Jalava A, Lintunen M, Heikkilä J
Department of Biochemistry and Pharmacy, Abo Akademi University, Turku, Finland.
Biochem Biophys Res Commun. 1993 Mar 15;191(2):472-8. doi: 10.1006/bbrc.1993.1242.
SH-SY5Y human neuroblastoma cells can be induced to differentiate by phorbol esters but not by bryostatins although both agents increase protein kinase C (PKC) activity in these cells to a similar extent. We examined whether this difference could be explained by differences in the responses of specific PKC isoenzymes. Both TPA and bryostatin 1 at 10 nM induced a rapid increase in membrane-associated PKC-alpha immunoreactivity which was sustained for 72 hours in TPA-treated cells, but was down-regulated within 24 hours in bryostatin-treated cells. TPA likewise induced a sustained phosphorylation of an 80 kDa PKC substrate whereas in bryostatin-treated cells the 80 kDa substrate was rapidly phosphorylated reaching a maximum at 6 hours followed by a decline to basal level within 48 hours. A higher concentration of TPA (300 nM), which results in a less differentiated phenotype, induced down-regulation of PKC-alpha within 24 hours. In contrast, both TPA and bryostatin 1 stimulated translocation and a partial down-regulation of PKC-epsilon with similar kinetics. These results suggest that the divergent actions of bryostatin 1 and TPA in SH-SY5Y cells are at least partially due to differential modulation of PKC-alpha but not PKC-epsilon by these two agents.
佛波酯可诱导SH-SY5Y人神经母细胞瘤细胞分化，但苔藓抑素却不能，尽管这两种物质均可使这些细胞中的蛋白激酶C（PKC）活性升高至相似程度。我们研究了这种差异是否可以通过特定PKC同工酶反应的差异来解释。10 nM的佛波酯（TPA）和苔藓抑素1均能迅速增加膜相关PKC-α的免疫反应性，在TPA处理的细胞中这种增加持续72小时，但在苔藓抑素处理的细胞中24小时内就下调了。TPA同样诱导了一种80 kDa PKC底物的持续磷酸化，而在苔藓抑素处理的细胞中，80 kDa底物迅速磷酸化，在6小时达到最大值，然后在48小时内降至基础水平。更高浓度的TPA（300 nM）会导致细胞分化程度降低，它能在24小时内诱导PKC-α下调。相比之下，TPA和苔藓抑素1均以相似的动力学刺激PKC-ε易位并使之部分下调。这些结果表明，苔藓抑素1和TPA在SH-SY5Y细胞中的不同作用至少部分是由于这两种物质对PKC-α的调节不同，而不是对PKC-ε的调节不同。
