Cytokine-Mediated Regulation of Cholesterogenesis

细胞因子介导的胆固醇生成调节

• 批准号: 6430095
• 负责人: ISHAIAHU SHECHTER
• 金额: $ 33.46万
• 依托单位: HENRY M. JACKSON FDN FOR THE ADV MIL/MED
• 依托单位国家: 美国
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-06-01 至 2006-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6430095
• 关键词: alkyltransferase; biological signal transduction; cholesterol; clinical research; cytokine; enzyme activity; genetic transcription; hamsters; interleukin 1; lipopolysaccharides; messenger RNA; phosphorylation; posttranslational modifications; protein degradation; protein localization; squalene; steroid biosynthesis; tissue /cell culture; transcription factor; tumor necrosis factor alpha

DESCRIPTION (provided by applicant): Squalene synthase (SQS) catalyzes the first reaction of the isoprenoid metabolic pathway committed to cholesterol biosynthesis and its activity regulates the flux of intermediates to sterols. SQS is regulated by sterols, lipopolysaccharide (LPS), and the pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-alpha) and interlukin-1-beta (IL-1-beta). Sterol-mediated transcriptional regulation of SQS is well understood, but little is known about the mechanism of its regulation during the inflammatory response. We propose to test the hypothesis that LPS and cytokines regulate SQS mRNA transcription and stability and enzyme protein posttranslational modification, stability and subcellular localization. In Specific Aim 1 we will determine the effects of LPS and cytokines on hepatic SQS transcription and mRNA stability in Syrian hamsters fed with different cholesterogenic diets. We will also determine changes in SQS mRNA level and size during response to cytokines and the contribution of the specific cytokines to these processes. In Specific Aim 2 we propose to elucidate the molecular mechanisms responsible for SQS mRNA regulation by LPS and cytokines. This will be achieved, in cultured cells, by examining promoter sequence elements responsible for the transcriptional repression by cytokines, by identification of transcription factors involved in this suppression, and by the elucidation of cellular signaling pathways involved in the transcriptional regulation. In addition, sequences required for SQS mRNA destabilization by cytokines will be localized. In Specific Aim 3 we propose to elucidate the LPS-and cytokine-induced, post-translational mechanisms underlying the decrease in SQS enzymic activity. We will examine SQS protein destabilization, mechanisms for its degradation, post-translational modification by phosphorylation, and change in its subcellular localization in response to LPS and cytokines. Achievement of the three Specific Aims will contribute directly to our long-term goal to elucidate the importance of SQS regulation on isoprenoid metabolic flux. It will increase our understanding of sterol metabolism in acute phase response (APR) to infection and inflammation and the role of SQS regulation in this process. Finally, it will enhance our overall understanding of hepatic cholesterol production in normal and pathological situations.

描述（由申请人提供）：角鲨烯合酶（SQS）催化 类异戊二烯代谢途径的第一个反应是胆固醇 生物合成及其活性调节中间体到甾醇的通量。 SQS 受甾醇、脂多糖 (LPS) 和促炎物质调节 细胞因子 肿瘤坏死因子-α (TNF-α) 和白细胞介素-1-β （IL-1-β）。甾醇介导的 SQS 转录调控效果良好 已被理解，但对其调控机制知之甚少。 炎症反应。我们建议检验 LPS 和 细胞因子调节 SQS mRNA 转录和稳定性以及酶蛋白 翻译后修饰、稳定性和亚细胞定位。在 具体目标 1 我们将确定 LPS 和细胞因子对肝脏的影响 饲喂不同饲料的叙利亚仓鼠的 SQS 转录和 mRNA 稳定性 胆固醇饮食。我们还将确定 SQS mRNA 水平的变化和 对细胞因子反应期间的大小以及特定的贡献 细胞因子参与这些过程。在具体目标 2 中，我们建议阐明 LPS 和细胞因子调节 SQS mRNA 的分子机制。 这将在培养细胞中通过检查启动子序列来实现 负责细胞因子转录抑制的元件， 鉴定参与这种抑制的转录因子，并通过 阐明参与转录的细胞信号通路 规定。此外，SQS mRNA 不稳定所需的序列 细胞因子将被定位。在具体目标 3 中，我们建议阐明 LPS 和 细胞因子诱导的翻译后机制导致 SQS 酶活性。我们将研究 SQS 蛋白不稳定的机制 其降解、磷酸化翻译后修饰，以及 其亚细胞定位响应 LPS 和细胞因子而发生变化。 这三个具体目标的实现将直接有助于我们 阐明 SQS 监管对类异戊二烯的重要性的长期目标 代谢通量。它将增加我们对甾醇代谢的了解 对感染和炎症的急性期反应 (APR) 以及 SQS 的作用 这个过程中的监管。最后，它会增强我们的整体理解 正常和病理情况下肝脏胆固醇产生的影响。