以前的研究工作从肠道致病性大肠杆菌识别出一组效应物，它们能抑制宿主“核因子-kB” (NF-kB) 信号作用，而它们当中只有一个，即NleB，是活体中细菌毒性所需的。本期Nature上发表的两篇论文演示了NleB作用的独特机制。它直接以死亡受体信号复合物为作用目标，结合到包括TNF受体、FAS、RIPK1、TRADD 和FADD在内的多种含DD的蛋白的“死亡域”(DD) 上。DD被发现起一个N-acetylglucosamine (GlcNAc) 转移酶的作用，后者修饰一个保守的DD精氨酸，阻断“受体-适配体”相互作用。这些发现表明，GlcNAc修饰是细菌毒性所必需的，能够调控死亡受体信号作用。（生物谷 Bioon.com）
生物谷推荐的英文摘要
Nature doi:10.1038/nature12436
Pathogen blocks host death receptor signalling by arginine GlcNAcylation of death domains
Shan Li, Li Zhang, Qing Yao, Lin Li, Na Dong, Jie Rong, Wenqing Gao, Xiaojun Ding, Liming Sun, Xing Chen, She Chen & Feng Shao
The tumour necrosis factor (TNF) family is crucial for immune homeostasis, cell death and inflammation. These cytokines are recognized by members of the TNF receptor (TNFR) family of death receptors, including TNFR1 and TNFR2, and FAS and TNF-related apoptosis-inducing ligand (TRAIL) receptors1. Death receptor signalling requires death-domain-mediated homotypic/heterotypic interactions between the receptor and its downstream adaptors, including TNFR1-associated death domain protein (TRADD) and FAS-associated death domain protein (FADD)2. Here we discover that death domains in several proteins, including TRADD, FADD, RIPK1 and TNFR1, were directly inactivated by NleB, an enteropathogenic Escherichia coli (EPEC) type III secretion system effector known to inhibit host nuclear factor-κB (NF-κB) signalling3, 4. NleB contained an unprecedented N-acetylglucosamine (GlcNAc) transferase activity that specifically modified a conserved arginine in these death domains (Arg 235 in the TRADD death domain). NleB GlcNAcylation (the addition of GlcNAc onto a protein side chain) of death domains blocked homotypic/heterotypic death domain interactions and assembly of the oligomeric TNFR1 complex, thereby disrupting TNF signalling in EPEC-infected cells, including NF-κB signalling, apoptosis and necroptosis. Type-III-delivered NleB also blocked FAS ligand and TRAIL-induced cell death by preventing formation of a FADD-mediated death-inducing signalling complex (DISC). The arginine GlcNAc transferase activity of NleB was required for bacterial colonization in the mouse model of EPEC infection. The mechanism of action of NleB represents a new model by which bacteria counteract host defences, and also a previously unappreciated post-translational modification.
