RESUMO
Neuronal loss is the central issue in Alzheimer's disease (AD), yet no treatment developed so far can halt AD-associated neurodegeneration. Here, we developed a monoclonal antibody (mAb2A7) against 217 site-phosphorylated human tau (p-tau217) and observed that p-tau217 levels positively correlated with brain atrophy and cognitive impairment in AD patients. Intranasal administration efficiently delivered mAb2A7 into male PS19 tauopathic mouse brain with target engagement and reduced tau pathology/aggregation with little effect on total soluble tau. Further, mAb2A7 treatment blocked apoptosis-associated neuronal loss and brain atrophy, reversed cognitive deficits, and improved motor function in male tauopathic mice. Proteomic analysis revealed that mAb2A7 treatment reversed alterations mainly in proteins associated with synaptic functions observed in murine tauopathy and AD brain. An antibody (13G4) targeting total tau also attenuated tau-associated pathology and neurodegeneration but impaired the motor function of male tauopathic mice. These results implicate p-tau217 as a potential therapeutic target for AD-associated neurodegeneration.
Assuntos
Doença de Alzheimer , Anticorpos Monoclonais , Tauopatias , Proteínas tau , Idoso , Idoso de 80 Anos ou mais , Animais , Feminino , Humanos , Masculino , Camundongos , Doença de Alzheimer/patologia , Doença de Alzheimer/metabolismo , Doença de Alzheimer/terapia , Doença de Alzheimer/tratamento farmacológico , Anticorpos Monoclonais/farmacologia , Anticorpos Monoclonais/administração & dosagem , Encéfalo/metabolismo , Encéfalo/patologia , Encéfalo/efeitos dos fármacos , Modelos Animais de Doenças , Imunoterapia/métodos , Camundongos Transgênicos , Degeneração Neural/patologia , Degeneração Neural/tratamento farmacológico , Fosforilação , Proteínas tau/metabolismo , Tauopatias/tratamento farmacológicoRESUMO
Sorting nexin17 (SNX17) is a member of the sorting nexin family, which plays a crucial role in endosomal trafficking. Previous research has shown that SNX17 is involved in the recycling or degradation of various proteins associated with neurodevelopmental and neurological diseases in cell models. However, the significance of SNX17 in neurological function in the mouse brain has not been thoroughly investigated. In this study, we generated Snx17 knockout mice and observed that the homozygous deletion of Snx17 (Snx17-/-) resulted in lethality. On the other hand, heterozygous mutant mice (Snx17+/-) exhibited anxiety-like behavior with a reduced preference for social novelty. Furthermore, Snx17 haploinsufficiency led to impaired synaptic transmission and reduced maturation of dendritic spines. Through GST pulldown and interactome analysis, we identified the SRC kinase inhibitor, p140Cap, as a potential downstream target of SNX17. We also demonstrated that the interaction between p140Cap and SNX17 is crucial for dendritic spine maturation. Together, this study provides the first in vivo evidence highlighting the important role of SNX17 in maintaining neuronal function, as well as regulating social novelty and anxiety-like behaviors.
Assuntos
Espinhas Dendríticas , Nexinas de Classificação , Animais , Camundongos , Espinhas Dendríticas/metabolismo , Homozigoto , Transporte Proteico , Deleção de Sequência , Nexinas de Classificação/genética , Nexinas de Classificação/metabolismoRESUMO
Senescent cells drive age-related tissue dysfunction partially through the induction of a chronic senescence-associated secretory phenotype (SASP)1. Mitochondria are major regulators of the SASP; however, the underlying mechanisms have not been elucidated2. Mitochondria are often essential for apoptosis, a cell fate distinct from cellular senescence. During apoptosis, widespread mitochondrial outer membrane permeabilization (MOMP) commits a cell to die3. Here we find that MOMP occurring in a subset of mitochondria is a feature of cellular senescence. This process, called minority MOMP (miMOMP), requires BAX and BAK macropores enabling the release of mitochondrial DNA (mtDNA) into the cytosol. Cytosolic mtDNA in turn activates the cGAS-STING pathway, a major regulator of the SASP. We find that inhibition of MOMP in vivo decreases inflammatory markers and improves healthspan in aged mice. Our results reveal that apoptosis and senescence are regulated by similar mitochondria-dependent mechanisms and that sublethal mitochondrial apoptotic stress is a major driver of the SASP. We provide proof-of-concept that inhibition of miMOMP-induced inflammation may be a therapeutic route to improve healthspan.
