School of Biological Sciences, Nanyang Technological University, Singapore, 637551, Singapore.
NTU Institute of Structural Biology, Nanyang Technological University, Singapore, 636921, Singapore.
Nat Commun. 2018 Nov 26;9(1):4993. doi: 10.1038/s41467-018-07447-9.
Signals arising from bacterial infections are detected by pathogen recognition receptors (PRRs) and are transduced by specialized adapter proteins in mammalian cells. The Receptor-interacting-serine/threonine-protein kinase 2 (RIPK2 or RIP2) is such an adapter protein that is critical for signal propagation of the Nucleotide-binding-oligomerization-domain-containing proteins 1/2 (NOD1 and NOD2). Dysregulation of this signaling pathway leads to defects in bacterial detection and in some cases autoimmune diseases. Here, we show that the Caspase-activation-and-recruitment-domain (CARD) of RIP2 (RIP2-CARD) forms oligomeric structures upon stimulation by either NOD1-CARD or NOD2-2CARD. We reconstitute this complex, termed the RIPosome in vitro and solve the cryo-EM filament structure of the active RIP2-CARD complex at 4.1 Å resolution. The structure suggests potential mechanisms by which CARD domains from NOD1 and NOD2 initiate the oligomerization process of RIP2-CARD. Together with structure guided mutagenesis experiments at the CARD-CARD interfaces, we demonstrate molecular mechanisms how RIP2 is activated and self-propagating such signal.
细菌感染产生的信号被病原体识别受体 (PRRs) 检测，并在哺乳动物细胞中被专门的衔接蛋白转导。受体相互作用丝氨酸/苏氨酸蛋白激酶 2 (RIPK2 或 RIP2) 就是这样一种衔接蛋白，它是核苷酸结合寡聚化结构域蛋白 1/2 (NOD1 和 NOD2) 信号转导的关键。该信号通路的失调导致细菌检测缺陷，并在某些情况下导致自身免疫性疾病。在这里，我们表明 RIP2 的 Caspase-activation-and-recruitment-domain (CARD) (RIP2-CARD) 在受到 NOD1-CARD 或 NOD2-2CARD 的刺激时会形成寡聚体结构。我们在体外重新构建了这个复合物，称为 RIPosome，并解决了活性 RIP2-CARD 复合物的 cryo-EM 丝状结构，分辨率为 4.1 Å。该结构提出了 NOD1 和 NOD2 的 CARD 结构域如何启动 RIP2-CARD 寡聚化过程的潜在机制。结合 CARD-CARD 界面的结构引导突变实验，我们证明了 RIP2 如何被激活并自我传播这种信号的分子机制。
