RESUMO
Accumulation of toxic protein aggregates-amyloid-ß (Aß) plaques and hyperphosphorylated tau tangles-is the pathological hallmark of Alzheimer disease (AD). Aß accumulation has been hypothesized to result from an imbalance between Aß production and clearance; indeed, Aß clearance seems to be impaired in both early and late forms of AD. To develop efficient strategies to slow down or halt AD, it is critical to understand how Aß is cleared from the brain. Extracellular Aß deposits can be removed from the brain by various clearance systems, most importantly, transport across the blood-brain barrier. Findings from the past few years suggest that astroglial-mediated interstitial fluid (ISF) bulk flow, known as the glymphatic system, might contribute to a larger portion of extracellular Aß (eAß) clearance than previously thought. The meningeal lymphatic vessels, discovered in 2015, might provide another clearance route. Because these clearance systems act together to drive eAß from the brain, any alteration to their function could contribute to AD. An understanding of Aß clearance might provide strategies to reduce excess Aß deposits and delay, or even prevent, disease onset. In this Review, we describe the clearance systems of the brain as they relate to proteins implicated in AD pathology, with the main focus on Aß.
Assuntos
Doença de Alzheimer/metabolismo , Encéfalo/metabolismo , Absorção Fisiológica/fisiologia , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/metabolismo , Biomarcadores/metabolismo , Barreira Hematoencefálica/metabolismo , Encéfalo/irrigação sanguínea , Proteínas do Líquido Cefalorraquidiano/metabolismo , Líquido Extracelular/metabolismo , Humanos , Sistema Linfático/fisiologia , Proteólise , Fatores de Risco , Proteínas tau/metabolismoAssuntos
Apolipoproteína E4/líquido cefalorraquidiano , Barreira Hematoencefálica/metabolismo , Ciclofilina A/líquido cefalorraquidiano , Metaloproteinase 9 da Matriz/líquido cefalorraquidiano , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Feminino , Genótipo , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
Cerebral amyloid angiopathy (CAA) is increasingly recognized as a major contributor of Alzheimer's disease (AD) pathogenesis. To date, vascular deposits and not parenchymal plaques appear more sensitive predictors of dementia. Amyloid deposition in and around cerebral blood vessels plays a central role in a series of response mechanisms that lead to changes in the integrity of the blood-brain barrier, extravasations of plasma proteins, edema formation, release of inflammatory mediators and matrix metalloproteases which, in turn, produce partial degradation of the basal lamina with the potential to develop hemorrhagic complications. The progressive buildup of amyloid deposits in and around blood vessels chronically limits blood supply and causes focal deprivation of oxygen, triggering a secondary cascade of metabolic events several of which involve the generation of nitrogen and oxygen free radicals with consequent oxidative stress and cell toxicity. Many aspects of CAA in early- and late-onset AD -the special preference of Aß40 to deposit in the vessel walls, the favored vascular compromise associated with many Aß genetic variants, the puzzling observation that some of these vasculotropic variants solely manifest with recurrent hemorrhagic episodes while others are mainly associated with dementia- await clarification. Non-Aß cerebral amyloidoses reinforce the viewpoint that plaque burden is not indicative of dementia while highlighting the relevance of nonfibrillar lesions and vascular involvement in the disease pathogenesis. The lessons learned from the comparative study of Aß and non-Aß cerebral amyloidosis provide new avenues and alternative models to study the role of amyloid in the molecular basis of neurodegeneration.