Assuntos
Apoptose , Senescência Celular , Citosol , DNA Mitocondrial , Mitocôndrias , Animais , Camundongos , Citosol/metabolismo , DNA Mitocondrial/metabolismo , Mitocôndrias/genética , Mitocôndrias/metabolismo , Necrose Dirigida por Permeabilidade Transmembrânica da Mitocôndria , Estudo de Prova de Conceito , Inflamação/metabolismo , Fenótipo , Longevidade , Envelhecimento SaudávelRESUMO
Extensive studies indicate that ß-amyloid (Aß) aggregation is pivotal for Alzheimer's disease (AD) progression; however, cumulative evidence suggests that Aß itself is not sufficient to trigger AD-associated degeneration, and whether other additional pathological factors drive AD pathogenesis remains unclear. Here, we characterize pathogenic aggregates composed of ß2-microglobulin (ß2M) and Aß that trigger neurodegeneration in AD. ß2M, a component of major histocompatibility complex class I (MHC class I), is upregulated in the brains of individuals with AD and constitutes the amyloid plaque core. Elevation of ß2M aggravates amyloid pathology independent of MHC class I, and coaggregation with ß2M is essential for Aß neurotoxicity. B2m genetic ablation abrogates amyloid spreading and cognitive deficits in AD mice. Antisense oligonucleotide- or monoclonal antibody-mediated ß2M depletion mitigates AD-associated neuropathology, and inhibition of ß2M-Aß coaggregation with a ß2M-based blocking peptide ameliorates amyloid pathology and cognitive deficits in AD mice. Our findings identify ß2M as an essential factor for Aß neurotoxicity and a potential target for treating AD.
Assuntos
Doença de Alzheimer , Transtornos Cognitivos , Camundongos , Animais , Doença de Alzheimer/genética , Doença de Alzheimer/patologia , Camundongos Transgênicos , Peptídeos beta-Amiloides/metabolismo , Encéfalo/metabolismo , Cognição , Precursor de Proteína beta-Amiloide/genética , Placa Amiloide/genética , Modelos Animais de DoençasRESUMO
Down syndrome (DS) is a neurological disorder with multiple immune-related symptoms; however, crosstalk between the CNS and peripheral immune system remains unexplored. Using parabiosis and plasma infusion, we found that blood-borne factors drive synaptic deficits in DS. Proteomic analysis revealed elevation of ß2-microglobulin (B2M), a major histocompatibility complex class I (MHC-I) component, in human DS plasma. Systemic administration of B2M in wild-type mice led to synaptic and memory defects similar to those observed in DS mice. Moreover, genetic ablation of B2m or systemic administration of an anti-B2M antibody counteracts synaptic impairments in DS mice. Mechanistically, we demonstrate that B2M antagonizes NMDA receptor (NMDAR) function through interactions with the GluN1-S2 loop; blocking B2M-NMDAR interactions using competitive peptides restores NMDAR-dependent synaptic function. Our findings identify B2M as an endogenous NMDAR antagonist and reveal a pathophysiological role for circulating B2M in NMDAR dysfunction in DS and related cognitive disorders.
