Role of PI 3-Kinase isoforms in insulin action

描述（由申请人提供）：这是NIH资助DK 55545的竞争性更新，重点是PI 3-激酶在胰岛素作用中的作用。PI 3-激酶是胰岛素代谢调控中的关键节点，也是胰岛素信号传导分歧的关键点。在先前的工作下，该授权使用在体外和体内的方法，包括创建和表征小鼠和细胞系中的PI 3-激酶的调节和催化亚基的特定亚型已被删除，我们已经证明，这种酶控制胰岛素信号在积极和消极的方式，并参与远远超过简单的生成PIP 3。这包括PI 3-激酶的不同调节亚基（p85）和催化亚基（p110）的活性和性质的差异;调节亚基和催化亚基之间的化学计量对胰岛素作用的重要影响; PI 3-激酶允许Akt和非典型PKC之间下游信号发散的能力;以及疾病状态下PI 3-激酶活性的改变。此外，我们已经确定了PI 3-激酶途径和其他信号途径之间的一些以前未被认识的联系，包括支持下游胰岛素作用的p110 a和p110 b催化亚基之间的差异，以及p85调节亚基和参与胰岛素抵抗的几种途径之间的重要联系，包括应激激酶JNK和p38;细胞和组织中主要的PIP 3磷酸酶PTEN;以及PIP 3激酶、内质网（ER）应激和未折叠蛋白反应之间的新联系。后者通过p85 a与转录因子XBP-1的相互作用发生，并且可以改变参与胰岛素抵抗的ER应激反应。这使我们对不同PI 3-激酶催化和调节亚基的重要作用提出了新的假设，这些亚基是胰岛素信号通路中的分歧位点和生理和病理状态下的正调节和负调节位点，以及与其他信号系统的串扰位点。 在接下来的五年里，我们将扩大这些观察在分子和生理水平上定义不同的信号是如何产生的不同的监管和催化亚基PI 3激酶，具体的信号复合物参与，以及该系统在体内胰岛素抵抗和糖尿病状态的作用。具体而言，我们将进一步阐明PI 3-激酶调节亚基和ER应激诱导之间的联系，通过定义体内和肌肉中与p85调节亚基相互作用的特定途径和分子，并确定p85是否在糖尿病和其他胰岛素分泌改变的状态下胰腺B细胞的ER应激反应中起作用。这将在体外和体内通过产生与分泌突变胰岛素分子的小鼠或具有肥胖和高胰岛素血症状态的小鼠杂交的b细胞特异性p85 a KO小鼠来完成。我们还将描述与严重胰岛素抵抗相关的第一个人类p85突变，并确定PI 3-激酶催化亚基p110 a和p110 b在PI 3-激酶途径中不同胰岛素信号传导中的不同作用。

DESCRIPTION (provided by applicant): This is a competitive renewal of NIH grant DK55545 which is focused on the role of PI 3-kinase in insulin action. PI 3-kinase is a critical node in insulin action in control of metabolism and a key point of divergence of insulin signaling. In previous work under this grant using both in vitro and in vivo approaches, including creation and characterization of mice and cell lines in which specific isoforms of PI 3-kinase regulatory and catalytic subunits have been deleted, we have demonstrated that this enzyme controls insulin signaling in both positive and negative ways, and is involved in much more than simply generation of PIP3. This includes differences in the activity and properties of the different regulatory (p85) and catalytic (p110) subunits of PI 3-kinase; important effects of stoichiometry between regulatory and catalytic subunits on insulin action; the ability of PI 3-kinase to allow divergence of the downstream signal between Akt and atypical PKCs; and alterations in PI 3-kinase activity in disease states. In addition, we have identified several previously unrecognized links between the PI 3-kinase pathway and other signaling pathways, including differences between the p110a and p110b catalytic subunits in support of downstream insulin actions and important links between the p85 regulatory subunits and several pathways involved in insulin resistance, including the stress kinases JNK and p38; the major PIP3 phosphatase in cells and tissues PTEN; and a novel link between PI 3-kinase, endoplasmic reticulum (ER) stress and the unfolded protein response. The latter occurs through interaction of p85a with the transcription factor XBP-1 and can modify the ER stress response involved in insulin resistance. This has led us to new hypotheses about the important role of the different PI 3-kinase catalytic and regulator subunits as both sites of divergence in the insulin signaling pathway and sites of both positive and negative regulation in physiological and pathological states, as well as sites for cross-talk with other signaling systems. In the next five years, we will expand upon these observations at both the molecular and physiological levels by defining how different signals are generated by different regulatory and catalytic subunits of PI 3- kinase, the specific signaling complexes involved, and the role of this system in vivo in insulin resistant and diabetic states. Specificall we will further elucidate the link between PI 3-kinase regulatory subunits and induction of ER stress by defining the specific pathways and molecules interacting with the p85 regulatory subunits in vivo and muscle and determining if p85 plays a role in the ER stress response in pancreatic b-cells in diabetes and other states with altered insulin secretion. This will be done i vitro and in vivo through creation of b-cell specific p85a KO mice crossed with a mouse that secretes a mutant insulin molecule or mice with states of obesity and hyperinsulinemia. We will also characterize the first human mutation in p85 associated with severe insulin resistance and determine the differential roles of the PI 3-kinase catalytic subunits p110a and p110b in divergent insulin signaling in the PI 3-kinase pathway.