Article

Cholesterol-regulated Translocation of NPC1L1 to the Cell Surface Facilitates Free Cholesterol Uptake

University of Texas at Dallas, Richardson, Texas, United States
Journal of Biological Chemistry (Impact Factor: 4.6). 04/2006; 281(10):6616-24. DOI: 10.1074/jbc.M511123200
Source: PubMed

ABSTRACT Although NPC1L1 is required for intestinal cholesterol absorption, data demonstrating mechanisms by which this protein facilitates the process are few. In this study, a hepatoma cell line stably expressing human NPC1L1 was established, and cholesterol uptake was studied. A relationship between NPC1L1 intracellular trafficking and cholesterol uptake was apparent. At steady state, NPC1L1 proteins localized predominantly to the transferrin-positive endocytic recycling compartment, where free cholesterol also accumulated as revealed by filipin staining. Interestingly, acute cholesterol depletion induced with methyl-beta-cyclodextrin stimulated relocation of NPC1L1 to the plasma membrane, preferentially to a newly formed "apical-like" subdomain. This translocation was associated with a remarkable increase in cellular cholesterol uptake, which in turn was dose-dependently inhibited by ezetimibe, a novel cholesterol absorption inhibitor that specifically binds to NPC1L1. These findings define a cholesterol-regulated endocytic recycling of NPC1L1 as a novel mechanism regulating cellular cholesterol uptake.

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    • "These findings, however, are in agreement with a previous study reported the relocation of NPC1L1 to the cell membrane after cholesterol depletion by methyl-β-cyclodextrin (Yu et al., 2006). This translocation was associated with an increase in cellular cholesterol uptake which was inhibited by ezetimibe (Yu et al., 2006). "
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    • "Studies on hepatoma cells have revealed that NPC1L1 is predominantly localized to intracellular components but relocated to the plasma membrane when acute cholesterol depletion via MβCD occurred (Yu et al. 2006). The NPC1L1-mediated cholesterol uptake seems to occur via a cholesterol-regulated clathrin-dependent endocytosis (Betters and Yu 2010; Yu et al. 2006). NPC1L1 mRNA has been found with highest values in the intestine with variant expression in rodent and human liver indicating species differences; other tissues such as the lung or brain also expressed NPC1L1 but at a relatively low level (Davies et al. 2000, 2005; Pramfalk et al. 2011). "
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