Rondanino Christine, Rojas Raul, Ruiz Wily G, Wang Exing, Hughey Rebecca P, Dunn Kenneth W, Apodaca Gerard
Laboratory of Epithelial Biology, Renal-Electrolyte Division of the Department of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA.
Traffic. 2007 Jul;8(7):932-49. doi: 10.1111/j.1600-0854.2007.00575.x. Epub 2007 Jun 4.
The Rho family of GTPases is implicated in the control of endocytic and biosynthetic traffic of many cell types; however, the cellular distribution of RhoB remains controversial and its function is not well understood. Using confocal microscopy, we found that endogenous RhoB and green fluorescent protein-tagged wild-type RhoB were localized to early endosomes, and to a much lesser extent to recycling endosomes, late endosomes or Golgi complex of fixed or live polarized Madin-Darby canine kidney cells. Consistent with RhoB localization to early endosomes, we observed that expression of dominant-negative RhoBN19 or dominant-active RhoBV14 altered postendocytic traffic of ligand-receptor complexes that undergo recycling, degradation or transcytosis. In vitro assays established that RhoB modulated the basolateral-to-apical transcytotic pathway by regulating cargo exit from basolateral early endosomes. Our results indicate that RhoB is localized, in part, to early endosomes where it regulates receptor egress through the early endocytic system.
GTP酶的Rho家族参与了许多细胞类型的内吞和生物合成运输的调控；然而，RhoB在细胞内的分布仍存在争议，其功能也尚未完全明确。利用共聚焦显微镜，我们发现内源性RhoB和绿色荧光蛋白标记的野生型RhoB定位于早期内体，在固定或活的极化的Madin-Darby犬肾细胞的再循环内体、晚期内体或高尔基体中定位程度要低得多。与RhoB定位于早期内体一致，我们观察到显性负性RhoBN19或显性活性RhoBV14的表达改变了经历再循环、降解或转胞吞作用的配体-受体复合物的内吞后运输。体外实验证实，RhoB通过调节货物从基底外侧早期内体的输出，调控从基底外侧到顶端的转胞吞途径。我们的结果表明，RhoB部分定位于早期内体，在那里它通过早期内吞系统调节受体的输出。
