Schweitzer S C, Klymkowsky M W, Bellin R M, Robson R M, Capetanaki Y, Evans R M
Department of Pathology, University of Colorado Health Sciences Center, Denver, Colorado, USA.
J Cell Sci. 2001 Mar;114(Pt 6):1079-89. doi: 10.1242/jcs.114.6.1079.
De novo expression of vimentin, GFAP or peripherin leads to the assembly of an extended intermediate filament network in intermediate filament-free SW13/cl.2 cells. Desmin, in contrast, does not form extended filament networks in either SW13/cl.2 or intermediate filament-free mouse fibroblasts. Rather, desmin formed short thickened filamentous structures and prominent spot-like cytoplasmic aggregates that were composed of densely packed 9-11 nm diameter filaments. Analysis of stably transfected cell lines indicates that the inability of desmin to form extended networks is not due to a difference in the level of transgene expression. Nestin, paranemin and synemin are large intermediate filament proteins that coassemble with desmin in muscle cells. Although each of these large intermediate filament proteins colocalized with desmin when coexpressed in SW-13 cells, expression of paranemin, but not synemin or nestin, led to the formation of an extended desmin network. A similar rescue of desmin network organization was observed when desmin was coexpressed with vimentin, which coassembles with desmin, or with keratins, which formed a distinct filament network. These studies demonstrate that desmin filaments differ in their organizational properties from the other vimentin-like intermediate filament proteins and appear to depend upon coassembly with paranemin, at least when they are expressed in non-muscle cells, in order to form an extended filament network.
波形蛋白、胶质纤维酸性蛋白（GFAP）或外周蛋白的从头表达会导致在无中间丝的SW13/cl.2细胞中组装出一个扩展的中间丝网络。相比之下，结蛋白在SW13/cl.2细胞或无中间丝的小鼠成纤维细胞中均不会形成扩展的丝网络。相反，结蛋白形成短而加粗的丝状结构以及由紧密堆积的直径9 - 11纳米的丝组成的突出的点状细胞质聚集体。对稳定转染细胞系的分析表明，结蛋白无法形成扩展网络并非由于转基因表达水平的差异。巢蛋白、副中间丝蛋白和联丝蛋白是在肌肉细胞中与结蛋白共同组装的大型中间丝蛋白。尽管当这些大型中间丝蛋白在SW - 13细胞中共表达时，它们各自都与结蛋白共定位，但副中间丝蛋白的表达会导致形成扩展的结蛋白网络，而联丝蛋白或巢蛋白的表达则不会。当结蛋白与能与其共同组装的波形蛋白或与形成独特丝网络的角蛋白共表达时，也观察到了结蛋白网络组织的类似拯救现象。这些研究表明，结蛋白丝在组织特性上与其他波形蛋白样中间丝蛋白不同，并且似乎至少在非肌肉细胞中表达时，依赖于与副中间丝蛋白的共同组装才能形成扩展的丝网络。
