PhoPQ-mediated regulation produces a more robust permeability barrier in the outer membrane of Salmonella enterica serovar Typhimurium
PhoPQ-mediated regulation produces a more robust permeability barrier in the outer membrane of Salmonella enterica serovar Typhimurium
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DOI：
10.1128/jb.00973-07
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发表时间：
2007-10-01
影响因子：
3.2
通讯作者：
Nikaido, Hiroshi
中科院分区：
文献类型：
--
作者：
Murata, Takeshi;Tseng, Will;Nikaido, Hiroshi
鼠伤寒沙门氏菌的PhoPQ双组分系统产生脂多糖的脂质A结构域的重塑，包括PagP催化的棕榈酰残基的加成、PmrAB调节的阳离子糖4-氨基阿拉伯糖和磷酸乙醇胺的加成以及LpxO催化的2-OH基团到脂肪酸之一上的加成。通过使用染料乙锭，尼罗红，曙红Y穿过外膜的扩散速率，以及细胞对大的亲脂性试剂的敏感性，我们评估了该膜作为渗透性屏障的功能。我们发现，在PhoP组成型菌株的重塑过程中产生的外膜，作为一个非常有效的渗透性屏障的环境中，是穷人的二价阳离子或含有阳离子肽，而它的情况下，在phoP无效突变体产生的外膜严重损害其屏障功能在这些条件下。从PhoP组成型菌株中去除脂质A-重塑功能的组合表明，已知的修饰反应解释了PhoPQ调节的渗透性变化的主要部分。我们认为，重塑的双层的屏障性能的增加是重要的，使病原体更耐应力，它遇到的主机，包括攻击的阳离子抗菌肽。另一方面，药物诱导的杀伤测定表明，含有未修饰的脂质A的外膜在高浓度（例如，5 mM）的Mg 2+。
The PhoPQ two-component system of Salmonella enterica serovar Typhimurium produces a remodeling of the lipid A domain of the lipopolysaccharide, including the PagP-catalyzed addition of palmitoyl residue, the PmrAB-regulated addition of the cationic sugar 4-aminoarabinose and phosphoethanolamine, and the LpxO-catalyzed addition of a 2-OH group onto one of the fatty acids. By using the diffusion rates of the dyes ethidium, Nile red, and eosin Y across the outer membrane, as well as the susceptibility of cells to large, lipophilic agents, we evaluated the function of this membrane as a permeability barrier. We found that the remodeling process in PhoP-constitutive strains produces an outer membrane that serves as a very effective permeability barrier in an environment that is poor in divalent cations or that contains cationic peptides, whereas its absence in phoP null mutants produces an outer membrane severely compromised in its barrier function under these conditions. Removing combinations of the lipid A-remodeling functions from a PhoP-constitutive strain showed that the known modification reactions explain a major part of the PhoPQ-regulated changes in permeability. We believe that the increased barrier property of the remodeled bilayer is important in making the pathogen more resistant to the stresses that it encounters in the host, including attack by the cationic antimicrobial peptides. On the other hand, drug-induced killing assays suggest that the outer membrane containing unmodified lipid A may serve as a better barrier in the presence of high concentrations (e.g., 5 mM) of Mg2+.