MK-STYX: A Requisite Gatekeeper to Mitochondrial Function and Death

MK-STYX：线粒体功能和死亡必需的看门人

• 批准号: 7741769
• 负责人: Jeffrey Paul MacKeigan
• 金额: $ 27.71万
• 依托单位: VAN ANDEL RESEARCH INSTITUTE
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2014-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7741769
• 关键词: ATP Synthesis Pathway; Address; Apoptosis; Apoptotic; Cancer Patient; Caspase; Cell Death; Cell Line; Cells; Cessation of life; Colorectal; Colorectal Cancer; Complex; Coupled; Cytotoxic Chemotherapy; Data; Development; Disease; Drug Efflux; Electron Transport; Electrons; Follow-Up Studies; Gatekeeping; Housing; Human Genome; Kinetics; Knowledge; Large Intestine Carcinoma; Measures; Mediating; Mitochondria; Mitochondrial Proteins; Molecular; Multidrug Resistance Gene; Organelles; Oxidative Phosphorylation; Patients; Pharmaceutical Preparations; Phosphoric Monoester Hydrolases; Phosphorylation; Phosphotransferases; Physiological; Process; Production; Proteins; Public Health; RNA Interference; Role; Signal Transduction; Staging; Stimulus; Testing; Time; Xenograft Model; base; cell type; chemotherapeutic agent; chemotherapy; cohort; cytochrome c; design; efficacy testing; efflux pump; in vivo; metastatic colorectal; neoplastic cell; novel; overexpression; prognostic; protein complex; public health relevance; response; therapeutic target; tumor; tumor progression

DESCRIPTION (provided by applicant): Chemoresistant metastatic disease presents the most serious threat to cancer patients despite the increased arsenal of targeted therapeutic options available to clinicians. While intense study into late-stage cancer progression has revealed a number of mechanisms that contribute to chemoresistance, little is known about the intracellular signaling mechanisms that desensitize cells to cytotoxic chemotherapy. In an effort to address this knowledge gap, we recently performed a large-scale RNA-interference (RNAi) screen intended to comprehensively identify critical kinases and phosphatases in the human genome that alter or modify tumor cell sensitivity to chemotherapeutic agents. In this RNAi screen, we identified a novel phosphatase, MK-STYX, which potently suppressed the response of tumor cells to a wide variety of chemotherapeutic drugs. Our central hypothesis is that MK-STYX specifically controls mitochondrial function by regulating phosphorylation of the machinery required for ATP synthesis, and thereby serves an essential role in the induction of chemotherapeutic-induced cell death. The objective of this project is to determine how MK-STYX regulates cellular ATP levels, and thus modulates intrinsic apoptosis. We propose the following specific aims to address this hypothesis and to understand its significance in the context of metastatic colorectal carcinoma: (1) Identify the catalytic mechanism of MK-STYX in the mitochondria; (2) Identify the mechanism whereby MK-STYX regulates chemoresistance; (3) Establish the role of MK-STYX in colorectal cancer progression and chemoresistance. Consistent with our central hypothesis, we have shown that loss of MK-STYX increases ATP production. Therefore, we predict that the elevation in cellular ATP due to loss of MK-STYX is sufficient to inhibit apoptosome formation and entry into apoptosis. We have shown that MK-STYX interacts with two additional mitochondrial proteins and we will mechanistically determine the mitochondrial function and the molecular consequences of each of these interactions. We have also shown that loss of MK-STYX expression correlates with colorectal cancer progression. To determine whether loss of MK-STYX mediates chemoresistance in vivo, we will test the efficacy of standard chemotherapies on a colorectal xenograft model using cell lines that demonstrate variable expression of MK-STYX, or have been manipulated to decrease endogenous MK-STYX levels. We will also determine the prognostic significance of MK-STYX protein levels in a cohort of patients with colorectal cancer. PUBLIC HEALTH RELEVANCE: Our recent identification of thirteen phosphatases that suppress chemoresistance, or whose expression drives chemosensitivity, has provided an avenue for a better understanding of the molecular basis of chemoresistance. If we can determine how loss of expression of these phosphatases leads to the development of chemoresistance, we will be better able to screen for chemoresistance and design rational drug strategies to treat chemoresistant tumors in cancer patients.

描述（由申请人提供）：尽管临床医生可用的靶向治疗选择不断增加，但耐药性转移性疾病对癌症患者构成了最严重的威胁。虽然对晚期癌症进展的深入研究揭示了许多导致化疗耐药的机制，但人们对使细胞对细胞毒性化疗不敏感的细胞内信号传导机制知之甚少。为了弥补这一知识差距，我们最近进行了大规模 RNA 干扰 (RNAi) 筛选，旨在全面鉴定人类基因组中改变或改变肿瘤细胞对化疗药物敏感性的关键激酶和磷酸酶。在这次 RNAi 筛选中，我们发现了一种新型磷酸酶 MK-STYX，它能有效抑制肿瘤细胞对多种化疗药物的反应。我们的中心假设是 MK-STYX 通过调节 ATP 合成所需机制的磷酸化来特异性控制线粒体功能，从而在诱导化疗诱导的细胞死亡中发挥重要作用。该项目的目标是确定 MK-STYX 如何调节细胞 ATP 水平，从而调节内在细胞凋亡。我们提出以下具体目标来解决这一假设并了解其在转移性结直肠癌中的意义：（1）确定 MK-STYX 在线粒体中的催化机制； (2) 确定MK-STYX调节化疗耐药的机制； (3) 确定MK-STYX在结直肠癌进展和化疗耐药中的作用。与我们的中心假设一致，我们已经证明 MK-STYX 的损失会增加 ATP 的产生。因此，我们预测，由于 MK-STYX 缺失而引起的细胞 ATP 升高足以抑制凋亡体形成和进入细胞凋亡。我们已经证明 MK-STYX 与另外两种线粒体蛋白相互作用，我们将机械地确定线粒体功能以及每种相互作用的分子后果。我们还发现 MK-STYX 表达缺失与结直肠癌进展相关。为了确定 MK-STYX 的缺失是否会介导体内化疗耐药性，我们将使用表现出 MK-STYX 可变表达或已被操纵以降低内源 MK-STYX 水平的细胞系，在结直肠异种移植模型上测试标准化疗的功效。我们还将确定结直肠癌患者队列中 MK-STYX 蛋白水平的预后意义。公共健康相关性：我们最近鉴定了 13 种抑制化疗耐药性或其表达驱动化疗敏感性的磷酸酶，为更好地了解化疗耐药性的分子基础提供了途径。如果我们能够确定这些磷酸酶表达的缺失如何导致化疗耐药的发生，我们将能够更好地筛选化疗耐药并设计合理的药物策略来治疗癌症患者的化疗耐药肿瘤。