Regulation of podocalyxin trafficking by Rab small GTPases in epithelial cells

摘要

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, includinginternalization from the plasma membrane, transport through early endosomes and Rabn-positive recycling endosomes, and delivery to the apicaf membrane. These steps are known to be tightly coordinated by Rab small GTPases, which act as molecular switchescycling 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-drmensional (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.