Depolymerization of cortical actin inhibits UT-A1 urea transporter endocytosis but promotes forskolin-stimulated membrane trafficking.
Depolymerization of cortical actin inhibits UT-A1 urea transporter endocytosis but promotes forskolin-stimulated membrane trafficking.
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皮质肌动蛋白的解聚会抑制 UT-A1 尿素转运蛋白的内吞作用，但会促进毛喉素刺激的膜运输。
DOI：
10.1152/ajpcell.00440.2011
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
Chen,Guangping
中科院分区：
文献类型：
--
作者：
Xu,Gang;Su,Hua;Carter,ConnerB;Fröhlich,Otto;Chen,Guangping
细胞骨架参与转运蛋白调控的许多方面。在这项研究中，通过酵母双杂交筛选，我们确定了细胞骨架蛋白actin作为UT-A1尿素转运蛋白的结合伙伴。这表明肌动蛋白在调节UT-A1活性中起作用。肌动蛋白特异性地与UT-A1的羧基末端结合。一项系列突变研究表明，当918丝氨酸突变为丙氨酸时，UT-A1羧基末端的肌动蛋白结合被取消。在极化的UT-A1- mdck细胞中，皮质丝状(F)肌动蛋白与UT-A1共定位于顶膜和顶下细胞质。在细胞表面，肌动蛋白和UT-A1都分布在脂筏微域。通过生物素化测定，latrunculin B对f -肌动蛋白细胞骨架的破坏导致细胞膜上UT-A1的积累。这种作用主要是由于UT-A1在网格蛋白和小窝蛋白介导的内吞途径中均受到抑制。相反，肌动蛋白解聚促进了福斯克林刺激的UT-A1转运到细胞表面。功能上，latrunculin B解聚肌动蛋白可显著增加卵母细胞表达系统中UT-A1尿素转运活性。我们的研究表明，皮质F-actin不仅作为一种结构蛋白，而且直接与UT-A1相互作用，通过影响内吞作用和运输作用，在控制UT-A1细胞表面表达中发挥重要作用，从而调节UT-A1的生物活性。
The cytoskeleton participates in many aspects of transporter protein regulation. In this study, by using yeast two-hybrid screening, we identified the cytoskeletal protein actin as a binding partner with the UT-A1 urea transporter. This suggests that actin plays a role in regulating UT-A1 activity. Actin specifically binds to the carboxyl terminus of UT-A1. A serial mutation study shows that actin binding to UT-A1's carboxyl terminus was abolished when serine 918 was mutated to alanine. In polarized UT-A1-MDCK cells, cortical filamentous (F) actin colocalizes with UT-A1 at the apical membrane and the subapical cytoplasm. In the cell surface, both actin and UT-A1 are distributed in the lipid raft microdomains. Disruption of the F-actin cytoskeleton by latrunculin B resulted in UT-A1 accumulation in the cell membrane as measured by biotinylation. This effect was mainly due to inhibition of UT-A1 endocytosis in both clathrin and caveolin-mediated endocytic pathways. In contrast, actin depolymerization facilitated forskolin-stimulated UT-A1 trafficking to the cell surface. Functionally, depolymerization of actin by latrunculin B significantly increased UT-A1 urea transport activity in an oocyte expression system. Our study shows that cortical F-actin not only serves as a structural protein, but directly interacts with UT-A1 and plays an important role in controlling UT-A1 cell surface expression by affecting both endocytosis and trafficking, therefore regulating UT-A1 bioactivity.