A Pterin-Dependent Signaling Pathway Regulates a Dual-Function Diguanylate Cyclase-Phosphodiesterase Controlling Surface Attachment in Agrobacterium tumefaciens.
A Pterin-Dependent Signaling Pathway Regulates a Dual-Function Diguanylate Cyclase-Phosphodiesterase Controlling Surface Attachment in Agrobacterium tumefaciens.
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DOI：
10.1128/mbio.00156-15
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发表时间：
2015-06-30
期刊：
影响因子：
6.4
通讯作者：
Fuqua C
中科院分区：
文献类型：
--
作者：
Feirer N;Xu J;Allen KD;Koestler BJ;Bruger EL;Waters CM;White RH;Fuqua C
从运动到静止的转变是多种细菌重要的生活方式转换，通常受细胞内第二信使环二鸟苷一磷酸(c-di-GMP)的调节。一般来说，高浓度的c-di-GMP促进了细胞表面的附着，而信号水平低的细胞则保持运动状态。在植物病原菌根癌农杆菌中，c-di-GMP通过调节单极多糖(UPP)粘附素来控制附着和生物膜的形成。根癌农杆菌中c-di-GMP的水平部分受双功能二鸟苷环化酶-磷酸二酯酶(DGC-PDE)蛋白DCPA的控制。在本研究中，我们报道了DCPA在异源和天然遗传背景下具有c-di-GMP合成和降解活性，这种二元能力在GGDEF-EAL结构域蛋白中是不寻常的。DCPA的活性受一种称为PruA的蝶啶还原酶的调节，在PruA存在的情况下，DCPA充当PDE，而在PruA不存在的情况下，DCPA充当DGC。PruA的酶活性是控制DCPA并通过这种控制、附着和生物膜形成所必需的。细胞内分析表明，PruA负责一种新的蝶呤物种的产生。此外，DCPA活性的控制还需要PruR，这是一种直接编码DCPA上游的蛋白质，具有预测的钼紫蝶呤结合结构域。PruR被认为是PruA和DCPA之间的一种潜在的信号中间产物，其机制尚不清楚。本研究为蝶呤蛋白介导的信号通路提供了第一个原核样本，并为双功能DGC-PDE蛋白的调控提供了一个新的模型。病原菌通常附着在表面并形成称为生物膜的多细胞群落。生物膜具有内在的弹性，可能很难治疗，对常见的抗菌素具有抵抗力。了解细菌细胞如何转变为生物膜的生活方式对于开发新的治疗策略至关重要。我们已经确定了一种新的信号通路，它在模式病原菌根癌农杆菌的生物膜形成调节中起主导作用。这一控制途径涉及被称为蝶呤的小代谢物，在真核生物中得到了很好的研究，但这是细菌中依赖蝶呤的信号传递的第一个例子。所描述的途径控制细胞内重要的第二信使(环单磷酸二鸟苷)的水平，该信使调节关键的细菌过程，如生物膜的形成、运动性和毒力。蝶呤控制着一种酶的活性平衡，这种酶既合成又降解第二信使。这些发现揭示了一种复杂的、多步骤的调节这种酶的途径，可能会确定抗菌干预的新靶点。
The motile-to-sessile transition is an important lifestyle switch in diverse bacteria and is often regulated by the intracellular second messenger cyclic diguanylate monophosphate (c-di-GMP). In general, high c-di-GMP concentrations promote attachment to surfaces, whereas cells with low levels of signal remain motile. In the plant pathogen Agrobacterium tumefaciens, c-di-GMP controls attachment and biofilm formation via regulation of a unipolar polysaccharide (UPP) adhesin. The levels of c-di-GMP in A. tumefaciens are controlled in part by the dual-function diguanylate cyclase-phosphodiesterase (DGC-PDE) protein DcpA. In this study, we report that DcpA possesses both c-di-GMP synthesizing and degrading activities in heterologous and native genetic backgrounds, a binary capability that is unusual among GGDEF-EAL domain-containing proteins. DcpA activity is modulated by a pteridine reductase called PruA, with DcpA acting as a PDE in the presence of PruA and a DGC in its absence. PruA enzymatic activity is required for the control of DcpA and through this control, attachment and biofilm formation. Intracellular pterin analysis demonstrates that PruA is responsible for the production of a novel pterin species. In addition, the control of DcpA activity also requires PruR, a protein encoded directly upstream of DcpA with a predicted molybdopterin-binding domain. PruR is hypothesized to be a potential signaling intermediate between PruA and DcpA through an as-yet-unidentified mechanism. This study provides the first prokaryotic example of a pterin-mediated signaling pathway and a new model for the regulation of dual-function DGC-PDE proteins. Pathogenic bacteria often attach to surfaces and form multicellular communities called biofilms. Biofilms are inherently resilient and can be difficult to treat, resisting common antimicrobials. Understanding how bacterial cells transition to the biofilm lifestyle is essential in developing new therapeutic strategies. We have characterized a novel signaling pathway that plays a dominant role in the regulation of biofilm formation in the model pathogen Agrobacterium tumefaciens. This control pathway involves small metabolites called pterins, well studied in eukaryotes, but this is the first example of pterin-dependent signaling in bacteria. The described pathway controls levels of an important intracellular second messenger (cyclic diguanylate monophosphate) that regulates key bacterial processes such as biofilm formation, motility, and virulence. Pterins control the balance of activity for an enzyme that both synthesizes and degrades the second messenger. These findings reveal a complex, multistep pathway that modulates this enzyme, possibly identifying new targets for antibacterial intervention.