Mrozowska Paulina S, Fukuda Mitsunori
a Laboratory of Membrane Trafficking Mechanisms, Department of Developmental Biology and Neurosciences , Graduate School of Life Sciences, Tohoku University , Sendai, Miyagi , Japan.
Small GTPases. 2016 Oct;7(4):231-238. doi: 10.1080/21541248.2016.1211068. Epub 2016 Jul 27.
The characteristic feature of polarity establishment in MDCK II cells is transcytosis of apical glycoprotein podocalyxin (PCX) from the outer plasma membrane to the newly formed apical domain. This transcytotic event consists of multiple steps, including internalization from the plasma membrane, transport through early endosomes and Rab11-positive recycling endosomes, and delivery to the apical membrane. These steps are known to be tightly coordinated by Rab small GTPases, which act as molecular switches cycling between active GTP-bound and inactive GDP-bound states. However, our knowledge regarding which sets of Rabs regulate particular steps of PCX trafficking was rather limited. Recently, we have performed a comprehensive analysis of Rab GTPase engagement in the transcytotic pathway of PCX during polarity establishment in 2-dimensional (2D) and 3-dimensional (3D) MDCK II cell cultures. In this Commentary we summarize our findings and set them in the context of previous reports.
MDCK II细胞中极性建立的特征是顶端糖蛋白足突融合蛋白（PCX）从外质膜经转胞吞作用转运至新形成的顶端结构域。这一转胞吞事件包含多个步骤，包括从质膜内化、通过早期内体和Rab11阳性回收内体运输，以及递送至顶端膜。已知这些步骤由Rab小GTP酶紧密协调，Rab小GTP酶作为分子开关在活性GTP结合状态和非活性GDP结合状态之间循环。然而，我们对于哪些Rab蛋白集调节PCX转运的特定步骤的了解相当有限。最近，我们对二维（2D）和三维（3D）MDCK II细胞培养物极性建立过程中Rab GTP酶参与PCX转胞吞途径进行了全面分析。在本述评中，我们总结了我们的发现，并将其置于先前报告的背景下。
