The Role of PTEN in Endothelial Biology

描述（由申请人提供）：血管生成，即从已有血管中生成的新毛细血管，受到内皮细胞上表达的许多血管生长因子及其同源受体酪氨酸激酶的严格调控；其中最主要的是血管内皮生长因子（VEGF）。VEGF通过磷酸肌苷（PI） 3-激酶转导信号，这是内皮细胞生长、迁移和存活的关键调节因子。PI 3-激酶的磷脂产物激活包括Akt在内的多种下游效应蛋白，促进血管生成所需的内皮细胞反应。这些途径被脂质磷酸酶PTEN破坏，它可以抑制细胞的生长、迁移和存活。虽然这些作用主要将PTEN定位在质膜上，但最近的数据表明，核PTEN具有独立于其对PI 3-激酶/Akt或其催化活性的作用，包括与p53和p300/CBP相互作用以调节p53介导的转录。与这些发现一致，我们实验室的初步数据表明，PTEN在物理和功能上与缺氧诱导因子(HIF)-11相互作用，HIF -11是缺氧血管生成的关键调节因子。具体来说，我们在本提案中提供的数据将证明PTEN和HIF-11存在物理相互作用；PTEN对于缺氧介导的基因表达激活既是必要的也是充分的，这一过程可能依赖于hif -11；PTEN对缺氧反应的增强与其催化活性无关。因此，我们的数据表明PTEN在调节细胞对缺氧的反应中起关键作用，包括血管生成。因此，我们假设PTEN和HIF-11之间的相互作用对于hif -1介导的基因表达是必要的，内皮细胞PTEN的表达促进了缺氧血管生成。其次，我们假设PTEN- HIF-11相互作用是缺氧期间细胞周期阻滞所必需的。为了进一步研究PTEN-HIF-11相互作用的机制和功能后果，本研究的具体目的是：1)确定PTEN与HIF-11相互作用并调节体外培养内皮细胞缺氧反应的机制；2)确定PTEN缺乏对小鼠后肢缺血和肿瘤血管生成模型缺氧血管生成的影响；3)确定内皮特异性PTEN过表达对静止成人血管系统及后肢缺血和肿瘤生长过程中血管生成的影响。完成这些特定目标将阐明PTEN-HIF-11相互作用调节内皮细胞对缺氧反应的机制，包括体内缺氧血管生成。这些研究的结果可能会导致治疗各种血管生成疾病的新策略的发展，包括缺血性血管疾病和癌症。

DESCRIPTION (provided by applicant): Angiogenesis, the growth of new capillaries from pre-existing blood vessels, is tightly regulated by a number of vascular growth factors and their cognate receptor tyrosine kinases expressed on endothelial cells; principal among these factors is vascular endothelial growth factor (VEGF). VEGF transduces signals through the enzyme phosphoinositide (PI) 3-kinase, which is a key regulator of endothelial cell growth, migration, and survival. The phospholipid products of PI 3-kinase activate multiple downstream effector proteins, including Akt, to promote the endothelial cellular responses required for angiogenesis. These pathways are disrupted by the lipid phosphatase PTEN, which can inhibit cell growth, migration, and survival. While these effects position PTEN primarily at the plasma membrane, recent data have demonstrated that nuclear PTEN has functions independent of its effects on PI 3-kinase/Akt or its catalytic activity, including interaction with p53 and p300/CBP to regulate p53-mediated transcription. Consistent with these findings, preliminary data from our lab demonstrate that PTEN physically and functionally interacts with hypoxia-inducible factor (HIF)-11, a critical regulator of hypoxic angiogenesis. Specifically, our data presented in this proposal will demonstrate that PTEN and HIF-11 physically interact; that PTEN is both necessary and sufficient for activation of hypoxia-mediated gene expression, a process that is likely HIF-11-dependent; and that PTEN's enhancement of the hypoxic response is independent of its catalytic activity. Our data therefore suggest a key role for PTEN in the regulation of cellular responses to hypoxia, including angiogenesis. Accordingly, we hypothesize that interaction between PTEN and HIF-11 is necessary for HIF-1-mediated gene expression and that endothelial PTEN expression facilitates hypoxic angiogenesis. Secondarily, we hypothesize that PTEN- HIF-11 interaction is required for cell cycle arrest during hypoxia. To further investigate the mechanism and functional consequences of the PTEN-HIF-11 interaction, the Specific Aims of this proposal are to: 1) Determine the mechanisms by which PTEN interacts with HIF-11 and modulates the hypoxic response in cultured endothelial cells in vitro; 2) Determine the effects of PTEN deficiency on hypoxic angiogenesis in murine models of hind limb ischemia and tumor angiogenesis; 3) Determine the effects of endothelium-specific PTEN overexpression on the quiescent adult vasculature and on angiogenesis during hind limb ischemia and tumor growth. Accomplishing these Specific Aims will shed light on the mechanisms by which the PTEN-HIF-11 interaction regulates the response of endothelial cells to hypoxia, including hypoxic angiogenesis in vivo. The results of these studies may lead to the development of novel strategies for the treatment of a variety of angiogenic diseases, including ischemic vascular diseases and cancer.