Lipid hydroxylation in glial cell signaling and myelination

神经胶质细胞信号传导和髓鞘形成中的脂质羟基化

• 批准号: 7475369
• 负责人: HIROKO HAMA
• 金额: $ 28.74万
• 依托单位: MEDICAL UNIVERSITY OF SOUTH CAROLINA
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-04-01 至 2013-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7475369
• 关键词: 3-ketosphinganine; Acyl Coenzyme A; Adult; Affect; Alleles; Anabolism; Animal Model; Axon; Binding; Biochemical; Biochemistry; Biological Assay; Brain; CDKN1A gene; Carbohydrates; Carrier Proteins; Cell Cycle; Cell Cycle Regulation; Cell Differentiation process; Cell Surface Receptors; Cells; Ceramides; Characteristics; Complex; Cuprizone; Cyclic AMP; Cyclin-Dependent Kinases; Data; Demyelinating Diseases; Demyelinations; Development; Dihydrosphingosine; Disease; Dose; Electron Transport; Employee Strikes; Enzymes; Family; Fatty Acids; Feedback; Figs - dietary; Foundations; Galactolipids; Galactose; Galactosylceramides; Genes; Genetic Recombination; Goals; Head; Health; Human; Hydrogen Bonding; Hydroxylation; In Vitro; Integrins; Knock-out; Knockout Mice; Knowledge; Lead; Length; Lipids; Maintenance; Mass Fragmentography; Mediating; Membrane; Membrane Microdomains; Mixed Function Oxygenases; Modeling; Molecular; Molecular Conformation; Molecular Genetics; Morphology; Multiple Sclerosis; Mus; Myelin; N-acylsphingosine galactosyltransferase; Nature; Neural Conduction; Neuraxis; Neuregulin Receptor; Neurilemmoma; Neurodegenerative Disorders; Neuroglia; Numbers; Oligodendroglia; Palmitoyl Coenzyme A; Pathway interactions; Peripheral Nervous System; Personal Satisfaction; Physiological; Play; Positioning Attribute; Protein Isoforms; Proteins; Public Health; RNA Interference; Regulation; Role; Schwann Cells; Serine; Signal Transduction; Signaling Molecule; Solid; Sphingolipids; Stimulus; Structure; Substrate Specificity; Sulfoglycosphingolipids; Surface; Tamoxifen; Testing; Therapeutic Agents; Time; Tissues; Transcriptional Activation; Transcriptional Regulation; Transgenic Mice; Up-Regulation; Uridine Diphosphate Galactose; Vertebrates; Very Long Chain Fatty Acid; Withdrawal; base; brain tissue; cell motility; cofactor; dihydroceramide; dihydroceramide synthase; fatty acid elongases; galactolipid; hydroxyl group; in vivo; insight; long chain fatty acid; membrane model; mouse model; myelination; novel; oncoprotein p21; p27 Cell Cycle Protein; p27 Enzyme Inhibitor; protein expression; response; role model; transcription factor

DESCRIPTION (provided by applicant): In higher vertebrates, nerve conduction is greatly facilitated by myelin, a lipid-rich membrane that wraps around the axon. A number of devastating demyelinating diseases threat human health, and few effective treatments exist. To develop better treatment for these diseases, we must understand the mechanisms involved in myelination. Myelin is a specialized structure with distinct lipid and protein constituents. Galactosylceramide (GalCer) and sulfatide make up approximately 30% of total myelin lipids, and more than half of these galactolipids contain fatty acid with a hydroxyl group at the C2 position (2-OH galactolipids). No other mammalian tissues contain such high concentrations of 2-OH fatty acids, suggesting that 2-OH galactolipids may play a crucial role in creating the special characteristics of myelin. Despite the extraordinary abundance of 2-OH galactolipids in myelin, there is surprisingly little understanding of the basic biochemistry and physiological role of 2-OH galactolipids. The overall goal of this study is to elucidate the pathway for myelin 2-OH lipids and their roles in myelination, myelin function, and cell signaling. A recently identified fatty acid 2-hydroxylase, FA2H, provides the precursor for the synthesis of myelin 2- OH galactolipids in oligodendrocytes and Schwann cells. FA2H and other enzymes are responsible for the increase in 2-OH very-long-chain (>C20) fatty acid contents in galactolipids during myelination. The first aim of this project is to establish the biosynthetic pathway involved in the unique lipid compositions of myelin galactolipids. Extensive biochemical analyses of FA2H will be performed to determine its physiological substrate, cofactors, and potential feedback mechanisms. Isoforms of fatty acid elongases and dihydroceramide synthases will be identified by a molecular genetic approach. More recently, it was found that reduced FA2H expression via RNAi significantly enhanced motility of D6P2T cells. Cellular 2-OH also partially blocked the upregulation of cyclin-dependent kinase inhibitors, p21 and p27, in response to a stimulus for differentiation. These observations indicate that 2-OH lipids are not only major structural components of myelin, but also function as signaling molecules to modulate cell differentiation and motility. In the second aim, the mechanism of action of 2-OH lipids in cell differentiation and motility will be determined. Transcriptional regulation for p21 and p27 will be investigated to determine the target protein modulated by 2-OH lipids, and the molecular identity of 2-OH lipid species with signaling function will be determined. The third aim is to determine the role of 2-OH galactolipids in myelin function and remyelination in adult brain. The cuprizone- induced demyelination/remyelination will be used to show FA2H is involved in remyelination. Subsequently, newly available conditional FA2H-knockout mice will be used to inactivate FA2H in adult brain. This model will be used to investigate myelin morphology, function, and remyelination in the absence of 2-OH lipids. PUBLIC HEALTH RELEVANCE To develop better treatment for devastating demyelinating diseases, we must understand the mechanisms involved in myelination. This project seeks to unravel the complex pathways for the synthesis of myelin lipids and their roles in myelin maintenance and function, as well as in cell signaling that controls proper myelination. Results obtained from this study will aid in developing better therapeutic agents for neurodegenerative diseases, such as multiple sclerosis.

