title: Isolation and characterization of a Chinese hamster ovary cell mutant with altered regulation of phosphatidylserine biosynthesis.
abstract: We have screened approximately 10,000 colonies of Chinese hamster ovary (CHO) cells immobilized on polyester cloth for mutants defective in [14C]ethanolamine incorporation into trichloroacetic acid-precipitable phospholipids. In mutant 29, discovered in this way, the activities of enzymes involved in the CDP-ethanolamine pathway were normal; however, the intracellular pool of phosphorylethanolamine was elevated, being more than 10-fold that in the parental CHO-K1 cells. These results suggested that the reduced incorporation of [14C]ethanolamine into phosphatidylethanolamine in mutant 29 was due to dilution of phosphoryl-[14C]ethanolamine with the increased amount of cellular phosphorylethanolamine. Interestingly, the rate of incorporation of serine into phosphatidylserine and the content of phosphatidylserine in mutant 29 cells were increased 3-fold and 1.5-fold, respectively, compared with the parent cells. The overproduction of phosphorylethanolamine in mutant 29 cells was ascribed to the elevated level of phosphatidylserine biosynthesis, because ethanolamine is produced as a reaction product on the conversion of phosphatidylethanolamine to phosphatidylserine, which is catalyzed by phospholipid-serine base-exchange enzymes. Using both intact cells and the particulate fraction of a cell extract, phosphatidylserine biosynthesis in CHO-K1 cells was shown to be inhibited by phosphatidylserine itself, whereas that in mutant 29 cells was greatly resistant to the inhibition, compared with the parental cells. As a conclusion, it may be assumed that mutant 29 cells have a lesion in the regulation of phosphatidylserine biosynthesis by serine-exchange enzyme activity, which results in the overproduction of phosphatidylserine and phosphorylethanolamine as well.
authors.affiliation: Department of Chemistry, National Institute of Health, Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Hasegawa
authors.forename: O
authors.initials: O
authors.lastname: Kuge
authors.forename: M
authors.initials: M
authors.lastname: Nishijima
authors.forename: Y
authors.initials: Y
authors.lastname: Akamatsu
mesh_terms: D000818:Animals; D002250:Carbon Radioisotopes; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D019856:Ethanolamine; D004983:Ethanolamines / Q000378:metabolism; D005260:Female; D006706:Homeostasis; D007700:Kinetics; D009154:Mutation; D010053:Ovary; D010718:Phosphatidylserines / Q000378:metabolism*; D011865:Radioisotope Dilution Technique; D014316:Tritium
chemical_list: D002250:Carbon Radioisotopes; D004983:Ethanolamines; D010718:Phosphatidylserines; D014316:Tritium; D019856:Ethanolamine