De-SUMOylation and the Hypoxic Response

描述(申请人提供)：SUMO(小泛素样修饰物)是一种泛素样蛋白，可以共价修饰大量细胞蛋白。相扑是一个动态的过程，它由激活(E1)、结合(E2)和连接(E3)酶介导，并容易被一系列相扑专一性蛋白酶(SENP)逆转。我们发现，SENP1基因的失活会导致小鼠妊娠中期的胚胎死亡，这是由于促红细胞生成素(EPO)产生不足而导致严重的胎儿贫血。SENP1通过调节缺氧诱导因子11(HIF11)在低氧条件下的稳定性来控制EPO的产生。在常氧状态下，HIF11在两个关键的脯氨酸残基上被一系列氧气感受酶羟化。脯氨酸羟化是HIF11与其泛素连接酶复合体、von Hippel-Lindau蛋白VHL/细长蛋白B/C复合体结合，导致泛素化和蛋白酶体降解的重要途径。我们发现，缺氧诱导了HIF11的快速SUMO化，这使得它能够以一种不依赖于羟脯氨酸的方式与VHL结合，也导致泛素化和蛋白酶体降解。SENP1逆转HIF11的SUMO化，减少与VHL的结合，从而稳定HIF11。因此，SENP1在调节HIF11在缺氧过程中的稳定性方面起着关键作用。由于HIF11调控多个关键的下游基因，如EPO和血管内皮生长因子，它具有调节红细胞生成和血管生成的潜力。在初步结果中，我们发现SUMO化HIF11的积累在低氧暴露后4小时达到峰值，随后下降。这对应于SUMO化的早期阶段，最可能是通过相扑E3活性的增加和后期的去SUMO化，最可能是通过SENP1活性的增加。在这项提案中，我们将研究SUMO化和去SUMO化在缺氧调节HIF11中的作用及其下游影响，重点是血管生成。目的1：确定低氧诱导HIF11 SUMO化的E3基因。目的2：研究低氧对SENP1的调节作用。目的：确定SENP1在发育过程中和肿瘤环境中是否调节血管生成。这些研究应该为去SUMO化途径如何调节低氧反应提供新的见解。与公共健康相关：我们发现了一种名为SENP1的蛋白质，它可以从相扑修饰的蛋白质中去除相扑(小泛素样修饰物)。由于SENP1在低氧环境中维持缺氧诱导因子11(HIF11)的稳定性，SENP1在小鼠体内的缺失会导致胚胎因严重贫血而过早死亡。我们将研究SENP1如何受低氧调节，HIF11如何被相扑修饰，以及SENP1如何调控正常和异常血管的发育。

DESCRIPTION (provided by applicant): SUMO (Small Ubiquitin-like Modifier) is a ubiquitin-like protein that can covalently modify a large number of cellular proteins. SUMOylation is a dynamic process that is mediated by activating (E1), conjugating (E2), and ligating (E3) enzymes and readily reversed by a family of SUMO-specific proteases (SENP). We showed that inactivation of the SENP1 gene causes embryonal lethality in mid- gestation in mice as a result of severe fetal anemia stemming from deficient erythropoietin (Epo) production. SENP1 controls Epo production by regulating the stability of hypoxia-inducible factor 11 (HIF11) in hypoxic condition. During normoxia, HIF11 is hydroxylated in two critical proline residues by a family of oxygen sensing enzymes. Proline hydroxylation is important for HIF11 to binds to its ubiquitin ligase complex, von Hippel-Lindau protein VHL/elongin B/C complex, leading to ubiquitination and proteasomal degradation. We showed that hypoxia induced rapid SUMOylation of HIF11, which allowed it to bind to VHL in a hydroxyl-proline-independent manner, also leading to ubiquitination and proteasomal degradation. SENP1 reverses SUMOylation of HIF11, reduces binding to VHL, and consequently stabilizes HIF11. Thus, SENP1 plays a critical role in regulating HIF11 stability during hypoxia. Since HIF11 regulates multiple, critical downstream genes, such as Epo and VEGF, it has the potential to regulate erythropoiesis and angiogenesis. In preliminary results, we showed that accumulation of SUMOylated HIF11 peaked at four hours after exposure to hypoxia and later declined. This corresponded to an early phase of SUMOylation, most likely by an increase in SUMO E3 activity and a later phase of de-SUMOylation, most likely mediated by an increase in SENP1 activity. In this proposal, we will examine the role of SUMOylation and de-SUMOylation in HIF11 regulation by hypoxia and its downstream effects, focusing on angiogenesis. AIM 1: To identify the E3 responsible for hypoxia-induced SUMOylation of HIF11. AIM 2: To study how SENP1 is regulated by hypoxia. AIM3: To determine whether SENP1 regulates angiogenesis during development and in the tumor environment. These studies should provide novel insights into how the de-SUMOylation pathway regulates the hypoxic response. PUBLIC HEALTH RELEVANCE: We discovered a protein called SENP1 that can remove SUMO (Small Ubiquitin-like modifier) from SUMO- modified proteins. Deletion of SENP1 in mouse causes the embryo to die early due to severe anemia because SENP1 is required to maintain the stability of hypoxia-inducible factor 11 (HIF11) in the hypoxic environment. We will study how SENP1 is regulated by hypoxia, how HIF11 is modified by SUMO, and how SENP1 can regulate the development of normal and abnormal blood vessels.