Assuntos
Síndrome de Down , Receptores de N-Metil-D-Aspartato , Microglobulina beta-2 , Animais , Humanos , Camundongos , Microglobulina beta-2/metabolismo , Microglobulina beta-2/farmacologia , Disfunção Cognitiva/metabolismo , Reações Cruzadas , Parabiose , Proteômica , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Síndrome de Down/sangue , Síndrome de Down/metabolismoRESUMO
BACKGROUND: Alzheimer's disease (AD) is a neurodegenerative disorder that manifests sequential Aß and tau brain pathology with age-dependent onset. Variants in the microglial immune receptor TREM2 are associated with enhanced risk of onset in sporadic Alzheimer's disease (AD). While recent studies suggest TREM2 dysfunction can aggravate tau pathology, mechanisms underlying TREM2-dependent modulation of tau pathology remains elusive. METHODS: Here, we characterized differences in progressive tau spreading from the medial entorhinal cortex (MEC) to the hippocampus in wildtype (WT) and Trem2 knockout (KO) mice by injection of AAV-P301L tau into the MEC, and correlated changes in hippocampal tau histopathology with spatial and fear memory. We also compared effects of intraneuronal dispersion between cultured microglia and neurons using a microfluidic dispersion assay, analyzed differences in microglial tau trafficking following uptake, and quantified exosomal tau secretion and pathogenicity from purified WT and Trem2 KO exosomes. RESULTS: Trem2 deletion in mice (Trem2 KO) can enhance tau spreading from the medial entorhinal cortex (MEC) to the hippocampus, which coincides with impaired synaptic function and memory behavior. Trem2 deletion in microglia enhances intraneuronal dispersion of tau in vitro between neuronal layers cultured in a microfluidic chamber, and the presence of exosome inhibitors can significantly reduce tau in exosomes and extracellular media from tau-loaded microglia. Although microglial Trem2 deletion has no effect on tau uptake, Trem2 deletion enhances distribution to endosomal and cellular pre-exosomal compartments following internalization. Trem2 deletion has little effect on exosome size, however, proteomic analysis indicates that Trem2 deletion can modulate changes in the microglial proteomic landscape with tau and LPS/ATP treatment conditions associated with exosome induction. Furthermore, exosomes from Trem2 KO microglia show elevated tau levels, and feature enhanced tau-seeding capacity in a tau FRET reporter line compared to exosomes from WT microglia. CONCLUSION: Together, our results reveal a role for Trem2 in suppressing exosomal tau pathogenicity, and demonstrates that Trem2 deletion can enhance tau trafficking, distribution and seeding through microglial exosomes.
Assuntos
Doença de Alzheimer , Exossomos , Glicoproteínas de Membrana/metabolismo , Receptores Imunológicos/metabolismo , Doença de Alzheimer/patologia , Animais , Camundongos , Camundongos Knockout , Microglia/patologia , ProteômicaRESUMO
BACKGROUND: Microglia plays crucial roles in Alzheimer's disease (AD) development. Triggering receptor expressed on myeloid cells 2 (TREM2) in association with DAP12 mediates signaling affecting microglia function. Here we study the negative regulation of TREM2 functions by leukocyte immunoglobulin-like receptor subfamily B member 2 (LILRB2), an inhibitory receptor bearing ITIM motifs. METHODS: To specifically interrogate LILRB2-ligand (oAß and PS) interactions and microglia functions, we generated potent antagonistic LILRB2 antibodies with sub-nanomolar level activities. The biological effects of LILRB2 antagonist antibody (Ab29) were studied in human induced pluripotent stem cell (iPSC)-derived microglia (hMGLs) for migration, oAß phagocytosis, and upregulation of inflammatory cytokines. Effects of the LILRB2 antagonist antibody on microglial responses to amyloid plaques were further studied in vivo using stereotaxic grafted microglia in 5XFAD mice. RESULTS: We confirmed the expression of both LILRB2 and TREM2 in human brain microglia using immunofluorescence. Upon co-ligation of the LILRB2 and TREM2 by shared ligands oAß or PS, TREM2 signaling was significantly inhibited. We identified a monoclonal antibody (Ab29) that blocks LILRB2/ligand interactions and prevents TREM2 signaling inhibition mediated by LILRB2. Further, Ab29 enhanced microglia phagocytosis, TREM2 signaling, migration, and cytokine responses to the oAß-lipoprotein complex in hMGL and microglia cell line HMC3. In vivo studies showed significantly enhanced clustering of microglia around plaques with a prominent increase in microglial amyloid plaque phagocytosis when 5XFAD mice were treated with Ab29. CONCLUSIONS: This study revealed for the first time the molecular mechanisms of LILRB2-mediated inhibition of TREM2 signaling in microglia and demonstrated a novel approach of enhancing TREM2-mediated microglia functions by blocking LILRB2-ligand interactions. Translationally, a LILRB2 antagonist antibody completely rescued the inhibition of TREM2 signaling by LILRB2, suggesting a novel therapeutic strategy for improving microglial functions.
