PKC site mutations reveal differential modulation by insulin of NMDA receptors containing NR2A or NR2B subunits
PKC site mutations reveal differential modulation by insulin of NMDA receptors containing NR2A or NR2B subunits
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DOI：
10.1111/j.1471-4159.2004.02985.x
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发表时间：
2005-03-01
影响因子：
4.7
通讯作者：
Leonard, JP
中科院分区：
文献类型：
--
作者：
Jones, ML;Leonard, JP
胰岛素调节中枢神经系统中的N-甲基-D-天冬氨酸(NMDA)受体，并以亚单位特异性的方式增强非洲爪哇卵母细胞的重组NMDA受体电流。在此之前，我们发现NR2B C末端的两个位点是C型蛋白激酶(PKCs)直接磷酸化的靶点。突变这些位点使电流的胰岛素增强减少了一半，反映了PKC介导的NR2B胰岛素效应部分。PKC-富含脯氨酸的酪氨酸激酶(PYK2)-Src家族的激酶通路也可能介导胰岛素的增强。当与含有NR2B的受体共表达时，显性负的Pyk2突变体显著降低了胰岛素的增强作用，这表明Pyk2及其下游的Src家族酪氨酸激酶与PKC一起参与了NR2B的胰岛素增强。NR2a的C末端含有两个与NR2B PKC靶标同源的残基。这两个位点的突变消除了含有NR2A的受体的胰岛素增强作用，而显性负向Pyk2的共同表达则没有影响。综上所述，这些数据表明PKCs本身就介导了NR2A型胰岛素效应。当单独测试在胰岛素增强中的重要性时，这两个PKC位点在包含NR2A的受体的增强中显示出相加的效应。含NR2A受体的胰岛素调节完全由PKCs介导，而含NR2B受体的胰岛素调节则由PKCs和酪氨酸激酶(PTKs)介导。
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).