RESUMEN
Despite the well-accepted role of the two main neuropathological markers (ß-amyloid and tau) in the progression of Alzheimer's disease, the interaction and specific contribution of each of them is not fully elucidated. To address this question, in the present study, an adeno-associated virus (AAV9) carrying the mutant P301L form of human tau, was injected into the dorsal hippocampi of APP/PS1 transgenic mice or wild type mice (WT). Three months after injections, memory tasks, biochemical and immunohistochemical analysis were performed. We found that the overexpression of hTauP301L accelerates memory deficits in APP/PS1 mice, but it did not affect memory function of WT mice. Likewise, biochemical assays showed that only in the case of APP/PS1-hTauP301L injected mice, an important accumulation of tau was observed in the insoluble urea fraction. Similarly, electron microscopy images revealed that numerous clusters of tau immunoparticles appear at the dendrites of APP/PS1 injected mice and not in WT animals, suggesting that the presence of amyloid is necessary to induce tau aggregation. Interestingly, these tau immunoparticles accumulate in dendritic mitochondria in the APP/PS1 mice, whereas most of mitochondria in WT injected mice remain free of tau immunoparticles. Taken together, it seems that amyloid induces tau aggregation and accumulation in the dendritic mitochondria and subsequently may alter synapse function, thus, contributing to accelerate cognitive decline in APP/PS1 mice.
Asunto(s)
Enfermedad de Alzheimer/complicaciones , Péptidos beta-Amiloides/efectos adversos , Trastornos del Conocimiento/patología , Modelos Animales de Enfermedad , Mitocondrias/patología , Proteínas tau/metabolismo , Precursor de Proteína beta-Amiloide/fisiología , Animales , Trastornos del Conocimiento/etiología , Trastornos del Conocimiento/metabolismo , Femenino , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Mitocondrias/metabolismo , Fosforilación , Presenilina-1/fisiología , Sinapsis , Proteínas tau/genéticaRESUMEN
Elevated amyloid precursor protein (APP) expression in the choroid plexus suggests an important role for extracellular APP metabolites such as sAPPα in cerebrospinal fluid. Despite widespread App brain expression, we hypothesized that specifically targeting choroid plexus expression could alter animal physiology. Through various genetic and viral approaches in the adult mouse, we show that choroid plexus APP levels significantly impact proliferation in both subventricular zone and hippocampus dentate gyrus neurogenic niches. Given the role of Aß peptides in Alzheimer disease pathogenesis, we also tested whether favoring the production of Aß in choroid plexus could negatively affect niche functions. After AAV5-mediated long-term expression of human mutated APP specifically in the choroid plexus of adult wild-type mice, we observe reduced niche proliferation, reduced hippocampus APP expression, behavioral defects in reversal learning, and deficits in hippocampal long-term potentiation. Our findings highlight the unique role played by the choroid plexus in regulating brain function and suggest that targeting APP in choroid plexus may provide a means to improve hippocampus function and alleviate disease-related burdens.
Asunto(s)
Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Plexo Coroideo/metabolismo , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/fisiopatología , Péptidos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/fisiología , Animales , Conducta Animal , Encéfalo/metabolismo , Proliferación Celular , Modelos Animales de Enfermedad , Hipocampo/metabolismo , Potenciación a Largo Plazo , Masculino , Ratones , Ratones Endogámicos C57BLRESUMEN
The prevailing opinion is that prefibrillar ß-amyloid (Aß) species, rather than end-stage amyloid fibrils, cause neuronal dysfunction in Alzheimer's disease, although the mechanisms behind Aß neurotoxicity remain to be elucidated. Luminescent conjugated oligothiophenes (LCOs) exhibit spectral properties upon binding to amyloid proteins and have previously been reported to change the toxicity of Aß1-42 and prion protein. In a previous study, we showed that an LCO, pentamer formyl thiophene acetic acid (p-FTAA), changed the toxicity of Aß1-42. Here we investigated whether an LCO, heptamer formyl thiophene acetic acid (h-FTAA), could change the toxicity of Aß1-42 by comparing its behavior with that of p-FTAA. Moreover, we investigated the effects on toxicity when Aß with the Arctic mutation (AßArc) was aggregated with both LCOs. Cell viability assays on SH-SY5Y neuroblastoma cells demonstrated that h-FTAA has a stronger impact on Aß1-42 toxicity than does p-FTAA. Interestingly, h-FTAA, but not p-FTAA, rescued the AßArc-mediated toxicity. Aggregation kinetics and binding assay experiments with Aß1-42 and AßArc when aggregated with both LCOs showed that h-FTAA and p-FTAA either interact with different species or affect the aggregation in different ways. In conclusion, h-FTAA protects against Aß1-42 and AßArc toxicity, thus showing h-FTAA to be a useful tool for improving our understanding of the process of Aß aggregation linked to cytotoxicity.
