Nuclear sphingolipid metabolism in regulation of myogenesis

鞘脂（SL）是膜的基本结构组分，并为关键的细胞膜提供储存库。 生物活性脂质，包括神经酰胺和1-磷酸鞘氨醇（S1 P）。而神经酰胺与 随着细胞凋亡和生长停滞，S1 P通常促进存活和增殖。最好的- S1 P的特征性靶是定位于质膜的S1 P受体。S1 P也可以在 通过结合和抑制I类组蛋白脱乙酰酶（HDAC），这是主要的调节剂， 的基因表达。SL信号传导的特征在于高度区室化的产生和靶向 生物活性分子。对局部S1 P产生和靶向血浆的实质性见解 细胞膜上的SL代谢，但对细胞核内SL代谢的调控知之甚少。这 该项目涉及在细胞核中产生生物活性SL的潜在作用的蛋白质的研究。 这项工作包括分析定位于核膜（NE）的中性鞘磷脂酶， 成肌细胞分化所需的，这可能是不可或缺的核SL代谢。该部件和 将在培养的成肌细胞中分析与核SL代谢有潜在联系的其他酶 分化模型亚细胞分级和脂质组学将被用来表征这些作用， 在成肌细胞分化过程中调节细胞核动态SL景观的蛋白质， 产生包括S1 P的生物活性SL。此外，S1 P在激活表达中的潜在功能可能是 将评估肌源性基因作为I类HDAC的抑制性配体的作用。总体而言，该项目将 研究假设，即细胞核容纳一个独特的SL代谢，具有重要作用， 肌源性分化这项工作与人类的肌肉病理学有明显的相关性，因为HDAC 包括S1 P在内的抑制剂已经显示出改善动物模型中的肌营养不良。

Sphingolipids (SLs) are essential structural components of membranes and provide reservoirs for critical bioactive lipids, including ceramide and sphingosine 1-phosphate (S1P). Whereas ceramide is associated with apoptosis and growth arrest, S1P commonly promotes survival and proliferation. The best- characterized targets of S1P are S1P receptors localized to the plasma membrane. S1P also can act in the nucleus by binding to and inhibiting class I histone deacetylases (HDACs), which are major regulators of gene expression. SL signaling is characterized by highly compartmentalized generation and targeting of the bioactive molecules. Substantial insight on localized S1P production and targeting at the plasma membrane has been obtained, but little is known about regulation of SL metabolism in the nucleus. This project involves investigation of proteins with potential roles in generating bioactive SLs in the nucleus. The work includes analysis of a neutral sphingomyelinase localized to the nuclear envelope (NE) that is required for myoblast differentiation, which may be integral to nuclear SL metabolism. This component and other enzymes with potential links to nuclear SL metabolism will be analyzed in a cultured myoblast differentiation model. Subcellular fractionation and lipidomics will be used to characterize the role of these proteins in regulating the dynamic SL landscape of the nucleus during myoblast differentiation, and in producing bioactive SLs including S1P. In addition, the potential functions of S1P in activating expression of myogenic genes as an inhibitory ligand for class I HDACs will be evaluated. Overall this project will investigate the hypothesis that the nucleus houses a distinctive SL metabolism that has a major role in myogenic differentiation. The work has clear relevance to muscle pathology in humans, since HDAC inhibitors including S1P have been shown to ameliorate muscular dystrophies in animal models.