Greenwood Jeremy R, Mewett Ken N, Allan Robin D, Martín Belén Ortiz, Pickering Darryl S
Department of Medicinal Chemistry, Danish University of Pharmaceutical Sciences, Universitetsparken 2, DK 2100 Copenhagen, Denmark.
Neuropharmacology. 2006 Jul;51(1):52-9. doi: 10.1016/j.neuropharm.2006.02.013. Epub 2006 Apr 24.
Three positional isomers (compounds 1, 2, and 3) of 1-uracilylalanine (willardiine) based on a 3-hydroxypyridazine 1-oxide scaffold with an alanine side-chain at positions 4 (1), 5 (2) or 6 (3) were tested for binding to recombinant homomeric AMPA receptor (AMPA-R) subtypes GluR1-4, as well for excitatory activity on the rat cortical wedge preparation. 1 had approximately 30 times higher affinity than willardiine while showing a similar selectivity profile, i.e. 22-fold selectivity for GluR1/2 over GluR3/4. The GluR1-4 affinities of 3 were similar to 1, however, its 31-fold selectivity for GluR1/2 over GluR3/4 is the highest yet observed among azine-based glutamate analogues. The non-isosteric congener 2 showed weaker binding to AMPA-Rs. In the cortical wedge, 1 evokes similar responses to AMPA, while 3 and 2 are 10- and 100-fold weaker, respectively. Dose-response curves on Xenopus laevis oocytes expressing GluR1-4(flip) confirmed that 1 and 3 are potent GluR1/2 receptor agonists (EC(50)s from 0.26 to 1.7microM) but are 10- to 160-fold less potent at GluR3/4. The structures, potencies and selectivities of this new class of AMPA agonists are compared with those of willardiine, 5-fluorowillardiine and azawillardiine, referring to the binding mode observed in the crystal structure of willardiine bound to GluR2-S1S2. The results indicate that the 3-hydroxypyridazine 1-oxide moiety can function as an outstanding carboxylate mimic at AMPA-Rs, leading the way to further fine-tuning of subtype selectivity. This little-explored molecular motif may find wider application in medicinal chemistry.
基于3-羟基哒嗪1-氧化物支架、在4位（化合物1）、5位（化合物2）或6位（化合物3）带有丙氨酸侧链的1-尿嘧啶基丙氨酸（鹅膏蕈氨酸）的三种位置异构体，被测试与重组同聚AMPA受体（AMPA-R）亚型GluR1-4的结合情况，以及对大鼠皮质楔形标本的兴奋活性。化合物1的亲和力比鹅膏蕈氨酸高约30倍，同时显示出相似的选择性特征，即对GluR1/2的选择性比对GluR3/4高22倍。化合物3对GluR1-4的亲和力与化合物1相似，然而，其对GluR1/2比对GluR3/4的31倍选择性是在嗪基谷氨酸类似物中迄今观察到的最高值。非等排类似物2与AMPA-Rs的结合较弱。在皮质楔形标本中，化合物1引起的反应与AMPA相似，而化合物3和2分别弱10倍和100倍。在表达GluR1-4（翻转）的非洲爪蟾卵母细胞上的剂量-反应曲线证实，化合物1和3是有效的GluR1/2受体激动剂（EC50为0.26至1.7微摩尔），但对GluR3/4的效力低10至160倍。将这类新的AMPA激动剂的结构、效力和选择性与鹅膏蕈氨酸、5-氟鹅膏蕈氨酸和氮杂鹅膏蕈氨酸的进行比较，并参考在与GluR2-S1S2结合的鹅膏蕈氨酸晶体结构中观察到的结合模式。结果表明，3-羟基哒嗪1-氧化物部分在AMPA-Rs处可作为出色的羧酸盐模拟物，为进一步微调亚型选择性指明了方向。这个研究较少的分子基序可能在药物化学中有更广泛的应用。
