Interleukin-18 (IL-18) is a pro-inflammatory cytokine that belongs to the interleukin-1 (IL-1) superfamily. It plays an important role in host defense against microbes but also contributes to pathogenesis of several inflammatory diseases, including rheumatoid arthritis, septic shock and Crohn's disease. IL-18 signaling is initiated by its cell-surface binding to the receptor (IL-18R) alpha subunit, followed by the recruitment of the receptor beta subunit to form a ternary signaling complex. IL-18 activities are regulated in vivo by a naturally occurring antagonist, the IL-18 binding protein (IL-18BP) through a negative feedback mechanism. Poxviruses, including the smallpox (variola) virus, also express functional IL-18BP homologues to evade IL-18-mediated host immune responses. IL-18, IL-18R and IL-18BP are therefore attractive targets for developing therapeutics agonist inflammatory or infectious diseases where down- or up-modulating IL-18 activities is indicated. However, there is a lack of thorough understanding of how IL-18 activates its receptor and how IL-18BP inhibits IL-18. We propose to determine the crystal structures of various protein complexes of IL-18 with IL-18R or IL-18BP and perform functional studies based on the structural information. In addition, we will perform structure-based design of IL-18 variants that may either serve as a more effective cytokine capable of evading the neutralization of poxvirus IL-18BPs, or as a receptor antagonist capable of blocking IL-18 activities.
Aim 1. To determine the molecular mechanism by which IL-18BPs neutralize IL-18.
Aim 2. To determine the molecular mechanism by which IL-18 specifically recognizes 1 subunit of IL-18R.
Aim 3. To determine the molecular mechanism by which IL-18 triggers the hetero-dimerization of IL-18R1 and 2 subunits. The objective of this application is the detailed characterization of a collection of IL-18 complexes by a combination of biophysical and biochemical methods, including x-ray crystallography, Surface Plasmon Resonance (SPR) and IL-18 bioassay. Accomplishing this objective is an important first step for achieving our long-term goal of understanding how IL-18 activates its receptors to initiate cell signaling and how this activity is regulated by IL-18BP.This research obtains/assumes extra dimensions. Since the targeted proteins are of significant medical relevance, our studies will provide a platform for designing selective inhibitors that may ultimately be developed into new therapeutics against a number of human diseases. Public Health Relevance: Our contribution here is expected to provide detailed molecular recognition of IL-18 by IL-18BP and IL-18R. This contribution is significant because it will fill the gap of our current knowledge on IL-18 activation pathway, and will provide important clues on how to modulate IL-18 activity. It may benefit efforts in developing treatments against some autoimmune and inflammatory diseases, in developing immunotherapies against other infectious diseases and cancer and in combating bioterrorism.

Public Health Relevance

Our contribution here is expected to provide detailed molecular recognition of IL-18 by IL-18BP and IL-18R. This contribution is significant because it will fill the gap of our current knowledge on IL-18 activation pathway, and will provide important clues on how to modulate IL-18 activity. It may benefit efforts in developing treatments against some autoimmune and inflammatory diseases, in developing immunotherapies against other infectious diseases and cancer and in combating bioterrorism.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI081928-02
Application #
7893102
Study Section
Cellular and Molecular Immunology - A Study Section (CMIA)
Program Officer
Leitner, Wolfgang W
Project Start
2009-07-01
Project End
2013-06-30
Budget Start
2010-07-01
Budget End
2011-06-30
Support Year
2
Fiscal Year
2010
Total Cost
$329,617
Indirect Cost
Name
Oklahoma State University Stillwater
Department
Biochemistry
Type
Schools of Earth Sciences/Natur
DUNS #
049987720
City
Stillwater
State
OK
Country
United States
Zip Code
74078
Krumm, Brian; Xiang, Yan; Deng, Junpeng (2014) Structural biology of the IL-1 superfamily: key cytokines in the regulation of immune and inflammatory responses. Protein Sci 23:526-38
Zhang, Bing; Liu, Caini; Qian, Wen et al. (2014) Structure of the unique SEFIR domain from human interleukin 17 receptor A reveals a composite ligand-binding site containing a conserved ?-helix for Act1 binding and IL-17 signaling. Acta Crystallogr D Biol Crystallogr 70:1476-83
Zhang, Bing; Liu, Caini; Qian, Wen et al. (2013) Crystal structure of IL-17 receptor B SEFIR domain. J Immunol 190:2320-6
Wu, Xiang; Meng, Xiangzhi; Yan, Bo et al. (2012) Vaccinia virus virion membrane biogenesis protein A11 associates with viral membranes in a manner that requires the expression of another membrane biogenesis protein, A6. J Virol 86:11276-86
Peng, Xiao; Wang, Yuna; Kolli, Swapna et al. (2012) Physical and functional interaction between the ID1 and p65 for activation of NF-?B. Am J Physiol Cell Physiol 303:C267-77
Krumm, Brian; Meng, Xiangzhi; Wang, Zhixin et al. (2012) A unique bivalent binding and inhibition mechanism by the yatapoxvirus interleukin 18 binding protein. PLoS Pathog 8:e1002876
Liu, Caini; Swaidani, Shadi; Qian, Wen et al. (2011) A CC' loop decoy peptide blocks the interaction between Act1 and IL-17RA to attenuate IL-17- and IL-25-induced inflammation. Sci Signal 4:ra72
Li, Yongchao; Meng, Xiangzhi; Xiang, Yan et al. (2010) Structure function studies of vaccinia virus host range protein k1 reveal a novel functional surface for ankyrin repeat proteins. J Virol 84:3331-8