About SOST / Sclerostin:
Sclerostin is a protein in humans that is encoded by the SOST gene. It is also identified by the following aliases: CDD, SOST1, VBCH, and DAND6. It is a glycoprotein that's secreted in the body and has a C-terminal cysteine knot-like domain. Its sequence can be compared to that of the DAN family of bone morphogenetic protein antagonists. More often than not, this protein is produced by the osteocyte, though it is found in other tissues as well.
SOST has a length of 213 residues and a secondary structure that has been determined by protein NMR. It is a 28% beta-sheet, with 6 stands and 32 residues. This protein is the product of the SOST gene and is found on chromosome 17q12-q21 in humans.
Sclerostin Functions & Interactions
Initially, sclerostin was thought to be a non-classical bone morphogenetic protein (BMP) antagonist. However, more recent data and studies have concluded that this protein binds to LRP5/6 receptors and inhibits the Wnt signaling pathway. As a consequence, this leads to decreased bone formation.
It is currently unclear on the precise mechanisms that are responsible for this function, but many experts believe that the antagonism of BMP-induced bone formation by sclerostin is mediated by Wnt signaling, rather than BMP signaling pathways.
Sclerostin is mainly expressed in osteocytes and some chondrocytes, preventing bone formation by osteoblasts. Often, the production of this protein by osteocytes is inhibited by parathyroid hormone, mechanical loading, estrogen, and various cytokines. On the other hand, the production of this protein is increased by calcitonin.