Differential uptake and storage of dehydroergosterol (DHE) as a marker for Niemann Pick Type C: Implications for drug screening and mechanistic studies

Niemann Pick Type C (NPC) is a cholesterol storage disorder caused by mutations the proteins NPC1 or NPC2 leading to liver dysfunction, neurodegeneration and premature death. Cyclodextrins (CDs) have been shown to mobilize cholesterol and alleviate NPC symptoms. We are using the fluorescent cholesterol analog, dehydroergosterol (DHE), to develop a simple phenotypic screening assay to find new potential treatments for this disease and to gain a better understanding of the mechanism of CDs. DHE is taken up, trafficked, processed and stored very similarly to cholesterol. We have observed that Chinese hamster ovary cells with an NPC1 mutation accumulate more DHE than wild‐type cells and that a 24 hour pre‐incubation with CD eliminates this difference. The DHE signal can be used in screening assays of compound libraries to identify novel chemicals that correct for the NPC trafficking defect. The mechanism by which CDs mobilize cholesterol in NPC cells is not clear and the DHE assay will be useful in exploring biochemical and molecular events involved. The assay can also be used to explore the potential contributions of membrane cholesterol depletion in the mobilization of accumulated cholesterol. These studies will be useful in identifying compounds that correct the NPC deficit and in exploring new mechanisms of action for potential therapeutics. Funding: Ara Parseghian Medical Research Foundation.