RESUMO
Although APP metabolism is being intensively investigated, a large fraction of its modulators is yet to be characterized. In this context, we combined two genome-wide high-content screenings to assess the functional impact of miRNAs and genes on APP metabolism and the signaling pathways involved. This approach highlighted the involvement of FERMT2 (or Kindlin-2), a genetic risk factor of Alzheimer's disease (AD), as a potential key modulator of axon guidance, a neuronal process that depends on the regulation of APP metabolism. We found that FERMT2 directly interacts with APP to modulate its metabolism, and that FERMT2 underexpression impacts axonal growth, synaptic connectivity, and long-term potentiation in an APP-dependent manner. Last, the rs7143400-T allele, which is associated with an increased AD risk and localized within the 3'UTR of FERMT2, induced a downregulation of FERMT2 expression through binding of miR-4504 among others. This miRNA is mainly expressed in neurons and significantly overexpressed in AD brains compared to controls. Altogether, our data provide strong evidence for a detrimental effect of FERMT2 underexpression in neurons and insight into how this may influence AD pathogenesis.
Assuntos
Doença de Alzheimer , Doença de Alzheimer/genética , Precursor de Proteína beta-Amiloide/genética , Humanos , Proteínas de Membrana , Proteínas de Neoplasias , Plasticidade Neuronal/genética , Neurônios , Fatores de RiscoRESUMO
The bridging integrator 1 gene (BIN1) is a major genetic risk factor for Alzheimer's disease (AD). In this report, we investigated how BIN1-dependent pathophysiological processes might be associated with Tau. We first generated a cohort of control and transgenic mice either overexpressing human MAPT (TgMAPT) or both human MAPT and BIN1 (TgMAPT;TgBIN1), which we followed-up from 3 to 15 months. In TgMAPT;TgBIN1 mice short-term memory deficits appeared earlier than in TgMAPT mice; however-unlike TgMAPT mice-TgMAPT;TgBIN1 mice did not exhibit any long-term or spatial memory deficits for at least 15 months. After killing the cohort at 18 months, immunohistochemistry revealed that BIN1 overexpression prevents both Tau mislocalization and somatic inclusion in the hippocampus, where an increase in BIN1-Tau interaction was also observed. We then sought mechanisms controlling the BIN1-Tau interaction. We developed a high-content screening approach to characterize modulators of the BIN1-Tau interaction in an agnostic way (1,126 compounds targeting multiple pathways), and we identified-among others-an inhibitor of calcineurin, a Ser/Thr phosphatase. We determined that calcineurin dephosphorylates BIN1 on a cyclin-dependent kinase phosphorylation site at T348, promoting the open conformation of the neuronal BIN1 isoform. Phosphorylation of this site increases the availability of the BIN1 SH3 domain for Tau interaction, as demonstrated by nuclear magnetic resonance experiments and in primary neurons. Finally, we observed that although the levels of the neuronal BIN1 isoform were unchanged in AD brains, phospho-BIN1(T348):BIN1 ratio was increased, suggesting a compensatory mechanism. In conclusion, our data support the idea that BIN1 modulates the AD risk through an intricate regulation of its interaction with Tau. Alteration in BIN1 expression or activity may disrupt this regulatory balance with Tau and have direct effects on learning and memory.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Transtornos da Memória/metabolismo , Memória de Longo Prazo/fisiologia , Proteínas do Tecido Nervoso/metabolismo , Tauopatias/metabolismo , Proteínas Supressoras de Tumor/metabolismo , Proteínas tau/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Animais , Encéfalo/metabolismo , Encéfalo/patologia , Transtornos da Memória/genética , Transtornos da Memória/patologia , Camundongos , Camundongos Transgênicos , Proteínas do Tecido Nervoso/genética , Neurônios/metabolismo , Neurônios/patologia , Fosforilação , Memória Espacial/fisiologia , Tauopatias/genética , Tauopatias/patologia , Proteínas Supressoras de Tumor/genéticaRESUMO