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Acetatos/química , Precursor de Proteína beta-Amiloide/metabolismo , Tiofenos/química , Acetatos/metabolismo , Amiloide/química , Péptidos beta-Amiloides/química , Precursor de Proteína beta-Amiloide/fisiología , Precursor de Proteína beta-Amiloide/toxicidad , Proteínas Amiloidogénicas/química , Colorantes Fluorescentes/química , Humanos , Cinética , Luminiscencia , Fragmentos de Péptidos/metabolismo , Agregado de Proteínas/efectos de los fármacos , Agregado de Proteínas/fisiología , Coloración y Etiquetado/métodos , Tiofenos/metabolismoRESUMEN
Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive cognitive impairment. It is hypothesized to develop due to the dysfunction of two major proteins, amyloid-ß (Aß) and microtubule-associated protein, tau. Evidence supports the involvement of cholesterol changes in both the generation and deposition of Aß. This study was performed to better understand the role of liver cholesterol and bile acid metabolism in the pathophysiology of AD. We used male and female wild-type control (C57BL/6J) mice to compare to two well-characterized amyloidosis models of AD, APP/PS1, and AppNL-G-F. Both conjugated and unconjugated primary and secondary bile acids were quantified using UPLC-MS/MS from livers of control and AD mice. We also measured cholesterol and its metabolites and identified changes in levels of proteins associated with bile acid synthesis and signaling. We observed sex differences in liver cholesterol levels accompanied by differences in levels of synthesis intermediates and conjugated and unconjugated liver primary bile acids in both APP/PS1 and AppNL-G-F mice when compared to controls. Our data revealed fundamental deficiencies in cholesterol metabolism and bile acid synthesis in the livers of two different AD mouse lines. These findings strengthen the involvement of liver metabolism in the pathophysiology of AD.
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Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/patología , Precursor de Proteína beta-Amiloide/fisiología , Ácidos y Sales Biliares/metabolismo , Modelos Animales de Enfermedad , Hígado/metabolismo , Presenilina-1/fisiología , Animales , Femenino , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones NoqueadosRESUMEN
Amyloid ß peptide (Aß) is the major pathogenic molecule in Alzheimer's disease (AD). BACE1 enzyme is essential for the generation of Aß. Deficiency of p38α-MAPK in neurons increases lysosomal degradation of BACE1 and decreases Aß deposition in the brain of APP-transgenic mice. However, the mechanisms mediating effects of p38α-MAPK are largely unknown. In this study, we used APP-transgenic mice and cultured neurons and observed that deletion of p38α-MAPK specifically in neurons decreased phosphorylation of Snapin at serine, increased retrograde transportation of BACE1 in axons and reduced BACE1 at synaptic terminals, which suggests that p38α-MAPK deficiency promotes axonal transportation of BACE1 from its predominant locations, axonal terminals, to lysosomes in the cell body. In vitro kinase assay revealed that p38α-MAPK directly phosphorylates Snapin. By further performing mass spectrometry analysis and site-directed mutagenic experiments in SH-SY5Y cell lines, we identified serine residue 112 as a p38α-MAPK-phosphorylating site on Snapin. Replacement of serine 112 with alanine did abolish p38α-MAPK knockdown-induced reduction of BACE1 activity and protein level, and transportation to lysosomes in SH-SY5Y cells. Taken together, our study suggests that activation of p38α-MAPK phosphorylates Snapin and inhibits the retrograde transportation of BACE1 in axons, which might exaggerate amyloid pathology in AD brain.
