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

RESUMO

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.


Assuntos
Envelhecimento/genética , Envelhecimento/fisiologia , Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/fisiologia , Aprendizagem/fisiologia , Doença de Alzheimer/etiologia , Doença de Alzheimer/patologia , Doença de Alzheimer/psicologia , Animais , Modelos Animais de Doenças , Comportamento Exploratório/fisiologia , Humanos , Masculino , Aprendizagem em Labirinto/fisiologia , Camundongos , Camundongos Transgênicos , Placa Amiloide/patologia , Comportamento Espacial/fisiologia
2.
Mol Biotechnol ; 18(1): 1-10, 2001 May.
Artigo em Inglês | MEDLINE | ID: mdl-11439695

RESUMO

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.


Assuntos
Peptídeos beta-Amiloides/química , Ácido Aspártico Endopeptidases , Bioquímica/métodos , Endopeptidases/análise , Endopeptidases/química , Glicoproteínas/química , Proteínas de Membrana/química , Doença de Alzheimer/diagnóstico , Secretases da Proteína Precursora do Amiloide , Apoptose , Ligação Competitiva , Western Blotting , Caspase 3 , Caspases/metabolismo , Linhagem Celular , Clonagem Molecular , Glicoproteínas/metabolismo , Humanos , Proteínas de Membrana/metabolismo , Mutagênese Sítio-Dirigida , Ligação Proteica , Fatores de Tempo , Transfecção
3.
J Biol Chem ; 276(33): 30701-7, 2001 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-11402035

RESUMO

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.


Assuntos
Proteínas Quinases Dependentes de Cálcio-Calmodulina/fisiologia , Proteínas de Membrana/análise , Fragmentos de Peptídeos/análise , Motivos de Aminoácidos , Sequência de Aminoácidos , Células Cultivadas , Dimerização , Quinase 3 da Glicogênio Sintase , Quinases da Glicogênio Sintase , Humanos , Proteínas de Membrana/química , Dados de Sequência Molecular , Fosforilação , Presenilina-1
4.
Neuroreport ; 12(6): 1265-70, 2001 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-11338204

RESUMO

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.


Assuntos
Doença de Alzheimer/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Apolipoproteínas E/metabolismo , Encéfalo/metabolismo , Modelos Animais de Doenças , Alelos , Peptídeos beta-Amiloides/metabolismo , Animais , Ensaio de Imunoadsorção Enzimática , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Solubilidade
5.
J Biol Chem ; 276(10): 7366-75, 2001 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-11104755

RESUMO

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.


Assuntos
Proteínas Quinases Dependentes de Cálcio-Calmodulina/química , Proteínas do Citoesqueleto/química , Proteínas de Membrana/química , Transdução de Sinais , Transativadores , Doença de Alzheimer/metabolismo , Motivos de Aminoácidos , Sequência de Aminoácidos , Peptídeos beta-Amiloides/química , Apoptose , Sítios de Ligação , Western Blotting , Morte Celular , Linhagem Celular , Núcleo Celular/metabolismo , Proteínas do Citoesqueleto/metabolismo , Proteínas do Citoesqueleto/fisiologia , Citosol/metabolismo , DNA Complementar/metabolismo , Vetores Genéticos , Quinase 3 da Glicogênio Sintase , Quinases da Glicogênio Sintase , Humanos , Luciferases/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/fisiologia , Microscopia de Fluorescência , Modelos Moleculares , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Mutação , Fragmentos de Peptídeos/química , Fosforilação , Testes de Precipitina , Presenilina-1 , Ligação Proteica , Estrutura Terciária de Proteína , Homologia de Sequência de Aminoácidos , Serina/química , Transfecção , beta Catenina
6.
Neurobiol Aging ; 22(6): 895-902, 2001.
Artigo em Inglês | MEDLINE | ID: mdl-11754996

RESUMO

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.


Assuntos
Doença de Alzheimer/genética , Caspase 1/biossíntese , Caspase 1/genética , Dano ao DNA/fisiologia , Regulação Enzimológica da Expressão Gênica/genética , Neurônios/metabolismo , Animais , Feminino , Humanos , Imuno-Histoquímica , Marcação In Situ das Extremidades Cortadas , Camundongos , Camundongos Transgênicos , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Coloração pela Prata
7.
Brain ; 123 Pt 12: 2467-74, 2000 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-11099448

RESUMO

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.


