Characterization of Mammalian Ceramide Synthases

描述（由申请人提供）：神经酰胺（Cer）由鞘氨醇碱和酰胺连接脂肪酸组成，是复杂鞘脂的骨架，也是重要细胞过程的调节剂。近年来，很明显，哺乳动物组织中含有许多不同的Cer亚类，并且形成这些重要化合物的酶对脂肪酰辅酶A底物具有高度选择性，但它们对鞘氨醇碱的选择性尚未完全确定。因此，该基金的总体目标是提供对Cer酶（CerS），其在调节鞘氨醇碱和Cer代谢中的作用以及新型代谢物的功能的更基本和完整的理解。该研究的一个主要目标是阐明两个最近发现的1-脱氧-和1-脱氧甲基-鞘氨醇碱作为骨架的生物合成和周转途径，以及它们的一些生物学功能（目的1）。当丝氨酸棕榈酰转移酶利用丙氨酸或甘氨酸代替丝氨酸时，这些化合物被制备，并且已经发现至少一种已知的疾病-人类感觉神经病1型，HSN 1-是由1-脱氧鞘氨醇（主要作为下游代谢物1-脱氧二氢Cer存在）的产生增加引起的。对这一提议的初步研究已经确定，这些替代类别的鞘脂的生产比以前认识到的要普遍得多，并且将确定影响其生物合成的因素。CerS的表征还将确定负责产生特定Cer亚种的酶、解释这种选择性的酶的结构特征，并确定它们的活性如何受到同二聚体和异二聚体形成的影响（目的2）。这些研究将利用“脂质组学”质谱法进行鞘脂分析，因为该技术不仅提供了有关单个分子亚种的信息，还提供了有关其他分支和代谢物的信息。因此，该提案的目标3将评估不同分支和代谢物之间的“串扰”，并为为什么在血浆和组织中发现不同的亚种分布提供综合解释。由于许多鞘氨醇碱和Cer的亚种与遗传性和获得性疾病有关，这些研究将提供Cer代谢的基本图谱，这将有助于理解这些过程，并有助于制定更合理的干预策略。

DESCRIPTION (provided by applicant): Ceramides (Cer) are comprised of a sphingoid base and amide-linked fatty acid, and are the backbones of complex sphingolipids as well as modulators of vital cellular processes. In recent years, it has become evident that mammalian tissues contain many different subcategories of Cer, and that the enzymes that form these important compounds are highly selective with respect to the fatty acyl-CoA substrate, but their selectivities for the sphingoid base have not yet been fully defined. Therefore, the overall objective of this grant is to provide a more fundamental and complete understanding of Cer synthases (CerS), their roles in regulating sphingoid base and Cer metabolism, and functions of novel metabolites. A major goal of the research in this grant is to elucidate the pathways for the biosynthesis and turnover of two recently discovered 1-deoxy- and 1-desoxymethyl-sphingoid bases as the backbones, and some of their biological functions (Aim 1). These compounds are made when serine palmitoyltransferase utilizes alanine or glycine instead of serine, and at least one known disease-human sensory neuropathy type 1, HSN1--has been found to result from elevated production of 1-deoxysphinganine (present mainly as the downstream metabolite 1- deoxydihydroCer). Preliminary studies for this proposal have established that production of these alternative categories of sphingolipids is far more common than has been previously appreciated, and the factors that influence their biosynthesis will be identified. Characterization of the CerS will also establish which are responsible for production of particular Cer subspecies, structural features of the enzymes that account for this selectivity, and determine how their activity is influenced by formation of homo- and hetero- dimers (Aim 2). These studies will utilize "lipidomic" mass spectrometry for the sphingolipid analysis because this technology provides information about not only individual molecular subspecies but also for other branches and metabolites. Thus, Aim 3 of the proposal will evaluate "cross-talk" among the different branches and metabolites and provide a integrative explanation for why distinctive subspecies distributions are found in plasma and tissues. Since many of the subspecies of sphingoid bases and Cer have been implicated in inherited and acquired disease, these studies will provide the underlying map of Cer metabolism that will help these processes be understood, and assist in developing more rational strategies for intervention.