Nagai H, Kalanins V I
Department of Anatomy and Cell Biology, University of Toronto, Ontario, Canada.
Exp Cell Res. 1996 Feb 25;223(1):63-71. doi: 10.1006/excr.1996.0058.
A tension-sensitive microfilament (MF) system in the plane of zonula adherens (ZA) junctions of retinal pigment epithelial (RPE) cells is described. Organ cultures and whole mounts of RPE from chick embryos were labeled for F-actin and examined with a confocal laser scanning microscope. The changes in the distribution of MFs during alternations in the direction of tensional stress, generated in the organ culture system or induced by mechanical wounding, were examined. In RPE cells throughout the organ culture, fine MF bundles, termed apical stress fibers (ASF), oriented parallel to the direction in which tension had been generated, were observed at the level of circumferential MF bundles (CMBs) associated with ZA junctions. Within 24 h after the direction of the tension was experimentally altered by 90 degrees, the orientation of ASF also changed, becoming aligned along the new lines of the tension. The ASF likewise react to changes in the direction of stress generated when RPE cells respond to wounding in organ culture. The presence of similar MFs in RPE cells in the posterior retina of 13-day chick embryos in situ may reflect mechanical stretching of the RPE cells that occurs during the development of the eye. The ASF probably limit the stretching of the CMBs of RPE cells in any one direction, thereby protecting the RPE cells against tensional stress. This system of MFs may be especially important in chick RPE cells, which lack desmosomes and keratin-type intermediate filaments that normally have this function in other cell types.
本文描述了视网膜色素上皮（RPE）细胞紧密连接（ZA）平面中的张力敏感微丝（MF）系统。对鸡胚RPE的器官培养物和整装标本进行F-肌动蛋白标记，并用共聚焦激光扫描显微镜检查。研究了在器官培养系统中产生或由机械损伤诱导的张力应力方向交替过程中MF分布的变化。在整个器官培养的RPE细胞中，在与ZA连接相关的周向MF束（CMB）水平上，观察到称为顶端应力纤维（ASF）的细MF束，其方向与产生张力的方向平行。在通过实验将张力方向改变90度后的24小时内，ASF的方向也发生了变化，沿新的张力线排列。当RPE细胞在器官培养中对损伤作出反应时，ASF同样会对产生的应力方向变化作出反应。在13日龄鸡胚原位视网膜后部的RPE细胞中存在类似的MF，这可能反映了在眼睛发育过程中发生的RPE细胞的机械拉伸。ASF可能限制RPE细胞的CMB在任何一个方向上的拉伸，从而保护RPE细胞免受张力应力。这种MF系统在鸡RPE细胞中可能特别重要，因为鸡RPE细胞缺乏桥粒和角蛋白型中间丝，而在其他细胞类型中这些通常具有这种功能。