RESUMO
Amyloid molecules harboring pyroglutamate (pGlu) residue at the N-termini are considered to be important for the development of cerebral amyloidosis such as Alzheimer's disease and thought to be either spontaneously generated or being catalyzed by glutaminyl cyclase. Familial British dementia (FBD) is an autosomal dominant form of dementia neuropathologically characterized by parenchymal amyloid and preamyloid deposits, extensive cerebral amyloid angiopathy, and neurofibrillary tangles. FBD is caused by a stop to Arg mutation in the BRI2 gene, generating de novo created amyloid molecule ABri which accumulates in FBD brains but is not present in the normal population. Soluble ABri molecules present in the circulation of carriers of the BRI2 mutation are 34 amino acids long exclusively harboring Glu residue at the N-termini (ABri1-34E), whereas water- and formic acid-soluble ABri molecules extracted from FBD brains have abundant ABri species bearing pGlu residue (ABri1-34pE), suggesting that pyroglutamate formation occurs at the site of deposition. In order to further clarify the mechanism (s) of ABri deposition, we studied whether pyroglutamate formation indeed occurs outside the central nervous system taking advantage that FBD is also a systemic amyloidosis. Soluble and fibrillar ABri molecules extracted from systemic organs and analyzed biochemically using a combination of immunoprecipitation, mass spectrometry, and western blot analysis were oligomeric in size and contained a large proportion of ABri1-34pE. The data indicate that pyroglutamate formation at the N-termini of ABri molecules is an early step in the process of FBD amyloid deposition, and its formation is not restricted to the central nervous system.
RESUMO
Mutations within the amyloid-beta (Abeta) sequence, especially those clustered at residues 21-23, which are linked to early onset familial Alzheimer's disease (AD), are primarily associated with cerebral amyloid angiopathy (CAA). The basis for this predominant vascular amyloid burden and the differential clinical phenotypes of cerebral hemorrhage/stroke in some patients and dementia in others remain unknown. The AbetaD23N Iowa mutation is associated with progressive AD-like dementia, often without clinically manifested intracerebral hemorrhage. Neuropathologically, the disease is characterized by predominant preamyloid deposits, severe CAA, and abundant neurofibrillary tangles in the presence of remarkably few mature plaques. Biochemical analyses using a combination of immunoprecipitation, mass spectrometry, amino acid sequence, and Western blot analysis performed after sequential tissue extractions to separately isolate soluble components, preamyloid, and fibrillar amyloid species indicated that the Iowa deposits are complex mixtures of mutated and nonmutated Abeta molecules. These molecules exhibited various degrees of solubility, were highly heterogeneous at both the N- and C-termini, and showed partial aspartate isomerization at positions 1, 7, and 23. This collection of Abeta species-the Iowa brain Abeta peptidome-contained clear imprints of amyloid clearance mechanisms yet highlighted the unique neuropathological features shared by a non-Abeta cerebral amyloidosis, familial Danish dementia, in which neurofibrillary tangles coexist with extensive pre-amyloid deposition in the virtual absence of fibrillar lesions. These data therefore challenge the importance of neuritic plaques as the sole contributors for the development of dementia.
Assuntos
Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/genética , Peptídeos beta-Amiloides/metabolismo , Angiopatia Amiloide Cerebral/metabolismo , Processamento de Proteína Pós-Traducional , Idoso , Idoso de 80 Anos ou mais , Encéfalo/patologia , Demência/metabolismo , Feminino , Humanos , Imuno-Histoquímica/métodos , Iowa , Masculino , Pessoa de Meia-Idade , Mutação , Estrutura Terciária de ProteínaRESUMO
Immunotherapy holds great promise for Alzheimer's disease (AD) and other conformational disorders but certain adverse reactions need to be overcome. Prior to the side effects in the first Elan/Wyeth AD vaccine trial, we proposed using amyloid-beta (Abeta) derivatives as a safer approach. The route of administration may also affect vaccine safety. To assess the feasibility of oral immunization that promotes mucosal immunity, Tg2576 AD model mice were treated prophylactically three times over 6 weeks starting at 3-5 months of age with a Salmonella vaccine expressing K6Abeta(1-30). At 22-24 months of age, cortical Abeta plaque burden and total Abeta(40/42) levels were reduced by 48-75% in the immunized mice compared to controls, which received unmodified Salmonella. Plaque clearance was not associated with increased microglial activation, which may be explained by the long treatment period. Furthermore, cerebral microhemorrhages were not increased in the treated mice in contrast to several passive Abeta antibody studies. These results further support our findings with this immunogen delivered subcutaneously and demonstrate its efficacy when given orally, which may provide added benefits for human use.
