Fogerty F J, Akiyama S K, Yamada K M, Mosher D F
Department of Medicine, University of Wisconsin, Madison 53706.
J Cell Biol. 1990 Aug;111(2):699-708. doi: 10.1083/jcb.111.2.699.
Fibroblasts have cell surface sites that mediate assembly of plasma and cellular fibronectin into the extracellular matrix. Cell adhesion to fibronectin can be mediated by the interaction of an integrin (alpha 5 beta 1) with the Arg-Gly-Asp-Ser (RGDS)-containing cell adhesion region of fibronectin. We have attempted to elucidate the role of the alpha 5 beta 1 fibronectin receptor in assembly of fibronectin in matrices. Rat monoclonal antibody mAb 13, which recognizes the integrin beta 1 subunit, completely blocked binding and matrix assembly of 125I-fibronectin as well as binding of the 125I-70-kD amino-terminal fragment of fibronectin (70 kD) to fibroblast cell layers. Fab fragments of the anti-beta 1 antibody were also inhibitory. Antibody mAb 16, which recognizes the integrin alpha 5 subunit, partially blocked binding of 125I-fibronectin and 125I-70-kD. When cell layers were coincubated with fluoresceinated fibronectin and either anti-beta 1 or anti-alpha 5, anti-beta 1 was a more effective inhibitor than anti-alpha 5 of binding of labeled fibronectin to the cell layer. Inhibition of 125I-fibronectin binding by anti-beta 1 IgG occurred within 20 min. Inhibition of 125I-fibronectin binding by anti-beta 1 Fab fragments or IgG could not be overcome with increasing concentrations of fibronectin, suggesting that anti-beta 1 and exogenous fibronectin may not compete for the same binding site. No beta 1-containing integrin bound to immobilized 70 kD. These data indicate that the beta 1 subunit plays an important role in binding and assembly of exogenous fibronectin, perhaps by participation in the organization, regeneration, or cycling of the assembly site rather than by a direct interaction with fibronectin.
成纤维细胞具有细胞表面位点，可介导血浆和细胞纤连蛋白组装到细胞外基质中。细胞与纤连蛋白的黏附可通过整合素（α5β1）与纤连蛋白中含精氨酸 - 甘氨酸 - 天冬氨酸 - 丝氨酸（RGDS）的细胞黏附区域的相互作用来介导。我们试图阐明α5β1纤连蛋白受体在纤连蛋白于基质中组装过程中的作用。识别整合素β1亚基的大鼠单克隆抗体mAb 13完全阻断了125I - 纤连蛋白的结合和基质组装，以及纤连蛋白的125I - 70kD氨基末端片段（70kD）与成纤维细胞层的结合。抗β1抗体的Fab片段也具有抑制作用。识别整合素α5亚基的抗体mAb 16部分阻断了125I - 纤连蛋白和125I - 70kD的结合。当细胞层与荧光素标记的纤连蛋白以及抗β1或抗α5抗体共同孵育时，抗β1比抗α5更有效地抑制标记纤连蛋白与细胞层的结合。抗β1 IgG对125I - 纤连蛋白结合的抑制在20分钟内发生。抗β1 Fab片段或IgG对125I - 纤连蛋白结合的抑制不能通过增加纤连蛋白浓度来克服，这表明抗β1和外源性纤连蛋白可能不会竞争相同的结合位点。没有含β1的整合素与固定化的70kD结合。这些数据表明，β1亚基在外源性纤连蛋白的结合和组装中起重要作用，可能是通过参与组装位点的组织、再生或循环，而不是通过与纤连蛋白的直接相互作用。
