Peñas P F, García-Díez A, Sánchez-Madrid F, Yáñez-Mó M
Departments of Dermatology and Immunology, Hospital Universitario de La Princesa, Universidad Autónoma de Madrid, Spain.
J Invest Dermatol. 2000 Jun;114(6):1126-35. doi: 10.1046/j.1523-1747.2000.00998.x.
We have described previously that beta1 integrins, which mediate keratinocyte cell adhesion and migration, are in ligand-occupied conformation at the basal surface but not at the lateral and apical surfaces of keratinocytes. This led us to study the cellular localization and function of tetraspanin molecules, which have been postulated to modulate integrin activity. We found that CD9 and CD81 are highly expressed by keratinocytes clearly delineating filopodia at lateral and apical surfaces. CD63 and CD151 are largely expressed in the intracellular compartment, although some membrane expression is observed. We found accumulation of CD9, CD81, and CD151 together with alpha3 and beta1 integrins at intercellular junctions. In low calcium medium, this intercellular space is crossed by a zipper of filopodia enriched in alpha3beta1 and tetraspanin proteins. Interestingly, the expression of CD9, CD81, and beta1 and alpha3 integrins was detected in the footprints and rippings of motile keratinocytes, suggesting their role in both adhesion to extracellular matrix and keratinocyte motility. beta1 integrins were only partially activated in the rips, whereas cytoskeleton-linking proteins such as talin were completely absent. On the other hand, antitetraspanin antibodies did not stain focal adhesions, which contain talin. The involvement of tetraspanins in keratinocyte motility was assessed in a wound healing migration assay. Inhibition of cell migration was observed with antibodies to CD9, CD81, beta1, and alpha3, and, to a lesser extent, to CD151. Together these results indicate that tetraspanin-integrin complexes might be involved in transient adhesion and integrin recycling during keratinocyte migration, as well as in intercellular recognition.
我们之前曾描述过，介导角质形成细胞黏附和迁移的β1整合素在角质形成细胞的基底表面呈配体占据构象，而在其侧面和顶面则不然。这促使我们研究四跨膜蛋白分子的细胞定位和功能，据推测这些分子可调节整合素活性。我们发现角质形成细胞高表达CD9和CD81，它们清晰勾勒出侧面和顶面的丝状伪足。CD63和CD151主要在细胞内区室表达，不过也观察到了一些膜表达。我们发现在细胞间连接处有CD9、CD81和CD151与α3和β1整合素的聚集。在低钙培养基中，这个细胞间空间被富含α3β1和四跨膜蛋白的丝状伪足拉链穿过。有趣的是，在运动角质形成细胞的足迹和撕脱处检测到了CD9、CD81以及β1和α3整合素的表达，表明它们在与细胞外基质黏附以及角质形成细胞运动中都发挥作用。β1整合素在撕脱处仅部分被激活，而诸如踝蛋白等细胞骨架连接蛋白则完全缺失。另一方面，抗四跨膜蛋白抗体不会使含有踝蛋白的粘着斑染色。通过伤口愈合迁移实验评估了四跨膜蛋白在角质形成细胞运动中的作用。用针对CD9、CD81、β1和α3的抗体观察到了细胞迁移的抑制，对CD151的抑制作用较小。这些结果共同表明，四跨膜蛋白 - 整合素复合物可能参与角质形成细胞迁移过程中的瞬时黏附、整合素循环以及细胞间识别。
