Department of Pharmacology, School of Medicine, University of California, Davis, California, USA.
Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California, USA.
Ann Clin Transl Neurol. 2022 May;9(5):600-609. doi: 10.1002/acn3.51536. Epub 2022 Mar 24.
Royal demolition explosive (RDX) can induce seizures in wildlife and humans following release into the environment or after voluntary consumption. During the Vietnam War, RDX intoxication was the most common cause of generalized seizures in US service personnel, and in some sections of the armed forces, eating of RDX has continued as "a dare" to this day. After its mechanism of action was long unknown, RDX was recently shown to be a GABA receptor antagonist. We here determined the GABA receptor subtype-selectivity of RDX and mapped its functional binding site.
We used whole-cell patch-clamp to determine the potency of RDX on 10 recombinantly expressed GABA receptors and mapped the RDX binding site using a combination of Rosetta molecular modeling and site-directed mutagenesis.
RDX was found to reversibly inhibit the α1β2γ2 GABA receptor with an IC of 23 μmol/L (95% CI 15.1-33.3 μmol/L), whereas α4 and α6 containing GABA receptor combinations were 4-10-fold less sensitive. RDX is binding to the noncompetitive antagonist (NCA) site in the pore. In a molecular model based on the cryo-EM structure of the resting state of the α1β2γ2 receptor, RDX forms two hydrogen bonds with the threonines at the T6' ring and makes hydrophobic interactions with the valine and alanine in 2' position of the α1 or β2 subunits.
Our findings characterize the mechanism of action of RDX at the atomistic level and suggest that RDX-induced seizures should be susceptible to treatment with GABA modulating drugs such as benzodiazepines, barbiturates, propofol, or neurosteroids.
在环境中释放或自愿摄入后，罗地亚炸药（RDX）可引发野生动物和人类癫痫发作。在越南战争期间，RDX 中毒是美国军人全身性癫痫发作的最常见原因，在武装部队的某些部门，至今仍有人将食用 RDX 作为“挑战”。在其作用机制长期未知的情况下，RDX 最近被证明是 GABA 受体拮抗剂。我们在此确定了 RDX 对 10 种重组表达的 GABA 受体的亚型选择性，并绘制了其功能结合位点。
我们使用全细胞膜片钳技术来确定 RDX 对 10 种重组表达的 GABA 受体的效力，并使用罗塞塔分子建模和定点突变相结合的方法来绘制 RDX 结合位点。
我们发现 RDX 可逆地抑制 α1β2γ2 GABA 受体，IC 为 23 μmol/L（95%CI 15.1-33.3 μmol/L），而包含 α4 和 α6 的 GABA 受体组合的敏感性则低 4-10 倍。RDX 与非竞争性拮抗剂（NCA）结合位点结合。在基于 α1β2γ2 受体静息状态冷冻电镜结构的分子模型中，RDX 与 T6'环上的苏氨酸形成两个氢键，并与 α1 或 β2 亚基 2'位的缬氨酸和丙氨酸形成疏水相互作用。
我们的研究结果从原子水平上描述了 RDX 的作用机制，并表明 RDX 诱导的癫痫发作应该对 GABA 调节药物（如苯二氮䓬类、巴比妥类、丙泊酚或神经甾体）敏感。
