Divergent Functions of ERK Substrate Binding Domains in Pathogenesis of Myeloproliferative Neoplasms

项目概要/摘要 Ras/MAPK通路在85%的人类癌症中被激活。然而，针对Ras/MAPK的尝试 信号传导仅产生有限的功效。我们假设，一个原因，失败的成功， 靶向该途径的另一个重要原因是靶向工作集中在该级联中激酶的活性位点， 未能提供长期的益处。我们假设这种方法的失败来自两个方面 原因：1）活性位点抑制剂，类似于三磷酸腺苷（ATP），必须克服 癌细胞中较高的胞质ATP水平;和2）该级联中的关键激酶（例如，ERK 1/2）具有明显的 底物相互作用结构域可以在调节癌症进展中发挥拮抗作用。 因此，活性部位集中抑制类似于同时踩下油门和刹车 汽车的踏板。我们假设，一个更成功的方法将是开发抑制剂， 保留激酶活性，但将其专门转移到“刹车踏板”底物。为了表示支持，我们已经证明 ERK 2的两个底物结合结构域，称为D和DPB结构域，在细胞凋亡中起相反的作用。 JAK 2-激酶驱动的骨髓增生性肿瘤（MPN）的发病机制。事实上，DBP和D结构域 就像刹车和加速踏板，分别阻止和促进疾病的发展。因此，委员会认为， 加速器踏板（D-结构域）或其底物的药理学衰减应会损害肿瘤进展 比活性位点抑制更有效，因为它选择性地干扰疾病促进活性， ERK 2，同时保留DBP结构域的肿瘤抑制功能。虽然我们有确凿的证据 对于ERK 2-D和DBP结构域的相反作用，其作用的分子基础仍不清楚 并且这是开发集中于ERK 2 D域的有效的药理学干预的障碍。 我们现在根据以下目标寻求解决这一知识差距。我们将：1）评估一般性 ERK 2-D和DBP结构域在不同MPN亚型发病机制中的相反功能; 2） 理解ERK 2-D和DBP结构域发挥其独特功能的机制基础;以及3） 评估ERK 2-D结构域和/或其靶点的药理学靶向在抑制癌症中的功效 进展通过这些努力，我们期望为ERK 2底物结合的作用带来新的见解。 调节癌症进展的模块以及如何在治疗上利用这些信息。当我们开始 MPN，这些发现可能对其他Ras/MAPK驱动的癌症具有深远的影响。

PROJECT SUMMARY/ABSTRACT The Ras/MAPK pathway is activated in 85% of human cancer. Nevertheless, attempts to target Ras/MAPK signaling have produced only limited efficacy. We hypothesize that one reason for the failure to successfully target this pathway is that the targeting efforts have focused on the active sites of kinases in this cascade, which has failed to provide long-lasting benefit. We hypothesize that the failure of this approach results from two causes: 1) Active site inhibitors, which resemble adenosine triphosphate (ATP), must overcome the exceedingly high cytosolic ATP levels in cancer cells; and 2) critical kinases in this cascade (e.g., ERK1/2) have distinct substrate interactions domains that can perform antagonistic roles in regulating cancer progression. Consequently, active-site focused inhibition is akin to simultaneous depression of the accelerator and brake pedals of an automobile. We hypothesize that a more successful approach will be to develop inhibitors which preserve kinase activity, but divert it exclusively to “brake pedal” substrates. In support, we have demonstrated that the two substrate binding domains of ERK2, termed the D and DPB domains, play opposing roles in the pathogenesis of JAK2-kinase driven myeloproliferative neoplasms (MPN). Indeed, the DBP and D domains act like brake and accelerator pedals, opposing and promoting disease progression, respectively. Consequently, pharmacologic attenuation of the accelerator pedal (D-domain) or its substrates should impair tumor progression more potently than active site inhibition, because it selectively interferes with the disease promoting activity of ERK2, while preserving the tumor suppressive function of the DBP-domain. While we have compelling evidence for the opposing roles of the ERK2-D and DBP domains, the molecular basis for their action remains unclear and this is an impediment to developing effective, pharmacologic interventions focused on the ERK2 D domain. We now seek to address this gap in knowledge according to the following aims. We will: 1) Assess the generality of the opposing functions of the ERK2-D and DBP domains in the pathogenesis of distinct MPN subtypes; 2) Understand the mechanistic basis by which the ERK2-D and DBP domains exert their distinct functions; and 3) Assess the efficacy of pharmacologic targeting of the ERK2-D domain and/or its targets in inhibiting cancer progression. Through these efforts we expect to bring new insights into the role of ERK2 substrate binding modules in regulating cancer progression and how to exploit this information therapeutically. While we begin with MPN, these findings may have far reaching implications for other Ras/MAPK driven cancers.