Cholecystokinin stimulates the down-regulation of CTP:phosphocholine cytidylyltransferase in pancreatic acinar cells.
Cholecystokinin stimulates the down-regulation of CTP:phosphocholine cytidylyltransferase in pancreatic acinar cells.
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胆囊收缩素刺激胰腺腺泡细胞中 CTP：磷酸胆碱胞苷酰转移酶的下调。
DOI：
10.1074/jbc.270.3.1437
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
Williams,JA
中科院分区：
文献类型：
--
作者：
Groblewski,GE;Wang,Y;Ernst,SA;Kent,C;Williams,JA
已知用胆囊收缩素 (CCK) 刺激大鼠胰腺腺泡细胞会显着抑制 CTP：磷酸胆碱胞苷酰转移酶 (CT)，这是磷脂酰胆碱生物合成中的限速酶。对 32P 标记的腺泡细胞进行的 CT 免疫沉淀显示，CCK 处理也导致 CT 磷酸盐水平显着降低。 CCK 的效果在 60 分钟内达到最大，并且取决于浓度，EC50 为 800 pM。其他钙动员促分泌剂，如氨甲酰胆碱 (100 μM) 和铃蟾肽 (10 nM) 也分别将 CT 磷酸盐水平降低至对照的 20% 和 39%。用毒胡萝卜素和/或 12-O-十四烷酰佛波醇-13-乙酸酯处理细胞证实，增加细胞内 Ca2+ 和蛋白激酶 C 活化的组合对于降低磷酸化 CT 含量是必要的。相反，单独添加促胰液素 (10 nM) 或 8-(4-氯苯硫基)-cAMP (100 μM) 则没有效果。使用化合物 JMV-180 表明 CCK 通过 CCKA 受体的低亲和力状态发挥作用，降低 CT 磷酸盐水平。此外，CCK 引起的磷酸化 CT 降低可被磷酸酶抑制剂冈田酸 (3 μM) 和花萼蛋白 A (100 nM) 阻断。最后，全细胞裂解物的免疫印迹显示，CT 在 CCK 的作用下部分降解，这提供了一种新的机制，通过该机制，CT 酶活性在激素的作用下被抑制。此外，这种降解也被磷酸酶抑制剂阻断。这些数据表明，CT 本身或介导 CCK 诱导的蛋白酶激活的一些其他调节分子的去磷酸化可能在降低腺泡细胞中 CT 酶水平方面发挥核心作用。
Stimulation of rat pancreatic acinar cells with cholecystokinin (CCK) is known to result in a significant inhibition of CTP:phosphocholine cytidylyltransferase (CT), a rate-limiting enzyme in phosphatidylcholine biosynthesis. Immunoprecipitation of CT from 32P-labeled acinar cells revealed that CCK treatment also caused a marked reduction in CT phosphate levels. The effects of CCK were maximal over 60 min and dependent on concentration, exhibiting an EC50 of 800 pM. Other calcium mobilizing secretagogues such as carbamylcholine (100 μM) and bombesin (10 nM) also reduced CT phosphate levels to 20 and 39% of control, respectively. Treatment of cells with thapsigargin and/or 12-O-tetradecanoylphorbol-13-acetate established that a combination of increased intracellular Ca2+ and protein kinase C activation was necessary to decrease phosphorylated CT content. Conversely, secretin (10 nM) or 8-(4-chlorophenylthio)-cAMP (100 μM) added alone had no effects. Use of the compound JMV-180 indicated CCK was acting through the low affinity state of the CCKAreceptor to reduce CT phosphate levels. Further, the decrease in phosphorylated CT caused by CCK was blocked by the phosphatase inhibitors okadaic acid (3 μM) and calyculin A (100 nM). Finally, immunoblotting from whole cell lysates revealed CT was partially degraded in response to CCK, providing a novel mechanism by which the inhibition of CT enzyme activity occurs in response to the hormone. Moreover, this degradation was also blocked by a phosphatase inhibitor. These data suggest that the dephosphorylation of either CT itself or some other regulatory molecule(s) which mediates the CCK-induced protease activation may play a central role in reducing CT enzyme levels in acinar cells.