Cadherin transmembrane proteins are responsible for intercellular adhesion in all biological tissues and modulate tissue morphogenesis, cell motility, force transduction, and macromolecular transport. The protein-mediated adhesions consist of adhesive trans interactions and lateral cis interactions. Although theory suggests cooperativity between cis and trans bonds, direct experimental evidence of such cooperativity has not been demonstrated. Here, the use of superresolution microscopy, in conjunction with intermolecular single-molecule Förster resonance energy transfer, demonstrated the mutual cooperativity of cis and trans interactions. Results further demonstrate the consequent assembly of large intermembrane junctions, using a biomimetic lipid bilayer cell adhesion model. Notably, the presence of cis interactions resulted in a nearly 30-fold increase in trans-binding lifetimes between epithelial-cadherin extracellular domains. In turn, the presence of trans interactions increased the lifetime of cis bonds. Importantly, comparison of trans-binding lifetimes of small and large cadherin clusters suggests that this cooperativity is primarily due to allostery. The direct quantitative demonstration of strong mutual cooperativity between cis and trans interactions at intermembrane adhesions provides insights into the long-standing controversy of how weak cis and trans interactions act in concert to create strong macroscopic cell adhesions.

钙粘蛋白跨膜蛋白负责所有生物组织中的细胞间粘附并调节组织形态发生、细胞运动、力转导和大分子转运。蛋白质介导的粘附包括粘附反式相互作用和横向顺式相互作用。尽管理论表明顺式和反式键之间存在协同性，但尚未证明这种协同性的直接实验证据。在这里，超分辨率显微镜的使用，结合分子间单分子 Förster 共振能量转移，证明了顺式和反式相互作用的相互协同性。结果进一步证明了大膜间连接的后续组装，使用仿生脂质双层细胞粘附模型。尤其，顺式相互作用的存在导致上皮-钙粘蛋白胞外域之间的反式结合寿命增加了近 30 倍。反过来，反式相互作用的存在增加了顺式键的寿命。重要的是，大小钙粘蛋白簇的反式结合寿命的比较表明这种协同作用主要是由于变构。在膜间粘连中顺式和反式相互作用之间强相互作用的直接定量证明提供了对弱顺式和反式相互作用如何协同作用以产生强大的宏观细胞粘附的长期争议的见解。小型和大型钙粘蛋白簇的反式结合寿命的比较表明这种协同作用主要是由于变构。在膜间粘连中顺式和反式相互作用之间强相互作用的直接定量证明提供了对弱顺式和反式相互作用如何协同作用以产生强大的宏观细胞粘附的长期争议的见解。小型和大型钙粘蛋白簇的反式结合寿命的比较表明这种协同作用主要是由于变构。在膜间粘连中顺式和反式相互作用之间强相互作用的直接定量证明提供了对弱顺式和反式相互作用如何协同作用以产生强大的宏观细胞粘附的长期争议的见解。