Role of Protein Kinase C in Cellular Proliferation

蛋白激酶 C 在细胞增殖中的作用

基本信息

批准号：
01570154
负责人：
HASHIMOTO Eikichi
金额：
$ 1.41万
依托单位：
Fukui Medical School
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

项目摘要

It has been proposed that protein kinase C plays important roles in cell proliferation because this enzyme is activated by diacylglycerol transiently formed by phosphatidylinositol breakdown induced by various growth factors or by tumorpromoting phorbol esters. It has also been shown that protein kinase C is subjected to limited proteolysis and down regulation of this enzyme is induced during prolonged treatment of various cells with phorbol esters. In an attempt to understand the molecular mechanism of the down regulation of protein kinase C, we analyzed the proteolytic modification of this enzyme using the rat liver plasma membrane. Under higher ionic strength than physiological level (>140 mM NaCl) and slightly alkaline pH (7.5-8.0), proteaseーactivated form of protein kinase C with Mr. 50,000 was rapidly released from the membrane. The properties of this activated enzyme were essentially the same as those of protein kinase M (corresponding to the catalytic fragment of protein kinase C) reported earlir. Based on these results, we supposed that activation of Na^+/H^+ exchanger in plasma membrane may be a trigger for inducing the down regulation of protein kinase C, because Na^+ influx and cytoplasmic alkalinization are usually observed after activation of Na^+/H^+ exchanger by various extracellular stimuli. In contrast, higher molecular weight form of protein kinase C (Mr. 80,000) was generated from membrane under lower ionic strength condion. The activity of this enzyme was stimulated 2-fold by Ca2+ and phospholipid. This partially activated kinase was converted to a Ca2+-phospholipid-independent form by further digestion with trypsin without significant change in molecullar mass. However, the physiological significance of these proteolyzed enzymes with Mr. 80,000 is not clear at this time. Further detailed analyses of down regulation of protein kinase C seems to be important for understanding the role of protein kinase C in cell proliferation.

已经提出，蛋白激酶C在细胞增殖中起重要作用，因为该酶是由二酰基甘油通过各种生长因子或肿瘤增强的磷脂酯诱导的磷脂酰肌醇分解而瞬时形成的。还已经显示，蛋白激酶C受到有限的蛋白水解，并且在用磷脂酰肌醇的各种细胞长期处理过程中，诱导了该酶的调节。为了了解蛋白激酶C下降调节的分子机制，我们使用大鼠肝质膜分析了该酶的蛋白水解修饰。在比物理水平（> 140 mM NaCl）和稍碱性pH（7.5-8.0）的高离子强度下，蛋白质激活形式的蛋白激活形式与50,000先生的蛋白激酶C迅速从膜中迅速释放。该活化酶的特性基本与蛋白激酶M的特性相同（对应于蛋白激酶C的催化片段C）。基于这些结果，我们期望质膜中Na^+/H^+交换器的激活可能是诱导蛋白激酶C下降调节的触发因素，因为Na^+的影响和细胞质碱化通常在激活Na^+/H^+通过各种外细胞外细胞外刺激后观察到。相反，在较低的离子强度condion下，蛋白激酶C的较高分子量形式（80,000先生）产生。通过Ca2+和磷脂刺激该酶的活性2倍。通过胰蛋白酶进一步消化而没有明显变化的分子质量，将这种部分活化的激酶转化为Ca2+磷脂独立的形式。但是，目前尚不清楚这些蛋白水解酶与80,000先生的物理意义。对蛋白激酶C的降低调节的进一步详细分析对于理解蛋白激酶C在细胞增殖中的作用似乎很重要。