The Early Phagosomal Stage of Francisella tularensis Determines Optimal Phagosomal Escape and Francisella Pathogenicity Island Protein Expression
The Early Phagosomal Stage of Francisella tularensis Determines Optimal Phagosomal Escape and Francisella Pathogenicity Island Protein Expression
复制标题
DOI：
10.1128/iai.00682-08
复制
发表时间：
2008-12-01
影响因子：
3.1
通讯作者：
Celli, Jean
中科院分区：
文献类型：
--
作者：
Chong, Audrey;Wehrly, Tara D.;Celli, Jean
土拉弗朗西斯菌是一种细胞内病原体，可以在巨噬细胞内存活和复制。在吞噬作用和与内吞途径的短暂相互作用后，F。土拉热菌迅速从其原始吞噬体逃逸到巨噬细胞细胞质中，并最终在其中复制。为了研究新生吞噬体对弗朗西斯菌胞内循环的重要性，我们描述了弗朗西斯菌早期的运输事件。土拉热亚种土拉热菌菌株Schu S4在鼠骨髓衍生的巨噬细胞模型中的表达。在这里，我们表明，早期的吞噬体含有Schu S4瞬时与早期和晚期内体相互作用，并在吞噬体破坏发生前酸化。在感染前用空泡ATP酶抑制剂巴弗洛霉素A1或康卡那霉素A抑制内体酸化显著延迟但不阻断吞噬体逃逸和胞质复制，表明早期含弗朗西斯菌的吞噬体（FCP）的成熟对于最佳吞噬体逃逸和随后的细胞内生长是重要的。此外，弗朗西斯菌致病岛（FPI）蛋白表达诱导早期细胞内运输事件。尽管内体酸化的抑制模拟了由FPI编码的IgICD蛋白的突变引起的早期吞噬体逃逸缺陷，但它不抑制FPI蛋白的细胞内诱导，表明这种反应不依赖于吞噬体pH。这些结果表明，吞噬体的早期成熟是最佳的吞噬体逃逸所必需的，而早期的FCP提供了除液泡内pH以外的线索，FPI蛋白的细胞内诱导。
Francisella tularensis is an intracellular pathogen that can survive and replicate within macrophages. Following phagocytosis and transient interactions with the endocytic pathway, F. tularensis rapidly escapes from its original phagosome into the macrophage cytoplasm, where it eventually replicates. To examine the importance of the nascent phagosome for the Francisella intracellular cycle, we have characterized early trafficking events of the F. tularensis subsp. tularensis strain Schu S4 in a murine bone marrow-derived macrophage model. Here we show that early phagosomes containing Schu S4 transiently interact with early and late endosomes and become acidified before the onset of phagosomal disruption. Inhibition of endosomal acidification with the vacuolar ATPase inhibitor bafilomycin A1 or concanamycin A prior to infection significantly delayed but did not block phagosomal escape and cytosolic replication, indicating that maturation of the early Francisella-containing phagosome (FCP) is important for optimal phagosomal escape and subsequent intracellular growth. Further, Francisella pathogenicity island (FPI) protein expression was induced during early intracellular trafficking events. Although inhibition of endosomal acidification mimicked the early phagosomal escape defects caused by mutation of the FPI-encoded IgICD proteins, it did not inhibit the intracellular induction of FPI proteins, demonstrating that this response is independent of phagosomal pH. Altogether, these results demonstrate that early phagosomal maturation is required for optimal phagosomal escape and that the early FCP provides cues other than intravacuolar pH that determine intracellular induction of FPI proteins.