Takahashi K, Takahashi F, Tanabe K K, Takahashi H, Fukuchi Y
Department of Respiratory Medicine, Juntendo University, School of Medicine, Tokyo, Japan.
Biochem Mol Biol Int. 1998 Dec;46(6):1081-92. doi: 10.1080/15216549800204632.
Osteopontin (OPN) is a secreted glycoprotein implicated in cell adhesion. It contains the arginine-glycine-asparatic acid (RGD) cell adhesive domain and the thrombin cleavage sequence. Although thrombin cleavage of OPN has been shown to be of physiological importance, the function of C-terminal OPN fragment cleaved by thrombin remains unknown. To determine its role, we performed cell adhesion assays using glutathione S-transferase-OPN fusion protein fragments and full-length OPN fusion protein. The N-terminal fragment containing RGD motif promoted enhanced adhesion of mouse and human fibroblasts by 2.9 and 2.8 folds in comparison with full-length OPN, respectively. The enhanced adhesion of both cells mediated by N-terminal fragment was significantly suppressed by addition of C-terminal fragment lacking RGD motif that has less cell adhesive property than full-length OPN. These results suggest that the C-terminal domain may play a pivotal role in regulating OPN functions by suppressing the RGD-dependent cell adhesion.
骨桥蛋白（OPN）是一种参与细胞黏附的分泌型糖蛋白。它含有精氨酸 - 甘氨酸 - 天冬氨酸（RGD）细胞黏附结构域和凝血酶切割序列。尽管已证明凝血酶对OPN的切割具有生理重要性，但凝血酶切割产生的OPN C末端片段的功能仍不清楚。为了确定其作用，我们使用谷胱甘肽S - 转移酶 - OPN融合蛋白片段和全长OPN融合蛋白进行了细胞黏附试验。与全长OPN相比，含有RGD基序的N末端片段分别使小鼠和人成纤维细胞的黏附增强了2.9倍和2.8倍。通过添加缺乏RGD基序且细胞黏附特性比全长OPN弱的C末端片段，显著抑制了由N末端片段介导的两种细胞的增强黏附。这些结果表明，C末端结构域可能通过抑制RGD依赖的细胞黏附在调节OPN功能中起关键作用。