Assuntos
Doença de Alzheimer/genética , Doença de Alzheimer/patologia , Proteínas de Membrana/genética , Mutação/genética , Adulto , Doença de Alzheimer/complicações , Transtornos Cognitivos/etiologia , Síndrome de Creutzfeldt-Jakob/diagnóstico , Análise Mutacional de DNA , Diagnóstico Diferencial , Progressão da Doença , Eletroencefalografia , Inglaterra , Evolução Fatal , Feminino , Humanos , Íntrons/genética , Mioclonia/etiologia , Linhagem , Presenilina-1 , Convulsões/etiologia
8.
Am J Pathol ; 157(3): 895-904, 2000 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-10980129

RESUMO

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.


Assuntos
Doença de Alzheimer/metabolismo , Precursor de Proteína beta-Amiloide/fisiologia , Receptor de Fator Estimulador de Colônias de Macrófagos/biossíntese , Doença de Alzheimer/genética , Neuropatias Amiloides/metabolismo , Neuropatias Amiloides/patologia , Peptídeos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/genética , Animais , Western Blotting , Cerebelo/metabolismo , Córtex Cerebral/metabolismo , Técnica Indireta de Fluorescência para Anticorpo , Hipocampo/metabolismo , Fator Estimulador de Colônias de Macrófagos/biossíntese , Fator Estimulador de Colônias de Macrófagos/genética , Camundongos , Camundongos Transgênicos , Microglia/metabolismo , Microglia/patologia , Microscopia Confocal , Placa Amiloide/metabolismo , Placa Amiloide/patologia , RNA Mensageiro/metabolismo , Receptor de Fator Estimulador de Colônias de Macrófagos/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa
9.
J Biol Chem ; 275(44): 34086-91, 2000 Nov 03.
Artigo em Inglês | MEDLINE | ID: mdl-10915801

RESUMO

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.


Assuntos
Endopeptidases/efeitos dos fármacos , Inibidores Enzimáticos/metabolismo , Proteínas de Membrana/metabolismo , Secretases da Proteína Precursora do Amiloide , Membrana Celular/metabolismo , Endopeptidases/metabolismo , Testes de Precipitina , Presenilina-1 , Presenilina-2 , Especificidade por Substrato
10.
J Biol Chem ; 275(41): 31770-7, 2000 Oct 13.
Artigo em Inglês | MEDLINE | ID: mdl-10918055

RESUMO

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.


Assuntos
Apolipoproteínas E/isolamento & purificação , Glicoproteínas/isolamento & purificação , Lipoproteínas LDL/química , Lipossomos/química , Microglia/química , Chaperonas Moleculares , Proteínas do Tecido Nervoso/isolamento & purificação , Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Animais , Apolipoproteínas E/química , Apolipoproteínas E/imunologia , Apolipoproteínas E/ultraestrutura , Western Blotting , Morte Celular/efeitos dos fármacos , Células Cultivadas , Cromatografia em Gel , Clusterina , Meios de Cultivo Condicionados/química , Eletroforese em Gel de Poliacrilamida , Glicoproteínas/química , Glicoproteínas/imunologia , Glicoproteínas/ultraestrutura , Cinética , Lipoproteínas LDL/metabolismo , Lipoproteínas LDL/ultraestrutura , Lipossomos/metabolismo , Lovastatina/análogos & derivados , Lovastatina/farmacologia , Camundongos , Microglia/citologia , Microglia/metabolismo , Microscopia Eletrônica , Proteínas do Tecido Nervoso/química , Proteínas do Tecido Nervoso/imunologia , Proteínas do Tecido Nervoso/ultraestrutura , Neurônios/citologia , Neurônios/efeitos dos fármacos , Tamanho da Partícula , Placa Amiloide/química , Placa Amiloide/metabolismo , Ligação Proteica , Ratos
12.
Neurobiol Dis ; 7(1): 9-22, 2000 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-10671319

RESUMO

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.


