DNA damage in APPV717F mice that commenced months prior to the appearance of Abeta plaques. Moreover, there were significant correlations between these parameters over an age range of 1-17 months. These findings are consistent with the idea that increases in ICE activity and expression contribute to neuronal injury in Alzheimer's disease.


Subject(s)
Alzheimer Disease/genetics , Caspase 1/biosynthesis , Caspase 1/genetics , DNA Damage/physiology , Gene Expression Regulation, Enzymologic/genetics , Neurons/metabolism , Animals , Female , Humans , Immunohistochemistry , In Situ Nick-End Labeling , Mice , Mice, Transgenic , RNA, Messenger/biosynthesis , RNA, Messenger/genetics , Reverse Transcriptase Polymerase Chain Reaction , Silver Staining
7.
Brain ; 123 Pt 12: 2467-74, 2000 Dec.
Article in English | MEDLINE | ID: mdl-11099448

ABSTRACT

Most cases of familial presenile Alzheimer's disease are caused by mutations in the presenilin-1 (PSEN-1) gene, most of these mutations being missense mutations. A mutation in the splice donor site of intron 4 of PSEN-1 has been described recently which results in aberrant splicing of PSEN-1 mRNA, causing insertion of an additional amino acid, Thr113-114ins, into the protein. We studied the neuropathology of four cases bearing this mutation in an attempt to clarify the pathology of this hereditary form of Alzheimer's disease and to determine whether it differs from other familial forms of the disease. The disease presented as a progressive cognitive decline, myoclonus and seizures developing later in the disease, a feature common to PSEN-1-linked Alzheimer's disease. The course of the disease was relatively rapid, death occurring approximately 6 years after onset. Pathology in the intron 4 cases demonstrated a severe Alzheimer's disease pathology with abundant deposition of ss-amyloid (Ass) 1-42 senile plaques and the formation of neurofibrillary tangles. Amyloid angiopathy was present in these cases and was readily demonstrated by Ass 1-40 staining, particularly in the cerebellum. Cases with the intron 4 mutation appear clinically and pathologically similar to other cases of early-onset Alzheimer's disease bearing PSEN-1 mutations.


Subject(s)
Alzheimer Disease/genetics , Alzheimer Disease/pathology , Membrane Proteins/genetics , Mutation/genetics , Adult , Alzheimer Disease/complications , Cognition Disorders/etiology , Creutzfeldt-Jakob Syndrome/diagnosis , DNA Mutational Analysis , Diagnosis, Differential , Disease Progression , Electroencephalography , England , Fatal Outcome , Female , Humans , Introns/genetics , Myoclonus/etiology , Pedigree , Presenilin-1 , Seizures/etiology
8.
Am J Pathol ; 157(3): 895-904, 2000 Sep.
Article in English | MEDLINE | ID: mdl-10980129

ABSTRACT

Inflammation is an important neuropathological change in Alzheimer's disease (AD). However, the pathophysiological factors that initiate and maintain the inflammatory response in AD are unknown. We examined AbetaPP(V717F) transgenic mice, which show numerous brain amyloid-beta (Abeta) deposits, for expression of the macrophage colony-stimulating factor (M-CSF) and its receptor (M-CSFR). M-CSF is increased in the brain in AD and dramatically augments the effects of Abeta on cultured microglia. AbetaPP(V717F) animals 12 months of age showed large numbers of microglia strongly labeled with an M-CSFR antibody near Abeta deposits. M-CSFR mRNA and protein levels were also increased in brain homogenates from AbetaPP(V717F) animals. Dystrophic neurites and astroglia showed no M-CSFR labeling in the transgenic animals. A M-CSF antibody decorated neuritic structures near hippocampal Abeta deposits in transgenic animals. M-CSF mRNA was also increased in AbetaPP(V717F) animals in comparison with wild-type controls. Simultaneous overexpression of M-CSFR and its ligand in AbetaPP(V717F) animals could result in augmentation of Abeta-induced activation of microglia. Because chronic activation of microglia is thought to result in neuronal injury, the M-CSF system may be a potential target for therapeutic intervention in AD.


