Katoh K, Masuda M, Kano Y, Jinguji Y, Fujiwara K
Department of Structural Analysis, National Cardiovascular Center Research Institute, Osaka, Japan.
Cell Motil Cytoskeleton. 1995;31(3):177-95. doi: 10.1002/cm.970310302.
Human fibroblasts stained with fluorescently labeled phalloidin revealed many stress fibers within the apical cytoplasm in addition to those located along the basal plasma membrane and associated with focal adhesions. The staining patterns of these apical stress fibers with fluorescent phalloidin, anti-alpha-actinin, and antimyosin were identical to those of the basal stress fibers, suggesting the same macromolecular organization for both types of stress fibers. There were two types of apical stress fibers that clearly interacted with the apical plasma membrane, those extending between the basal and the apical plasma membrane and those having both ends on the basal membrane forming arches whose top interacted with the apical plasma membrane. By electron microscopy, we observed that apical stress fibers were associated with the apical plasma membrane via electron-dense plaques reminiscent of the focal adhesion. Since several proteins have been specifically localized to the focal adhesion site, we examined whether they were also present at the apical stress fiber-membrane association site by using immunocytochemical methods and image reconstruction techniques. We found that vinculin, talin, paxillin, a fibronectin receptor protein, several integrin subunits including beta 1, fibronectin, and proteins with phosphorylated tyrosine were also components of the apical plaque. These observations indicate that apical stress fibers are attached to the plasma membrane by using principally the same molecular assembly as the focal adhesion associated with the basal stress fiber. We suggest that the complex molecular organization of the focal adhesion is not demanded by cell adhesion, but rather it is needed for anchoring stress fibers to the plasma membrane. Apical plaques did not stain with the anti-integrin alpha v subunit or anti-focal adhesion associated kinase (FAK), although these antibodies stained focal adhesions. These results suggest that the apical stress fiber-membrane contact has some important functions different from those of the focal adhesion.
用荧光标记的鬼笔环肽染色的人成纤维细胞显示，除了沿基底质膜分布并与粘着斑相关的应力纤维外，顶端细胞质内还有许多应力纤维。这些顶端应力纤维用荧光鬼笔环肽、抗α - 辅肌动蛋白和抗肌球蛋白染色的模式与基底应力纤维相同，表明这两种类型的应力纤维具有相同的大分子组织。有两种类型的顶端应力纤维与顶端质膜明显相互作用，一种在基底质膜和顶端质膜之间延伸，另一种两端位于基底膜上形成弓形，其顶部与顶端质膜相互作用。通过电子显微镜观察，我们发现顶端应力纤维通过类似于粘着斑的电子致密斑与顶端质膜相关联。由于几种蛋白质已被特异性定位于粘着斑部位，我们通过免疫细胞化学方法和图像重建技术检查它们是否也存在于顶端应力纤维 - 膜结合部位。我们发现纽蛋白、踝蛋白、桩蛋白、一种纤连蛋白受体蛋白、包括β1在内的几种整合素亚基、纤连蛋白以及磷酸化酪氨酸的蛋白质也是顶端斑的组成成分。这些观察结果表明，顶端应力纤维主要通过与基底应力纤维相关的粘着斑相同的分子组装附着于质膜。我们认为，粘着斑复杂的分子组织并非细胞粘附所必需，而是将应力纤维锚定到质膜所需要的。顶端斑用抗整合素αv亚基抗体或抗粘着斑相关激酶（FAK）抗体染色时不着色，尽管这些抗体可使粘着斑染色。这些结果表明，顶端应力纤维 - 膜接触具有一些与粘着斑不同的重要功能。
