Sphingolipid Biology And Disease

鞘磷脂是细胞信号通路的关键介体和调节者。我们的研究主要集中在以鞘糖脂(GSLS)和鞘氨醇-1-磷酸(S1P)为代表的两类鞘磷脂的作用上。我们的工作旨在定义这些鞘脂的正常功能，并了解它们在疾病过程中的作用。 GSLs存在于细胞膜的外叶，集中在特殊的信号结构中。它们尤其以神经节苷脂(含唾液酸的GSLS)的形式存在于神经细胞中。通过对编码GSLS合成酶的基因的遗传破坏，我们创造了一系列表达有限糖鞘糖脂结构的小鼠。我们正在使用这些小鼠来发现GSLS的功能。当负责GSL降解的细胞机制出现缺陷时，GSL储存病就会导致严重的神经变性。例如泰-萨克斯病、桑德霍夫病和高谢病。 S1P是一种信号分子，对多种细胞事件的调节至关重要，包括细胞的存活、生长、分化和钙动员。近年来，对S1P的大量研究表明，S1P通过G蛋白偶联受体(GPCRs)家族在心血管系统发育和免疫中发挥重要作用，被命名为S1P1-5。 1.我们发现S1P在神经发育中也起着关键作用，可能是通过S1P1受体介导的。我们发现，在小鼠中同时破坏这两个已知的鞘氨酸激酶基因会导致S1P缺乏，从而干扰血管生成，导致神经管闭合缺陷，随后导致胚胎死亡。在这些突变胚胎发育中的神经系统中，细胞凋亡显著增加，有丝分裂显著减少。因此，S1P加入了越来越多的信号分子，如血管内皮生长因子，这些分子调节着血管生成和神经发生的功能交织的途径。我们的发现不仅提供了对S1P信号的新的生物学见解，还表明利用这一途径可能会导致开发新的神经疾病治疗方法。 2.我们现在已经在带有loxP位点的小鼠身上建立了一个UGcg等位基因。当cre重组酶在Nestin启动子作用下在神经系统中表达时，Flobled基因发生重组，导致UGcg的表达和神经节苷脂糖脂系列的水平显著降低。神经系统中缺乏UGcg的小鼠表现出浦肯野细胞的显著丧失和异常的神经行为。UGCG等位基因有助于分析神经鞘糖脂在正常生理状态下以及糖尿病和癌症等疾病中的功能。

Sphingolipids are key mediators and regulators of cell signaling pathways. Our studies have focused on the actions of two classes of sphingolipids represented by glycosphingolipids (GSLs) and sphingosine-1-phosphate (S1P). Our work is aimed at defining the normal functions of these sphingolipids and understanding their roles in disease processes. GSLs are found in the outer leaflet of the plasma membrane and are concentrated in specialized signaling structures. They are particularly abundant in neuronal cells in the form of gangliosides (sialic acid containing GSLs). Through genetic disruption of genes that encode synthetic enzymes for GSLs, we have created a series of mice that express limited glycosphingolipid structures. We are using these mice to discover the functions of GSLs. When the cellular machinery responsible for GSL degradation is defective, GSL storage diseases result in which profound neurodegeneration occurs. Examples are Tay-Sachs, Sandhoff and Gaucher diseases. S1P is a signaling molecule that is crucial for the regulation of several diverse cellular events, including cell survival, growth, differentiation and calcium mobilization. Recently, numerous studies on S1P have demonstrated its importance in the development of the cardiovascular system and immunity through a family of G protein-coupled receptors (GPCRs), designated S1P1-5. 1. We have shown that S1P also plays a key role in neural development, probably mediated by the S1P1 receptor. We found that simultaneous disruption of the two known sphingosine kinase genes in mice results in a deficiency of S1P, which disturbed angiogenesis and caused neural tube closure defects, followed by embryonic lethality. Dramatic increases in apoptosis and decreases in mitosis were seen in the developing nervous systems of these mutant embryos. Thus, S1P joins a growing list of signaling molecules, such as vascular endothelial growth factor, which regulate the functionally intertwined pathways of angiogenesis and neurogenesis. Our findings not only provide new biological insights into S1P signaling, but also suggest that exploitation of this pathway could lead to the development of novel therapeutic approaches for neurological disease. 2. We have now established a Ugcg allele in mice flanked by loxP sites (floxed). When cre recombinase was expressed in the nervous system under the Nestin promoter, the floxed gene underwent recombination, resulting in a substantial reduction of Ugcg expression and of glycosphingolipid ganglio-series levels. The mice lacking Ugcg in the nervous system show a striking loss of Purkinje cells and abnormal neurologic behavior. The floxed Ugcg allele will facilitate the analysis of the function of glycosphingolipids in normal physiology and in diseases such as diabetes and cancer.