期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1981
卷号：78
期号：10
页码：6176-6180
DOI：10.1073/pnas.78.10.6176
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Variants of the rat basophilic leukemia (RBL) cell line were isolated and screened for phospholipid methyltransferase I and II activities, enzymes that convert phosphatidylethanolamine to phosphatidylcholine. Two variants were found that had decreased phospholipid methyltransferase enzyme levels and were unable to cause an influx of Ca2+ or release histamine in an IgE-mediated reaction. However, these cells were able to release histamine through an ionophore-induced reaction, indicating that the releasing mechanism distal to the Ca2+ channel was intact. One cell line, 1C1.B1, had low specific activity for phospholipid methyltransferase I. A second variant, 2H3.B6, had reduced phospholipid methyltransferase II activity. Although both variants were unable to incorporate label from [methyl-3H]methionine or [3H]serine into phosphatidylcholine, they were able to incorporate [methyl-3H]choline and myo-[2-3H(N)]inositol into phospholipids. Fusion of the two cell lines and isolation on selective media resulted in the growth of eight independent hybrids. All eight had an increased number of chromosomes and normal phospholipid methyltransferase activities. Stimulation of the hybrids with IgE resulted in CA2+ influx and histamine release. These results indicate that phospholipid methylation precedes and is necessary for Ca2+ influx, and they further support the hypothesis that methylation is a necessary early step in the IgE-mediated histamine release reaction in RBL cells.
