Cytokine-Mediated Regulation of Cholesterogenesis

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 生物合成和其活性调节中间体到甾醇的通量。 SQS受固醇、脂多糖（LPS）和促炎因子调节。 细胞因子肿瘤坏死因子-α（TNF-α）和白细胞介素-1-β （IL-1-β）。甾体介导的SQS转录调控是很好的 了解，但很少有人知道它的调节机制， 炎症反应。我们建议检验LPS和 细胞因子调节SQS mRNA转录和稳定性及酶蛋白 翻译后修饰、稳定性和亚细胞定位。在 具体目的1我们将确定LPS和细胞因子对肝细胞的影响， 叙利亚仓鼠中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， 在对细胞因子的反应过程中， 细胞因子对这些过程的影响。在具体目标2中，我们建议阐明 负责LPS和细胞因子对SQS mRNA调节的分子机制。 这将在培养的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， 参与转录的细胞信号通路的阐明 调控此外，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 精氨酸诱导的，翻译后机制的减少， SQS酶活性。我们将研究SQS蛋白的不稳定性， 用于其降解、通过磷酸化的翻译后修饰，以及 其亚细胞定位响应于LPS和细胞因子的变化。 实现这三个具体目标将直接有助于我们 长期目标是阐明SQS调节类异戊二烯的重要性 代谢通量它将增加我们对固醇代谢的理解， 感染和炎症的急性期反应（APR）以及SQS的作用 在这个过程中的监管。最后，它将增强我们的整体认识 在正常和病理情况下肝脏胆固醇的产生。

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.