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).

该子项目是利用该技术的众多研究子项目之一 资源由 NIH/NCRR 资助的中心拨款提供。子项目和 研究者 (PI) 可能已从 NIH 的另一个来源获得主要资金， 因此可以在其他 CRISP 条目中表示。列出的机构是 中心，不一定是研究者的机构。 具体目标对原始申请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，通过将磷酸胆碱基团从磷脂酰胆碱 (PC) 转移到神经酰胺上。在反应过程中，还会产生二酰基甘油（DAG）分子。因此，SMS的生物学重要性，除了SM的合成外，可能还在于对两种重要生物活性脂质神经酰胺和二酰甘油（DAG）水平的相反方向的调节，这两种脂质在关键细胞功能的控制中经常发挥拮抗作用例如增殖、凋亡和/或分化。在哺乳动物细胞中，SMS 由两个最近发现的基因 SMS1 和 SMS2 编码。 PI 实验室的初步数据显示，表达 bcr-abl 癌基因的慢性粒细胞白血病 (CML) 细胞的 SMS 活性显着升高。 CML是一种造血干/祖细胞的骨髓增殖性疾病，占成人白血病的15-20%。 CML 是由 bcr-abl 癌基因的表达引发的，该癌基因编码一种组成型活性酪氨酸激酶，该激酶具有增殖优势并提高细胞存活率，部分通过抑制肿瘤抑制蛋白磷酸酶 2A (PP2A) 来实现。我们表明，SMS 活性的增加可以通过 bcr-abl 癌基因在其他 bcr-abl 阴性细胞中的表达来概括，而抑制 bcr-abl 活性会显着降低 SMS 活性。我们还证明 bcr-abl 诱导的 SMS 活性增加是由于 SMS1 而非 SMS2 mRNA 表达增加所致。值得注意的是，将 SMS 活性抑制至接近 bcr-abl 阴性细胞的水平可显着降低 bcr-abl 阳性祖细胞的细胞增殖并促进其分化。在bcr-abl阳性细胞中抑制SMS或bcr-abl活性会引起神经酰胺的积累和DAG的减少，PP2A的下调部分恢复了抑制SMS活性后观察到的增殖抑制。由于已知神经酰胺可促进 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 SMS1 活性升高维持其致瘤潜力； 3) SMS1 调节的生物活性脂质部分通过 PP2A 依赖性机制负责维持 bcr-abl 依赖性促肿瘤发生信号传导。为了验证我们的假设，我们将阐明bcr-abl对SMS1的调节机制（规范目标1），并确定SMS1在bcr-abl阳性细胞致瘤潜力中的作用及其作用机制（规范目标2） 。