Subject(s)
Alzheimer Disease/metabolism , Amyloid beta-Protein Precursor/physiology , Receptor, Macrophage Colony-Stimulating Factor/biosynthesis , Alzheimer Disease/genetics , Amyloid Neuropathies/metabolism , Amyloid Neuropathies/pathology , Amyloid beta-Peptides/metabolism , Amyloid beta-Protein Precursor/genetics , Animals , Blotting, Western , Cerebellum/metabolism , Cerebral Cortex/metabolism , Fluorescent Antibody Technique, Indirect , Hippocampus/metabolism , Macrophage Colony-Stimulating Factor/biosynthesis , Macrophage Colony-Stimulating Factor/genetics , Mice , Mice, Transgenic , Microglia/metabolism , Microglia/pathology , Microscopy, Confocal , Plaque, Amyloid/metabolism , Plaque, Amyloid/pathology , RNA, Messenger/metabolism , Receptor, Macrophage Colony-Stimulating Factor/genetics , Reverse Transcriptase Polymerase Chain Reaction
9.
J Biol Chem ; 275(44): 34086-91, 2000 Nov 03.
Article in English | MEDLINE | ID: mdl-10915801

ABSTRACT

Presenilins are integral membrane protein involved in the production of amyloid beta-protein. Mutations of the presenilin-1 and -2 gene are associated with familial Alzheimer's disease and are thought to alter gamma-secretase cleavage of the beta-amyloid precursor protein, leading to increased production of longer and more amyloidogenic forms of A beta, the 4-kDa beta-peptide. Here, we show that radiolabeled gamma-secretase inhibitors bind to mammalian cell membranes, and a benzophenone analog specifically photocross-links three major membrane polypeptides. A positive correlation is observed among these compounds for inhibition of cellular A beta formation, inhibition of membrane binding and cross-linking. Immunological techniques establish N- and C-terminal fragments of presenilin-1 as specifically cross-linked polypeptides. Furthermore, binding of gamma-secretase inhibitors to embryonic membranes derived from presenilin-1 knockout embryos is reduced in a gene dose-dependent manner. In addition, C-terminal fragments of presenilin-2 are specifically cross-linked. Taken together, these results indicate that potent and selective gamma-secretase inhibitors block A beta formation by binding to presenilin-1 and -2.


Subject(s)
Endopeptidases/drug effects , Enzyme Inhibitors/metabolism , Membrane Proteins/metabolism , Amyloid Precursor Protein Secretases , Cell Membrane/metabolism , Endopeptidases/metabolism , Precipitin Tests , Presenilin-1 , Presenilin-2 , Substrate Specificity
10.
J Biol Chem ; 275(41): 31770-7, 2000 Oct 13.
Article in English | MEDLINE | ID: mdl-10918055

ABSTRACT

Amyloid Abeta deposition is a neuropathologic hallmark of Alzheimer's disease. Activated microglia are intimately associated with plaques and appear to facilitate Abeta deposition, an event believed to contribute to pathogenesis. It is unclear if microglia can modulate pathogenesis of Alzheimer's disease by secreting lipoprotein particles. Here we show that cultured BV2 murine microglial cells, like astrocytes, secrete apolipoprotein E (apoE) and apolipoprotein J (apoJ) in a time-dependent manner. To isolate and identify BV2 microglial particles, gel filtration chromatography was employed to fractionate BV2-conditioned medium. Analyses by Western blot, lipid determination, electron microscopy, and native gel electrophoresis demonstrate that BV2 microglial cells release spherical low density lipoprotein (LDL)-like lipid-containing particles rich in apoJ but poor in apoE. These microglial particles are dissimilar in size, shape, and lipoprotein composition to astrocyte-derived particles. The microglial-derived particles were tested for functional activity. Under conditions of suppressed de novo cholesterol synthesis, the LDL-like particles effectively rescued primary rat cortical neurons from mevastatin-induced neurotoxicity. The particles were also shown to bind Abeta. We speculate that the LDL-like apoJ-rich apoE-poor microglial lipoproteins preferentially bind the lipoprotein receptor, recognizing apoJ, which is abundant in the choroid plexus, facilitating Abeta clearance from the brain. BV2 cells also secrete an apoE-rich lipid-poor species that binds Abeta. Consistent with the role of apoE in Abeta fibril formation and deposition, this microglial species may promote plaque formation.


