Multiple system atrophy (MSA) is a progressive, degenerative neurological disorder characterized by parkinsonism, ataxia & dysautonomia. The cardinal pathological feature of MSA is the presence of glial cytoplasmic inclusions composed of alpha-synuclein (SYN) in oligodendrocytes. Recent studies suggest that abnormal SYN accumulation in neurons & glia leads to cellular dysfunction & neurodegeneration. During the previous funding period we developed in vitro & in vivo models of MSA showing that mitochondrial damage & hyperphosphorylated SYN aggregate generation may contribute to the pathogensis of MSA. However, mechanisms by which these pathways promote oligodendrogial dysfunction & neurodegeneration are unclear. In this renewal we will investigate the role of mitochondrial dysfunction in SYN phosphorylation & toxicity. Our central hypothesis is that oxidative stress due to mitochondrial dysfuntion may promote G-protein coupled receptor kinase (GRK) activation & toxic SYN phosphorylation. The main objective is to investigate neurodegeneration in MSA-like SYN transgenic (tg) models to determine if reducing SYN accumulation represents a therapeutic strategy for MSA. Aim 1. In order to determine the role of hyperphosphorylated SYN accumulation in oligodendrocj^es in the mechanisms of neurotoxicity, we will analyze SYN accumulation & neurodegeneration in myelin basic protein (MBP)-SYN tg mice expressing wild-type (wt) human SYN or a nonphosphorylatable SYN mutant (S129A). MBP-SYNwt tg mice will be crossed with GRK2- or GRKS-deficient mice & MBP-SYNwt tg mice & MBP-SYN(S129A) tg mice will receive intra-cerebral infections with lentivirus expressing GRK2 or GRK5 under a oligodendroglial specific promoter (MBP). Aim 2. In order to determine the role of mitochondrial dysfunction & oxidative stress on GRK activation & SYN phosphorylation, MBP-SYN (wt and S129A) mice & oligodendroglial cells will be challenged with 3- nitropropionic acid. Aim 3. In order to determine if neuronal impairments in MSA models can be ameliorated by reducing SYN aggregation or inhibiting GRKs, MBP-SYN wt tg mice will be treated with rifampicin or GRK blockers. Behavioral performance, neurodegeneration, SYN oligomerization & phosphorylation & GRK activity will be assessed

Our studies will shed light on the pathogenesis of MSA, highlighting key mechanisms underiying the role of mitochndrial dysfunction and oxidative stress as they relate to SYN phosphorylation, aggregation and toxicity. The studies with rifampicin and GRK blockers will help identify new strategies for the prevention and treatment of MSA.