RAB5A IS A COMMON COMPONENT OF THE APICAL AND BASOLATERAL ENDOCYTIC MACHINERY IN POLARIZED EPITHELIAL-CELLS
RAB5A IS A COMMON COMPONENT OF THE APICAL AND BASOLATERAL ENDOCYTIC MACHINERY IN POLARIZED EPITHELIAL-CELLS
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DOI：
10.1073/pnas.91.11.5061
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发表时间：
1994-05-24
影响因子：
11.1
通讯作者：
ZERIAL, M
中科院分区：
文献类型：
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作者：
BUCCI, C;WANDINGERNESS, A;ZERIAL, M
在非极化细胞中，小的GTdR Rab 5a定位于质膜、网格蛋白包被的囊泡和早期内体。Rab 5a是体外早期内体融合所需的，并在体内调节质膜和早期内体之间的转运。在极化上皮细胞中，胞吞作用发生在分开的顶侧和基底侧质膜区域。内化的分子最初被递送到不同的顶端或基底外侧早期内体。在体外，顶端早期内体可以容易地彼此融合，但不能与基底外侧内体融合，反之亦然，从而表明顶端和基底外侧早期内吞途径由不同的机制控制。在这里，我们研究了Rab 5a在极化上皮细胞中的定位和功能。共聚焦免疫荧光显微镜对小鼠肾脏切片显示协会的蛋白质与顶端和基底侧质膜域和底层结构。在极化的Madin-Darby犬肾I细胞中，内源性和过表达的Rab 5a具有相同的分布。此外，蛋白质的过度表达导致从细胞的两个结构域的液相摄取增加2倍，从而表明Rab 5a在顶端和基底侧内吞作用中起作用。我们的数据表明，上皮细胞的顶端和基底侧内吞机制共享共同的监管组件和Rab 5a本身是不足以针对内吞囊泡顶端或基底侧早期内体。
In nonpolarized cells, the small GTPase Rab5a is localized to the plasma membrane, clathrin-coated vesicles, and early endosomes. Rab5a is required for early endosome fusion in vitro and regulates transport between the plasma membrane and early endosomes, in vivo. In polarized epithelial cells endocytosis occurs from separate apical and basolateral plasma membrane domains. Internalized molecules are initially delivered to distinct apical or basolateral early endosomes. In vitro, apical early endosomes can readily fuse with one another but not with the basolateral endosomes and vice versa, thereby indicating that the apical and basolateral early endocytic pathways are controlled by distinct machineries. Here, we have investigated the localization and function of Rab5a in polarized epithelial cells. Confocal immunofluorescence microscopy on mouse kidney sections revealed association of the protein with the apical and basolateral plasma membrane domains and underlying structures. In polarized Madin-Darby canine kidney I cells, endogenous and overexpressed Rab5a have the same distribution. Moreover, overexpression of the protein causes a 2-fold increase in fluid-phase uptake from both domains of the cell, thus showing that Rab5a functions in apical and basolateral endocytosis. Our data indicate that the apical and basolateral endocytic machineries of epithelial cells share common regulatory components and that Rab5a per se is not sufficient to target endocytic vesicles to apical or basolateral early endosomes.