Role of PI 3-Kinase Isoforms in Insulin Action

项目总结/摘要 这是NIH资助DK 055545的修订竞争性更新，重点是以下方面的作用： 磷脂酰肌醇3-激酶（PI 3 K）在胰岛素作用和胰岛素抵抗中的作用。PI 3-激酶是一个关键节点， 胰岛素的代谢作用。PI 3 K的改变与癌症、糖尿病和许多其他疾病有关。 紊乱在以前的工作中，根据这项赠款，我们已经使用了体外和体内的方法来定义 这种酶在胰岛素作用和胰岛素抵抗中的作用。我们已经表明，PI 3 K的调节取决于 这两个不同的调节亚基的性质;调节和催化之间的化学计量 PI 3-激酶作为下游信号传导发散位点的能力;以及PI 3-激酶的改变。 疾病状态下的PI 3 K活性。我们还发现了PI 3-激酶途径与其他细胞因子之间的新联系。 信号通路，包括p85调节亚基和几种通路之间的重要联系 参与胰岛素抵抗，如激活应激激酶JNK和p38，调节PIP 3 磷酸酶PTEN，以及PI 3-激酶，内质网（ER）应激和未折叠的 p85α和XBP-1 s之间的相互作用产生的蛋白质反应（UPR），促进XBP-1 s转运到 从而改变内质网应激反应。另一个令人兴奋的最新发展是， SHORT综合征（一种以胰岛素为特征的综合征）患者p85α突变的鉴定 抵抗和部分脂肪营养不良。最近，我们已经创造了一个基因敲入小鼠携带这种突变， 研究其在体内的作用。我们还开始描述两个主要催化剂的不同作用， PI 3 K亚基（p110α和p110β）在胰岛素信号转导和线粒体稳态中的作用 体内和体外。这导致了新的假设，不同的催化和调节作用的独特作用， PI 3-激酶的亚基，其允许这些蛋白质充当胰岛素信号传导中的两个分歧位点 生理和病理状态下的正、负调节途径和部位。 在接下来的五年里，我们建议通过定义分子水平来扩展这些观察结果。 和生理水平如何不同的信号产生的p110α和p110β催化亚基PI 3- 激酶，参与的特定信号复合物，以及PI 3 K和线粒体稳态之间的联系。 此外，我们将扩大我们对调节亚基的研究，重点是确定p85α的区域， 与XBP-1相互作用，在PI 3-激酶途径和ER应激之间产生串扰。我们还将进一步 定义p85α调节亚基的突变如何产生显性负效应并导致严重的 胰岛素抵抗总之，这些研究将有助于完成我们对PI 3 K系统作用的理解。 及其在胰岛素作用和胰岛素抵抗中的不同催化和调节亚基。

Project Summary/Abstract This is a revised competitive renewal of NIH grant DK055545 which is focused on the role of phosphatidylinositol 3-kinase (PI3K) in insulin action and insulin resistance. PI 3-kinase is a critical node in insulin's metabolic actions. Alterations in PI3K have been implicated in cancer, diabetes and many other disorders. In previous work under this grant we have used both in vitro and in vivo approaches to define the role of this enzyme in insulin action and insulin resistance. We have shown that regulation of PI3K depends both on the nature of the different regulatory subunits; the stoichiometry between regulatory and catalytic subunits; the ability of PI 3-kinase to serve as a site for divergence of downstream signaling; and alterations in PI3K activity in disease states. We have also identified new links between the PI 3-kinase pathway and other signaling pathways, including important links between the p85 regulatory subunits and several pathways involved in insulin resistance, such as activation of the stress kinases JNK and p38, regulation of the PIP3 phosphatase PTEN, and a novel link between PI 3-kinase, endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) created by the interaction between p85α and XBP-1s, facilitating XBP-1s transport into the nucleus and thus modifying the ER stress response. Another exciting recent development has been the identification of a mutation in p85α in patients with SHORT syndrome, a syndrome characterized by insulin resistance and partial lipodystrophy. Recently, we have created a knock-in mouse bearing this mutation to study its effects in vivo. We have also begun to characterize the different roles of the two major catalytic subunits of PI3K (p110α and p110β) in insulin signaling and mitochondrial homeostasis through knockout in vivo and in vitro. This has led to new hypotheses about the unique roles of the different catalytic and regulatory subunits of PI 3-kinase, which allow these proteins to serve as both sites of divergence in the insulin signaling pathway and sites of positive and negative regulation in physiological and pathological states. In the next five years, we propose to expand upon these observations by defining at both the molecular and physiological levels how different signals are generated by the p110α and p110β catalytic subunits of PI 3- kinase, the specific signaling complexes involved, and the link between PI3K and mitochondrial homeostasis. In addition, we will expand our studies on the regulatory subunits focusing defining the regions of p85α that interact with XBP-1s creating crosstalk between the PI 3-kinase pathway and ER stress. We will also further define how mutations in the p85α regulatory subunit can have a dominant negative effect and result in severe insulin resistance. Together, these studies will help complete our understanding of the role of the PI3K system and its different catalytic and regulatory subunits in insulin action and insulin resistance.