529 J. Exp. Med.  The R ockefeller University Press • 0022-1007/ 2000/ 02/ 529/ 11 $5.00 Volume 191, Number 3, February 7, 2000 529–539 http:/ / www.jem.org The First  Helix of Interleukin (IL)-2 Folds as a Homotetramer, Acts as an Agonist of the IL-2 Receptor  Chain, and Induces Lymphokine-activated Killer Cells By R alph Eckenberg,* Thierry Rose, ‡ Jean-Louis Moreau,* R obert Weil, § Franck Gesbert, ¶ Sigrid Dubois,** Diana Tello,  Marc Bossus, ‡‡ Hélène Gras, ‡‡ André Tartar, ‡‡ Jacques Bertoglio, ¶ Salem Chouaïb, §§ Michel Goldberg, ‡ Yannick Jacques,** Pedro M. Alzari,  and Jacques Thèze* From the *Unité d’Immunogénétique Cellulaire, the ‡ Unité de Biochimie Cellulaire, the § Unité de Biologie Moléculaire Expression Génique, and the  Unité de Biochimie Structurale, Institut Pasteur, 75015 Paris, France; the ¶ Institut N ational de la Santé et de la R echerche Médicale (IN SER M), U461, 92296 Chatenay-Malabry, France; the ** IN SER M, U463, 44000 N antes, France; the ‡‡ Chimie des Biomolécules, Institut Pasteur, 59000 Lille, France; and the §§ IN SER M, U487, 94805 V illejuif, France Abstract Interleukin (IL)-2 interacts with two types of functional receptors (IL-2R  and IL-2R ) 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  helix A of IL-2) spontaneously folds into an -helical homotetramer and stimulates the growth of T cell lines expressing human IL-2R , whereas shorter versions of the peptide lack helical structure and are inactive. We also demon- strate that this neocytokine interacts with a previously undescribed dimeric form of IL-2R. In agreement with its binding to IL-2R , p1–30 activates Shc and p56 lck but unlike IL-2, fails to ac- tivate 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-2R  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-2R . A significant interferon  production is also detected after p1–30 stimulation. A mutant form of p1–30 (Asp20 →Lys), which is likely unable to induce vas- cular leak syndrome, remains capable of generating LAK cells, like the original p1–30 peptide. Al- together, our data suggest that p1–30 has therapeutic potential. Key words: interleukin 2 mimetic • synthetic hemopoietin • dimeric interleukin 2 receptor  chain • signal transduction • natural killer cells Introduction Human IL-2 is a 133–amino acid (aa) 1 polypeptide with a molecular mass of 15–18 kD depending on the degree of glycosylation (1, 2). Its structure is made up of a compact core bundle of four anti-parallel  helices connected by three loops (3). IL-2 is a major cytokine regulating the im- mune system, with its primary biological activity consisting in promoting clonal expansion of antigen-activated T lym- phocytes. Furthermore, IL-2 induces lymphokine-activated killer (LAK) and NK cell cytotoxicity against tumor cells or virus-infected cells (4). R. Eckenberg and T. Rose contributed equally to this work. Address correspondence to Jacques Thèze, Unité d’Immunogénétique Cellulaire, Département d’Immunologie, Institut Pasteur, 25 & 28 rue du Dr. R oux, 75724 Paris cedex 15, France. Phone: 33-1-45-68-86-28/ 86-00; Fax: 33-1-45-68-88-38; E-mail: jtheze@pasteur.fr 1 A bbreviations used in this paper: A domain, acidic domain; aa, amino acid; CD, circular dichroism; EMSA, electrophoretic mobility shift assay; EPO, erythropoietin; FLC, fluorescein; GAS, IFN-–activated sequence; Jak, Ja- nus kinase; K d , dissociation constant; LAK, lymphokine-activated killer cell; PTK, protein tyrosine kinase; S domain, serine-rich domain; STAT, signal transducer and activator of transcription; VLS, vascular leak syndrome. Downloaded from http://rupress.org/jem/article-pdf/191/3/529/1124892/99-1605.pdf by guest on 31 December 2022