Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati, Medical Sciences Building, Cincinnati, OH 45267, U.S.A.
Biochem J. 2020 Sep 18;477(17):3167-3182. doi: 10.1042/BCJ20200552.
The DAN (differential screening-selected gene aberrative in neuroblastoma) family are a group of secreted extracellular proteins which typically bind to and antagonize BMP (bone morphogenetic protein) ligands. Previous studies have revealed discrepancies between the oligomerization state of certain DAN family members, with SOST (a poor antagonist of BMP signaling) forming a monomer while Grem1, Grem2, and NBL1 (more potent BMP antagonists) form non-disulfide linked dimers. The protein SOSTDC1 (Sclerostin domain containing protein 1) is sequentially similar to SOST, but has been shown to be a better BMP inhibitor. In order to determine the oligomerization state of SOSTDC1 and determine what effect dimerization might have on the mechanism of DAN family antagonism of BMP signaling, we isolated the SOSTDC1 protein and, using a battery of biophysical, biochemical, and structural techniques, showed that SOSTDC1 forms a highly stable non-covalent dimer. Additionally, this SOSTDC1 dimer was shown, using an in vitro cell based assay system, to be an inhibitor of multiple BMP signaling growth factors, including GDF5, while monomeric SOST was a very poor antagonist. These results demonstrate that SOSTDC1 is distinct from paralogue SOST in terms of both oligomerization and strength of BMP inhibition.
DAN（神经母细胞瘤差异筛选选择的基因异常）家族是一组分泌的细胞外蛋白，通常与 BMP（骨形态发生蛋白）配体结合并拮抗。先前的研究表明，某些 DAN 家族成员的寡聚化状态存在差异，SOST（BMP 信号的低效拮抗剂）形成单体，而 Grem1、Grem2 和 NBL1（更强效的 BMP 拮抗剂）形成非二硫键连接的二聚体。SOSTDC1（含 Sclerostin 结构域蛋白 1）蛋白在序列上与 SOST 相似，但已被证明是更好的 BMP 抑制剂。为了确定 SOSTDC1 的寡聚化状态，并确定二聚化可能对 DAN 家族拮抗 BMP 信号机制的影响，我们分离了 SOSTDC1 蛋白，并使用一系列生物物理、生化和结构技术，表明 SOSTDC1 形成高度稳定的非共价二聚体。此外，使用体外基于细胞的测定系统，该 SOSTDC1 二聚体被证明是多种 BMP 信号生长因子（包括 GDF5）的抑制剂，而单体 SOST 则是一种很差的拮抗剂。这些结果表明，SOSTDC1 在寡聚化和 BMP 抑制强度方面与同源物 SOST 不同。
