Basic—Liver, Pancreas, and Biliary TractNPC2 Regulates Biliary Cholesterol Secretion via Stimulation of ABCG5/G8-Mediated Cholesterol Transport
Section snippets
Adenoviruses
Adenoviruses expressing the short hairpin RNA sequence for knockdown of the mouse Npc2 gene (accession no. BC007190) (Ad-shNpc2 #1 and #2) and adenoviruses expressing human NPC2 complementary DNA (cDNA) (accession no. BC002532) attached to a Myc tag and 6×His tag sequences (Ad-NPC2-Myc-His), human ABCG5 cDNA (accession no. NM022436) attached to a Myc tag sequence (Ad-Myc-ABCG5), and human ABCG8 cDNA (accession no. NM022437) attached to an HA tag sequence (Ad-HA-ABCG8) were constructed and
Biliary Cholesterol Secretion Is Reduced in Hepatic Npc2-Knockdown Mice
To test the hypothesis that biliary NPC2 affects cholesterol secretion into bile, Npc2-knockdown mice were created by intravenous administration of adenoviruses (Ad-shNpc2 #1 and Ad-shNpc2 #2) expressing short hairpin RNA against Npc2. Following infection with Ad-shNpc2 #1 and #2, the hepatic expression of Npc2 mRNA was significantly reduced to 53% and 19% of basal levels, respectively, whereas expression of Npc2 mRNA in the intestine and brain was not affected (Figure 1A). Corresponding to the
Discussion
The major contribution of the present study was to identify the physiologic function of biliary NPC2 as a positive regulator of cholesterol secretion into bile, and this novel function of NPC2 is accounted for by the stimulation of ABCG5/G8-mediated cholesterol efflux. It is known that the 2 half ABC transporters, ABCG5 and ABCG8, which act on the bile canalicular membrane,23 are essential for the biliary secretion of cholesterol; Abcg5/g8-deficient mice have a significantly reduced biliary
Acknowledgments
Yoshihide Yamanashi and Tappei Takada contributed equally to this study.
References (41)
- et al.
Absorption, metabolism, and serum concentrations of cholesterol in vegetarians: effects of cholesterol feeding
Am J Clin Nutr
(1994) - et al.
Regulation of ATP-binding cassette sterol transporters ABCG5 and ABCG8 by the liver X receptors alpha and beta
J Biol Chem
(2002) - et al.
The sterol transporting heterodimer ABCG5/ABCG8 requires bile salts to mediate cholesterol efflux
FEBS Lett
(2007) - et al.
Intracellular trafficking of Niemann-Pick C proteins 1 and 2: obligate components of subcellular lipid transport
Biochim Biophys Acta
(2004) - et al.
A porcine homolog of the major secretory protein of human epididymis, HE1, specifically binds cholesterol
Biochim Biophys Acta
(1999) - et al.
Uncoupling of biliary phospholipid and cholesterol secretion in mice with reduced expression of mdr2 P-glycoprotein
J Lipid Res
(1996) - et al.
NPC2, the protein deficient in Niemann-Pick C2 disease, consists of multiple glycoforms that bind a variety of sterols
J Biol Chem
(2006) - et al.
Hepatic overexpression of murine Abcb11 increases hepatobiliary lipid secretion and reduces hepatic steatosis
J Biol Chem
(2004) - et al.
Homozygous disruption of the murine mdr2 P-glycoprotein gene leads to a complete absence of phospholipid from bile and to liver disease
Cell
(1993) - et al.
Abcg5/8 independent biliary cholesterol excretion in Atp8b1-deficient mice
Gastroenterology
(2008)
Control analysis of biliary lipid secretion
J Theor Biol
The molecular and metabolic basis of biliary cholesterol secretion and gallstone disease
Front Biosci
Hepatic cholesterol transport from plasma into bile: implications for gallstone disease
Curr Opin Lipidol
Gallbladder cancer: a morphological and molecular update
Histopathology
Accumulation of dietary cholesterol in sitosterolemia caused by mutations in adjacent ABC transporters
Science
Niemann-Pick C1 Like 1 protein is critical for intestinal cholesterol absorption
Science
Disruption of Abcg5 and Abcg8 in mice reveals their crucial role in biliary cholesterol secretion
Proc Natl Acad Sci U S A
Hepatic Niemann-Pick C1-like 1 regulates biliary cholesterol concentration and is a target of ezetimibe
J Clin Invest
HNF4alpha is a crucial modulator of the cholesterol-dependent regulation of NPC1L1
Pharm Res
Niemann-Pick C1-like 1 overexpression facilitates ezetimibe-sensitive cholesterol and beta-sitosterol uptake in CaCo-2 cells
J Pharmacol Exp Ther
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Conflicts of interest The authors disclose no conflicts.
Funding Supported by grants from the Ministry of Education, Culture, Sports, Science and Technology of Japan and Grant-in-Aid for Scientific Research on Innovative Areas HD-physiology (22136015).