The Effects of N-Linked Glycosylation on SLC6 Transporters
The Effects of N-Linked Glycosylation on SLC6 Transporters
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DOI：
10.1021/acs.jcim.2c00940
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发表时间：
2023-04-07
影响因子：
5.6
通讯作者：
Shukla, Diwakar
中科院分区：
文献类型：
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作者：
Chan, Matthew C.;Shukla, Diwakar
溶质载体 6 (SLC6) 家族的膜转运蛋白通过促进氨基酸、神经递质和其他代谢物的易位来介导各种生理过程。在体内，这些转运蛋白的活性通过各种翻译后修饰受到严格控制，这些修饰会对蛋白质表达、稳定性、膜运输和动力学产生影响。虽然 N 连接糖基化是真核生物中的普遍调控机制，但糖基化如何影响 SLC6 转运蛋白家族的一致机制仍然难以捉摸。人们普遍认为聚糖影响转运蛋白稳定性和膜运输；然而，糖基化对转运蛋白动力学的作用仍然存在争议，SLC6 家族的各个转运蛋白之间存在不同的结论。在这项研究中，我们收集了超过 1 ms 的聚合全原子分子动力学 (MD) 模拟数据，以系统地识别 N-聚糖对 SLC6 转运蛋白动力学的影响。我们对四种人类 SLC6 转运蛋白（血清素、多巴胺、甘氨酸和 B0AT1 转运蛋白）进行了建模，首先模拟连接到每个糖基化位点的聚糖的所有可能组合，然后研究较大的寡聚 N 连接聚糖对每个转运蛋白的影响。模拟表明，糖基化不会显着影响转运蛋白结构，但会改变糖基化细胞外环和周围区域的动力学。附着较大的聚糖分子进一步强调了糖基化对环动力学的结构影响。然而，没有观察到配体稳定性或门控螺旋运动的明显差异，因此，模拟表明糖基化对与底物运输相关的构象动力学没有深远的影响。
Membrane transporters of the solute carrier 6 (SLC6) family mediate various physiological processes by facilitating the translocation of amino acids, neurotransmitters, and other metabolites. In the body, the activity of these transporters is tightly controlled through various post-translational modifications with implications on protein expression, stability, membrane trafficking, and dynamics. While N-linked glycosylation is a universal regulatory mechanism among eukaryotes, a consistent mechanism of how glycosylation affects the SLC6 transporter family remains elusive. It is generally believed that glycans influence transporter stability and membrane trafficking; however, the role of glycosylation on transporter dynamics remains disputable, with differing conclusions among individual transporters across the SLC6 family. In this study, we collected over 1 ms of aggregated all-atom molecular dynamics (MD) simulation data to systematically identify the impact of N-glycans on SLC6 transporter dynamics. We modeled four human SLC6 transporters, the serotonin, dopamine, glycine, and B0AT1 transporters, by first simulating all possible combinations of a glycan attached to each glycosylation site followed by investigating the effect of larger, oligo-N-linked glycans to each transporter. The simulations reveal that glycosylation does not significantly affect the transporter structure but alters the dynamics of the glycosylated extracellular loop and surrounding regions. The structural consequences of glycosylation on the loop dynamics are further emphasized with larger glycan molecules attached. However, no apparent differences in ligand stability or movement of the gating helices were observed, and as such, the simulations suggest that glycosylation does not have a profound effect on conformational dynamics associated with substrate transport.