PDF(Pubmed)
Abstract：
Betaine is an endogenous osmolyte that exhibits therapeutic potential by mitigating various neurological disorders. However, the underlying cellular and molecular mechanisms responsible for its neuroprotective effects remain puzzling.In this study, we describe a possible mechanism behind the positive impact of betaine in preserving neurons from excitotoxicity. Here we demonstrate that betaine at low concentration modulates the GABA uptake by GAT1 (slc6a1), the predominant GABA transporter in the central nervous system. This modulation occurs through the temporal inhibition of the transporter, wherein prolonged occupancy by betaine impedes the swift transition of the transporter to the inward conformation. Importantly, the modulatory effect of betaine on GAT1 is reversible, as the blocking of GAT1 disappears with increased extracellular GABA. Using electrophysiology, mass spectroscopy, radiolabelled cellular assay, and molecular dynamics simulation we demonstrate that betaine has a dual role in GAT1: at mM concentration acts as a slow substrate, and at µM as a temporal blocker of GABA, when it is below its K0.5. Given this unique modulatory characteristic and lack of any harmful side effects, betaine emerges as a promising neuromodulator of the inhibitory pathways improving GABA homeostasis via GAT1, thereby conferring neuroprotection against excitotoxicity.
摘要：
甜菜碱是一种内源性渗透压物质，通过减轻各种神经系统疾病而表现出治疗潜力。然而,负责其神经保护作用的潜在细胞和分子机制仍然令人困惑。在这项研究中,我们描述了甜菜碱对保护神经元免受兴奋性毒性的积极影响背后的可能机制。在这里，我们证明，甜菜碱在低浓度调节GABA摄取GAT1（slc6a1），中枢神经系统中主要的GABA转运蛋白。这种调节是通过对转运蛋白的时间抑制而发生的，其中甜菜碱的长时间占用会阻碍转运蛋白迅速过渡到向内构象。重要的是,甜菜碱对GAT1的调节作用是可逆的，随着细胞外GABA的增加，GAT1的阻断消失。使用电生理学，质谱,放射性标记的细胞测定，和分子动力学模拟，我们证明甜菜碱在GAT1中具有双重作用：在mM浓度下充当缓慢的底物，在µM时作为GABA的时间阻滞剂，当它低于K0.5时。鉴于这种独特的调节特性和缺乏任何有害的副作用，甜菜碱作为抑制途径的有希望的神经调节剂通过GAT1改善GABA稳态，从而赋予神经保护以对抗兴奋性毒性。
