Arpin M, Friederich E, Algrain M, Vernel F, Louvard D
Unité de Biologie des Membranes, URA CNRS, Département de Biologie Moléculaire, Institut Pasteur, Paris.
J Cell Biol. 1994 Dec;127(6 Pt 2):1995-2008. doi: 10.1083/jcb.127.6.1995.
Fimbrins/plastins are a family of highly conserved actin-bundling proteins. They are present in all eukaryotic cells including yeast, but each isoform displays a remarkable tissue specificity. T-plastin is normally found in epithelial and mesenchymal cells while L-plastin is present in hematopoietic cells. However, L-plastin has been also found in tumor cells of non-hematopoietic origin (Lin, C.-S., R. H. Aebersold, S. B. Kent, M. Varma, and J. Leavitt. 1988. Mol. Cell. Biol. 8:4659-4668; Lin, C.-S., R. H. Aebersold, and J. Leavitt. 1990. Mol. Cell. Biol. 10: 1818-1821). To learn more about the biological significance of their tissue specificity, we have overproduced the T- and L-plastin isoforms in a fibroblast-like cell line, CV-1, and in a polarized epithelial cell line, LLC-PK1. In CV-1 cells, overproduction of T- and L-plastins induces cell rounding and a concomitant reorganization of actin stress fibers into geodesic structures. L-plastin remains associated with microfilaments while T-plastin is almost completely extracted after treatment of the cells with non-ionic detergent. In LLC-PK1 cells, T-plastin induces shape changes in microvilli and remains associated with microvillar actin filaments after detergent extraction while L-plastin has no effect on these structures and is completely extracted. The effect of T-plastin on the organization of microvilli differs from that of villin, another actin-bundling protein. Our experiments indicate that these two isoforms play differing roles in actin filament organization, and do so in a cell type-specific fashion. Thus it is likely that these plastin isoforms play fundamentally different roles in cell function.
丝束肌动蛋白/丝束蛋白是一类高度保守的肌动蛋白成束蛋白家族。它们存在于包括酵母在内的所有真核细胞中，但每种亚型都表现出显著的组织特异性。T-丝束蛋白通常存在于上皮细胞和间充质细胞中，而L-丝束蛋白存在于造血细胞中。然而，在非造血来源的肿瘤细胞中也发现了L-丝束蛋白（林，C.-S.，R. H. 埃伯索尔德，S. B. 肯特，M. 瓦尔马，和J. 莱维特。1988年。《分子与细胞生物学》8:4659 - 4668；林，C.-S.，R. H. 埃伯索尔德，和J. 莱维特。1990年。《分子与细胞生物学》10: 1818 - 1821）。为了更多地了解它们组织特异性的生物学意义，我们在成纤维细胞样细胞系CV - 1和极化上皮细胞系LLC - PK1中过量表达了T-和L-丝束蛋白亚型。在CV - 1细胞中，过量表达T-和L-丝束蛋白会诱导细胞变圆，并伴随着肌动蛋白应力纤维重组为测地线结构。L-丝束蛋白仍与微丝相关，而在用非离子去污剂处理细胞后，T-丝束蛋白几乎完全被提取出来。在LLC - PK1细胞中，T-丝束蛋白诱导微绒毛形状改变，在用去污剂提取后仍与微绒毛肌动蛋白丝相关，而L-丝束蛋白对这些结构没有影响且完全被提取出来。T-丝束蛋白对微绒毛组织的影响不同于另一种肌动蛋白成束蛋白绒毛蛋白。我们的实验表明，这两种亚型在肌动蛋白丝组织中发挥不同作用，并且是以细胞类型特异性方式发挥作用。因此，这些丝束蛋白亚型很可能在细胞功能中发挥根本不同的作用。
