Hack N, Clayman P, Skorecki K
Toronto General Hospital, Canada.
Biosci Rep. 1990 Aug;10(4):353-62. doi: 10.1007/BF01117235.
We have previously demonstrated phospholipase C (PLC) independent activation of phospholipase A2(PLA2) by epidermal growth factor (EGF) in glomerular mesangial cells in culture. In the current study using glass beads to permeabilize [3H]- or [14C]-arachidonate labelled mesangial cells we demonstrate that guanine nucleotides modulate the EGF-mediated stimulation of arachidonic acid release (75% inhibition with 100 microM GDP beta S and 108% augmentation with 100 microM GTP gamma S). GTP gamma S alone stimulated both the release of free arachidonic acid and production of diacylglycerol (DAG), while EGF itself neither stimulated DAG nor augmented the DAG response to GTP gamma S. These findings suggest the intermediacy of a G-protein in PLC-independent stimulation of PLA2 by a growth factor, and provide a model system for determining the relationship between G-protein intermediacy and the intrinsic tyrosine kinase activity of the growth factor receptor.
我们先前已证实在培养的肾小球系膜细胞中，表皮生长因子（EGF）可通过磷脂酶C（PLC）非依赖性途径激活磷脂酶A2（PLA2）。在当前研究中，我们使用玻璃珠使[3H] - 或[14C] - 花生四烯酸盐标记的系膜细胞透化，结果表明鸟嘌呤核苷酸可调节EGF介导的花生四烯酸释放（100μM GDPβS可抑制75%，100μM GTPγS可增强108%）。单独使用GTPγS可刺激游离花生四烯酸的释放和二酰基甘油（DAG）的产生，而EGF本身既不刺激DAG，也不增强DAG对GTPγS的反应。这些发现提示在生长因子通过PLC非依赖性途径刺激PLA2的过程中，存在一种G蛋白作为中间介质，并且为确定G蛋白中间介质与生长因子受体的内在酪氨酸激酶活性之间的关系提供了一个模型系统。
