SEMISYNTHETIC IGF-I/INSULIN HYBRIDS AS RECEPTOR PROBES

该提案的长期目标涉及：（a）确定 胰岛素样生长因子I（IGF-I）的结构属性， 确定其与I型IGF受体相互作用的效力， （B）评价以下发展： 可能适用于亲和力的不同决定因素的规则， 在结构上相关的基团内的受体相互作用的选择性 配体和受体，以及（c）考虑开发 可能具有治疗或实验价值的IGF-I类似物。 该项目的具体目标概述如下： 制备具有选定结构变化的杂合IGF-I/胰岛素类似物， 通过化学肽合成和半合成进行氨基酸置换。 (b)为了评价这些类似物的效力， 通过结合I型IGF和胰岛素受体的能力 竞争研究和放射性标记配体结合的直接分析。（c）第（1）款 考虑受体位点亲和力和选择性的不同问题 与IGF-I和胰岛素系统相关， 与两种受体的相互作用。(d)为了解决潜在的 用光谱方法研究类似物溶液结构的差异 和化学修饰。(e)为了评估结构性的后果， 这些类似物的变化与其生物活性有关， 体外，通过使用3 H-胸苷掺入DNA和 额外的代谢反应。(f)为了评估潜在的生物学 在配体相互作用中结合位点异质性的影响 I型IGF受体相关结合动力学分析 问题研究(g)了解I型IGF受体 通过使用化学和亲和性， 方法. 由于IGF-I生理学的异常可能导致 在不同的情况下，无论是不适当的低， 不适当的高组织生长速率，并且由于IGF-I系统可以 可用于在胰岛素抵抗状态下绕过胰岛素系统， 不难想象， IGF-I的类似物，其可能（a）对IGF-I的一种或另一种具有选择性， 作用，（B）甚至比天然激素更有效，（c）抑制 通过与受体结合而不诱导细胞内分泌， 反应，或（d）通过多个受体系统产生所需的 代谢效应 该提案代表了IGF-I系统的研究， 一个基本的水平，在这个阶段，和应用的方法， 化学多肽合成与半合成相关的阐明 结构-功能关系。

This proposal has long-term goals related to (a) identifying the structural attributes of insulin-like growth factor I (IGF-I) which determine its potency for interactions with type I IGF receptors, and its consequent overall biological effects, (b) evaluating the development of rules that might apply to the separate determinants of affinity and selectivity for receptor interactions within structurally related groups of ligands and receptors, and (c) considering the potential for development of IGF-I analogs that might be of therapeutic or experimental value. Specific aims for the project are summarized as follows: (a) To prepare hybrid IGF-I/insulin analogs with selected structural changes and amino acid replacements by chemical peptide synthesis and semisynthesis. (b) To evaluate the potencies of these analogs with regard to their abilities to bind to the type I IGF and insulin receptors through binding competition studies and direct analysis of radiolabeled ligand binding. (c) To consider the separate issues of receptor site affinity and selectivity in relation to the IGF-I and insulin systems through comparisons of analog interactions with both receptors. (d) To address aspects of potential differences in the solution structures of analogs by spectroscopic methods and chemical modification. (e) To evaluate the consequences of structural changes in these analogs in relation to their biological activities in vitro, by use of assays for 3H-thymidine incorporation into DNA and for additional metabolic responses. (f) To evaluate the potential biological implications of binding site heterogeneity in ligand interactions with the type I IGF receptor through the kinetic analysis of related binding studies. (g) To approach an understanding of type I IGF receptor heterogeneity at the molecular level through use of chemical and affinity methods. As aberrations in IGF-I physiology can be expected to result under different sets of circumstances in either inappropriately low or inappropriately high rates of tissue growth, and as the IGF-I system could be useful in by-passing the insulin system in states of insulin resistance, it is not difficult to envision the potential health-related importance of analogs of IGF-I that might (a) be selective for one or the other of its actions, (b) be even more potent than the natural hormone, (c) inhibit the action endogenous hormone by binding to receptor without inducing cellular responses, or (d) act through multiple receptor systems to produce desired metabolic effects. This proposal represents a study of the IGF-I system at a fundamental level, at this stage, and the application of the methods of chemical peptide synthesis and semisynthesis to the elucidation of relevant structure-function relationships.