Pepio Antonio M, Thibault Ginette L, Sossin Wayne S
Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec H3A 2B4, Canada.
J Biol Chem. 2002 Oct 4;277(40):37116-23. doi: 10.1074/jbc.M202264200. Epub 2002 Jul 24.
Phosphorylation of protein kinase Cs (PKCs) by phosphoinositide-dependent kinase I (PDK) is critical for PKC activity. In the nervous system of the marine mollusk Aplysia, there are only two major PKC isoforms, the calcium-activated PKC Apl I and the calcium-independent PKC Apl II, and both PKCs are persistently activated during intermediate memory. We monitored the PDK-dependent phosphorylation of PKC Apl I and PKC Apl II using phosphopeptide antibodies. During persistent activation of PKCs in Aplysia neurons, there is a significant increase in the amount of PDK-phosphorylated PKC Apl II in the particulate fraction but no increase in the amount of PKC Apl I phosphorylated by PDK. PDK phosphorylation of PKCs was not sensitive to inhibitors of phosphatidylinositol 3-kinase, PKC, or expression of a kinase-inactive PDK. Localization of PDK-phosphorylated PKC Apl II using immunocytochemistry revealed an enrichment of phosphorylated PKC Apl II at the plasma membrane. These data suggest that increased PDK phosphorylation of PKC Apl II is important for persistent kinase activation.
磷酸肌醇依赖性激酶I（PDK）对蛋白激酶C（PKC）的磷酸化作用对于PKC的活性至关重要。在海洋软体动物海兔的神经系统中，只有两种主要的PKC亚型，即钙激活的PKC Apl I和钙非依赖性的PKC Apl II，并且在中间记忆过程中这两种PKC都持续被激活。我们使用磷酸肽抗体监测了PKC Apl I和PKC Apl II的PDK依赖性磷酸化。在海兔神经元中PKC持续激活期间，颗粒部分中PDK磷酸化的PKC Apl II的量显著增加，但PDK磷酸化的PKC Apl I的量没有增加。PKC的PDK磷酸化对磷脂酰肌醇3激酶、PKC的抑制剂或激酶失活的PDK的表达不敏感。使用免疫细胞化学对PDK磷酸化的PKC Apl II进行定位显示，磷酸化的PKC Apl II在质膜处富集。这些数据表明，PKC Apl II的PDK磷酸化增加对于激酶的持续激活很重要。