Assuntos
Doença de Alzheimer , Células-Tronco Pluripotentes Induzidas , Doença de Alzheimer/metabolismo , Animais , Encéfalo/metabolismo , Humanos , Células-Tronco Pluripotentes Induzidas/metabolismo , Ligantes , Glicoproteínas de Membrana/metabolismo , Camundongos , Microglia/metabolismo , Placa Amiloide/metabolismo , Receptores Imunológicos/metabolismoRESUMO
Down syndrome (DS), or trisomy 21, is one of the critical risk factors for early-onset Alzheimer's disease (AD), implicating key roles for chromosome 21-encoded genes in the pathogenesis of AD. We previously identified a role for the deubiquitinase USP25, encoded on chromosome 21, in regulating microglial homeostasis in the AD brain; however, whether USP25 affects amyloid pathology remains unknown. Here, by crossing 5×FAD AD and Dp16 DS mice, we observed that trisomy 21 exacerbated amyloid pathology in the 5×FAD brain. Moreover, bacterial artificial chromosome (BAC) transgene-mediated USP25 overexpression increased amyloid deposition in the 5×FAD mouse brain, whereas genetic deletion of Usp25 reduced amyloid deposition. Furthermore, our results demonstrate that USP25 promoted ß cleavage of APP and Aß generation by reducing the ubiquitination and lysosomal degradation of both APP and BACE1. Importantly, pharmacological inhibition of USP25 ameliorated amyloid pathology in the 5×FAD mouse brain. In summary, we identified the DS-related gene USP25 as a critical regulator of AD pathology, and our data suggest that USP25 serves as a potential pharmacological target for AD drug development.
Assuntos
Doença de Alzheimer , Amiloidose , Síndrome de Down , Doença de Alzheimer/patologia , Secretases da Proteína Precursora do Amiloide/genética , Secretases da Proteína Precursora do Amiloide/metabolismo , Peptídeos beta-Amiloides/genética , Peptídeos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Amiloidose/metabolismo , Amiloidose/patologia , Animais , Ácido Aspártico Endopeptidases/genética , Ácido Aspártico Endopeptidases/metabolismo , Encéfalo/metabolismo , Modelos Animais de Doenças , Síndrome de Down/metabolismo , Flavina-Adenina Dinucleotídeo/metabolismo , Camundongos , Camundongos Transgênicos , Ubiquitina Tiolesterase/genética , Ubiquitina Tiolesterase/metabolismoRESUMO
Tauopathies are a group of neurodegenerative diseases characterized by hyperphosphorylation of the microtubule-binding protein, tau, and typically feature axon impairment and synaptic dysfunction. Cyclin-dependent kinase5 (Cdk5) is a major tau kinase and its activity requires p35 or p25 regulatory subunits. P35 is subjected to rapid proteasomal degradation in its membrane-bound form and is cleaved by calpain under stress to a stable p25 form, leading to aberrant Cdk5 activation and tau hyperphosphorylation. The type Ib transmembrane protein RPS23RG1 has been implicated in Alzheimer's disease (AD). However, physiological and pathological roles for RPS23RG1 in AD and other tauopathies are largely unclear. Herein, we observed retarded axon outgrowth, elevated p35 and p25 protein levels, and increased tau phosphorylation at major Cdk5 phosphorylation sites in Rps23rg1 knockout (KO) mice. Both downregulation of p35 and the Cdk5 inhibitor roscovitine attenuated tau hyperphosphorylation and axon outgrowth impairment in Rps23rg1 KO neurons. Interestingly, interactions between the RPS23RG1 carboxyl-terminus and p35 amino-terminus promoted p35 membrane distribution and proteasomal degradation. Moreover, P301L tau transgenic (Tg) mice showed increased tau hyperphosphorylation with reduced RPS23RG1 levels and impaired axon outgrowth. Overexpression of RPS23RG1 markedly attenuated tau hyperphosphorylation and axon outgrowth defects in P301L tau Tg neurons. Our results demonstrate the involvement of RPS23RG1 in tauopathy disorders, and implicate a role for RPS23RG1 in inhibiting tau hyperphosphorylation through homeostatic p35 degradation and suppression of Cdk5 activation. Reduced RPS23RG1 levels in tauopathy trigger aberrant Cdk5-p35 activation, consequent tau hyperphosphorylation, and axon outgrowth impairment, suggesting that RPS23RG1 may be a potential therapeutic target in tauopathy disorders.
