GLYCOSPHINGOLIPID METABOLISM AND MENTAL RETARDATION

广泛的长期目标是了解糖脂的作用 （糖鞘脂（GSL）和肌醇磷酸甘油酯）在正常神经 功能和致病过程涉及他们导致精神 迟钝 为了实现这一目标，我们将使用培养的细胞， 神经特异性（神经元，神经瘤或杂交细胞系， 少突胶质细胞）或遗传性代谢缺陷（成纤维细胞）， 结合代谢研究、酶测定、特异性抗体， 特异性蛋白质的cDNA转染。 两个主要的具体目标是： 1)为了了解受体是如何与 磷脂酶C（PLC）和磷酸肌醇的水解，以及如何这 系统由蛋白激酶A、蛋白激酶C、糖脂和 衍生的游离鞘氨醇碱。 a）我们将专注于低分子量 GTP结合蛋白如rap 1b，它们的周转，磷酸化， 与受体和PLC的膜缔合和偶联。 我们将研究 三种细胞系，其中受体-PLC偶联似乎受到调节 分别为NCB-20、WEHI-3和人少突胶质细胞瘤细胞。 B） 我们将确定鞘氨醇的活性，以及它们如何 生理上调节PK-C和PLC活性，以及它们的再表达是如何进行的。 棕榈酰化可能与生物活性物质的酰化/脱酰化有关。 GAP-43等蛋白质。 2)为了阐明鞘糖脂在某些细胞凋亡机制中的作用， 神经细胞损伤的类型。 a）我们将研究新生大鼠的缺氧 少突胶质细胞，因为缺氧最初限制O2为2-羟基脂肪酸 酸性GSL合成和消耗ATP水平足以破坏间 关键髓鞘蛋白质的细胞器易位和磷酸化。 B） 由于抗GM 1、GM 2和GD 1b抗体在人体中的高滴度似乎 选择性地破坏运动神经元-肌肉突触接触， 神经元疾病，我们将研究神经节苷脂在调节Ca 2+， 第二信使和突触发生。 （三）我们将确定 在β-Hex基因突变的患者中， GM 2-神经节苷脂降解酶N-乙酰-β-D-氨基葡萄糖苷酶（β-Hex） 为了更好地了解beta-Hex，酶如何降解GSL， 如何设计出更好的治疗方法

The broad, long-term objectives are to understand the role of glycolipids (glycoshingolipids (GSL) and inositolphosphoglycerides) in normal nervous function and the pathogenic processes involving them which lead to mental retardation. To achieve this goal we will use cultured cells which express either neural-specific properties (neurons, neurotumor hybrid cell lines, oligodendrocytes), or inherited metabolic defects (fibroblasts), in conjunction with metabolic studies, enzyme assays, specific antibodies, and cDNA transfection of specific proteins. The two major Specific Aims are: 1) To understand how receptors are coupled to the activation of phospholipase C (PLC) and the hydrolysis of phosphoinositides, and how this system is regulated by protein kinase A, protein kinase C, glycolipids and derived free sphingosine bases. a) We will focus on low molecular weight GTP-binding proteins such as rap1b, their turnover, phosphorylation, membrane association and coupling to receptors and PLC. We will study three cell lines in which receptor-PLC coupling seems to be regulated differently, namely NCB-20, WEHI-3 and human oligodendroglioma cells. b) We will determine how sphingosines activity, and how they could physiologically regulate both PK-C and PLC activity, and how their re- palmitoylation could be related to the acylation/deacylation of bioactive proteins such as GAP-43. 2) To elucidate the role of glycosphingolipids in the mechanism of certain types of neural cell injury. a) We will study hypoxia in neonatal rat oligodendrocytes since hypoxia initially restricts O2 for 2-hydroxy fatty acid GSL synthesis and depletes ATP levels sufficiently to disrupt inter- organellar translocation and phosphorylation of key myelin proteins. b) Since high titers of anti-GM1, GM2, and GD1b antibodies in humans appear to selectively destroy motor neuron-muscle synaptic contacts and cause motor neuron disease, we will study the role of gangliosides in regulating Ca2+, second messengers and synaptogenesis. c) We will determine the point mutations in the beta-Hex gene in patients with partial deficiency of the GM2-ganglioside degrading enzyme N-acetyl-beta-D-glucosaminidase (beta-Hex) in order to understand more about beta-Hex, how enzymes degrade GSL, and how better remedial therapy might be designed.