Jarvis W D, Auer K L, Spector M, Kunos G, Grant S, Hylemon P, Mikkelsen R, Dent P
Department of Medicine, Medical College of Virginia, Richmond 23298-0058, USA.
FEBS Lett. 1997 Jul 21;412(1):9-14. doi: 10.1016/s0014-5793(97)00705-9.
The role of protein kinase C (PKC) and p42(MAP kinase) signaling in the regulation of proliferation and apoptosis was investigated in freshly isolated and primary cultured rat hepatocytes. Acute treatment of freshly isolated hepatocytes with phenylephrine and EGF caused rapid phasic activations of p42(MAP kinase) and JNK1. Acute pre-treatment of hepatocytes with the PKC inhibitors sphingosine, chelerythrine and bis-indolylmaleimide abolished the ability of phenylephrine, but not EGF, to activate p42(MAP kinase) and JNK1. Acute pretreatments with all of the PKC inhibitors alone increased JNK1 basal activity approximately 2-fold. Acute treatments of primary cultures of hepatocytes with an inhibitor of MEK1 activation (PD98059) also caused inhibition of p42(MAP kinase) and a approximately 2-fold activation of JNK1. These data demonstrate that PKC can function as both a proximal activator and a distal inhibitor of signaling through the JNK1/SAP kinase pathway. Treatments (4 h) of primary cultured hepatocytes with sphingosine, chelerythrine, bis-indolylmaleimide and PD98059 did not induce apoptosis as judged by propidium iodide staining. Similar acute treatments of HepG2 cells rapidly induced cell death. These data demonstrate that acute inhibition of either PKC or p42(MAP kinase) function is sufficient to rapidly induce apoptosis in transformed, but not in non-transformed hepatocytes.
在新鲜分离和原代培养的大鼠肝细胞中，研究了蛋白激酶C（PKC）和p42（丝裂原活化蛋白激酶）信号传导在增殖和凋亡调节中的作用。用去氧肾上腺素和表皮生长因子（EGF）对新鲜分离的肝细胞进行急性处理，可导致p42（丝裂原活化蛋白激酶）和JNK1迅速出现阶段性激活。用PKC抑制剂鞘氨醇、白屈菜红碱和双吲哚马来酰胺对肝细胞进行急性预处理，可消除去氧肾上腺素（而非EGF）激活p42（丝裂原活化蛋白激酶）和JNK1的能力。单独使用所有PKC抑制剂进行急性预处理，均可使JNK1基础活性增加约2倍。用MEK1激活抑制剂（PD98059）对原代培养的肝细胞进行急性处理，也会导致p42（丝裂原活化蛋白激酶）受到抑制，JNK1激活约2倍。这些数据表明，PKC可作为通过JNK1/应激激活蛋白激酶途径进行信号传导的近端激活剂和远端抑制剂。用鞘氨醇、白屈菜红碱、双吲哚马来酰胺和PD98059对原代培养的肝细胞进行处理（4小时），通过碘化丙啶染色判断，未诱导凋亡。对HepG2细胞进行类似的急性处理可迅速诱导细胞死亡。这些数据表明，急性抑制PKC或p42（丝裂原活化蛋白激酶）功能足以在转化的肝细胞中迅速诱导凋亡，但在未转化的肝细胞中则不然。
