• The Molecular Basis of IL-1 Family Signaling: Strategies to Modulate Inflammation

      Fields, James; Sundberg, Eric J.; 0000-0001-5923-108X (2021)
      Interleukin-1 (IL-1) family cytokines are potent signaling molecules that influence both innate and adaptive immune systems. The IL-1 family, composed of 11 cytokines and 10 receptors, mediate inflammation to a wide array of stimuli and act on myriad cell types for diverse immunological outcomes. Altogether, IL-1 family signaling is integral to a multitude of inflammatory responses and occurs in distinct steps. First, an agonist cytokine binds its cognate receptor at high affinity. Next, this cytokine-receptor complex recruits an often-shared co-receptor. As this cytokine/receptor/co-receptor complex forms, Toll/IL-1 Receptor (TIR) domains, residing cytoplasmically, oligomerize, initiating a potent signaling cascade that results in prototypical NF-κB signal transduction. Due to the strong nature of IL-1 family signaling, multiple physiological mechanisms exist to stem this inflammatory signal, including antagonist cytokines and decoy receptors. Within the IL-1 family, the cytokines and receptors can be further divided into four subfamilies dependent on their secondary receptors. The IL-1 subfamily contains IL-1, IL-33, and IL-36 as they all share IL-1RAcP as their secondary receptor; the IL-18 subfamily is distinct as it utilizes IL-18Rβ as its secondary receptor. Here, we describe how structural biology has guided our understanding of IL-1 family signaling and how that knowledge can be leveraged for the design of therapeutics to stem aberrant cytokine signaling. In our first study, we demonstrate the feasibility of targeting a shared co-receptor, IL-1RAcP, for selective cytokine inhibition. Indeed, dependent on the specific epitope targeted on IL-1RAcP, differential cytokine signaling inhibition can be achieved. In addition, we developed our own IL-33 therapeutics by leveraging the high affinity IL-33 has for its primary receptor, the stability imparted by the secondary receptor, and the extended half-life gained through an Fc-fused receptor. Two of these molecules inhibit IL-33 signaling better than the natural antagonist sST2. Altogether, structural biology has informed our understanding of IL-1 family signaling, generated approaches to improve existing therapeutics, namely antibody epitope targeting, and led to the creation of additional IL-33 target therapeutics in the form of our “cytokine traps.”
    • Repression of TNFalpha gene activation at febrile range temperature through modification of recruitment of transcriptional regulators

      Cooper, Zachary A.; Hasday, Jeffrey D. (2009)
      We have previously shown that exposure to febrile-range temperatures (FRT, 39.5-40°C) reduces lipopolysaccaride (LPS)-induced tumor necrosis factor-α (TNFα) expression, in part through the direct interaction of heat shock factor-1 (HSF-1) with the TNFα gene promoter. However, it is not known whether exposure to FRT also modifies other proximal LPS-induced signaling events or recruitment of transcriptional regulators to the TNFα promoter. Using HSF-1-null mice, we confirmed that HSF-1 is required for FRT-induced repression of TNFα in vitro by LPS-stimulated bone marrow derived macrophages and in vivo in mice challenged intratracheally with LPS. Exposing LPS-stimulated RAW 264.7 mouse macrophages to FRT reduced TNFα expression, while increasing interleukin (IL)-1β expression despite the two genes being regulated by the same MyD88-dependent pathway. Global activation of the three LPS induced signaling intermediates that lead to cytokine gene expression, ERK and p38 MAPKs and NFκB, was not affected by exposing RAW 264.7 cells to FRT as assessed by western blot analysis of ERK and p38 phosphorylation and analysis of NFκB activation by EMSA and reporter plasmid expression assays. However, chromatin immunoprecipitation (ChIP) analysis demonstrated that exposure to FRT reduced LPS-induced recruitment of NFκB-p65 to the TNFα promoter, while increasing its recruitment to the IL-1β promoter. An additional ChIP analysis shows that LPS stimulated a 90% increase in recruitment of Sp1 to the proximal TNFα promoter at 37�C, which was completely abrogated by exposure to FRT even though FRT exposure increased intranuclear Sp1 DNA-binding as measured by EMSA. LPS also stimulated recruitment of both Elk-1 and ATF-2 to the proximal promoter, but FRT exposure had no significant effect on this process. ChIP analysis of the 1452 bp TNFα 5'flanking sequence (-1300/+152) revealed no additional heat shock response elements (HSEs) and no effect of FRT on chromatin acetylation on this sequence. These data suggest that FRT exerts its effects on cytokine gene expression in a gene specific manner through downstream effects on promoter activation, rather than through proximal receptor activation/signaling events. In conclusion, we describe new mechanisms through which TNFα expression is reduced at FRT through gene-specific reduction of NFκB and Sp1 recruitment to the TNFα promoter.