Co-ordinate regulation of distinct host cell signalling pathways by multifunctional enteropathogenic Escherichia coli effector molecules
Co-ordinate regulation of distinct host cell signalling pathways by multifunctional enteropathogenic Escherichia coli effector molecules
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DOI：
10.1046/j.1365-2958.2002.02952.x
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发表时间：
2002-05-01
影响因子：
3.6
通讯作者：
Jepson, MA
中科院分区：
文献类型：
--
作者：
Kenny, B;Ellis, S;Jepson, MA
肠致病性大肠杆菌 (EPEC) 是小儿腹泻的主要原因，也是附着和消除 (A/E) 病原体家族的模型。 A/E 病原体编码 III 型分泌系统，将效应蛋白转移到宿主细胞中。 EPEC Tir 效应蛋白充当细菌表面蛋白 intimin 的受体，并参与粘附细菌下方不依赖于 Cdc42、富含肌动蛋白的基座结构的形成。在本文中，我们证明 EPEC 与 HeLa 细胞结合还会诱导不依赖于 Tir 的细胞骨架重排，这一点可以通过感染部位早期、短暂的丝状伪足样结构的形成来证明。丝状伪足的形成依赖于 EPEC Map 效应分子的表达，EPEC Map 效应分子是一种靶向线粒体并诱导其功能障碍的蛋白质。我们发现，Map 诱导的丝状伪足形成独立于线粒体靶向，并被 Cdc42 抑制性 WASP-CRIB 结构域的细胞表达所消除，这表明 Map 在宿主细胞中至少具有两种不同的功能。丝状伪足的短暂性与 EPEC 下调 Map 诱导的细胞信号传导的能力有关，该信号传导（如基座形成）依赖于 Tir 和 intimin 蛋白。 Tir 下调丝状伪足的能力因破坏假定的 GTP 酶激活蛋白 (GAP) 基序而受到损害，这表明 Tir 可能具有这种功能，其与 intimin 的相互作用触发了这种活性。此外，我们还发现 Map 诱导的细胞信号传导抑制基座形成，表明 Tir 和 Map 的细胞效应必须在感染过程中协调调节。讨论了 EPEC 效应分子的多功能性质在发病机制中的可能影响。
Enteropathogenic Escherichia coli (EPEC) is a major cause of paediatric diarrhoea and a model for the family of attaching and effacing (A/E) pathogens. A/E pathogens encode a type III secretion system to transfer effector proteins into host cells. The EPEC Tir effector protein acts as a receptor for the bacterial surface protein intimin and is involved in the formation of Cdc42-independent, actin-rich pedestal structures beneath the adhered bacteria. In this paper, we demonstrate that EPEC binding to HeLa cells also induces Tir-independent, cytoskeletal rearrangement evidenced by the early, transient formation of filopodia-like structures at sites of infection. Filopodia formation is dependent on expression of the EPEC Map effector molecule - a protein that targets mitochondria and induces their dysfunction. We show that Map-induced filopodia formation is independent of mitochondrial targeting and is abolished by cellular expression of the Cdc42 inhibitory WASP-CRIB domain, demonstrating that Map has at least two distinct functions in host cells. The transient nature of the filopodia is related to an ability of EPEC to downregulate Map-induced cell signalling that, like pedestal formation, was dependent on both Tir and intimin proteins. The ability of Tir to downregulate filopodia was impaired by disrupting a putative GTPase-activating protein (GAP) motif, suggesting that Tir may possess such a function, with its interaction with intimin triggering this activity. Furthermore, we also found that Map-induced cell signalling inhibits pedestal formation, revealing that the cellular effects of Tir and Map must be co-ordinately regu-lated during infection. Possible implications of the multifunctional nature of EPEC effector molecules in pathogenesis are discussed.