ABSTRACT
LRP5 and LRP6 are proteins predicted to contain four six-bladed ß-propeller domains and both bind the bone-specific Wnt signaling antagonist sclerostin. Here, we report the crystal structure of the amino-terminal region of LRP6 and using NMR show that the ability of sclerostin to bind to this molecule is mediated by the central core of sclerostin and does not involve the amino- and carboxyl-terminal flexible arm regions. We show that this structured core region interacts with LRP5 and LRP6 via an NXI motif (found in the sequence PNAIG) within a flexible loop region (loop 2) within the central core region. This sequence is related closely to a previously identified motif in laminin that mediates its interaction with the ß-propeller domain of nidogen. However, the NXI motif is not involved in the interaction of sclerostin with LRP4 (another ß-propeller containing protein in the LRP family). A peptide derived from the loop 2 region of sclerostin blocked the interaction of sclerostin with LRP5/6 and also inhibited Wnt1 but not Wnt3A or Wnt9B signaling. This suggests that these Wnts interact with LRP6 in different ways.
Subject(s)
Bone Morphogenetic Proteins/metabolism , Low Density Lipoprotein Receptor-Related Protein-5/metabolism , Low Density Lipoprotein Receptor-Related Protein-6/metabolism , Wnt1 Protein/metabolism , Adaptor Proteins, Signal Transducing , Amino Acid Sequence , Bone Morphogenetic Proteins/genetics , Calorimetry , Cell Line , Crystallography , DNA, Complementary , Genetic Markers/genetics , Humans , Low Density Lipoprotein Receptor-Related Protein-5/genetics , Low Density Lipoprotein Receptor-Related Protein-6/chemistry , Low Density Lipoprotein Receptor-Related Protein-6/genetics , Models, Molecular , Molecular Sequence Data , Nuclear Magnetic Resonance, Biomolecular , Protein Binding , Protein Conformation , Sequence Homology, Amino Acid , Wnt1 Protein/geneticsABSTRACT
A series of quinoxaline inhibitors of c-Met kinase is described. The postulated binding mode was confirmed by an X-ray crystal structure and optimisation of the series was performed on the basis of this structure. Future directions for development of the series are discussed together with the identification of a novel quinoline scaffold.