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Secretasas de la Proteína Precursora del Amiloide/metabolismo , Precursor de Proteína beta-Amiloide/fisiología , Ácido Aspártico Endopeptidasas/metabolismo , Proteína Quinasa 14 Activada por Mitógenos/metabolismo , Presenilina-1/fisiología , Terminales Presinápticos/metabolismo , Proteínas de Transporte Vesicular/metabolismo , Secretasas de la Proteína Precursora del Amiloide/genética , Animales , Ácido Aspártico Endopeptidasas/genética , Transporte Axonal , Modelos Animales de Enfermedad , Humanos , Ratones , Ratones Transgénicos , Proteína Quinasa 14 Activada por Mitógenos/genética , Neuronas/citología , Neuronas/metabolismo , Proteínas de Transporte Vesicular/genéticaRESUMEN
Alzheimer's disease (AD) is a complicated neurodegenerative disease and therefore addressing multiple targets simultaneously has been believed as a promising therapeutic strategy against AD. α7 nicotinic acetylcholine receptor (nAChR), which plays an important role in improving cognitive function and alleviating neuroinflammation in central nervous system (CNS), has been regarded as a potential target in the treatment of AD. However, the regulation of α7 nAChR at post-transcriptional level in mammalian brain remains largely speculated. Herein, we uncovered a novel post-transcriptional regulatory mechanism of α7 nAChR expression in AD and further demonstrated that miR-98-5p suppressed α7 nAChR expression through directly binding to the 3'UTR of mRNA. Knockdown of miR-98-5p activated Ca2+ signaling pathway and consequently reversed cognitive deficits and Aß burden in APP/PS1 mice. Furthermore, miR-98-5p downregulation increased α7 nAChR expression, and ameliorated neuroinflammation via inhibiting NF-κB pathway and upregulating Nrf2 target genes. Our findings illustrate a prominent regulatory role of miR-98-5p in targeting inflammation and cognition, and provide an insight into the potential of miR-98-5p/α7 nAChR axis as a novel therapeutic strategy for AD.
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Enfermedad de Alzheimer/complicaciones , Disfunción Cognitiva/patología , MicroARNs/genética , Enfermedades Neurodegenerativas/patología , Procesamiento Postranscripcional del ARN , Receptor Nicotínico de Acetilcolina alfa 7/genética , Precursor de Proteína beta-Amiloide/fisiología , Animales , Disfunción Cognitiva/etiología , Disfunción Cognitiva/metabolismo , Modelos Animales de Enfermedad , Regulación de la Expresión Génica , Humanos , Masculino , Ratones , Ratones Transgénicos , Enfermedades Neurodegenerativas/etiología , Enfermedades Neurodegenerativas/metabolismo , Presenilina-1/fisiología , Receptor Nicotínico de Acetilcolina alfa 7/metabolismoRESUMEN
Mitochondrial Tu translation elongation factor (TUFM or EF-Tu) is part of the mitochondrial translation machinery. It is reported that TUFM expression is reduced in the brain of Alzheimer's disease (AD), suggesting that TUFM might play a role in the pathophysiology. In this study, we found that TUFM protein level was decreased in the hippocampus and cortex especially in the aged APP/PS1 mice, an animal model of AD. In HEK cells that stably express full-length human amyloid-ß precursor protein (HEK-APP), TUFM knockdown or overexpression increased or reduced the protein levels of ß-amyloid protein (Aß) and ß-amyloid converting enzyme 1 (BACE1), respectively. TUFM-mediated reduction of BACE1 was attenuated by translation inhibitor cycloheximide (CHX) or α-[2-[4-(3,4-Dichlorophenyl)-2-thiazolyl]hydrazinylidene]-2-nitro-benzenepropanoic acid (4EGI1), and in cells overexpressing BACE1 constructs deleting the 5' untranslated region (5'UTR). TUFM silencing increased the half-life of BACE1 mRNA, suggesting that RNA stability was affected by TUFM. In support, transcription inhibitor Actinomycin D (ActD) and silencing of nuclear factor κB (NFκB) failed to abolish TUFM-mediated regulation of BACE1 protein and mRNA. We further found that the mitochondria-targeted antioxidant TEMPO diminished the effects of TUFM on BACE1, suggesting that reactive oxygen species (ROS) played an important role. Indeed, cellular ROS levels were affected by TUFM knockdown or overexpression, and TUFM-mediated regulation of apoptosis and Tau phosphorylation at selective sites was attenuated by TEMPO. Collectively, TUFM protein levels were decreased in APP/PS1 mice. TUFM is involved in AD pathology by regulating BACE1 translation, apoptosis, and Tau phosphorylation, in which ROS plays an important role.
