Boyd A P, Sory M P, Iriarte M, Cornelis G R
International Institute of Cellular and Molecular Pathology and Faculté de Médecine, Université Catholique de Louvain, Brussels, Belgium.
Mol Microbiol. 1998 Jan;27(2):425-36. doi: 10.1046/j.1365-2958.1998.00691.x.
Yersiniae are equipped with the Yop virulon, an apparatus that allows extracellular bacteria to deliver toxic Yop proteins inside the host cell cytosol in order to sabotage the communication networks of the host cell or even to cause cell death. LcrG is a component of the Yop virulon involved in the regulation of secretion of the Yops. In this paper, we show that LcrG can bind HeLa cells, and we analyse the role of proteoglycans in this phenomenon. Treatment of the HeLa cells with heparinase I, but not chondroitinase ABC, led to inhibition of binding. Competition assays indicated that heparin and dextran sulphate strongly inhibited binding, but that other glycosaminoglycans did not. This demonstrated that binding of HeLa cells to purified LcrG is caused by heparan sulphate proteoglycans. LcrG could bind directly to heparin-agarose beads and, in agreement with these results, analysis of the protein sequence of Yersinia enterocolitica LcrG revealed heparin-binding motifs. In vitro production and secretion by Y. enterocolitica of the Yops was unaffected by the addition of heparin. However, the addition of exogenous heparin decreased the level of YopE-Cya translocation into HeLa cells. A similar decrease was seen with dextran sulphate, whereas the other glycosaminoglycans tested had no significant effect. Translocation was also decreased by treatment of HeLa cells with heparinitase, but not with chondroitinase. Thus, heparan sulphate proteoglycans have an important role to play in translocation. The interaction between LcrG and heparan sulphate anchored at the surface of HeLa cells could be a signal triggering deployment of the Yop translocation machinery. This is the first report of a eukaryotic receptor interacting with the type III secretion and associated translocation machinery of Yersinia or of other bacteria.
耶尔森氏菌配备有Yop毒力蛋白分泌系统，该系统能使胞外细菌将有毒的Yop蛋白递送至宿主细胞胞质溶胶中，从而破坏宿主细胞的通讯网络甚至导致细胞死亡。LcrG是Yop毒力蛋白分泌系统的一个组成部分，参与Yop蛋白的分泌调节。在本文中，我们发现LcrG能结合HeLa细胞，并分析了蛋白聚糖在这一现象中的作用。用肝素酶I而非软骨素酶ABC处理HeLa细胞，导致结合受到抑制。竞争试验表明，肝素和硫酸葡聚糖强烈抑制结合，但其他糖胺聚糖则无此作用。这表明HeLa细胞与纯化的LcrG的结合是由硫酸乙酰肝素蛋白聚糖引起的。LcrG能直接结合肝素琼脂糖珠，与这些结果一致，对小肠结肠炎耶尔森氏菌LcrG的蛋白质序列分析揭示了肝素结合基序。小肠结肠炎耶尔森氏菌在体外产生和分泌Yop蛋白不受肝素添加的影响。然而，添加外源性肝素会降低YopE-Cya转运至HeLa细胞中的水平。硫酸葡聚糖也有类似的降低作用，而所测试的其他糖胺聚糖则无显著影响。用肝素酶处理HeLa细胞也会降低转运水平，但用软骨素酶处理则无此作用。因此，硫酸乙酰肝素蛋白聚糖在转运过程中发挥着重要作用。LcrG与锚定在HeLa细胞表面的硫酸乙酰肝素之间的相互作用可能是触发Yop转运机制部署的信号。这是关于真核受体与耶尔森氏菌或其他细菌的III型分泌及相关转运机制相互作用的首次报道。
