Feline Interleukin-31 Shares Overlapping Epitopes with the Oncostatin M Receptor and IL-31RA

Abstract

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.

Expression, purification, and biological characterization of recombinant human interleukin‐31 protein

“…32,33 Different from human orthologues, feline IL-31 (fIL-31) could directly bind to either feline OSMRβ or IL-31RA. 34 In current study, rhIL-31 could directly bind to hIL-31RA in a dose-dependent manner, which was proved by both ELISA and FACS assays (Figures 3 and 4A,B). Obviously, the results were in alignment with the immunoprecipitation observations in previous literatures.…”

“…Previous studies provided immunoprecipitation evidence that hIL‐31 was able to directly interact with rhIL‐31RA‐hFc, but failed to recognize hOSMRβ‐hFc 32,33 . Different from human orthologues, feline IL‐31 (fIL‐31) could directly bind to either feline OSMRβ or IL‐31RA 34 . In current study, rhIL‐31 could directly bind to hIL‐31RA in a dose‐dependent manner, which was proved by both ELISA and FACS assays (Figures 3 and 4A,B).…”

Atopic Dermatitis in Domestic Animals: What Our Current Understanding Is and How This Applies to Clinical Practice

“…A monoclonal antibody against feline IL-31 with the ability to block the binding of this cytokine to its receptor has been described [ 119 ], suggesting a promising future biologic for cats.…”