D-alanylation of lipoteichoic acids confers resistance to cationic peptides in group B streptococcus by increasing the cell wall density.
D-alanylation of lipoteichoic acids confers resistance to cationic peptides in group B streptococcus by increasing the cell wall density.
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DOI：
10.1371/journal.ppat.1002891
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发表时间：
2012-09
期刊：
影响因子：
6.7
通讯作者：
Shai Y
中科院分区：
文献类型：
--
作者：
Saar-Dover R;Bitler A;Nezer R;Shmuel-Galia L;Firon A;Shimoni E;Trieu-Cuot P;Shai Y
阳离子抗菌肽(CAMP)是天然免疫系统抵御入侵微生物病原体的第一道防线。革兰氏阳性细菌可以通过用D-丙氨酸修饰阴离子磷壁酸(TA)来抵抗cAMP，但确切的耐药机制尚不完全清楚。在这里，我们利用不同的功能和生物物理方法来研究人类病原体B组链球菌(GBS)与一系列具有不同性质的cAMP的相互作用。数据显示：(I)脂磷壁酸(LTAs)的D-丙氨酰化只增强了GBS对cAMP亚类的抗性，并且抗药性与cAMP长度和电荷密度之间存在直接关系；(Ii)由于LTAS阴离子电荷的减少而产生的抗药性并不是由于结合多肽对细菌的减少所致；(Iii)D-丙氨酰化极有可能改变LTAS的构象，从而导致细胞壁密度增加，并减少cAMP对细胞壁的穿透。此外，原子力显微镜显示，野生型GBS菌株的细胞壁表面硬度增加到dltA突变体的20倍以上。我们认为，LTAS的D-丙氨酸化主要是通过降低细胞壁的柔韧性和渗透性，而不是通过减少多肽与细胞表面的静电相互作用来提供对线性cAMP的保护。总体而言，我们的发现揭示了细胞壁对cAMP的重要保护作用，并扩大了我们对细菌耐药性机制的理解。阳离子抗菌肽(CAMP)是天然免疫的重要进化保守元件，其杀伤机制涉及细菌细胞壁的渗透。因此，革兰氏阳性细菌可以通过在加入D-丙氨基残基后修改阴离子磷壁酸(TA)来中和它们的表面电荷来抵抗cAMP，这一反应是由DLT操纵子基因产物催化的。在这里，我们证明了这种电化学修饰改变了B组链球菌细胞壁的屏障属性，并使DLT操纵子活性失活导致cAMP敏感性。然而，尽管突变体的表面电荷显著增加，但没有观察到cAMP的静电结合增加。相反，D-丙氨酸的掺入通过减少cAMP对细胞壁的穿透来保护细菌的膜。因此，DLT突变体更容易被cAMP穿孔，其细胞壁纳米结构显著改变。总体而言，我们展示了细胞壁对cAMP的一种新的保护作用，这应该使细菌入侵者能够在宿主的定居后存活。
Cationic antimicrobial peptides (CAMPs) serve as the first line of defense of the innate immune system against invading microbial pathogens. Gram-positive bacteria can resist CAMPs by modifying their anionic teichoic acids (TAs) with D-alanine, but the exact mechanism of resistance is not fully understood. Here, we utilized various functional and biophysical approaches to investigate the interactions of the human pathogen Group B Streptococcus (GBS) with a series of CAMPs having different properties. The data reveal that: (i) D-alanylation of lipoteichoic acids (LTAs) enhance GBS resistance only to a subset of CAMPs and there is a direct correlation between resistance and CAMPs length and charge density; (ii) resistance due to reduced anionic charge of LTAs is not attributed to decreased amounts of bound peptides to the bacteria; and (iii) D-alanylation most probably alters the conformation of LTAs which results in increasing the cell wall density, as seen by Transmission Electron Microscopy, and reduces the penetration of CAMPs through the cell wall. Furthermore, Atomic Force Microscopy reveals increased surface rigidity of the cell wall of the wild-type GBS strain to more than 20-fold that of the dltA mutant. We propose that D-alanylation of LTAs confers protection against linear CAMPs mainly by decreasing the flexibility and permeability of the cell wall, rather than by reducing the electrostatic interactions of the peptide with the cell surface. Overall, our findings uncover an important protective role of the cell wall against CAMPs and extend our understanding of mechanisms of bacterial resistance. Cationic antimicrobial peptides (CAMPs) represent important evolutionarily conserved elements of innate immunity and their killing mechanism involves bacterial cell wall permeation. As a result, gram-positive bacteria can resist CAMPs by modifying their anionic teichoic acids (TAs) following incorporation of D-alanyl residues to neutralize their surface charge, a reaction catalyzed by the dlt operon gene product. Here, we demonstrate that this electrochemical modification changes the barrier properties of Group B Streptococcus cell wall and inactivation of the dlt operon activity results in CAMP sensitivity. However, despite the major increase in the surface charge of the mutant, no increased electrostatic binding of CAMPs is observed. Rather, D-alanine incorporation protects the bacterial membrane by reducing the penetration of CAMPs through the cell wall. Accordingly, a dlt mutant was more susceptible to perforation by CAMPs and its cell wall nanostructure was significantly altered. Overall, we demonstrate a novel protective role of the cell wall against CAMPs which should enable bacterial invaders to survive upon host's colonization.
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影响因子：
2.2
作者：
Eaton, Peter;Fernandes, Joao C.;Malcata, F. Xavier
通讯作者：
Malcata, F. Xavier
影响因子：
4.8
作者：
Koprivnjak, T;Peschel, A;Weiss, JP
通讯作者：
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影响因子：
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作者：
Dorschner, RA;Lopez-Garcia, B;Gallo, RL
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DOI：
10.1073/pnas.97.16.8856
发表时间：
2000-08-01
影响因子：
11.1
作者：
Hancock, REW;Scott, MG
通讯作者：
Scott, MG
影响因子：
3.2
作者：
Gutberlet, T;Frank, J;Fischer, W
通讯作者：
Fischer, W