RECON-Dependent Inflammation in Hepatocytes Enhances Listeria monocytogenes Cell-to-Cell Spread.
RECON-Dependent Inflammation in Hepatocytes Enhances Listeria monocytogenes Cell-to-Cell Spread.
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DOI：
10.1128/mbio.00526-18
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发表时间：
2018-05-15
期刊：
影响因子：
6.4
通讯作者：
Woodward JJ
中科院分区：
文献类型：
--
作者：
McFarland AP;Burke TP;Carletti AA;Glover RC;Tabakh H;Welch MD;Woodward JJ
氧化还原酶Recon是细菌来源的环二核苷酸(CDN)的高亲和力胞浆感受器。CDN结合抑制Recon的酶活性，从而促进炎症。在这项研究中，我们试图表征Recon对细胞内单核细胞增生性李斯特菌感染周期的影响，该细菌将环状双AMP(c-di-AMP)分泌到受感染宿主细胞的胞浆中。在这里，我们报告在感染Recon缺陷的肝细胞期间，表现出高炎症反应，单核细胞增多性乳杆菌表现出显著的细胞间传播。细菌传播的增强不能归因于PRFA或ActA的变化，这两个毒力因子对细胞内运动和细胞间传播至关重要。详细的显微镜分析显示，在没有Recon的情况下，单核细胞增多性乳杆菌的肌动蛋白尾长明显更长，而且有更多移动更快的细菌。互补实验表明，Recon对乳杆菌单核细胞增殖和肌动蛋白尾长的影响与其酶活性有关。重组核糖核酸酶活性抑制核因子-κB的激活，并被c-二AMP抑制。与这些先前的发现一致，我们发现在没有Recon的情况下，增强的NF-κB激活导致了单核细胞增多性乳杆菌在细胞间的扩散，并且单核细胞增多性乳杆菌的扩散与c-二腺苷的分泌相关。最后，我们发现，显著增加的NF-κB依赖的诱导型一氧化氮合酶的表达和一氧化氮的产生负责促进单核细胞增多性乳杆菌在细胞间的传播。本文提出的工作支持一种模型，即单核细胞增多性乳杆菌分泌c-diAMP抑制Recon的酶活性，促进NF-κB的激活和一氧化氮的产生，最终促进细胞间扩散。到目前为止，真核生物中的细菌CDN唯一被欣赏的是它们在天然免疫中激活胞浆感觉通路的能力。然而，目前尚不清楚主动分泌CDN的病原体是否从这一过程中受益。在这里，我们提供了CDNS分泌导致单核细胞增多性乳杆菌细胞间传播增强的证据。这是迄今为止未知的这些分子的作用，表明在某些情况下，单核细胞增多性乳杆菌可能受益于它们的分泌。分子表征显示，令人惊讶的是，一氧化氮是导致这种增强扩散的原因。病原体的作用是防止一氧化氮的产生，或者像单核细胞增多性乳杆菌一样，它们已经进化成抵抗其直接的抗菌作用。这项研究提供了证据，证明细胞内的细菌病原体不仅可以耐受感染过程中不可避免的一氧化氮，而且还可以利用这种多效性分子对宿主细胞造成的变化。
The oxidoreductase RECON is a high-affinity cytosolic sensor of bacterium-derived cyclic dinucleotides (CDNs). CDN binding inhibits RECON’s enzymatic activity and subsequently promotes inflammation. In this study, we sought to characterize the effects of RECON on the infection cycle of the intracellular bacterium Listeria monocytogenes, which secretes cyclic di-AMP (c-di-AMP) into the cytosol of infected host cells. Here, we report that during infection of RECON-deficient hepatocytes, which exhibit hyperinflammatory responses, L. monocytogenes exhibits significantly enhanced cell-to-cell spread. Enhanced bacterial spread could not be attributed to alterations in PrfA or ActA, two virulence factors critical for intracellular motility and intercellular spread. Detailed microscopic analyses revealed that in the absence of RECON, L. monocytogenes actin tail lengths were significantly longer and there was a larger number of faster-moving bacteria. Complementation experiments demonstrated that the effects of RECON on L. monocytogenes spread and actin tail lengths were linked to its enzymatic activity. RECON enzyme activity suppresses NF-κB activation and is inhibited by c-di-AMP. Consistent with these previous findings, we found that augmented NF-κB activation in the absence of RECON caused enhanced L. monocytogenes cell-to-cell spread and that L. monocytogenes spread correlated with c-di-AMP secretion. Finally, we discovered that, remarkably, increased NF-κB-dependent inducible nitric oxide synthase expression and nitric oxide production were responsible for promoting L. monocytogenes cell-to-cell spread. The work presented here supports a model whereby L. monocytogenes secretion of c-di-AMP inhibits RECON’s enzymatic activity, drives augmented NF-κB activation and nitric oxide production, and ultimately enhances intercellular spread. To date, bacterial CDNs in eukaryotes are solely appreciated for their capacity to activate cytosolic sensing pathways in innate immunity. However, it remains unclear whether pathogens that actively secrete CDNs benefit from this process. Here, we provide evidence that secretion of CDNs leads to enhancement of L. monocytogenes cell-to-cell spread. This is a heretofore-unknown role of these molecules and suggests L. monocytogenes may benefit from their secretion in certain contexts. Molecular characterization revealed that, surprisingly, nitric oxide was responsible for the enhanced spread. Pathogens act to prevent nitric oxide production or, like L. monocytogenes, they have evolved to resist its direct antimicrobial effects. This study provides evidence that intracellular bacterial pathogens not only tolerate nitric oxide, which is inevitably encountered during infection, but can also capitalize on the changes this pleiotropic molecule enacts on the host cell.