Sclerostin and the inhibition of Wnt signaling and bone formation

Abstract

The loss of the SOST gene product sclerostin leads to sclerosteosis characterized by high bone mass (HBM). In this report, we found that sclerostin could antagonize canonical Wnt signaling in human embryonic kidney A293 cells and mouse osteoblastic MC3T3 cells. This sclerostin-mediated antagonism could be reversed by over-expression of Wnt coreceptor LRP5. 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 transducing 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 the 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 HBM phenotype associated with the loss of sclerostin may at least in part be attributed to an increase in canonical Wnt signaling resulting from the reduction in sclerostin-mediated Wnt antagonism.

1 . A method for promoting bone formation or bone remodeling in a patient in need thereof comprising administering at least one non-native compound, at least one fragment of a non-native compound, or any combination thereof, wherein said compound or fragment binds to the site on sclerostin where sclerostin interacts with the LRP receptor to disrupt the interaction of said sclerostin with said receptor. 
   
   
       2 . A method for promoting bone formation or bone remodeling in a patient in need thereof comprising administering at least one non-native compound, at least one fragment of a non-native compound, or any combination thereof, wherein said compound or fragment binds to the site on sclerostin where sclerostin interacts with at least one domain of the LRP receptor to disrupt the interaction of said sclerostin with said receptor. 
   
   
       3 . A method for promoting bone formation or bone remodeling in a patient in need thereof comprising administering at least one non-native compound, at least one fragment of a non-native compound, or any combination thereof, wherein said compound or fragment binds to the site on sclerostin where sclerostin interacts with the first and second domain of the LRP receptor to disrupt the interaction of said sclerostin with said receptor. 
   
   
       4 . A method for promoting bone formation or bone remodeling in a patient in need thereof comprising administering at least one non-native compound, at least one fragment of a non-native compound, or any combination thereof, wherein said compound or fragment binds to at least one site on sclerostin where sclerostin interacts with the LRP receptor to disrupt the interaction of said sclerostin with said receptor. 
   
   
       5 . A method for promoting bone formation or bone remodeling in a patient in need thereof comprising administering at least one non-native compound, at least one fragment of a non-native compound, or any combination thereof, wherein said compound or fragment binds to at least one site on sclerostin where sclerostin interacts with at least one domain of the LRP receptor to disrupt the interaction of said sclerostin with said receptor. 
   
   
       6 . A method for promoting bone formation or bone remodeling in a patient in need thereof comprising administering at least one non-native compound, at least one fragment of a non-native compound, or any combination thereof, wherein said compound or fragment binds to at least one site on sclerostin where sclerostin interacts with the first and second domain of the LRP receptor to disrupt the interaction of said sclerostin with said receptor. 
   
   
       7 . A method for promoting bone formation or bone remodeling in a patient in need thereof comprising administering at least one non-native compound, at least one fragment of a non-native compound, or any combination thereof, wherein said compound or fragment binds:
 a. to at least one site on sclerostin where sclerostin interacts with the LRP receptor; and   b. to the LRP receptor,   
     thereby disrupting the interaction of sclerostin with said receptor. 
   
   
       8 . A method for promoting bone formation or bone remodeling in a patient in need thereof comprising administering at least one non-native compound, at least one fragment of a non-native compound, or any combination thereof, wherein said compound or fragment binds:
 a. to at least one site on sclerostin where sclerostin interacts with the LRP receptor; and   b. to at least one domain on the LRP receptor,   
     thereby disrupting the interaction of sclerostin with said receptor. 
   
   
       9 . A method for promoting bone formation or bone remodeling in a patient in need thereof comprising administering at least one non-native compound, at least one fragment of a non-native compound, or any combination thereof, wherein said compound or fragment binds:
 a. to at least one site on sclerostin where sclerostin interacts with the LRP receptor; and   b. to the first and second domain on the LRP receptor,   
     thereby disrupting the interaction of sclerostin with said receptor. 
   
   
       10 . The method of  claim 1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8 ,  9  or  10  wherein said compound or said fragment of a compound comprises a small molecule, protein, peptide, polypeptide, cyclic molecule, heterocyclic organic molecule, nucleic acid, lipid, charged lipid, polar lipid, non-polar lipid, sugar, glycoprotein, glycolipid, lipoprotein or chemical. 
   
