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: 8078009
• 负责人: Jeffrey Paul MacKeigan
• 金额: $ 26.88万
• 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/8078009
• 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; Gatekeeping; Health; 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; follow-up; in vivo; metastatic colorectal; neoplastic cell; novel; overexpression; prognostic; protein complex; 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有针对性治疗方案的武器库增加，但化学抗性转移性疾病对癌症患者构成了最严重的威胁。尽管对晚期癌症进展的强烈研究揭示了许多有助于化学抗性的机制，但对细胞内信号传导机制几乎不了解，这些机制使细胞脱敏至细胞毒性化学疗法。为了解决这一知识差距，我们最近进行了大规模的RNA干扰（RNAi）筛选，旨在全面识别人类基因组中的关键激酶和磷酸酶，以改变或改变对化学治疗剂的肿瘤细胞敏感性。在这个RNAi筛选中，我们确定了一种新型的磷酸酶MK-STYX，该酶有效抑制了肿瘤细胞对多种化学治疗药物的反应。我们的中心假设是，MK-STYX通过调节ATP合成所需的机械的磷酸化来特异性控制线粒体功能，从而在诱导化学治疗诱导的细胞死亡中起着至关重要的作用。该项目的目的是确定MK-STYX如何调节细胞ATP水平，从而调节内在凋亡。我们提出了以下具体旨在解决这一假设并在转移性结直肠癌的背景下理解其意义的特定目的：（1）确定线粒体中MK-STYX的催化机制； （2）确定MK-Styx调节化学抗性的机制； （3）确定MK-STYX在结直肠癌进展和化学上的作用。与我们的中心假设一致，我们表明MK-STYX的损失会增加ATP的产生。因此，我们预测，由于MK-STYX的损失而导致的细胞ATP升高足以抑制凋亡组的形成并进入细胞凋亡。我们已经表明，MK-Styx与另外两个线粒体蛋白相互作用，我们将机械地确定这些相互作用的线粒体功能和分子后果。我们还表明，MK-STYX表达的丧失与结直肠癌的进展相关。为了确定MK-STYX的损失是否介导体内化学耐药性，我们将使用证明MK-STYX的可变表达或已操纵以降低内源性MK-STYX水平的细胞系来测试标准化学疗法对结直肠异种移植模型的功效。我们还将确定大肠癌患者队列中MK-Styx蛋白水平的预后意义。公共卫生相关性：我们最近对抑制化学抗性或表达促进化学敏感性的13种磷酸酶的鉴定为更好地理解化学耐药性的分子基础提供了途径。如果我们能确定这些磷酸酶表达的丧失如何导致化学耐药性的发展，那么我们将能够更好地筛选化学耐药性和设计合理的药物策略，以治疗癌症患者的化学耐药性肿瘤。