Assuntos
Doença de Alzheimer/prevenção & controle , Vacinas contra Alzheimer/imunologia , Peptídeos beta-Amiloides/imunologia , Administração Oral , Vacinas contra Alzheimer/administração & dosagem , Animais , Hemorragia Cerebral/etiologia , Hemorragia Cerebral/prevenção & controle , Modelos Animais de Doenças , Ensaio de Imunoadsorção Enzimática , Feminino , Imunoglobulinas/sangue , Imuno-Histoquímica , Masculino , Camundongos , Camundongos Transgênicos , Fragmentos de Peptídeos , Salmonella/genética , Vacinas Sintéticas/administração & dosagem , Vacinas Sintéticas/imunologiaRESUMO
In cerebral amyloid angiopathy (CAA), amyloid fibrils deposit in walls of arteries, arterioles and less frequently in veins and capillaries of the central nervous system, often resulting in secondary degenerative vascular changes. Although the amyloid-beta peptide is by far the commonest amyloid subunit implicated in sporadic and rarely in hereditary forms of CAA, a number of other proteins may also be involved in rare familial diseases in which CAA is also a characteristic morphological feature. These latter proteins include the ABri and ADan subunits in familial British dementia and familial Danish dementia, respectively, which are also known under the umbrella term BRI2 gene-related dementias, variant cystatin C in hereditary cerebral haemorrhage with amyloidosis of Icelandic-type, variant transthyretins in meningo-vascular amyloidosis, disease-associated prion protein (PrP(Sc)) in hereditary prion disease with premature stop codon mutations and mutated gelsolin (AGel) in familial amyloidosis of Finnish type. In this review, the characteristic morphological features of the different CAAs is described and the implication of the biochemical, genetic and transgenic animal data for the pathogenesis of CAA is discussed.
Assuntos
Encéfalo/irrigação sanguínea , Angiopatia Amiloide Cerebral/genética , Angiopatia Amiloide Cerebral/patologia , Doença de Alzheimer/complicações , Doença de Alzheimer/terapia , Peptídeos beta-Amiloides/metabolismo , Amiloidose/complicações , Amiloidose/genética , Animais , Encéfalo/metabolismo , Encéfalo/patologia , Encéfalo/fisiopatologia , Angiopatia Amiloide Cerebral/fisiopatologia , Angiopatia Amiloide Cerebral/terapia , Hemorragia Cerebral/complicações , Hemorragia Cerebral/genética , Cistatina C/genética , Demência/complicações , Demência/genética , Modelos Animais de Doenças , Predisposição Genética para Doença , Humanos , Imunoterapia , Mutação , Pré-Albumina/metabolismo , Doenças Priônicas/complicaçõesRESUMO
We have been developing Abeta derivative vaccines with the objective to improve the safety of Abeta targeting immunotherapy. Our Abeta homologs are designed to have less direct toxicity and to produce a modified immune response compared to Abeta. In extensive mouse studies, all our vaccines have improved cognition in transgenic mice while eliciting different immune responses and reducing brain amyloid burden to a variable degree. While we are continuing to characterize these vaccines in mice, in preparation for studies in old primates and for human trials we assessed their effect in young lemur primates (n=25) that with age develop Abeta plaques and tau aggregates as seen in Alzheimer's disease. In the primates, all the peptides administered with alum adjuvant elicited a moderate to robust anti-Abeta IgM response. Abeta1-42, K6Abeta1-30 and K6Abeta1-30[E(18)E(19)] resulted in a high anti-Abeta IgG response, whereas Abeta1-30[E(18)E(19)] produced a weaker more variable IgG titer. Notably, 22 weeks after the 3rd immunization, IgM and IgG levels in derivative-vaccinated primates were similar to preimmune values whereas Abeta1-42 treated primates maintained a moderate IgG titer. The increase in antibodies that recognized Abeta1-40 often correlated with increase in Abeta1-40 in plasma, which suggests that the antibodies were binding to Abeta in vivo. Interestingly, significant transient weight gain was observed (K6Abeta1-30-, Abeta1-30[E(18)E(19)]- and Abeta1-42-treated) or a trend in the same direction (K6Abeta1-30[E(18)E(19)]-treated, adjuvant controls) following the injections. Based on these findings, we have chosen K6Abeta1-30 for immunizations in old primates as the antibody response to this vaccine was less variable compared to other Abeta derivatives. Our present findings indicate that most of our Abeta derivatives elicit a substantial antibody response in primates, and importantly this effect is reversible which enhances the safety profile of our approach.
