RESUMO
Genome-wide association studies (GWAS) have identified a region upstream the BIN1 gene as the most important genetic susceptibility locus in Alzheimer's disease (AD) after APOE. We report that BIN1 transcript levels were increased in AD brains and identified a novel 3 bp insertion allele â¼28 kb upstream of BIN1, which increased (i) transcriptional activity in vitro, (ii) BIN1 expression levels in human brain and (iii) AD risk in three independent case-control cohorts (Meta-analysed Odds ratio of 1.20 (1.14-1.26) (P=3.8 × 10(-11))). Interestingly, decreased expression of the Drosophila BIN1 ortholog Amph suppressed Tau-mediated neurotoxicity in three different assays. Accordingly, Tau and BIN1 colocalized and interacted in human neuroblastoma cells and in mouse brain. Finally, the 3 bp insertion was associated with Tau but not Amyloid loads in AD brains. We propose that BIN1 mediates AD risk by modulating Tau pathology.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Doença de Alzheimer/genética , Doença de Alzheimer/patologia , Predisposição Genética para Doença/genética , Proteínas Nucleares/genética , Proteínas Supressoras de Tumor/genética , Proteínas tau/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/biossíntese , Doença de Alzheimer/metabolismo , Animais , Encéfalo/metabolismo , Encéfalo/patologia , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Estudos de Casos e Controles , Células Cultivadas , Proteínas de Drosophila/deficiência , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Endofenótipos , Expressão Gênica/genética , Humanos , Camundongos , Degeneração Neural/genética , Degeneração Neural/patologia , Proteínas Nucleares/biossíntese , Placa Amiloide/patologia , Polimorfismo de Nucleotídeo Único/genética , Sinaptossomos/patologia , Fatores de Transcrição/deficiência , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Proteínas Supressoras de Tumor/biossíntese , Proteínas tau/antagonistas & inibidoresRESUMO
Understanding mechanisms controlling neuronal cell death and survival under conditions of altered energy supply (e.g., during stroke) is fundamentally important for the development of therapeutic strategies. The function of autophagy herein is unclear, as both its beneficial and detrimental roles have been described. We previously demonstrated that loss of AMP-activated protein kinase (AMPK), an evolutionarily conserved enzyme that maintains cellular energy balance, leads to activity-dependent degeneration in neuronal tissue. Here, we show that energy depletion in Drosophila AMPK mutants results in increased autophagy that convincingly promotes, rather than rescues, neurodegeneration. The generated excessive autophagic response is accompanied by increased TOR and S6K activity in the absence of an AMPK-mediated negative regulatory feedback loop. Moreover, energy-depleted neurons use a phagocytic-like process as a means to cellular survival at the expense of surrounding cells. Consequently, phagocytosis stimulation by expression of the scavenger receptor Croquemort significantly delays neurodegeneration. This study thus reveals a potentially novel strategy for cellular survival during conditions of extreme energy depletion, resembling xeno-cannibalistic events seen in metastatic tumors. We provide new insights into the roles of autophagy and phagocytosis in the neuronal metabolic stress response and open new avenues into understanding of human disease and development of therapeutic strategies.