CARBOHYDRATE OF THE INSULIN RECEPTOR

胰岛素与其受体的结合启动了一系列 对靶细胞的新陈代谢至关重要的反应。 已知的胰岛素受体是一种细胞表面糖蛋白， 根据目前的结构模型由四个部分组成 二硫键连接的亚基(α2β2)与α亚基 包含胰岛素结合部位，而跨膜β- 亚基负责信号转导，可能通过其 酪氨酸激酶活性。该基因的完整氨基酸序列 受体蛋白已被报道基于该基因的DNA克隆 胰岛素受体前体基因，但尽管 碳水化合物构成了分子的重要部分，几乎不是 已知的关于结构和生物学功能的 附着的糖类单位。几项研究表明， 然而，这种碳水化合物可能在 胰岛素受体的生物活性及其转运 细胞表面。 拟议中的实验将检验 存在于分离的α和β亚基上的碳水化合物单位 以及在细胞内的生物合成 先驱物。受体亚基将从人类体内获得 代谢性放射性标记后的淋巴细胞(~3H)氨基葡萄糖 甘露糖)，并将用链霉酶处理以制备糖肽。 碳水化合物单元的详细结构将被确定 通过特定的糖苷酶消化，甲基化分析和 释放和分离N-后的高碘酸盐氧化 和O-连接的糖以及凝集素亲和力 层析法。利用得到的结构信息，它将 可以通过以下方式研究碳水化合物单位的作用 糖类的选择性脱除及其改性的评价 胰岛素结合活性的受体及其结合能力 进行胰岛素刺激的自磷酸化；此外， 碳水化合物参与控制α-和β- 将检查亚基的形成。这些研究将导致 更好地理解碳水化合物在体内的作用 我们对II型糖尿病和胰岛素认识的生物起源 处于抗性状态的活跃细胞表面的数量 受体减少。此外，来自这些网站的信息 研究将是对当前模型的重大补充 并将允许一种合理的方法来研究 研究胰岛素的作用如何依赖于受体结构。

The binding of insulin to its receptor initiates a series of responses which are critical to the metabolism of the target cell. The insulin receptor is known to be a cell surface glycoprotein and according to the current structural model consists of four disulfide linked subunits (alpha 2 beta 2) with the alpha-subunit containing the insulin binding sites while the transmembrane beta- subunit is responsible for signal transduction possibly via its tyrosine kinase activity. The complete amino acid sequence of the receptor protein has been reported based on a DNA clone of the insulin receptor precursor gene, but despite the fact the carbohydrate forms a substantial part of the molecule, little is known in regard to the structure and biological function of the attached saccharide units. Several studies have suggested, however, that carbohydrate may play an important role in the biological activity of the insulin receptor and its transport to the cell surface. The experiments proposed will examine the nature of the carbohydrate units present on the isolated alpha- and beta-subunits of the receptor as well as on its intracellular biosynthetic precursors. The receptor subunits will be obtained from human lymphocytes after metabolic radiolabeling ((3H) glucosamine, (3H) mannose) and will be treated with pronase to prepare glycopeptides. The detail structure of the carbohydrate units will be determined by specific glycosidase digestions, methylation analysis and periodate oxidation subsequent to release and isolation of the N- and O-linked saccharides as well as by lectin affinity chromatography. With the resulting structural information it will be possible to investigate the role of the carbohydrate units by selective removal of the sugars and evaluation of the modified receptor for insulin binding activity and for its ability to undergo insulin-stimulated autophosphorylation; moreover the involvement of carbohydrate in the control of alpha- and beta- subunit formation will be examined. These studies will result in a better understanding of the role of carbohydrate in the biogenesis of our understanding of Type II diabetes and insulin resistant states in which the number of active cell surface receptors is decreased. Furthermore, the information from these studies will represent a significant addition to the current model for the insulin receptor and will allow a logical approach to the study of how insulin action is dependent on receptor structure.