INTERCADHERIN INTERACTIONS IN EPITHELIAL CELLS

E-钙粘蛋白属于经典钙粘蛋白的多基因家族，其在称为粘附连接的特化细胞间连接中充当结构性跨膜元件。基于E-钙粘蛋白的粘附对于上皮组织的正常发育和维持至关重要。尽管它们的重要性，但是，很少有人知道的分子机制参与这些路口的组装。目前的建议是基于我们的发现，即E-钙粘蛋白可以自缔合形成暴露在细胞表面上的三种不同的复合物。其中两个复合物，横向复合物，其中E-钙粘蛋白分子形成二聚体通过残基Trp 156（Trp 156依赖性横向复合物），和反平行（粘合剂）复合物已被预测的晶体学分析。第三个复杂的确定是横向Trp 156独立的复杂。它是由培养基中细胞外Ca 2+离子的耗尽引发的。重要的是，只有粘附复合物的形成依赖于细胞质E-钙粘蛋白结构域。此外，表皮生长因子（EGF）强烈增加这些复合物的量。这三种不同的复合物可能代表了粘附连接组装中的连续步骤。因此，本提案的主要目标是评估这一假设。为此，我们将研究这些复合物中的每一个对粘附连接组装的贡献。将评估横向Trp 156依赖性复合物和连环蛋白在粘附复合物形成中的作用。我们将确定哪些决定因素的E-钙粘蛋白参与Trp 156独立的相互作用。此外，我们计划检查是否由点突变，或由特定的肽，这一决定因素的失活，影响集群的粘附复合物成adherens连接。该提案的最后一部分集中在了解EGF对粘合剂复合物形成的影响。在这个建议中描述的实验将进一步我们的上皮形态发生的分子机制的理解。

E-cadherin belongs to a multigene family of classic cadherins that serve as structural transmembrane elements in specialized intercellular junctions termed adherens junctions. E-cadherin-based adhesion is critical for normal development and maintenance of epithelial tissue. Despite their importance, however, little is known about the molecular mechanisms involved in the assembly of these junctions. The present proposal is based on our finding that E-cadherin can self- associate to form three distinct complexes exposed on the cell surface. Two of these complexes, the lateral complex in which E-cadherin molecules form dimers via residue Trp156 (Trp156-dependent lateral complex), and the antiparallel (adhesive) complex have been predicted by crystallographic analysis. The third complex identified is the lateral Trp156-independent complex. It is triggered by a depletion of extracellular Ca2+ ions from culture medium. Importantly, only the formation of adhesive complexes depends on cytoplasmic E-cadherin domain. Furthermore, epidermal growth factor (EGF) strongly increases the amount of these complexes. It is likely that the three distinct complexes represent consecutive steps in adherens junction assembly. The broad goal then, of the present proposal is to evaluate this hypothesis. To this end, we will study the contribution of each of these complexes to adherens junction assembly. The role of the lateral Trp156-dependent complexes and catenins in the formation of the adhesive complexes will be evaluated. We will identify which determinant of E-cadherin is involved in Trp156- independent interactions. Also, we plan to examine whether inactivation of this determinant by point mutations, or by specific peptides, affects clustering of the adhesive complexes into adherens junctions. The final part of the proposal is focused on understanding the effect of EGF on the adhesive complex formation. The experiments described in this proposal will further our understanding of the molecular mechanisms responsible for epithelial morphogenesis.