O028 The signaling properties of Interleukin-30 underline plasticity and cross-talk among the Interleukin-6 family of cytokines
Introduction The anti-inflammatory Interleukin (IL)-6/IL-12 cytokine family member IL-27 consists of the cytokine Interleukin-30 (IL-30, also referred to as IL-27p28) and the non-signaling α -receptor subunit Epstein-Barr virus induced gene 3 (EBI3). Antigen-presenting cells are the major cellular source of both proteins, and IL-27 has been shown to engage signaling via a heterodimer of the two transmembrane receptors WSX-1 and gp130. Besides this well-established function, several studies suggest that IL-30 has signaling properties on its own. Recently, IL-30 was shown to form a novel cytokine complex with the non-signaling membrane-bound IL-6 receptor α (IL-6R). Methods Since free, endogenous IL-30 is not efficiently secreted, we developed a strategy for bacterial expression, purification and renaturation of murine IL-30 (mIL-30) for in vitro and in vivo analysis. Furthermore, we designed a Hyper-cytokine, consisting of the extracellular/soluble part of the IL-6R fused via a peptide linker to IL-30, and expressed the IL-30-sIL-6R fusion protein in mammalian cells. Results We show that mIL-30 can induce STAT-dependent proliferation of Ba/F3-gp130 cells expressing murine or human IL-6R, indicating that in contrast to murine IL-6, murine IL-30 possesses no species specificity. Furthermore, we identified the two transmembrane proteins that function as the signal transducing receptors of the IL-30/IL-6R complex. IL-30 was also able to induce IL-30-trans-signaling using the soluble IL-6R (sIL-6R), a characteristic property that was initially described for IL-6 signaling via the sIL-6R. We further show how STAT phosphorylation and proliferation of Ba/F3-gp130 cells induced by IL-30-sIL-6R can be efficiently inhibited. Finally, mIL-30 but not IL-6, was able to induce STAT-dependent proliferation of Ba/F3-gp130 cells without the need of the p28- α receptors IL-6R and EBI3, albeit at higher concentrations of mIL-30 in comparison to IL-30-sIL-6R. Conclusion Our study enlarges the spectrum of IL-30-dependent receptor activation pathways and might have major implications for the biological role of Interleukin-30 in vivo .