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1.
Neurobiol Dis ; 159: 105514, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34555537

RESUMO

Synchronized and properly balanced electrical activity of neurons is the basis for the brain's ability to process information, to learn, and to remember. In Alzheimer's disease (AD), which causes cognitive decline in patients, this synchronization and balance is disturbed by the accumulation of neuropathological biomarkers such as amyloid-beta peptide (Aß42). Failure of Aß42 clearance mechanisms as well as desynchronization of crucial neuronal classes such as fast-spiking interneurons (FSN) are root causes for the disruption of the cognition-relevant gamma brain rhythm (30-80 Hz) and consequent cognitive impairment observed in AD. Here we show that recombinant BRICHOS molecular chaperone domains from ProSP-C or Bri2, which interfere with Aß42 aggregation, can rescue the gamma rhythm. We demonstrate that Aß42 progressively decreases gamma oscillation power and rhythmicity, disrupts the inhibition/excitation balance in pyramidal cells, and desynchronizes FSN firing during gamma oscillations in the hippocampal CA3 network of mice. Application of the more efficacious Bri2 BRICHOS chaperone rescued the cellular and neuronal network performance from all ongoing Aß42-induced functional impairments. Collectively, our findings offer critical missing data to explain the importance of FSN for normal network function and underscore the therapeutic potential of Bri2 BRICHOS to rescue the disruption of cognition-relevant brain rhythms in AD.


Assuntos
Potenciais de Ação/efeitos dos fármacos , Proteínas Adaptadoras de Transdução de Sinal/farmacologia , Hipocampo/efeitos dos fármacos , Interneurônios/efeitos dos fármacos , Chaperonas Moleculares/farmacologia , Células Piramidais/efeitos dos fármacos , Potenciais de Ação/fisiologia , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Peptídeos beta-Amiloides , Animais , Modelos Animais de Doenças , Ritmo Gama , Hipocampo/fisiopatologia , Técnicas In Vitro , Interneurônios/fisiologia , Camundongos , Vias Neurais/efeitos dos fármacos , Vias Neurais/fisiopatologia , Fragmentos de Peptídeos , Domínios Proteicos , Proteína C Associada a Surfactante Pulmonar/metabolismo , Proteína C Associada a Surfactante Pulmonar/farmacologia , Células Piramidais/metabolismo , Células Piramidais/fisiologia , Proteínas Recombinantes
2.
Biochem J ; 473(20): 3683-3704, 2016 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-27514716

RESUMO

Formation of fibrils of the amyloid-ß peptide (Aß) is suggested to play a central role in neurodegeneration in Alzheimer's disease (AD), for which no effective treatment exists. The BRICHOS domain is a part of several disease-related proproteins, the most studied ones being Bri2 associated with familial dementia and prosurfactant protein C (proSP-C) associated with lung amyloid. BRICHOS from proSP-C has been found to be an efficient inhibitor of Aß aggregation and toxicity, but its lung-specific expression makes it unsuited to target in AD. Bri2 is expressed in the brain, affects processing of Aß precursor protein, and increased levels of Bri2 are found in AD brain, but the specific role of its BRICHOS domain has not been studied in vivo Here, we find that transgenic expression of the Bri2 BRICHOS domain in the Drosophila central nervous system (CNS) or eyes efficiently inhibits Aß42 toxicity. In the presence of Bri2 BRICHOS, Aß42 is diffusely distributed throughout the mushroom bodies, a brain region involved in learning and memory, whereas Aß42 expressed alone or together with proSP-C BRICHOS forms punctuate deposits outside the mushroom bodies. Recombinant Bri2 BRICHOS domain efficiently prevents Aß42-induced reduction in γ-oscillations in hippocampal slices. Finally, Bri2 BRICHOS inhibits several steps in the Aß42 fibrillation pathway and prevents aggregation of heat-denatured proteins, indicating that it is a more versatile chaperone than proSP-C BRICHOS. These findings suggest that Bri2 BRICHOS can be a physiologically relevant chaperone for Aß in the CNS and needs to be further investigated for its potential in AD treatment.


Assuntos
Peptídeos beta-Amiloides/metabolismo , Demência/metabolismo , Proteínas de Drosophila/metabolismo , Chaperonas Moleculares/metabolismo , Animais , Encéfalo/metabolismo , Encéfalo/ultraestrutura , Sistema Nervoso Central/metabolismo , Drosophila , Eletrofisiologia , Feminino , Hipocampo/metabolismo , Hipocampo/ultraestrutura , Humanos , Imuno-Histoquímica , Técnicas In Vitro , Cinética , Locomoção/genética , Locomoção/fisiologia , Masculino , Camundongos , Microscopia Eletrônica de Transmissão , Reação em Cadeia da Polimerase em Tempo Real
3.
Nat Struct Mol Biol ; 22(3): 207-213, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25686087