Tau-mediated neurodegeneration in Alzheimer's disease and tauopathies is generally assumed to start in a normally developed brain. However, several lines of evidence suggest that impaired Tau isoform expression during development could affect mitosis and ploidy in post-mitotic differentiated tissue. Interestingly, the relative expression levels of Tau isoforms containing either 3 (3R-Tau) or 4 repeats (4R-Tau) play an important role both during brain development and neurodegeneration. Here, we used genetic and cellular tools to study the link between 3R and 4R-Tau isoform expression, mitotic progression in neuronal progenitors and post-mitotic neuronal survival. Our results illustrated that the severity of Tau-induced adult phenotypes depends on 4R-Tau isoform expression during development. As recently described, we observed a mitotic delay in 4R-Tau expressing cells of larval eye discs and brains. Live imaging revealed that the spindle undergoes a cycle of collapse and recovery before proceeding to anaphase. Furthermore, we found a high level of aneuploidy in post-mitotic differentiated tissue. Finally, we showed that overexpression of wild type and mutant 4R-Tau isoform in neuroblastoma SH-SY5Y cell lines is sufficient to induce monopolar spindles. Taken together, our results suggested that neurodegeneration could be in part linked to neuronal aneuploidy caused by 4R-Tau expression during brain development.
Assuntos
Aneuploidia , Regulação da Expressão Gênica no Desenvolvimento , Neurônios/metabolismo , Tauopatias/genética , Tauopatias/metabolismo , Proteínas tau/genética , Proteínas tau/metabolismo , Animais , Linhagem Celular , Sobrevivência Celular/genética , Humanos , Mitose/genética , Mutação , Células-Tronco Neurais/metabolismo , Fenótipo , Células Fotorreceptoras/metabolismo , Isoformas de Proteínas , Tauopatias/patologiaRESUMO
Genome-wide association studies (GWASs) have identified 19 susceptibility loci for Alzheimer's disease (AD). However, understanding how these genes are involved in the pathophysiology of AD is one of the main challenges of the "post-GWAS" era. At least 123 genes are located within the 19 susceptibility loci; hence, a conventional approach (studying the genes one by one) would not be time- and cost-effective. We therefore developed a genome-wide, high-content siRNA screening approach and used it to assess the functional impact of gene under-expression on APP metabolism. We found that 832 genes modulated APP metabolism. Eight of these genes were located within AD susceptibility loci. Only FERMT2 (a ß3-integrin co-activator) was also significantly associated with a variation in cerebrospinal fluid Aß peptide levels in 2886 AD cases. Lastly, we showed that the under-expression of FERMT2 increases Aß peptide production by raising levels of mature APP at the cell surface and facilitating its recycling. Taken as a whole, our data suggest that FERMT2 modulates the AD risk by regulating APP metabolism and Aß peptide production.
Assuntos
Precursor de Proteína beta-Amiloide/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , RNA Interferente Pequeno/genética , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Animais , Biomarcadores/líquido cefalorraquidiano , Membrana Celular/metabolismo , Córtex Cerebral/metabolismo , Córtex Cerebral/patologia , Loci Gênicos , Predisposição Genética para Doença , Estudo de Associação Genômica Ampla , Células HEK293 , Hipocampo/metabolismo , Hipocampo/patologia , Humanos , Neurônios/metabolismo , Neurônios/patologia , Interferência de RNA , RatosRESUMO
Although several ADAMs (A disintegrin-like and metalloproteases) have been shown to contribute to the amyloid precursor protein (APP) metabolism, the full spectrum of metalloproteases involved in this metabolism remains to be established. Transcriptomic analyses centred on metalloprotease genes unraveled a 50% decrease in ADAM30 expression that inversely correlates with amyloid load in Alzheimer's disease brains. Accordingly, in vitro down- or up-regulation of ADAM30 expression triggered an increase/decrease in Aß peptides levels whereas expression of a biologically inactive ADAM30 (ADAM30(mut)) did not affect Aß secretion. Proteomics/cell-based experiments showed that ADAM30-dependent regulation of APP metabolism required both cathepsin D (CTSD) activation and APP sorting to lysosomes. Accordingly, in Alzheimer-like transgenic mice, neuronal ADAM30 over-expression lowered Aß42 secretion in neuron primary cultures, soluble Aß42 and amyloid plaque load levels in the brain and concomitantly enhanced CTSD activity and finally rescued long term potentiation alterations. Our data thus indicate that lowering ADAM30 expression may favor Aß production, thereby contributing to Alzheimer's disease development.
