title: Dual mechanism of interleukin-3 receptor blockade by an anti-cancer antibody.
abstract: Interleukin-3 (IL-3) is an activated T cell product that bridges innate and adaptive immunity and contributes to several immunopathologies. Here, we report the crystal structure of the IL-3 receptor α chain (IL3Rα) in complex with the anti-leukemia antibody CSL362 that reveals the N-terminal domain (NTD), a domain also present in the granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-5, and IL-13 receptors, adopting unique "open" and classical "closed" conformations. Although extensive mutational analyses of the NTD epitope of CSL362 show minor overlap with the IL-3 binding site, CSL362 only inhibits IL-3 binding to the closed conformation, indicating alternative mechanisms for blocking IL-3 signaling. Significantly, whereas "open-like" IL3Rα mutants can simultaneously bind IL-3 and CSL362, CSL362 still prevents the assembly of a higher-order IL-3 receptor-signaling complex. The discovery of open forms of cytokine receptors provides the framework for development of potent antibodies that can achieve a "double hit" cytokine receptor blockade.
authors.affiliation: Australian Cancer Research Foundation Rational Drug Discovery Centre, St. Vincent's Institute of Medical Research, Fitzroy, VIC 3065, Australia.
authors.forename: Sophie E
authors.initials: SE
authors.lastname: Broughton
authors.affiliation: The Centre for Cancer Biology, SA Pathology and the University of South Australia, Adelaide, SA 5000, Australia.
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Hercus
authors.affiliation: CSL Limited, Parkville, VIC 3010, Australia.
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Hardy
authors.affiliation: The Centre for Cancer Biology, SA Pathology and the University of South Australia, Adelaide, SA 5000, Australia.
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: McClure
authors.affiliation: Australian Cancer Research Foundation Rational Drug Discovery Centre, St. Vincent's Institute of Medical Research, Fitzroy, VIC 3065, Australia.
authors.forename: Tracy L
authors.initials: TL
authors.lastname: Nero
authors.affiliation: The Centre for Cancer Biology, SA Pathology and the University of South Australia, Adelaide, SA 5000, Australia.
authors.forename: Mara
authors.initials: M
authors.lastname: Dottore
authors.affiliation: CSL Limited, Parkville, VIC 3010, Australia.
authors.forename: Huy
authors.initials: H
authors.lastname: Huynh
authors.affiliation: CSL Limited, Parkville, VIC 3010, Australia.
authors.forename: Hal
authors.initials: H
authors.lastname: Braley
authors.affiliation: The Centre for Cancer Biology, SA Pathology and the University of South Australia, Adelaide, SA 5000, Australia.
authors.forename: Emma F
authors.initials: EF
authors.lastname: Barry
authors.affiliation: The Centre for Cancer Biology, SA Pathology and the University of South Australia, Adelaide, SA 5000, Australia.
authors.forename: Winnie L
authors.initials: WL
authors.lastname: Kan
authors.affiliation: Australian Cancer Research Foundation Rational Drug Discovery Centre, St. Vincent's Institute of Medical Research, Fitzroy, VIC 3065, Australia.
authors.forename: Urmi
authors.initials: U
authors.lastname: Dhagat
authors.affiliation: CSL Limited, Parkville, VIC 3010, Australia.
authors.forename: Pierre
authors.initials: P
authors.lastname: Scotney
authors.affiliation: CSL Limited, Parkville, VIC 3010, Australia.
authors.forename: Dallas
authors.initials: D
authors.lastname: Hartman
authors.affiliation: CSL Limited, Parkville, VIC 3010, Australia.
authors.forename: Samantha J
authors.initials: SJ
authors.lastname: Busfield
authors.affiliation: CSL Limited, Parkville, VIC 3010, Australia.
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Owczarek
authors.affiliation: CSL Limited, Parkville, VIC 3010, Australia.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Nash
authors.affiliation: CSL Limited, Parkville, VIC 3010, Australia. Electronic address: nick.wilson@csl.com.au.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Wilson
authors.affiliation: Australian Cancer Research Foundation Rational Drug Discovery Centre, St. Vincent's Institute of Medical Research, Fitzroy, VIC 3065, Australia; Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, VIC 3010, Australia. Electronic address: mparker@svi.edu.au.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Parker
authors.affiliation: The Centre for Cancer Biology, SA Pathology and the University of South Australia, Adelaide, SA 5000, Australia. Electronic address: angel.lopez@health.sa.gov.au.
authors.forename: Angel F
authors.initials: AF
authors.lastname: Lopez
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D061067:Antibodies, Monoclonal, Humanized / Q000737:chemistry* / Q000276:immunology; D000970:Antineoplastic Agents / Q000737:chemistry* / Q000378:metabolism; D001666:Binding Sites, Antibody; D019556:COS Cells; D002522:Chlorocebus aethiops; D057809:HEK293 Cells; D006801:Humans; D053650:Interleukin-3 Receptor alpha Subunit / Q000737:chemistry* / Q000276:immunology; D008969:Molecular Sequence Data; D011485:Protein Binding
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; C115022:IL3RA protein, human; D053650:Interleukin-3 Receptor alpha Subunit