Understanding Mechanisms of a-synuclein pathology

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PROJECT SUMMARY - PROJECT 2: UNDERSTANDING MECHANISMS OF α -SYNUCLEIN PATHOLOGY Genetic and biochemical abnormalities of α-synuclein are directly implicated in the pathogenesis of familial and sporadic forms of Parkinson's disease (PD). The underlying mechanisms of α-synuclein-induced neurodegeneration are poorly understood. Familial mutations in α-synuclein as well as oxidative and nitrosative stress contribute to α-synuclein pathology, in part, via enhanced oligomerization, fibrillation and aggregation. During the last funding cycle, we showed in collaboration with Project 1 that activation of the non- receptor tyrosine kinase, c-Abl may contributes to the pathogenesis of PD. From these studies emerged the exciting preliminary findings that c-Abl phosphorylates α-synuclein at tyrosine 39. However, the potential roles of tyrosine 39 α-synuclein and c-Abl activation in pathogenesis of PD has not been explored. We will study the roles of phosphorylation of α-synuclein at tyrosine 39 and c-Abl activation in the death of DA neurons due to α- synuclein, as well as, their roles in aggregation of α-synuclein in vitro and in vivo. With the Proteomics Core D, the Clinical Core B and the Neuropathology Core C, we will investigate whether the levels of phosphorylation of α-synuclein at tyrosine 39 can serve as a progression and/or pathologic maker of α-synuclein-induced neurodegeneration and of α-synuclein pathology in human PD. For these studies, we will assess the levels of tyrosine 39 phosphorylation of α-synuclein and the activation state of c-Abl in human A53T α-synuclein transgenic model, the adeno-associated virus-WT or A53T α-synuclein model with DA neuron loss, and human post-mortem tissues from PD patients via a phosphospecific tyrosine 39 α-synuclein antibody and MRM (Multiple Reaction Monitoring) mass spectrometry. Cell-to-cell transmission of misfolded α-synuclein may contribute to the degeneration of DA neurons in sporadic PD and the mechanisms accounting for the recruitment and the corruption of endogenous α-synuclein into fibrils are not known. Since our preliminary data suggests that tyrosine 39 phosphorylation of α-synuclein by c-Abl promotes the fibrillation of α-synuclein, we will study the ability of WT versus phospho-deficient Y39F and phospho-mimetic α-synuclein Y39E, as well as c-Abl deficiency in cell-to-cell transmission and degeneration of DA neurons in the α-synuclein PFF model of sporadic PD. Finally, we will explore proteomic changes induced by α-synuclein PFFs in degenerating DA neurons via advanced spike-in mass spectrometry approaches combined with SILAM (Stable Isotope Labeling in Mammals). These studies will provide new mechanistic insights into the pathogenesis of α-synuclein induced neurodegeneration and may lead to the development of novel therapeutic targets and biomarkers for the treatment of PD.