Nagafuchi A, Ishihara S, Tsukita S
Department of Information Physiology, National Institute for Physiological Sciences, Okazaki, Japan.
J Cell Biol. 1994 Oct;127(1):235-45. doi: 10.1083/jcb.127.1.235.
The carboxyl terminus-truncated cadherin (nonfunctional cadherin) has no cell adhesion activity probably because of its failure to associate with cytoplasmic proteins called alpha and beta catenin. To rescue this nonfunctional cadherin as adhesion molecules, we constructed three cDNAs for fusion proteins between nonfunctional E-cadherin and alpha catenin, nE alpha, nE alpha N, and nE alpha C, where the intact, amino-terminal and carboxy-terminal half of alpha catenin, respectively, were directly linked to the nonfunctional E-cadherin, and introduced them into mouse L cells. The subcellular distribution and cell adhesion activity of nE alpha and nE alpha C molecules was similar to those of intact E-cadherin transfectants: they bound to cytoskeletons, were concentrated at cell-cell adhesion sites and showed strong cell adhesion activity. nE alpha N molecules, which also bound to cytoskeletons, showed very poor cell adhesion activity. Taken together, we conclude that in the formation of the cadherin-catenin complex, the mechanical association of alpha catenin, especially its carboxy-terminal half, with E-cadherin is a key step for the cadherin-mediated cell adhesion. Close comparison revealed that the behavior of nE alpha molecules during cytokinesis was quite different from that of intact E-cadherin, and that the intercellular motility, i.e., the cell movement in a confluent sheet, was significantly suppressed in nE alpha transfectants although it was facilitated in E-cadherin transfectants. Considering that nE alpha was not associated with endogenous beta catenin in transfectants, the difference in the nature of cell adhesion between nE alpha and intact E-cadherin transfectants may be explained by the function of beta catenin. The possible functions of beta catenin are discussed with a special reference to its role as a negative regulator for the cadherin-mediated cell adhesion system.
羧基末端截短的钙黏蛋白（无功能的钙黏蛋白）可能由于无法与称为α - 连环蛋白和β - 连环蛋白的细胞质蛋白结合而没有细胞黏附活性。为了将这种无功能的钙黏蛋白挽救为黏附分子，我们构建了三个用于非功能性E - 钙黏蛋白与α - 连环蛋白之间融合蛋白的cDNA，即nEα、nEαN和nEαC，其中α - 连环蛋白的完整、氨基末端和羧基末端的一半分别直接与非功能性E - 钙黏蛋白相连，并将它们导入小鼠L细胞。nEα和nEαC分子的亚细胞分布和细胞黏附活性与完整E - 钙黏蛋白转染细胞相似：它们与细胞骨架结合，集中在细胞 - 细胞黏附位点，并表现出强大的细胞黏附活性。同样与细胞骨架结合的nEαN分子表现出非常差的细胞黏附活性。综上所述，我们得出结论，在钙黏蛋白 - 连环蛋白复合物的形成过程中，α - 连环蛋白，尤其是其羧基末端的一半与E - 钙黏蛋白的机械结合是钙黏蛋白介导的细胞黏附的关键步骤。仔细比较发现，nEα分子在胞质分裂过程中的行为与完整E - 钙黏蛋白有很大不同，并且在nEα转染细胞中，细胞间运动性，即在汇合片层中的细胞运动，显著受到抑制，而在E - 钙黏蛋白转染细胞中则得到促进。考虑到nEα在转染细胞中不与内源性β - 连环蛋白结合，nEα和完整E - 钙黏蛋白转染细胞之间细胞黏附性质的差异可能由β - 连环蛋白的功能来解释。我们特别参考β - 连环蛋白作为钙黏蛋白介导的细胞黏附系统的负调节因子的作用，讨论了β - 连环蛋白的可能功能。