Assuntos
Proteínas ADAM/metabolismo , Peptídeos beta-Amiloides/metabolismo , Catepsina D/metabolismo , Proteínas ADAM/antagonistas & inibidores , Proteínas ADAM/genética , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Sequência de Aminoácidos , Animais , Encéfalo/metabolismo , Encéfalo/patologia , Catepsina D/química , Linhagem Celular Tumoral , Regulação para Baixo/efeitos dos fármacos , Células HEK293 , Humanos , Lisossomos/metabolismo , Macrolídeos/farmacologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Microscopia de Fluorescência , Técnicas de Patch-Clamp , Pepstatinas/farmacologia , Interferência de RNA , RNA Interferente Pequeno/metabolismoRESUMO
INTRODUCTION: The application of high-throughput genomic approaches has revealed 24 novel risk loci for Alzheimer's disease (AD). We recently reported that the bridging integrator 1 (BIN1) risk gene is linked to Tau pathology. RESULTS: We used glutathione S-transferase pull-down assays and nuclear magnetic resonance (NMR) experiments to demonstrate that BIN1 and Tau proteins interact directly and then map the interaction between BIN1's SH3 domain and Tau's proline-rich domain (PRD) . Our NMR data showed that Tau phosphorylation at Thr231 weakens the SH3-PRD interaction. Using primary neurons, we found that BIN1-Tau complexes partly co-localize with the actin cytoskeleton; however, these complexes were not observed with Thr231-phosphorylated Tau species. CONCLUSION: Our results show that (i) BIN1 and Tau bind through an SH3-PRD interaction and (ii) the interaction is downregulated by phosphorylation of Tau Thr231 (and potentially other residues). Our study sheds new light on regulation of the BIN1/Tau interaction and opens up new avenues for exploring its complex's role in the pathogenesis of AD.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Neurônios/metabolismo , Proteínas Nucleares/metabolismo , Prolina/metabolismo , Proteínas Supressoras de Tumor/metabolismo , Domínios de Homologia de src/fisiologia , Proteínas tau/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/química , Proteínas Adaptadoras de Transdução de Sinal/genética , Animais , Animais Recém-Nascidos , Encéfalo/citologia , Células Cultivadas , Células HEK293 , Humanos , Espectroscopia de Ressonância Magnética , Proteínas Nucleares/química , Proteínas Nucleares/genética , Fosforilação/fisiologia , Conformação Proteica , Ratos , Transfecção , Proteínas Supressoras de Tumor/química , Proteínas Supressoras de Tumor/genética , Proteínas tau/química , Proteínas tau/genéticaRESUMO
Aneuploidy is a common feature of many cancers, suggesting that genomic stability is essential to prevent tumorigenesis. Also, during meiosis, chromosome non-disjunction produces gamete imbalance and when fertilized result in developmental arrest or severe birth defects. The spindle assembly checkpoint prevents chromosome mis-segregation during both mitosis and meiosis. In mitosis, this control system monitors kinetochore-microtubule attachment while in meiosis its role is still unclear. Interestingly, recent data suggest that defects in the spindle assembly checkpoint are unlikely to cause cancer development but might facilitate tumour progression. However, in meiosis a weakened checkpoint could contribute to age-related aneuploidy found in humans.