title: Identification of regions within the third FnIII-like domain of the IL-5Ralpha involved in IL-5 interaction.
abstract: Previously, two binding sites for interleukin 5 (IL-5) were identified on the IL-5 receptor alpha chain (IL-5Ralpha). They are located within the CD loop of the first fibronectin type III (FnIII)-like domain and the EF loop of the second FnIII-like domain. The first binding site was identified by exploiting the different abilities of human IL-5Ralpha (hIL-5Ralpha) and mouse IL-5Ralpha (mIL-5Ralpha) to bind hIL-5. Here we show that ovine IL-5 (oIL-5) has the ability to activate the hIL-5Ralpha but not the mIL-5Ralpha. By using chimeras of the mIL-5Ralpha and hIL-5Ralpha we demonstrate that residues within the first and third FnIII-like domains of mIL-5Ralpha are responsible for this lack of activity. Furthermore, mutation of residues on hIL-5Ralpha to mIL-5Ralpha within the predicted DE and FG loop regions of the third FnIII domain reduces oIL-5 activity. These results show that regions of the third FnIII domain of IL-5Ralpha are involved in binding, in addition to the regions in domains one and two of the IL-5Ralpha that were identified in an earlier study.
authors.affiliation: Molecular Immunology Group, Curtin University of Technology, Perth, Australia. pczabot@nimr.mrc.ac.uk
authors.forename: P E
authors.initials: PE
authors.lastname: Czabotar
authors.forename: J
authors.initials: J
authors.lastname: Holland
authors.forename: C J
authors.initials: CJ
authors.lastname: Sanderson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001681:Biological Assay; D019556:COS Cells; D002460:Cell Line; D005353:Fibronectins / Q000378:metabolism*; D006801:Humans; D015848:Interleukin-5 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D018123:Receptors, Interleukin / Q000235:genetics / Q000378:metabolism*; D053649:Receptors, Interleukin-5
chemical_list: D005353:Fibronectins; D015848:Interleukin-5; D018123:Receptors, Interleukin; D053649:Receptors, Interleukin-5