title: Elucidation of the interleukin-15 binding site on its alpha receptor by NMR.
abstract: The cytokine interleukin-15 (IL-15) signals through the formation of a quaternary receptor complex composed of an IL-15-specific alpha receptor, together with beta and gammac receptors that are shared with interleukin-2 (IL-2). The initiating step in the formation of this signaling complex is the interaction between IL-15 and IL-15Ralpha, which is a single sushi domain bearing strong structural homology to one of the two sushi domains of IL-2Ralpha. The crystal structure of the IL2-Ralpha/IL-2 complex has been determined, however little is known about the analogous IL-15Ralpha/IL-15 binding interaction. Here we show that recombinant IL-15 can be overexpressed as a stable complex in the presence of its high affinity receptor, IL-15Ralpha. We find that this complex is 10-fold more active than IL-15 alone in stimulating proliferation and survival of memory phenotype CD8 T cells. To probe the ligand/receptor interface, we used solution NMR to map chemical shifts on 15N-labeled IL-15Ralpha in complex with unlabeled IL-15. Our results predict that the binding surface on IL-15Ralpha involves strands C and D, similar to IL-2Ralpha. The interface, as predicted here, leaves open the possibility of trans-presentation of IL-15 by IL-15Ralpha on an opposing cell.
authors.affiliation: Howard Hughes Medical Institute, Department of Molecular and Cellular Physiology, Stanford University School of Medicine, California 94305, USA.
authors.forename: Nicole A
authors.initials: NA
authors.lastname: Hanick
authors.forename: Mathias
authors.initials: M
authors.lastname: Rickert
authors.forename: Luca
authors.initials: L
authors.lastname: Varani
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Bankovich
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Cochran
authors.forename: David M
authors.initials: DM
authors.lastname: Kim
authors.forename: Charles D
authors.initials: CD
authors.lastname: Surh
authors.forename: K Christopher
authors.initials: KC
authors.lastname: Garcia
mesh_terms: D001665:Binding Sites; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D006801:Humans; D019409:Interleukin-15 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D053720:Interleukin-15 Receptor alpha Subunit / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D019409:Interleukin-15; D053720:Interleukin-15 Receptor alpha Subunit; D011994:Recombinant Proteins