Assuntos
Doença de Alzheimer/genética , Fosfotransferases/genética , Proteínas Ribossômicas/genética , Doença de Alzheimer/prevenção & controle , Animais , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Crescimento Neuronal , Neurônios/metabolismo , Fosforilação , Fosfotransferases/antagonistas & inibidores , Proteínas Ribossômicas/antagonistas & inibidores , Proteínas tau/genética , Proteínas tau/metabolismoRESUMO
Variations in many genes linked to sporadic Alzheimer's disease (AD) show abundant expression in microglia, but relationships among these genes remain largely elusive. Here, we establish isogenic human ESC-derived microglia-like cell lines (hMGLs) harboring AD variants in CD33, INPP5D, SORL1, and TREM2 loci and curate a comprehensive atlas comprising ATAC-seq, ChIP-seq, RNA-seq, and proteomics datasets. AD-like expression signatures are observed in AD mutant SORL1 and TREM2 hMGLs, while integrative multi-omic analysis of combined epigenetic and expression datasets indicates up-regulation of APOE as a convergent pathogenic node. We also observe cross-regulatory relationships between SORL1 and TREM2, in which SORL1R744X hMGLs induce TREM2 expression to enhance APOE expression. AD-associated SORL1 and TREM2 mutations also impaired hMGL Aß uptake in an APOE-dependent manner in vitro and attenuated Aß uptake/clearance in mouse AD brain xenotransplants. Using this modeling and analysis platform for human microglia, we provide new insight into epistatic interactions in AD genes and demonstrate convergence of microglial AD genes at the APOE locus.
Assuntos
Doença de Alzheimer/genética , Doença de Alzheimer/patologia , Apolipoproteínas E/genética , Variação Genética , Células-Tronco Embrionárias Humanas/metabolismo , Microglia/patologia , Peptídeos beta-Amiloides/metabolismo , Animais , Encéfalo/patologia , Diferenciação Celular , Linhagem Celular , Cromatina/metabolismo , Epigênese Genética , Redes Reguladoras de Genes , Marcação de Genes , Loci Gênicos , Humanos , Camundongos Transgênicos , Modelos Biológicos , Proteínas Mutantes/metabolismo , Mutação/genética , Fagocitose , Proteoma/metabolismo , Transdução de Sinais , Transcriptoma/genética , Transplante Heterólogo , Regulação para Cima/genéticaRESUMO
SORLA is a transmembrane trafficking protein associated with Alzheimer's disease risk. Although SORLA is abundantly expressed in neurons, physiological roles for SORLA remain unclear. Here, we show that cultured transgenic neurons overexpressing SORLA feature longer neurites, and accelerated neurite regeneration with wounding. Enhanced release of a soluble form of SORLA (sSORLA) is observed in transgenic mouse neurons overexpressing human SORLA, while purified sSORLA promotes neurite extension and regeneration. Phosphoproteomic analyses demonstrate enrichment of phosphoproteins related to the epidermal growth factor (EGFR)/ERK pathway in SORLA transgenic mouse hippocampus from both genders. sSORLA coprecipitates with EGFR in vitro, and sSORLA treatment increases EGFR Y1173 phosphorylation, which is involved in ERK activation in cultured neurons. Furthermore, sSORLA triggers ERK activation, whereas pharmacological EGFR or ERK inhibition reverses sSORLA-dependent enhancement of neurite outgrowth. In search for downstream ERK effectors activated by sSORLA, we identified upregulation of Fos expression in hippocampus from male mice overexpressing SORLA by RNAseq analysis. We also found that Fos is upregulated and translocates to the nucleus in an ERK-dependent manner in neurons treated with sSORLA. Together, these results demonstrate that sSORLA is an EGFR-interacting protein that activates EGFR/ERK/Fos signaling to enhance neurite outgrowth and regeneration.SIGNIFICANCE STATEMENT SORLA is a transmembrane trafficking protein previously known to reduce the levels of amyloid-ß, which is critical in the pathogenesis of Alzheimer's disease. In addition, SORLA mutations are a risk factor for Alzheimer's disease. Interestingly, the SORLA ectodomain is cleaved into a soluble form, sSORLA, which has been shown to regulate cytoskeletal signaling pathways and cell motility in cells outside the nervous system. We show here that sSORLA binds and activates the EGF receptor to induce downstream signaling through the ERK serine/threonine kinase and the Fos transcription factor, thereby enhancing neurite outgrowth. These findings reveal a novel role for sSORLA in promoting neurite regeneration through the EGF receptor/ERK/Fos pathway, thereby demonstrating a potential neuroprotective mechanism involving SORLA.
