A novel mutation within a transmembrane helix of the bile salt export pump (BSEP, ABCB11) with delayed development of cirrhosis
A novel mutation within a transmembrane helix of the bile salt export pump (BSEP, ABCB11) with delayed development of cirrhosis
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DOI：
10.1111/liv.12217
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发表时间：
2013-11-01
影响因子：
6.7
通讯作者：
Kubitz, Ralf
中科院分区：
文献类型：
--
作者：
Stindt, Jan;Ellinger, Philipp;Kubitz, Ralf
背景与目的胆盐输出泵（BSEP，ABCB 11）是肝细胞小管膜分泌胆盐所必需的。与BSEP突变相关的临床表型通常分为良性复发性肝内胆汁淤积症（BRIC-2）或进行性家族性肝内胆汁淤积症（PFIC-2）。方法采用免疫组化、基因测序、胆盐分析、哺乳动物细胞和酵母重组表达等方法对BSEP相关性肝病的分子基础进行鉴定，并进行定位和体外活性研究。结果一对兄妹均为间歇性胆汁淤积，考虑良性复发性肝内胆汁淤积。ABCB 11的基因测序鉴定了新的错义突变p.G374S，其定位于BSEP的推定的第六跨膜螺旋。兄弟在18岁时出现肝纤维化，3年内进展为肝硬化。肝组织的免疫荧光显示清晰的小管BSEP表达;然而，胆汁盐浓度急剧降低。在符合这些在体内的研究结果，HEK 293细胞表现出定期膜靶向的人BSEPG 374 S，而在体外运输测量显示了强烈降低的运输activity.Conclusions新的突变p.G374S损害运输功能，而不禁用膜定位的BSEP。虽然跨膜螺旋内的所有其他已知BSEP突变与PFIC-2相关，但新的p.G374S突变导致BRIC-2和PFIC-2之间的过渡表型。
Background & Aims The bile salt export pump (BSEP, ABCB11) is essential for bile salt secretion at the canalicular membrane of liver cells. Clinical phenotypes associated with BSEP mutations are commonly categorized as benign recurrent intrahepatic cholestasis (BRIC-2) or progressive familial intrahepatic cholestasis (PFIC-2). Methods The molecular basis of BSEP-associated liver disease in a sibling pair was characterized by immunostaining, gene sequencing, bile salt analysis and recombinant expression in mammalian cells and yeast for localization and in vitro activity studies respectively. Results Benign recurrent intrahepatic cholestasis was considered in a brother and sister who both suffered from intermittent cholestasis since childhood. Gene sequencing of ABCB11 identified the novel missense mutation p.G374S, which is localized in the putative sixth transmembrane helix of BSEP. Liver fibrosis was present in the brother at the age of 18 with progression to cirrhosis within 3years. Immunofluorescence of liver tissue showed clear canalicular BSEP expression; however, biliary concentration of bile salts was drastically reduced. In line with these in vivo findings, HEK293 cells showed regular membrane targeting of human BSEPG374S, whereas in vitro transport measurements revealed a strongly reduced transport activity.Conclusions The novel mutation p.G374S impairs transport function without disabling membrane localization of BSEP. While all other known BSEP mutations within transmembrane helices are associated with PFIC-2, the new p.G374S mutation causes a transitional phenotype between BRIC-2 and PFIC-2.