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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

2000; Rockefeller University Press; Volume: 191; Issue: 3 Linguagem: Inglês

10.1084/jem.191.3.529

1540-9538

Ralph Eckenberg, Thierry Rose, Jean‐Louis Moreau, Robert Weil, Franck Gesbert, Sigrid Dubois, Diana Tello, Marc Bossus, Hélène Gras, André Tartar, Jacques Bertoglio, Salem Chouaı̈b, Michel Goldberg, Yannick Jacques, Pedro M. Alzari, Jacques Thèze,

Immune Response and Inflammation

Interleukin (IL)-2 interacts with two types of functional receptors (IL-2Ralphabetagamma and IL-2Rbetagamma) 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 alpha helix A of IL-2) spontaneously folds into an alpha-helical homotetramer and stimulates the growth of T cell lines expressing human IL-2Rbeta, 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-2Rbeta. In agreement with its binding to IL-2Rbeta, p1-30 activates Shc and p56(lck) 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-2Rbeta may bind to different Jaks depending on its oligomerization. At the cellular level, p1-30 induces lymphokine-activated killer (LAK) cells and preferentially activates CD8(low) lymphocytes and natural killer cells, which constitutively express IL-2Rbeta. A significant interferon gamma 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.