Dissertação para obtenção do Grau de Mestre em
Genética Molecular e BiomedicinaAutosomal recessive juvenile Parkinson disease (AR-JP) is mainly caused by mutations in PARK2. AR-JP presents with rigidity, bradykinesia and resting tremor, usually before age 40 years.
Large PARK2 deletions account for 50% of the mutations identified in patients with AR-JP of Portuguese origin. The PARK2 gene encodes parkin, an E3 ubiquitin ligase, an important part of the cellular machinery that covalently tags target proteins with ubiquitin for degradation by the ubiquitinproteasome system (UPS), the main cellular protein degradation system responsible for targeted degradation of damaged and misfolded proteins.
This project aims were: determine the breakpoints of the deletion found in Portuguese patients in order to identify the genomic mechanisms underlying these gene rearrangements and to explore the pathogenic mechanisms of parkin mutations by assessing the dynamics of formation and degradation
of aggregates by UPS and also by determining its effects in the UPS degradation capacity and its relation with neuronal death.
A successful approach was developed to narrow the deletion breakpoint intronic position. Cellular models expressing wild-type and mutant parkin were developed and characterized regarding mRNA and protein expression, as well as, aggregate formation, cell viability and proteasome activity.
Our data show that the different studied mutations do not have an impact on cell viability, although resulted in differences in the number of cell with aggregates for the cells expressing N52MfsX29, L358RfsX77 and R275W mutants as well as in the number of aggregates present in each cell. We were also able to show that proteasome inhibition has as impact both in cell viability and in
aggregate formation, resulting in decreased viability and increased aggregate formation.
The study of the cellular mechanisms resulting in neuronal dysfunction is crucial for the identification of potential therapeutic targets for Parkinson disease