Assuntos
Agressão , Precursor de Proteína beta-Amiloide/genética , Encéfalo/patologia , Mutação Puntual , Doença de Alzheimer/genética , Amiloide/análise , Animais , Encéfalo/ultraestrutura , Núcleo Celular/patologia , Núcleo Celular/ultraestrutura , Angiopatia Amiloide Cerebral/genética , Humanos , Ácido Caínico/toxicidade , Dose Letal Mediana , Camundongos , Camundongos Endogâmicos , Camundongos Transgênicos , N-Metilaspartato/toxicidade
13.
Neurology ; 54(2): 438-42, 2000 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-10668709

RESUMO

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.


Assuntos
Doença de Alzheimer/epidemiologia , Doença de Alzheimer/genética , alfa-Macroglobulinas/genética , Idoso , Idoso de 80 Anos ou mais , Apolipoproteínas E/genética , Éxons , Feminino , Deleção de Genes , Predisposição Genética para Doença , Genótipo , Humanos , Masculino , Pessoa de Meia-Idade , Razão de Chances , Polimorfismo Genético , Fatores de Risco
14.
J Neurochem ; 74(1): 295-301, 2000 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-10617132

RESUMO

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.


Assuntos
Neuritos/fisiologia , Envelhecimento/metabolismo , Precursor de Proteína beta-Amiloide/genética , Animais , Astrócitos/metabolismo , Astrócitos/fisiologia , Feminino , Proteína Glial Fibrilar Ácida/genética , Hipocampo/citologia , Hipocampo/metabolismo , Humanos , Imuno-Histoquímica , Camundongos , Camundongos Transgênicos/genética , Placa Amiloide/metabolismo , RNA Mensageiro/metabolismo , Proteínas S100/genética , Proteínas S100/metabolismo
15.
Methods Mol Med ; 32: 139-48, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-21318516

RESUMO

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 Med Chem ; 42(19): 3889-98, 1999 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-10508437

RESUMO

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.


Assuntos
Aldeídos , Peptídeos beta-Amiloides/biossíntese , Dipeptídeos/síntese química , Biblioteca de Peptídeos , Animais , Sítios de Ligação , Células CHO , Linhagem Celular , Cricetinae , Humanos , Técnicas Imunoenzimáticas , Espectrometria de Massas , Modelos Químicos
17.
J Cell Biol ; 147(2): 277-94, 1999 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-10525535

RESUMO

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.


Assuntos
Precursor de Proteína beta-Amiloide/fisiologia , Endopeptidases/metabolismo , Hipocampo/fisiologia , Proteínas de Membrana/fisiologia , Secretases da Proteína Precursora do Amiloide , Animais , Ácido Aspártico Endopeptidases , Complexo de Golgi/fisiologia , Complexo de Golgi/ultraestrutura , Hipocampo/ultraestrutura , Humanos , Imuno-Histoquímica , Camundongos , Camundongos Transgênicos , Neurônios/fisiologia , Neurônios/ultraestrutura , Presenilina-1 , Processamento de Proteína Pós-Traducional
18.
J Biol Chem ; 274(10): 6483-92, 1999 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-10037741

RESUMO

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.


Assuntos
Precursor de Proteína beta-Amiloide/genética , Encéfalo/fisiologia , Camundongos Transgênicos/fisiologia , Mutação , Doença de Alzheimer/genética , Precursor de Proteína beta-Amiloide/biossíntese , Animais , Eletrofisiologia , Expressão Gênica , Hipocampo/fisiologia , Camundongos
19.
J Biol Chem ; 273(33): 20967-71, 1998 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-9694846

RESUMO

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.


Assuntos
Peptídeos beta-Amiloides/farmacologia , Interleucina-1/biossíntese , Interleucina-6/biossíntese , Fator Estimulador de Colônias de Macrófagos/farmacologia , Microglia/efeitos dos fármacos , Óxido Nítrico/biossíntese , Doença de Alzheimer/metabolismo , Animais , Linhagem Celular Transformada , Fator Estimulador de Colônias de Granulócitos e Macrófagos/farmacologia , Camundongos , Microglia/metabolismo
20.
Revolution ; 7(2): 43-5, 1997.
Artigo em Inglês | MEDLINE | ID: mdl-9277311

RESUMO

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.


Assuntos
Tomada de Decisões Gerenciais , Relações Interprofissionais , Enfermeiros Administradores/psicologia , Recursos Humanos de Enfermagem/psicologia , Supervisão de Enfermagem/organização & administração , Poder Psicológico , Humanos
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