School of Molecular and Biomedical Science, University of Adelaide, Adelaide, South Australia, Australia.
PLoS One. 2012;7(5):e36312. doi: 10.1371/journal.pone.0036312. Epub 2012 May 15.
Capsule polysaccharide is a major virulence factor for a wide range of bacterial pathogens, including Streptococcus pneumoniae. The biosynthesis of Wzy-dependent capsules in both gram-negative and -positive bacteria is regulated by a system involving a protein tyrosine phosphatase (PTP) and a protein tyrosine kinase. However, how the system functions is still controversial. In Streptococcus pneumoniae, a major human pathogen, the system is present in all but 2 of the 93 serotypes found to date. In order to study this regulation further, we performed a screen to find inhibitors of the phosphatase, CpsB. This led to the observation that a recently discovered marine sponge metabolite, fascioquinol E, inhibited CpsB phosphatase activity both in vitro and in vivo at concentrations that did not affect the growth of the bacteria. This inhibition resulted in decreased capsule synthesis in D39 and Type 1 S. pneumoniae. Furthermore, concentrations of Fascioquinol E that inhibited capsule also lead to increased attachment of pneumococci to a macrophage cell line, suggesting that this compound would inhibit the virulence of the pathogen. Interestingly, this compound also inhibited the phosphatase activity of the structurally unrelated gram-negative PTP, Wzb, which belongs to separate family of protein tyrosine phosphatases. Furthermore, incubation with Klebsiella pneumoniae, which contains a homologous phosphatase, resulted in decreased capsule synthesis. Taken together, these data provide evidence that PTPs are critical for Wzy-dependent capsule production across a spectrum of bacteria, and as such represents a valuable new molecular target for the development of anti-virulence antibacterials.
荚膜多糖是多种细菌病原体（包括肺炎链球菌）的主要毒力因子。革兰氏阴性和阳性细菌中 Wzy 依赖性荚膜的生物合成受涉及蛋白酪氨酸磷酸酶（PTP）和蛋白酪氨酸激酶的系统调节。然而，该系统的功能仍存在争议。在主要的人类病原体肺炎链球菌中，该系统存在于迄今为止发现的 93 种血清型中的 91 种，只有 2 种不存在。为了进一步研究这种调节，我们进行了筛选以寻找磷酸酶 CpsB 的抑制剂。这导致观察到最近发现的海洋海绵代谢物 fascioquinol E 在不影响细菌生长的浓度下，在体外和体内均抑制 CpsB 磷酸酶活性。这种抑制导致 D39 和 1 型 S 肺炎链球菌荚膜合成减少。此外，抑制荚膜合成的 Fascioquinol E 浓度也导致肺炎球菌对巨噬细胞系的附着增加，表明该化合物会抑制病原体的毒力。有趣的是，该化合物还抑制了结构上不相关的革兰氏阴性 PTP Wzb 的磷酸酶活性，Wzb 属于蛋白酪氨酸磷酸酶的单独家族。此外，与含有同源磷酸酶的肺炎克雷伯菌孵育会导致荚膜合成减少。综上所述，这些数据提供了证据表明 PTP 对于 Wzy 依赖性荚膜产生在一系列细菌中至关重要，因此代表了开发抗毒力抗菌药物的有价值的新分子靶标。
