Type IV secretion by Neisseria gonorrhoeae

描述（由申请人提供）：淋病奈瑟菌引起性传播疾病淋病，更严重的感染性盆腔炎（PID）和播散性淋球菌感染（DGI）。我们在N.淋病，表现出致病岛的特征。几种形式的淋球菌遗传岛（GGI）存在于疾病分离株中，约80%的淋球菌菌株携带某种形式的GGI。我们确定了一个肽聚糖水解酶（atlA）编码的GGI，并发现它是参与生产一种不寻常的细胞毒素来自细菌细胞壁。这种肽聚糖衍生的细胞毒素（PG-细胞毒素）与百日咳杆菌的气管细胞毒素相同，是淋球菌感染中的重要毒力因子。PG-细胞毒素导致器官培养中的输卵管纤毛细胞死亡，诱导大鼠关节炎，并诱导培养细胞中的IL-1和IL-6。atlA在遗传岛中的存在与引起DOT的菌株显著相关。 DNA测序显示，GGI编码一个推定的IV型分泌系统。IV型分泌系统包括质粒接合系统和毒力因子输出系统，并且一些IV型分泌系统进行这两个过程。GGI中推定的IV型分泌基因的突变导致DNA分泌的丧失。这些突变体还显示出对原代宫颈细胞的延迟粘附，并在与细胞结合时表现出不寻常的小菌落表型。atlA中的突变导致与其他IV型分泌突变相同的表型，并显示PG-细胞毒素产生减少。因此，PGIA是IV型分泌所必需的，并且直接或间接参与PG-细胞毒素的产生。这些结果表明，GGI编码一个活跃的IV型分泌系统，在N。淋病与宿主 该提案的目标包含在两个具体目标中。1)我们将设计突变以影响IV型分泌，并测试这些突变体的蛋白质、DNA和PG细胞毒素分泌。2)我们将检测分泌缺陷突变体的毒力相关表型，即，上皮细胞粘附和侵袭、细胞内存活和小集落形成。总体而言，这些研究旨在揭示这种新型分泌系统的分子机制，并确定以前未被认识到的在淋球菌感染中重要的毒力因子，这些因子可能作为化疗或免疫保护的新靶点。

DESCRIPTION (provided by applicant): Neisseria gonorrhoeae causes the sexually transmitted disease gonorrhea, the more serious infections pelvic inflammatory disease (PID) and disseminated gonococcal infection (DGI). We identified a 57 kb genetic island present in N. gonorrhoeae that shows the characteristics of a pathogenicity island. Several forms of the gonococcal genetic island (GGI) are present among disease isolates, with approximately 80 percent of gonococcal strains carrying some form of the GGI. We identified a peptidoglycan hydrolase (atlA) encoded in the GGI and found that it is involved in the production of an unusual cytotoxin derived from the bacterial cell wall. This peptidoglycan-derived cytotoxin (PG-cytotoxin) is identical to the tracheal cytotoxin of Bordetella pertussis and is an important virulence factor in gonococcal infections. PG-cytotoxin causes the death of ciliated fallopian tube cells in organ culture, induces arthritis in rats, and induces IL-1 and IL-6 in cultured cells. The presence of atlA in the genetic island is significantly correlated with strains that cause DOT. DNA sequencing revealed that the GGI encodes a putative type IV secretion system. Type IV secretion systems include plasmid conjugation systems and virulence factor export systems and some type IV secretion systems carry out both processes. Mutations in the putative type IV secretion genes in the GGI result in loss of DNA secretion. These mutants also show delayed adherence to primary cervical cells and exhibit an unusual microcolony phenotype upon binding to cells. Mutations in atlA result in the same phenotypes as the other type IV secretion mutations as well as showing decreased PG-cytotoxin production. Thus AtlA is necessary for type IV secretion and is either directly or indirectly involved in PG-cytotoxin production. These results suggest that the GGI encodes an active type IV secretion system important in interaction of N. gonorrhoeae with the host. The goals of this proposal are contained in two specific aims. 1) We will make mutations designed to affect type IV secretion and test these mutants for secretion of proteins, DNA, and PG-cytotoxin. 2) We will test mutants with defects in secretion for phenotypes relevant to virulence, i.e., epithelial cell adherence and invasion, intracellular survival, and microcolony formation. Overall, these studies are designed to reveal the molecular mechanisms of this novel secretion system and identify previously unrecognized virulence factors important in gonococcal infection which may serve as new targets for chemotherapy or immunoprotection.