Ayalon O, Sabanai H, Lampugnani M G, Dejana E, Geiger B
Department of Chemical Immunology, Weizmann Institute of Science, Rehovot, Israel.
J Cell Biol. 1994 Jul;126(1):247-58. doi: 10.1083/jcb.126.1.247.
The integrity of the endothelial layer, which lines the entire cavity of the vascular system, depends on tight adhesion of the cells to the underlying basement membrane as well as to each other. It has been previously shown that such interactions occur via membrane receptors that determine the specificity, topology, and mechanical properties of the surface adhesion. Cell-cell junctions between endothelial cells, in culture and in situ, involve both Ca(2+)-dependent and -independent mechanisms that are mediated by distinct adhesion molecules. Ca(2+)-dependent cell-cell adhesion occurs mostly via members of the cadherin family, which locally anchor the microfilament system to the plasma membrane, in adherens junctions. Ca(2+)-independent adhesions were reported to mainly involve members of the Ig superfamily. In this study, we performed three-dimensional microscopic analysis of the relative subcellular distributions of these two endothelial intercellular adhesion systems. We show that cadherins are located at adjacent (usually more apical), yet clearly distinct domains of the lateral plasma membrane, compared to PECAM-1. Moreover, cadherins were first organized in adherens junctions within 2 h after seeding of endothelial cells, forming multiple lateral patches which developed into an extensive belt-like structure over a period of 24 h. PECAM-1 became associated with surface adhesions significantly later and became progressively associated with the cadherin-containing adhesions. Cadherins and PECAM-1 also differed in their detergent extractability, reflecting differences in their mode of association with the cytoskeleton. Moreover, the two adhesion systems could be differentially modulated since short treatment with the Ca2+ chelator EGTA, disrupted the cadherin junctions leaving PECAM-1 apparently intact. These results confirm that endothelial cells possess distinct intercellular contact mechanisms that differ in their spatial and temporal organization as well as in their functional properties.
内皮细胞层覆盖着整个血管系统腔，其完整性取决于细胞与下方基底膜以及彼此之间的紧密黏附。先前的研究表明，这种相互作用是通过膜受体发生的，这些受体决定了表面黏附的特异性、拓扑结构和机械特性。在培养和原位状态下，内皮细胞之间的细胞间连接涉及由不同黏附分子介导的钙依赖性和非钙依赖性机制。钙依赖性细胞间黏附主要通过钙黏蛋白家族成员发生，这些成员在黏附连接中将微丝系统局部锚定到质膜上。据报道，非钙依赖性黏附主要涉及免疫球蛋白超家族成员。在本研究中，我们对这两种内皮细胞间黏附系统的相对亚细胞分布进行了三维显微镜分析。我们发现，与血小板内皮细胞黏附分子-1（PECAM-1）相比，钙黏蛋白位于相邻（通常更靠近顶端）但明显不同的外侧质膜区域。此外，在内皮细胞接种后2小时内，钙黏蛋白首先在黏附连接中组织起来，形成多个外侧斑块，并在24小时内发展成广泛的带状结构。PECAM-1与表面黏附的关联明显较晚，并逐渐与含钙黏蛋白的黏附相关联。钙黏蛋白和PECAM-1在去污剂提取能力方面也有所不同，这反映了它们与细胞骨架关联方式的差异。此外，这两种黏附系统可以受到不同的调节，因为用钙离子螯合剂乙二醇双四乙酸（EGTA）进行短时间处理会破坏钙黏蛋白连接，而PECAM-1显然保持完整。这些结果证实，内皮细胞具有不同的细胞间接触机制，它们在空间和时间组织以及功能特性方面存在差异。