Assuntos
Vacinas contra Alzheimer/imunologia , Peptídeos beta-Amiloides/sangue , Peptídeos beta-Amiloides/imunologia , Formação de Anticorpos , Fragmentos de Peptídeos/sangue , Fragmentos de Peptídeos/imunologia , Plasma/química , Adjuvantes Imunológicos/administração & dosagem , Compostos de Alúmen/administração & dosagem , Animais , Peso Corporal , Encéfalo/patologia , Cheirogaleidae , Feminino , Imunoglobulina G/sangue , Imunoglobulina M/sangue , MasculinoRESUMO
The increasing knowledge of the exact biochemical nature of the localized and systemic amyloid disorders has made a logical and easily understood nomenclature absolutely necessary. Such a nomenclature, biochemically based, has been used for several years but the current literature is still mixed up with many clinical and histochemically based designations from the time when amyloid in general was poorly understood. All amyloid types are today preferably named by their major fibril protein. This makes a simple and rational nomenclature for the increasing number of amyloid disorders known in humans and animals.
Assuntos
Amiloide/classificação , Amiloidose/classificação , Amiloide/metabolismo , Amiloidose/metabolismo , Amiloidose/patologia , Animais , HumanosRESUMO
OBJECTIVE: To describe a novel molecular and pathological phenotype of Creutzfeldt-Jakob disease. Patient A 69-year-old woman with behavioral and personality changes followed by rapidly evolving dementia. RESULTS: Postmortem examination of the brain showed intracellular prion protein deposition and axonal swellings filled with amyloid fibrils. Biochemical analysis of the pathological prion protein disclosed a previously unrecognized PrP(Sc) tertiary structure lacking diglycosylated species. Genetic analysis revealed a wild-type prion protein gene. The prion agent responsible for this atypical phenotype was successfully passaged to bank voles. CONCLUSION: To our knowledge, our results define a new human prion disorder characterized by intracellular accumulation of a novel type of pathological prion protein.
Assuntos
Síndrome de Creutzfeldt-Jakob/metabolismo , Proteínas PrPSc/metabolismo , Idoso , Animais , Arvicolinae , Encéfalo/metabolismo , Encéfalo/patologia , Encéfalo/ultraestrutura , Síndrome de Creutzfeldt-Jakob/genética , Síndrome de Creutzfeldt-Jakob/transmissão , Evolução Fatal , Feminino , Genótipo , Glicosilação , Humanos , Immunoblotting , Espectrometria de Massas , Microscopia Imunoeletrônica , Fenótipo , Proteína PrP 27-30/química , Proteína PrP 27-30/genética , Proteína PrP 27-30/metabolismo , Proteínas PrPSc/química , Proteínas PrPSc/genética , Conformação Proteica , Estrutura Terciária de ProteínaRESUMO
Two hereditary forms of cerebrovascular amyloidosis, familial British and Danish dementias (FBD and FDD), share striking similarities with Alzheimer's disease (AD) despite structural differences among their amyloid subunits (ABri in FBD, ADan in FDD, and Abeta in AD). Neuropathological lesions in these disorders include neurofibrillary tangles, parenchymal amyloid and pre-amyloid deposits and overwhelming cerebral amyloid angiopathy co-localizing with reactive microglia and multiple amyloid associated proteins including activation products of the complement cascade. Immunohistochemical analysis of FBD and FDD brain lesions unveiled the presence of serum amyloid P-component (SAP) primarily associated with thioflavin positive amyloid deposits in spite of the significant pre-amyloid burden existing in both disorders. Using affinity chromatography and ELISA binding assays we demonstrated specific, calcium-dependent, saturable, high affinity binding interactions between SAP and ABri/ADan peptides, with dissociation constant values in the sub-nanomolar range and within the same order of magnitude as those resulting from the interaction of SAP with Alzheimer's Abeta1-40 and Abeta1-42. The preferential association of SAP with fibrillar amyloid lesions and not with non-fibrillar pre-amyloid deposits is puzzling, suggesting that SAP modulates the assembly and stability of the final fibril rather than participating in the early steps of protein misfolding and oligomerization.
