Structure and inhibition mechanism of the human citrate transporter NaCT.
Structure and inhibition mechanism of the human citrate transporter NaCT.
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DOI：
10.1038/s41586-021-03230-x
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发表时间：
2021-03
期刊：
影响因子：
64.8
通讯作者：
Wang DN
中科院分区：
文献类型：
--
作者：
Sauer DB;Song J;Wang B;Hilton JK;Karpowich NK;Mindell JA;Rice WJ;Wang DN
众所周知，柠檬酸是细胞TCA循环中的中间体。除了在能量代谢中的这一重要作用外，三羧酸阴离子也是脂肪酸合成的前体和调节剂。因此，脂肪酸合成的速度与胞浆柠檬酸浓度直接相关。肝细胞通过钠依赖的柠檬酸转运体NACT(SLC13A5)输入柠檬酸盐，因此该蛋白是抗肥胖药物的潜在靶点。为了了解其抑制机制的结构基础，我们测定了人NACT在与柠檬酸盐和小分子抑制剂的络合物中的冷冻电子显微镜结构。这些结构揭示了与柠檬酸盐结合在同一位置的抑制剂是如何阻止蛋白质的运输周期的。NACT-抑制剂结构也解释了为什么该化合物选择性地抑制NACT超过两个同源的人二羧酸转运体，并提出了进一步提高亲和力和选择性的方法。最后，NACT结构为理解各种突变如何取消NACT在大脑中的运输活动从而导致新生儿SLC13A5癫痫提供了一个框架。
Citrate is most well-known as an intermediate in the TCA cycle of the cell. In addition to this essential role in energy metabolism, the tricarboxylate anion also acts as both a precursor and a regulator of fatty acid synthesis . Thus, the rate of fatty acid synthesis correlates directly with the cytosolic citrate concentration . Liver cells import citrate via the sodium-dependent citrate transporter NaCT (SLC13A5), and as a consequence this protein is a potential target for anti-obesity drugs. To understand the structural basis of its inhibition mechanism, we have determined cryo-electron microscopy structures of human NaCT in complex with citrate and with a small molecule inhibitor. These structures reveal how the inhibitor, bound at the same site as citrate, arrests the protein’s transport cycle. The NaCT-inhibitor structure also explains why the compound selectively inhibits NaCT over two homologous human dicarboxylate transporters, and suggests ways to further improve the affinity and selectivity. Finally, the NaCT structures provide a framework for understanding how various mutations abolish NaCT’s transport activity in the brain and thereby cause SLC13A5-Epilepsy in newborns .