Studies on the regulatory mechanisms and the biological significance of metabolisms of membrane phospholipids in mammalian cells by using technics of biochemical genetics.

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This research was performed mainly by using technics of biochemical genetics with variants of mammalian cells concerning metabolisms of membrane phospholipids. 1. A CHO(Chinese hamster ovary)cell mutant with altered regulation of PS(phosphatidylserine)was isolated and the existence of a regulatory factor of PS biosynthesis was suggested. 2. Gene cloning of PS synthase I and PS decarboxylase was succeeded by using a variant defective in PS synthase I, and significance of the enzyme was suggested in regulation of PS and PE(phosphatidylethanolamine)synthesis and in growth and division of cells. 3. Further. importance of PS and PE in the membrane fusion was suggested by the experiment of Sindbis virus infection to this mutant. 4. A CHO variant defective in the Na' dependent inositol transport, which is an important process in phosphatidylinositol synthesis, was also isolated, and the presence of two inositol transport systems was suggested. 5. A temperature sensitive mutant with a defect in serine-parmitoyl transferase, the rate limiting enzyme of the synthesis of sphingolipids, was isolated from CHO cells, and sphingolipids were suggested essential in the mammalian cell growth. 6. A defective mutant of PG(phosphatidylglycerol)synthase was also isolated from CHO cells and importance of PG and cardiolipin in cellular growth was also suggested. 7. A resistant mutant to high concentrations of LPS(lipopolysaccharide)was isolated from J774.1 macrophage cells, and found a defect in both arachidonate release and O_2^- generation after LPS treatment. Further, regulatory pathways from phospholipases activation was suggested to be involved in the control of LPS-induced O_2^- generation by interferon gamma. 8. Importance of calmodulin in control of the membrane permeability with extra-cellular ATP was suggested. In mouse 3T3 cells, the expression of GLUT-1, a glucose transporter gene, by TGF-beta and an altered glycosylation of GLUT-1 protein were suggested.