Membrane associated clathrin sheets as a possible adhesion structure in cultured osteoclasts

本研究的目的是用免疫荧光显微镜和电子显微镜观察细胞剪除或洗涤剂提取后破骨细胞的细胞-基质黏附结构。鉴定出两种不同的黏附结构：一种是典型的足体，另一种是笼状结构。在速冻、冷冻替代或冷冻干燥的复制品中，笼状蛋白呈现典型的蜂窝状亚结构，由六边形或五角形的多边形组成(每个多边形的直径为20~30 nm)。这些网状蛋白片常见于腹膜的周围或中央区域。几乎没有细胞骨架，而足体由微丝和相关结构组成。在某些情况下，运动的破骨细胞的假平台的腹膜包含几个笼状蛋白片层。此外，即使在使用机械细胞剪切和化学洗涤剂提取去除了几乎所有的细胞结构之后，细胞表面仍留下了网状蛋白片层。综上所述，这些结果支持这一观点，即笼状蛋白片层可能通过受体-配体相互作用在破骨细胞黏附中发挥作用。

The purpose of the present study is to investigate the cell-substratum adhesion structures in cultured osteoclasts using immunofluorescent microscopy and electron microscopy after cell shearing or detergent extraction. Two different adhesion structures were identified ; one was typical podosomes and the other clathrin sheets. In quick-freezing and freeze-substituted or freeze-dried replicas the clathrins showed a typical honey-comb substructure which were composed of polygons with hexagonal or pentagonal in shape (each polygon was 20〜30nm in diameter). These clathrin sheets were often encountered the peripheral or central region of the ventral membrane. Almost clathrin sheets were devoid of the cytoskeletons, while podosomes were composed of the bundles of microfilaments and related structures. In some case, the ventral membrane of pseudo-podium in moving osteoclasts contained several clathrin sheets. In addition clathrin sheets were left behind the cell surface even after almost cellular structures had removed away by using mechanical cell shearing and chemical detergent extraction. In conclusion, these results, therefore, support the idea that the clathrin sheets plays a possible role in osteoclastic adhesion via receptor-ligand interaction.