Lysosomal storage diseases (LSD) are a group of ~ 50 genetic disorders, which mainly affect children. LSDs are clinically heterogeneous but are frequently dominated by progressive neurologic deterioration. Most patients pass away after years of lingering illness. In general, the molecular pathogenesis of LSDs is still poorly understood. To gain insight into disease mechanisms the project investigates cellular proteomic alterations sequentially induced by increasing lysosomal storage. In vivo and in vitro models of selected LSDs affecting the nervous system will be investigated. Whole cell proteomes, subcellular fractions and tissues will be analyzed using quantitative large scale mass spectrometry based proteomic techniques employing stable isotope labeling based multiplex quantification approaches (TMT, iTRAQ, SILAC) and tandem mass spectrometry on an Orbitrap Velos mass spectrometer.Three model systems focusing on glial and neuronal cells will be analyzed: a) in vitro differentiation of NG2 glia to oligodendrocytes under normal or sulfatide accumulating conditions as a model for metachromatic leukodystrophy (MLD); b) in vivo alterations occurring in the course of progressive demyelination in the peripheral nervous system of a mouse model of MLD c) a cell culture model in which consequences of increasing storage of ß-glucosylceramide in neurons will be examined as a model of Gaucher disease.Using the quantitative data, alterations in protein expression and phosphorylation will be identified, grouped and analyzed for up- and downstream interaction partners as well as biological processes they are involved in. This will be done for various levels of storage to understand the succession and possibly the hierarchy of events. These data will allow describing cellular consequences of lysosomal storage in a so far unprecedented way, will allow generating new working hypotheses, and may provide the basis for the identification of new therapeutic targets.