ABSTRACT
Bacteria require at least one pathway to rescue ribosomes stalled at the ends of mRNAs. The primary pathway for ribosome rescue is
trans
-translation, which is conserved in >99% of sequenced bacterial genomes. Some species also have backup systems, such as ArfA or ArfB, which can rescue ribosomes in the absence of sufficient
trans
-translation activity. Small-molecule inhibitors of ribosome rescue have broad-spectrum antimicrobial activity against bacteria grown in liquid culture. These compounds were tested against the tier 1 select agent
Francisella tularensis
to determine if they can limit bacterial proliferation during infection of eukaryotic cells. The inhibitors KKL-10 and KKL-40 exhibited exceptional antimicrobial activity against both attenuated and fully virulent strains of
F. tularensis
in vitro
and during
ex vivo
infection. Addition of KKL-10 or KKL-40 to macrophages or liver cells at any time after infection by
F. tularensis
prevented further bacterial proliferation. When macrophages were stimulated with the proinflammatory cytokine gamma interferon before being infected by
F. tularensis
, addition of KKL-10 or KKL-40 reduced intracellular bacteria by >99%, indicating that the combination of cytokine-induced stress and a nonfunctional ribosome rescue pathway is fatal to
F. tularensis
. Neither KKL-10 nor KKL-40 was cytotoxic to eukaryotic cells in culture. These results demonstrate that ribosome rescue is required for
F. tularensis
growth at all stages of its infection cycle and suggest that KKL-10 and KKL-40 are good lead compounds for antibiotic development.
摘要
细菌至少需要一种途径来挽救停滞在 mRNA 末端的核糖体。挽救核糖体的主要途径是
反式
-99%的已测序细菌基因组都保留了这一途径。有些物种还拥有后备系统,如 ArfA 或 ArfB,它们可以在缺乏足够的转译时挽救核糖体。
转
-转译活性。核糖体救援小分子抑制剂对液体培养的细菌具有广谱抗菌活性。这些化合物针对 1 级选择剂
土拉弗氏菌
进行了测试,以确定它们能否在真核细胞感染过程中限制细菌增殖。抑制剂 KKL-10 和 KKL-40 对减毒株和全毒株的土拉弗氏菌均表现出卓越的抗菌活性。
图拉真菌
在体外
和
体外
感染。在巨噬细胞或肝细胞感染 F. tularensis 后的任何时间向其添加 KKL-10 或 KKL-40
F. tularensis
可阻止细菌进一步增殖。当巨噬细胞在被 F. tularensis 感染前受到促炎细胞因子γ干扰素的刺激时,KKL-10 或 KKL-40 可阻止细菌进一步增殖。
土拉菌
KKL-10 或 KKL-40 能使细胞内的细菌减少 99%。
致命。
.KKL-10和KKL-40对培养中的真核细胞都没有细胞毒性。这些结果表明,核糖体救援是F.
图拉真菌
生长所需的核糖体救援,并表明 KKL-10 和 KKL-40 是开发抗生素的良好先导化合物。