RESUMO
In neurodegenerative diseases like Alzheimer's disease (AD), tau is hyperphosphorylated and forms aggregates and neurofibrillary tangles in affected neurons. Autophagy is critical to clear the aggregates of disease-associated proteins and is often altered in patients and animal models of AD. Because mechanistic target of rapamycin (mTOR) negatively regulates autophagy and is hyperactive in the brains of patients with AD, mTOR is an attractive therapeutic target for AD. However, pharmacological strategies to increase autophagy by targeting mTOR inhibition cause various side effects. Therefore, autophagy activation mediated by non-mTOR pathways is a new option for autophagy-based AD therapy. Here, we report that pimozide activates autophagy to rescue tau pathology in an AD model. Pimozide increased autophagic flux through the activation of the AMPK-Unc-51 like autophagy activating kinase 1 (ULK1) axis, but not of mTOR, in neuronal cells, and this function was independent of dopamine D2 receptor inhibition. Pimozide reduced levels of abnormally phosphorylated tau aggregates in neuronal cells. Further, daily intraperitoneal (i.p.) treatment of pimozide led to a recovery from memory deficits of TauC3 mice expressing a caspase-cleaved form of tau. In the brains of these mice, we found increased phosphorylation of AMPK1 and ULK1, and reduced levels of the soluble oligomers and NP40-insoluble aggregates of abnormally phosphorylated tau. Together, these results suggest that pimozide rescues memory impairments in TauC3 mice and reduces tau aggregates by increasing autophagic flux through the mTOR-independent AMPK-ULK1 axis.
Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Proteína Homóloga à Proteína-1 Relacionada à Autofagia/metabolismo , Autofagia/fisiologia , Pimozida/farmacologia , Proteínas tau/metabolismo , Animais , Autofagia/efeitos dos fármacos , Células Cultivadas , Antagonistas de Dopamina/farmacologia , Antagonistas de Dopamina/uso terapêutico , Feminino , Células HeLa , Humanos , Masculino , Transtornos da Memória/metabolismo , Transtornos da Memória/prevenção & controle , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Pimozida/uso terapêutico , Proteínas tau/antagonistas & inibidoresRESUMO
In Alzheimer's disease and other tauopathy, abnormal Tau proteins form intracellular aggregates and Tau filaments. However, the mechanisms that regulate Tau aggregation are not fully understood. In this paper, we show that POLDIP2 is a novel regulator of Tau aggregation. From a cell-based screening using cDNA expression library, we isolated POLDIP2 which increased Tau aggregation. Expression of POLDIP2 was increased in neuronal cells by the multiple stresses, including Aß, TNF-α and H2O2. Accordingly, ectopic expression of POLDIP2 enhanced the formation of Tau aggregates without affecting Tau phosphorylation, while down-regulation of POLDIP2 alleviated ROS-induced Tau aggregation. Interestingly, we found that POLDIP2 overexpression induced impairments of autophagy activity and partially proteasome activity and this activities were retained in DUF525 domain of POLDIP2. In a drosophila model of human tauopathy, knockdown of the drosophila POLDIP2 homolog, CG12162, attenuated rough eye phenotype induced by Tau overexpression. Further, the lifespan of neural-Tau(R406W) transgenic files were recovered by CG12162 knockdown. Together, these observations indicate that POLDIP2 plays a crucial role in Tau aggregation via the impairment of autophagy activity, providing insight into Tau aggregation in Tau pathology.
