Department of Pathobiology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America.
PLoS Pathog. 2011 Sep;7(9):e1002241. doi: 10.1371/journal.ppat.1002241. Epub 2011 Sep 1.
Competence stimulating peptide (CSP) is a 17-amino acid peptide pheromone secreted by Streptococcus pneumoniae. Upon binding of CSP to its membrane-associated receptor kinase ComD, a cascade of signaling events is initiated, leading to activation of the competence regulon by the response regulator ComE. Genes encoding proteins that are involved in DNA uptake and transformation, as well as virulence, are upregulated. Previous studies have shown that disruption of key components in the competence regulon inhibits DNA transformation and attenuates virulence. Thus, synthetic analogues that competitively inhibit CSPs may serve as attractive drugs to control pneumococcal infection and to reduce horizontal gene transfer during infection. We performed amino acid substitutions on conserved amino acid residues of CSP1 in an effort to disable DNA transformation and to attenuate the virulence of S. pneumoniae. One of the mutated peptides, CSP1-E1A, inhibited development of competence in DNA transformation by outcompeting CSP1 in time and concentration-dependent manners. CSP1-E1A reduced the expression of pneumococcal virulence factors choline binding protein D (CbpD) and autolysin A (LytA) in vitro, and significantly reduced mouse mortality after lung infection. Furthermore, CSP1-E1A attenuated the acquisition of an antibiotic resistance gene and a capsule gene in vivo. Finally, we demonstrated that the strategy of using a peptide inhibitor is applicable to other CSP subtype, including CSP2. CSP1-E1A and CSP2-E1A were able to cross inhibit the induction of competence and DNA transformation in pneumococcal strains with incompatible ComD subtypes. These results demonstrate the applicability of generating competitive analogues of CSPs as drugs to control horizontal transfer of antibiotic resistance and virulence genes, and to attenuate virulence during infection by S. pneumoniae.
Competence stimulating peptide (CSP) 是肺炎链球菌分泌的一种 17 个氨基酸的肽类信息素。CSP 与膜相关受体激酶 ComD 结合后，会引发一系列信号事件，从而激活由应答调节因子 ComE 调控的感受态调控子。编码与 DNA 摄取和转化以及毒力相关的蛋白的基因被上调。先前的研究表明，破坏感受态调控子中的关键成分会抑制 DNA 转化并减弱毒力。因此，竞争性抑制 CSP 的合成类似物可能成为控制肺炎链球菌感染和减少感染过程中水平基因转移的有吸引力的药物。我们对 CSP1 中的保守氨基酸残基进行了氨基酸替换，以使其无法进行 DNA 转化并减弱肺炎链球菌的毒力。突变肽之一 CSP1-E1A 通过时间和浓度依赖性方式与 CSP1 竞争，从而抑制了 DNA 转化中的感受态发育。CSP1-E1A 降低了肺炎链球菌毒力因子胆碱结合蛋白 D (CbpD) 和自溶素 A (LytA) 的体外表达，显著降低了肺部感染后小鼠的死亡率。此外，CSP1-E1A 减弱了体内抗生素耐药基因和荚膜基因的获得。最后，我们证明了使用肽抑制剂的策略适用于其他 CSP 亚型，包括 CSP2。CSP1-E1A 和 CSP2-E1A 能够交叉抑制不兼容 ComD 亚型的肺炎链球菌菌株中感受态的诱导和 DNA 转化。这些结果表明，生成 CSP 的竞争性类似物作为药物来控制抗生素耐药性和毒力基因的水平转移，并减弱肺炎链球菌感染期间的毒力是可行的。
