The N-glycan on Asn54 affects the atypical N-glycan composition of plant-produced interleukin-22, but does not influence its activity

Human interleukin-22 (IL-22) is a member of the IL-10 cytokine family that has recently been shown to have major therapeutic potential. IL-22 is an unusual cytokine as it does not act directly on immune cells. Instead, IL-22 controls the differentiation, proliferation and antimicrobial protein expression of epithelial cells, thereby maintaining epithelial barrier function. In this study, we transiently expressed human IL-22 in Nicotiana benthamiana plants and investigated the role of N-glycosylation on protein folding and biological activity. Expression levels of IL-22 were up to 5.4 μg/mg TSP, and N-glycan analysis revealed the presence of the atypical Lewis A structure. Surprisingly, upon engineering of human-like N-glycans on IL-22 by co-expressing mouse FUT8 in ΔXT/FT plants a strong reduction in Lewis A was observed. Also, core α1,6-fucoylation did not improve the biological activity of IL-22. The combination of site-directed mutagenesis of Asn54 and in vivo deglycosylation with PNGase F also revealed that N-glycosylation at this position is not required for proper protein folding. However, we do show that the presence of a N-glycan on Asn54 contributes to the atypical N-glycan composition of plant-produced IL-22 and influences the N-glycan composition of N-glycans on other positions. Altogether, our data demonstrate that plants offer an excellent tool to investigate the role of N-glycosylation on folding and activity of recombinant glycoproteins, such as IL-22.