Burkholderia pseudomallei is a facultative intracellular pathogen and the causative agent of melioidosis, a spectrum of potentially fatal diseases endemic in Northern Australia and South-East Asia. We demonstrate that B. pseudomallei rapidly modifies infected macrophage-like cells in a manner analagous to osteoclastogenesis. These alterations include multinucleation and the expression by infected cells of mRNA for factors required for osteoclastogenesis: the chemokines monocyte chemotactic protein 1 (MCP-1), macrophage inflammatory protein 1 gamma (MIP-1gamma), 'regulated on activation normal T cell expressed and secreted' (RANTES) and the transcription factor 'nuclear factor of activated T-cells cytoplasmic 1' (NFATc1). An increase in expression of these factors was also observed after infection with Burkholderia thailandensis. Expression of genes for the osteoclast markers calcitonin receptor (CTR), cathepsin K (CTSK) and tartrate-resistant acid phosphatase (TRAP) was also increased by B. pseudomallei-infected, but not by B. thailandensis-infected cells. The expression by B. pseudomallei-infected cells of these chemokine and osteoclast marker genes was remarkably similar to cells treated with RANKL, a stimulator of osteoclastogenesis. Analysis of dentine resorption by B. pseudomallei-induced osteoclast-like cells revealed that demineralization may occur but that authentic excavation does not take place under the tested conditions. Furthermore, we identified and characterized lfpA (for lactonase family protein A) in B. pseudomallei, which shares significant sequence similarity with the eukaryotic protein 'regucalcin', also known as 'senescence marker protein-30' (SMP-30). LfpA orthologues are widespread in prokaryotes and are well conserved, but are phylogenetically distinct from eukaryotic regucalcin orthologues. We demonstrate that lfpA mRNA expression is dramatically increased in association with macrophage-like cells. Mutation of lfpA significantly reduced expression of the tested host genes, relative to the response to wild-type B. pseudomallei. We also show that lfpA is required for optimal virulence in vivo.

译文

pseudomalei伯克霍尔德菌是一种兼性细胞内病原体,也是类鼻疽病的病原体,类鼻疽是澳大利亚北部和东南亚流行的一系列潜在致命疾病。我们证明假单胞菌以类似于破骨细胞发生的方式快速修饰感染的巨噬细胞样细胞。这些改变包括破骨细胞形成所需的因子的多核和感染细胞的mRNA表达: 趋化因子单核细胞趋化蛋白1 (MCP-1),巨噬细胞炎性蛋白1 γ (MIP-1gamma),“调节活化正常T细胞表达和分泌” (RANTES) 和转录因子 “活化T细胞胞质核因子1” (NFATc1)。感染泰国伯克霍尔德菌后,还观察到这些因子的表达增加。破骨细胞标记物降钙素受体 (CTR),组织蛋白酶K (CTSK) 和耐酒石酸酸性磷酸酶 (TRAP) 的基因表达也被假假性芽孢杆菌感染的细胞增加,但未被泰国芽孢杆菌感染的细胞增加。这些趋化因子和破骨细胞标记基因的假假单胞菌感染细胞的表达与用破骨细胞生成刺激物RANKL处理的细胞非常相似。假单胞菌诱导的破骨细胞样细胞对牙本质的吸收分析表明,可能会发生脱矿质,但在测试条件下不会发生真正的挖掘。此外,我们在假单胞菌中鉴定并鉴定了lfpA (用于内酯酶家族蛋白A),该蛋白与真核蛋白 “regucalin” (也称为 “衰老标记蛋白-30” (SMP-30)) 具有显着的序列相似性。LfpA直系同源物在原核生物中广泛存在,并且保存良好,但在系统发育上与真核生物regucalcin直系同源物不同。我们证明lfpA mRNA表达与巨噬细胞样细胞相关显着增加。相对于对野生型B.Pseudomalei的反应,lfpA的突变显着降低了所测试宿主基因的表达。我们还表明,lfpA是体内最佳毒力所必需的。

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