O'Brien Julie A, Lemaire Wei, Chen Tsing-Bau, Chang Raymond S L, Jacobson Marlene A, Ha Sookhee N, Lindsley Craig W, Schaffhauser Hervé J, Sur Cyrille, Pettibone Douglas J, Conn P Jeffrey, Williams David L
Neuroscience-WP46-300, Merck Research Laboratories, West Point, PA 19486, USA.
Mol Pharmacol. 2003 Sep;64(3):731-40. doi: 10.1124/mol.64.3.731.
We have identified a family of highly selective allosteric modulators of the group I metabotropic glutamate receptor subtype 5 (mGluR5). This family of closely related analogs exerts a spectrum of effects, ranging from positive to negative allosteric modulation, and includes compounds that do not themselves modulate mGluR5 agonist activity but rather prevent other family members from exerting their modulatory effects. 3,3'-Difluorobenzaldazine (DFB) has no agonist activity, but it acts as a selective positive allosteric modulator of human and rat mGluR5. DFB potentiates threshold responses to glutamate, quisqualate, and 3,5-dihydroxyphenylglycine in fluorometric Ca2+ assays 3- to 6-fold, with EC50 values in the 2 to 5 microM range, and at 10 to 100 microM, it shifts mGluR5 agonist concentration-response curves approximately 2-fold to the left. The analog 3,3'-dimethoxybenzaldazine (DMeOB) acts as a negative modulator of mGluR5 agonist activity, with an IC50 of 3 microM in fluorometric Ca2+ assays, whereas the analog 3,3'-dichlorobenzaldazine (DCB) does not exert any apparent modulatory effect on mGluR5 activity. However, DCB seems to act as an allosteric ligand with neutral cooperativity, preventing the positive allosteric modulation of mGluRs by DFB as well as the negative modulatory effect of DMeOB. None of these analogs affects binding of [3H]quisqualate to the orthosteric (glutamate) site, but they do inhibit [3H]3-methoxy-5-(2-pyridinylethynyl)pyridine binding to the site for 2-methyl-6-(phenylethynyl)-pyridine, a previously identified negative allosteric modulator. With the use of these compounds, we provide evidence that allosteric sites on GPCRs can respond to closely related ligands with a range of pharmacological activities from positive to negative modulation as well as to neutral competition of this modulation.
我们已鉴定出一组I型代谢型谷氨酸受体亚型5（mGluR5）的高选择性变构调节剂。这组密切相关的类似物具有一系列效应，从正变构调节到负变构调节，并且包括本身不调节mGluR5激动剂活性但能阻止其他家族成员发挥其调节作用的化合物。3,3'-二氟苯甲醛腙（DFB）没有激动剂活性，但它作为人和大鼠mGluR5的选择性正变构调节剂。在荧光钙测定中，DFB使对谷氨酸、喹啉酸和3,5-二羟基苯甘氨酸的阈值反应增强3至6倍，EC50值在2至5微摩尔范围内，并且在10至100微摩尔时，它使mGluR5激动剂浓度-反应曲线向左移动约2倍。类似物3,3'-二甲氧基苯甲醛腙（DMeOB）作为mGluR5激动剂活性的负调节剂，在荧光钙测定中的IC50为3微摩尔，而类似物3,3'-二氯苯甲醛腙（DCB）对mGluR5活性没有明显的调节作用。然而，DCB似乎作为具有中性协同作用的变构配体，阻止DFB对mGluRs的正变构调节以及DMeOB的负调节作用。这些类似物均不影响[3H]喹啉酸与正位（谷氨酸）位点的结合，但它们确实抑制[3H]3-甲氧基-5-（2-吡啶基乙炔基）吡啶与2-甲基-6-（苯乙炔基）-吡啶位点的结合，2-甲基-6-（苯乙炔基）-吡啶是先前鉴定的负变构调节剂。通过使用这些化合物，我们提供了证据表明GPCR上的变构位点可以对具有从正调节到负调节以及这种调节的中性竞争等一系列药理活性的密切相关配体作出反应。
