ROEL AND FUNCTION OF MAMMALIAN SPHINGOMYELIN SYNTHASES

哺乳动物鞘磷脂合成酶的作用和作用

• 批准号: 8168049
• 负责人: CHIARA LUBERTO
• 金额: $ 18.25万
• 依托单位: MEDICAL UNIVERSITY OF SOUTH CAROLINA
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2011-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8168049
• 关键词: 1,2-diacylglycerol; Accounting; Anabolism; Apoptosis; Biological; Cell Proliferation; Cell Survival; Cell physiology; Cells; Ceramides; Chronic Myeloid Leukemia; Computer Retrieval of Information on Scientific Projects Database; Data; Diglycerides; Down-Regulation; Enzymes; Funding; Genes; Grant; Institution; Laboratories; Lipids; Maintenance; Mammalian Cell; Messenger RNA; Myeloproliferative disease; Phosphoric Monoester Hydrolases; Phosphorylcholine; Play; Protein Tyrosine Kinase; Protein phosphatase; Reaction; Regulation; Research; Research Personnel; Resources; Role; Signal Transduction; Source; Sphingomyelins; Stem cells; Testing; Tumor Suppressor Proteins; United States National Institutes of Health; abl Oncogene; adult leukemia; progenitor; sphingomyelin synthase; stem; tumorigenic

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The specific aims have been modified from those proposed in the original application. Sphingomyelin synthase (SMS) is a class of enzymes responsible for the biosynthesis of sphingomyelin (SM), by transferring a phosphocholine mojety from phosphatydylcholine (PC) onto ceramide. In the course of the reaction, a molecule of diacylglycerol (DAG) is also produced. Therefore, the biological importance of SMS, besides synthesis of SM, may reside in the regulation in opposing directions, of the levels of two important bioactive lipids, ceramide and diacylglycerol (DAG), which often play antagonistic roles in the control of key cellular functions such as proliferation, apoptosis, and/or differentiation. In mammalian cells, SMS is encoded by two recently identified genes, SMS1 and SMS2. Preliminary data from the PI's laboratory show Chronic Myelogenous Leukemia (CML) cells that express the bcr-abl oncogene have a significantly elevated SMS activity. CML is a myeloproliferative disorder of hemopoietic stem/progenitor cells and it accounts for 15-20% of adult leukemia. CML is initiated by the expression of the bcr-abl oncogene that encodes for a constitutively active tyrosine kinase which confers proliferative advantage and enhances cell survival, in part by inhibiting the tumor suppressor protein phosphatase 2A (PP2A). We showed that the increase of SMS activity can be recapitulated by expression of the bcr-abl oncogene in otherwise bcr-abl negative cells whereas inhibition of bcr-abl activity significantly reduces SMS activity. We also demonstrated that the bcr-abl-induced increase of SMS activity is due to increased expression of SMS1 and not SMS2 mRNA. Remarkably, inhibition of SMS activity to levels approaching bcr-abl negative cells significantly reduced cell proliferation of bcr-abl-positive progenitors and promoted their differentiation. Inhibition of SMS or bcr-abl activity in bcr-abl positive cells caused an accumulation of ceramide, and decrease of DAG, and down-regulation of PP2A partially reverted the block of proliferation observed upon inhibition of SMS activity. Since it is known that ceramide promotes PP2A activity, we HYPOTHESIZE that: 1) bcr-abl elevates SMS activity by enhancing expression of SMS1; 2) elevated SMS1 activity in bcr-abl-positive cells sustains their tumorigenic potential; and 3) the bioactive lipids regulated by SMS1 are responsible for maintenance of the bcr-abl-dependent pro-tumorigenic signaling in part through a PP2A-dependent mechanism. To test our hypothesis, we will elucidate the mechanism of SMS1 regulation by bcr-abl (Spec. Aim 1) and determine the role of SMS1 in the tumorigenic potential of bcr-abl positive cells and its mechanism of action (Spec. Aim 2).

该副本是利用众多研究子项目之一 由NIH/NCRR资助的中心赠款提供的资源。子弹和 调查员（PI）可能已经从其他NIH来源获得了主要资金， 因此可以在其他清晰的条目中代表。列出的机构是 对于中心，这不一定是调查员的机构。 特定目标已从原始应用中提出的目标进行了修改。 鞘磷脂合酶（SMS）是一类负责鞘磷脂（SM）生物合成的酶，通过将磷胆碱含量从磷酸胆碱（PC）转移到神经酰胺上。在反应过程中，还产生了二酰基甘油（DAG）的分子。因此，除SM的合成外，SMS的生物学重要性可能存在于相反方向的调节中，即两个重要的生物活性脂质，神经酰胺和二酰基甘油（DAG）的水平，通常在关键细胞功能的控制中起拮抗作用，例如增殖，凋亡，凋亡和/或分化。在哺乳动物细胞中，SMS由两个最近鉴定的基因SMS1和SMS2编码。 来自PI实验室的初步数据表明，表达BCR-ABL癌基因的慢性粒细胞性白血病（CML）细胞的SMS活性显着升高。 CML是血有茎/祖细胞的髓增生性疾病，占成年白血病的15-20％。 CML是由BCR-ABL癌基因的表达引发的，该表达编码为组成型活性酪氨酸激酶，该激酶赋予增殖优势并增强细胞存活，部分原因是抑制肿瘤抑制蛋白磷酸酶2a（PP2A）。我们表明，在否则BCR-ABL阴性细胞中BCR-ABL癌基因的表达可以概括SMS活性的增加，而BCR-ABL活性的抑制显着降低了SMS活性。我们还证明了BCR ABL诱导的SMS活性的增加是由于SMS1的表达增加而不是SMS2 mRNA所致。值得注意的是，抑制接近BCR-ABL阴性细胞水平的SMS活性显着降低了BCR-ABL阳性祖细胞的细胞增殖并促进其分化。 BCR-ABL阳性细胞中SMS或BCR-ABL活性的抑制导致神经酰胺的积累，DAG的降低，PP2A的下调部分恢复了抑制SMS活性时观察到的增殖块。由于已知神经酰胺促进了PP2A活性，因此我们假设：1）BCR-ABL通过增强SMS1的表达来提高SMS活性； 2）BCR-ABL阳性细胞中的SMS1活性升高可维持其肿瘤性潜力； 3）由SMS1调节的生物活性脂质负责维持BCR-ABL依赖性的亲阳离子信号，部分通过PP2A依赖性机制来维持。为了检验我们的假设，我们将通过BCR-ABL阐明SMS1调节的机理（Spec。AIM1），并确定SMS1在BCR-ABL阳性细胞的致瘤潜力中的作用及其作用机理（Spec。AIM2）。