Screening of therapautic compounds in a C. elegans model of Machado-Joseph disease: targeting mitochondria

• Autor(a) principal: Miranda, Vera Adriana Batista
• Data de Publicação: 2011
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.22/8755
• topic: Machado-Joseph disease; ataxin-3; protein aggregation; neuronal dysfunction; mitochondrial dysfunction; creatine; small molecules; Domínio/Área Científica::Ciências Médicas::Ciências da Saúde

Since the early 90’s a new class of inherited neurodegenerative diseases has been characterized, the polyglutamine (polyQ) expansion diseases. This group is composed by nine progressive and finally fatal disorders. The mutation underlying each one of these disorders is an expansion of a CAG trinucleotide repeat that encodes a polyQ tract in the respective disease proteins. This polyQ expansion causes the appearance of misfolded protein species, which ultimately lead to the formation of aggregates and neuronal loss. Although polyQ diseases present different clinical features and neuronal degeneration pattern, all these diseases have in common the fact that the associated gene products are widely expressed but affect only specific subsets of neurons. This specificity suggests that protein misfolding and its toxic outcomes may be determined by the polyQ-flanking sequences of the specific disease-associated proteins. Machado-Joseph disease (MJD) or spinocerebellar ataxia type 3 (SCA3) is the most frequent autosomal dominant ataxia worldwide. Ataxin-3 (ATXN3) is a polyQ protein and expansion of its repetitive glutamine tract causes MJD. The economic and social impact of these neurodegenerative diseases has led several researchers worldwide to investigate the pathogenesis mechanism and therapeutic strategies for polyQ diseases. Animal models, like Caenorhabditis elegans (C. elegans), have proved to be an essential tool in this field due to their importance in the development of therapeutic trials. C. elegans offers unique advantages for examining the aggregation dynamics of aggregation-prone proteins and its toxic effects on individual neurons, since the transparency of all 959 cells allows easy detection of fluorescent proteins in live animals. Despite having relatively few neurons, C. elegans display a wide array of complex behaviors and a clear link exists between the behavior and the function of neuronal subsets. In this work, we used a C. elegans model of MJD for a screening of therapeutic compounds. First, we have tested the effect of a candidate compound targeting mitochondrial toxicity: creatine (Cr). We showed that, in our C. elegans model of MJD pathogenesis, Cr food supplementation had limited effect in mutant ATXN3-mediated neuronal dysfunction and aggregation. Further experiments will be required to determine Screening of therapeutic compounds in a C. elegans model of Machado-Joseph disease: targeting mitochondria. viii the treatment effectiveness. Next, in a hypothesis-free approach, we have tested 20 compounds from an FDA-approved out-of-patent library, and the small molecules Prestw 38 and Prestw-227 significantly reduced mutant ATXN3-mediated motor impairment. In summary, with this work we have identified two compounds that reduced the percentage of mutant ATXN3 animals that present locomotion defects, and one of which showed a significant reduction in the number of aggregates per area and in the area of aggregates per area. It also made available a valuable C. elegans model/tool for drug discovery and target identification that can be very useful in future therapy development in MJD.