ABSTRACT
The type III secretion system (T3SS) is a clinically important virulence mechanism in
Pseudomonas aeruginosa
that secretes and translocates effector toxins into host cells, impeding the host's rapid innate immune response to infection. Inhibitors of T3SS may be useful as prophylactic or adjunctive therapeutic agents to augment the activity of antibiotics in
P. aeruginosa
infections, such as pneumonia and bacteremia. One such inhibitor, the phenoxyacetamide MBX 1641, exhibits very responsive structure-activity relationships, including striking stereoselectivity, in its inhibition of
P. aeruginosa
T3SS. These features suggest interaction with a specific, but unknown, protein target. Here, we identify the apparent molecular target by isolating inhibitor-resistant mutants and mapping the mutation sites by deep sequencing. Selection and sequencing of four independent mutants resistant to the phenoxyacetamide inhibitor MBX 2359 identified the T3SS gene
pscF
, encoding the needle apparatus, as the only locus of mutations common to all four strains. Transfer of the wild-type and mutated alleles of
pscF
, together with its chaperone and cochaperone genes
pscE
and
pscG
, to a Δ
pscF P. aeruginosa
strain demonstrated that each of the single-codon mutations in
pscF
is necessary and sufficient to provide secretion and translocation that is resistant to a variety of phenoxyacetamide inhibitor analogs but not to T3SS inhibitors with different chemical scaffolds. These results implicate the PscF needle protein as an apparent new molecular target for T3SS inhibitor discovery and suggest that three other chemically distinct T3SS inhibitors interact with one or more different targets or a different region of PscF.
摘要
III型分泌系统(T3SS)是铜绿假单胞菌中一种临床上重要的毒力机制。
铜绿假单胞菌
Ⅲ型分泌系统(T3SS)是铜绿假单胞菌的一种重要临床毒力机制,它能将效应毒素分泌并转运到宿主细胞中,从而阻碍宿主对感染做出快速的先天免疫反应。T3SS 抑制剂可作为预防或辅助治疗药物,增强抗生素在铜绿假单胞菌感染中的活性。
铜绿假单胞菌
感染(如肺炎和菌血症)的抗生素活性。其中一种抑制剂是苯氧乙酰胺 MBX 1641,它对铜绿假单胞菌的抑制表现出非常灵敏的结构-活性关系,包括显著的立体选择性。
铜绿假单胞菌
T3SS。这些特征表明它与一个特定但未知的蛋白质靶点相互作用。在这里,我们通过分离抑制剂抗性突变体并通过深度测序绘制突变位点图,确定了明显的分子靶标。对四个对苯氧乙酰胺抑制剂 MBX 2359 具有抗性的独立突变体进行筛选和测序,确定了 T3SS 基因
pscF
是所有四个菌株唯一共同的突变位点。将野生型和突变等位基因的
的野生型和突变等位基因
及其伴侣蛋白和辅助伴侣蛋白基因
pscE
和
基因
转变为 Δ
pscF 铜绿微囊藻
菌株中的每个单密码子突变都证明了
单密码子突变
中的每个单密码子突变对提供分泌和转运是必要且足够的,这些分泌和转运对多种苯氧乙酰胺抑制剂类似物具有抗性,但对具有不同化学支架的 T3SS 抑制剂没有抗性。这些结果表明,PscF 针蛋白显然是发现 T3SS 抑制剂的一个新分子靶点,并表明其他三种化学性质不同的 T3SS 抑制剂与 PscF 的一个或多个不同靶点或不同区域相互作用。