The First α Helix of Interleukin (Il)-2 Folds as a Homotetramer, Acts as an Agonist of the IL-2 Receptor β Chain, and Induces Lymphokine-Activated Killer Cells

Abstract

Interleukin (IL)-2 interacts with two types of functional receptors (IL-2Rαβγ and IL-2Rβγ) and acts on a broad range of target cells involved in inflammatory reactions and immune responses. For the first time, we show that a chemically synthesized fragment of the IL-2 sequence can fold into a molecule mimicking the quaternary structure of a hemopoietin. Indeed, peptide p1–30 (containing amino acids 1–30, covering the entire α helix A of IL-2) spontaneously folds into an α-helical homotetramer and stimulates the growth of T cell lines expressing human IL-2Rβ, whereas shorter versions of the peptide lack helical structure and are inactive. We also demonstrate that this neocytokine interacts with a previously undescribed dimeric form of IL-2Rβ. In agreement with its binding to IL-2Rβ, p1–30 activates Shc and p56lck but unlike IL-2, fails to activate Janus kinase (Jak)1, Jak3, and signal transducer and activator of transcription 5 (STAT5). Unexpectedly, we also show that p1–30 activates Tyk2, thus suggesting that IL-2Rβ may bind to different Jaks depending on its oligomerization. At the cellular level, p1–30 induces lymphokine-activated killer (LAK) cells and preferentially activates CD8low lymphocytes and natural killer cells, which constitutively express IL-2Rβ. A significant interferon γ production is also detected after p1–30 stimulation. A mutant form of p1–30 (Asp20→Lys), which is likely unable to induce vascular leak syndrome, remains capable of generating LAK cells, like the original p1–30 peptide. Altogether, our data suggest that p1–30 has therapeutic potential.

IL-2 In Vivo Activities and Antitumor Efficacy Enhanced by an Anti-IL-2 mAb

“…This region encompasses an amino acid residue (D34) within the ␣ helix A that is critical for the CD122 binding of IL-2 (10). In addition, the peptide encompassing ␣ helix A of human IL-2, termed p1-30, acts as an agonist through CD122 (11). These lines of evidence establish the neutralizing potential of the anti-IL-2 mAb.…”

IL-2Rβ Agonist P1–30 Acts in Synergy with IL-2, IL-4, IL-9, and IL-15: Biological and Molecular Effects

“…As previously demonstrated, p1-30 induces the proliferation of cell lines expressing the human IL-2R␤-chain (24). was observed between p1-30 and IL-2 because the proliferative response obtained with the combination of p1-30 ϩ IL-2 was much greater than the sum of each individual response.…”

“…In human PBMC, p1-30 induces lymphokine-activated killer (LAK) cells and leads to the production of IFN-␥. We have also suggested that p1-30 has therapeutic potential (24).…”

“…A peptide, named p1-30 (comprising aa 1-30 of human IL-2), which includes the entire ␣ helix A of human IL-2, has been recently characterized in our laboratory (24). At the structural level p1-30 appears to be folded as a cytokine of the hemopoietin family and binds to human IL-2R␤ dimers (p1-30R).…”

“…Contrary to IL-2, p1-30 is not able to activate Jak1, Jak3, or STAT5 but, strikingly, it induces the phosphorylation of Tyk2. Furthermore, p1-30 induces the activation of p56 lck and the phosphorylation of the adaptor protein Shc (24). At the immunological level p1-30 is able to specifically activate NK and CD8 T cells, which constitutively express large amounts of IL-2R␤.…”