4-phenylbutyrate enhances the cell surface expression and the transport capacity of wild-type and mutated bile salt export pumps
4-phenylbutyrate enhances the cell surface expression and the transport capacity of wild-type and mutated bile salt export pumps
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DOI：
10.1002/hep.21630
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发表时间：
2007-06-01
期刊：
影响因子：
13.5
通讯作者：
Sugiyama, Yuichi
中科院分区：
文献类型：
--
作者：
Hayashi, Hisamitsu;Sugiyama, Yuichi
进行性家族性肝内胆汁淤积症2型(PFIC2)是由胆盐输出泵(BSEP/ABCB11)基因突变引起的。我们以前报道过，在欧洲患者中经常发现的E297G和D482G BSEP突变导致膜转运受损，而这两个突变都保留了它们的转运功能。这种功能异常的定位可能是由于BSEP滞留在内质网(ER)，随后蛋白酶体降解。由于4-苯丁酸钠(4PBA)已被证明可恢复细胞表面突变质膜蛋白的表达，在本研究中，我们研究了4PBA处理对E297G和D482G BSEP的影响。利用Madin-Darby犬肾(MDCK)Il细胞进行的跨细胞转运和细胞表面生物素化研究表明，4PBA处理增加了功能细胞表面野生型(NW)、E297G和D482G BSEP的表达。4PBA处理的细胞表面驻留的BSEP的半衰期延长是造成这一结果的原因。此外，用4PBA处理SD大鼠后，BSEP在小管膜上的表达增加，并伴有胆汁中[H-3]牛磺胆酸(TC)排泄增加。结论：临床浓度的4PBA可增强MDCK II细胞表面WT、E297G和D482G BSEP的表达和转运能力，并诱导BSEP在小管膜上的功能性表达和胆汁酸通过小管膜的转运。4PBA不仅可以治疗E297G和D482G突变的PFIC2患者，还可以治疗其他胆汁淤积症患者，这些患者的小管膜上BSEP表达降低。
Progressive familial intrahepatic cholestasis type 2 (PFIC2) is caused by a mutation in the bile salt export pump (BSEP/ABCB11) gene. We previously reported that E297G and D482G BSEP, which are frequently found mutations in European patients, result in impaired membrane trafficking, whereas both mutants retain their transport function. The dysfunctional localization is probably attributable to the retention of BSEP in endoplasmic reticulum (ER) followed by proteasomal degradation. Because sodium 4-phenylbutyrate (4PBA) has been shown to restore the reduced cell surface expression of mutated plasma membrane proteins, in the current study, we investigated the effect of 4PBA treatment on E297G and D482G BSEP. Transcellular transport and cell surface biotinylation studies using Madin-Darby canine kidney (MDCK) Il cells demonstrated that 4PBA treatment increased functional cell surface expression of wild-type (NW), E297G, and D482G BSEP. The prolonged half-life of cell surface-resident BSEP with 4PBA treatment was responsible for this result. Moreover, treatment of Sprague-Dawley rats with 4PBA resulted in an increase in BSEP expression at the canalicular membrane, which was accompanied by an increase in the biliary excretion of [H-3]taurocholic acid (TC). Conclusion: 4PBA treatment with a clinically achievable concentration enhances the cell surface expression and the transport capacity of WT, E297G, and D482G BSEP in MDCK II cells, and also induces functional BSEP expression at the canalicular membrane and bile acid transport via canalicular membrane in vivo. 4PBA is a potential pharmacological agent for treating not only PFIC2 patients with E297G and D482G mutations but also other cholestatic patients, in whom the BSEP expression at the canalicular membrane is reduced.