CLATHRIN SHEETS AND CYTOSKELETAL STRCTURES ON THE PROTOPLASMIC SURAFCE OF THE VENTRAL MEMBRANES OF OSTEOCLASTS IN CULTURE

物理细胞剪切导致基侧(上层)膜、细胞骨架或细胞器不同程度的破坏，并暴露出附着在下面的底物(如盖片、云母或合成磷灰石板)上的破骨细胞的外膜(粘附膜)的原生质面。细胞剪切后残留在基质上的腹膜冻干复制品提供了培养破骨细胞原生质膜表面超微结构的三维信息。可见广泛的原生质面和附着在质膜贴壁表面的不同数量的细胞骨架结构。特别是，本研究最具特色的发现是，腹膜上显示了大量显示不同大小、形状和曲率的网状蛋白片层。笼状晶格的多边形亚结构似乎是由带有少量五角形…的六边形组成更多的名词穿插其中。可在边缘旁区域看到它们，它们位于与下层密切接触的部位。此外，在基侧(上)膜上从未观察到笼状蛋白晶格。在良好的立体视图中，大多数细胞骨架不与网状蛋白片层直接接触。尽管人们普遍认为破骨细胞等运动细胞中的细胞骨架足在细胞黏附中起主要作用，但目前的研究表明，膜相关的笼蛋白也可能在黏附于底物的过程中发挥作用。在这一点上，网状蛋白被认为是受体介导的内吞作用所必需的，但它是否也可能在细胞附着中发挥作用仍是一个有争议的问题。这种类型的网状蛋白相关的黏附似乎是破骨细胞中细胞/底物黏附的一个先前未被发现的部位。为了评估这一可能的功能，我们较少地关注培养的破骨细胞腹膜上的笼蛋白和相关的细胞骨架元件。

Physical cell shearing resulted in various degrees of disruption of the basolateral (upper) membranes, cytoskeletons or cell organelles, and exposed the protoplasmic surface of vental (adhesion) membranes of steoclasts that were attached to the underlying substratum such as cover slips, mica or synthetic apatite plates. Freeze-dried replicas of the ventral membranes left behind on the substratum after cell-shearing provided 3-dimensional information on the ultrastructure of the protoplasmic membrane surface of cultured osteoclasts. An extensive area of the protoplasmic surface and various amounts of cytoskeletal structures attached to the adherent vental surface of the plasma membrane were visible. In particular, the most characteristic finding of the present study is that numerous clathrin sheets displaying various sizes, shapes and curvature were revealed on the ventral membrane. The polygon substructures of the clathrin lattices appeared to be composed of hexagons with a few pentago … More ns interspersed. They were seen at the paramarginal area where they were situated at the sites of close contact with the underlying substratum. In addition, clathrin lattices were never observed on the basolateral (upper) membranes. In favorable stereo views, most of cytoskeletons were not in direct contact with the clathrin sheets. However, a few observations indicated that possible remnants of cytoskeletons attached to clathrin latticesAlthough it is generally accepted that the cytoskeletal podosomes in motile cells such as osteoclasts play a major role in cell adhesion, the present study indicates that membrane-associated clathrin may also function during the attachment to the substrate. In this regard, clathrin is thought to be required for receptor-mediated endocytosis, but whether it may also function in cell attachment is still a matter for debate. This type of clathrin-related adhesion appears to be a previously unrecognized site of cell / substrate adhesion in osteoclasts. To assess this possible function, we focused on clathrin and related cytoskeletal elements on the ventral membranes of cultured osteoclasts Less