Abstract
Interleukin-23 (IL23) is a pro-inflammatory cytokine involved in the host defence against pathogens, but also implicated in the development of several autoimmune disorders. The IL23 receptor has become a key target for drug discovery but the exact mechanism of the receptor ligand interaction remains poorly understood. In this study the affinities of IL23 for its individual receptor components (IL23R and IL12Rβ1) and the heteromeric complex formed between them have been measured in living cells using NanoLuciferase tagged full-length proteins. Here, we demonstrate that TAMRA-tagged IL23 has a greater than seven fold higher affinity for IL12Rβ1 than IL23R. However, in the presence of both receptor subunits IL23 affinity is increased more than three orders of magnitude to 27 pM. Furthermore, we show that IL23 induces a potent change in the position of the N -terminal domains of the two receptor subunits consistent with a conformational change in the heteromeric receptor structure.
Highlights
Interleukin-23 (IL-23) is an important pro-inflammatory cytokine, produced by antigen-presenting cells, such as dendritic cells and macrophages, that plays a crucial role in host defense against bacterial and fungal pathogens (Verreck et al, 2004; Werner et al, 2011)
The specific receptor for the IL-23 cytokine is formed of the IL-12 receptor subunit b1 (IL12Rb1) and the IL-23 receptor (IL23R), which are both needed for subsequent Janus kinase (JAK) activation and signaling (Parham et al, 2002)
Following removal of the unreacted labeling reagent using a desalting column, the TAMRA-conjugated IL-23 and the unlabeled IL-23 were assessed using liquid chromatography coupled with mass spectrometry (LC-MS; Figures S1 and S2)
Summary
Interleukin-23 (IL-23) is an important pro-inflammatory cytokine, produced by antigen-presenting cells, such as dendritic cells and macrophages, that plays a crucial role in host defense against bacterial and fungal pathogens (Verreck et al, 2004; Werner et al, 2011). Each IL-12 heteromeric receptor component is thought to have affinity for a specific a or b subunit of each heterodimeric IL-12 family cytokine (Hasegawa et al, 2016). The specific receptor for the IL-23 cytokine is formed of the IL-12 receptor subunit b1 (IL12Rb1) and the IL-23 receptor (IL23R), which are both needed for subsequent Janus kinase (JAK) activation and signaling (Parham et al, 2002). The formation of heteromers by IL-12 family cytokine receptors facilitates promiscuous pairing within the IL-12 family, leading to a diverse range of functional effects (Floss et al, 2020; Hasegawa et al, 2016). IL-23 and IL-12 mediate distinct pathways, with IL-23 inducing the expansion and maintenance of Th17 cells and IL-12, leading to differentiation of Th1 cells (Vignali and Kuchroo, 2012)
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