Subject(s)
Apolipoproteins E/isolation & purification , Glycoproteins/isolation & purification , Lipoproteins, LDL/chemistry , Liposomes/chemistry , Microglia/chemistry , Molecular Chaperones , Nerve Tissue Proteins/isolation & purification , Alzheimer Disease/metabolism , Amyloid beta-Peptides/metabolism , Animals , Apolipoproteins E/chemistry , Apolipoproteins E/immunology , Apolipoproteins E/ultrastructure , Blotting, Western , Cell Death/drug effects , Cells, Cultured , Chromatography, Gel , Clusterin , Culture Media, Conditioned/chemistry , Electrophoresis, Polyacrylamide Gel , Glycoproteins/chemistry , Glycoproteins/immunology , Glycoproteins/ultrastructure , Kinetics , Lipoproteins, LDL/metabolism , Lipoproteins, LDL/ultrastructure , Liposomes/metabolism , Lovastatin/analogs & derivatives , Lovastatin/pharmacology , Mice , Microglia/cytology , Microglia/metabolism , Microscopy, Electron , Nerve Tissue Proteins/chemistry , Nerve Tissue Proteins/immunology , Nerve Tissue Proteins/ultrastructure , Neurons/cytology , Neurons/drug effects , Particle Size , Plaque, Amyloid/chemistry , Plaque, Amyloid/metabolism , Protein Binding , Rats
12.
Neurology ; 54(2): 438-42, 2000 Jan 25.
Article in English | MEDLINE | ID: mdl-10668709

ABSTRACT

BACKGROUND: alpha2 Macroglobulin is a panproteinase inhibitor that is found immunohistochemically in neuritic plaques, a requisite neuropathologic feature of AD. Recently, a pentanucleotide deletion near the 5' end of the "bait region" of the alpha2 macroglobulin (A2M) gene was reported to be associated with AD in a large cohort of sibpairs, in which the mutation conferred a similar odds ratio with AD as the APOE-epsilon4 allele for carriers of at least one copy of the A2M gene (Mantel-Haenszel odds ratio, 3.56). METHODS: We studied three independent association samples of AD patients (n = 309) with an age range of 50 to 94 years and representative controls (n = 281) to characterize the allele frequency of the pentanucleotide deletion in this cohort. We detected the mutation near the 5' splice site of exon 18 using standard PCR and restriction fragment length polymorphism methods. The results were adjusted for age, gender, education, and APOE polymorphism. RESULTS: We found that the A2M gene polymorphism conferred an increased risk for AD, with an estimated Mantel-Haenszel ratio of 1.5 (95% CI 1.1 to 2.2; p = 0.025). There was no age- or gender-dependent increase in A2M gene allele frequencies in AD patients compared with controls. The combined sample showed the expected association between AD and APOE-epsilon 4. In one of our three samples there was an interaction between the A2M and APOE-epsilon4 genes, but the other two samples showed no interaction between the two risk factors. CONCLUSIONS: Our data support an association between the A2M gene and AD. This association is less pronounced, however, in our cohort than in the previously reported sample of sibpairs.


Subject(s)
Alzheimer Disease/epidemiology , Alzheimer Disease/genetics , alpha-Macroglobulins/genetics , Aged , Aged, 80 and over , Apolipoproteins E/genetics , Exons , Female , Gene Deletion , Genetic Predisposition to Disease , Genotype , Humans , Male , Middle Aged , Odds Ratio , Polymorphism, Genetic , Risk Factors
13.
Neurobiol Dis ; 7(1): 9-22, 2000 Feb.
Article in English | MEDLINE | ID: mdl-10671319

ABSTRACT

The contribution of mutations in the amyloid precursor protein (APP) gene known as Flemish (APP/A692G) and Dutch (APP/E693Q) to the pathogenesis of Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis of the Dutch type, respectively, was studied in transgenic mice that overexpress the mutant APP in brain. These transgenic mice showed the same early behavioral disturbances and defects and increased premature death as the APP/London (APP V717I), APP/Swedish (K670N, M671L), and other APP transgenic mice described previously. Pathological changes included intense glial reaction, extensive microspongiosis in the white matter, and apoptotic neurons in select areas of the brain, while amyloid deposits were absent, even in mice over 18 months of age. This contrasts with extensive amyloid deposition in APP/London transgenic mice and less pronounced amyloid deposition in APP/Swedish transgenic mice generated identically. It demonstrated, however, that the behavioral deficiencies and the pathological changes in brain resulting from an impaired neuronal function are caused directly by APP or its proteolytic derivative(s). These accelerate or impinge on the normal process of aging and amyloid deposits per se are not essential for this phenotype.


