Broich Markus, Rydzewski Kerstin, McNealy Tamara L, Marre Reinhard, Flieger Antje
Pathogenesis of Legionella Infection NG5, Robert Koch-Institut, Nordufer 20, D-13353 Berlin, Germany.
J Bacteriol. 2006 Feb;188(4):1218-26. doi: 10.1128/JB.188.4.1218-1226.2006.
Legionella pneumophila possesses a variety of secreted and cell-associated hydrolytic activities that could be involved in pathogenesis. The activities include phospholipase A, lysophospholipase A, glycerophospholipid:cholesterol acyltransferase, lipase, protease, phosphatase, RNase, and p-nitrophenylphosphorylcholine (p-NPPC) hydrolase. Up to now, there have been no data available on the regulation of the enzymes in L. pneumophila and no data at all concerning the regulation of bacterial phospholipases A. Therefore, we used L. pneumophila mutants in the genes coding for the global regulatory proteins RpoS and LetA to investigate the dependency of hydrolytic activities on a global regulatory network proposed to control important virulence traits in L. pneumophila. Our results show that both L. pneumophila rpoS and letA mutants exhibit on the one hand a dramatic reduction of secreted phospholipase A and glycerophospholipid:cholesterol acyltransferase activities, while on the other hand secreted lysophospholipase A and lipase activities were significantly increased during late logarithmic growth phase. The cell-associated phospholipase A, lysophospholipase A, and p-NPPC hydrolase activities, as well as the secreted protease, phosphatase, and p-NPPC hydrolase activities were significantly decreased in both of the mutant strains. Only cell-associated phosphatase activity was slightly increased. In contrast, RNase activity was not affected. The expression of plaC, coding for a secreted acyltransferase, phospholipase A, and lysophospholipase A, was found to be regulated by LetA and RpoS. In conclusion, our results show that RpoS and LetA affect phospholipase A, lysophospholipase A, acyltransferase, and other hydrolytic activities of L. pneumophila in a similar way, thereby corroborating the existence of the LetA/RpoS regulation cascade.
嗜肺军团菌具有多种分泌型和细胞相关的水解活性，这些活性可能与发病机制有关。这些活性包括磷脂酶A、溶血磷脂酶A、甘油磷脂：胆固醇酰基转移酶、脂肪酶、蛋白酶、磷酸酶、核糖核酸酶和对硝基苯基磷酸胆碱（p-NPPC）水解酶。到目前为止，尚无关于嗜肺军团菌中这些酶调控的相关数据，对于细菌磷脂酶A的调控更是完全没有数据。因此，我们使用编码全局调节蛋白RpoS和LetA的基因中的嗜肺军团菌突变体，来研究水解活性对一个被认为控制嗜肺军团菌重要毒力特性的全局调节网络的依赖性。我们的结果表明，嗜肺军团菌rpoS和letA突变体一方面表现出分泌型磷脂酶A和甘油磷脂：胆固醇酰基转移酶活性的显著降低，而另一方面，在对数生长后期，分泌型溶血磷脂酶A和脂肪酶活性显著增加。在这两种突变菌株中，细胞相关的磷脂酶A、溶血磷脂酶A和p-NPPC水解酶活性，以及分泌型蛋白酶、磷酸酶和p-NPPC水解酶活性均显著降低。只有细胞相关的磷酸酶活性略有增加。相比之下，核糖核酸酶活性不受影响。发现编码分泌型酰基转移酶、磷脂酶A和溶血磷脂酶A的plaC的表达受LetA和RpoS调控。总之，我们的结果表明，RpoS和LetA以相似的方式影响嗜肺军团菌的磷脂酶A、溶血磷脂酶A、酰基转移酶和其他水解活性，从而证实了LetA/RpoS调节级联的存在。
