title: The structure of siglec-7 in complex with sialosides: leads for rational structure-based inhibitor design.
abstract: Siglecs (sialic acid binding Ig-like lectins) are transmembrane receptors for sialylated glycoconjugates that modulate cellular interactions and signalling events in the haematopoietic, immune and nervous systems. Siglec-7 is a structural prototype for the recently described family of immune inhibitory CD33-related siglecs and is predominantly expressed on natural killer cells and monocytes, as well as subsets of CD8 T-cells. Siglec-specific inhibitors are desired for the detection of masked and unmasked forms of siglecs, to aid in dissection of signalling pathways and as tools to investigate siglecs as potential therapeutic targets. As a first step towards this end, we present the crystal structure of siglec-7 in complex with a sialylated ligand, the ganglioside analogue DSLc4 [alpha(2,3)/alpha(2,6) disialyl lactotetraosyl 2-(trimethylsilyl)ethyl], which allows for a detailed description of the binding site, required for structure-guided inhibitor design. Mutagenesis and binding assays were used to demonstrate a key structural role for Lys131, a residue that changes conformation upon sialic acid binding. Differences between the binding sites of siglec family members were then exploited using alpha-methyl Neu5Ac (N-acetylneuraminic acid) as a basic scaffold. A co-crystal of siglec-7 in complex with the sialoside inhibitor, oxamido-Neu5Ac [methyl alpha-9-(amino-oxalyl-amino)-9-deoxy-Neu5Ac] and inhibition data for the sialosides gives clear leads for future inhibitor design.
authors.affiliation: Division of Biological Chemistry, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK.
authors.forename: Helen
authors.initials: H
authors.lastname: Attrill
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Takazawa
authors.forename: Simone
authors.initials: S
authors.lastname: Witt
authors.forename: Soerge
authors.initials: S
authors.lastname: Kelm
authors.forename: Rainer
authors.initials: R
authors.lastname: Isecke
authors.forename: Reinhard
authors.initials: R
authors.lastname: Brossmer
authors.forename: Takayuki
authors.initials: T
authors.lastname: Ando
authors.forename: Hideharu
authors.initials: H
authors.lastname: Ishida
authors.forename: Makoto
authors.initials: M
authors.lastname: Kiso
authors.forename: Paul R
authors.initials: PR
authors.lastname: Crocker
authors.forename: Daan M F
authors.initials: DM
authors.lastname: van Aalten
mesh_terms: D000818:Animals; D015214:Antigens, Differentiation, Myelomonocytic / Q000737:chemistry* / Q000502:physiology*; D016466:CHO Cells; D019556:COS Cells; D002522:Chlorocebus aethiops; D006224:Cricetinae; D018360:Crystallography, X-Ray; D015195:Drug Design; D004912:Erythrocytes / Q000378:metabolism; D006801:Humans; D037102:Lectins / Q000737:chemistry* / Q000502:physiology*; D007962:Leukocytes / Q000378:metabolism; D008968:Molecular Conformation; D019158:N-Acetylneuraminic Acid / Q000737:chemistry; D012794:Sialic Acids / Q000737:chemistry
chemical_list: D015214:Antigens, Differentiation, Myelomonocytic; D037102:Lectins; C402206:SIGLEC7 protein, human; D012794:Sialic Acids; D019158:N-Acetylneuraminic Acid