Genetic Dissection of the Signaling Cascade that Controls Activation of the Shigella Type III Secretion System from the Needle Tip.
Genetic Dissection of the Signaling Cascade that Controls Activation of the Shigella Type III Secretion System from the Needle Tip.
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DOI：
10.1038/srep27649
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发表时间：
2016-06-09
影响因子：
4.6
通讯作者：
Blocker AJ
中科院分区：
文献类型：
--
作者：
Murillo I;Martinez-Argudo I;Blocker AJ
许多革兰氏阴性细菌病原体使用III型分泌系统（t3ss）产生毒力。志贺氏菌T3SS由一个中空的针组成，由MxiH制成，从细菌表面伸出，通过多聚体蛋白环固定在细菌膜上。针的顶端是尖端复合体（TC），由IpaD和IpaB组成。在与真核宿主细胞物理接触后，T3S被启动，导致真核细胞膜上形成由IpaB和IpaC组成的孔。通过针状和孔状通道，进一步的细菌蛋白被转移到宿主细胞内，以阻止其入侵。IpaD和针头参与了宿主细胞感应信号到T3S装置的转导。此外，具有感知能力的TC似乎由4台ipad和1台IpaB组成。然而，关于激活过程没有进一步的了解。为了研究IpaB在T3SS激活中的作用，我们使用随机诱变和遗传筛选分离了分泌失调的IpaB突变体。我们发现ipaB点突变导致分泌激活缺陷，有时会减少孔插入和宿主细胞入侵。我们还证明IpaB与TC内的IpaD和MxiH在分子内和分子间进行通信，因为影响这些相互作用的突变会损害信号转导。
Many Gram-negative bacterial pathogens use type III secretion systems (T3SSs) for virulence. The Shigella T3SS consists of a hollow needle, made of MxiH and protruding from the bacterial surface, anchored in both bacterial membranes by multimeric protein rings. Atop the needle lies the tip complex (TC), formed by IpaD and IpaB. Upon physical contact with eukaryotic host cells, T3S is initiated leading to formation of a pore in the eukaryotic cell membrane, which is made of IpaB and IpaC. Through the needle and pore channels, further bacterial proteins are translocated inside the host cell to meditate its invasion. IpaD and the needle are implicated in transduction of the host cell-sensing signal to the T3S apparatus. Furthermore, the sensing-competent TC seems formed of 4 IpaDs topped by 1 IpaB. However, nothing further is known about the activation process. To investigate IpaB’s role during T3SS activation, we isolated secretion-deregulated IpaB mutants using random mutagenesis and a genetic screen. We found ipaB point mutations in leading to defects in secretion activation, which sometimes diminished pore insertion and host cell invasion. We also demonstrated IpaB communicates intramolecularly and intermolecularly with IpaD and MxiH within the TC because mutations affecting these interactions impair signal transduction.