Structural insights into RIP3-mediated necroptotic signaling
Tian Xie1, Wei Peng, Chuangye Yan
1Ministry of Education Protein Science Laboratory, Tsinghua-Peking Joint Center for Life Sciences, Center for Structural Biology, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China.
Cell Reports
|October 8, 2013
Summary
Researchers elucidated the structural basis of RIP3 kinase binding to its substrate MLKL, revealing key conformational changes essential for necroptosis signaling. This structural insight clarifies how RIP3 recognizes and interacts with MLKL.
Area of Science:
- Molecular Biology
- Cell Death Pathways
- Structural Biology
Background:
- Receptor-interacting protein kinase 3 (RIP3) is a critical upstream kinase in the programmed cell death pathway known as necroptosis.
- The pseudokinase mixed lineage kinase domain-like protein (MLKL) acts as a substrate for RIP3, mediating downstream necroptotic signaling.
- The precise molecular mechanism governing RIP3's recognition and phosphorylation of MLKL has remained elusive.
Purpose of the Study:
- To determine the structural mechanisms underlying the interaction between the RIP3 kinase domain and the MLKL kinase-like domain.
- To elucidate how RIP3 recognizes and binds to MLKL, and how this binding influences their respective conformations.
- To understand the role of MLKL phosphorylation by RIP3 in complex formation and necroptosis signaling.
Main Methods:
- X-ray crystallography was employed to determine the structures of the mouse RIP3 kinase domain, the MLKL kinase-like domain, and their binary complex.
- Analysis of conformational changes in RIP3 and MLKL upon complex formation.
- Biochemical assays to assess the necessity of MLKL phosphorylation for stable RIP3-MLKL complex formation.
Main Results:
- Crystal structures revealed that both RIP3 and MLKL possess canonical kinase folds.
- Free RIP3 adopts an active conformation, while MLKL binding, stabilized by AMP-PNP, induces an inactive conformation in RIP3.
- Complex formation involves significant conformational rearrangements in the N- and C-lobes, αC helix, and activation loop of both RIP3 and MLKL; MLKL phosphorylation is not required for stable complex formation.
Conclusions:
- The study provides the first structural framework for understanding the RIP3-MLKL interaction in necroptosis.
- Conformational changes in RIP3 and MLKL are critical for complex assembly, independent of RIP3-mediated MLKL phosphorylation.
- These findings offer mechanistic insights into RIP3-driven necroptotic signaling and potential therapeutic targets.
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