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Elife. 2015 Dec 8;4. pii: e12177. doi: 10.7554/eLife.12177.

Identification of NPC1 as the target of U18666A, an inhibitor of lysosomal cholesterol export and Ebola infection.

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Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, United States.
Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States.


Niemann-Pick C1 (NPC1) is a lysosomal membrane protein that exports cholesterol derived from receptor-mediated uptake of LDL, and it also mediates cellular entry of Ebola virus. Cholesterol export is inhibited by nanomolar concentrations of U18666A, a cationic sterol. To identify the target of U18666A, we synthesized U-X, a U18666A derivative with a benzophenone that permits ultraviolet-induced crosslinking. When added to CHO cells, U-X crosslinked to NPC1. Crosslinking was blocked by U18666A derivatives that block cholesterol export, but not derivatives lacking blocking activity. Crosslinking was prevented by point mutation in the sterol-sensing domain (SSD) of NPC1, but not by point mutation in the N-terminal domain (NTD). These data suggest that the SSD contains a U18666A-inhibitable site required for cholesterol export distinct from the cholesterol-binding site in the NTD. Inasmuch as inhibition of Ebola requires 100-fold higher concentrations of U18666A, the high affinity U16888A-binding site is likely not required for virus entry.


Niemann-Pick C1; U18666A; biochemistry; cell biology; cholesterol transport; crosslinking; endosomes/lysosomes; human; sterol-sensing domain

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