SseK1 and SseK3 Type III Secretion System Effectors Inhibit NF-κB Signaling and Necroptotic Cell Death in Salmonella-Infected Macrophages.
SseK1 and SseK3 Type III Secretion System Effectors Inhibit NF-κB Signaling and Necroptotic Cell Death in Salmonella-Infected Macrophages.
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DOI：
10.1128/iai.00010-17
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发表时间：
2017-03
影响因子：
3.1
通讯作者：
Thurston TLM
中科院分区：
文献类型：
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作者：
Günster RA;Matthews SA;Holden DW;Thurston TLM
在宿主细胞内，如巨噬细胞，肠沙门氏菌通过SPI-2 III型分泌系统将毒力(效应)蛋白转移到其空泡膜上。以前的研究表明，当异位表达时，效应分子SseK1和SseK3可以抑制肿瘤坏死因子-α(Tumor-α)诱导的核因子-κB的激活。在这项研究中，我们证明了异位表达的SseK1、SseK2和SseK3抑制了肿瘤坏死因子-α诱导的，但不能抑制Toll样受体4或白细胞介素性诱导的NF-κB的激活。抑制需要SseK1和SseK3中的DXD基序，这是N-乙酰氨基葡萄糖转移到精氨酸残基(精氨酸-GlcN酰化)所必需的。在巨噬细胞感染过程中，SseK1和SseK3以相加的方式抑制NF-κB的活性。SseK3介导的对NF-κB激活的抑制不需要这个效应器唯一的宿主结合伙伴，E3-泛素连接酶TRIM32。在巨噬细胞感染过程中，SSEK蛋白也能抑制肿瘤坏死因子-α诱导的细胞死亡。尽管SseK1和SseK3通过异位表达抑制肿瘤坏死因子-α诱导的HeLa细胞的凋亡，但感染的巨噬细胞发生凋亡的百分比不依赖于SseK。相反，SseK蛋白抑制了巨噬细胞感染期间的坏死性细胞死亡。在感染的巨噬细胞中，SseK1和SseK3引起不同蛋白质的GlcN酰化，这表明这些效应物具有不同的底物特异性。事实上，SseK1导致了含有死亡结构域的蛋白FADD和Tradd的GlcN酰化，而SseK3的表达导致了Tradd的弱GlcN酰化，而不是FADD。另外，尚不清楚的底物可能解释了同时缺乏SseK1和SseK3的沙门氏菌菌株的添加表型。
Within host cells such as macrophages, Salmonella enterica translocates virulence (effector) proteins across its vacuolar membrane via the SPI-2 type III secretion system. Previously, it was shown that when expressed ectopically, the effectors SseK1 and SseK3 inhibit tumor necrosis factor alpha (TNF-α)-induced NF-κB activation. In this study, we show that ectopically expressed SseK1, SseK2, and SseK3 suppress TNF-α-induced, but not Toll-like receptor 4- or interleukin-induced, NF-κB activation. Inhibition required a DXD motif in SseK1 and SseK3, which is essential for the transfer of N-acetylglucosamine to arginine residues (arginine-GlcNAcylation). During macrophage infection, SseK1 and SseK3 inhibited NF-κB activity in an additive manner. SseK3-mediated inhibition of NF-κB activation did not require the only known host-binding partner of this effector, the E3-ubiquitin ligase TRIM32. SseK proteins also inhibited TNF-α-induced cell death during macrophage infection. Despite SseK1 and SseK3 inhibiting TNF-α-induced apoptosis upon ectopic expression in HeLa cells, the percentage of infected macrophages undergoing apoptosis was SseK independent. Instead, SseK proteins inhibited necroptotic cell death during macrophage infection. SseK1 and SseK3 caused GlcNAcylation of different proteins in infected macrophages, suggesting that these effectors have distinct substrate specificities. Indeed, SseK1 caused the GlcNAcylation of the death domain-containing proteins FADD and TRADD, whereas SseK3 expression resulted in weak GlcNAcylation of TRADD but not FADD. Additional, as-yet-unidentified substrates are likely to explain the additive phenotype of a Salmonella strain lacking both SseK1 and SseK3.