Asunto(s)
Enfermedad de Alzheimer/patología , Secretasas de la Proteína Precursora del Amiloide/metabolismo , Modelos Animales de Enfermedad , Mitocondrias/patología , Factor Tu de Elongación Peptídica/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/metabolismo , Secretasas de la Proteína Precursora del Amiloide/genética , Precursor de Proteína beta-Amiloide/fisiología , Animales , Humanos , Ratones , Ratones Transgénicos , Mitocondrias/metabolismo , Factor Tu de Elongación Peptídica/genética , Fosforilación , Presenilina-1/fisiologíaRESUMEN
Transgenic mouse models of Aß amyloidosis generated by knock-in of a humanized Aß sequence can offer some advantages over the transgenic models that overexpress amyloid precursor protein (APP). However, systematic comparison of memory, behavioral, and neuropathological phenotypes between these models has not been well documented. In this study, we compared memory and affective behavior in APPNLGF mice, an APP knock-in model, to two widely used mouse models of Alzheimer's disease, 5xFAD and APP/PS1 mice, at 10 months of age. We found that, despite similar deficits in working memory, object recognition, and social recognition memory, APPNLGF and 5xFAD mice but not APP/PS1 mice show compelling anxiety- and depressive-like behavior, and exhibited a marked impairment of social interaction. We quantified corticolimbic Aß plaques, which were lowest in APPNLGF, intermediate in APP/PS1, and highest in 5xFAD mice. Interestingly, analysis of plaque size revealed that plaques were largest in APP/PS1 mice, intermediate in 5xFAD mice, and smallest in APPNLGF mice. Finally, we observed a significantly higher percentage of the area occupied by plaques in both 5xFAD and APP/PS1 relative to APPNLGF mice. Overall, our findings suggest that the severity of Aß neuropathology is not directly correlated with memory and affective behavior impairments between these three transgenic mouse models. Additionally, APPNLGF may represent a valid mouse model for studying AD comorbid with anxiety and depression.
Asunto(s)
Afecto , Precursor de Proteína beta-Amiloide/genética , Encéfalo/patología , Memoria , Oligopéptidos/genética , Precursor de Proteína beta-Amiloide/metabolismo , Precursor de Proteína beta-Amiloide/fisiología , Animales , Femenino , Locomoción , Masculino , Memoria a Corto Plazo , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Prueba del Laberinto Acuático de Morris , Oligopéptidos/metabolismo , Oligopéptidos/fisiología , Prueba de Campo Abierto , Interacción SocialRESUMEN
Rationale: Delivery of therapeutic agents to the brain is limited by the presence of the blood-brain barrier (BBB). An emerging strategy to temporarily and locally increase the permeability of the BBB is the use of transcranial focused ultrasound (FUS) and systematically injected microbubbles (MBs). FUS+MB BBB treatments cause an acute inflammatory response, marked by a transient upregulation of pro-inflammatory genes; however, the cellular immune response remains unknown. Methods: FUS+MB BBB treatments were monitored in real-time using two-photon fluorescence microscopy and transgenic EGFP Wistar rats, which harbour several fluorescent cell types. Leukocyte identification and counts were confirmed using magnetic resonance imaging-guided FUS+MB BBB treatments. Participation of leukocytes in reducing ß-amyloid pathology following repeated FUS+MB BBB treatments was investigated in the TgCRND8 mouse model of Alzheimer's disease. Results: Intravascular leukocyte activity indicative of acute inflammation were identified, including transendothelial migration, formation of cell aggregates, and cell masses capable of perturbing blood flow. Leukocyte responses were only observed after the onset of sonication. Neutrophils were identified to be a key participating leukocyte. Significantly more neutrophils were detected in the sonicated hemisphere compared to the contralateral hemisphere, and to untreated controls. Three to five biweekly FUS+MB BBB treatments did not induce significantly more neutrophil recruitment, nor neutrophil phagocytosis of ß-amyloid plaques, in TgCRND8 mice compared to untreated controls. Conclusions: This study provides evidence that the cellular aspect of the peripheral immune response triggered by FUS+MB BBB treatments begins immediately after sonication, and emphasizes the importance for further investigations to be conducted to understand leukocyte dynamics and cerebral blood flow responses to FUS+MB BBB treatments.
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Enfermedad de Alzheimer/inmunología , Barrera Hematoencefálica/metabolismo , Permeabilidad Capilar , Leucocitos/inmunología , Microburbujas , Infiltración Neutrófila/inmunología , Sonicación/métodos , Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/patología , Enfermedad de Alzheimer/radioterapia , Precursor de Proteína beta-Amiloide/fisiología , Animales , Transporte Biológico , Barrera Hematoencefálica/efectos de la radiación , Femenino , Proteínas Fluorescentes Verdes , Inflamación/inmunología , Inflamación/metabolismo , Inflamación/patología , Inflamación/radioterapia , Masculino , Ratones , Ratones Transgénicos , Placa Amiloide/patología , Ratas , Ratas WistarRESUMEN
The accumulation of amyloid-ß (Aß) is a characteristic event in the pathogenesis of Alzheimer's disease (AD). Aquaporin 1 (AQP1) is a membrane water channel protein belonging to the AQP family. AQP1 levels are elevated in the cerebral cortex during the early stages of AD, but the role of AQP1 in AD pathogenesis is unclear. We first determined the expression and distribution of AQP1 in brain tissue samples of AD patients and two AD mouse models (3xTg-AD and 5xFAD). AQP1 accumulation was observed in vulnerable neurons in the cerebral cortex of AD patients, and in neurons affected by the Aß or tau pathology in the 3xTg-AD and 5xFAD mice. AQP1 levels increased in neurons as aging progressed in the AD mouse models. Stress stimuli increased AQP1 in primary cortical neurons. In response to cellular stress, AQP1 appeared to translocate to endocytic compartments of ß- and γ-secretase activities. Ectopic expression of AQP1 in human neuroblastoma cells overexpressing amyloid precussir protein (APP) with the Swedish mutations reduced ß-secretase (BACE1)-mediated cleavage of APP and reduced Aß production without altering the nonamyloidogenic pathway. Conversely, knockdown of AQP1 enhanced BACE1 activity and Aß production. Immunoprecipitation experiments showed that AQP1 decreased the association of BACE1 with APP. Analysis of a human database showed that the amount of Aß decreases as the expression of AQP1 increases. These results suggest that the upregulation of AQP1 is an adaptive response of neurons to stress that reduces Aß production by inhibiting the binding between BACE1 and APP.