Assuntos
Encéfalo/metabolismo , Angiopatia Amiloide Cerebral Familiar/metabolismo , Demência/metabolismo , Placa Amiloide/metabolismo , Componente Amiloide P Sérico/metabolismo , Proteínas Adaptadoras de Transdução de Sinal , Idoso , Amiloide/metabolismo , Peptídeos beta-Amiloides/metabolismo , Benzotiazóis , Biomarcadores/metabolismo , Encéfalo/patologia , Encéfalo/fisiopatologia , Angiopatia Amiloide Cerebral Familiar/patologia , Angiopatia Amiloide Cerebral Familiar/fisiopatologia , Demência/patologia , Demência/fisiopatologia , Dinamarca , Inglaterra , Humanos , Imuno-Histoquímica , Glicoproteínas de Membrana , Proteínas de Membrana , Neurofibrilas/metabolismo , Neurofibrilas/patologia , Fragmentos de Peptídeos/metabolismo , Placa Amiloide/patologia , Subunidades Proteicas/metabolismo , Tiazóis/metabolismoRESUMO
Immunotherapy holds great promise for Alzheimer's disease (AD) and other conformational disorders but certain adverse reactions need to be overcome. The meningoencephalitis observed in the first AD vaccination trial was likely related to excessive cell-mediated immunity caused by the immunogen, amyloid-beta (Abeta) 1-42, and the adjuvant, QS-21. To avoid this toxicity, we have been using Abeta derivatives in alum adjuvant that promotes humoral immunity. Other potential side effects of immunotherapy are increased vascular amyloid and associated microhemorrhages that may be related to rapid clearance of parenchymal amyloid. Here, we determined if our immunization strategy was associated with this form of toxicity, and if the therapeutic effect was age-dependent. Tg2576 mice and wild-type littermates were immunized from 11 or 19 months and their behaviour evaluated prior to killing at 24 months. Subsequently, plaque- and vascular-Abeta burden, Abeta levels and associated pathology was assessed. The therapy started at the cusp of amyloidosis reduced cortical Abeta deposit burden by 31% and Abeta levels by 30-37%, which was associated with cognitive improvements. In contrast, treatment from 19 months, when pathology is well established, was not immunogenic and therefore did not reduce Abeta burden or improve cognition. Significantly, the immunotherapy in the 11-24 months treatment group, that reduced Abeta burden, did not increase cerebral bleeding or vascular Abeta deposits in contrast to several Abeta antibody studies. These findings indicate that our approach age-dependently improves cognition and reduces Abeta burden when used with an adjuvant suitable for humans, without increasing vascular Abeta deposits or microhemorrhages.
Assuntos
Adjuvantes Imunológicos/administração & dosagem , Doença de Alzheimer/prevenção & controle , Vacinas contra Alzheimer , Peptídeos beta-Amiloides/uso terapêutico , Hemorragia Cerebral/etiologia , Vacinação/métodos , Fatores Etários , Compostos de Alúmen/administração & dosagem , Doença de Alzheimer/imunologia , Doença de Alzheimer/patologia , Vacinas contra Alzheimer/uso terapêutico , Peptídeos beta-Amiloides/análise , Peptídeos beta-Amiloides/imunologia , Animais , Encéfalo/imunologia , Encéfalo/patologia , Cognição , Modelos Animais de Doenças , Ensaio de Imunoadsorção Enzimática , Feminino , Processamento de Imagem Assistida por Computador , Imuno-Histoquímica , Masculino , Aprendizagem em Labirinto , Camundongos , Camundongos Transgênicos , Atividade Motora , Fragmentos de Peptídeos/imunologia , Fragmentos de Peptídeos/uso terapêutico , Placa Amiloide/patologia , Fatores de TempoRESUMO
It was proposed that insulin-degrading enzyme (IDE) participates in the clearance of amyloid beta (Abeta) in the brain, and its low expression or activity may be relevant for the progression of Alzheimer disease. We performed a longitudinal study of brain level, activity, and distribution of IDE in transgenic mice (Tg2576) expressing the Swedish mutation in human Abeta precursor protein. At 16 months of age, Tg2576 showed a significant 2-fold increment in IDE protein level as compared with 4.5- and 11-month-old animals. The peak of IDE was in synchrony with the sharp accumulation of sodium dodecyl sulfate-soluble Abeta and massive Abeta deposition into plaques. At this stage, IDE appeared surrounding Abeta fibrillar deposits within glial fibrillar acidic protein-positive astrocytes, suggesting that it was locally overexpressed during the Abeta-mediated inflammation process. When primary astrocytes were exposed to fibrillar Abeta in vitro, IDE protein level increased as compared with control, and this effect was reduced by the addition of U0126, a specific inhibitor of the ERK1/2 mitogen-activated protein kinase cascade. We propose that in Tg2576 mice and in contrast to its behavior in Alzheimer brains, active IDE increases with age around plaques as a component of astrocyte activation as a result of Abeta-triggered inflammation.
