The three main objectives of the proposed studies on assembly of CNS myelin are (1) characterization of the role of lipids in intracellular transport of myelin components, (2) characterization of the processing of myelin proteins between their synthesis and assembly into myelin, with emphasis on extra-myelin pools of proteolipid protein, and (3) further development of methods for isolation of Golgi-enriched fractions, and characterization of the role of the Golgi apparatus in processing of lipids and proteins destined for myelin. These studies are designed to increase our understanding of membrane biogenesis, and more specifically myelination, a major event in maturation of the nervous system. Brain slices from young rats will be used to examine the effects of various agents on transport of galactolipids, phospholipids, cholesterol and gangliosides to myelin. Agents to be studied include the Golgi-disrupting compounts monensin and Co++; the microtubule-binding agents colchicine and taxol; fenfluramine and propanolol, inhibitors of the synthesis of choline and ethanolamine phospholipids; and 20, 25 diazocholesterol, and inhibitor of cholesterol synthesis. The metabolism of extra-myelin pools of proteolipid protein will be examined with regard to long-term turnover, and accumulation in the presence of monensin. Effects of taxol and Co++ on transport of myelin proteins will be characterized. Golgi-enriched fractions will be further characterized and examined using immunoblot methodology and metabolic studies to determine whether myelin proteins are processed through Golgi membranes. Finally the possible role of proton gradients in intracellular transport of proteolipid protein will be examined by comparing the effects of monensin to the effects of chloroquine, a weak base which can raise intravesicular pH, and of selected ionophores such as nigericin.
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