PKC AND THE SECRETION AND BIOSYNTHESIS OF NEUROPEPTIDES IN ATT-20 CELLS

PKC 与 ATT-20 细胞中神经肽的分泌和生物合成

• 批准号: 3822977
• 负责人: R ESKAY
• 金额: --
• 依托单位: NATIONAL INSTITUTE ON ALCOHOL ABUSE AND ALCOHOLISM
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/3822977
• 关键词: cell membrane; cytoplasm; ethanol; membrane permeability; neoplastic cell; peptide hormone biosynthesis; pituitary neoplasms; protein kinase C; tissue /cell culture; tumor promoters

Enhanced protein phosphorylation is one of the intracellular events which invariably follows membrane receptor activation. Recently identified Protein Kinase C (PKC) is a unique enzyme which phosphorylates specific proteins, whose functions remain to be determined. PKC requires a phospholipid and a diacylglycerol (DAG) for maximal activity. DAG is the hydrolytic product of membrane polyphosphoinositide breakdown, which occurs following membrane receptor occupancy, and is one of the initial events in signal transduction. The release of DAG during PI turnover substantially stimulates PKC activity over that observed in quiescent cells. The known co-carcinogen or tumor promoter, TPA, specifically increases membrane PKC activity. Associated with this increased membrane PKC activity is a reduction of cytosolic PKC activity, which suggests that translocation of PKC from the cytosol to the membrane is an important intracellular event. Using AtT-20 cells that respond to a variety of membrane and intracellular activators by releasing POMC-derived peptides, we have explored the involvement of PKC in hormone secretion by monitoring the release of beta endorphin (BE), as well as membrane and cytosolic PKC activity. TPA treatment resulted in a dose-related increase in BE secretion and translocation of PKC from the cytosolic to the membrane fraction. A maximally-stimulating concentration of TPA enhanced membrane PKC activity 2-fold within 1 min and 5-fold within 3 min. Preincubation of AtT-20 cells with ethanol (0.1-0.6%) for 24 hours resulted in a dose-related 2-5 fold reduction in cytosolic PKC activity and a 50% reduction in membrane PKC activity at 0.4% ethanol. Ethanol pretreatment for 24 hours only marginally reduced the ability of a maximal stimulatory concentration of TPA to induce translocation of PKC.

增强的蛋白质磷酸化是细胞内事件之一 始终遵循膜受体激活。 最近确定 蛋白激酶C（PKC）是一种独特的酶，可磷酸化特定 蛋白质的功能仍有待确定。 PKC需要一个 磷脂和二酰基甘油（DAG），用于最大活性。 DAG是 发生的膜多磷酸肌醇分解的水解产物 在膜受体占用率之后，是 信号转导。 PI周转期间DAG的释放基本上 刺激静态细胞中观察到的PKC活性。 已知 联合加霉菌原或肿瘤启动子TPA特别增加了膜PKC 活动。 与这种增加的膜PKC活性相关的是 胞质PKC活性的减少，这表明易位 从细胞质到膜的PKC是重要的细胞内事件。 使用对各种膜和细胞内反应的ATT-20单元 激活剂通过释放POMC衍生的肽，我们探索了 通过监测Beta的释放，PKC参与激素分泌 内啡肽（BE），以及膜和胞质PKC活性。 TPA 治疗导致与剂量有关的增加是分泌和 PKC从胞质到膜分数的易位。 一个 TPA增强膜PKC活性的最大刺激浓度 在1分钟内2倍，3分钟内5倍。 预孵育ATT-20细胞 乙醇（0.1-0.6％）24小时导致剂量相关2-5倍 胞质PKC活性的降低和膜PKC降低50％ 活性为0.4％乙醇。 仅乙醇预处理24小时 略降低了最大刺激浓度的能力 TPA诱导PKC的易位。