Assuntos
Receptores ErbB/fisiologia , Sistema de Sinalização das MAP Quinases/fisiologia , Proteínas de Membrana Transportadoras/fisiologia , Regeneração Nervosa/fisiologia , Neuritos/fisiologia , Receptores de LDL/fisiologia , Animais , Células Cultivadas , Feminino , Regulação da Expressão Gênica , Genes fos , Hipocampo/fisiologia , Masculino , Proteínas de Membrana Transportadoras/genética , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Transgênicos , Fosforilação , Receptores de LDL/genéticaRESUMO
Alzheimer's disease (AD) is the most common neurodegenerative disorder seen in age-dependent dementia. There is currently no effective treatment for AD, which may be attributed in part to lack of a clear underlying mechanism. Studies within the last few decades provide growing evidence for a central role of amyloid ß (Aß) and tau, as well as glial contributions to various molecular and cellular pathways in AD pathogenesis. Herein, we review recent progress with respect to Aß- and tau-associated mechanisms, and discuss glial dysfunction in AD with emphasis on neuronal and glial receptors that mediate Aß-induced toxicity. We also discuss other critical factors that may affect AD pathogenesis, including genetics, aging, variables related to environment, lifestyle habits, and describe the potential role of apolipoprotein E (APOE), viral and bacterial infection, sleep, and microbiota. Although we have gained much towards understanding various aspects underlying this devastating neurodegenerative disorder, greater commitment towards research in molecular mechanism, diagnostics and treatment will be needed in future AD research.
Assuntos
Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Neurônios/metabolismo , Proteínas tau/metabolismo , Doença de Alzheimer/patologia , Precursor de Proteína beta-Amiloide/metabolismo , Apolipoproteínas E/metabolismo , HumanosRESUMO
BACKGROUND: Synaptic protein dyshomeostasis and functional loss is an early invariant feature of Alzheimer's disease (AD), yet the unifying etiological pathway remains largely unknown. Knowing that cyclin-dependent kinase 5 (CDK5) plays critical roles in synaptic formation and degeneration, its phosphorylation targets were reexamined in search of candidates with direct global impacts on synaptic protein dynamics, and the associated regulatory network was also analyzed. METHODS: Quantitative phosphoproteomics and bioinformatics analyses were performed to identify top-ranked candidates. A series of biochemical assays was used to investigate the associated regulatory signaling networks. Histological, electrochemical, and behavioral assays were performed in conditional knockout, small hairpin RNA-mediated knockdown, and AD-related mice models to evaluate the relevance of CDK5 to synaptic homeostasis and functions. RESULTS: Among candidates with known implications in synaptic modulations, BAG3 ranked the highest. CDK5-mediated phosphorylation on S297/S291 (mouse/human) destabilized BAG3. Loss of BAG3 unleashed the selective protein degradative function of the HSP70 machinery. In neurons, this resulted in enhanced degradation of a number of glutamatergic synaptic proteins. Conditional neuronal knockout of Bag3 in vivo led to impairment of learning and memory functions. In human AD and related mouse models, aberrant CDK5-mediated loss of BAG3 yielded similar effects on synaptic homeostasis. Detrimental effects of BAG3 loss on learning and memory functions were confirmed in these mice, and such effects were reversed by ectopic BAG3 reexpression. CONCLUSIONS: Our results highlight that the neuronal CDK5-BAG3-HSP70 signaling axis plays a critical role in modulating synaptic homeostasis. Dysregulation of the signaling pathway directly contributes to synaptic dysfunction and AD pathogenesis.
