Mechanism of alpha-synuclein aggregate clearance by Rab7

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Parkinson's disease is characterized by aggregates of misfolded proteins, in particular alpha-synuclein. Our aim is to stop progression of Parkinson's disease by inducing clearance of alpha-synuclein aggregates.Aggregates are degraded by autophagy where pieces of cytosol are engulfed by a membrane. These autophagosomes subsequently fuse with lysosomes to degrade their content. In previous work we could show that autolysosomal degradation of alpha-synuclein aggregates is induced by overexpression of Rab7. Several Rab proteins promote aggregate clearance, but Rab7 is of particular interest since it mediates effects of PINK, parkin and LRRK2. Mutations in the genes that encode these proteins are associated with familial Parkinson's disease. The most important effector of Rab7 is FYCO1 (FYVE and coiled-coiled domain containing 1).In order to further develop our previous work into a therapeutic strategy for Parkinson's disease we will use two strategies. First, we will validate our findings from cell lines and drosophila melanogaster in models that resemble the clinical situation mor closely. We will therefore test Rab7, FYCO1 and further interventions in primary mouse neurons and in a mouse model using intracerebral injection of alpha-synuclein fibrils.In a second approach we aim to understand how Rab7-induced aggregate clearance works in order to design better manipulations for the future. Many steps and factors are involved in aggregate clerance. To focus our efforts we therefoer formulated two testable hypotheses based on our preliminary experiments:- Fusion of autophagosomes with lysosomes is the rate-limiting step of aggregate clearance. - Cholesterol transport at contact sites between autophagosomes and the ER is necessary for aggregate clearance.We will also investigate the relevance of intracellular transport and secretion for aggregate clearance.