Bile salt-dependent efflux of cellular phospholipids mediated by ATP binding cassette protein B4
Bile salt-dependent efflux of cellular phospholipids mediated by ATP binding cassette protein B4
复制标题
DOI：
10.1002/hep.21591
复制
发表时间：
2007-07-01
期刊：
影响因子：
13.5
通讯作者：
Ueda, Kazumitsu
中科院分区：
文献类型：
--
作者：
Morita, Shin-ya;Kobayashi, Aya;Ueda, Kazumitsu
人ABCB4（多药耐药[MDR] 3p -糖蛋白）在肝细胞小管膜表达。ABCB4已被证明是磷脂酰胆碱（PC）分泌到胆汁中以及PC在质膜上转运所必需的。为了进一步研究ABCB4的功能，我们建立了稳定表达ABCB4（人胚胎肾[HEK]/ABCB4）的细胞系。添加牛磺胆酸后，HEK/ABCB4细胞的磷脂外排明显增加。此外，HEK/ABCB4细胞的胆固醇外排也在牛磺胆酸存在下增强。光散射测量表明，牛磺胆酸盐单体在abcb4介导的脂质分泌中起重要作用。另一方面，即使存在牛磺酸胆酸，磷脂和胆固醇的外排也不是由ABCB1 （MDR1）介导的。牛磺胆酸盐比糖胆酸盐和胆酸盐更有效地促进HEK/ABCB4细胞的磷脂和胆固醇外排。ABCB4-K435M和ABCB4-K1075M是Walker A赖氨酸突变体，在牛磺胆酸存在的情况下不介导磷脂和胆固醇的外排，这表明ATP水解对外排至关重要。维拉帕米完全抑制HEK/ABCB4细胞中依赖于牛磺胆酸的磷脂和胆固醇的外排。质谱分析显示，与鞘磷脂相比，在牛磺酸胆酸存在时，HEK/ABCB4细胞优先分泌PC。PC囊泡诱导胆固醇从细胞膜扩散，但不接受来自ABCB4的胆固醇。结论：在胆盐存在的情况下，ABCB4介导磷脂外排进入小管腔，在胆汁形成和脂质稳态中起重要作用。
Human ABCB4 (multidrug resistance [MDR]3 P-glycoprotein) is expressed in the canalicular membrane of the hepatocyte. ABCB4 has been shown to be required for phosphatidylcholine (PC) secretion into the bile and to translocate PC across the plasma membrane. To further investigate the function of ABCB4, we established a cell line stably expressing ABCB4 (human embryonic kidney [HEK]/ABCB4). The efflux of phospholipids from HEK/ABCB4 cells was remarkably increased by the addition of taurocholate. In addition, the cholesterol efflux from HEK/ABCB4 cells was also enhanced in the presence of taurocholate. Light scattering measurements suggested that the taurocholate monomer plays an important role in ABCB4-mediated lipid secretion. On the other hand, the efflux of phospholipids and cholesterol was not mediated by ABCB1 (MDR1) even in the presence of taurocholate. Taurocholate promoted the efflux of phospholipids and cholesterol from HEK/ABCB4 cells more efficiently than glycocholate and cholate. ABCB4-K435M and ABCB4-K1075M, Walker A lysine mutants, did not mediate the phospholipid and cholesterol efflux in the presence of taurocholate, suggesting that ATP hydrolysis is essential for the efflux. Verapamil completely inhibited the taurocholate-dependent efflux of phospholipids and cholesterol from HEK/ABCB4 cells. Mass spectrometry revealed that, in the presence of taurocholate, HEK/ABCB4 cells preferentially secreted PC compared to sphingomyelin. PC vesicles induced cholesterol diffusion from cell membrane, but did not accept cholesterol from ABCB4. Conclusion: ABCB4 mediates the efflux of phospholipids into the canalicular lumen in the presence of bile salts, and plays a crucial role in bile formation and lipid homeostasis.