Assuntos
Doença de Alzheimer , Quinase 5 Dependente de Ciclina , Proteínas Adaptadoras de Transdução de Sinal , Doença de Alzheimer/genética , Animais , Proteínas Reguladoras de Apoptose/metabolismo , Quinase 5 Dependente de Ciclina/genética , Quinase 5 Dependente de Ciclina/metabolismo , Memória , Camundongos , Neurônios/metabolismo , Transdução de SinaisRESUMO
Dysregulation of various APP trafficking components in the endosome has been previously implicated in Alzheimer's disease (AD). Although single nucleotide polymorphisms within the gene locus encoding the endosomal component, SNX8 have been previously associated with AD, how SNX8 levels are altered and its contribution to AD onset is currently unknown. Here, we observe decreased expression of SNX8 in human AD and AD mouse brain. SNX8 predominantly localized to early and late endosomes, where SNX8 overexpression enhanced total APP levels, cell surface APP distribution and consequent soluble APPα cleavage. SNX8 depletion resulted in elevated ß-amyloid (Aß) levels, while SNX8 overexpression reduced Aß levels in cells and in an APP/PS1 AD mouse model. Importantly, SNX8 overexpression rescued cognitive impairment in APP/PS1 mice. Together, these results implicate a neuroprotective role for SNX8 in enhancing non-amyloidogenic APP trafficking and processing pathways. Given that endosomal dysfunction is an early event in AD, restoration of dysfunctional endosomal components such as SNX8 may be beneficial in future therapeutic strategies.
RESUMO
Oxidative stress is a common feature of neurodegenerative diseases and plays an important role in disease progression. Appoptosin is a pro-apoptotic protein that contributes to the pathogenesis of neurodegenerative diseases such as Alzheimer's disease and progressive supranuclear palsy. However, whether appoptosin mediates oxidative stress-induced neurotoxicity has yet to be determined. Here, we observe that appoptosin protein levels are induced by hydrogen peroxide (H2O2) exposure through the inhibition of proteasomal appoptosin degradation. Furthermore, we demonstrate that overexpression of appoptosin induces apoptosis through the JNK-FoxO1 pathway. Importantly, knockdown of appoptosin can ameliorate H2O2-induced JNK activation and apoptosis in primary neurons. Thus, we propose that appoptosin functions as an upstream regulator of the JNK-FoxO1 pathway, contributing to cell death in response to oxidative stress during neurodegeneration.
RESUMO
TREM2 and CD33 are microglial receptors associated with Alzheimer's disease (AD) risk. In this issue of Neuron, Griciuc et al. (2019) demonstrate opposing effects of CD33 and TREM2 on AD phenotypes, where CD33 deletion promotes neuroprotection in a manner dependent on TREM2.
Assuntos
Doença de Alzheimer , Humanos , Glicoproteínas de Membrana , Microglia , Neuroproteção , Fenótipo , Receptores Imunológicos , Lectina 3 Semelhante a Ig de Ligação ao Ácido SiálicoRESUMO
Mechanisms underlying motor neuron degeneration in amyotrophic lateral sclerosis (ALS) are yet unclear. Specific deletion of the ER-component membralin in astrocytes manifested postnatal motor defects and lethality in mice, causing the accumulation of extracellular glutamate through reducing the glutamate transporter EAAT2. Restoring EAAT2 levels in membralin KO astrocytes limited astrocyte-dependent excitotoxicity in motor neurons. Transcriptomic profiles from mouse astrocytic membralin KO motor cortex indicated significant perturbation in KEGG pathway components related to ALS, including downregulation of Eaat2 and upregulation of Tnfrsf1a. Changes in gene expression with membralin deletion also overlapped with mouse ALS models and reactive astrocytes. Our results shown that activation of TNF receptor (TNFR1)-NFκB pathway known to suppress Eaat2 transcription was upregulated with membralin deletion. Further, reduced membralin and EAAT2 levels correlated with disease progression in spinal cord from SOD1-mutant mouse models, and reductions in membralin/EAAT2 were observed in human ALS spinal cord. Importantly, overexpression of membralin in SOD1G93A astrocytes decreased TNFR1 levels and increased EAAT2 expression, and improved motor neuron survival. Importantly, upregulation of membralin in SOD1G93A mice significantly prolonged mouse survival. Together, our study provided a mechanism for ALS pathogenesis where membralin limited glutamatergic neurotoxicity, suggesting that modulating membralin had potentials in ALS therapy.
