RESUMEN
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.
Asunto(s)
Proteínas Morfogenéticas Óseas/metabolismo , Proteína-5 Relacionada con Receptor de Lipoproteína de Baja Densidad/metabolismo , Proteína-6 Relacionada a Receptor de Lipoproteína de Baja Densidad/metabolismo , Proteína Wnt1/metabolismo , Proteínas Adaptadoras Transductoras de Señales , Secuencia de Aminoácidos , Proteínas Morfogenéticas Óseas/genética , Calorimetría , Línea Celular , Cristalografía , ADN Complementario , Marcadores Genéticos/genética , Humanos , Proteína-5 Relacionada con Receptor de Lipoproteína de Baja Densidad/genética , Proteína-6 Relacionada a Receptor de Lipoproteína de Baja Densidad/química , Proteína-6 Relacionada a Receptor de Lipoproteína de Baja Densidad/genética , Modelos Moleculares , Datos de Secuencia Molecular , Resonancia Magnética Nuclear Biomolecular , Unión Proteica , Conformación Proteica , Homología de Secuencia de Aminoácido , Proteína Wnt1/genéticaRESUMEN
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.
