THE ROLE OF THE AKT/PKB SIGNALING IN INSULIN ACTION

II型糖尿病是西方世界最常见的疾病之一，在老年人群中的患病率从10%到50%不等。II型糖尿病的一个组成部分是胰岛素抵抗，即无法达到最大浓度的激素来刺激适当的肌肉葡萄糖运输和其他生理反应。导致新型胰岛素增敏药物开发的一个看似合理的策略是从对胰岛素信号的系统分析开始的。经过20多年对相关丝氨酸/苏氨酸蛋白激酶的深入研究，Akt/PKB已成为胰岛素调节重要代谢靶点的主要候选介体。AKT/PKB已成为胰岛素调节重要代谢靶点的主要候选介体。AKT/PKB是一种普遍存在的丝氨酸/苏氨酸蛋白激酶，其活性依赖于磷脂酰肌醇3‘-激酶的脂类产物，该酶是胰岛素几乎所有代谢活动所必需的。虽然这是一个迅速发展的领域，但目前大量证据表明，Akt/PKB几乎肯定地介导了胰岛素和IGF1‘S效应。大量证据表明，Akt/PKB几乎肯定地介导了胰岛素和IGF1’S的抗细胞凋亡作用，可能参与了胰岛素刺激蛋白质、糖原和甘油三酯的合成，并可能参与了胰岛素激活葡萄糖转运。此外，有确凿的数据表明，Akt/PKB是线虫中胰岛素受体启动的途径中的一个专有中间体。这项研究的主要目标是更仔细地确定Akt/PKB在与生理相关的胰岛素信号中的作用，更详细地了解胰岛素受体和Akt/PKB之间的中间产物，以及后者的激酶和生物输出之间的干预。这些目标将通过两种不同的策略来实现：1)评估在Akt/PKB途径中可疑或牵连的候选蛋白，以及几种新的中间产物的遗传和生化筛选；2)仔细分析培养的小鼠脂肪细胞中的“胰岛素特异性”现象，在这种现象中，Akt/PKB的激活与葡萄糖运输平行。在这里使用的胰岛素特异性是指观察到只有胰岛素，而不是其他生长因子，如PDGF，刺激葡萄糖运输，尽管两组激动剂激活相同的早期信号步骤，具有相同的有效性。预计，通过这些研究，人们将对胰岛素调节基本代谢功能的关键细胞内事件有更深入的了解。

Type II Diabetes Mellitus is one of the most common diseases in the Western world, with prevalence ranging from 10-50% in older populations. An integral component of Type II diabetes mellitus is insulin resistance, i.e. an inability of maximal concentrations of the hormone to stimulate appropriate muscle glucose transport and other physiological response. A plausible strategy leading to the development of novel in insulin-sensitizing drugs begins with the systematic analysis of the insulin signaling. After over 20 years of intensive research in the pursuit of relevant serine/threonine protein kinases, Akt/PKB has emerged as a major candidate mediator of insulin's regulation of important metabolic targets. Akt/PKB has emerged as a major candidate mediator of insulin's regulation of important metabolic targets. Akt/PKB is a fairly ubiquitous serine/threonine protein kinase, whose activity depends on the lipid products of phosphatidylinositol 3'-kinase, an enzyme known to be required for virtually all of the metabolic actions of insulin. Though this a rapidly evolving field, at the present time the bulk of evidence suggests that Akt/PKB almost certainly mediates insulin's and IGF1's effects to time the bok of evidence suggests that Akt/PKB almost certainly mediates insulin's and IGF1's effects to antagonize apoptosis, probably contribute to insulin's stimulation of protein, glycogen and triglyceride synthesis, and possibly is involved in insulin's activation of glucose transport. Moreover, there is definitive data demonstrating that Akt/PKB represents an obligate intermediate in an insulin receptor-initiated pathway in the nematode, C. elegans. The primary goals of the studies describes in this grant proposal are to more carefully define the role of Akt/PKB in physiologically relevant insulin signaling, and to understand in more detail the intermediates both between the insulin receptor and Akt/PKB, as well as intervening between the latter kinase and biological outputs. These goals will be accomplished via two distinct strategies: 1) the evaluation of candidate proteins suspected or implicated in the Akt/PKB pathway, and several genetic and biochemical screens for new intermediates, and 2) a careful analysis of the phenomenon of "insulin specificity" in cultured murine adipocytes, in which activation of Akt/PKB parallels that of glucose transport . Insulin specificity, in the context employed here, refers to the observation that only insulin, but not other growth factors such as PDGF, stimulates glucose transport, in spite of both sets of agonists activating the same early steps in signaling with equal efficacy. It is anticipated that, through these studies, a much deeper understanding will be obtained concerned the critical intracellular events which mediate insulin's regulation of essential metabolic functions.