Regulatory mechanisms of type III secretion system by molecular chaperones and proteases in Salmonella enterica serovar Typhimurium.

鼠伤寒沙门氏菌与多种兼性细胞内病原体相似，可通过诱导应激蛋白对宿主机体巨噬细胞内的敌意条件做出反应。应激蛋白在功能上分为两类，分子伴侣和蛋白水解酶。我们发现分子伴侣和蛋白水解酶在沙门氏菌致病中具有重要作用。(1)AAA+蛋白水解酶家族对III型分泌系统的调节机制我们证明热休克蛋白ClpXP和Lon在BALB/c小鼠全身感染鼠伤寒沙门氏菌过程中起主要作用。ClpXP和Lon是鼠伤寒沙门氏菌在巨噬细胞内生存和生长所必需的。我们报道了ClpXP和Lon在鼠伤寒沙门氏菌中控制两个TTSS的表达，其中一个由鞭毛调节子编码，另一个由沙门氏菌致病性岛1(SPI1)编码。(2)分子伴侣巨噬细胞存活分析表明，DNAK/DNAJ缺失的突变体根本不能在巨噬细胞内存活或增殖。该突变体既不能侵袭培养的上皮细胞，也不能分泌任何SPI1编码的侵袭蛋白。(3)沙门氏菌活疫苗的研制。ClpXP或Lon缺陷型沙门氏菌免疫小鼠，可保护小鼠免受鼠伤寒沙门氏菌强毒株的攻击。攻毒后5天，攻毒沙门氏菌和免疫后的无毒沙门氏菌均从脾、肠系膜淋巴结、Peyer‘s结、甚至盲肠完全清除。我们的数据表明，破坏依赖于ATP的蛋白酶ClpXP或Lon的沙门氏菌在开发活疫苗株方面可能是有用的。

Salmonella enterica serovar Typhimurium, similar to various facultative intracellular pathogens, has been shown to respond to the hostile conditions inside macrophages of the host organism by inducing stress proteins. The stress proteins are functionally divided into two groups, molecular chaperones and proteases. We showed molecular chaperones and proteases have an important function for the Salmonella Pathogenicity.(1)Regulatory mechanisms of type III secretion system (TTSS) by AAA+ protease familyWe showed that the heat shock proteases ClpXP and Lon are essentially involved in systemic infection with S.enterica serovar Typhimurium in BALB/c mice. ClpXP and Lon are required for the survival and growth of S.enterica serovar Typhimurium within macrophages. We reported that ClpXP and Lon control the expression of two TTSSs in S.enterica serovar Typhimurium in which one is encoded by flagellar regulon and another is by Salmonella Pathogenicity Island 1(SPI1).(2)Regulatory mechanisms of TTSS by molecular chaperoneMacrophage survival assays revealed that the DnaK/DnaJ-depleted mutant could not survive or proliferate at all within macrophages. This mutant could neither invade cultured epithelial cells nor secrete any of the invasion proteins encoded within SPI1. We also showed that the DnaK/DnaJ-depleted mutant could not secrete flagellar proteins and SPI2 effector proteins encoded by TTSSs.(3)Development of Salmonella live vaccine.Immunization with the ClpXP-or Lon-deficient strain protected mice against oral challenge with the S. enterica serovar Typhimurium virulent strain. Both the challenged virulent and immunized avirulent salmonellae were completely cleared from the spleen, mesenteric lymph nodes, Peyer's patches, and even cecum 5 days after the challenge. Our data indicated that Salmonella with a disruption of the ATP-dependent protease ClpXP or Lon could be useful in developing a live vaccine strain.