PDF(Pubmed)
Abstract：
GABAergic transmission is influenced by post-translational modifications, like phosphorylation, impacting channel conductance, allosteric modulator sensitivity, and membrane trafficking. O-GlcNAcylation is a post-translational modification involving the O-linked attachment of β-N-acetylglucosamine on serine/threonine residues. Previously we reported an acute increase in O-GlcNAcylation elicits a long-term depression of evoked GABAAR inhibitory postsynaptic currents (eIPSCs) onto hippocampal principal cells. Importantly, O-GlcNAcylation and phosphorylation can co-occur or compete for the same residue; whether they interact in modulating GABAergic IPSCs is unknown. We tested this by recording IPSCs from hippocampal principal cells and pharmacologically increased O-GlcNAcylation, before or after increasing serine phosphorylation using the adenylate cyclase activator, forskolin. Although forskolin had no significant effect on baseline eIPSC amplitude, we found that a prior increase in O-GlcNAcylation unmasks a forskolin-dependent increase in eIPSC amplitude, reversing the O-GlcNAc-induced eIPSC depression. Inhibition of adenylate cyclase or protein kinase A did not prevent the potentiating effect of forskolin, indicating serine phosphorylation is not the mechanism. Surprisingly, increasing O-GlcNAcylation also unmasked a potentiating effect of the neurosteroids 5α-pregnane-3α,21-diol-20-one (THDOC) and progesterone on eIPSC amplitude in about half of the recorded cells, mimicking forskolin. Our findings show that under conditions of heightened O-GlcNAcylation, the neurosteroid site on synaptic GABAARs is possibly accessible to agonists, permitting strengthening of synaptic inhibition.
摘要：
GABA能传递受翻译后修饰的影响，比如磷酸化，影响通道电导，变构调节剂灵敏度，和膜贩运。O-GlcNAcylation是一种翻译后修饰，涉及β-N-乙酰葡糖胺在丝氨酸/苏氨酸残基上的O连接连接。以前，我们报道了O-GlcNAcylation的急性增加会导致诱发的GABAAR抑制性突触后电流（eIPSC）长期抑制海马主细胞。重要的是,O-GlcNAcylation和磷酸化可以共存或竞争相同的残基;它们是否在调节GABA能IPSC中相互作用是未知的。我们通过记录海马主细胞的IPSC和药理学上增加的O-GlcNAcylation来测试这一点，在使用腺苷酸环化酶激活剂增加丝氨酸磷酸化之前或之后，Forskolin.虽然毛喉素对基线eIPSC振幅没有显著影响，我们发现，O-GlcNAcylation的先前增加揭示了eIPSC振幅的毛喉素依赖性增加，逆转O-GlcNAc诱导的eIPSC抑制。抑制腺苷酸环化酶或蛋白激酶A并不能阻止毛喉素的增强作用，表明丝氨酸磷酸化不是机制。令人惊讶的是,增加O-GlcNAcylation也揭示了神经类固醇5α-孕烷3α的增强作用，21-diol-20-one（THDOC）和孕酮对约一半记录细胞的eIPSC振幅，模仿Forskolin.我们的研究结果表明，在O-GlcNAcylation升高的条件下，突触GABAAR上的神经类固醇位点可能是激动剂可以接近的，允许加强突触抑制。
