Kolesnick R N
Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, New York 10021.
J Biol Chem. 1987 Oct 25;262(30):14525-30.
Phorbol esters have been shown to stimulate phosphatidylcholine synthesis via the CDP-choline pathway. The present study compares the effects of phorbol esters and thyrotropin-releasing hormone (TRH) on phosphatidylcholine metabolism in GH3 pituitary cells. In a previous study (Kolesnick, R.N., and Paley, A.E. (1987) J. Biol. Chem. 262, 9204-9210), the potent phorbol ester, 12-O-tetradecanoylphorbol 13-acetate (TPA) induced time- and concentration-dependent incorporation of 32Pi and [3H]choline into phosphatidylcholine in short-term labeling experiments. In this study, TPA is shown to activate choline-phosphate cytidylyltransferase (EC 2.7.7.15), the regulatory enzyme of the CDP-choline pathway, by stimulating redistribution of the inactive cytosolic form of the enzyme to the membrane. Redistribution was quantitative. TPA reduced cytosolic activity from 3.5 +/- 0.4 to 1.5 +/- 0.3 nmol . min-1 x 10(7) cells-1 and enhanced particulate activity from 2.5 +/- 0.4 to 4.9 +/- 0.6 nmol . min-1 x 10(7) cells-1. TRH also stimulated time- and concentration-dependent 32Pi and [3H]choline incorporation into phosphatidylcholine. An increase was detectable after 5 min; and after 30 min, the levels were 164 +/- 9 and 150 +/- 11% of control, respectively; EC50 congruent to 2 X 10(-10) M TRH. These events correlated directly with TRH-induced 32Pi incorporation into phosphatidylcholine. TRH also stimulated redistribution of cytidylyl-transferase specific activity. TRH reduced cytosolic activity 45% and enhanced particulate activity 51%. Neither TRH nor TPA stimulated phosphatidylcholine degradation. In cells down-modulated for protein kinase C (Ca2+/phospholipid-dependent protein kinase), the effects of TPA and TRH on 32Pi incorporation into phosphatidylcholine were abolished. However, TRH-induced incorporation into phosphatidylinositol still occurred. These studies provide evidence that hormones may regulate phosphatidylcholine metabolism via the protein kinase C pathway.
佛波酯已被证明可通过CDP - 胆碱途径刺激磷脂酰胆碱的合成。本研究比较了佛波酯和促甲状腺激素释放激素（TRH）对GH3垂体细胞中磷脂酰胆碱代谢的影响。在先前的一项研究中（科尔斯尼克，R.N.，和佩利，A.E.（1987年）《生物化学杂志》262，9204 - 9210），强效佛波酯12 - O - 十四酰佛波醇13 - 乙酸酯（TPA）在短期标记实验中诱导了32Pi和[3H]胆碱向磷脂酰胆碱的时间和浓度依赖性掺入。在本研究中，TPA被证明可通过刺激该酶无活性的胞质形式重新分布到膜上，从而激活CDP - 胆碱途径的调节酶胆碱磷酸胞苷转移酶（EC 2.7.7.15）。这种重新分布是定量的。TPA将胞质活性从3.5±0.4降至1.5±0.3 nmol·min-1×10(7)个细胞-1，并将微粒体活性从2.5±0.4提高到4.9±0.6 nmol·min-1×10(7)个细胞-1。TRH也刺激了32Pi和[3H]胆碱向磷脂酰胆碱的时间和浓度依赖性掺入。5分钟后可检测到增加；30分钟后，水平分别为对照的164±9%和150±11%；TRH的EC50约为2×10(-10) M。这些事件与TRH诱导的32Pi掺入磷脂酰胆碱直接相关。TRH还刺激了胞苷转移酶比活性的重新分布。TRH使胞质活性降低45%，微粒体活性提高51%。TRH和TPA均未刺激磷脂酰胆碱的降解。在蛋白激酶C（Ca2+/磷脂依赖性蛋白激酶）下调的细胞中，TPA和TRH对32Pi掺入磷脂酰胆碱的影响被消除。然而，TRH诱导的掺入到磷脂酰肌醇中的现象仍然发生。这些研究提供了证据，表明激素可能通过蛋白激酶C途径调节磷脂酰胆碱的代谢。
