Nagafuchi A, Takeichi M
Department of Biophysics, Faculty of Science, Kyoto University, Japan.
EMBO J. 1988 Dec 1;7(12):3679-84. doi: 10.1002/j.1460-2075.1988.tb03249.x.
Cadherins are a family of transmembrane glycoproteins responsible for Ca2+-dependent cell-cell adhesion. Their amino acid sequences are highly conserved in the cytoplasmic domain. To study the role of the cytoplasmic domain in the function of cadherins, we constructed expression vectors with cDNAs encoding the deletion mutants of E-cadherin polypeptides, in which the carboxy terminus was truncated at various lengths. These vectors were introduced into L cells by transfection, and cell lines expressing the mutant E-cadherin molecules were isolated. In all transfectants obtained, the extracellular domain of the mutant E-cadherins was exposed on the cell surface, and had normal Ca2+-sensitivity and molecular size. However, these cells did not show any Ca2+-dependent aggregation, indicating that the mutant molecules cannot mediate cell-cell binding. The mutant E-cadherin molecules could be released from cells by nonionic detergents, whereas a fraction of normal E-cadherin molecules could not be extracted with the detergent and appeared to be anchored to the cytoskeleton at cell-cell junctions. These results suggest that the cytoplasmic domain regulates the cell-cell binding function of the extracellular domain of E-cadherin, possibly through interaction with some cytoskeletal components.
钙黏蛋白是一类跨膜糖蛋白，负责钙离子依赖的细胞间黏附。它们的氨基酸序列在细胞质结构域中高度保守。为了研究细胞质结构域在钙黏蛋白功能中的作用，我们构建了表达载体，其含有编码E-钙黏蛋白多肽缺失突变体的cDNA，其中羧基末端被截短至不同长度。通过转染将这些载体导入L细胞，并分离出表达突变型E-钙黏蛋白分子的细胞系。在所有获得的转染细胞中，突变型E-钙黏蛋白的细胞外结构域暴露在细胞表面，并且具有正常的钙离子敏感性和分子大小。然而，这些细胞未表现出任何钙离子依赖的聚集，表明突变分子不能介导细胞间结合。突变型E-钙黏蛋白分子可被非离子去污剂从细胞中释放出来，而一部分正常的E-钙黏蛋白分子不能被该去污剂提取，似乎在细胞间连接处锚定在细胞骨架上。这些结果表明，细胞质结构域可能通过与某些细胞骨架成分相互作用来调节E-钙黏蛋白细胞外结构域的细胞间结合功能。
