Piek E, Franzén P, Heldin C H, ten Dijke P
Department of Cell Biology, University of Nijmegen, The Netherlands.
J Cell Physiol. 1997 Dec;173(3):447-59. doi: 10.1002/(SICI)1097-4652(199712)173:3<447::AID-JCP17>3.0.CO;2-8.
We have characterized a 60-kDa transforming growth factor-beta (TGF-beta) binding protein that was originally identified on LNCaP adenocarcinoma prostate cells by affinity cross-linking of cell surface proteins by using 125I-TGF-beta 1. Binding of 125I-TGF-beta 1 to the 60-kDa protein was competed by an excess of unlabeled TGF-beta 1 but not by TGF-beta 2, TGF-beta 3, activin, or osteogenic protein-1 (OP-1), also termed bone morphogenetic protein-7 (BMP-7). In addition, no binding of 125I-TGF-beta 2 and 125I-TGF-beta 3 to the 60-kDa binding protein on LNCaP cells could be demonstrated by using affinity labeling techniques. The 60-kDa TGF-beta binding protein showed no immunoreactivity with antibodies against the known type I and type II receptors for members of the TGF-beta superfamily. Treatment of LNCaP cells with 0.25 M NaCl, 1 microgram/ml heparin, or 10% glycerol caused a release of the 60-kDa protein from the cell surface. In addition, we found that the previously described TGF-beta type IV receptor on GH3 cells, which does not form a heterometric complex with TGF-beta receptors, could be released from the cell surface by these same treatments. This suggests that the 60-kDa protein and the similarly sized TGF-beta type IV receptor are related proteins. The eluted 60-kDa LNCaP protein was shown to interfere with the binding of TGF-beta to the TGF-beta receptors. Thus, the cell surface-associated 60-kDa TGF-beta binding protein may play a role in regulating TGF-beta binding to TGF-beta receptors.
我们已鉴定出一种60 kDa的转化生长因子-β（TGF-β）结合蛋白，该蛋白最初是通过使用¹²⁵I-TGF-β1对LNCaP前列腺腺癌细胞表面蛋白进行亲和交联而鉴定出来的。¹²⁵I-TGF-β1与60 kDa蛋白的结合可被过量的未标记TGF-β1竞争，但不能被TGF-β2、TGF-β3、激活素或成骨蛋白-1（OP-1，也称为骨形态发生蛋白-7，即BMP-7）竞争。此外，使用亲和标记技术未检测到¹²⁵I-TGF-β2和¹²⁵I-TGF-β3与LNCaP细胞上60 kDa结合蛋白的结合。60 kDa的TGF-β结合蛋白与针对TGF-β超家族成员已知的I型和II型受体的抗体没有免疫反应性。用0.25 M NaCl、1 μg/ml肝素或10%甘油处理LNCaP细胞会导致60 kDa蛋白从细胞表面释放。此外，我们发现GH3细胞上先前描述的TGF-βIV型受体，它不与TGF-β受体形成异源复合物，也可通过相同处理从细胞表面释放。这表明60 kDa蛋白和大小相似的TGF-βIV型受体是相关蛋白。洗脱的LNCaP 60 kDa蛋白被证明会干扰TGF-β与TGF-β受体的结合。因此，细胞表面相关的60 kDa TGF-β结合蛋白可能在调节TGF-β与TGF-β受体的结合中起作用。
