GABAA receptor phosphorylation and functional modulation in cortical neurons by a protein kinase C-dependent pathway
GABAA receptor phosphorylation and functional modulation in cortical neurons by a protein kinase C-dependent pathway
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DOI：
10.1074/jbc.m004910200
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发表时间：
2000-12-08
影响因子：
4.8
通讯作者：
Moss, SJ
中科院分区：
文献类型：
--
作者：
Brandon, NJ;Delmas, P;Moss, SJ
GABA(A) 受体是大脑中快速突触抑制的关键介质，中枢神经系统中的主要受体亚型被认为是由 α、β 和 γ 亚基组成的五聚体。先前对重组受体的研究表明，蛋白激酶C（PRC）和PHA直接磷酸化受体β亚基内的细胞内丝氨酸残基并调节受体功能。然而，这种调节与神经元受体的相关性仍然知之甚少。为了解决这个关键问题，我们研究了培养的皮质神经元中 GABA(A) 受体的磷酸化和功能调节。在这里，我们表明神经元 β3 亚基通过 PHC 依赖性途径在丝氨酸残基上进行基础磷酸化。 PKC 抑制剂消除基础磷酸化，增加受体活性，而 PKC 激活剂增强 β3 磷酸化，同时降低受体活性。 PKA 激活剂仅在 PKC 抑制剂存在的情况下才会增加 β3 亚基的磷酸化。我们还表明，神经元 β3 亚基内磷酸化的主要位点可能包括 Ser-408 和 Ser-409，这些残基对于含有 β3 的重组受体的功能调节很重要。此外，PHC 激活不会改变质膜中 GABA(A) 受体的总数，这表明 PKC 激活的影响是关于通道的选通或电导。总之，这些结果表明，激活 PKC 的细胞信号传导途径可能通过直接调节 GABA(A) 受体功能，对突触抑制的功效产生深远的影响。
GABA(A) receptors are critical mediators of fast synaptic inhibition in the brain, and the predominant receptor subtype in the central nervous system is believed to be a pentamer composed of alpha, beta, and gamma subunits. Previous studies on recombinant receptors have shown that protein kinase C (PRC) and PHA directly phosphorylate intracellular serine residues within the receptor beta subunit and modulate receptor function. However, the relevance of this regulation for neuronal receptors remains poorly characterized. To address this critical issue, we have studied phosphorylation and functional modulation of GABA(A) receptors in cultured cortical neurons. Here we show that the neuronal beta3 subunit is basally phosphorylated on serine residues by a PHC-dependent pathway. PKC inhibitors abolish basal phosphorylation, increasing receptor activity, whereas activators of PKC enhance beta3 phosphorylation with a concomitant decrease in receptor activity. PKA activators were shown to increase the phosphorylation of the beta3 subunit only in the presence of PKC inhibitors, We also show that the main sites of phosphorylation within the neuronal beta3 subunit are likely to include Ser-408 and Ser-409, residues that are important for the functional modulation of beta3-containing recombinant receptors, Furthermore, PHC activation did not change the total number of GABA(A) receptors in the plasma membrane, suggesting that the effects of PKC activation are on the gating or conductance of the channel. Together, these results illustrate that cell-signaling pathways that activate PKC may have profound effects on the efficacy of synaptic inhibition by directly modulating GABA(A) receptor function.