The long-term goal is to determine the factors which regulate the synthesis, transport and catabolism of glycolipids in nervous tissue and how this relates to various types of mental retardation. Glycolipids accumulate within lysosomes and destroy neurons in a group of inherited mental retardation syndromes known as the sphingolipidoses, but are also believed to play an important role in neural cell differentiation and function. It is proposed to complete studies on the biosynthesis and role of sialoglycosphingolipids (gangliosides) as modulators of an adenylate cyclase-linked receptor for serotonin (5HT) by purifying and reconstituting functional 5HT1 receptors. Neurotumor x central nervous system hybrid cell lines such as NCB-20 will be used to study the consequences of glycolipid modulation of A-kinase such as protein phosphorylation of enzymes, ion channels and cytoskeletal proteins (e.g., synapsin). We propose to raise both polyclonal and monoclonal antibodies to 5HT1 receptors and use these in combination with monoclonal antibodies to GD3 and GD2 gangliosides to probe 5HT1 receptor structure, synthesis, assembly and turnover and its coupling to adenylate cyclase. This work is especially relevant in view of claims that AUTISM may result from an autoimmune disease involving 5HT1 receptors. Because of the importance of myelination to achievement of normal mental status, we will continue to study the regulation of glycolipid synthesis in sheep oligodendrocytes undergoing differentiation. Concomitant differentiation markers will include myelin basic protein and cyclic nucleotide phosphohydrolase which are phosphorylated by C-kinase and both C and A-kinase respectively. We will focus on the role of cyclic AMP, calcium (inositol triphosphate-C-kinase-mediated) calmodulin-C-kinase and corticosteroids in regulating glycolipid synthesis. Finally, we propose to continue studies on fibroblasts from patients with the inherited neurodegenerative glycolipid storage disease fucosidosis by using molecular probes to determine the types of synthetic or processing defects in different forms of fucosidosis.
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