Santic Marina, Molmeret Maelle, Barker Jeffrey R, Klose Karl E, Dekanic Andrea, Doric Miljenko, Abu Kwaik Yousef
Department of Microbiology and Immunology, University of Louisville, College of Medicine, Louisville, KY 40202, USA.
Cell Microbiol. 2007 Oct;9(10):2391-403. doi: 10.1111/j.1462-5822.2007.00968.x. Epub 2007 May 21.
Francisella tularensis is an intracellular bacterial pathogen, and is a category A bioterrorism agent. Within quiescent human macrophages, the F. tularensis pathogenicity island (FPI) is essential for bacterial growth within quiescent macrophages. The F. tularensis-containing phagosome matures to a late endosome-like stage that does not fuse to lysosomes for 1-8 h, followed by gradual bacterial escape into the macrophage cytosol. Here we show that the FPI protein IglD is essential for intracellular replication in primary human monocyte-derived macrophages (hMDMs). While the parental strain replicates robustly in pulmonary, hepatic and splenic tissues of BALB/c mice associated with severe immunopathologies, the isogenic iglD mutant is severely defective. Within hMDMs, the iglD mutant-containing phagosomes mature to either a late endosome-like phagosome, similar to the parental strain, or to a phagolysosome, similar to phagosomes harbouring the iglC mutant control. Despite heterogeneity and alterations in phagosome biogenesis, the iglD mutant bacteria escape into the cytosol faster than the parental strain within hMDMs and pulmonary cells of BALB/c mice. Co-infections of hMDMs with the wild-type strain and the iglD mutant, or super-infection of iglD mutant-infected hMDMs with the wild-type strain show that the mutant strain replicates robustly within the cytosol of hMDMs coinhabited by the wild strain. However, when the wild-type strain-infected hMDMs are super-infected by the iglD mutant, the mutant fails to replicate in the cytosol of communal macrophages. This is the first demonstration of a F. tularensis novel protein essential for proliferation in the macrophage cytosol. Our data indicate that F. tularensis transduces signals to the macrophage cytosol to remodel it into a proliferative niche, and IglD is essential for transduction of these signals.
土拉弗朗西斯菌是一种细胞内细菌病原体，属于A类生物恐怖主义制剂。在静止的人类巨噬细胞内，土拉弗朗西斯菌致病岛（FPI）对于细菌在静止巨噬细胞内的生长至关重要。含有土拉弗朗西斯菌的吞噬体成熟至晚期内体样阶段，在1 - 8小时内不与溶酶体融合，随后细菌逐渐逃逸到巨噬细胞胞质溶胶中。在此，我们表明FPI蛋白IglD对于原代人单核细胞衍生巨噬细胞（hMDM）中的细胞内复制至关重要。虽然亲本菌株在BALB / c小鼠的肺、肝和脾组织中大量复制并伴有严重免疫病理，但同基因的iglD突变体存在严重缺陷。在hMDM内，含有iglD突变体的吞噬体成熟为类似于亲本菌株的晚期内体样吞噬体，或成熟为类似于含有iglC突变体对照的吞噬体的吞噬溶酶体。尽管吞噬体生物发生存在异质性和改变，但iglD突变体细菌在hMDM和BALB / c小鼠肺细胞内比亲本菌株更快地逃逸到胞质溶胶中。hMDM与野生型菌株和iglD突变体的共感染，或iglD突变体感染的hMDM与野生型菌株的超感染表明，突变菌株在与野生菌株共居的hMDM胞质溶胶中大量复制。然而，当野生型菌株感染的hMDM被iglD突变体超感染时，突变体无法在共同巨噬细胞的胞质溶胶中复制。这是首次证明土拉弗朗西斯菌有一种对在巨噬细胞胞质溶胶中增殖至关重要的新型蛋白质。我们的数据表明，土拉弗朗西斯菌向巨噬细胞胞质溶胶转导信号以将其重塑为增殖小生境，而IglD对于这些信号的转导至关重要。
