ROLE OF THE UBIQUITIN/PROTEASOME PATHWAY IN THE DEGENERATION OF MOTOR NEURONS IN IN VITRO AND IN VIVO MODELS OF FAMILIAL AMYOTROPHIC LATERAL SCLEROSIS

Accumulation of abnormally misfolded proteins, that resist degradation and impair neuronal cell functioning, is a hallmark of most neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS). On the basis of recent findings in Huntington’s disease, hereditary ataxias and Kennedy's disease (a genetic form of bulbar and spinal muscular atrophy), we hypothesize that formation of aggregates in ALS is largely the result of an impairment of the ubiquitin-proteasome system of protein degradation. To this end, we will investigate the presence of proteasome dysfunction in transgenic mice expressing mutant human superoxide dismutase 1 (SOD1), a free radical scavenging enzyme that is mutated in a subset of familial ALS cases. Morphological and biochemical analyses will be carried out to characterize the composition of the aggregates and their interaction with proteasome subunits, and to evaluate proteasomal dysfunction by histopathological techniques and by in vitro assays. The results will be validated and extended by parallel studies on an immortalized motor neuron cell line overexpressing mutant SOD1. Furthermore, in vitro and in vivo treatments with proteasome inhibitors will be performed to understand whether proteasome impairment will exacerbate the motor neuron disease. These experiments should allow us to clarify the role of proteasome dysfunction in motor neuron degeneration, and to define novel therapeutic strategies for ALS, based on modulation of proteasome activity.