Activation of protein kinase C selectively inhibits the gamma-aminobutyric acidA receptor: role of desensitization.
Activation of protein kinase C selectively inhibits the gamma-aminobutyric acidA receptor: role of desensitization.
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发表时间：
1992-06
影响因子：
3.6
通讯作者：
N. Leidenheimer;S. McQuilkin;L. Hahner;P. Whiting;R. Harris
中科院分区：
文献类型：
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作者：
N. Leidenheimer;S. McQuilkin;L. Hahner;P. Whiting;R. Harris
使用 36Cl- 摄取，通过表达脑 mRNA 或亚基 cDNA 的非洲爪蟾卵母细胞和分离的小鼠脑小脑膜囊泡（微囊）中的两电极电压钳研究蛋白激酶 C (PKC) 激活剂对 γ-氨基丁酸 A (GABAA) 受体功能的影响。卵母细胞和微囊均表现出短暂（脱敏）和持续（非脱敏）GABAA 受体反应。在表达脑 mRNA 的卵母细胞中，PKC 激活剂佛波醇肉豆蔻酰乙酸酯 (PMA)（而非无活性的类似物佛波醇 12-单肉豆蔻酸酯）抑制瞬时和持续的 GABA 门控氯电流。 PMA 的抑制作用呈浓度依赖性，EC50 约为 5 nM，导致 GABA 的功效降低，但效力不降低。此外，PMA 抑制表达 alpha 1 beta 1 gamma 2L 亚基 cDNA 的卵母细胞中的 GABA 门控氯电流。 PMA对重组受体的作用被PKC抑制肽(PKCI)显着拮抗。在微囊制备中，PKC激活剂(-)-7-辛基吲哚内酰胺V和PMA抑制36Cl-通量的持续相而不改变瞬态相。 PMA 的作用被激酶抑制剂和 Mg-ATP 消耗所阻断，并被蛋白磷酸酶抑制剂模仿。这些结果证明PKC的激活抑制GABAA受体功能，并且微囊实验的结果表明PKC依赖性磷酸化优先使受体的非脱敏形式或状态失活。
The effects of protein kinase C (PKC) activators on gamma-aminobutyric acidA (GABAA) receptor function were studied by two-electrode voltage-clamp in Xenopus oocytes expressing brain mRNA or subunit cDNAs and in isolated mouse brain cerebellar membrane vesicles (microsacs), using 36Cl- uptake. Both oocytes and microsacs showed transient (desensitizing) and sustained (nondesensitizing) GABAA receptor responses. In oocytes expressing brain mRNA, the PKC activator phorbol myristoyl acetate (PMA), but not the inactive analog phorbol 12-monomyristate, inhibited both transient and sustained GABA-gated chloride currents. The inhibition by PMA was concentration dependent, with an EC50 of approximately 5 nM, and resulted in a decrease in the efficacy, but not the potency, of GABA. Additionally, PMA inhibited GABA-gated chloride currents in oocytes expressing alpha 1 beta 1 gamma 2L subunit cDNAs. The effect of PMA on recombinant receptors was significantly antagonized by PKC inhibitory peptide (PKCI). In the microsac preparation, the PKC activators (-)-7-octylindolactam V and PMA inhibited the sustained phase of 36Cl- flux without altering the transient phase. The action of PMA was blocked by kinase inhibitors and by depletion of Mg-ATP and was mimicked by protein phosphatase inhibitors. These results demonstrate that activation of PKC inhibits GABAA receptor function, and the results from the microsac experiments suggest that PKC-dependent phosphorylation preferentially inactivates a nondesensitized form or state of the receptor.