Effects of Mutant Keratin Genes in Transfected Epidermal Cells : Establishment of Cell Models for Genodermatoses

为了确定分化特异性角蛋白丝组装所需的相互作用，将小鼠毛发角蛋白mHa1和mHb4基因的活性拷贝导入大鼠袋鼠肾上皮细胞系（PtK2）和大鼠分层鳞状上皮细胞系（大鼠表皮角化细胞）。在PtK2瞬时转染中，当单独或联合引入时，mHa1和mHb4在核周区域形成不同大小的环状结构聚集体，没有证据表明它们组织成角蛋白网络。这些聚集体改变了内源性角蛋白和波形蛋白的分布。在大多数细胞核周围携带mHa1和mHb4环状结构的细胞中，内源性角蛋白网络崩溃并定位于细胞核周围。此外，密集积累的内源性角蛋白围绕环状聚集体部分共定位。然而，当转染到大鼠表皮角质形成细胞时，mHa1和mHb4能够与内源性角蛋白发育良好的细胞骨架共定位。这些结果表明，与角蛋白对K5/K14和K8/K18相比，mHa1/mHb4对本身无法形成广泛的角蛋白网络，这些毛发角蛋白与其他角蛋白之间可能存在形成发育良好的细胞质网络的差异能力。

To define the interactions required for the filament assembly of differentiation-specific keratins, active copies of mouse hair keratin mHa1 and mHb4 genes were introduced into a rat kangaroo kidney epithelial cell line (PtK2) and a rat stratified squamous epithelial cell line (rat epidermal keratinocyte). In PtK2 transient transfectants when introduced individually or in combination, mHa1 and mHb4 formed aggregates of ring-like structures of various sizes at the perinuclear region with no evidence of organization into a keratin network. These aggregates altered the distribution of the endogenous keratins and vimentin. In most of the cells carrying the ring-like structures of mHa1 and mHb4 around the nucleus, the endogenous keratin network collapsed and localized around the nucleus. Furthermore, the densely accumulated endogenous keratin surrounded the ring-like aggregates with partial co-localization. However, when transfected into the rat epidermal keratinocytes, mHa1 and mHb4 were able to co-localize with the well-developed cytoskeleton of endogenous keratins. These results showed that, in contrast to keratin pairs K5/K14 and K8/K18, the mHa1/mHb4 pair is unable to develop an extensive keratin network on its own, and that there are possible differential abilities among these hair keratins and other keratins to form well-developed cytoplasmic networks.