Moncrieffe Martin C, Grossmann J Günter, Gay Nicholas J
Department of Biochemistry, Cambridge University, Cambridge CB2 1GA, United Kingdom.
J Biol Chem. 2008 Nov 28;283(48):33447-54. doi: 10.1074/jbc.M805427200. Epub 2008 Oct 1.
The Drosophila Toll receptor is activated by the endogenous protein ligand Spätzle in response to microbial stimuli in immunity and spatial cues during embryonic development. Downstream signaling is mediated by the adaptor proteins Tube, the kinase Pelle, and the Drosophila homologue of myeloid differentiation primary response protein (dMyD88). Here we have characterized heterodimeric (dMyD88-Tube) and heterotrimeric (dMyD88-Tube-Pelle) death domain complexes. We show that both the heterodimeric and heterotrimeric complexes form kidney-shaped structures and that Tube is bivalent and has separate high affinity binding sites for dMyD88 and Pelle. Additionally we found no interaction between the isolated death domains of Pelle and dMyD88. These results indicate that the mode of assembly of the heterotrimeric dMyD88-Tube-Pelle complex downstream of the activated Toll receptor is unique. The measured dissociation constants for the interaction between the death domains of dMyD88 and Tube and of Pelle and a preformed dMyD88-Tube complex are used to propose a model of the early postreceptor events in Drosophila Toll receptor signaling.
果蝇Toll受体可被内源性蛋白配体斯帕兹勒（Spätzle）激活，以响应免疫过程中的微生物刺激以及胚胎发育期间的空间线索。下游信号传导由衔接蛋白Tube、激酶Pelle以及髓样分化初级反应蛋白的果蝇同源物（dMyD88）介导。在此，我们对异二聚体（dMyD88-Tube）和异三聚体（dMyD88-Tube-Pelle）死亡结构域复合物进行了表征。我们发现，异二聚体和异三聚体复合物均形成肾形结构，且Tube具有双价性，对dMyD88和Pelle具有独立的高亲和力结合位点。此外，我们未发现Pelle和dMyD88的分离死亡结构域之间存在相互作用。这些结果表明，活化的Toll受体下游异三聚体dMyD88-Tube-Pelle复合物的组装模式是独特的。所测得的dMyD88与Tube以及Pelle与预先形成的dMyD88-Tube复合物之间死亡结构域相互作用的解离常数，被用于提出果蝇Toll受体信号传导中受体后早期事件的模型。
