The Three‐Dimensional Structure of Human Interleukin‐5 at 2.4‐Angstroms Resolution: Implication for the Structures of Other Cytokines

Abstract

THE THREE-DIMENSIONAL STRUCTURE OF HUMAN INTERLEUKIN-5Interleukin 5 (IL-5) is a specific cytokine involved in the development and differentiation of eosinophils. It plays an important role in diseases associated with increased levels of eosinophils, such as asthma and atopic dermatitis.',? W: have solved the three-dimensional structure of human 1L-5 to a resolution of 2.4 A using X-ray crystallographic techniques. The molecule is a dimer of identical subunits that are joined together by disulphide bridges. The crystal structure reveals a novel two-domain structure where each domain of the protein is a 4-helical bundle containing two short stretches of beta sheet. These domain structures show a high degree of similarity to the cytokine fold, which has already been described in Interleukin-2 and -4, granulocyte, and granulocyte-macrophage colony stimulating factors, and porcine and human growth hormones. This high degree of similarity within known cytokine structures has led us to make predictions of the structures of cytokines for which no three-dimensional information is available. Furthermore, it provides the molecular basis for the design of agonists and antagonists of IL-5, which will be important in the therapy of eosinophil mediated diseases.1L-5 is a T-cell-derived cytokine that causes eosinophilpoesis and activation of eosinophils. In order to investigate its biology and its role in models of asthmatic inflammation, we have produced the protein in large quantities. A synthetic gene for human IL-5 was overexpressed in E. coli, where the protein forms inclusion bodies. This protein can then be subsequently renatured under carefully controlled conditions of protein concentration and buffer redox potential to give large quantities of active p r~t e i n .~ Unlike the natural human IL-5, the E. coli derived material is not glycosylated. It is of equal potency, however, showing that glycosylation is not required for biological activity. We mapped the positions of the disulphide 118

The GM–CSF/IL‐3/IL‐5 cytokine receptor family: from ligand recognition to initiation of signaling

“…Furthermore, extensive mutagenesis analyses on IL‐5 and its receptor has allowed a picture to be built of how IL‐5 recognizes both of its receptor subunits. Human IL‐5 is a 115 residue glycoprotein that adopts an unusual homodimer structure ( Fig. A ).…”

Profile of anti-IL-5 mAb mepolizumab in the treatment of severe refractory asthma and hypereosinophilic diseases

“… 16 IL-5 is a 134-amino acid protein that forms a 52 kDa homodimer related to both GM-CSF and IL-3. 17 – 19 IL-5 is produced by CD4+ Th2 cells, mast cells, eosinophils, and basophils and is involved in several steps of eosinophil development and function. 20 It stimulates the final differentiation of activated B cells into antibody-forming cells and enhances the proliferation and differentiation of eosinophils precursors.…”

New biological therapies from the human genome

“…Most of the interleukins and growth factors are built from a bundle of four α-helices. Thus, a BLAST search with the simple sequence of the protein has a low chance of finding other members of the same structural class: IL-2 will not find IL-3 and IL-4 will not find IL-5, despite them all being four-helix bundles [10] . Thus, more sensitive approaches have used multiple sequence alignment approaches, where profiles are built up of the average of the members of a family and these are used to search (programs such as position specific iterated BLAST).…”