IL-6/IL-12 Cytokine Receptor Shuffling of Extra-and Intracellular Domains Reveals Canonical STAT Activation via Synthetic IL-35 and IL-39 Signaling

IL-35 and IL-39 are recently discovered shared members of the IL-6-and IL-12-type cytokine family with immune-suppressive capacity. IL-35 has been reported to induce the formation of four different receptor complexes: gp130: IL-12 beta 2, gp130: gp130, IL-12 beta 2: IL-12 beta 2, and IL-12 beta 2: WSX-1. IL-39 was proposed to form a gp130: IL-23R receptor complex. IL-35, but not IL-39, has been reported to activate non-conventional STAT signaling, depending on the receptor complex and target cell. Analyses of IL-35 and IL-39 are, however, hampered by the lack of biologically active recombinant IL-35 and IL-39 proteins. Therefore, we engineered chimeric cytokine receptors to accomplish synthetic IL-35 and IL-39 signaling by shuffling the extra-and intracellular domains of IL-6/IL-12-type cytokine receptors, resulting in biological activity for all previously described IL-35 receptor complexes. Moreover, we found that the proposed IL-39 receptor complex is biologically active and discovered two additional biologically active synthetic receptor combinations, gp130/IL-12R beta 1 and IL-23R/IL-12R beta 2. Surprisingly, synthetic IL-35 activation led to more canonical STAT signaling of all receptor complexes. In summary, our receptor shuffling approach highlights an interchangeable, modular domain structure among IL-6-and IL-12-type cytokine receptors and enabled synthetic IL-35 and IL-39 signaling.