Aggeler J
Department of Human Anatomy, School of Medicine, University of California, Davis 95616.
Cell Motil Cytoskeleton. 1990;16(2):121-32. doi: 10.1002/cm.970160206.
Modulation of the synthesis and secretion of extracellular matrix proteins and matrix-degrading metalloproteases by rabbit synovial fibroblasts is an important model system for studying the control of tissue-specific gene expression. Induction of collagenase expression is correlated with changes in cell shape and actin filament distribution, but the role of the cellular cytoskeleton in the sustained synthesis and secretion of metalloproteases has not been closely examined. When cells were allowed to respread after rounding by trypsin or cytochalasin, two known metalloprotease inducers, reformation of stress fibers was observed within 2 h in the presence of serum. In the absence of serum, trypsin-treated cells did not respread substantially, even after 24 h in culture. In contrast, cytochalasin-treated cells recovered almost as rapidly in the absence as in the presence of serum, showing reformation of well-formed microfilament bundles within 30 min of drug removal, especially at the spreading cell edges. High resolution electron-microscopic views of detergent-extracted cytoskeletons confirmed the rapid rebundling of peripheral microfilaments. Acrylamide-treated cells fell between these two extremes, spreading slowly in the absence of serum, but almost as rapidly as cytochalasin-treated cells in its presence. Reestablishment of normal intermediate filament distribution generally lagged slightly behind actin for all treatments, and intermediate filaments always appeared to spread back into the cellular cytoplasm within the confines of the reforming peripheral microfilament bundles. No obvious interaction between these two cytoskeletal elements was observed after any treatment, and no specific role for intermediate filaments in modulating gene expression in these cells is suggested by these results. The serum dependence displayed after trypsin or acrylamide treatment may be due to the disturbances in fibronectin synthesis observed in these cells and is consistent with evidence that both induction and sustained expression of matrix-degrading metalloprotease may involve signals transduced through plasma membrane matrix receptors (integrins).
兔滑膜成纤维细胞对细胞外基质蛋白和基质降解金属蛋白酶合成与分泌的调节是研究组织特异性基因表达调控的重要模型系统。胶原酶表达的诱导与细胞形状和肌动蛋白丝分布的变化相关，但细胞骨架在金属蛋白酶持续合成和分泌中的作用尚未得到深入研究。当细胞经胰蛋白酶或细胞松弛素处理变圆后再铺展时（胰蛋白酶和细胞松弛素是两种已知的金属蛋白酶诱导剂），在有血清存在的情况下，2小时内可观察到应力纤维的重新形成。在无血清条件下，经胰蛋白酶处理的细胞即使培养24小时也基本不会大量铺展。相比之下，经细胞松弛素处理的细胞在无血清和有血清时恢复速度几乎一样快，在去除药物后30分钟内即可观察到形成良好的微丝束重新形成，尤其是在铺展细胞边缘。去污剂提取的细胞骨架的高分辨率电子显微镜观察证实了外周微丝的快速重新束集。经丙烯酰胺处理的细胞情况介于上述两种极端情况之间，在无血清时铺展缓慢，但在有血清时铺展速度几乎与经细胞松弛素处理的细胞一样快。对于所有处理，正常中间丝分布的重新建立通常比肌动蛋白稍滞后，并且中间丝似乎总是在重新形成的外周微丝束范围内扩散回细胞质中。任何处理后均未观察到这两种细胞骨架成分之间有明显相互作用，这些结果也未表明中间丝在调节这些细胞基因表达中有特定作用。胰蛋白酶或丙烯酰胺处理后显示出的血清依赖性可能是由于这些细胞中观察到的纤连蛋白合成受到干扰，这与基质降解金属蛋白酶的诱导和持续表达可能涉及通过质膜基质受体（整合素）转导的信号这一证据一致。
