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

Abstract

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.

Regulation of cholesterol homeostasis in health and diseases: from mechanisms to targeted therapeutics

“… 82 Recently, Hu et al found that SSD in NPC1L1 can respond to cholesterol concentrations by binding different amounts of cholesterol. 83 In addition, the effective cholesterol uptake by NPC1L1 depends on its dimerization. 84 Based on the crucial role of NPC1L1 in cholesterol uptake, ezetimibe has been developed and used clinically as an inhibitor of hypercholesterolemia, and other NPC1L1 inhibitors are being developed.…”

The role of NPC1L1 in cancer

“…As a homolog of NPC1, NPC1L1 likewise possesses a transmembrane domain with 13 cysteines and three major luminal structural domains in the extracellular area, the N-terminal domain (NTD), the middle domain (MLD), and the cysteine-rich domain (CTD). Thirteen molecules of membrane-embedded transmembrane helices (TM) make up the transmembrane domain (TMD) ( Hu et al, 2021 ). The SSD domain is widely distributed in several regulatory protein substructures that are closely related to cholesterol metabolisms, such as NPC1, sterol regulatory element-binding protein cleavage activating protein (SCAP), and hydroxymethyl glutaryl-CoA reductase (HMG-CoA reductase) ( Yang et al, 2012 ).…”

“…Huang et al studied the structure of NPC1L1 derived from Rattus . Miao Qinghu et al ( Hu et al, 2021 ) and Long et al (2021 ) studied the structure of human-derived NPC1L1. Their findings demonstrated a general similarity between the three-dimensional architecture of mouse and human NPC1L1.…”

Phytosterols in human health: friends or foes?

“…PS, as well as cholesterol, are quickly uptaken by the enterocyte (Igel et al, 2003). Due to its structural similarity to cholesterol, PS can be uptaken by enterocytes through the Niemann-Pick C1-like 1 (NPC1L1) multi-pass transporter (Hu et al, 2021). Between these two types of molecules, plant sterol is better absorbed than stanol (Igel et al, 2003), suggesting that their chemical structure play an important role.…”