Chinese Academy of Sciences scholar Immunity published a paper: MDA5-MAVS antiviral signaling pathway assembly program and activation mechanism

MDA5 is an allogeneic RNA monitoring protein in cells, and it is an important member of the RIG-I-like receptor family (RLRs)

Ubiquitination is an important post-translational modification in eukaryotes

On October 12, 2021, Zheng Jie’s team from Shanghai Institute of Materia Medica, Chinese Academy of Sciences published an online publication titled "Ordered assembly of the cytosolic RNA-sensing MDA5-MAVS signaling complex via binding to unanchored K63-linked in the Immunity magazine in the form of a Research Article.

First, the researchers established a K63-, K48-linked biochemical synthesis platform for ubiquitin chains, and prepared K63-polyUbn (2≤n≤14) of different lengths (Figure 1)

Figure 1: HDX-MS analysis of the effect of K63-polyUb (2≤n≤14) on the oligomerization of RLR CARDs

In order to study the K63-polyUbn-mediated assembly mechanism of ^MDA5 CARDs oligomers, the researchers used cryo-electron microscopy to analyze the structure of the complex of ^MDA5 CARDs and K63-polyUb ₁₃ with a resolution of 3.

Figure 2: Single particle cryo-electron microscopy showing the assembly mechanism of MDA5-MAVS CARD-CARD mediated by K63-polyUbn (n≥8)

At the same time, the researchers demonstrated for the first time that the CARDs of the human MDA5 full-length protein are in an open conformation and can bind to the long chain K63-polyUb ₁₀ through the biological macromolecule hydrogen-deuterium exchange mass spectrometry technology

Figure 3: HDX-MS analysis of the dynamic conformational changes and signal transduction mechanism of full-length MDA5 under the action of its recognition ligand or substrate (dsRNA/ATP/K63-polyUb)

In summary, the study found that long-chain, non-anchored K63-polyUb is similar to a "molecular bridge" through biological macromolecule hydrogen-deuterium exchange mass spectrometry and cryo-electron microscopy, which promotes the assembly of ^MDA5 CARDs tetramers and makes them form An excited conformation to recruit downstream ^MAVS CARD to further promote the oligomerization and activation of ^MAVS CARD (Figure 3)

　　Song Bin, a postdoctoral fellow at Shanghai Institute of Materia Medica, and Chen Yun, an American NIH Research Associate, are the first authors of the paper

　　Original link: https:// 

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