Assuntos
Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Córtex Cerebral/metabolismo , Insulisina/biossíntese , Placa Amiloide/metabolismo , Fatores Etários , Doença de Alzheimer/patologia , Animais , Astrócitos/metabolismo , Western Blotting , Modelos Animais de Doenças , Ensaio de Imunoadsorção Enzimática , Processamento de Imagem Assistida por Computador , Imuno-Histoquímica , Camundongos , Camundongos Transgênicos , RNA Mensageiro/análise , Ratos , Ratos Sprague-Dawley , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Amyloid protein deposited in cerebral vessel walls and diffuse plaques of patients with hereditary cerebral hemorrhage with amyloidosis, Dutch type (HCHWA-D), is similar to the 40-42 residues amyloid beta (Abeta) in vessel walls and senile plaques in brains of patients with Alzheimer's disease (AD), Down's syndrome, and familial and sporadic cerebral amyloid angiopathy (CAA). In 1990 we sequenced the amyloid beta-protein precursor (AbetaPP) gene from HCHWA-D patients revealing a single mutation that results in an amino acid substitution, Abeta E22Q. Subsequent identification of additional mutations in the AbetaPP gene in familial AD (FAD) pedigrees revealed that whereas substitutions in the middle of Abeta, residues Abeta21-23, are predominantly vasculotropic, those found amino- or carboxyl-terminal to the Abeta sequence within AbetaPP enhance amyloid parenchymal plaque deposition. Studies of transfected cells showed that substitutions amino- or carboxyl-terminal to Abeta lead to either greater Abeta production or to enhanced secretion of the more hydrophobic thus more fibrillogenic Abeta1-42. Substitutions in the center of Abeta facilitate rapid aggregation and fibrillization, slower clearance across the blood-brain barrier and perivascular drainage to the systemic circulation, possibly higher resistance to proteolysis, and enhanced toxicity towards endothelial and smooth muscle cells. However, most AD patients have no genetic defects in AbetaPP, indicating that other factors may alter Abeta production, conformation, and/or clearance initiating the disease process.
Assuntos
Doença de Alzheimer/genética , Doença de Alzheimer/patologia , Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Encéfalo/metabolismo , Encéfalo/patologia , Variação Genética/genética , Mutação Puntual/genética , Humanos , Países BaixosRESUMO
In order to have more specific tools available to approach amyloidogenesis in Alzheimer's disease (AD), we have produced several polyclonal and monoclonal antibodies that recognize specific sequences of the amyloid beta (Abeta) peptide. Here we present results that demonstrate that our monoclonal antibody EM5 recognizes an internal sequence (residues 11-16) of the Abeta peptide. This strategic localization of the epitope allowed us to employ this antibody, together with two previously reported polyclonal antibodies (EM2 and EM3, specific for AbetaX-40 and AbetaX-42, respectively), in an immunohistochemical study aimed at exploring the differential distribution of longer (AbetaX-40/42) and shorter (Abeta17-X) peptides along the various types of amyloid deposits of AD. This antibody panel was used in six AD brains, on sections from associative neocortex, striatum and cerebellar cortex. Single and double immunostaining revealed specific staining of vascular amyloid deposits and neuritic plaques by EM5 antibody, with high co-localization of EM2. Our results suggest that EM5 antibody recognizes pathogenic forms of Abeta deposits (amyloid angiopathy and neuritic plaques) and reveals the existence of a subset of plaques with a profile similar to vascular deposits. Additionally, our results show that diffuse plaques in AD brains may contain Abeta17-X peptides as its principal component. EM5 may be a useful tool in research both on human and transgenic mice tissue that may aid in the study of molecular heterogeneity of plaques in AD.
