Ozawa M, Ringwald M, Kemler R
Max-Planck-Institut für Immunbiologie, Forschergruppe Molekulare Embryologie, Stübeweg, Freiburg, Federal Republic of Germany.
Proc Natl Acad Sci U S A. 1990 Jun;87(11):4246-50. doi: 10.1073/pnas.87.11.4246.
We have recently found that the cytoplasmic region of the cell adhesion molecule uvomorulin associates with three proteins named catenin alpha, beta, and gamma. Here we show by analysis of various mutant uvomorulin polypeptides expressed in mouse L cells that this association is mediated by a specific domain in the cytoplasmic region. A specific recognition site for catenins is located in a 72-amino acid domain. Interestingly, 69 of the 72 amino acid residues are encoded by a single exon of the uvomorulin gene. To demonstrate the direct interaction between catenins and the 72-amino acid domain, cDNA constructs composed of H-2Kd cDNA and various 3' sequences of uvomorulin were expressed in L cells. Chimeric proteins between H-2Kd and the 72-amino acid domain of uvomorulin were shown, by immunoprecipitation with anti-H-2Kd antibodies, to complex with catenin alpha, beta, and gamma. Catenins connect uvomorulin to cytoskeletal structures. We provide biochemical evidence for an association of the uvomorulin-catenin complex with actin bundles. Our results suggest that catenin alpha plays a key role in the association with actin filaments, whereas catenin beta binds more directly to the cytoplasmic region of uvomorulin. In cell aggregation assays with transfected cells expressing normal or mutant uvomorulin, the adhesive function was expressed only when uvomorulin was associated with catenins. From these results we conclude that the cytoplasmic anchorage of uvomorulin is of major biological importance.
我们最近发现，细胞粘附分子埃-钙粘蛋白的胞质区域与三种名为连环蛋白α、β和γ的蛋白质相关联。在此，我们通过对在小鼠L细胞中表达的各种突变型埃-钙粘蛋白多肽进行分析表明，这种关联是由胞质区域中的一个特定结构域介导的。连环蛋白的一个特异性识别位点位于一个72个氨基酸的结构域中。有趣的是，这72个氨基酸残基中的69个由埃-钙粘蛋白基因的一个外显子编码。为了证明连环蛋白与这个72个氨基酸的结构域之间的直接相互作用，由H-2Kd cDNA和埃-钙粘蛋白的各种3'序列组成的cDNA构建体在L细胞中进行了表达。通过用抗H-2Kd抗体进行免疫沉淀显示，H-2Kd与埃-钙粘蛋白的72个氨基酸结构域之间的嵌合蛋白与连环蛋白α、β和γ形成复合物。连环蛋白将埃-钙粘蛋白连接到细胞骨架结构上。我们提供了生化证据，证明埃-钙粘蛋白-连环蛋白复合物与肌动蛋白束相关联。我们的结果表明，连环蛋白α在与肌动蛋白丝的关联中起关键作用，而连环蛋白β更直接地与埃-钙粘蛋白的胞质区域结合。在用表达正常或突变型埃-钙粘蛋白的转染细胞进行的细胞聚集试验中，只有当埃-钙粘蛋白与连环蛋白相关联时，粘附功能才会表达。从这些结果我们得出结论，埃-钙粘蛋白的胞质锚定具有重要的生物学意义。
