A Framework for Lateral Membrane Trafficking and Polar Tethering of the PEN3 ATP-Binding Cassette Transporter1[CC-BY]
A Framework for Lateral Membrane Trafficking and Polar Tethering of the PEN3 ATP-Binding Cassette Transporter1[CC-BY]
复制标题
PEN3 ATP 结合盒转运蛋白 1 的横向膜运输和极性束缚框架[CC-BY]
作者：
Hailiang Mao;Moritaka Nakamura;C. Viotti;M. Grebe
外外侧膜货物的跨高尔基网络运输及其EXOCYST84b捆绑因子的极性需要ACTIN7。植物最外层的细胞层，即表皮及其外（侧）膜域面对环境不断受到生物和非生物胁迫的挑战。因此，表皮和外膜结构域提供了重要的选择性和保护性屏障。然而，只有少数特异性外膜定位的蛋白质是已知的。同样，外膜结构域蛋白的转运和极性定位的分子机制需要进一步探索。在这里，我们证明了ACTIN7 （ACT7）介导渗透3 （PEN3）外膜蛋白从反式高尔基网络（TGN）运输到拟南芥根表皮的质膜，并且肌动蛋白的功能有助于PEN3的内噬循环。与这种来自TGN的通用act7依赖性转运相反，EXOCYST84b （EXO84b）系聚因子介导PEN3外膜极性。此外，EXO84b在外膜结构域的精确定位需要ACT7的功能。因此，我们的研究结果揭示了在外外侧膜货物运输和极性建立过程中，ACT7功能在空间和机械上的不同要求。他们进一步确定了外外侧膜货物极性的胞囊系固复杂介质。
ACTIN7 is required for trans-Golgi network trafficking of outer lateral membrane cargo and for polarity of its EXOCYST84b tethering factor. The outermost cell layer of plants, the epidermis, and its outer (lateral) membrane domain facing the environment are continuously challenged by biotic and abiotic stresses. Therefore, the epidermis and the outer membrane domain provide important selective and protective barriers. However, only a small number of specifically outer membrane-localized proteins are known. Similarly, molecular mechanisms underlying the trafficking and the polar placement of outer membrane domain proteins require further exploration. Here, we demonstrate that ACTIN7 (ACT7) mediates trafficking of the PENETRATION3 (PEN3) outer membrane protein from the trans-Golgi network (TGN) to the plasma membrane in the root epidermis of Arabidopsis (Arabidopsis thaliana) and that actin function contributes to PEN3 endocytic recycling. In contrast to such generic ACT7-dependent trafficking from the TGN, the EXOCYST84b (EXO84b) tethering factor mediates PEN3 outer-membrane polarity. Moreover, precise EXO84b placement at the outer membrane domain itself requires ACT7 function. Hence, our results uncover spatially and mechanistically distinct requirements for ACT7 function during outer lateral membrane cargo trafficking and polarity establishment. They further identify an exocyst tethering complex mediator of outer lateral membrane cargo polarity.