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.

为了阐明蛋白激酶 C 下调的机制及其在细胞信号转导中的意义，对钙蛋白酶和蛋白激酶 C (PKC) 进行了研究。当细胞表面受体被配体激活且细胞内钙浓度增加时，钙蛋白酶和 PKC 在结合钙离子时同时易位至生物膜。在钙存在的情况下，二酰基甘油和磷脂在膜上激活 PKC。在钙和磷脂酰肌醇-4,5-二磷酸存在的情况下，钙蛋白酶也会在膜上自催化被激活。活化的钙蛋白酶作用于活化的 PKC，水解 N 端调节结构域和 C 端激酶结构域之间的键，产生 PKC 的活性片段，该片段在没有辅因子的情况下也具有活性。钙蛋白酶仅识别活性和磷酸化物质，非活性 PKC 不会被水解。活性片段的作用尚不清楚。它可能是降解的中间体，或者在信号从膜到细胞核的转导中具有某些生理功能。Calpain 水解转录因子，如 c-Jun 和 c-Fos，导致由激活的细胞信号下调。受体。钙蛋白酶的激活至少通过水解 PKC 和转录因子来停止细胞信号转导途径。激活的钙蛋白酶非常不稳定，可能仅使用一次。钙蛋白酶基因是佛波酯响应基因，其转录是通过各种刺激物处理细胞而诱导的，例如生长因子、佛波酯等。新合成的钙蛋白酶补充了用于下调信号转导的钙蛋白酶池。