Pilot Project 6 (2020)

Identifying regulators of late endosomal cholesterol homeostasis and post-endosomal trafficking routes using proximity proteomics

Late endosomes and lysosomes control intracellular trafficking routes by monitoring the cellular homeostasis of cholesterol. Cholesterol is taken up by cells via endocytosis and is distributed from late endosomal/lysosomal compartments to other cellular destinations. The regulation of the late endosomal cholesterol content is of central importance to several cellular processes including the control of virus infection and endothelial cell activation during inflammation. Increasing late endosomal cholesterol levels is part of the innate immune response to reduce influenza A virus infection by inhibiting viral escape from the endosome. At the same time, late endosomal cholesterol accumulation impairs endothelial cell activation by blocking protein trafficking from late endosomal compartments to Weibel-Palade Bodies (WPB) endothelial cell-specific secretory granules. To further investigate the impact of late endosomal cholesterol homeostasis on downstream trafficking routes, we plan to acquire and compare the associated proteomes of late endosomes and WPBs in control cells and cells with pharmacologically inhibited late endosomal cholesterol efflux via proximity-dependent labeling.