Biogenesis Of The Salmonella-containing Vacuole

沙门氏菌sp是兼性细胞内细菌，在液泡（SCV）内居住和复制。SCV的生物发生是由细菌决定的，并涉及通过III型分泌系统转运到宿主细胞中的效应蛋白。侵袭是由于肌动蛋白细胞骨架的局部重排引起的局部膜褶。这一过程是由几个易位效应蛋白的协同作用诱导的。膜褶含有大量的膜，必须迅速交付。由于在scv中只检测到内吞标记物，因此一直认为生物合成/分泌途径不参与这一过程。在与蒙特利尔大学的Michel Desjardins的合作中，我们最近发现SCV迅速获得内质网膜，并且确实与内质网相邻。因此，内质网有可能为质膜上的皱褶提供膜含量。事实上，在吞噬细胞中，可以看到内质网膜与含有乳胶珠或利什曼原虫的新生吞噬体相邻。

Salmonella sp are facultative intracellular bacteria that reside and replicate within a vacuole (SCV). The biogenesis of the SCV is determined by the bacteria and involves effector proteins that are translocated into the host cell via Type III secretion systems. Invasion occurs as a result of localized membrane ruffles that are due to local rearrangement of the actin cytoskeleton. This process is induced by the co-operative effectives of several translocated effector proteins. Membrane ruffles contain large amounts of membrane that must be rapidly delivered. It has been assumed, since only endocytic markers are detected in SCVs, that the biosynthetic/secretory pathway is not involved in this process. In collaboration with Michel Desjardins at the University of Montreal, we have recently shown that the SCV rapidly acquires Endoplasmic Reticulum membranes and indeed appears contiguous with the ER. Thus it is possible that the ER is contributing membrane content to ruffles at the plasma membrane. Indeed, in phagocytic cells, ER membrane can be seen to be contiguous with nascent phagosomes containing either latex beads or Leishmania. We have now developed a live cell system that we are using to characterize 3 stages of Salmonella-host cell interactions; invasion, SCV formation and Sif dynamics. Sifs are tubules that extend from, and are contiguous with, SCVs. The formation of Sifs is dependent on several Salmonella effector proteins and unidentified host factors. We have found that these extensive tubules are extremely dynamic and are dependent on microtubules. Further characterization of the role of microtubules, motors and other host cell factors is ongoing.