描述(申请人提供)：在高等脊椎动物中，髓鞘极大地促进了神经传导，髓鞘是一种包裹在轴突周围的富含脂质的膜。许多毁灭性的脱髓鞘疾病威胁着人类的健康，而且几乎没有有效的治疗方法。为了开发更好的治疗这些疾病的方法，我们必须了解髓鞘形成的机制。髓鞘是一种特殊的结构，具有不同的脂肪和蛋白质成分。半乳糖基神经酰胺(GalCer)和硫脂约占髓磷脂总量的30%，其中超过一半的半乳糖脂含有C2位带有羟基的脂肪酸(2-OH半乳糖脂)。没有其他哺乳动物组织含有如此高浓度的2-羟基脂肪酸，这表明2-羟基半乳糖脂可能在创造髓鞘的特殊特性中起着关键作用。尽管髓鞘中含有非常丰富的2-羟基半乳糖脂，但令人惊讶的是，人们对2-羟基半乳糖脂的基本生化和生理作用知之甚少。这项研究的总体目标是阐明髓鞘2-羟基类脂的途径及其在髓鞘形成、髓鞘功能和细胞信号转导中的作用。新发现的脂肪酸2-羟基酶FA2H为少突胶质细胞和雪旺细胞合成髓鞘2-羟基半乳糖脂提供了前体。FA2H和其他酶是在髓鞘形成过程中半乳糖脂中2-OH超长链(&GT；C20)脂肪酸含量增加的原因。本项目的第一个目标是建立髓鞘半乳糖脂独特的脂组成所涉及的生物合成途径。将对FA2H进行广泛的生化分析，以确定其生理底物、辅因子和潜在的反馈机制。脂肪酸伸长酶和二氢神经酰胺合成酶的异构体将通过分子遗传学方法进行鉴定。最近，人们发现通过RNAi降低FA2H的表达显著增强了D6P2T细胞的运动能力。细胞2-OH也部分阻断了细胞周期蛋白依赖的激酶抑制物p21和p27的上调，以响应分化刺激。这些观察表明，2-羟基脂类不仅是髓鞘的主要结构成分，而且还作为信号分子调节细胞的分化和运动。在第二个目标中，将确定2-羟基脂类在细胞分化和运动中的作用机制。将研究p21和p27的转录调控，以确定受2-羟基脂类调节的靶蛋白，并确定具有信号功能的2-羟基脂类的分子同一性。第三个目的是确定2-羟基半乳糖脂在成人大脑髓鞘功能和再髓鞘形成中的作用。铜酮诱导的脱髓鞘/再髓鞘形成将被用来表明FA2H参与了再髓鞘形成。随后，新获得的条件性FA2H基因敲除小鼠将被用来灭活成年大脑中的FA2H。这一模型将被用于研究髓鞘形态、功能和在没有2-羟基类脂的情况下的再髓鞘形成。为了开发更好的治疗破坏性脱髓鞘疾病的方法，我们必须了解髓鞘形成涉及的机制。该项目旨在揭示髓磷脂合成的复杂途径及其在髓鞘维持和功能中的作用，以及在控制适当的髓鞘形成的细胞信号中的作用。这项研究的结果将有助于开发更好的治疗神经退行性疾病的药物，如多发性硬化症。