Lakkakorpi P T, Horton M A, Helfrich M H, Karhukorpi E K, Väänänen H K
Department of Anatomy, University of Oulu, Finland.
J Cell Biol. 1991 Nov;115(4):1179-86. doi: 10.1083/jcb.115.4.1179.
During bone resorption, osteoclasts form a tight attachment, the sealing zone, around resorption lacunae. Vitronectin receptor has previously been shown to be expressed in osteoclasts and it has been suggested that it mediates the tight attachment at the sealing zone. In this study we have shown that glycine-arginine-glycine-aspartic acid-serine pentapeptide inhibits bone resorption by isolated osteoclasts and drastically changes the morphology of the osteoclasts. When the vitronectin receptor was localized by immunofluorescence in rat and chicken osteoclasts cultured on bone slices, it was found to be distributed throughout the osteoclast cell membrane except in the sealing zone areas. Immunoperoxidase staining of rat bone sections at the light microscopical level also revealed intense staining of the cell membrane with occasional small unstained areas, probably corresponding to the sealing zones. Immunoelectron microscopy confirmed the results obtained by light microscopy showing specific labeling only at the ruffled borders and basolateral membranes (0.82 and 2.43 gold particles/microns of membrane, respectively), but not at the sealing zone areas (0.06 gold particles/microns of membrane). Both alpha v and beta 3 subunits of the vitronectin receptor were similarly localized. These results strongly suggest that, although the vitronectin receptor is important in the function of osteoclasts, it is not mediating the final sealing zone attachment of the osteoclasts to the mineralized bone surface.
在骨吸收过程中，破骨细胞在吸收陷窝周围形成紧密附着，即封闭区。此前已表明玻连蛋白受体在破骨细胞中表达，有人提出它介导封闭区的紧密附着。在本研究中，我们发现甘氨酸 - 精氨酸 - 甘氨酸 - 天冬氨酸 - 丝氨酸五肽可抑制分离的破骨细胞的骨吸收，并显著改变破骨细胞的形态。当通过免疫荧光法在骨切片上培养的大鼠和鸡破骨细胞中定位玻连蛋白受体时，发现它分布于破骨细胞的整个细胞膜，封闭区除外。在光学显微镜水平对大鼠骨切片进行免疫过氧化物酶染色也显示细胞膜有强烈染色，偶尔有小的未染色区域，可能对应于封闭区。免疫电子显微镜证实了光学显微镜的结果，显示仅在皱襞缘和基底外侧膜有特异性标记（分别为每微米膜0.82和2.43个金颗粒），而在封闭区没有（每微米膜0.06个金颗粒）。玻连蛋白受体的αv和β3亚基定位情况相似。这些结果强烈表明，尽管玻连蛋白受体在破骨细胞功能中很重要，但它并不介导破骨细胞与矿化骨表面的最终封闭区附着。
