Structural insights into the mechanism of human NPC1L1-mediated cholesterol uptake

Niemann-Pick C1-like 1 (NPC1L1) protein plays a central role in the intestinal cholesterol absorption and is the target of a drug, ezetimibe, which inhibits NPC1L1 to reduce cholesterol absorption. Here, we present cryo-electron microscopy structures of human NPC1L1 in apo state, cholesterol-enriched state, and ezetimibe-bound state to reveal molecular details of NPC1L1-mediated cholesterol uptake and ezetimibe inhibition. Comparison of these structures reveals that the sterol-sensing domain (SSD) could respond to the cholesterol level alteration by binding different number of cholesterol molecules. Upon increasing cholesterol level, SSD binds more cholesterol molecules, which, in turn, triggers the formation of a stable structural cluster in SSD, while binding of ezetimibe causes the deformation of the SSD and destroys the structural cluster, leading to the inhibition of NPC1L1 function. These results provide insights into mechanisms of NPC1L1 function and ezetimibe action and are of great significance for the development of new cholesterol absorption inhibitors.

Automated summary

NPC1L1 protein is crucial in intestinal cholesterol absorption, and ezetimibe can inhibit NPC1L1 to reduce cholesterol uptake. Cryo-electron microscopy structures revealed that SSD in NPC1L1 responds to alterations in cholesterol levels by binding different numbers of cholesterol molecules, with ezetimibe binding causing inhibition of NPC1L1 function through deformation of the SSD.