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Secretasas de la Proteína Precursora del Amiloide/fisiología , Precursor de Proteína beta-Amiloide/fisiología , Amiloide/biosíntesis , Acuaporina 1/fisiología , Enfermedad de Alzheimer/metabolismo , Animales , Acuaporina 1/metabolismo , Modelos Animales de Enfermedad , Humanos , Ratones , Neuronas/metabolismoRESUMEN
Amyloid beta (Aß) is a major component of amyloid plaques, which are a key pathological hallmark found in the brains of Alzheimer's disease (AD) patients. We show that statins are effective at reducing Aß in human neurons from nondemented control subjects, as well as subjects with familial AD and sporadic AD. Aß is derived from amyloid precursor protein (APP) through sequential proteolytic cleavage by BACE1 and γ-secretase. While previous studies have shown that cholesterol metabolism regulates APP processing to Aß, the mechanism is not well understood. We used iPSC-derived neurons and bimolecular fluorescence complementation assays in transfected cells to elucidate how altering cholesterol metabolism influences APP processing. Altering cholesterol metabolism using statins decreased the generation of sAPPß and increased levels of full-length APP (flAPP), indicative of reduced processing of APP by BACE1. We further show that statins decrease flAPP interaction with BACE1 and enhance APP dimerization. Additionally, statin-induced changes in APP dimerization and APP-BACE1 are dependent on cholesterol binding to APP. Our data indicate that statins reduce Aß production by decreasing BACE1 interaction with flAPP and suggest that this process may be regulated through competition between APP dimerization and APP cholesterol binding.
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Precursor de Proteína beta-Amiloide/metabolismo , Inhibidores de Hidroximetilglutaril-CoA Reductasas/farmacología , Neuronas/metabolismo , Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/patología , Secretasas de la Proteína Precursora del Amiloide/metabolismo , Péptidos beta-Amiloides/metabolismo , Péptidos beta-Amiloides/fisiología , Precursor de Proteína beta-Amiloide/efectos de los fármacos , Precursor de Proteína beta-Amiloide/fisiología , Ácido Aspártico Endopeptidasas/metabolismo , Colesterol/metabolismo , Dimerización , Células HEK293 , Humanos , Inhibidores de Hidroximetilglutaril-CoA Reductasas/metabolismo , Células Madre Pluripotentes Inducidas/metabolismo , Neuronas/efectos de los fármacos , Neuronas/fisiología , Unión ProteicaRESUMEN
INTRODUCTION: Microglial TYROBP (DAP12) is a network hub and driver in sporadic late-onset Alzheimer's disease (AD). TYROBP is a cytoplasmic adaptor for TREM2 and other receptors, but little is known about its roles and actions in AD. Herein, we demonstrate that endogenous Tyrobp transcription is specifically increased in recruited microglia. METHODS: Using a novel transgenic mouse overexpressing TYROBP in microglia, we observed a decrease of the amyloid burden and an increase of TAU phosphorylation stoichiometry when crossed with APP/PSEN1 or MAPTP301S mice, respectively. Characterization of these mice revealed Tyrobp-related modulation of apolipoprotein E (Apoe) transcription. We also showed that Tyrobp and Apoe mRNAs were increased in Trem2-null microglia recruited around either amyloid beta deposits or a cortical stab injury. Conversely, microglial Apoe transcription was dramatically diminished when Tyrobp was absent. CONCLUSIONS: Our results provide evidence that TYROBP-APOE signaling does not require TREM2 and could be an initiating step in establishment of the disease-associated microglia (DAM) phenotype.
