Mueller H, Franke W W
J Mol Biol. 1983 Feb 5;163(4):647-71. doi: 10.1016/0022-2836(83)90116-x.
Epithelial cells contain complexes of cytokeratin filaments (tonofilaments) with specific domains of the plasma membrane that appear as symmetric junctions, i.e. desmosomes, or as asymmetric hemi-desmosomes. These regions of filament-membrane-attachment are characterized by 14 to 20 nm thick dense plaques (desmosomal plaque). In isolated desmosome-tonofilament complexes or other desmosomal fractions from various stratified squamous epithelia (e.g. bovine muzzle epidermis and tongue mucosa) desmosomal plaque structures are recognized and show a relatively high resistance to various extraction buffers and detergents. Such fractions enriched in desmosomal plaque material are also enriched in two prominent polypeptide bands of apparent molecular weights 250,000 (desmoplakin I) and 215,000 (desmoplakin II) which appear, on two-dimensional gel electrophoresis, as two distinct polypeptides isoelectric near neutral pH. These two polypeptides are present in almost equimolar amounts and each of them appears as a series of isoelectric variants, including some labeled by [32P]phosphate in tissue slices. The two desmoplakin polypeptides are closely related as shown by tryptic peptide map analysis and are different from keratin-like proteins and other major polypeptides of desmosome-rich fractions. Guinea pig antibodies raised against desmoplakins and specific for these proteins do not cross-react with other desmosomal antigen(s) or constituents of other types of junctions. Using desmoplakin antibodies we have identified desmoplakins as the major constituents of the desmosomal plaques present in epithelial and myocardiac cells of diverse species. The significance of this group of cell type-specific membrane-associated cytoskeletal proteins and their possible cytoskeletal functions are discussed.
上皮细胞含有细胞角蛋白丝（张力丝）与质膜特定结构域的复合体，这些复合体表现为对称连接，即桥粒，或不对称半桥粒。这些丝与膜附着的区域以14至20纳米厚的致密斑（桥粒斑）为特征。在从各种复层鳞状上皮（如牛口鼻表皮和舌黏膜）分离出的桥粒 - 张力丝复合体或其他桥粒组分中，桥粒斑结构可被识别，并且对各种提取缓冲液和去污剂表现出相对较高的抗性。富含桥粒斑物质的这些组分还富含两条明显的多肽带，其表观分子量分别为250,000（桥粒斑蛋白I）和215,000（桥粒斑蛋白II），在二维凝胶电泳上，它们表现为在中性pH附近等电的两条不同多肽。这两种多肽几乎以等摩尔量存在，并且它们各自都表现为一系列等电变体，包括在组织切片中被[32P]磷酸盐标记的一些变体。如胰蛋白酶肽图谱分析所示，这两种桥粒斑蛋白多肽密切相关，并且与角蛋白样蛋白和富含桥粒组分的其他主要多肽不同。针对桥粒斑蛋白产生的豚鼠抗体对这些蛋白质具有特异性，不会与其他桥粒抗原或其他类型连接的成分发生交叉反应。使用桥粒斑蛋白抗体，我们已确定桥粒斑蛋白是存在于不同物种上皮细胞和心肌细胞中的桥粒斑的主要成分。本文讨论了这组细胞类型特异性膜相关细胞骨架蛋白的意义及其可能的细胞骨架功能。
