ROLE AND FUNCTION OF MAMMALIAN SPHINGOMYELIN SYNTHASES

哺乳动物鞘磷脂合成酶的作用和功能

• 批准号: 7381851
• 负责人: CHIARA LUBERTO
• 金额: $ 21.38万
• 依托单位: MEDICAL UNIVERSITY OF SOUTH CAROLINA
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-07-01 至 2007-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7381851
• 关键词: ROLE; FUNCTION; MAMMALIAN; SPHINGOMYELIN; SYNTHASES

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. SMS represents an important class of enzymes responsible for the biosynthesis of sphingomyelin (SM), a critical structural component of the plasma membrane. Moreover, in the course of its biochemical reaction, SMS also regulates, in opposing directions, 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 and/or induction of cell death. Recently two enzymes, SMS1 and SMS2 have been proposed as potential SMSs based on biochemical characterization studies using a yeast expression system. Soon after, SMS1 was proved to mediate SM synthesis in mammalian cells. Previous studies conducted by the PI showed that activation of SM synthesis coupled with activation of NF-kB, a pivotal transcription factor, involved in the regulation of cellular functions, such as survival and inflammatory response. Our results obtained during year 1 of the present project characterized SMS2 as a SMS in mammalian cells, thus demonstrating that both SMS1 and SMS2 are capable of SMS activity in mammalian cells. Additionally, we found that knock-down of SMS2 significantly impaired basal and cytokine induced-activation of NF-kB in a PKC-independent manner, with consequent inhibition of the expression of NF-kB-responsive genes, such as the cyclooxigenase 2 gene (cox-2). Based on the potential role of SMS2 in promoting NF-kB activation and because NF-kB activation has been identified as a key factor promoting cancer development, we HYPOTHESIZE that SMS regulates activation of the prosurvival transcription factor NF-kB, through modulation of the bioactive lipids controlled by its biochemical reaction, and that SMS is therefore a determinant for the development of cancer. RESULTS: In vivo biochemical characterization of SMS2 established that, under basal conditions, the golgi sub pool of SMS2 is active whereas still no evidence is collected on the activity of the plasma membrane localized SMS2 pool. Both SMS1 and SMS2 regulate NF-kB activity in a similar fashion and independently from IkB degradation. In transformed phenotypes such as chronic myelogeneous leukemia and SV40-transformation, the expression levels of SMS were increased. In the CML model the increase in SMS1 expression was not due to increased message stability suggesting an enhanced transcription. INTERPRETATION AND DIRECTION: The fact that SMSs seem to regulate NF-kB in a non classical mode, by-passing regulation by IkB, shed light and underlie the importance of an additional and still ill-studied step in the regulation of NF-kB. Therefore the significance of our results is two-fold: they establish NF-kB as a target for SMS1 and SMS2 activity, and they are starting to elucidate an additional level of regulation of NF-kB activity down-stream of IkB. Moreover, the fact that in different transformed phenotypes SMSs expression is elevated, and that in bcr-abl cells, modulation of SMS1 expression results in modulation of cellular viability, underscores the fact that elevated SMS activity might represent a requisite to favor cell transformation or survival perhaps in harmful conditions.

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。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。列出的机构适用于该中心，这不一定是调查员的机构。 SMS代表了一类重要的酶，负责鞘磷脂（SM）的生物合成，这是质膜的关键结构成分。此外，在其生化反应过程中，SMS还在相反的方向上调节了两种重要的生物活性脂质，神经酰胺和二酰基甘油（DAG）的水平，这些脂质（DAG）通常在控制关键细胞功能（例如繁殖和/或诱导细胞死亡）的关键细胞功能中起拮抗作用。最近，使用酵母表达系统的生化特征研究提出了两种酶SMS1和SMS2作为潜在的SMSS。此后不久，SMS1被证明可以介导哺乳动物细胞中的SM合成。 PI先前进行的研究表明，SM合成的激活以及NF-KB的激活（NF-KB（一种关键转录因子），参与细胞功能的调节，例如存活和炎症反应。我们在本项目的第1年获得的结果将SMS2表征为哺乳动物细胞中的SMS，因此表明SMS1和SMS2都能够在哺乳动物细胞中的SMS活性。此外，我们发现SMS2的敲除显着损害了基底因子和细胞因子以PKC独立的方式诱导NF-KB激活，因此抑制了NF-KB反应性基因的表达，例如环氧素酶2基因（COX-2）。基于SMS2在促进NF-KB激活中的潜在作用，并且由于NF-KB激活已被确定为促进癌症发展的关键因素，因此我们假设SMS通过对生物活性脂质的调节来调节Prosurvival转录因子NF-KB的激活，从而由其生物学脂质进行调节，从而由其生物化学反应进行了癌症，从而确定了癌症。结果：SMS2的体内生物化学表征确定，在基础条件下，Sms2的高尔基体子库是活性的，而仍未收集有关质膜局部sms2池活性的证据。 SMS1和SMS2都以类似的方式调节NF-KB活动，并且独立于IKB降解。在转化的表型中，例如慢性骨髓性白血病和SV40转化，SMS的表达水平增加。在CML模型中，SMS1表达的增加并不是由于消息稳定性提高表明转录增强。解释和方向：SMSS似乎以非经典模式调节NF-KB的事实，通过IKB的调节，散发出光线并构成了在NF-KB调节中的额外且仍未研究的一步的重要性。因此，我们结果的意义是两个方面：它们将NF-KB建立为SMS1和SMS2活性的目标，并且他们开始阐明IKB NF-KB活性下降的额外调节水平。此外，在不同转化的表型中SMS表达的事实升高，并且在BCR-ABL细胞中，SMS1表达的调节导致细胞活力的调节，强调了以下事实：升高SMS活性可能代表了在有害条件下可能有助于细胞转化或生存的必需品。