Subject(s)
Aggression , Amyloid beta-Protein Precursor/genetics , Brain/pathology , Point Mutation , Alzheimer Disease/genetics , Amyloid/analysis , Animals , Brain/ultrastructure , Cell Nucleus/pathology , Cell Nucleus/ultrastructure , Cerebral Amyloid Angiopathy/genetics , Humans , Kainic Acid/toxicity , Lethal Dose 50 , Mice , Mice, Inbred Strains , Mice, Transgenic , N-Methylaspartate/toxicity
14.
J Neurochem ; 74(1): 295-301, 2000 Jan.
Article in English | MEDLINE | ID: mdl-10617132

ABSTRACT

Homozygous APPV717F transgenic mice overexpress a human beta-amyloid precursor protein (betaAPP) minigene encoding a familial Alzheimer's disease mutation. These mice develop Alzheimer-type neuritic beta-amyloid plaques surrounded by astrocytes. S100beta is an astrocyte-derived cytokine that promotes neurite growth and promotes excessive expression of betaAPP. S100beta overexpression in Alzheimer's disease correlates with the proliferation of betaAPP-immunoreactive neurites in beta-amyloid plaques. We found age-related increases in tissue levels of both betaAPP and S100beta mRNA in transgenic mice. Neuronal betaAPP overexpression was found in cell somas in young mice, whereas older mice showed betaAPP overexpression in dystrophic neurites in plaques. These age-related changes were accompanied by progressive increases in S100beta expression, as determined by S100beta load (percent immunoreactive area). These increases were evident as early as 1 and 2 months of age, months before the appearance of beta-amyloid deposits in these mice. Such precocious astrocyte activation and S100beta overexpression are similar to our earlier findings in Down's syndrome. Accelerated age-related overexpression of S100beta may interact with age-associated overexpression of mutant betaAPP in transgenic mice to promote development of Alzheimer-like neuropathological changes.


Subject(s)
Neurites/physiology , Aging/metabolism , Amyloid beta-Protein Precursor/genetics , Animals , Astrocytes/metabolism , Astrocytes/physiology , Female , Glial Fibrillary Acidic Protein/genetics , Hippocampus/cytology , Hippocampus/metabolism , Humans , Immunohistochemistry , Mice , Mice, Transgenic/genetics , Plaque, Amyloid/metabolism , RNA, Messenger/metabolism , S100 Proteins/genetics , S100 Proteins/metabolism
15.
Methods Mol Med ; 32: 139-48, 2000.
Article in English | MEDLINE | ID: mdl-21318516

ABSTRACT

The accumulation of insoluble Aß peptide aggregates in the brain is the diagnostic feature of Alzheimer's disease. Identical deposits are seen in the elderly who are at risk for this disease. The formation of the approx 4 kDa Aß peptide is implicated as a key component in the development of Alzheimer's disease pathology. Genetic evidence strongly supports this contention (1,2), as well as a number of demonstrated relevant biological activities of the Aß peptide such as its neurotoxicity (3) and proinflammatory properties (4). A great deal of attention has been focused on the processes involved in the generation of Aß peptide. In contrast, the fate of this peptide once it has been released from the cell is less well understood. Recently, this situation has been changing as studies on the clearance of Aß peptide are being published. The identification of Aß-degrading enzymes produced in the brain, their class, and selectivity, as well as their cellular origin, are important unresolved questions. One key issue of Aß peptide clearance is whether the brain may be limited in its capacity to degrade this protein, as all cells produce Aß, yet it is seen to accumulate only in brain tissue. Because alterations in Aß peptide clearance may potentially contribute to increased levels and to the development of insoluble Aß deposits in the brains of afflicted individuals, this chapter focuses on specific approaches to clarifying Aß peptide-clearance mechanisms.

