Mechanism of down-regulation of protein kinase C and its implications in signal transduction

蛋白激酶C下调机制及其对信号转导的影响

基本信息

批准号：
03454155
负责人：
SUZUKI Koichi
金额：
$ 4.29万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

项目摘要

To clarify the mechanism of down-regulation of protein kianse C, and its implication in cellular signal transduction, studies on calpain and protein kinase C (PKC) were performed. Calpain and PKC translocate simultaneously to the biological membrane upon binding calcium ions when the cell surface receptor is activated by ligands and intracellular calcium concentrations increase. PKC is activated at the membrane in the presence of calcium by diacylglycerol and phospholipids. Calpain is also activated at the membrane autocatalytically in the presence of calcium and phosphatidylinositol-4,5- bisphosphate. Activated calpain acts on activated PKC and hydrolyzes bonds between the N-terminal regulatory domain and the C-terminal kinase domain to give an active fragment of PKC which is active without cofactors. Calpain recongnizes only the active and phosphorylated species and inactive PKC is not hydrolyzed. The role of the active fragment is not clear yet. It may be an intermediate of degradation or have some physiological function in transduction of signal from the membrane to the nucleus.Calpain hydrolyzes transcription factors, such as c-Jun and c-Fos, leading to down-regulation of cellular signals induced by activation of receptors. Activation of calpain stops the cellular signal transduction pathway at least by hydrolyzing PKC and transcription factors.Activated calpain is very unstable and presumably used only once. The calpain gene is a phorbol ester responsive gene and its transcription is induced by treatment of cells by various stimuli, such as growth factors, phorbol ester, etc. Newly synthesized calpain refills the calpain pool used to down-regulate signal transduction.

为了阐明蛋白质C下调的机理及其在细胞信号转导中的含义，进行了对钙蛋白酶和蛋白激酶C（PKC）的研究。当结合钙离子被配体激活细胞表面受体时，钙蛋白酶和PKC在结合钙离子后同时转移到生物膜上，细胞内钙浓度增加。在二酰基甘油和磷脂存在钙的情况下，在膜上激活PKC。在存在钙和磷脂酰肌醇-4,5-双磷酸盐的情况下，在膜自催化的钙蛋白酶也被激活。活性钙蛋白酶作用于活化的PKC并在N末端调节结构域和C-末端激酶结构域之间水解键，从而产生PKC的活跃片段，而PKC的活跃片段，而没有辅因子。 Calpain仅将活性和磷酸化的物种和非活性PKC重新处理。活动片段的作用尚不清楚。它可能是降解的中间体，或者在信号从膜转移到细胞核中具有一定的生理功能。钙蛋白酶水解转录因子（例如C-JUN和C-FOS），导致受受体活化引起的细胞信号下调。钙蛋白酶的激活至少通过水解PKC和转录因子停止了细胞信号转导途径。激活的钙蛋白酶非常不稳定，大概只使用了一次。钙蛋白酶基因是佛波酯的反应性基因，其转录是通过各种刺激（例如生长因子，凤凰酯等）对细胞进行处理的诱导的。新合成的钙蛋白钙蛋白酶补充钙蛋白酶用于下调信号转导的钙蛋白酶池。