Zhang Z, Morla A O, Vuori K, Bauer J S, Juliano R L, Ruoslahti E
Cancer Research Center, La Jolla Cancer Research Foundation, California 92037.
J Cell Biol. 1993 Jul;122(1):235-42. doi: 10.1083/jcb.122.1.235.
The fibronectin receptor, alpha 5 beta 1, has been shown to be required for fibronectin matrix assembly and plays an important role in cell migration on fibronectin. However, it is not clear whether other fibronectin binding integrins can take the place of alpha 5 beta 1 during matrix assembly and cell migration. To test this, we expressed the human alpha v subunit in the CHO cell line CHO-B2 that lacks the alpha 5 subunit. We found that the human alpha v combined with CHO cell beta 1 to form the integrin alpha v beta 1. Cells that expressed alpha v beta 1 attached to and spread well on fibronectin-coated dishes, but did so less well on vitronectin-coated dishes. This, along with other data, indicated that alpha v beta 1 functions as a fibronectin receptor in CHO-B2 cells. The alpha v beta 1-expressing cells failed to produce a fibronectin matrix or to migrate on fibronectin, although the same cells transfected with alpha 5 do produce a matrix and migrate on fibronectin. The affinity of the alpha v beta 1-expressing cells for fibronectin was fourfold lower than that of the alpha 5 beta 1-expressing cells. In addition, alpha v beta 1 was distributed diffusely throughout the cell surface, whereas alpha 5 beta 1 was localized to focal adhesions when cells were seeded onto fibronectin-coated surfaces. Thus, of the two fibronectin receptors, alpha v beta 1 and alpha 5 beta 1, only alpha 5 beta 1 supports fibronectin matrix assembly and promotes cell migration on fibronectin in the CHO-B2 cells. Possible reasons for this difference in the activities of alpha v beta 1 and alpha 5 beta 1 include the lower affinity of alpha v beta 1 for fibronectin and the failure of this integrin to localize in adhesion plaques on a fibronectin substrate. These results show that two integrins with similar ligand specificities and cell attachment functions may be quite different in their ability to support fibronectin matrix assembly and cell motility on fibronectin.
纤连蛋白受体α5β1已被证明是纤连蛋白基质组装所必需的，并且在细胞在纤连蛋白上的迁移中起重要作用。然而，尚不清楚在基质组装和细胞迁移过程中，其他与纤连蛋白结合的整合素是否能够替代α5β1。为了验证这一点，我们在缺乏α5亚基的CHO细胞系CHO-B2中表达了人αv亚基。我们发现人αv与CHO细胞的β1结合形成整合素αvβ1。表达αvβ1的细胞能够附着在纤连蛋白包被的培养皿上并良好铺展，但在玻连蛋白包被的培养皿上则表现较差。这与其他数据表明，αvβ1在CHO-B2细胞中作为纤连蛋白受体发挥作用。尽管转染了α5的相同细胞确实能产生基质并在纤连蛋白上迁移，但表达αvβ1的细胞无法产生纤连蛋白基质或在纤连蛋白上迁移。表达αvβ1的细胞对纤连蛋白的亲和力比表达α5β1的细胞低四倍。此外，当细胞接种到纤连蛋白包被的表面时，αvβ1在整个细胞表面呈弥散分布，而α5β1则定位于粘着斑。因此，在两种纤连蛋白受体αvβ1和α5β1中，只有α5β1支持纤连蛋白基质组装并促进CHO-B2细胞在纤连蛋白上的迁移。αvβ1和α5β1活性存在差异的可能原因包括αvβ1对纤连蛋白的亲和力较低以及该整合素无法定位于纤连蛋白底物上的粘着斑。这些结果表明，两种具有相似配体特异性和细胞附着功能的整合素在支持纤连蛋白基质组装和细胞在纤连蛋白上的运动能力方面可能存在很大差异。