16.
J Cell Biol ; 147(2): 277-94, 1999 Oct 18.
Article in English | MEDLINE | ID: mdl-10525535

ABSTRACT

Mutations of presenilin 1 (PS1) causing Alzheimer's disease selectively increase the secretion of the amyloidogenic betaA4(1-42), whereas knocking out the gene results in decreased production of both betaA4(1-40) and (1-42) amyloid peptides (De Strooper et al. 1998). Therefore, PS1 function is closely linked to the gamma-secretase processing of the amyloid precursor protein (APP). Given the ongoing controversy on the subcellular localization of PS1, it remains unclear at what level of the secretory and endocytic pathways PS1 exerts its activity on APP and on the APP carboxy-terminal fragments that are the direct substrates for gamma-secretase. Therefore, we have reinvestigated the subcellular localization of endogenously expressed PS1 in neurons in vitro and in vivo using confocal microscopy and fine-tuned subcellular fractionation. We show that uncleaved PS1 holoprotein is recovered in the nuclear envelope fraction, whereas the cleaved PS fragments are found mainly in post-ER membranes including the intermediate compartment (IC). PS1 is concentrated in discrete sec23p- and p58/ERGIC-53-positive patches, suggesting its localization in subdomains involved in ER export. PS1 is not found to significant amounts beyond the cis-Golgi. Surprisingly, we found that APP carboxy-terminal fragments also coenrich in the pre-Golgi membrane fractions, consistent with the idea that these fragments are the real substrates for gamma-secretase. Functional evidence that PS1 exerts its effects on gamma-secretase processing of APP in the ER/IC was obtained using a series of APP trafficking mutants. These mutants were investigated in hippocampal neurons derived from transgenic mice expressing PS1wt or PS1 containing clinical mutations (PS1(M146L) and PS1(L286V)) at physiologically relevant levels. We demonstrate that the APP-London and PS1 mutations have additive effects on the increased secretion of betaA4(1-42) relative to betaA4(1-40), indicating that both mutations operate independently. Overall, our data clearly establish that PS1 controls gamma(42)-secretase activity in pre-Golgi compartments. We discuss models that reconcile this conclusion with the effects of PS1 deficiency on the generation of betaA4(1-40) peptide in the late biosynthetic and endocytic pathways.


Subject(s)
Amyloid beta-Protein Precursor/physiology , Endopeptidases/metabolism , Hippocampus/physiology , Membrane Proteins/physiology , Amyloid Precursor Protein Secretases , Animals , Aspartic Acid Endopeptidases , Golgi Apparatus/physiology , Golgi Apparatus/ultrastructure , Hippocampus/ultrastructure , Humans , Immunohistochemistry , Mice , Mice, Transgenic , Neurons/physiology , Neurons/ultrastructure , Presenilin-1 , Protein Processing, Post-Translational
17.
J Med Chem ; 42(19): 3889-98, 1999 Sep 23.
Article in English | MEDLINE | ID: mdl-10508437

ABSTRACT

In an effort to rapidly identify potent inhibitors of Abeta production and to probe the amino acid sequence specificity of the protease(s) responsible for the production of this peptide, a large number of dipeptide aldehydes were combinatorially synthesized and manually evaluated for their inhibitory properties. The starting point for this study was the dipeptide aldehyde carbobenzoxyl-valinyl-phenylalanal previously shown to inhibit the production of Abeta in CHO cells stably transfected with the cDNA encoding betaAPP695. Pools of related dipeptide aldehydes were combinatorially synthesized, and the most active pool was deconvoluted, resulting in the identification of the most active inhibitor of this pool. Systematic optimization of this inhibitor resulted in a series of dipeptide aldehydes with enhanced potencies relative to carbobenzoxyl-valinyl-phenylalanal. The most active dipeptide aldehydes were those that possessed hydrophobic amino acids at both the P1 and P2 positions. The most potent compound identified in this study was 3, 5-dimethoxycinnamamide-isoleucinyl-leucinal with an IC(50) of 9.6 microM, approximately 10-fold more active than carbobenzoxyl-valinyl-phenylalanal. In immunoprecipitation experiments using antibodies directed toward either Abeta1-40 or Abeta1-42, 3,5-dimethoxycinnamamide-isoleucinyl-leucinal, like carbobenzoxyl-valinyl-phenylalanal, preferentially inhibited the shorter 1-40 form of Abeta, whereas the longer 1-42 form was not as strongly inhibited. These results suggest that dipeptide aldehydes related to carbobenzoxyl-valinyl-phenylalanal inhibit Abeta through similar mechanisms and demonstrate the utility of a combinatorial synthesis approach to rapidly identify potent inhibitors of Abeta production.


