Byrne Jane A, Strautnieks Sandra S, Mieli-Vergani Giorgina, Higgins Christopher F, Linton Kenneth J, Thompson Richard J
Institute of Liver Studies, King's College Hospital, Guy's, King's, and St. Thomas' School of Medicine, London, England.
Gastroenterology. 2002 Nov;123(5):1649-58. doi: 10.1053/gast.2002.36591.
BACKGROUND & AIMS: The bile salt export pump (BSEP) is the major bile salt transporter in the liver canalicular membrane. Our aim was to determine the affinity of the human BSEP for bile salts and identify inhibitors.
Human BSEP was expressed in insect cells. Adenosine triphosphatase (ATPase) assays were performed, and bile salt transport studies were undertaken.
The BSEP gene, ABCB11, was cloned and a recombinant baculovirus was generated. Infected insect cells expressed a 140-kilodalton protein that was absent in uninfected and in mock-infected cells. An ATPase assay showed BSEP to have a high basal ATPase activity. Transport assays were used to determine the Michaelis constant for taurocholate as 4.25 micromol/L, with a maximum velocity of 200 pmol x min(-1) x mg(-1) protein. Inhibition constant values for other bile salts were 11 micromol/L for glycocholate, 7 micromol/L for glycochenodeoxycholate, and 28 micromol/L for taurochenodeoxycholate. Cyclosporin A, rifampicin, and glibenclamide were proved to be competitive inhibitors of BSEP taurocholate transport, with inhibition constant values of 9.5 micromol/L, 31 micromol/L, and 27.5 micromol/L, respectively. Progesterone and tamoxifen did not inhibit BSEP.
The human BSEP is a high-affinity bile salt transporter. The relative affinities for the major bile salts differ from those seen in rodents and reflect the different bile salt pools. BSEP is competitively inhibited by therapeutic drugs. This is a potentially significant mechanism for drug-induced cholestasis.
胆盐输出泵（BSEP）是肝小管膜中的主要胆盐转运体。我们的目的是确定人BSEP对胆盐的亲和力并鉴定其抑制剂。
人BSEP在昆虫细胞中表达。进行了三磷酸腺苷酶（ATPase）测定，并开展了胆盐转运研究。
克隆了BSEP基因ABCB11，并构建了重组杆状病毒。受感染的昆虫细胞表达了一种140千道尔顿的蛋白质，未感染和假感染的细胞中不存在这种蛋白质。ATPase测定显示BSEP具有较高的基础ATPase活性。转运测定用于确定牛磺胆酸盐的米氏常数为4.25微摩尔/升，最大速度为200皮摩尔×分钟-1×毫克-1蛋白质。其他胆盐的抑制常数分别为：甘氨胆酸盐11微摩尔/升、甘氨鹅去氧胆酸盐7微摩尔/升、牛磺鹅去氧胆酸盐28微摩尔/升。已证明环孢素A、利福平、格列本脲是BSEP牛磺胆酸盐转运的竞争性抑制剂，抑制常数分别为9.5微摩尔/升、31微摩尔/升和27.5微摩尔/升。孕酮和他莫昔芬不抑制BSEP。
人BSEP是一种高亲和力胆盐转运体。对主要胆盐的相对亲和力与啮齿动物不同，反映了不同的胆盐池。BSEP受到治疗药物的竞争性抑制。这是药物性胆汁淤积的一个潜在重要机制。
