FUNCTIONS, STRUCTURE, AND REGULATION OF RECEPTORS FOR CELL ADHESION PROTEINS

细胞与细胞外基质分子通过特异性 受体。 我们已经表征了膜结合分子， 纤连蛋白和胶原蛋白。 生物合成，调节， 纤连蛋白受体的功能进行了表征。 贝塔 发现小鼠和人受体亚基是合成的 作为较小的前体， 涉及天冬酰胺连接的寡糖。 成熟导致 在纤连蛋白结合功能和分泌到 细胞表面。 细胞内的α和β亚基水平 人纤连蛋白受体受转化生长调节 因子B，其诱导合成20- 40倍。 Fibronectin 细胞表面的受体被证明存在于一个 跨膜方向。 它们常常迅速扩散 迁移的胚胎细胞和鸟类或人类肿瘤细胞， 聚集在静止细胞的粘附位点。 这些 分布被证明是独立的受体 磷酸化 纤连蛋白受体的作用显示在 胚胎两栖动物原肠胚形成和人类血小板功能。 抗受体抗体阻断原肠胚形成和血小板生成 与纤连蛋白的粘附。 受体对应血小板 糖蛋白Ic-IIa，并参与非激活性 血小板与含纤连蛋白基质的附着。 一 恶性转化后减少的蛋白质， 具有生物化学特征。 它是一种球形单体， 碱性氨基酸，具有独特的氨基末端36个残基序列 含有一个新的7-mer串联重复序列， 休克蛋白 热休克诱导的mRNA水平，如通过 体外翻译和北方印迹分析。 两个推定 该HSP 47蛋白的连续生物合成前体。 鉴定，两者都具有完全的生物活性， 胶原配体;这种直接的功能与 需要激活纤连蛋白受体。

Cells interact with extracellular matrix molecules by specific receptors. We have characterized membrane binding molecules for fibronectin and collagen. The biosynthesis, regulation, and function of fibronectin receptors were characterized. The beta subunit of mouse and human receptors were found to be synthesized as smaller precursors that required a lengthy maturation period involving asparagine-linked oligosaccharides. Maturation resulted in an activation of fibronectin-binding function and secretion onto the cell surface. Levels of both alpha and beta subunits of the human fibronectin receptor were regulated by transforming growth factor B, which induced synthesis 20- to 40-fold. Fibronectin receptors on the cell surface were shown to exist in a transmembrane orientation. They are often diffuse on rapidly migrating embryonic cells and avian or human tumor cells, but clustered at adhesion sites of stationary cells. These distributions were shown to be independent of receptor phosphorylation. Roles for the fibronectin receptor were shown in embryonic amphibian gastrulation and human platelet function. Antibodies against the receptor blocked gastrulation and platelet adhesion to fibronectin. The receptor corresponds to platelet glycoprotein Ic-IIa, and is involved in activation-independent attachment of platelets to fibronectin-containing substrates. A protein that was decreased after malignant transformation was characterized biochemically. It is a globular monomer enriched in basic amino acids, with a unique amino-terminal 36-residue sequence containing a novel 7-mer tandem repeat unrelated to other heat shock proteins. Heat shock induces levels of mRNA as detected by in vitro translation and Northern blot analysis. Two putative sequential biosynthetic precursors of this hsp47 protein were. identified, both of which were fully biologically active in binding to a collagenous ligand; this immediate functionality contrasts with the requirement for activation of the fibronectin receptor.