TY  - JOUR
A1  - van Dinther, Maarten
A1  - Zhang, Juan
A1  - Weidauer, Stella E.
A1  - Boschert, Verena
A1  - Muth, Eva-Maria
A1  - Knappik, Achim
A1  - de Gorter, David J. J.
A1  - van Kasteren, Puck B.
A1  - Frisch, Christian
A1  - Müller, Thomas D.
A1  - ten Dijke, Peter
T1  - Anti-Sclerostin Antibody Inhibits Internalization of Sclerostin and Sclerostin-Mediated Antagonism of Wnt/LRP6 Signaling
JF  - PLoS ONE
N2  - Sclerosteosis is a rare high bone mass disease that is caused by inactivating mutations in the SOST gene. Its gene product, Sclerostin, is a key negative regulator of bone formation and might therefore serve as a target for the anabolic treatment of osteoporosis. The exact molecular mechanism by which Sclerostin exerts its antagonistic effects on Wnt signaling in bone forming osteoblasts remains unclear. Here we show that Wnt3a-induced transcriptional responses and induction of alkaline phosphatase activity, an early marker of osteoblast differentiation, require the Wnt co-receptors LRP5 and LRP6. Unlike Dickkopf1 (DKK1), Sclerostin does not inhibit Wnt-3a-induced phosphorylation of LRP5 at serine 1503 or LRP6 at serine 1490. Affinity labeling of cell surface proteins with \([^{125} I]\) Sclerostin identified LRP6 as the main specific Sclerostin receptor in multiple mesenchymal cell lines. When cells were challenged with Sclerostin fused to recombinant green fluorescent protein (GFP) this was internalized, likely via a Clathrin-dependent process, and subsequently degraded in a temperature and proteasome-dependent manner. Ectopic expression of LRP6 greatly enhanced binding and cellular uptake of Sclerostin-GFP, which was reduced by the addition of an excess of non-GFP-fused Sclerostin. Finally, an anti-Sclerostin antibody inhibited the internalization of Sclerostin-GFP and binding of Sclerostin to LRP6. Moreover, this antibody attenuated the antagonistic activity of Sclerostin on canonical Wnt-induced responses.
KW  - gene
KW  - rat model
KW  - Dickkopf proteins
KW  - postmenopausal osteoporosis
KW  - increases bone-formation
KW  - WNT
KW  - LRP6
KW  - density
KW  - receptor
KW  - ligand
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-130981
VL  - 8
IS  - 4
ER  -