STRUCTURE AND ROLE OF A TRANSFORMATION-SENSITIVE CELL SURFACE GLYCOPROTEIN

糖蛋白纤连蛋白在肿瘤细胞上经常减少， 参与细胞粘附和迁移。 它的两种主要形式，称为 血浆和细胞纤维连接蛋白，被证明是非常密切相关的 在一个物种内，但更少的物种之间， 免疫学和肽图谱标准。 这种模式表明， 起源于一个基因而不是一个基因家族。 网站在这些 使用合成的纤维连接蛋白探索与细胞相互作用的纤维连接蛋白。 来自进化保守区域的肽。 序列 Gly-Arg-Gly-Asp-Ser是一个重要的识别信号， 成纤维细胞粘附测定。 变体肽通常表现出少得多的 活性，唯一的例外是短的反向四肽 序列Ser-Asp-Gly-Arg。 纤连蛋白肽也被发现是 功能性体内和显微注射到两栖动物或鸡胚胎中 特异性阻断原肠胚形成和神经嵴细胞迁移。 这些 其他初步实验表明，这些肽也可能 抑制肿瘤细胞迁移和侵袭。 方法直接 用氚标记的荧光标记物， 纤连蛋白和细胞结合片段。 纤连蛋白与细胞结合， 中等亲和力（Kd = 8 × 10-7 M），每个细胞有多达500，000个位点。 合成肽也竞争性抑制纤连蛋白结合到 细胞表面，但具有较低的表观亲和力（Ki = 10 - 3至10 - 10）。 4 M）。 这些结果有力地表明，其他序列信息 除了完全结合所需的关键五肽序列之外 活动 我们未来的目标将是确定 纤连蛋白一级结构除了关键的五肽序列 参与与细胞表面结合，以探索 这种粘附识别信号在各种细胞-基质中的作用， 细胞间粘附系统，尤其是恶性细胞，以及 确定用纤连蛋白合成肽进行体内治疗是否可以 在模型系统中阻止肿瘤细胞侵袭和转移。

The glycoprotein fibronectin is often decreased on tumor cells and is involved in cell adhesion and migration. Its two major forms, termed plasma and cellular fibronectins, were shown to be very closely related structurally within a species, but much less between species, by immunological and peptide mapping criteria. This pattern indicates an origin from a single gene rather than a gene family. The site on these fibronectins that interacts with cells was explored using synthetic peptides from evolutionarily conserved regions. The sequence Gly-Arg-Gly-Asp-Ser was found to be a critical recognition signal in fibroblast adhesion assays. Variant peptides generally showed much less activity, with the sole exception of the short inverted tetrapeptide sequence Ser-Asp-Gly-Arg. Fibronectin peptides were also found to be functional in vivo and microinjection into amphibian or chicken embryos specifically blocked gastrulation and neural crest cell migration. These and other preliminary experiments suggest that these peptides may also inhibit tumor cell migration and invasion. Methods for directly quantitating fibronectin binding by cells were developed using tritiated fibronectin and cell-binding fragments. Fibronectin bound to cells with moderate affinity (Kd = 8 x 10-7 M) with up to 500,000 sites per cell. Synthetic peptides also competitively inhibited fibronectin binding to the cell surface, but with lower apparent affinity (Ki = 10 minus 3 to 10 minus 4 M). These results strongly suggest that other sequence information besides the critical pentapeptide sequence are needed for full binding activity. Our future objectives will be to define the elements of fibronectin primary structure besides the critical pentapeptide sequence that are involved in binding to the cell surface, to explore the generality of this adhesive recognition signal in a variety of cell-to-substrate and cell-to-cell adhesion systems, especially in malignant cells, and to establish whether in vivo treatment with fibronectin synthetic peptides can prevent tumor cell invasion and metastasis in model systems.