Ehler E, Babiychuk E, Draeger A
Institute of Molecular Biology, Austrian Academy of Sciences, Salzburg, Austria.
Cell Motil Cytoskeleton. 1996;34(4):288-98. doi: 10.1002/(SICI)1097-0169(1996)34:4<288::AID-CM4>3.0.CO;2-4.
Single cells displaying many characteristics in common with smooth muscle are now being identified in many organs. Although their origin remains elusive, they are nonetheless known to play a major role in fibroproliferative diseases and stromal reactions by virtue of their contractile properties. We have investigated the contractile properties and expression of smooth muscle-associated proteins in such a cell line derived from human foetal lung (IMR-90). For almost two decades, these cells have served as model fibroblasts in a wide variety of studies. And yet, IMR-90 cells manifest many features characteristic of differentiated smooth muscle cells: they exhibit the same elongated, slender form and the strikingly regular, longitudinal alignment of their actin-attachment sites, which are indispensable for coordinated contraction. Moreover, these adhaerens junctions also contain metavinculin, the smooth muscle analogue of vinculin, the stable expression of which has not previously been demonstrated in cultured cells. Since sm 22, as well as the smooth muscle-associated alpha-actin isoform and calponin are also expressed, IMR-90 cells must now be classified as myofibroblasts. When cultivated on a rubbery silicon surface, IMR-90 cells respond to stimulation with a rate of contraction which is considerably faster than that exhibited by fibroblasts derived from other established lines. Taken together, the regular longitudinal orientation of the adhaerens junctions, the stable expression of metavinculin, and the rapid speed of shortening in IMR-90 cells suggest, by implication, that the periodicity of actin attachment sites is a fundamental determinant of contractile efficiency in smooth muscle cells; this spacing may be mediated by metavinculin.
目前在许多器官中都发现了具有许多与平滑肌相同特征的单细胞。尽管它们的起源尚不清楚，但由于其收缩特性，已知它们在纤维增生性疾病和基质反应中起主要作用。我们研究了源自人胎儿肺（IMR-90）的这种细胞系的收缩特性和平滑肌相关蛋白的表达。在近二十年的时间里，这些细胞在各种各样的研究中都作为模型成纤维细胞。然而，IMR-90细胞表现出许多分化的平滑肌细胞的特征：它们呈现出相同的细长形态，其肌动蛋白附着位点具有惊人的规则纵向排列，这对于协调收缩是必不可少的。此外，这些黏附连接还含有间皮肌动蛋白，它是肌动蛋白的平滑肌类似物，其稳定表达此前尚未在培养细胞中得到证实。由于sm 22以及平滑肌相关的α-肌动蛋白同工型和钙调蛋白也有表达，现在IMR-90细胞必须被归类为肌成纤维细胞。当在橡胶状硅表面培养时，IMR-90细胞对刺激的收缩速率比源自其他已建立细胞系的成纤维细胞快得多。综上所述，IMR-90细胞中黏附连接的规则纵向取向、间皮肌动蛋白的稳定表达以及快速缩短速度暗示，肌动蛋白附着位点的周期性是平滑肌细胞收缩效率的一个基本决定因素；这种间距可能由间皮肌动蛋白介导。
