A Family of Highly Selective Allosteric Modulators of the Metabotropic Glutamate Receptor Subtype 5
作者:Julie A. O'Brien、Wei Lemaire、Tsing-Bau Chen、Raymond S. L. Chang、Marlene A. Jacobson、Sookhee N. Ha、Craig W. Lindsley、Hervé J. Schaffhauser、Cyrille Sur、Douglas J. Pettibone、P. Jeffrey Conn、David L. Williams
DOI:10.1124/mol.64.3.731
日期:2003.9
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 μM range, and at 10 to 100 μM, 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 μM 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.
我们已鉴定出一类高度选择性的别构调节剂,用于I类代谢型谷氨酸受体亚型5(mGluR5)。这一类紧密相关的类化合物表现出了一系列效果,从正别构调节到负别构调节,并包括一些不直接调节mGluR5激动剂活性的化合物,而是防止其他家族成员发挥其调节作用。3,3′-二氟苯腈(DFB)没有激动剂活性,但作为人类和大鼠mGluR5的选择性正别构调节剂。DFB在荧光钙离子测定中能使谷氨酸、奎奎酸和3,5-二羟基苯基甘氨酸的阈值反应增强3到6倍,EC50值在2到5μM范围内,而在10到100μM时,它将mGluR5激动剂浓度-反应曲线向左移动约2倍。类化合物3,3′-二甲氧基苯腈(DMeOB)作为mGluR5激动剂活性的负调节剂,其IC50值为3μM,而类化合物3,3′-二氯苯腈(DCB)对mGluR5活性没有显著的调节效果。然而,DCB似乎作为具有中性协同性的别构配体,防止DFB对mGluRs的正别构调节以及DMeOB的负调节效应。这些类化合物均不影响[3H]奎奎酸与正位(谷氨酸)结合位点的结合,但它们确实抑制了[3H]3-甲氧基-5-(2-吡啶乙炔基)吡啶与2-甲基-6-(苯乙炔基)吡啶结合位点的结合,后者是一种已知的负别构调节剂。通过使用这些化合物,我们提供了证据表明GPCR上的别构位点能够对紧密相关的配体作出反应,这些配体具有从正调节到负调节以及对此调节的中性竞争等一系列药理活性。