Protein Misfolding and Aggregation in Neurodegeneration: In Vitro And In Vivo Study Cases

Neurodegenerative diseases are nowadays increasing in incidence and widely distributed around the world. Despite those disorders show very different symptoms and morbidity, intracellular and extracellular protein misfolding and accumulation appears as a common pathological pathway. In the present thesis work I analyzed two cases of toxic protein deposition involved in ALS and AD. First, I looked at SOD1-G93A mutant protein, whose neuronal deposit is associated to familial and sporadic ALS. The mitochondrial porin VDAC1 has been proposed as a binding target of SOD1 mutant forms to mitochondria. By affinity studies we found that VDAC1 protein specifically binds SOD1-G93A but not wild type SOD1. Notably, it is known that the N-Terminal end of Hexokinase 1 (N-HK1) interacts with VDAC1: thus, we produced a synthetic peptide corresponding to the first 11 aa of human HK1 and tested its action as a potential interfering molecule between VDAC1/SOD1-G93A bond. Both in a protein-protein interaction and in a protein mitochondrial interaction we obtained a decrease of VDAC1/SOD1-G93A binding with respect of the increased N-HK1 peptide concentration. Summarizing, SOD1-G93A binds VDAC1 and impairs HK1 binding and our results suggest for N-HK1 peptide a neuroprotective potential in ALS patients. The second part of my thesis work was focused on Amyloid and tau protein accumulation in 3xTg-AD mice. In order to study neuropathology and cognitive deficits in (AD), several transgenic models of AD have been identified. Accumulation of Abeta and fibrillary tangles as well as impairments in working and learning memory are age-related hallmark of AD pathology. To produce a progressive characterization of Abeta and tau pathology in 3xTg-AD mice we aged female mice at 2, 6, 12 and 20 months of age. We tested mice in a behavioral assay named Morris Water Maze (MWM) and we used in vitro biochemical assays, to observe Abeta soluble and insoluble fraction as well as tau phosphorylation in both cortex and hippocampus of 3xTg-AD mice. Our data on MWM demonstrate a progressive impairment in learning with a strongly significant difference between 3xTg-AD mice and controls, from 6 months of age. Notably, we also found a progressive increase in both soluble and insoluble Abeta40 and Abeta42, an age dependent tau hyperphosphorylation at specific AD linked phospho-sites, and an intense glial reactivity. Overall, our data confirm that female 3xTg-AD mice consistently show AD-like pathology, therefore this transgenic mouse model can be used as an extremely powerful tool to investigate pathogenic mechanisms underlying Alzheimer s disease.