Download MendeleyStructural basis of human IL-18 sequestration by the decoy receptor IL-18 binding protein in inflammation and tumor immunity.
Detry, S., Andries, J., Bloch, Y., Gabay, C., Clancy, D.M., Savvides, S.N.(2022) J Biol Chem 298: 101908-101908
- PubMed: 35398099
- DOI: https://doi.org/10.1016/j.jbc.2022.101908
- Primary Citation of Related Structures:
7AL7 - PubMed Abstract:
Human Interleukin-18 (IL-18) is an omnipresent proinflammatory cytokine of the IL-1 family with central roles in autoimmune and inflammatory diseases and serves as a staple biomarker in the evaluation of inflammation in physiology and disease, including the inflammatory phase of COVID-19. The sequestration of IL-18 by its soluble decoy receptor IL-18-Binding Protein (IL-18BP) is critical to the regulation of IL-18 activity. Since an imbalance in expression and circulating levels of IL-18 is associated with disease, structural insights into how IL-18BP outcompetes binding of IL-18 by its cognate cell-surface receptors are highly desirable; however, the structure of human IL-18BP in complex with IL-18 has been elusive. Here, we elucidate the sequestration mechanism of human IL-18 mediated by IL-18BP based on the crystal structure of the IL-18:IL-18BP complex. These detailed structural snapshots reveal the interaction landscape leading to the ultra-high affinity of IL-18BP toward IL-18 and identify substantial differences with respect to previously characterized complexes of IL-18 with IL-18BP of viral origin. Furthermore, our structure captured a fortuitous higher-order assembly between IL-18 and IL-18BP coordinated by a disulfide-bond distal to the binding surface connecting IL-18 and IL-18BP molecules from different complexes, resulting in a novel tetramer with 2:2 stoichiometry. This tetrapartite assembly was found to restrain IL-18 activity more effectively than the canonical 1:1 complex. Collectively, our findings provide a framework for innovative, structure-driven therapeutic strategies and further functional interrogation of IL-18 in physiology and disease.
Organizational Affiliation:
Unit for Structural Biology, Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium; Unit for Structural Biology, VIB Center for Inflammation Research, Ghent, Belgium.