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Proteínas Adaptadoras Transductoras de Señales/genética , Enfermedad de Alzheimer/metabolismo , Apolipoproteínas E/genética , Glicoproteínas de Membrana/genética , Ratones Transgénicos , Microglía/metabolismo , Receptores Inmunológicos/genética , Enfermedad de Alzheimer/genética , Precursor de Proteína beta-Amiloide/fisiología , Amiloidosis/prevención & control , Animales , Encéfalo/metabolismo , Encéfalo/patología , Modelos Animales de Enfermedad , Humanos , Ratones , Ratones Noqueados , Fosforilación , Presenilina-1/fisiología , Transducción de Señal , Proteínas tau/metabolismoRESUMEN
The amyloid precursor protein (APP) is a structurally and functionally conserved transmembrane protein whose physiological role in adult brain function and health is still unclear. Because mutations in APP cause familial Alzheimer's disease (fAD), most research focuses on this aspect of APP biology. We investigated the physiological function of APP in the adult brain using the fruit fly Drosophila melanogaster, which harbors a single APP homologue called APP Like (APPL). Previous studies have provided evidence for the implication of APPL in neuronal wiring and axonal growth through the Wnt signaling pathway during development. However, like APP, APPL continues to be expressed in all neurons of the adult brain where its functions and their molecular and cellular underpinnings are unknown. We report that APPL loss of function (LOF) results in the dysregulation of endolysosomal function in neurons, with a notable enlargement of early endosomal compartments followed by neuronal cell death and the accumulation of dead neurons in the brain during a critical period at a young age. These defects can be rescued by reduction in the levels of the early endosomal regulator Rab5, indicating a causal role of endosomal function for cell death. Finally, we show that the secreted extracellular domain of APPL interacts with glia and regulates the size of their endosomes, the expression of the Draper engulfment receptor, and the clearance of neuronal debris in an axotomy model. We propose that APP proteins represent a novel family of neuroglial signaling factors required for adult brain homeostasis.
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Precursor de Proteína beta-Amiloide/metabolismo , Proteínas de Drosophila/genética , Endosomas/metabolismo , Proteínas de la Membrana/genética , Proteínas del Tejido Nervioso/genética , Enfermedad de Alzheimer/genética , Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/fisiología , Animales , Encéfalo/metabolismo , Proteínas Portadoras/metabolismo , Muerte Celular , Supervivencia Celular , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Mutación con Pérdida de Función/genética , Proteínas de la Membrana/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Neuroglía/metabolismo , Neuronas/metabolismo , Transducción de Señal/fisiologíaRESUMEN
The physiological and pathological roles of nascent amyloid beta (Aß) monomers are still debated in the literature. Their involvement in the pathological route of Alzheimer's Disease (AD) is currently considered to be the most relevant, triggered by their aggregation into structured oligomers, a toxic species. Recently, it has been suggested that nascent Aß, out of the amyloidogenic pathway, plays a physiological and protective role, especially in the brain. In this emerging perspective, the study presented in this paper investigated whether the organization of model membranes is affected by contact with Aß in the nascent state, as monomers. The outcome is that, notably, the rules of engagement and the resulting structural outcome are dictated by the composition and properties of the membrane, rather than by the Aß variant. Interestingly, Aß monomers are observed to favor the tightening of adjacent complex membranes, thereby affecting a basic structural event for cell-cell adhesion and cell motility.
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Péptidos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Membranas/metabolismo , Enfermedad de Alzheimer/metabolismo , Péptidos beta-Amiloides/fisiología , Precursor de Proteína beta-Amiloide/fisiología , Humanos , Membranas/fisiología , Modelos Biológicos , Fragmentos de Péptidos/metabolismo , Unión ProteicaRESUMEN
The amyloid precursor protein (APP) intracellular domain (AICD) is a metabolic by-product of APP produced through sequential proteolytic cleavage by α-, ß-, and γ-secretases. The interaction between AICD and Fe65 has been reported to impair adult neurogenesis in vivo. However, the exact role of AICD in mediating neural stem cell fate remains unclear. To identify the role of AICD in neuronal proliferation and differentiation, as well as to clarify the molecular mechanisms underlying the role of AICD in neurogenesis, we first generated a mouse model expressing the Rosa26-based AICD transgene. AICD overexpression did not alter the spatiotemporal expression pattern of full-length APP or accumulation of its metabolites. In addition, AICD decreased the newly generated neural progenitor cell (NPC) pool, inhibited the proliferation and differentiation efficiency of NPCs, and increased cell death both in vitro and in vivo. Given that abnormal neurogenesis is often associated with depression-like behavior in adult mice, we conducted a forced swim test and tail suspension test with AICD mice and found a depression-like behavioral phenotype in AICD transgenic mice. Moreover, AICD stimulated FOXO3a transcriptional activation, which in turn negatively regulated AICD. In addition, functional loss of FOXO3a in NPCs derived from the hippocampal dentate gyrus of adult AICD transgenic mice rescued neurogenesis defects. AICD also increased the mRNA expression of FOXO3a target genes related to neurogenesis and cell death. These results suggest that FOXO3a is the functional target of AICD in neurogenesis regulation. Our study reveals the role of AICD in mediating neural stem cell fate to maintain homeostasis during brain development via interaction with FOXO3a.
