Nagafuchi A, Takeichi M
Department of Biophysics, Faculty of Science, Kyoto University, Japan.
Cell Regul. 1989 Nov;1(1):37-44. doi: 10.1091/mbc.1.1.37.
Cadherins are a family of transmembrane glycoproteins which play a key role in Ca(2+)-dependent cell-cell adhesion. Cytoplasmic domains of these molecules are anchored to the cell cytoskeleton and are required for cadherin function. To elucidate how the function of cadherins is controlled through their cytoplasmic domains, we deleted five different regions in the cytoplasmic domain of E-cadherin. After transfecting L cells with cDNA encoding the mutant polypeptides, we assayed aggregating activity of these transfectants; all these mutant proteins were shown to have an extracellular domain with normal Ca(2+)-sensitivity and molecular weight. Two mutant polypeptides with deletions in the carboxy half of the cytoplasmic domain, however, did not promote cell-cell adhesion and had also lost the ability to bind to the cytoskeleton, whereas the mutant molecules with deletions of other regions retained the ability to promote cell adhesion and to anchor to the cytoskeleton. Thus, the cytoplasmic domain contains a subdomain which was involved in the cell adhesion and cytoskeleton-binding functions. When E-cadherin in F9 cells or in L cells transfected with wild-type or functional mutant cadherin polypeptides was solubilized with nonionic detergents and immunoprecipitated, two additional 94 and 102 kDa components were coprecipitated. The 94 kDa component, however, was not detected in the immunoprecipitates from cells expressing the mutant cadherins which had lost the adhesive function. These results suggest that the interaction of the carboxy half of the cytoplasmic domain with the 94 kDa component regulates the cell binding function of the extracellular domain of E-cadherin.
钙黏着蛋白是一类跨膜糖蛋白家族，在钙离子依赖的细胞间黏附中起关键作用。这些分子的胞质结构域锚定在细胞骨架上，是钙黏着蛋白功能所必需的。为了阐明钙黏着蛋白的功能是如何通过其胞质结构域来控制的，我们删除了E-钙黏着蛋白胞质结构域中的五个不同区域。在用编码突变多肽的cDNA转染L细胞后，我们检测了这些转染细胞的聚集活性；所有这些突变蛋白都显示具有一个具有正常钙离子敏感性和分子量的细胞外结构域。然而，在胞质结构域羧基端一半有缺失的两个突变多肽，既不促进细胞间黏附，也失去了与细胞骨架结合的能力，而其他区域有缺失的突变分子则保留了促进细胞黏附和锚定到细胞骨架的能力。因此，胞质结构域包含一个参与细胞黏附和细胞骨架结合功能的亚结构域。当用非离子去污剂溶解F9细胞或用野生型或功能性突变钙黏着蛋白多肽转染的L细胞中的E-钙黏着蛋白并进行免疫沉淀时，另外两个94 kDa和102 kDa的成分也被共沉淀。然而，在表达失去黏附功能的突变钙黏着蛋白的细胞的免疫沉淀产物中未检测到94 kDa的成分。这些结果表明，胞质结构域羧基端一半与94 kDa成分的相互作用调节了E-钙黏着蛋白细胞外结构域的细胞结合功能。
