Department of Oral Anatomy and Neurobiology, Graduate School of Dentistry, Osaka University, Japan.
Exp Cell Res. 2021 Feb 1;399(1):112433. doi: 10.1016/j.yexcr.2020.112433. Epub 2020 Dec 23.
Osteoclasts seeded on either glass coverslips or apatite pellets have at least two morphologically distinct substrate adhesion sites: actin-based adhesion structures including podosome belts and sealing zones, and adjacent clathrin sheets. Clathrin-coated structures are exclusively localized at the podosome belts and sealing zone, in both of which the plasma membrane forms a tight attachment to the substrate surface. When cultured on apatite osteoclasts can degrade the apatite leading to the formation of resorption lacunae. The sealing zone divides the ventral membrane into different domains, outside and inside of the sealing zones. The former facing the smooth-surfaced intact apatite contains relatively solitary or networks of larger flat clathrin structures; and the latter, facing the rough-surfaced degraded apatite in the resorption lacunae contain clathrin in various shapes and sizes. Clathrin assemblies on the membrane domain facing not only a resorption lacuna, or trails but also intact apatite indeed were observed to be heterogeneous in size and intensity, suggesting that they appeared to follow variations in the surface topography of the apatite surface. These results provide a detailed insight into the flat clathrin sheets that have been suggested to be the sites of adhesion and mechanosensing in co-operation with podosomes.
基于肌动蛋白的附着结构，包括足突带和封闭带，以及相邻的网格蛋白片层。网格蛋白包被结构仅定位于足突带和封闭带，在这两个部位，质膜与基质表面紧密附着。当在磷灰石上培养时，破骨细胞可以降解磷灰石，导致吸收陷窝的形成。封闭带将腹膜分为不同的区域，封闭带的外部和内部。前者朝向光滑表面完整的磷灰石，包含相对孤立或较大的平面网格蛋白结构网络；后者朝向吸收陷窝中粗糙表面降解的磷灰石，包含各种形状和大小的网格蛋白。面向不仅是吸收陷窝，还是完整磷灰石的膜域上的网格蛋白组装体在大小和强度上确实存在异质性，表明它们似乎跟随磷灰石表面形貌的变化。这些结果深入了解了平面网格蛋白片层，这些片层被认为是与足突一起进行粘附和机械感应的部位。
