TY - JOUR
T1 - ATP-Binding Cassette Transporter A Subfamily 8 Is a Sinusoidal Efflux Transporter for Cholesterol and Taurocholate in Mouse and Human Liver
AU - Sasaki, Kazunari
AU - Tachikawa, Masanori
AU - Uchida, Yasuo
AU - Hirano, Satoshi
AU - Kadowaki, Fumito
AU - Watanabe, Michitoshi
AU - Ohtsuki, Sumio
AU - Terasaki, Tetsuya
N1 - Funding Information:
This study was supported in part by Grants-in-Aid from the Japanese Society for the Promotion of Science (JSPS) for Scientific Research (A) [KAKENHI: 24249011] and Scientific Research (C) [KAKENHI: 16K08364], and grants from the Mochida Memorial Foundation for Medical and Pharmaceutical Research, and the Takeda Science Foundation. We also thank A. Niitomi and N. Handa for secretarial assistance.
Publisher Copyright:
© 2018 American Chemical Society.
PY - 2018/2/5
Y1 - 2018/2/5
N2 - The ATP-binding cassette (ABC) transporter A subfamily 8 (ABCA8) belongs to the ABCA6-like transporters subgroup, which is distinct from the ABCA1-like subgroup in the ABCA family. The expression and function of the short-size human ABCA8 lacking one of the two ATP-binding domains for ATP hydrolysis, which are regularly present in the other ABCA transporters, have been reported. However, the functional differences between the short-size human ABCA8 and full-size human ABCA8, which has the two ATP-binding domains, remain unknown. The purpose of the present study was to clarify the tissue expression profiles of ABCA6-like and ABCA1-like subgroup transporters and the functional characteristics of ABCA8 in mouse and human. The tissue distribution of mouse ABCA (mABCA) transporter protein and the changes in mABCA8 protein expression levels in a mouse model of obstructive cholestasis were elucidated by means of quantitative targeted absolute proteomics (QTAP). The transport characteristics were clarified in a HEK293 cell line overexpressing full-size ABCA8 protein. QTAP and immunohistochemical analyses revealed that mABCA transporters exhibited the distinct protein expression patterns in the tissues, and mABCA8b, its mouse orthologue, was abundant in the liver and predominantly distributed in sinusoidal membranes of the hepatocytes. Further, protein expression of mABCA8b was decreased in the mouse cholestasis liver. Changes of mABCA8b expression level in cholestasis were similar to those of mABCA1, a sinusoidal cholesterol efflux transporter. Uptake and efflux assays showed that ABCA8 mediates efflux of [ 3 H]cholesterol and [ 3 H]taurocholate, while it showed no significant efflux activity for [ 3 H]estrone sulfate, [ 3 H]digoxin, [ 3 H]vinblastine, [ 3 H]para-aminohippuric acid, [ 3 H]oleic acid, [ 14 C]nicotine, or [ 3 H]methotrexate. [ 3 H]Cholesterol efflux was increased by extracellularly applied taurocholate. These results suggest that mABCA8b/ABCA8 functions as a sinusoidal efflux transporter for at least cholesterol and taurocholate in mouse and human liver.
AB - The ATP-binding cassette (ABC) transporter A subfamily 8 (ABCA8) belongs to the ABCA6-like transporters subgroup, which is distinct from the ABCA1-like subgroup in the ABCA family. The expression and function of the short-size human ABCA8 lacking one of the two ATP-binding domains for ATP hydrolysis, which are regularly present in the other ABCA transporters, have been reported. However, the functional differences between the short-size human ABCA8 and full-size human ABCA8, which has the two ATP-binding domains, remain unknown. The purpose of the present study was to clarify the tissue expression profiles of ABCA6-like and ABCA1-like subgroup transporters and the functional characteristics of ABCA8 in mouse and human. The tissue distribution of mouse ABCA (mABCA) transporter protein and the changes in mABCA8 protein expression levels in a mouse model of obstructive cholestasis were elucidated by means of quantitative targeted absolute proteomics (QTAP). The transport characteristics were clarified in a HEK293 cell line overexpressing full-size ABCA8 protein. QTAP and immunohistochemical analyses revealed that mABCA transporters exhibited the distinct protein expression patterns in the tissues, and mABCA8b, its mouse orthologue, was abundant in the liver and predominantly distributed in sinusoidal membranes of the hepatocytes. Further, protein expression of mABCA8b was decreased in the mouse cholestasis liver. Changes of mABCA8b expression level in cholestasis were similar to those of mABCA1, a sinusoidal cholesterol efflux transporter. Uptake and efflux assays showed that ABCA8 mediates efflux of [ 3 H]cholesterol and [ 3 H]taurocholate, while it showed no significant efflux activity for [ 3 H]estrone sulfate, [ 3 H]digoxin, [ 3 H]vinblastine, [ 3 H]para-aminohippuric acid, [ 3 H]oleic acid, [ 14 C]nicotine, or [ 3 H]methotrexate. [ 3 H]Cholesterol efflux was increased by extracellularly applied taurocholate. These results suggest that mABCA8b/ABCA8 functions as a sinusoidal efflux transporter for at least cholesterol and taurocholate in mouse and human liver.
KW - ABCA1-like subgroup transporters
KW - ABCA6-like subgroup transporters
KW - ABCA8
KW - absolute protein expression level
KW - bile duct ligation
KW - cholestasis
KW - liver
KW - mass spectrometry
KW - quantitative targeted absolute proteomics
KW - sinusoidal membrane
KW - tissue distribution
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U2 - 10.1021/acs.molpharmaceut.7b00679
DO - 10.1021/acs.molpharmaceut.7b00679
M3 - Article
C2 - 29300488
AN - SCOPUS:85041858337
SN - 1543-8384
VL - 15
SP - 343
EP - 355
JO - Molecular Pharmaceutics
JF - Molecular Pharmaceutics
IS - 2
ER -