Novel Methods for the Inhibition of Phosphatase Function

描述(申请人提供)：磷酸酪氨酸磷酸酶1B(PTP1B)调节葡萄糖摄取，已被证实为治疗II型糖尿病和肥胖症的药物靶点。尽管受到了广泛的关注，但小分子PTP1B抑制剂的发展一直受到两个主要问题的阻碍：由于大多数已知抑制剂的极性性质而缺乏生物利用度，以及由于PTP家族中高度保守的活性部位而导致该抑制剂相对于其他磷酸酶的选择性较差。因此，需要新的方法来抑制PTP1B和其他磷酸酶的功能。在这份提案中，我们概述了实现这一目标的两种不同战略。首先，我们建议开发一种新的小分子筛选策略，用于直接发现磷酸酶的变构配体。变构小分子可能会克服磷酸酶活性部位抑制剂的局限性，因为它可能会结合到磷酸酶的一个区域，而该区域并不像活性部位那样高度保守或极性。我们将利用钒酸根离子与磷酸酶活性部位结合的倾向，形成磷酸转移中关键过渡态的稳定类似物。我们建议通过实施小分子微阵列(SMM)技术来测试这一概念，以筛选钒稳定的PTP1B过渡态构象的小分子变构配体。抑制磷酸酶功能的第二种策略是通过将泛素-蛋白酶体途径重定向到目标磷酸酶来靶向降解磷酸酶。我们设想通过实施一种嵌合小分子来实现这一点，该嵌合小分子包含一个已知的PTP1B配体，该配体与一个低分子质量的类药物分子相连，该分子可以结合von Hippel-Lindau肿瘤抑制因子(VHL)，VHL是VBC-Cul2 E3泛素连接酶复合体的识别亚单位。这种针对嵌合体的蛋白水解酶(PROTAC)应该诱导PTP1B的多泛素化，导致其被蛋白质小体降解。这两种方法都致力于通过使用小分子来控制磷酸酶的功能。虽然我们最初将在经过充分研究的磷酸酶PTP1B上开发这些方法，PTP1B是治疗II型糖尿病的有效药物靶点，但我们随后计划将这些研究扩展到与癌症和其他疾病有关的其他磷酸酶。

DESCRIPTION (provided by applicant): Phosphotyrosine Phosphatase 1B (PTP1B) regulates glucose uptake and has been validated as a drug target for the treatment of type II diabetes as well as obesity. Despite widespread interest, the development of small molecule PTP1B inhibitors has been hindered by two main issues; the lack of bioavailability due to the polar nature of most known inhibitors and poor selectivity of the inhibitor over other phosphatases due to the highly conserved active sites across the PTP family. Because of this a need exists for new methodologies to inhibit the functions of PTP1B and other phosphatases. In this proposal we outline two different strategies to accomplish this goal. First, we propose to develop a novel small molecule screening strategy for the direct discovery of allosteric ligands of phosphatases. An allosteric small molecule is likely to overcome the stated limitations of phosphatase active site inhibitors since it would likely bind to a region of the phosphatase that is not as highly conserved or polar as the active site. We will capitalize on the well precedented propensity of vanadate ions to bind the active site of phosphatases and form stable analogs of key transition states in phosphate transfer. We propose to test this concept by implementing Small Molecule Microarray (SMM) technology to screen for small molecule allosteric ligands of a vanadate stabilized transition state conformation of PTP1B. A second strategy for inhibiting phosphatase function is to target the phosphatase for degradation by redirecting the ubiquitin-proteasome pathway towards a target phosphatase. We envision achieving this for PTP1B by implementing a chimeric small molecule containing a known PTP1B ligand tethered to a low molecular weight drug-like molecule that can bind the von Hippel-Lindau tumor suppressor (VHL), the recognition subunit of the VBC-Cul2 E3 ubiquitin ligase complex. Such a PROteolysis TArgeting Chimera (PROTAC) should induce the poly-ubiquitination of PTP1B, leading to its degradation by the proteosome. Both of these methodologies strive to control the function of phosphatases through the use of small molecules. While we will initially develop these methodologies on the well studied phosphatase PTP1B, a validated drug target for type II diabetes, we subsequently plan to expand these studies to other phosphatases which have been implicated in cancer and other diseases.