Interleukin-31 (IL-31) is a major protein involved in severe inflammatory skin disorders. Its signaling pathway is mediated through two type I cytokine receptors, IL-31RA (also known as the gp130-like receptor) and the oncostatin M receptor (OSMR). Understanding molecular details in these interactions would be helpful for developing antagonist anti-IL-31 monoclonal antibodies (mAbs) as potential therapies. Previous studies suggest that human IL-31 binds to IL-31RA and then recruits OSMR to form a ternary complex. In this model, OSMR cannot interact with IL-31 in the absence of IL-31RA. In this work, we show that feline IL-31 (fIL-31) binds independently with feline OSMR using surface plasmon resonance, an enzyme-linked immunosorbent assay, and yeast surface display. Moreover, competition experiments suggest that OSMR shares a partially overlapping epitope with IL-31RA. We then used deep mutational scanning to map the binding sites of both receptors on fIL-31. In agreement with previous studies of the human homologue, the binding site for IL31-RA contains fIL-31 positions E20 and K82, while the binding site for OSMR comprises the “PADNFERK” motif (P103–K110) and position G38. However, our results also revealed a new overlapping site, composed of positions R69, R72, P73, D76, D81, and E97, between both receptors that we called the “shared site”. The conformational epitope of an anti-feline IL-31 mAb that inhibits both OSMR and IL-31RA also mapped to this shared site. Combined, our results show that fIL-31 binds IL-31RA and OSMR independently through a partially shared epitope. These results suggest reexamination of the putative canonical mechanisms for IL-31 signaling in higher animals.

中文翻译：

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猫白介素31与Oncostatin M受体和IL-31RA共有重叠表位。

白介素31（IL-31）是一种与严重的炎症性皮肤病有关的主要蛋白质。它的信号传导途径是通过两种I型细胞因子受体介导的，即IL-31RA（也称为gp130样受体）和制瘤素M受体（OSMR）。了解这些相互作用中的分子细节将有助于开发拮抗性抗IL-31单克隆抗体（mAb）作为潜在疗法。先前的研究表明，人IL-31与IL-31RA结合，然后募集OSMR形成三元复合物。在此模型中，在没有IL-31RA的情况下OSMR无法与IL-31相互作用。在这项工作中，我们表明猫IL-31（fIL-31）使用表面等离子体共振，酶联免疫吸附测定和酵母表面展示与猫OSMR独立结合。此外，竞争实验表明OSMR与IL-31RA具有部分重叠的表位。然后，我们使用深度突变扫描来绘制fIL-31上两个受体的结合位点。与先前对人类同源物的研究一致，IL31-RA的结合位点包含fIL-31的E20和K82位置，而OSMR的结合位点包含“ PADNFERK”基序（P103-K110）和G38位置。然而，我们的结果还揭示了两个受体之间的新重叠位点，由位置R69，R72，P73，D76，D81和E97组成，我们称之为“共享位点”。同时抑制OSMR和IL-31RA的抗猫IL-31 mAb的构象表位也映射到该共享位点。结合起来，我们的结果表明，fIL-31通过部分共享的表位独立地结合IL-31RA和OSMR。