Inactivation of NPC1L1 Causes Multiple Lipid Transport Defects and Protects against Diet-induced Hypercholesterolemia

Department of Human Genetics, Mount Sinai School of Medicine, New York, New York 10029, USA.
Journal of Biological Chemistry (Impact Factor: 4.6). 05/2005; 280(13):12710-20. DOI: 10.1074/jbc.M409110200
Source: PubMed

ABSTRACT NPC1L1, a recently identified relative of Niemann-Pick C1, was characterized to determine its subcellular location and potential
function(s). NPC1L1 was highly expressed in HepG2 cells and localized in a subcellular vesicular compartment rich in the small
GTPase Rab5. mRNA expression profiling revealed significant differences between mouse and man with highest expression found
in human liver and significant expression in the small intestine. In contrast, liver expression in mouse was extremely low
with mouse small intestine exhibiting the highest NPC1L1 expression. A mouse knock-out model of NPC1L1 was generated and revealed
that mice lacking a functional NPC1L1 have multiple lipid transport defects. Surprisingly, lack of NPC1L1 exerts a protective
effect against diet-induced hyperlipidemia. Further characterization of cell lines generated from wild-type and knock-out
mice revealed that in contrast to wild-type cells, NPC1L1 cells exhibit aberrant plasma membrane uptake and subsequent transport
of various lipids, including cholesterol and sphingolipids. Furthermore, lack of NPC1L1 activity causes a deregulation of
caveolin transport and localization, suggesting that the observed lipid transport defects may be the indirect result of an
inability of NPC1L1 null cells to properly target and/or regulate caveolin expression.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The known mechanism by which orlistat decreases the absorption of dietary cholesterol is by inhibition of intestinal lipases. The aim of this study was to investigate the ability of orlistat to limit cholesterol absorption by inhibition of the cholesterol transport protein Niemann-Pick C1-like 1 (NPC1L1) as another mechanism of action. In situ rat intestinal perfusion studies were conducted to study the effect of orlistat on jejunal cholesterol absorption. Inhibition kinetic parameters were calculated from in vitro inhibition studies using Caco2 and NPC1L1 transfected cell lines. The in situ studies demonstrated that intestinal perfusion of orlistat (100µM) was able to reduce cholesterol absorption by three-fold when compared to control (i.e. in the absence of orlistat, P<0.01). In vitro studies using Caco2 cells demonstrated orlistat to reduce the cellular uptake of cholesterol by 30%. Additionally, orlistat reduced the cellular uptake of cholesterol in dose dependent manner in NPC1L1 transfected cell line with an IC50=1.2µM. Lineweaver-Burk plot indicated a noncompetitive inhibition of NPC1L1 by orlistat. Beside the already established mechanism by which orlistat reduces the absorption of cholesterol, we demonstrated for the first time that orlistat limits cholesterol absorption by the inhibition of NPC1L1 transport protein. Copyright © 2015. Published by Elsevier B.V.
    European journal of pharmacology 06/2015; 762. DOI:10.1016/j.ejphar.2015.05.060 · 2.68 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Cholesterol is an essential component of eukaryotic plasma membranes and plays an important role in membrane organization and signaling processes. It is the major lipid component of detergent resistant caveolin-1 containing rafts which previously had been reported as a platform for nerve growth factor (NGF) signaling in oligodendrocytes (OL). Surprisingly, a knockdown of caveolin-1 attenuated the process formation of OL (Schmitz et al. J Neurosci Res 88:572-588, 2010), for which a loss of cholesterol could be responsible. In the present report, we could show that a caveolin-1 knockdown resulted in an elevation of cellular cholesterol level; it may indicate an important role of caveolin-1 in cholesterol trafficking to the plasma membrane. Treatment with exogenous PEG cholesterol, which was incorporated to the plasma membrane, supported oligodendroglial process formation, in particular when OL were stimulated by NGF. In this context we have found that OL express NPC1L1 (Niemann-Pick disease type C1-Like 1) which could modulate cholesterol uptake. In contrast, depletion of membrane-bound cholesterol diminished NGF-induced process formation concomitant with a reduced activity of p42/44 mitogen-activated protein kinases.
    Journal of Molecular Neuroscience 06/2012; 49(3). DOI:10.1007/s12031-012-9833-2 · 2.76 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Ezetimibe stimulates faecal neutral sterol (FNS) excretion in mice, which cannot be explained by cholesterol absorption inhibition alone. We investigated whether these effects are mediated via the sterol exporter ATP binding cassette transporter G8 (abcg8). Ezetimibe increased FNS excretion 2.7-fold in WT mice and 1.5-fold in abcg8(-/-) mice, without affecting biliary cholesterol secretion. Daily FNS excretion exceeded the sum of dietary cholesterol intake and biliary secretion by about 60%. Ezetimibe enhanced this 'extra' FNS excretion by 3.5-fold and 1.5-fold in wildtype (WT) and abcg8(-/-) mice, respectively. Ezetimibe stimulates fecal sterol excretion of non-biliary and non-dietary origin, probably through stimulation of trans-intestinal cholesterol excretion. We show that this effect depends on intact abcg8 function.
    FEBS letters 08/2010; 584(16):3625-8. DOI:10.1016/j.febslet.2010.07.035 · 3.34 Impact Factor