Assuntos
Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/imunologia , Anticorpos Monoclonais , Química Encefálica/imunologia , Fragmentos de Peptídeos/imunologia , Placa Amiloide/química , Sequência de Aminoácidos , Peptídeos beta-Amiloides/química , Peptídeos beta-Amiloides/genética , Animais , Especificidade de Anticorpos , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Immunoblotting , Imuno-Histoquímica , Masculino , Camundongos , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/genética , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por MatrizRESUMO
The modern nomenclature of amyloidosis now includes 25 human and 8 animal fibril proteins. To be included in the list, the protein has to be a major fibril protein in extracellular deposits, which have the characteristics of amyloid, including affinity for Congo red with resulting green birefringence. Synthetic fibrils with amyloid properties are best named 'amyloid-like'. With increasing knowledge, however, the borders between different protein aggregates tend to become less sharp.
Assuntos
Amiloide/classificação , Amiloidose/classificação , Humanos , Terminologia como AssuntoRESUMO
Familial Danish dementia is an early onset autosomal dominant neurodegenerative disorder linked to a genetic defect in the BRI2 gene and clinically characterized by dementia and ataxia. Cerebral amyloid and preamyloid deposits of two unrelated molecules (Danish amyloid (ADan) and beta-amyloid (Abeta)), the absence of compact plaques, and neurofibrillary degeneration indistinguishable from that observed in Alzheimer disease (AD) are the main neuropathological features of the disease. Biochemical analysis of extracted amyloid and preamyloid species indicates that as the solubility of the deposits decreases, the heterogeneity and complexity of the extracted peptides exponentially increase. Nonfibrillar deposits were mainly composed of intact ADan-(1-34) and its N-terminally modified (pyroglutamate) counterpart together with Abeta-(1-42) and Abeta-(4-42) in approximately 1:1 mixture. The post-translational modification, glutamate to pyroglutamate, was not present in soluble circulating ADan. In the amyloid fractions, ADan was heavily oligomerized and highly heterogeneous at the N and C terminus, and, when intact, its N terminus was post-translationally modified (pyroglutamate), whereas Abeta was mainly Abeta-(4-42). In all cases, the presence of Abeta-(X-40) was negligible, a surprising finding in view of the prevalence of Abeta40 in vascular deposits observed in sporadic and familial AD, Down syndrome, and normal aging. Whether the presence of the two amyloid subunits is imperative for the disease phenotype or just reflects a conformational mimicry remains to be elucidated; nonetheless, a specific interaction between ADan oligomers and Abeta molecules was demonstrated in vitro by ligand blot analysis using synthetic peptides. The absence of compact plaques in the presence of extensive neuro fibrillar degeneration strongly suggests that compact plaques, fundamental lesions for the diagnosis of AD, are not essential for the mechanism of dementia.
Assuntos
Peptídeos beta-Amiloides/metabolismo , Demência/genética , Demência/metabolismo , Fragmentos de Peptídeos/metabolismo , Adulto , Doença de Alzheimer/metabolismo , Vasos Sanguíneos/metabolismo , Demência/patologia , Dinamarca , Humanos , Immunoblotting , Técnicas Imunoenzimáticas , Masculino , Placa Amiloide/metabolismo , Placa Amiloide/patologiaRESUMO
Protein conformational diseases, including Alzheimer's, Huntington's, and Parkinson's diseases, result from protein misfolding, giving a distinct fibrillar feature termed amyloid. Recent studies show that only the globular (not fibrillar) conformation of amyloid proteins is sufficient to induce cellular pathophysiology. However, the 3D structural conformations of these globular structures, a key missing link in designing effective prevention and treatment, remain undefined as of yet. By using atomic force microscopy, circular dichroism, gel electrophoresis, and electrophysiological recordings, we show here that an array of amyloid molecules, including amyloid-beta(1-40), alpha-synuclein, ABri, ADan, serum amyloid A, and amylin undergo supramolecular conformational change. In reconstituted membranes, they form morphologically compatible ion-channel-like structures and elicit single ion-channel currents. These ion channels would destabilize cellular ionic homeostasis and hence induce cell pathophysiology and degeneration in amyloid diseases.