Rab11a and myosin Vb are required for bile canalicular formation in WIF-B9 cells
Rab11a and myosin Vb are required for bile canalicular formation in WIF-B9 cells
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DOI：
10.1073/pnas.0503702102
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发表时间：
2005-10-18
影响因子：
11.1
通讯作者：
Arias, IM
中科院分区：
文献类型：
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作者：
Wakabayashi, Y;Dutt, P;Arias, IM
肝细胞通过形成功能上不同的窦状（基底外侧）和小管（顶端）质膜结构域来分化。两种不同的途径用于将膜蛋白递送至小管。具有糖基磷脂酰肌醇锚或单跨膜结构域的蛋白质靶向窦状质膜，从那里它们转胞质至小管结构域。相反，顶端ATP-结合盒（ABC）转运蛋白，这是所需的胆汁酸（ABCB 11），磷脂（ABCB 4），和非胆汁酸有机阴离子（ABCC 2）的能量依赖性胆汁分泌，缺乏在基底外侧质膜和交通直接从高尔基体膜到小管膜的初始居留。在研究WIF-B 9细胞（一种极化的肝上皮细胞系）中的顶端靶向机制时，我们观察到rab 11 a是小管形成所需的。rab 11 a的敲除或rab 11 a-GDP锁定形式的过表达阻止了小管形成，正如肌球蛋白Vb无马达尾结构域的过表达一样。在WIF-B 9细胞，缺乏胆小管，顶端ABC转运共定位与转胞膜蛋白在rab 11 a的内涵体，不像转胞标记，没有分布到质膜。我们提出肝细胞的极化（即，小管生物发生）需要将rab 11 a和肌球蛋白Vb募集到含有顶端ABC转运蛋白和转胞吞标记物的细胞内膜，从而允许它们靶向质膜。在该模型中，极化在将含有rab 11 a-肌球蛋白Vb的膜递送至表面后开始，这导致递送部位的质膜分化成顶端域（胆小管）。
Hepatocytes polarize by forming functionally distinct sinusoidal (basolateral) and canalicular (apical) plasma membrane domains. Two distinct routes are used for delivery of membrane proteins to the canaliculus. Proteins having glycosylphosphatidylinositol anchors or single transmembrane domains are targeted to the sinusoical plasma membrane from where they transcytose to the canalicular domain. In contrast, apical ATP-bincling-cassette (ABC) transporters, which are required for energy-dependent biliary secretion of bile acids (ABCB11), phospholipids (ABCB4), and non-bile acid organic anions (ABCC2), lack initial residence in the basolateral plasma membrane and traffic directly from Golgi membranes to the canalicular membrane. While investigating mechanisms of apical targeting in WIF-B9 cells, a polarized hepatic epithelial cell line, we observed that rab11a is required for canalicular formation. Knockdown of rab11a or overexpression of the rab11a-GDP locked form prevented canalicular formation as did overexpression of the myosin Vb motorless tail domain. In WIF-B9 cells, which lack bile canaliculi, apical ABC transporters colocalized with transcytotic membrane proteins in rab11a-containing endosomes and, unlike the transcytotic markers, did not distribute to the plasma membrane. We propose that polarization of hepatocytes (i.e., canalicular biogenesis) requires recruitment of rab11a and myosin Vb to intracellular membranes that contain apical ABC transporters and transcytotic markers, permitting their targeting to the plasma membrane. In this model, polarization is initiated upon delivery of rab11a-myosin Vb-containing membranes to the surface, which causes plasma membrane at the site of delivery to differentiate into apical domain (bile canaliculus).