Intracellular trafficking of bile salt export pump (ABCB11) in polarized hepatic cells: Constitutive cycling between the canalicular membrane and Rab11-positive endosomes
Intracellular trafficking of bile salt export pump (ABCB11) in polarized hepatic cells: Constitutive cycling between the canalicular membrane and Rab11-positive endosomes
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DOI：
10.1091/mbc.e03-10-0737
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发表时间：
2004-07-01
影响因子：
3.3
通讯作者：
Arias, IM
中科院分区：
文献类型：
--
作者：
Wakabayashi, Y;Lippincott-Schwartz, J;Arias, IM
胆盐输出泵（BSEP，ABCB 11）将ATP水解与胆汁酸转运到肝细胞的胆小管中偶联。其在顶小管膜中的定位受分泌胆汁组分的需求的生理调节。为了深入了解这种定位是如何调节的，我们研究了极化WIF-B 9细胞中标记有黄色荧光蛋白（YFP）的BSEP的细胞内运输。共聚焦成像显示，BSEP-YFP定位于小管膜和小管泡状结构中，要么邻近微管组织中心，要么广泛分布在细胞质中。在后两个位置，BSEP-YFP与内体标记物rab 11共定位。选择性光漂白实验表明，单个BSEP-YFP分子在与细胞内BSEP-YFP池交换之前仅短暂地驻留在小管膜中。这种交换被微管和肌动蛋白抑制剂抑制，不受布雷菲德菌素A，二丁酰环AMP，牛磺胆酸盐，或PI 3-激酶抑制剂。富含BSEP-YFP的细胞内载体从邻近微管组织中心的球状结构中伸长并解离为管状元件。它们向小管或基底外侧膜振荡运动，但仅与小管膜融合。BSEP组成性循环的小管和细胞内膜之间的通路可用于调节BSEP的顶端池以及其他顶端膜转运蛋白。
The bile salt export pump (BSEP, ABCB11) couples ATP hydrolysis with transport of bile acids into the bile canaliculus of hepatocytes. Its localization in the apical canalicular membrane is physiologically regulated by the demand to secrete biliary components. To gain insight into how such localization is regulated, we studied the intracellular trafficking of BSEP tagged with yellow fluorescent protein (YFP) in polarized WIF-B9 cells. Confocal imaging revealed that BSEP-YFP was localized at the canalicular membrane and in tubulo-vesicular structures either adjacent to the microtubule-organizing center or widely distributed in the cytoplasm. In the latter two locations, BSEP-YFP colocalized with rab11, an endosomal marker. Selective photobleaching experiments revealed that single BSEP-YFP molecules resided in canalicular membranes only transiently before exchanging with intracellular BSEP-YFP pools. Such exchange was inhibited by microtubule and actin inhibitors and was unaffected by brefeldin A, dibutyryl cyclic AMP, taurocholate, or PI 3-kinase inhibitors. Intracellular carriers enriched in BSEP-YFP elongated and dissociated as tubular elements from a globular structure adjacent to the microtubule-organizing center. They displayed oscillatory movement toward either canalicular or basolateral membranes, but only fused with the canalicular membrane. The pathway between canalicular and intracellular membranes that BSEP constitutively cycles within could serve to regulate apical pools of BSEP as well as other apical membrane transporters.