Andersson K, Magnusson K E, Majeed M, Stendahl O, Fällman M
Division of Medical Microbiology, Department of Health and Environment, Linköping University, SE-581 85 Linköping, Sweden.
Infect Immun. 1999 May;67(5):2567-74. doi: 10.1128/IAI.67.5.2567-2574.1999.
Pathogenic species of the genus Yersinia evade the bactericidal functions of phagocytes. This evasion is mediated through their virulence effectors, Yops, which act within target cells. In this study we investigated the effect of Yersinia pseudotuberculosis on Ca2+ signaling in polymorphonuclear neutrophils. The intracellular free calcium concentration in single adherent human neutrophils was monitored during bacterial infection and, in parallel, the encounter between the bacteria and cells was observed. When a plasmid-cured strain was used for infection, adherence of a single bacterium to the cellular surface induced a beta1 integrin-dependent transient increase in the intracellular concentration of free calcium. This was, however, not seen with Yop-expressing wild-type bacteria, which adhered to the cell surface without generating any Ca2+ signal. Importantly, the overall Ca2+ homeostasis was not affected by the wild-type strain; the Ca2+ signal mediated by the G-protein-coupled formyl-methionyl-leucyl-phenylalanine receptor was still functioning. Hence, the blocking effect was restricted to certain receptors and their signaling pathways. The use of different Yop mutant strains revealed that the protein tyrosine phosphatase YopH was responsible for the inhibition. This virulence determinant has previously been implicated in very rapid Yersinia-mediated effects on target cells as the key effector in the blockage of phagocytic uptake. The present finding, that Y. pseudotuberculosis, via YopH, specifically inhibits a self-induced immediate-early Ca2+ signal in neutrophils, offers more-detailed information concerning the effectiveness of this virulence effector and implies an effect on Ca2+-dependent, downstream signals.
耶尔森氏菌属的致病物种能够逃避吞噬细胞的杀菌功能。这种逃避是通过其毒力效应蛋白Yops介导的，Yops在靶细胞内发挥作用。在本研究中，我们调查了假结核耶尔森氏菌对多形核中性粒细胞中Ca2+信号传导的影响。在细菌感染期间监测单个贴壁人中性粒细胞内的游离钙浓度，同时观察细菌与细胞之间的相互作用。当使用质粒消除菌株进行感染时，单个细菌与细胞表面的粘附会诱导游离钙细胞内浓度的β1整合素依赖性短暂增加。然而，表达Yop的野生型细菌则不会出现这种情况，它们粘附在细胞表面而不产生任何Ca2+信号。重要的是，野生型菌株不会影响整体Ca2+稳态；由G蛋白偶联的甲酰甲硫氨酰亮氨酰苯丙氨酸受体介导的Ca2+信号仍在发挥作用。因此，阻断作用仅限于某些受体及其信号通路。使用不同的Yop突变菌株表明，蛋白酪氨酸磷酸酶YopH是造成这种抑制的原因。这种毒力决定因素先前被认为是耶尔森氏菌对靶细胞非常快速的作用的关键效应物，参与阻断吞噬作用。目前的发现表明，假结核耶尔森氏菌通过YopH特异性抑制中性粒细胞中自身诱导的早期Ca2+信号，这提供了关于这种毒力效应物有效性的更详细信息，并暗示其对Ca2+依赖性下游信号的影响。
