K-Ras sumoylation in cell proliferation and transformation

摘要 Ras蛋白是激活多个信号级联的GTP酶，其调节细胞凋亡。 存活、增殖、迁移和分化。Ras蛋白受几乎所有 已知的翻译后修饰，包括法尼基化，棕榈酰化，磷酸化， 泛素化和乙酰化。然而，Ras蛋白是否被修饰仍然是未知的， 通过SUMO化。我们最近发现，所有三种形式的Ras蛋白都是SUMO 3修饰的。 我们进一步的研究表明，赖氨酸42（K42）是sumo化的主要残基，而 皮亚斯γ和MEKK 1是使Ras类泛素化的候选E3连接酶。类小泛素化对于 激活K-Ras及其下游信号传导。此外，我们还发现了一系列 在体外和体内靶向SUMO结合的SUMO E1抑制剂。先导化合物 27 A和SB-264有效地抑制SUMO化，但不抑制泛素化或neddylation。值得注意的是， 这些化合物对杀死转化的胰腺细胞显示出优异的生物活性， 在甘氨酸12或甘氨酸13处的K-Ras突变并抑制它们的迁移。鉴于 类小泛素化在控制关键细胞调节因子的功能中的重要性，以及K- Ras在细胞增殖和转化中的作用，我们假设类小泛素化促进K-Ras 活性和SUMO调节途径是一个很好的目标，为发展抗- 抗癌药本文提出了三个具体的目标来检验假设的有效性。我们将 确定sumoylation调节K-Ras激活的机制，阐明 控制K-Ras类小泛素化的调控网络，并研究SUMO E1的功效 抑制剂在临床前小鼠模型中抑制胰腺癌生长的增殖。 K-Ras类小泛素化的进一步表征有望对我们的研究产生深远的影响。 了解调节细胞生长的基本细胞信号机制。给定 新的SUMO E1抑制剂的发现，我们提出的研究将有助于加速 开发靶向泛素样修饰的治疗应用。 !

ABSTRACT Ras proteins are GTPases that activate multiple signaling cascades, which modulate cell survival, proliferation, migration, and differentiation. Ras proteins are regulated by almost all known post-translational modifications, including farnesylation, palmitoylation, phosphorylation, ubiquitination, and acetylation. However, it remains unknown whether Ras proteins are modified by sumoylation. We recently discovered that all three forms of Ras protein are SUMO3-modified. Our further studies reveal that lysine 42 (K42) is the primary residue for sumoylation, whereas PIASγ and MEKK1 are candidate E3 ligases that sumoylate Ras. Sumoylation is essential for activating K-Ras and its downstream signaling. Furthermore, we have discovered a series of SUMO E1 inhibitors that target SUMO conjugation both in vitro and in vivo. The lead compounds 27A and SB-264 potently inhibit sumoylation, but not ubiquitination or neddylation. Significantly, these compounds display excellent bioactivities toward killing transformed pancreatic cells with K-Ras mutations at glycine 12 or glycine 13 and suppress their migration. Given the role of sumoylation in controlling functions of key cellular regulators and the paramount importance of K- Ras in cell proliferation and transformation, we hypothesize that sumoylation promotes K-Ras activity and that the SUMO regulatory pathway is an excellent target for development of anti- cancer drugs. Three Specific Aims are proposed to test the validity of the hypothesis. We will determine the mechanism by which sumoylation regulates K-Ras activation, elucidate the regulatory network that controls K-Ras sumoylation, and investigate the efficacy of SUMO E1 inhibitors in suppressing proliferation of pancreatic cancer growth in preclinical mouse models. Further characterization of K-Ras sumoylation promises to have a profound impact on our understanding of the fundamental cellular signaling mechanisms that regulate cell growth. Given the discovery of novel SUMO E1 inhibitors, our proposed studies will help to accelerate the development of therapeutic applications that target ubiquitin-like modifications. !