RESUMEN
Alzheimer's disease is the most common neurodegenerative disease, associated with aggregation of amyloid-ß (Aß) peptides. The exact mechanism of neuronal cell dysfunction in Alzheimer's disease is poorly understood and numerous models have been used to decipher the mechanisms leading to cellular death. Yeast cells might be a good model to understand the intracellular toxicity triggered by Aß peptides. Indeed, yeast has been used as a model to examine protein functions or cellular pathways that mediate the secretion, aggregation and subsequent toxicity of proteins associated with human neurodegenerative disorders. In the present study, we use the yeast Saccharomyces cerevisiae as a model system to study the effects of intracellular Aß in fusion with green fluorescent protein. We sent this fusion protein into the secretory pathway and showed that intracellular traffic pathways are necessary for the generation of toxic species. Yeast PICALM orthologs are involved in cellular toxicity, indicating conservation of the mechanisms of toxicity from mammals to yeast. Finally, our model demonstrates the capacity for intracellular Aß to cross intracellular membranes and target mitochondrial organelles.
Asunto(s)
Péptidos beta-Amiloides/química , Péptidos beta-Amiloides/metabolismo , Proteínas de Ensamble de Clatrina Monoméricas/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Enfermedad de Alzheimer/etiología , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/metabolismo , Péptidos beta-Amiloides/genética , Péptidos beta-Amiloides/toxicidad , Transporte Biológico Activo , Endocitosis , Proteínas Fluorescentes Verdes/genética , Proteínas Fluorescentes Verdes/metabolismo , Proteínas de Choque Térmico/genética , Proteínas de Choque Térmico/metabolismo , Humanos , Modelos Biológicos , Modelos Neurológicos , Proteínas de Ensamble de Clatrina Monoméricas/genética , Consumo de Oxígeno , Multimerización de Proteína , Procesamiento Proteico-Postraduccional , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Proteínas Recombinantes de Fusión/toxicidad , Saccharomyces cerevisiae/efectos de los fármacos , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genéticaRESUMEN
Despite intensive research into how amyloid structures can impair cellular viability, the molecular nature of these toxic species and the cellular mechanisms involved are not clearly defined and may differ from one disease to another. We systematically analyzed, in Saccharomyces cerevisiae, genes that increase the toxicity of an amyloid (M8), previously selected in yeast on the sole basis of its cellular toxicity (and consequently qualified as "artificial"). This genomic screening identified the Vps-C HOPS (homotypic vacuole fusion and protein sorting) complex as a key-player in amyloid toxicity. This finding led us to analyze further the phenotype induced by M8 expression. M8-expressing cells displayed an identical phenotype to vps mutants in terms of endocytosis, vacuolar morphology and salt sensitivity. The direct and specific interaction between M8 and lipids reinforces the role of membrane formation in toxicity due to M8. Together these findings suggest a model in which amyloid toxicity results from membrane fission.