Andreoli J M, Trevor K T
Center for Molecular Medicine and Genetics, Wayne State University, Detroit, Michigan, USA.
Cell Motil Cytoskeleton. 1995;32(1):10-25. doi: 10.1002/cm.970320103.
Cytoskeletal intermediate filaments (IFs) constitute a diverse family of proteins whose members are expressed in tissue-specific patterns. Although vimentin IFs are normally restricted to mesenchyme, a variety of cell types express vimentin alone or together with cell-specific IFs during growth, differentiation, and neoplasia. In this study, we have investigated the influence of increased vimentin expression on the simple epithelial cell phenotype. An expression vector encoding a human vimentin cDNA was transfected into murine HR9 endoderm and F9 embryonal carcinoma cell lines, which serve as models for early extraembryonic epithelial differentiation. Stable clones that expressed varying levels of human vimentin were characterized by human vimentin were characterized by immunofluorescence and biochemical analysis. A relatively high level of vimentin expression in HR9 and differentiated F9 epithelial cells resulted in aberrant vimentin structures with co-collapse of keratin K8/K18 filaments and lowered amounts of keratin protein. In F9 epithelial cells, the desmosomal proteins DP I/II did not appear to localize to cell surface desmosome s but rather but rather co-aggregated with the perturbed IFs. Although overall cell morphology was not dramatically altered, individual nuclei were distorted by excess intracellular vimentin. Furthermore, cell proliferation as well as the cell spreading response time were slowed. Ther appears to be a threshold effect regarding overall vimentin levels as cells that expressed lower amounts of the human vimentin exhibited no obvious structural nor biological effects. Our results demonstrate that wild-type vimentin can act as a "mutant" protein when present at high intracellular levels, inducing a variety of phenotypic changes.
细胞骨架中间丝（IFs）构成了一个多样化的蛋白质家族，其成员以组织特异性模式表达。虽然波形蛋白中间丝通常局限于间充质，但在生长、分化和肿瘤形成过程中，多种细胞类型单独表达波形蛋白或与细胞特异性中间丝共同表达。在本研究中，我们研究了波形蛋白表达增加对简单上皮细胞表型的影响。将编码人波形蛋白cDNA的表达载体转染到小鼠HR9内胚层和F9胚胎癌细胞系中，这两种细胞系可作为早期胚外上皮分化的模型。通过免疫荧光和生化分析对表达不同水平人波形蛋白的稳定克隆进行了表征。HR9和分化的F9上皮细胞中相对高水平的波形蛋白表达导致波形蛋白结构异常，角蛋白K8/K18丝共塌陷，角蛋白含量降低。在F9上皮细胞中，桥粒蛋白DP I/II似乎没有定位于细胞表面桥粒，而是与受干扰的中间丝共聚集。虽然总体细胞形态没有明显改变，但单个细胞核因细胞内过量的波形蛋白而变形。此外，细胞增殖以及细胞铺展反应时间减慢。对于总体波形蛋白水平似乎存在阈值效应，因为表达较低量人波形蛋白的细胞没有表现出明显的结构或生物学效应。我们的结果表明，野生型波形蛋白在细胞内高水平存在时可作为一种“突变”蛋白，诱导多种表型变化。