RESUMO

Alzheimer's disease is an increasingly prevalent neurodegenerative disorder whose pathogenesis has been associated with aggregation of the amyloid-ß peptide (Aß42). Recent studies have revealed that once Aß42 fibrils are generated, their surfaces effectively catalyze the formation of neurotoxic oligomers. Here we show that a molecular chaperone, a human Brichos domain, can specifically inhibit this catalytic cycle and limit human Aß42 toxicity. We demonstrate in vitro that Brichos achieves this inhibition by binding to the surfaces of fibrils, thereby redirecting the aggregation reaction to a pathway that involves minimal formation of toxic oligomeric intermediates. We verify that this mechanism occurs in living mouse brain tissue by cytotoxicity and electrophysiology experiments. These results reveal that molecular chaperones can help maintain protein homeostasis by selectively suppressing critical microscopic steps within the complex reaction pathways responsible for the toxic effects of protein misfolding and aggregation.


Assuntos
Peptídeos beta-Amiloides/metabolismo , Chaperonas Moleculares/fisiologia , Agregação Patológica de Proteínas , Doença de Alzheimer/metabolismo , Animais , Microscopia Crioeletrônica , Eletrofisiologia , Feminino , Hipocampo/metabolismo , Hipocampo/fisiologia , Humanos , Cinética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Chaperonas Moleculares/química , Chaperonas Moleculares/metabolismo , Dobramento de Proteína , Estrutura Terciária de Proteína
4.
J Neurosci ; 34(34): 11416-25, 2014 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-25143621

RESUMO

The amyloid-ß hypothesis of Alzheimer's Disease (AD) focuses on accumulation of amyloid-ß peptide (Aß) as the main culprit for the myriad physiological changes seen during development and progression of AD including desynchronization of neuronal action potentials, consequent development of aberrant brain rhythms relevant for cognition, and final emergence of cognitive deficits. The aim of this study was to elucidate the cellular and synaptic mechanisms underlying the Aß-induced degradation of gamma oscillations in AD, to identify aggregation state(s) of Aß that mediate the peptides neurotoxicity, and to test ways to prevent the neurotoxic Aß effect. We show that Aß(1-42) in physiological concentrations acutely degrades mouse hippocampal gamma oscillations in a concentration- and time-dependent manner. The underlying cause is an Aß-induced desynchronization of action potential generation in pyramidal cells and a shift of the excitatory/inhibitory equilibrium in the hippocampal network. Using purified preparations containing different aggregation states of Aß, as well as a designed ligand and a BRICHOS chaperone domain, we provide evidence that the severity of Aß neurotoxicity increases with increasing concentration of fibrillar over monomeric Aß forms, and that Aß-induced degradation of gamma oscillations and excitatory/inhibitory equilibrium is prevented by compounds that interfere with Aß aggregation. Our study provides correlative evidence for a link between Aß-induced effects on synaptic currents and AD-relevant neuronal network oscillations, identifies the responsible aggregation state of Aß and proofs that strategies preventing peptide aggregation are able to prevent the deleterious action of Aß on the excitatory/inhibitory equilibrium and on the gamma rhythm.


Assuntos
Potenciais de Ação/efeitos dos fármacos , Peptídeos beta-Amiloides/farmacologia , Relógios Biológicos/efeitos dos fármacos , Região CA3 Hipocampal/citologia , Neurônios/efeitos dos fármacos , Fragmentos de Peptídeos/farmacologia , Agregados Proteicos/efeitos dos fármacos , Peptídeos beta-Amiloides/química , Peptídeos beta-Amiloides/metabolismo , Peptídeos beta-Amiloides/ultraestrutura , Animais , Região CA3 Hipocampal/fisiologia , Agonistas de Aminoácidos Excitatórios/farmacologia , Feminino , Técnicas In Vitro , Ácido Caínico/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Rede Nervosa/efeitos dos fármacos , Rede Nervosa/fisiologia , Técnicas de Patch-Clamp , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/metabolismo , Fragmentos de Peptídeos/ultraestrutura , Conformação Proteica/efeitos dos fármacos , Análise Espectral , Transmissão Sináptica/efeitos dos fármacos , Fatores de Tempo
5.
Org Biomol Chem ; 12(34): 6684-93, 2014 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-25030615

RESUMO

Peptide-like compounds containing an arginine have been shown to bind and stabilize the central helix of the Alzheimer's disease related amyloid-ß peptide (Aß) in an α-helical conformation, thereby delaying its aggregation into cytotoxic species. Here we study a novel Aß targeting ligand AEDabDab containing the triamino acid, N(γ)-(2-aminoethyl)-2,4-diaminobutanoic (AEDab) acid. The new AEDab triamino acid carries an extra positive charge in the side chain and is designed to be incorporated into a ligand AEDabDab where the AEDab replaces an arginine moiety in a previously developed ligand Pep1b. This is done in order to increase the Aß-ligand interaction, and molecular dynamics (MD) simulation of the stability of the Aß central helix in the presence of the AEDabDab ligand shows further stabilization of the helical conformation of Aß compared to the previously reported Pep1b as well as compared to the AEOrnDab ligand containing an N(δ)-(2-aminoethyl)-2,5-diaminopentanoic acid unit which has an additional methylene group. To evaluate the effect of the AEDabDab ligand on the Aß neurotoxicity the AEDab triamino acid building block is synthesized by reductive alkylation of N-protected-glycinal with α-amino-protected diaminobutanoic acid, and the Aß targeting ligand AEDabDab is prepared by solid-phase synthesis starting with attachment of glutarate to the Wang support. Replacement of the arginine residue by the AEDab triamino acid resulted in an improved capability of the ligand to prevent the Aß1-42 induced reduction of gamma (γ) oscillations in hippocampal slice preparation.


