STRUCTURE AND ROLE OF A TRANSFORMATION-SENSITIVE CELL SURFACE GLYCOPROTEIN

纤维连接蛋白是主要的细胞表面和细胞外基质 参与细胞粘附和迁移的糖蛋白。 合成 对衍生自其序列的肽抑制剂进行了检测， 对各种粘合系统的影响。 五肽Gly- Arg-Gly-Asp-Ser（GRGDS）是抗肿瘤作用最强的多肽。 纤连蛋白介导的粘附，相关序列是活跃的 对于玻连蛋白。 这些肽对层粘连蛋白几乎没有活性， 胶原蛋白或细胞-细胞粘附，表明特异性。 一个 人工反向肽鉴定了一种可能的共同点， 这五个系统中的四个系统的功能分母。 GRGDS 抑制小鼠B16黑色素瘤细胞的实验性转移 如通过肺定殖测量的，以及相对活性 与抑制细胞粘附的类似物密切匹配 体外 肽治疗也大大延长了生存期 这些动物。 增加肽的几种策略 体外和体内有效性正在研究中。 这 五肽粘附识别序列似乎也 在果蝇原肠胚形成和脊椎动物体节中的作用 体节前体细胞表现为诱导的细胞-细胞 粘连 全亲和力结合所需的额外区域 细胞表面（50至100倍扩增）的定义 通过重组DNA表达研究。 大纤维连接蛋白 在E. coli as λ gt 11融合蛋白 保留了超过80%的粘附活性;真核后- 因此不需要翻译修饰。 删除 诱变实验表明，第二个位点至少 距离GRGDS位点20 kD。 另一类小说，细胞- 型特异性结合位点被发现在其他地方， 纤维连接蛋白的可变剪接调控位点。 合成 来自一个位点的肽的活性仅为完整肽的2.4倍 纤连蛋白。 关键氨基酸序列和生物活性 这些新区域在细胞迁移和转移中的功能 将被确定。

Fibronectin is a major cell surface and extracellular matrix glycoprotein involved in cell adhesion and migration. Synthetic peptide inhibitors derived from its sequence were examined for effects on a variety of adhesion systems. The pentapeptide Gly- Arg-Gly-Asp-Ser (GRGDS) was the most effective peptide against fibronectin-mediated adhesion, and a related sequence was active for vitronectin. Such peptides had little activity on laminin, collagen, or cell-cell adhesion, indicating specificity. An artificial inverted peptide identified a possible common denominator of function in four of these five systems. GRGDS inhibited experimental metastasis of B16 melanoma cells in mice as measured by pulmonary colonization, and the relative activities of analogues closely matched those for inhibition of cell adhesion in vitro. Peptide treatment also substantially prolonged survival of these animals. Several strategies to increase peptide effectiveness in vitro and in vivo are under investigation. This pentapeptide adhesive recognition sequence also appears to function in Drosophila gastrulation and in vertebrate somite formation; somite precursor cells showed induced cell-cell adhesion. An additional region required for full-affinity binding to the cell surface (50- to 100-fold augmentation) is being defined by recombinant DNA expression studies. Large fibronectin fragments expressed in E. coli as lambda gt11 fusion proteins retained greater than 80% adhesive activity; eukaryotic post- translational modifications were thus not needed. Deletion mutagenesis experiments show that the second site is at least 20kD away from the GRGDS site. A separate class of novel, cell- type specific binding sites were discovered elsewhere in fibronectin at sites regulated by alternative splicing. A synthetic peptide from one site was only 2.4-fold less active than intact fibronectin. The critical amino acid sequences and the biological functions of these novel regions in cell migration and metastasis will be determined.