Prabhat Prashant, Gan Zhuo, Chao Jerry, Ram Sripad, Vaccaro Carlos, Gibbons Steven, Ober Raimund J, Ward E Sally
Department of Immunology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
Proc Natl Acad Sci U S A. 2007 Apr 3;104(14):5889-94. doi: 10.1073/pnas.0700337104. Epub 2007 Mar 23.
The intracellular events on the recycling pathway that lead from sorting endosomes to exocytosis at the plasma membrane are central to cellular function. However, despite intensive study, these processes are poorly characterized in spatial and dynamic terms. The primary reason for this is that, to date, it has not been possible to visualize rapidly moving intracellular compartments in three dimensions in cells. Here, we use a recently developed imaging setup in which multiple planes can be simultaneously imaged within the cell in conjunction with visualization of the plasma membrane plane by using total internal reflection fluorescence microscopy. This has allowed us to track and characterize intracellular events on the recycling pathway that lead to exocytosis of the MHC Class I-related receptor, FcRn. We observe both direct delivery of tubular and vesicular transport containers (TCs) from sorting endosomes to exocytic sites at the plasma membrane, and indirect pathways in which TCs that are not in proximity to sorting endosomes undergo exocytosis. TCs can also interact with different sorting endosomes before exocytosis. Our data provide insight into the intracellular events that precede exocytic fusion.
从分拣内体到质膜处胞吐作用的回收途径上的细胞内事件，对于细胞功能至关重要。然而，尽管进行了深入研究，这些过程在空间和动态方面的特征仍不清楚。主要原因是，迄今为止，还无法在细胞中对快速移动的细胞内区室进行三维可视化。在这里，我们使用了一种最近开发的成像装置，通过全内反射荧光显微镜，可以在细胞内同时对多个平面进行成像，并结合质膜平面的可视化。这使我们能够追踪和表征回收途径上导致MHC I类相关受体FcRn胞吐作用的细胞内事件。我们观察到，管状和囊泡状运输容器（TCs）从分拣内体直接运输到质膜处的胞吐位点，以及间接途径，即那些不靠近分拣内体的TCs发生胞吐作用。TCs在胞吐作用之前也可以与不同的分拣内体相互作用。我们的数据为胞吐融合之前的细胞内事件提供了见解。
