title: Sclerostin binds to LRP5/6 and antagonizes canonical Wnt signaling.
abstract: The loss of the SOST gene product sclerostin leads to sclerosteosis characterized by high bone mass. In this report, we found that sclerostin could antagonize canonical Wnt signaling in human embryonic kidney A293T cells and mouse osteoblastic MC3T3 cells. This sclerostin-mediated antagonism could be reversed by overexpression of Wnt co-receptor low density lipoprotein receptor-related protein (LRP) 5. In addition, we found that sclerostin bound to LRP5 as well as LRP6 and identified the first two YWTD-EGF repeat domains of LRP5 as being responsible for the binding. Although these two repeat domains are required for transduction of canonical Wnt signals, canonical Wnt did not appear to compete with sclerostin for binding to LRP5. Examination of the expression of sclerostin and Wnt7b, an autocrine canonical Wnt, during primary calvarial osteoblast differentiation revealed that sclerostin is expressed at late stages of osteoblast differentiation coinciding with the expression of osteogenic marker osteocalcin and trailing after the expression of Wnt7b. Given the plethora of evidence indicating that canonical Wnt signaling stimulates osteogenesis, we believe that the high bone mass phenotype associated with the loss of sclerostin may be attributed, at least in part, to an increase in canonical Wnt signaling resulting from the reduction in sclerostin-mediated Wnt antagonism.
authors.affiliation: Department of Genetics and Developmental Biology, University of Connecticut Health Center, Farmington, 06030, USA.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Li
authors.forename: Yazhou
authors.initials: Y
authors.lastname: Zhang
authors.forename: Heeseog
authors.initials: H
authors.lastname: Kang
authors.forename: Wenzhong
authors.initials: W
authors.lastname: Liu
authors.forename: Peng
authors.initials: P
authors.lastname: Liu
authors.forename: Jianghong
authors.initials: J
authors.lastname: Zhang
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Harris
authors.forename: Dianqing
authors.initials: D
authors.lastname: Wu
mesh_terms: D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing; D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D005819:Genetic Markers / Q000235:genetics; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D026502:LDL-Receptor Related Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D060492:Low Density Lipoprotein Receptor-Related Protein-5; D060488:Low Density Lipoprotein Receptor-Related Protein-6; D051379:Mice; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D011973:Receptors, LDL / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D051153:Wnt Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D019485:Bone Morphogenetic Proteins; C501126:DKK1 protein, human; C498622:DKK2 protein, human; C501127:Dkk1 protein, mouse; C405060:Dkk2 protein, mouse; D005819:Genetic Markers; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D026502:LDL-Receptor Related Proteins; C555482:LRP5 protein, human; C555475:LRP6 protein, human; D060492:Low Density Lipoprotein Receptor-Related Protein-5; D060488:Low Density Lipoprotein Receptor-Related Protein-6; C555483:Lrp5 protein, mouse; C555476:Lrp6 protein, mouse; D011506:Proteins; D011518:Proto-Oncogene Proteins; D011973:Receptors, LDL; D011994:Recombinant Proteins; C486030:Sost protein, mouse; D051153:Wnt Proteins; C095937:Wnt7b protein, mouse