Inhibition of Niemann-Pick-type C1-like1 by ezetimibe activates autophagy in human hepatocytes and reduces mutant α1-antitrypsin Z deposition.
Autophagy can degrade aggregate-prone proteins, but excessive autophagy can have adverse effects. It would be beneficial if autophagy could be enhanced in a cell type-specific manner, but this has been difficult because the basic mechanism of autophagy is common. In the present study we found that inhibition of Niemann-Pick-type C1-like 1 (NPC1L1) by ezetimibe activates autophagy only in hepatocytes and small intestinal epithelia, but not in other cells. Ezetimibe induced accumulation of free cholesterol in the late endosome/lysosome and increased partitioning of a Ragulator component, LAMTOR1, in rafts. The latter change led to down-regulation of mammalian target of rapamycin (mTOR)C1 activity by decreasing mTOR recruitment to the late endosome/lysosome and activated autophagy. A primary effect of ezetimibe was found to be a decrease of free cholesterol in the plasma membrane, because all the results caused by ezetimibe were suppressed by supplementation of cholesterol as a methyl-β-cyclodextrin complex. By enhancing autophagy in human primary hepatocytes with ezetimibe, insoluble mutant α1-antitrypsin Z was reduced significantly.


CONCLUSIONS
Inhibition of NPC1L1 by ezetimibe activates autophagy in human hepatocytes by modulating cholesterol homeostasis. Ezetimibe may be used to ameliorate liver degeneration in α1-antitrypsin deficiency.
Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, 466-8550, Japan; Department of Gastroenterology and Hepatology, Nagoya University Graduate School of Medicine, Nagoya, 466-8550, Japan.
Takeshi
T
Yamamura
Yuki
Y
Ohsaki
Michitaka
M
Suzuki
Yuki
Y
Shinohara
Tsuyako
T
Tatematsu
Jinglei
J
Cheng
Masato
M
Okada
Naoki
N
Ohmiya
Yoshiki
Y
Hirooka
Hidemi
H
Goto
Toyoshi
T
Fujimoto
D000924:Anticholesteremic Agents / Q000494:pharmacology; D001343:Autophagy / Q000187:drug effects*; D001384:Azetidines / Q000494:pharmacology*; D002352:Carrier Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D002784:Cholesterol / Q000378:metabolism; D000069438:Ezetimibe; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008247:Lysosomes / Q000378:metabolism; D021962:Membrane Microdomains / Q000378:metabolism; D008565:Membrane Proteins / Q000037:antagonists & inhibitors* / Q000187:drug effects; D026901:Membrane Transport Proteins; D009154:Mutation / Q000235:genetics*; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D000515:alpha 1-Antitrypsin / Q000235:genetics* / Q000378:metabolism*
D000924:Anticholesteremic Agents; D001384:Azetidines; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; C544374:LAMTOR1 protein, human; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C410800:NPC1L1 protein, human; D000515:alpha 1-Antitrypsin; D002784:Cholesterol; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D000069438:Ezetimibe