Effects of Ca2+ on the activation of conventional and new PKC isozymes and on TPA and endothelin‐1 induced translocations of these isozymes in intact cells

FEBS Letters

Chen, Ching-Chow¹ 

[1] Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei 10018, Taiwan, ROC

关键词: Protein kinase C;    Isozyme;    conventional and new;    Extracellular Ca2+-depletion;    Ionomycin;    TPA;    ET-1;   

DOI  :  10.1016/0014-5793(94)00571-0

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The effects of Ca²⁺ on the translocation of conventional and new protein kinase C isozymes in intact cells were studied by using C₆ glioma cells as a model system. Two conditions which monitor intracellular Ca²⁺ were performed: one is extracellular Ca²⁺-depletion by treating the cells with physiological saline solution (PSS) without Ca²⁺ but containing 0.5 mM EGTA, the other is treating the cells with 1 μM ionomycin to induce Ca²⁺-influx. In addition, the TPA and endothelin-1 induced translocations of conventional and new PKC isozymes under these two conditions were also comparatively studied. When the intact cells were treated with Ca²⁺-free, EGTA containing PSS, the membrane-bound conventional PKCα (cPKCα) was greatly reduced and cytosolic cPKCα was slightly increased. However, neither membrane bound nor cytosolic new PKCδ (nPKCδ) was affected by extracellular Ca²⁺-depletion. On the other hand, when the cells were treated with 1 μM ionomycin, the translocation of cPKCα itself was observed while nPKCδ was not affected. In extracellular Ca²⁺-depletion, the translocation of cPKCα induced by 100 nM TPA still occurred although the extent of translocation was smaller than that induced by TPA under normal Ca²⁺ conditions; however, that induced by 30 nM ET-1 was blocked. After the cells were treated with 1 μM ionomycin, the translocation of cPKCα induced by 30 nM TPA was further increased compared to 1 μM ionomycin or 30 nM TPA alone, while that induced by ET-1 was only slightly further increased. All these results suggested that in intact cells, the activation of cPKCα was operated by both the intracellular Ca²⁺ level and diacylglycerol and that of nPKCδ was operated by diacylglycerol alone as predicted by their properties from purified enzyme or cDNA. In addition, the translocation of cPKCα induced by the natural activator ET-1 seemed to be more dependent on Ca²⁺ than TPA in intact cells.

【 授权许可】

Unknown