Truchan Hilary K, Cockburn Chelsea L, Hebert Kathryn S, Magunda Forgivemore, Noh Susan M, Carlyon Jason A
Department of Microbiology and Immunology, Virginia Commonwealth University School of Medicine Richmond, VA, USA.
Program in Vector Borne Diseases, Department of Veterinary Microbiology and Pathology, Washington State UniversityPullman, WA, USA; The Paul G. Allen School for Global Animal Health, Washington State UniversityPullman, WA, USA.
Front Cell Infect Microbiol. 2016 Mar 1;6:22. doi: 10.3389/fcimb.2016.00022. eCollection 2016.
The genus Anaplasma consists of tick-transmitted obligate intracellular bacteria that invade white or red blood cells to cause debilitating and potentially fatal infections. A. phagocytophilum, a human and veterinary pathogen, infects neutrophils to cause granulocytic anaplasmosis. A. marginale invades bovine erythrocytes. Evidence suggests that both species may also infect endothelial cells in vivo. In mammalian and arthropod host cells, A. phagocytophilum and A. marginale reside in host cell derived pathogen-occupied vacuoles (POVs). While it was recently demonstrated that the A. phagocytophilum-occupied vacuole (ApV) intercepts membrane traffic from the trans-Golgi network, it is unclear if it or the A. marginale-occupied vacuole (AmV) interacts with other secretory organelles. Here, we demonstrate that the ApV and AmV extensively interact with the host endoplasmic reticulum (ER) in endothelial, myeloid, and/or tick cells. ER lumen markers, calreticulin, and protein disulfide isomerase, and the ER membrane marker, derlin-1, were pronouncedly recruited to the peripheries of both POVs. ApV association with the ER initiated early and continued throughout the infection cycle. Both the ApV and AmV interacted with the rough ER and smooth ER. However, only derlin-1-positive rough ER derived vesicles were delivered into the ApV lumen where they localized with intravacuolar bacteria. Transmission electron microscopy identified multiple ER-POV membrane contact sites on the cytosolic faces of both species' vacuoles that corresponded to areas on the vacuoles' lumenal faces where intravacuolar Anaplasma organisms closely associated. A. phagocytophilum is known to hijack Rab10, a GTPase that regulates ER dynamics and morphology. Yet, ApV-ER interactions were unhindered in cells in which Rab10 had been knocked down, demonstrating that the GTPase is dispensable for the bacterium to parasitize the ER. These data establish the ApV and AmV as pathogen-host interfaces that directly engage the ER in vertebrate and invertebrate host cells and evidence the conservation of ER parasitism between two Anaplasma species.
无形体属包含蜱传播的专性细胞内细菌，这些细菌侵入白细胞或红细胞，引发使人虚弱甚至可能致命的感染。嗜吞噬细胞无形体是一种人畜共患病原体，它感染中性粒细胞，引发粒细胞无形体病。边缘无形体侵入牛的红细胞。有证据表明，这两种细菌在体内也可能感染内皮细胞。在哺乳动物和节肢动物宿主细胞中，嗜吞噬细胞无形体和边缘无形体存在于宿主细胞衍生的病原体占据的液泡（POV）中。虽然最近有研究表明，嗜吞噬细胞无形体占据的液泡（ApV）会拦截来自反式高尔基体网络的膜运输，但目前尚不清楚它或边缘无形体占据的液泡（AmV）是否与其他分泌细胞器相互作用。在这里，我们证明ApV和AmV在内皮细胞、髓样细胞和/或蜱细胞中与宿主内质网（ER）广泛相互作用。内质网腔标记物、钙网蛋白和蛋白质二硫键异构酶，以及内质网膜标记物derlin-1，都明显被募集到两个POV的周边。ApV与内质网的结合在早期就开始，并在整个感染周期持续。ApV和AmV都与粗面内质网和滑面内质网相互作用。然而，只有derlin-1阳性的粗面内质网衍生的囊泡被递送到ApV腔内，并与泡内细菌定位在一起。透射电子显微镜在两种细菌液泡的胞质面上鉴定出多个内质网-POV膜接触位点，这些位点对应于液泡腔面上无形体生物体紧密相连的区域。已知嗜吞噬细胞无形体会劫持Rab10，一种调节内质网动态和形态的GTP酶。然而，在Rab10被敲除的细胞中，ApV-内质网的相互作用并未受到阻碍，这表明该GTP酶对于细菌寄生内质网来说是可有可无的。这些数据表明ApV和AmV是病原体-宿主界面，它们在脊椎动物和无脊椎动物宿主细胞中直接与内质网相互作用，并证明了两种无形体物种之间内质网寄生现象的保守性。
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