N-terminal domain of the cholesterol transporter Niemann-Pick C1-like 1 (NPC1L1) is essential for α-tocopherol transport.
Both cholesterol and α-tocopherol are essential lipophilic nutrients for humans and animals. Although cholesterol in excess causes severe problems such as coronary heart disease, it is a necessary component of cell membranes and is the precursor for the biosynthesis of steroid hormones and bile acids. Niemann-Pick C1-like 1 (NPC1L1) is a cholesterol transporter that is highly expressed in the small intestine and liver in humans and plays an important role in cholesterol homeostasis. Cholesterol promotes NPC1L1 endocytosis, which is an early step in cholesterol uptake. Furthermore, α-tocopherol is the most active form of vitamin E, and sufficient amounts of vitamin E are critical for health. It has been reported that NPC1L1 mediates α-tocopherol absorption; however, the mechanisms underlying this process are unknown. In this study, we found that treatment of cells that stably express NPC1L1-GFP with α-tocopherol promotes NPC1L1 endocytosis, and the NPC1L1 inhibitor, ezetimibe, efficiently prevents the α-tocopherol-induced endocytosis of NPC1L1. Cholesterol binding to the N-terminal domain (NTD) of NPC1L1 (NPC1L1-NTD) is essential for NPC1L1-mediated cholesterol absorption. We found that α-tocopherol competitively binds NPC1L1-NTD with cholesterol. Furthermore, when cells stably expressed NPC1L1ΔNTD-GFP, α-tocopherol could not induce the endocytosis of NPC1L1ΔNTD. Taken together, these results demonstrate that NPC1L1 recognizes α-tocopherol via its NTD and mediates α-tocopherol uptake through the same mechanism as cholesterol absorption.
Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 985-1 Sanzo, Higashimura-cho, Fukuyama, Hiroshima 729-0292, Japan. Electronic address: kamishikiryou@fupharm.fukuyama-u.ac.jp.
Jun
J
Kamishikiryo
Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 985-1 Sanzo, Higashimura-cho, Fukuyama, Hiroshima 729-0292, Japan.
Misaki
M
Haraguchi
Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 985-1 Sanzo, Higashimura-cho, Fukuyama, Hiroshima 729-0292, Japan.
Shunsuke
S
Nakashima
Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 985-1 Sanzo, Higashimura-cho, Fukuyama, Hiroshima 729-0292, Japan.
Yuka
Y
Tasaka
Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 985-1 Sanzo, Higashimura-cho, Fukuyama, Hiroshima 729-0292, Japan.
Hiroe
H
Narahara
Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 985-1 Sanzo, Higashimura-cho, Fukuyama, Hiroshima 729-0292, Japan.
Narumi
N
Sugihara
Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 985-1 Sanzo, Higashimura-cho, Fukuyama, Hiroshima 729-0292, Japan.
Tetsuya
T
Nakamura
Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 985-1 Sanzo, Higashimura-cho, Fukuyama, Hiroshima 729-0292, Japan.
Tetsuo
T
Morita
D000818:Animals; D000924:Anticholesteremic Agents / Q000494:pharmacology; D001667:Binding, Competitive; D001692:Biological Transport; D018938:Caco-2 Cells; D045744:Cell Line, Tumor; D002784:Cholesterol / Q000378:metabolism* / Q000494:pharmacology; D004705:Endocytosis / Q000187:drug effects; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D000069438:Ezetimibe / Q000494:pharmacology; D015870:Gene Expression; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins; D010957:Plasmids / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D000072417:Protein Domains; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D024502:alpha-Tocopherol / Q000378:metabolism*
D000924:Anticholesteremic Agents; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C410800:NPC1L1 protein, human; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D002784:Cholesterol; D000069438:Ezetimibe; D024502:alpha-Tocopherol
Alpha-tocopherol; Cholesterol; Ezetimibe; Niemann–Pick C1-like 1; Vitamin E