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Precursor de Proteína beta-Amiloide/fisiología , Proteína Forkhead Box O3/genética , Proteína Forkhead Box O3/metabolismo , Regulación del Desarrollo de la Expresión Génica/genética , Hipocampo/fisiología , Neurogénesis/genética , Animales , Diferenciación Celular/genética , Proliferación Celular/genética , Hipocampo/citología , Masculino , Ratones Transgénicos , Neuronas/fisiología , ARN Mensajero/genética , ARN Mensajero/metabolismoRESUMEN
BACKGROUND: Tau hyperphosphorylation is involved in the progression of Alzheimer's disease (AD). In the present study, we aimed to evaluate the role of linc00507 with respect to modulating Tau phosphorylation in ab AD animal and an Aß42-SH-SY5Y cell model. METHODS: Aß precursor protein (APP)/PS transgenic mice and Aß42-SH-SY5Y cell model were used to investigate the role of linc00507 in AD. A quantitative real-time polymerase chain reaction evaluated the RNA expression of linc00507, miR-181c-5p and microtubule-associated protein tau (MAPT)/tau-tubulin kinase-1 (TTBK1). The interactions between the genes were investigated through changes in one gene expression by regulating another gene in cells and, in addition, correlation assays were performed in mice. Western blot assays examined the protein expression of MAPT/TTBK1, phosphorylation of tau and signaling proteins P25/P35/GSK3ß in response to the regulation of linc00507, miR-181c-5p and MAPT/TTBK1 in cells and also in mice. RESULTS: linc00507 was significantly elevated in hippocampus, and cerebral cortex of APP/PS transgenic mice and AD-like SH-SY5Y cells. It could bind miR-181c-5p and thereby regulate the expression of microtubule-associated protein Tau (MAPT) and tau-tubulin kinase-1 (TTBK1) as a competitive endogenous RNA (ceRNA). MAPT (encoding the tau protein) and TTBK1 (encoding a tau kinase) were identified as direct target genes of miR-181c-5p. Furthermore, linc00507 mediated tau protein hyperphosphorylation by the activation of the P25/P35/GSK3ß signaling pathway through regulating MAPT/TTBK1 by sponging miR-181c-5p. CONCLUSIONS: The findings of the present highlight the regulatory role of linc00507 in tau phosphorylation miR-181c-5p as ceRNA of MAPT/TTBK1 in vitro and in vivo, providing a basis for novel diagnostic and treatment strategies for AD.
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Enfermedad de Alzheimer/patología , Hipocampo/patología , MicroARNs/genética , Neuroblastoma/patología , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas tau/metabolismo , Enfermedad de Alzheimer/etiología , Enfermedad de Alzheimer/metabolismo , Péptidos beta-Amiloides/efectos adversos , Precursor de Proteína beta-Amiloide/fisiología , Animales , Apoptosis , Proliferación Celular , Hipocampo/metabolismo , Masculino , Ratones , Ratones Transgénicos , Neuroblastoma/genética , Neuroblastoma/metabolismo , Fosforilación , Proteínas Serina-Treonina Quinasas/genética , Transducción de Señal , Células Tumorales Cultivadas , Proteínas tau/genéticaRESUMEN
Amyloid precursor protein (APP) is associated with both familial and sporadic forms of Alzheimer's disease. Despite its importance, the role of APP family in neuronal function and survival remains unclear because of perinatal lethality exhibited by knockout mice lacking all three APP family members. Here we report that selective inactivation of APP family members in excitatory neurons of the postnatal forebrain results in neither cortical neurodegeneration nor increases in apoptosis and gliosis up to â¼2 years of age. However, hippocampal synaptic plasticity, learning, and memory are impaired in these mutant mice. Furthermore, hippocampal neurons lacking APP family exhibit hyperexcitability, as evidenced by increased neuronal spiking in response to depolarizing current injections, whereas blockade of Kv7 channels mimics and largely occludes the effects of APP family inactivation. These findings demonstrate that APP family is not required for neuronal survival and suggest that APP family may regulate neuronal excitability through Kv7 channels.
