Wilcox R A, Challiss R A, Traynor J R, Fauq A H, Ognayanov V I, Kozikowski A P, Nahorski S R
Department of Cell Physiology and Pharmacology, University of Leicester, United Kingdom.
J Biol Chem. 1994 Oct 28;269(43):26815-21.
Several novel D-myo-inositol 1,4,5-trisphosphate (Ins(1,4,5)P3] analogues equatorially substituted at the 3-position have been synthesized to probe the structure-activity relationship of the Ins(1,4,5)P3-receptor subsite adjacent to the native 3-hydroxy (3-OH) of Ins(1,4,5)P3. This study was prompted, in part, by our observation that myo-inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4), the 3-position phosphorylated product of Ins(1,4,5)P3 was a full agonist at the Ca(2+)-mobilizing Ins(1,4,5)P3 receptor of SH-SY5Y cells (Wilcox, R.A., Challiss, R. A. J., Liu, C., Potter, B. V. I., and Nahorski, S. R. (1993) Mol. Pharmacol. 44, 810-817). The 3-position Ins(1,4,5)P3 analogues were equatorially substituted with groups spanning the steric range between the 3-OH of Ins(1,4,5)P3 and the 3-phosphate of Ins(1,3,4,5)P4; in order of increasing 3-position steric bulk these were: 3-fluoro-, 3-chloro-, 3-amino-, 3-bromo-, 3-methoxy-, and 3-phosphorothioate-Ins(1,4,5)P3. The analogues were assessed at the specific Ins(1,4,5)P3 binding-site of bovine adrenal cortex and for Ca2+ mobilizing activity in saponin-permeabilized SH-SY5Y human neuroblastoma cells. A correlation was observed between increasing molecular volume of the 3-position substituent and respective decreases in both affinity and Ca2+ mobilizing efficacy. Further analysis of the data also revealed that Ins(1,4,5)P3 analogues with equatorial 3-OH, 3-phosphate, and 3-phosphorothioate substituents interacted more favorably with Ins(1,4,5)P3 recognition sites than would be predicted by purely steric considerations. In contrast, 3-C-trifluoromethyl-Ins(1,4,5)P3 (which is axially substituted, but retains the native 3-OH of Ins(1,4,5)P3) interacted with Ins(1,4,5)P3 recognition sites with virtually the same potency as Ins(1,4,5)P3, indicating that the binding pocket of the Ins(1,4,5)P3-receptor was not sterically restrictive with respect to axially oriented 3-position substituents. We conclude that the Ins(1,4,5)P3 receptor has favorable non-covalent binding interactions with the equatorial 3-position substituents of Ins(1,4,5)P3 and Ins(1,3,4,5)P4 and that these interactions significantly ameliorate the steric constraints of the Ins(1,4,5)P3 receptor binding pocket.
已合成了几种在3位具有赤道取代基的新型D-肌醇1,4,5-三磷酸（Ins(1,4,5)P3）类似物，以探究Ins(1,4,5)P3受体亚位点与Ins(1,4,5)P3天然3-羟基（3-OH）相邻区域的构效关系。本研究部分是受我们的观察结果所推动，即Ins(1,4,5)P3的3位磷酸化产物肌醇1,3,4,5-四磷酸（Ins(1,3,4,5)P4）是SH-SY5Y细胞中Ca(2+)动员型Ins(1,4,5)P3受体的完全激动剂（威尔科克斯，R.A.，查利斯，R.A.J.，刘，C.，波特，B.V.I.，和纳霍尔斯基，S.R.（1993年）《分子药理学》44卷，810 - 817页）。3位Ins(1,4,5)P3类似物在赤道位置被取代基取代，这些取代基的空间范围跨越了Ins(1,4,5)P3的3-OH和Ins(1,3,4,5)P4的3-磷酸之间；按照3位空间体积增加的顺序，它们依次为：3-氟代-、3-氯代-、3-氨基-、3-溴代-、3-甲氧基-和3-硫代磷酸酯-Ins(1,4,5)P3。这些类似物在牛肾上腺皮质的特异性Ins(1,4,5)P3结合位点进行了评估，并在皂素通透的SH-SY5Y人神经母细胞瘤细胞中检测了其Ca2+动员活性。观察到3位取代基分子体积的增加与亲和力和Ca2+动员效力的相应降低之间存在相关性。对数据的进一步分析还表明，具有赤道3-OH、3-磷酸和3-硫代磷酸酯取代基的Ins(1,4,5)P3类似物与Ins(1,4,5)P3识别位点的相互作用比单纯的空间因素所预测的更为有利。相比之下，3-C-三氟甲基-Ins(1,4,5)P3（它是轴向取代的，但保留了Ins(1,4,5)P3的天然3-OH）与Ins(1,4,5)P3识别位点相互作用的效力与Ins(1,4,5)P3几乎相同，这表明Ins(1,4,5)P3受体的结合口袋对于轴向取向的3位取代基在空间上没有限制。我们得出结论，Ins(1,4,5)P3受体与Ins(1,4,5)P3和Ins(1,3,4,5)P4的赤道3位取代基具有良好的非共价结合相互作用，并且这些相互作用显著改善了Ins(1,4,5)P3受体结合口袋的空间限制。
