A novel role for the integrin-binding III-10 module in fibronectin matrix assembly.
A novel role for the integrin-binding III-10 module in fibronectin matrix assembly.
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DOI：
10.1083/jcb.133.2.431
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发表时间：
1996-04
期刊：
影响因子：
--
通讯作者：
McKeown-Longo PJ
中科院分区：
文献类型：
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作者：
Hocking DC;Smith RK;McKeown-Longo PJ
纤连蛋白基质组装是细胞依赖性过程，其在发育和创伤修复期间的不同时间在组织中上调以支持细胞粘附、迁移和分化的功能。先前的研究已经证明，α 5 β 1整合素和纤连蛋白的氨基末端和III-1模块在纤连蛋白聚合中是重要的。我们最近已经表明纤连蛋白的III-1模块包含纤连蛋白氨基末端的构象敏感结合位点（Hocking，D.C.，J. Sottile和P.J. McKeown-Longo。1994. J.Biol.Chem.269：19183- 19191）。本研究旨在确定α 5 β 1整合素与纤连蛋白聚合之间的关系。固相结合试验，使用重组III-10和III-1模块的人血浆纤连蛋白表明，III-10模块包含一个构象依赖性的结合位点的III-1模块的纤连蛋白。未折叠的III-10可以支持形成含有III-1和氨基末端70 kD片段的三元复合物，表明III-1模块可以支持III-10和70 kD的同时结合。未折叠的III-10和未折叠的III-1都可以支持纤连蛋白结合，但只有III-10可以在没有细胞的情况下促进纤连蛋白的二硫键结合多聚体的形成。III-10依赖性多聚体的形成被抗III-1单克隆抗体9D 2和纤连蛋白的氨基末端片段抑制。III-10的片段，称为III-10/A，能够阻止成纤维细胞单层中的基质组装。使用III-10A/RGE片段获得了类似的结果，其中RGD位点已突变为RGE，表明III-IO/A通过与破坏整联蛋白结合不同的机制阻断基质组装。德克萨斯红偶联的重组III-1，2定位于铺在纤连蛋白或纤连蛋白III-9，10模块上的细胞上的粘着斑的含β 1位点.针对纤连蛋白的III-1或III-9，10模块的单克隆抗体阻断了III-1，2与细胞的结合，而不破坏粘着斑。这些数据表明，α 5 β 1整合素在基质组装中的作用是调节一系列连续的自身相互作用，导致纤连蛋白的聚合。
Fibronectin matrix assembly is a cell-dependent process which is upregulated in tissues at various times during development and wound repair to support the functions of cell adhesion, migration, and differentiation. Previous studies have demonstrated that the alpha 5 beta 1 integrin and fibronectin's amino terminus and III-1 module are important in fibronectin polymerization. We have recently shown that fibronectin's III-1 module contains a conformationally sensitive binding site for fibronectin's amino terminus (Hocking, D.C., J. Sottile, and P.J. McKeown-Longo. 1994. J. Biol. Chem. 269: 19183- 19191). The present study was undertaken to define the relationship between the alpha 5 beta 1 integrin and fibronectin polymerization. Solid phase binding assays using recombinant III-10 and III-1 modules of human plasma fibronectin indicated that the III-10 module contains a conformation-dependent binding site for the III-1 module of fibronectin. Unfolded III-10 could support the formation of a ternary complex containing both III-1 and the amino-terminal 70-kD fragment, suggesting that the III-1 module can support the simultaneous binding of III-10 and 70 kD. Both unfolded III-10 and unfolded III-1 could support fibronectin binding, but only III-10 could promote the formation of disulfide-bonded multimers of fibronectin in the absence of cells. III-10-dependent multimer formation was inhibited by both the anti-III-1 monoclonal antibody, 9D2, and amino-terminal fragments of fibronectin. A fragment of III-10, termed III-10/A, was able to block matrix assembly in fibroblast monolayers. Similar results were obtained using the III-10A/RGE fragment, in which the RGD site had been mutated to RGE, indicating that III-I0/A was blocking matrix assembly by a mechanism distinct from disruption of integrin binding. Texas red- conjugated recombinant III-1,2 localized to beta 1-containing sites of focal adhesions on cells plated on fibronectin or the III-9,10 modules of fibronectin. Monoclonal antibodies against the III-1 or the III-9,10 modules of fibronectin blocked binding of III-1,2 to cells without disrupting focal adhesions. These data suggest that a role of the alpha 5 beta 1 integrin in matrix assembly is to regulate a series of sequential self-interactions which result in the polymerization of fibronectin.