Spa13 of Shigella flexneri has a dual role: chaperone escort and export gate-activator switch of the type III secretion system
Spa13 of Shigella flexneri has a dual role: chaperone escort and export gate-activator switch of the type III secretion system
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DOI：
10.1099/mic.0.071712-0
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发表时间：
2014-01-01
期刊：
影响因子：
2.8
通讯作者：
Allaoui, Abdelmounaaim
中科院分区：
文献类型：
--
作者：
Cherradi, Youness;Hachani, Abderrahman;Allaoui, Abdelmounaaim
许多革兰氏阴性病原体使用III型分泌器（T3 SA）将毒力因子注入真核细胞。福氏志贺菌T3SA跨越细菌包膜，其组装需要类似于20 mxi和spa基因的产物。尽管在理解T3SA如何组装方面取得了进展，但几种预测的可溶性组分（如Spa13）的作用仍然难以捉摸。在这里，我们表明，spa13突变体的分泌缺陷与缺乏T3SA组装，这部分是由于针组件MxiH的不稳定性。与耶尔森氏菌对应物相反，Spa13不是分泌蛋白。我们确定了Spa13与ATP酶Spa47、C环蛋白Spa33和内膜蛋白Spa40之间的相互作用网络。此外，我们揭示了Spa13与内膜MxiA的相互作用，并表明WT背景中MxiA的大胞质结构域的过表达关闭了分泌。最后，我们证明了Spa13与Spa40的切割形式和转运蛋白伴侣IpgC相互作用，表明Spa13在分泌层次转换过程中进行干预。总的来说，我们的研究结果支持Spa13作为伴侣护送和出口门激活开关的双重作用。
The type III secretion apparatus (T3SA) is used by numerous Gram-negative pathogens to inject virulence factors into eukaryotic cells. The Shigella flexneri T3SA spans the bacterial envelope and its assembly requires the products of similar to 20 mxi and spa genes. Despite progress made in understanding how the T3SA is assembled, the role of several predicted soluble components, such as Spa13, remains elusive. Here, we show that the secretion defect of the spa13 mutant is associated with lack of T3SA assembly which is partly due to the instability of the needle component MxiH. In contrast to its Yersinia counterpart, Spa13 is not a secreted protein. We identified a network of interactions between Spa13 and the ATPase Spa47, the C-ring protein Spa33, and the inner-membrane protein Spa40. Moreover, we revealed a Spa13 interaction with the inner-membrane MxiA and showed that overexpression of the large cytoplasmic domain of MxiA in the WT background shuts off secretion. Lastly, we demonstrated that Spa13 interacts with the cleaved form of Spa40 and with the translocator chaperone IpgC, suggesting that Spa13 intervenes during the secretion hierarchy switch process. Collectively, our results support a dual role of Spa13 as a chaperone escort and as an export gate-activator switch.