   
       11 . The method of  claim 1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8 ,  9  or  10  wherein said compound or said fragment of a compound is an antibody or a fragment of an antibody. 
   
   
       12 . A therapeutic composition for promoting bone formation or bone remodeling comprising at least one non-native compound, at least one fragment of a non-native compound, or any combination thereof, wherein said compound or fragment binds to the site on sclerostin where sclerostin interacts with the LRP receptor to disrupt the interaction of said sclerostin with said receptor. 
   
   
       13 . A therapeutic composition for promoting bone formation or bone remodeling comprising at least one non-native compound, at least one fragment of a non-native compound, or any combination thereof, wherein said compound or fragment binds to the site on sclerostin where sclerostin interacts with at least one domain of the LRP receptor to disrupt the interaction of said sclerostin with said receptor. 
   
   
       14 . A therapeutic composition for promoting bone formation or bone remodeling comprising at least one non-native compound, at least one fragment of a non-native compound, or any combination thereof, wherein said compound or fragment binds to the site on sclerostin where sclerostin interacts with the first and second domain of the LRP receptor to disrupt the interaction of said sclerostin with said receptor. 
   
   
       15 . A therapeutic composition for promoting bone formation or bone remodeling comprising at least one non-native compound, at least one fragment of a non-native compound, or any combination thereof, wherein said compound or fragment binds to at least one site on sclerostin where sclerostin interacts with the LRP receptor to disrupt the interaction of said sclerostin with said receptor. 
   
   
       16 . A therapeutic composition for promoting bone formation or bone remodeling comprising at least one non-native compound, at least one fragment of a non-native compound, or any combination thereof, wherein said compound or fragment binds to at least one site on sclerostin where sclerostin interacts with at least one domain of the LRP receptor to disrupt the interaction of said sclerostin with said receptor. 
   
   
       17 . A therapeutic composition for promoting bone formation or bone remodeling comprising at least one non-native compound, at least one fragment of a non-native compound, or any combination thereof, wherein said compound or fragment binds to at least one site on sclerostin where sclerostin interacts with the first and second domain of the LRP receptor to disrupt the interaction of said sclerostin with said receptor. 
   
   
       18 . A therapeutic composition for promoting bone formation or bone remodeling comprising at least one non-native compound, at least one fragment of a non-native compound, or any combination thereof, wherein said compound or fragment binds:
 a. to at least one site on sclerostin where sclerostin interacts with the LRP receptor; and   b. to the LRP receptor,   
     thereby disrupting the interaction of sclerostin with said receptor. 
   
   
       19 . A therapeutic composition for promoting bone formation or bone remodeling comprising at least one non-native compound, at least one fragment of a non-native compound, or any combination thereof, wherein said compound or fragment binds:
 a. to at least one site on sclerostin where sclerostin interacts with the LRP receptor; and   b. to at least one domain on the LRP receptor,   
     thereby disrupting the interaction of sclerostin with said receptor. 
   
   
       20 . A therapeutic composition for promoting bone formation or bone remodeling comprising at least one non-native compound, at least one fragment of a non-native compound, or any combination thereof, wherein said compound or fragment binds:
 a. to at least one site on sclerostin where sclerostin interacts with the LRP receptor; and   b. to the first and second domain on the LRP receptor,   
     thereby disrupting the interaction of sclerostin with said receptor. 
   
   
       21 . The composition of  claim 12 ,  13 ,  14 ,  15 ,  16 ,  17 ,  18 ,  19  or  20  wherein said compound or said fragment of a compound comprises a small molecule, protein, peptide, polypeptide, cyclic molecule, heterocyclic organic molecule, nucleic acid, lipid, charged lipid, polar lipid, non-polar lipid, sugar, glycoprotein, glycolipid, lipoprotein or chemical. 
   
   
       22 . The composition of  claim 12 ,  13 ,  14 ,  15 ,  16 ,  17 ,  18 ,  19  or  20  wherein said compound or said fragment of a compound is an antibody or a fragment of an antibody.