O-GlcNac Modulation of GABAergic Transmission

gaba能传递强度的变化在很大程度上受到翻译后修饰和变构调节剂（如苯二氮卓类药物和神经类固醇）的影响。O- glcnac酰化（O- GlcNAc）是由O-GlcNAc转移酶（OGT）和O- glcnacase （OGA）严格调控的翻译后修饰，它们分别将β - n -乙酰氨基葡萄糖的O-GlcNAc片段添加或去除到蛋白质的Ser/Thr残基上。各种神经退行性疾病，如阿尔茨海默病（AD）和代谢紊乱，如糖尿病，表现出失调的O-GlcNAc水平。我们实验室发表的报告表明，o - glcn酰化的急性增加诱导诱发的GABAAR介导的IPSC （eipsc）的长期抑制，并降低海马主细胞中自发IPSC （sIPSC）的振幅和频率，但其发生的机制尚不清楚。大量研究表明，GABAAR的丝氨酸磷酸化可根据神经元类型和特定亚基增加或减少GABAAR电流。虽然o - glcn酰化调节抑制性gaba门控电流，但没有研究检查其与丝氨酸磷酸化在gaba能传递中的相互作用。由于o - glcnac酰化和磷酸化之间的串扰影响多种蛋白的调控，因此o - glcnac酰化和磷酸化可能在调节GABAAR功能和抑制传递强度方面相互作用。此外，潜在的相互作用可能会影响变构调节剂如何影响GABAARs，因为丝氨酸磷酸化可以增加或降低这些调节剂的功效。提出的研究将调查这些假设，并将测试O- GlcNAc水平长期升高的疾病状况是否会导致GABAAR功能下降，从而可以通过药物抑制OGT来挽救GABAAR功能。在磷酸化和变构调节剂存在的情况下，为了确定o - glcn酰化对gaba能传递的影响，我将使用电生理技术、免疫印迹测定和质谱分析。结果将显示PKA和变构调节剂对GABAAR功能的调节是否受O-GlcNAc修饰的存在或不存在的影响，以及在疾病模型中恢复O-GlcNAc酰化水平是否可以恢复E/I平衡。

Changes in the strength of GABAergic transmission is heavily influenced by posttranslational modifications and allosteric modulators like benzodiazepines and neurosteroids. O-GlcNAcylation (O- GlcNAc) is a post- translational modification that is tightly regulated by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), which add or remove the O-GlcNAc moiety of β–N-acetylglucosamine to Ser/Thr residues on proteins, respectively. Various neurodegenerative diseases like Alzheimer's disease (AD), and metabolic disorders like, diabetes exhibit dysregulated O-GlcNAc levels. Published reports from our lab have demonstrated that an acute increase in O-GlcNAcylation induces a long-term depression of evoked GABAAR mediated IPSCs (eIPSCs) and reduces the amplitude and frequency of spontaneous IPSC (sIPSC) in hippocampal principal cells, however the mechanism in which this occurs is unknown. Numerous studies have shown that serine phosphorylation of GABAAR can increase or decrease GABAAR currents depending on the neuron type and specific subunit. While O-GlcNAcylation modulates inhibitory GABA-gated currents, no studies have examined its interplay with serine phosphorylation on GABAergic transmission. Because the crosstalk between O-GlcNAcylation and phosphorylation affects the regulation of various proteins, the potential exists that O-OglcNAcylation and phosphorylation will interaction in the modulation of GABAAR function and the strength of inhibitory transmission. Furthermore, a potential interaction could impact how allosteric modulators effect GABAARs, since serine phosphorylation can either increase or decrease efficacy of these modulators. Studies proposed will investigate these hypotheses and will also test whether disease conditions where O- GlcNAc levels are chronically elevated lead to depressed GABAAR function that can be rescued via pharmacological inhibition of OGT. To determine O-GlcNAcylation's effect on GABAergic transmission in the presence of phosphorylation and allosteric modulators, I will use electrophysiological techniques, immunoblotting assays and mass spectrometry. Results will show whether the modulation of GABAAR function by PKA and allosteric modulators are shaped by the presence or absence of a co-occurring O- GlcNAc modification and if the restoration of O-GlcNAcylation levels in a disease models can restore the E/I balance.