Jones Michelle L, Leonard John P
Laboratory of Integrative Neuroscience and Laboratory for Molecular Biology, Department of Biological Sciences, University of Illinois at Chicago, 845 W. Taylor Street, Chicago, IL 60607, USA.
J Neurochem. 2005 Mar;92(6):1431-8. doi: 10.1111/j.1471-4159.2004.02985.x.
Insulin modulates N-methyl-d-aspartate (NMDA) receptors in the CNS and potentiates currents of recombinant NMDA receptors in a subunit-specific manner in Xenopus oocytes. Previously we identified two sites in the NR2B C-terminus as targets for direct phosphorylation by C-type protein kinases (PKCs). Mutating these sites reduced insulin potentiation of currents by one half, reflecting the PKC-mediated portion of the NR2B insulin effect. The PKC-proline rich tyrosine kinase (Pyk2)-Src family kinase pathway may also mediate insulin potentiation. A dominant negative Pyk2 mutant significantly reduced insulin potentiation when co-expressed with NR2B-containing receptors, suggesting that Pyk2 and downstream Src-family tyrosine kinases are involved, along with PKCs, in insulin potentiation of NR2B. The NR2A C-terminus contains two residues homologous to the NR2B PKC targets. Mutating both these sites eliminated insulin potentiation of NR2A-containing receptors, while co-expression of dominant negative Pyk2 had no effect. Together, these data indicate that PKCs alone mediate the NR2A insulin effect. When tested individually for importance in insulin potentiation, the two PKC sites showed an additive effect in potentiation of NR2A-containing receptors. Insulin modulation of NR2A-containing receptors is mediated solely by PKCs, whereas insulin modulation of NR2B-containing receptors is mediated by PKCs and tyrosine kinases (PTKs).
胰岛素可调节中枢神经系统中的N-甲基-D-天冬氨酸（NMDA）受体，并以亚基特异性方式增强非洲爪蟾卵母细胞中重组NMDA受体的电流。此前我们确定了NR2B C末端的两个位点是C型蛋白激酶（PKC）直接磷酸化的靶点。突变这些位点可使电流的胰岛素增强作用降低一半，这反映了NR2B胰岛素效应中PKC介导的部分。PKC-富含脯氨酸的酪氨酸激酶（Pyk2）-Src家族激酶途径也可能介导胰岛素增强作用。当与含NR2B的受体共表达时，显性负性Pyk2突变体可显著降低胰岛素增强作用，这表明Pyk2和下游Src家族酪氨酸激酶与PKC一起参与了NR2B的胰岛素增强作用。NR2A C末端含有两个与NR2B PKC靶点同源的残基。突变这两个位点可消除含NR2A受体的胰岛素增强作用，而共表达显性负性Pyk2则无影响。这些数据共同表明，单独的PKC介导了NR2A的胰岛素效应。当分别测试其在胰岛素增强作用中的重要性时，两个PKC位点在含NR2A受体的增强作用中表现出累加效应。含NR2A受体的胰岛素调节仅由PKC介导，而含NR2B受体的胰岛素调节则由PKC和酪氨酸激酶（PTK）介导。