Asunto(s)
Envejecimiento/fisiología , Precursor de Proteína beta-Amiloide/fisiología , Corteza Cerebral/fisiología , Hipocampo/fisiología , Plasticidad Neuronal/fisiología , Neuronas/fisiología , Animales , Antracenos/farmacología , Apoptosis/fisiología , Conducta Animal/fisiología , Supervivencia Celular , Potenciales Postsinápticos Excitadores/fisiología , Canal de Potasio KCNQ1/antagonistas & inhibidores , Ratones , Ratones NoqueadosRESUMEN
The amyloid beta peptide (Aß) is derived from the amyloid precursor protein (APP) by secretase processing. APP is also cleaved by numerous other proteases, such as the type II transmembrane serine protease matriptase, with consequences on the production of Aß. Because the APP homolog protein amyloid-like protein 1 (APLP1) shares similarities with APP, we sought to determine if matriptase also plays a role in its processing. Here, we demonstrate that matriptase directly interacts with APLP1 and that APLP1 is cleaved in cellulo by matriptase in its E1 ectodomains at arginine 124. Replacing Arg124 with Ala abolished APLP1 processing by matriptase. Using a bioluminescence resonance energy transfer (BRET) assay we found that matriptase reduces APLP1 homodimeric interactions. This study identifies matriptase as the first protease cleaving APLP1 in its dimerization domain, potentially altering the multiple functions associated with dimer formation.
Asunto(s)
Precursor de Proteína beta-Amiloide/metabolismo , Serina Endopeptidasas/metabolismo , Secretasas de la Proteína Precursora del Amiloide/metabolismo , Péptidos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/fisiología , Dimerización , Células HEK293 , Humanos , Serina Endopeptidasas/fisiologíaRESUMEN
Asymmetric dimethylarginine (ADMA), an endogenous inhibitor and uncoupler of nitric oxide synthase, has gained attention as a risk factor for cardiac disease, metabolic syndrome, and cerebrovascular disease. In this study, we investigated the role of systemic ADMA overburden in cerebromicrovascular pathology associated with cognitive dysfunction using APPSwDI transgenic mice expressing human ß-amyloid precursor protein Swedish (Tg-SwDI), a model of cerebrovascular ß-amyloidosis. To induce systemic overburden of ADMA, Tg-SwDI mice were treated with a daily dose of exogenous ADMA. ADMA treatment resulted in elevated ADMA levels in the blood and brain of Tg-SwDI mice. ADMA treatment induced the brain nitrosative stress and inflammation as well as enhanced the brain Aß deposition and cognitive impairment in Tg-SwDI mice. However, ADMA treatment had no such effects on wild type mice. ADMA treatment also exacerbated brain microvascular pathology in Tg-SwDI mice as observed by increased blood-brain barrier dysfunction, loss of tight junction proteins, increased endothelial stress fibers, and decreased microvessel density in the brain. In addition, similar observations were made in cultured human brain microvessel endothelial cells, where ADMA in the presence of VEGF-induced endothelial cell signaling for F-actin stress fiber inducing endothelial barrier dysfunction. Overall, these data document the potential role of ADMA in the cognitive pathology under conditions of cerebrovascular ß-amyloidosis.
Asunto(s)
Precursor de Proteína beta-Amiloide/fisiología , Arginina/análogos & derivados , Trastornos Cerebrovasculares/fisiopatología , Disfunción Cognitiva/patología , Endotelio Vascular/patología , Inhibidores Enzimáticos/toxicidad , Animales , Arginina/sangre , Arginina/toxicidad , Disfunción Cognitiva/etiología , Disfunción Cognitiva/metabolismo , Inhibidores Enzimáticos/sangre , Femenino , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Ratones TransgénicosRESUMEN
Glyceraldehyde 3-phosphate dehydrogenase's (GAPDH) proapoptotic response to cellular oxidative stress has suspected implication for Alzheimer's disease (AD). Interestingly, the overexpression of the amyloid precursor protein (APP) can initiate oxidative stress responses within mammalian cell lines. Here, APP695 and APP770 overexpression significantly increased the level of GAPDH, while no effect was observed when the APP homologues APLP1 or APLP2 were used. Heterologous expression of APP695 was shown to increase the level of GAPDH within the cytoplasm by over 100% and within the mitochondria by approximately 50%. Moreover, a shift in organelle distribution from cytoplasm > nucleus > mitochondria in control cell lines to cytoplasm > mitochondria > nucleus in the APP695 overexpressing cell line was also observed. Further, the overexpression of APP695 increased GAPDH aggregation temperature by 3.09 ± 0.46 °C, indicative of greater thermal stability. These results demonstrate a clear correlation between APP overexpression and GAPDH levels, organelle distribution and thermal stability.