Assuntos
Aminobutiratos/síntese química , Peptídeos beta-Amiloides/química , Ritmo Gama/efeitos dos fármacos , Hipocampo/efeitos dos fármacos , Fragmentos de Peptídeos/química , Agregação Patológica de Proteínas/prevenção & controle , Aminobutiratos/química , Aminobutiratos/farmacologia , Peptídeos beta-Amiloides/antagonistas & inibidores , Peptídeos beta-Amiloides/toxicidade , Animais , Arginina/química , Ritmo Gama/fisiologia , Hipocampo/fisiologia , Ácido Caínico/farmacologia , Ligantes , Camundongos , Camundongos Endogâmicos C57BL , Simulação de Dinâmica Molecular , Fragmentos de Peptídeos/antagonistas & inibidores , Fragmentos de Peptídeos/toxicidade , Ligação Proteica , Estabilidade Proteica/efeitos dos fármacos , Estrutura Secundária de Proteína , Técnicas de Cultura de Tecidos
6.
J Neurosci ; 32(26): 8767-77, 2012 Jun 27.
Artigo em Inglês | MEDLINE | ID: mdl-22745479

RESUMO

Alzheimer's disease (AD) is the major cause of dementia. During the development of AD, neurofibrillary tangles progress in a fixed pattern, starting in the transentorhinal cortex followed by the hippocampus and cortical areas. In contrast, the deposition of ß-amyloid (Aß) plaques, which are the other histological hallmark of AD, does not follow the same strict spatiotemporal pattern, and it correlates poorly with cognitive decline. Instead, soluble Aß oligomers have received increasing attention as probable inducers of pathogenesis. In this study, we use microinjections into electrophysiologically defined primary hippocampal rat neurons to demonstrate the direct neuron-to-neuron transfer of soluble oligomeric Aß. Additional studies conducted in a human donor-acceptor cell model show that this Aß transfer depends on direct cellular connections. As the transferred oligomers accumulate, acceptor cells gradually show beading of tubulin, a sign of neurite damage, and gradual endosomal leakage, a sign of cytotoxicity. These observations support that intracellular Aß oligomers play a role in neurodegeneration, and they explain the manner in which Aß can drive disease progression, even if the extracellular plaque load is poorly correlated with the degree of cognitive decline. Understanding this phenomenon sheds light on the pathophysiological mechanism of AD progression. Additional elucidation will help uncover the detailed mechanisms responsible for the manner in which AD progresses via anatomical connections and will facilitate the development of new strategies for stopping the progression of this incapacitating disease.


Assuntos
Peptídeos beta-Amiloides/metabolismo , Peptídeos beta-Amiloides/toxicidade , Comunicação Celular/fisiologia , Degeneração Neural/induzido quimicamente , Degeneração Neural/patologia , Neurônios/metabolismo , Fragmentos de Peptídeos/metabolismo , Fragmentos de Peptídeos/toxicidade , Transmissão Sináptica/fisiologia , Animais , Animais Recém-Nascidos , Comunicação Celular/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Células Cultivadas , Técnicas de Cocultura , Dendritos/metabolismo , Relação Dose-Resposta a Droga , Endocitose/efeitos dos fármacos , Endocitose/fisiologia , Exocitose/efeitos dos fármacos , Exocitose/fisiologia , Feminino , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Compostos Heterocíclicos com 3 Anéis/administração & dosagem , Compostos Heterocíclicos com 3 Anéis/metabolismo , Hipocampo/citologia , Humanos , Proteína 2 de Membrana Associada ao Lisossomo/metabolismo , Masculino , Glicoproteínas de Membrana/metabolismo , Microinjeções , Microscopia Eletrônica de Transmissão , Neocórtex/citologia , Proteínas do Tecido Nervoso/metabolismo , Neuroblastoma/patologia , Neuroglia/efeitos dos fármacos , Neuroglia/metabolismo , Neurônios/efeitos dos fármacos , Neurônios/ultraestrutura , Técnicas de Patch-Clamp , Ratos , Ratos Sprague-Dawley , Rodaminas , Transmissão Sináptica/efeitos dos fármacos , Sais de Tetrazólio , Tiazóis , Fatores de Tempo , Transfecção , Proteínas rab5 de Ligação ao GTP/metabolismo
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