Balzar M, Briaire-de Bruijn I H, Rees-Bakker H A, Prins F A, Helfrich W, de Leij L, Riethmüller G, Alberti S, Warnaar S O, Fleuren G J, Litvinov S V
Department of Pathology, Leiden University Medical Center, Leiden, University of Munich, Munich, Germany.
Mol Cell Biol. 2001 Apr;21(7):2570-80. doi: 10.1128/MCB.21.7.2570-2580.2001.
Ep-CAM is a new type of cell adhesion molecule (CAM) which does not structurally resemble the members of the four major families (cadherins, integrins, selectins, and CAMs of the immunoglobulin superfamily) and mediates Ca(2+)-independent, homophilic adhesions. The extracellular domain of Ep-CAM consists of a cysteine-rich region, containing two type II epidermal growth factor (EGF)-like repeats, followed by a cysteine-poor region. We generated mutated Ep-CAM forms with various deletions in the extracellular domain. These deletion mutants, together with monoclonal antibodies recognizing different epitopes in the extracellular domain, were used to investigate the role of the EGF-like repeats in the formation of intercellular contacts mediated by Ep-CAM molecules. We established that both EGF-like repeats are required for the formation of Ep-CAM-mediated homophilic adhesions, including the accumulation of Ep-CAM molecules at the cell-cell boundaries, and the anchorage of the Ep-CAM adhesion complex to F-actin via alpha-actinin. Deletion of either EGF-like repeat was sufficient to inhibit the adhesion properties of the molecule. The first EGF-like repeat of Ep-CAM is required for reciprocal interactions between Ep-CAM molecules on adjacent cells, as was demonstrated with blocking antibodies. The second EGF-like repeat was mainly required for lateral interactions between Ep-CAM molecules. Lateral interactions between Ep-CAM molecules result in the formation of tetramers, which might be the first and necessary step in the formation of Ep-CAM-mediated intercellular contacts.
上皮细胞黏附分子（Ep-CAM）是一种新型细胞黏附分子（CAM），其结构与四大主要家族（钙黏蛋白、整合素、选择素和免疫球蛋白超家族的细胞黏附分子）的成员不同，介导不依赖于Ca(2+)的同型黏附。Ep-CAM的细胞外结构域由一个富含半胱氨酸的区域组成，该区域包含两个II型表皮生长因子（EGF）样重复序列，随后是一个半胱氨酸含量较低的区域。我们构建了细胞外结构域有各种缺失的突变型Ep-CAM形式。这些缺失突变体，连同识别细胞外结构域中不同表位的单克隆抗体，被用于研究EGF样重复序列在由Ep-CAM分子介导的细胞间接触形成中的作用。我们确定，两个EGF样重复序列对于Ep-CAM介导的同型黏附的形成都是必需的，包括Ep-CAM分子在细胞-细胞边界的积累，以及Ep-CAM黏附复合物通过α-辅肌动蛋白与F-肌动蛋白的锚定。删除任何一个EGF样重复序列都足以抑制该分子的黏附特性。如用阻断抗体所证实的，Ep-CAM的第一个EGF样重复序列对于相邻细胞上的Ep-CAM分子之间的相互作用是必需的。第二个EGF样重复序列主要是Ep-CAM分子之间侧向相互作用所必需的。Ep-CAM分子之间的侧向相互作用导致四聚体的形成，这可能是Ep-CAM介导的细胞间接触形成的第一步也是必要步骤。