Assuntos
Esclerose Lateral Amiotrófica/metabolismo , Astrócitos/metabolismo , Ácido Glutâmico/metabolismo , Córtex Motor/metabolismo , Proteínas do Tecido Nervoso/deficiência , Esclerose Lateral Amiotrófica/genética , Esclerose Lateral Amiotrófica/patologia , Animais , Astrócitos/patologia , Regulação para Baixo , Transportador 2 de Aminoácido Excitatório/biossíntese , Transportador 2 de Aminoácido Excitatório/genética , Ácido Glutâmico/genética , Humanos , Camundongos , Camundongos Knockout , Córtex Motor/patologia , Proteínas do Tecido Nervoso/metabolismo , Receptores Tipo I de Fatores de Necrose Tumoral/biossíntese , Receptores Tipo I de Fatores de Necrose Tumoral/genética , Superóxido Dismutase/biossíntese , Superóxido Dismutase/genética , Transcrição Gênica , Regulação para CimaRESUMO
BACKGROUND: Although synaptic impairment is a prerequisite to cognitive deficiencies in Alzheimer's disease (AD), mechanisms underlying the dysregulation of essential synaptic scaffolding components and their integrity remain elusive. RPS23RG1 is a newly identified protein implicated in AD. However, the physiological function of RPS23RG1 has yet to be determined. METHODS: We investigated the role of RPS23RG1 in maintaining synaptic structure and function in cell cultures and in Rps23rg1 knockout mice and determined whether targeting RPS23RG1-mediated pathways has therapeutic potential in APP/PS1 AD model mice. RESULTS: Deletion of the Rps23rg1 gene resulted in severe memory deficits and impairment of postsynaptic structure and function, with marked reductions in postsynaptic densities-93 and -95 (PSD-93 and PSD-95) levels. RPS23RG1 interacted with PSD-93/PSD-95 through its intracellular domain, consequently sequestering PSD-93/PSD-95 from murine double minute 2-mediated ubiquitination and degradation, thereby maintaining synaptic function. Restoration of PSD-93/PS-D95 levels reversed synaptic and memory deficits in Rps23rg1 knockout mice. We further observed attenuated RPS23RG1 expression in human AD, which positively correlated with PSD-93/PSD-95 levels. Importantly, an RPS23RG1-derived peptide comprising a unique PSD-93/PSD-95 interaction motif rescued synaptic and cognitive defects in Rps23rg1 knockout and AD mouse models. CONCLUSIONS: Our results reveal a role for RPS23RG1 in maintaining synaptic integrity and function and provide a new mechanism for synaptic dysfunction in AD pathogenesis. This demonstrates that RPS23RG1-mediated pathways show good therapeutic potential in AD intervention.
Assuntos
Disfunção Cognitiva/metabolismo , Proteína 4 Homóloga a Disks-Large/metabolismo , Plasticidade Neuronal , Proteínas Ribossômicas/metabolismo , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Doença de Alzheimer/fisiopatologia , Animais , Disfunção Cognitiva/genética , Disfunção Cognitiva/fisiopatologia , Modelos Animais de Doenças , Regulação da Expressão Gênica , Técnicas de Silenciamento de Genes , Hipocampo/metabolismo , Humanos , Aprendizagem em Labirinto , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteínas Ribossômicas/genéticaRESUMO
Alzheimer's disease (AD) comprises two major pathological hallmarks: extraneuronal deposition of ß-amyloid (Aß) peptides ("senile plaques") and intraneuronal aggregation of the microtubule-associated protein tau ("neurofibrillary tangles"). Aß is derived from sequential cleavage of the ß-amyloid precursor protein by ß- and γ-secretases, while aggregated tau is hyperphosphorylated in AD. Mounting evidence suggests that dysregulated trafficking of these AD-related proteins contributes to AD pathogenesis. Rab proteins are small GTPases that function as master regulators of vesicular transport and membrane trafficking. Multiple Rab GTPases have been implicated in AD-related protein trafficking, and their expression has been observed to be altered in postmortem AD brain. Here we review current implicated roles of Rab GTPase dysregulation in AD pathogenesis. Further elucidation of the pathophysiological role of Rab GTPases will likely reveal novel targets for AD therapeutics.