The Role of PTEN in Endothelial Biology

描述（由申请人提供）：血管生成是指从既存血管中生长出新毛细血管，受多种血管生长因子及其在内皮细胞上表达的同源受体酪氨酸激酶的严格调节;这些因子中的主要因子是血管内皮生长因子（VEGF）。VEGF通过酶磷酸肌醇（PI）3-激酶转导信号，该酶是内皮细胞生长、迁移和存活的关键调节因子。PI 3-激酶的磷脂产物激活多种下游效应蛋白，包括Akt，以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，其可以抑制细胞生长、迁移和存活。尽管这些作用主要将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的功能，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，我们在本提案中提出的数据将证明，PTEN和HIF-11物理相互作用; PTEN是必要的和足够的缺氧介导的基因表达的激活，这一过程可能是HIF-11依赖的;和PTEN的缺氧反应的增强是独立的催化活性。因此，我们的数据表明，在调节细胞对缺氧的反应，包括血管生成的关键作用，PTEN。因此，我们假设PTEN和HIF-11之间的相互作用是HIF-1介导的基因表达所必需的，并且内皮PTEN表达促进缺氧血管生成。其次，我们假设PTEN-HIF-11相互作用是缺氧时细胞周期停滞所必需的.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的内皮细胞的缺氧反应的机制; 2）确定PTEN缺陷对小鼠后肢缺血模型和肿瘤血管生成的缺氧血管生成的影响; 3）确定内皮特异性PTEN过表达对静止的成年血管系统和对后肢缺血和肿瘤生长期间的血管生成的影响。实现这些特定目的将阐明PTEN-HIF-11相互作用调节内皮细胞对缺氧的反应的机制，包括体内缺氧血管生成。这些研究的结果可能会导致开发新的策略，用于治疗各种血管生成性疾病，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.