Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, Sweden.
Department of Biological Chemistry, University of California Los Angeles, Los Angeles, California, USA.
Nat Commun. 2021 May 10;12(1):2578. doi: 10.1038/s41467-021-22590-6.
MyD88 and MAL are Toll-like receptor (TLR) adaptors that signal to induce pro-inflammatory cytokine production. We previously observed that the TIR domain of MAL (MAL) forms filaments in vitro and induces formation of crystalline higher-order assemblies of the MyD88 TIR domain (MyD88). These crystals are too small for conventional X-ray crystallography, but are ideally suited to structure determination by microcrystal electron diffraction (MicroED) and serial femtosecond crystallography (SFX). Here, we present MicroED and SFX structures of the MyD88 assembly, which reveal a two-stranded higher-order assembly arrangement of TIR domains analogous to that seen previously for MAL. We demonstrate via mutagenesis that the MyD88 assembly interfaces are critical for TLR4 signaling in vivo, and we show that MAL promotes unidirectional assembly of MyD88. Collectively, our studies provide structural and mechanistic insight into TLR signal transduction and allow a direct comparison of the MicroED and SFX techniques.
MyD88 和 MAL 是 Toll 样受体 (TLR) 衔接子，可信号转导诱导促炎细胞因子的产生。我们之前观察到 MAL 的 TIR 结构域（MAL）在体外形成纤维，并诱导 MyD88 TIR 结构域（MyD88）形成结晶的更高阶组装体。这些晶体太小，不适合传统的 X 射线晶体学，但非常适合微晶体电子衍射 (MicroED) 和连续飞秒晶体学 (SFX) 的结构测定。在这里，我们展示了 MyD88 组装体的 MicroED 和 SFX 结构，这些结构揭示了 TIR 结构域的双链更高阶组装排列，类似于之前观察到的 MAL。我们通过突变分析证明了 MyD88 组装体界面对于体内 TLR4 信号转导至关重要，并表明 MAL 促进了 MyD88 的单向组装。总的来说，我们的研究提供了 TLR 信号转导的结构和机制见解，并允许对 MicroED 和 SFX 技术进行直接比较。