Subject(s)
Aldehydes , Amyloid beta-Peptides/biosynthesis , Dipeptides/chemical synthesis , Peptide Library , Animals , Binding Sites , CHO Cells , Cell Line , Cricetinae , Humans , Immunoenzyme Techniques , Mass Spectrometry , Models, Chemical
18.
J Biol Chem ; 274(10): 6483-92, 1999 Mar 05.
Article in English | MEDLINE | ID: mdl-10037741

ABSTRACT

Transgenic mice overexpressing different forms of amyloid precursor protein (APP), i.e. wild type or clinical mutants, displayed an essentially comparable early phenotype in terms of behavior, differential glutamatergic responses, deficits in maintenance of long term potentiation, and premature death. The cognitive impairment, demonstrated in F1 hybrids of the different APP transgenic lines, was significantly different from nontransgenic littermates as early as 3 months of age. Biochemical analysis of secreted and membrane-bound APP, C-terminal "stubs," and Abeta(40) and Abeta(42) peptides in brain indicated that no single intermediate can be responsible for the complex of phenotypic dysfunctions. As expected, the Abeta(42) levels were most prominent in APP/London transgenic mice and correlated directly with the formation of amyloid plaques in older mice of this line. Plaques were associated with immunoreactivity for hyperphosphorylated tau, eventually signaling some form of tau pathology. In conclusion, the different APP transgenic mouse lines studied display cognitive deficits and phenotypic traits early in life that dissociated in time from the formation of amyloid plaques and will be good models for both early and late neuropathological and clinical aspects of Alzheimer's disease.


Subject(s)
Amyloid beta-Protein Precursor/genetics , Brain/physiology , Mice, Transgenic/physiology , Mutation , Alzheimer Disease/genetics , Amyloid beta-Protein Precursor/biosynthesis , Animals , Electrophysiology , Gene Expression , Hippocampus/physiology , Mice
19.
J Biol Chem ; 273(33): 20967-71, 1998 Aug 14.
Article in English | MEDLINE | ID: mdl-9694846

ABSTRACT

In Alzheimer's disease (AD), a chronic cerebral inflammatory state is thought to lead to neuronal injury. Microglia, intrinsic cerebral immune effector cells, are likely to be key in the pathophysiology of this inflammatory state. We showed that macrophage colony-stimulating factor, a microglial activator found at increased levels in the central nervous system in AD, dramatically augments beta-amyloid peptide (betaAP)-induced microglial production of interleukin-1, interleukin-6, and nitric oxide. In contrast, granulocyte macrophage colony-stimulating factor, another hematopoietic cytokine found in the AD brain, did not augment betaAP-induced microglial secretory activity. These results indicate that increased macrophage colony-stimulating factor levels in AD could magnify betaAP-induced microglial inflammatory cytokine and nitric oxide production, which in turn could intensify the cerebral inflammatory state by activating astrocytes and additional microglia, as well as directly injuring neurons.


Subject(s)
Amyloid beta-Peptides/pharmacology , Interleukin-1/biosynthesis , Interleukin-6/biosynthesis , Macrophage Colony-Stimulating Factor/pharmacology , Microglia/drug effects , Nitric Oxide/biosynthesis , Alzheimer Disease/metabolism , Animals , Cell Line, Transformed , Granulocyte-Macrophage Colony-Stimulating Factor/pharmacology , Mice , Microglia/metabolism
20.
Revolution ; 7(2): 43-5, 1997.
Article in English | MEDLINE | ID: mdl-9277311

ABSTRACT

Empowerment amounts to a social process of recognizing, promoting and enhancing staff nurse abilities to meet self needs, solve their own problems and mobilize the necessary resources to gain mastery over their own professional lives. Healing, to be made whole, is a process of getting in touch with that which is impeding our realization of wholeness. Empowerment as a source of organizational healing conveys the message that in order to realize wholeness, nurses are dependent upon personal and organizational resources. As nurses learn multiple ways to interact with the work environment, they find the path to a wholeness that incorporates physical, emotional, intellectual, and spiritual aspects of themselves. As the value of wholeness is realized individually, interactions with the environment spontaneously manifest these attributes and the message permeates the nursing community. As the nursing community is empowered, it is increasingly able to empower the individual. This expanding energy can result in a synergistic pattern that brings phenomena together, and interrelates them, creating a new and greater whole from the disparate, seemingly conflicting parts. When nurses as individuals and groups are able and willing (empowered) to invest energy to that which impacts their lives so that they can move toward wholeness (heal), positive energy exponentially intensifies and permeates the environment to envelop all.


Subject(s)
Decision Making, Organizational , Interprofessional Relations , Nurse Administrators/psychology , Nursing Staff/psychology , Nursing, Supervisory/organization & administration , Power, Psychological , Humans
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