Interleukin-2 Carbohydrate Recognition Modulates CTLL-2 Cell Proliferation

Abstract

Interleukin-2 (IL-2) specifically recognizes high-mannose type glycans with five or six mannosyl residues. To determine whether the carbohydrate recognition activity of IL-2 contributes to its physiological activity, the inhibitory effects of high-mannose type glycans on IL-2-dependent CTLL-2 cell proliferation were investigated. Man5GlcNAc2Asn added to CTLL-2 cell cultures inhibited not only phosphorylation of tyrosine kinases but also IL-2-dependent cell proliferation. We found that a complex of IL-2, IL-2 receptor α, β, γ subunits, and tyrosine kinases was formed in rhIL-2-stimulated CTLL-2 cells. Among the components of this complex, only the IL-2 receptor α subunit was stained with Galanthus nivalis agglutinin which specifically recognizes high-mannose type glycans. This staining was diminished after digestion of the glycans with endo-β -N-acetylglucosaminidase H or D, suggesting that at least a N-glycan containing Man5GlcNAc2 is linked to the extracellular portion of the IL-2 receptor α subunit. Our findings indicate that IL-2 binds the IL-2 receptor α subunit through Man5GlcNAc2 and a specific peptide sequence on the surface of CTLL-2 cells. When IL-2 binds to the IL-2Rα subunit, this may trigger formation of the high affinity complex of IL-2-IL-2Rα, -β, and -γ subunits, leading to cellular signaling.