Assuntos
Proteínas Nucleares/metabolismo , Proteínas tau/metabolismo , Animais , Animais Geneticamente Modificados , Autofagia , Linhagem Celular , Modelos Animais de Doenças , Regulação para Baixo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Técnicas de Silenciamento de Genes , Genes de Insetos , Células HEK293 , Células HeLa , Humanos , Degeneração Neural/metabolismo , Degeneração Neural/patologia , Proteínas Nucleares/antagonistas & inibidores , Proteínas Nucleares/genética , Complexo de Endopeptidases do Proteassoma/metabolismo , Domínios e Motivos de Interação entre Proteínas , Multimerização Proteica , RNA Interferente Pequeno/genética , Espécies Reativas de Oxigênio/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Proteínas tau/química , Proteínas tau/genéticaRESUMO
BACKGROUND: In tauopathies, brain regions with tau accumulation strongly correlate with clinical symptoms, and spreading of misfolded tau along neural network leads to disease progression. However, the underlying mechanisms by which tau proteins enter neurons during pathological propagation remain unclear. METHODS: To identify membrane receptors responsible for neuronal propagation of tau oligomers, we established a cell-based tau uptake assay and screened complementary DNA expression library. Tau uptake and propagation were analyzed in vitro and in vivo using a microfluidic device and stereotactic injection. The cognitive function of mice was assessed using behavioral tests. RESULTS: From a genome-wide cell-based functional screening, RAGE (receptor for advanced glycation end products) was isolated to stimulate the cellular uptake of tau oligomers. Rage deficiency reduced neuronal uptake of pathological tau prepared from rTg4510 mouse brains or cerebrospinal fluid from patients with Alzheimer's disease and slowed tau propagation between neurons cultured in a 3-chamber microfluidic device. RAGE levels were increased in the brains of rTg4510 mice and tau oligomer-treated neurons. Rage knockout decreased tau transmission in the brains of nontransgenic mice after injection with Alzheimer's disease patient-derived tau and ameliorated memory loss after injection with GFP-P301L-tau-AAV. Treatment of RAGE antagonist FPS-ZM1 blocked transsynaptic tau propagation and inflammatory responses and alleviated cognitive impairment in rTg4510 mice. CONCLUSIONS: These results suggest that in neurons and microglia, RAGE binds to pathological tau and facilitates neuronal tau pathology progression and behavioral deficits in tauopathies.
Assuntos
Doença de Alzheimer , Receptor para Produtos Finais de Glicação Avançada , Tauopatias , Proteínas tau , Animais , Camundongos , Doença de Alzheimer/metabolismo , Encéfalo/metabolismo , Modelos Animais de Doenças , Transtornos da Memória/metabolismo , Camundongos Transgênicos , Receptor para Produtos Finais de Glicação Avançada/metabolismo , Proteínas tau/metabolismo , Tauopatias/metabolismoRESUMO
The enzyme γ-secretase generates ß-amyloid (Aß) peptides by cleaving amyloid protein precursor (APP); the aggregation of these peptides is associated with Alzheimer's disease (AD). Despite the development of various γ-secretase regulators, their clinical use is limited by coincident disruption of other γ-secretase-regulated substrates, such as Notch. Using a genome-wide functional screen of γ-secretase activity in cells and a complementary DNA expression library, we found that SERP1 is a previously unknown γ-secretase activator that stimulates Aß generation in cells experiencing endoplasmic reticulum (ER) stress, such as is seen with diabetes. SERP1 interacted with a subcomplex of γ-secretase (APH1A/NCT) through its carboxyl terminus to enhance the assembly and, consequently, the activity of the γ-secretase holoenzyme complex. In response to ER stress, SERP1 preferentially recruited APP rather than Notch into the γ-secretase complex and enhanced the subcellular localization of the complex into lipid rafts, increasing Aß production. Moreover, SERP1 abundance, γ-secretase assembly, and Aß production were increased both in cells exposed to high amounts of glucose and in diabetic AD model mice. Conversely, Aß production was decreased by knocking down SERP1 in cells or in the hippocampi of mice. Compared to postmortem samples from control individuals, those from patients with AD showed increased SERP1 expression in the hippocampus and parietal lobe. Together, our findings suggest that SERP1 is an APP-biased regulator of γ-secretase function in the context of cell stress, providing a possible molecular explanation for the link between diabetes and sporadic AD.