title: Localization and role of NPC1L1 in cholesterol absorption in human intestine.
abstract: Recent studies have documented the presence of Niemann-Pick C1-Like 1 (NPC1L1) in the small intestine and its capacity to transport cholesterol in mice and rats. The current investigation was undertaken to explore the localization and function of NPC1L1 in human enterocytes. Cell fractionation experiments revealed an NPC1L1 association with apical membrane of the enterocyte in human jejunum. Signal was also detected in lysosomes, endosomes, and mitochondria. Confirmation of cellular NPC1L1 distribution was obtained by immunocytochemistry. Knockdown of NPC1L1 caused a decline in the ability of Caco-2 cells to capture micellar [(14)C]free cholesterol. Furthermore, this NPC1L1 suppression resulted in increased and decreased mRNA levels and activity of HMG-CoA reductase, the rate-limiting step in cholesterol synthesis, and of ACAT, the key enzyme in cholesterol esterification, respectively. An increase was also noted in the transcriptional factor sterol-regulatory element binding protein that modulates cholesterol homeostasis. Efforts were devoted to define the impact of NPC1L1 knockdown on other mediators of cholesterol uptake. RT-PCR evidence is presented to show the significant decrease in the levels of scavenger receptor class B type I (SR-BI) with no changes in ABCA1, ABCG5, and cluster determinant 36 in NPC1L1-deficient Caco-2 cells. Together, our data suggest that NPC1L1 contributes to intestinal cholesterol homeostasis and possibly cooperates with SR-BI to mediate cholesterol absorption in humans.
authors.affiliation: Department of Nutrition, CHU-Sainte-Justine, University of Montreal, Montreal, Quebec H3T 1C5, Canada.
authors.forename: Alain Théophile
authors.initials: AT
authors.lastname: Sané
authors.forename: Daniel
authors.initials: D
authors.lastname: Sinnett
authors.forename: Edgard
authors.initials: E
authors.lastname: Delvin
authors.forename: Moise
authors.initials: M
authors.lastname: Bendayan
authors.forename: Valérie
authors.initials: V
authors.lastname: Marcil
authors.forename: Daniel
authors.initials: D
authors.lastname: Ménard
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Beaulieu
authors.forename: Emile
authors.initials: E
authors.lastname: Levy
mesh_terms: D000328:Adult; D018938:Caco-2 Cells; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D007408:Intestinal Absorption / Q000502:physiology*; D007421:Intestine, Small / Q000201:enzymology / Q000378:metabolism*; D007583:Jejunum / Q000201:enzymology / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008875:Middle Aged; D013050:Spectrometry, Fluorescence; D002785:Sterol O-Acyltransferase / Q000378:metabolism
chemical_list: D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C410800:NPC1L1 protein, human; D002784:Cholesterol; D002785:Sterol O-Acyltransferase; C493492:sterol O-acyltransferase 1