Giraud F, Gascard P, Sulpice J C
Physiologie de la Nutrition, CNRS UA 646, Université Paris-Sud, France.
Biochim Biophys Acta. 1988 Mar 11;968(3):367-78. doi: 10.1016/0167-4889(88)90029-8.
Activation of protein kinase C in erythrocytes by 4-beta-phorbol 12-myristate 13-acetate (PMA) resulted in a parallel stimulation (time course and dose response) of the phosphorylation of both membrane proteins (heterodimers of 107 kDa and 97 kDa, protein 4.1 and 4.9, respectively) and of phosphatidylinositol 4-phosphate (PIP) and, to a lesser extent, of phosphatidylinositol 4,5-bisphosphate (PIP2). Evidence that the effect on lipid was mediated by protein kinase C activation and not by a direct action of PMA was provided by (1) the lack of effect of a phorbol ester that did not activate protein kinase C or of PMA addition on isolated membranes from control erythrocytes, (2) the reversal of the effect in the presence of protein kinase C inhibitors (alpha-cobrotoxin, H-7 (1-(5-isoquinolinesulfonyl)-2-methylpiperazine) or trifluoperazine). PMA treatment did not change the specific activity of ATP or the content of PIP2, but increased the content of PIP and decreased that of PI, indicating that the phosphorylation or dephosphorylation reactions linking PI and PIP were the target for the action of PMA. PMA treatment had no effect on the Ca2+-dependent PIP/PIP2 phospholipase C activity measured in isolated membranes. Mezerein, another protein kinase activator, had similar effects on both protein and lipid phosphorylation, when added with alpha-cobrotoxin. Activation of protein kinase A by cAMP also produced increases in phosphorylation, although quantitatively different from those induced by protein kinase C, in proteins and PIP. Simultaneous addition of PMA and cAMP at maximal doses resulted in only a partially additive effect on PIP labelling. These results show that inositol lipid turnover can be modulated by a protein kinase C and protein kinase A-dependent process involving the phosphorylation of a common protein. This could be PI kinase or PIP phosphatase or another protein regulating the activity of these enzymes.
4-β-佛波醇12-肉豆蔻酸酯13-乙酸酯（PMA）激活红细胞中的蛋白激酶C，导致膜蛋白（分别为107 kDa和97 kDa的异二聚体、蛋白4.1和4.9）以及磷脂酰肌醇4-磷酸（PIP）的磷酸化出现平行刺激（时间进程和剂量反应），对磷脂酰肌醇4,5-二磷酸（PIP2）的刺激程度较小。以下证据表明对脂质的影响是由蛋白激酶C激活介导的，而非PMA的直接作用：（1）不激活蛋白激酶C的佛波酯或向对照红细胞的分离膜中添加PMA均无作用；（2）在存在蛋白激酶C抑制剂（α-银环蛇毒素、H-7（1-（5-异喹啉磺酰基）-2-甲基哌嗪）或三氟拉嗪）的情况下，该效应会逆转。PMA处理未改变ATP的比活性或PIP2的含量，但增加了PIP的含量并降低了PI的含量，表明连接PI和PIP的磷酸化或去磷酸化反应是PMA作用的靶点。PMA处理对分离膜中测得的Ca2+依赖性PIP/PIP2磷脂酶C活性无影响。与α-银环蛇毒素一起添加时，另一种蛋白激酶激活剂肉豆蔻醇酯对蛋白质和脂质磷酸化具有类似作用。cAMP激活蛋白激酶A也会导致蛋白质和PIP的磷酸化增加，尽管在数量上与蛋白激酶C诱导的不同。以最大剂量同时添加PMA和cAMP对PIP标记仅产生部分相加效应。这些结果表明，肌醇脂质周转可通过蛋白激酶C和蛋白激酶A依赖性过程进行调节，该过程涉及一种共同蛋白质的磷酸化。这可能是PI激酶或PIP磷酸酶或另一种调节这些酶活性的蛋白质。
