Baur Roland, Tan Kelly R, Lüscher Benjamin P, Gonthier Anne, Goeldner Maurice, Sigel Erwin
Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.
J Neurochem. 2008 Sep;106(6):2353-63. doi: 10.1111/j.1471-4159.2008.05574.x. Epub 2008 Jul 15.
Classical benzodiazepines, for example diazepam, interact with alpha(x)beta(2)gamma(2) GABA(A) receptors, x = 1, 2, 3, 5. Little is known about effects of alpha subunits on the structure of the binding pocket. We studied here the interaction of the covalently reacting diazepam analog 7-Isothiocyanato-5-phenyl-1,3-dihydro-2H-1,4-benzodiazepin-2-one (NCS compound) with alpha(1)H101Cbeta(2)gamma(2) and with receptors containing the homologous mutation, alpha(2)H101Cbeta(2)gamma(2), alpha(3)H126Cbeta(2)gamma(2) and alpha(5)H105Cbeta(2)gamma(2). This comparison was extended to alpha(6)R100Cbeta(2)gamma(2) receptors as this mutation conveys to these receptors high affinity towards classical benzodiazepines. The interaction was studied at the ligand binding level and at the functional level using electrophysiological techniques. Results indicate that the geometry of alpha(6)R100Cbeta(2)gamma(2) enables best interaction with NCS compound, followed by alpha(3)H126Cbeta(2)gamma(2), alpha(1)H101Cbeta(2)gamma(2) and alpha(2)H101Cbeta(2)gamma(2), while alpha(5)H105Cbeta(2)gamma(2) receptors show little interaction. Our results allow conclusions about the relative apposition of alpha(1)H101 and homologous positions in alpha(2), alpha(3), alpha(5) and alpha(6) with the position occupied by -Cl in diazepam. During this study we found evidence for the presence of a novel site for benzodiazepines that prevents modulation of GABA(A) receptors via the classical benzodiazepine site. The novel site potentially contributes to the high degree of safety to some of these drugs. Our results indicate that this site may be located at the alpha/beta subunit interface pseudo-symmetrically to the site for classical benzodiazepines located at the alpha/gamma interface.
经典苯二氮䓬类药物，如地西泮，与α(x)β₂γ₂ GABA(A)受体相互作用，其中x = 1、2、3、5。关于α亚基对结合口袋结构的影响知之甚少。我们在此研究了共价反应性地西泮类似物7-异硫氰酸酯-5-苯基-1,3-二氢-2H-1,4-苯并二氮杂䓬-2-酮（NCS化合物）与α₁H₁₀₁Cβ₂γ₂以及含有同源突变的受体α₂H₁₀₁Cβ₂γ₂、α₃H₁₂₆Cβ₂γ₂和α₅H₁₀₅Cβ₂γ₂之间的相互作用。这种比较扩展到了α₆R₁₀₀Cβ₂γ₂受体，因为这种突变赋予这些受体对经典苯二氮䓬类药物的高亲和力。使用电生理技术在配体结合水平和功能水平上研究了这种相互作用。结果表明，α₆R₁₀₀Cβ₂γ₂的几何结构与NCS化合物的相互作用最佳，其次是α₃H₁₂₆Cβ₂γ₂、α₁H₁₀₁Cβ₂γ₂和α₂H₁₀₁Cβ₂γ₂，而α₅H₁₀₅Cβ₂γ₂受体的相互作用较弱。我们的结果得出了关于α₁H₁₀₁以及α₂、α₃、α₅和α₆中的同源位置与地西泮中-Cl所占据位置的相对并置情况的结论。在这项研究中，我们发现了存在一个新的苯二氮䓬类药物位点的证据，该位点可防止通过经典苯二氮䓬类药物位点对GABA(A)受体进行调节。这个新位点可能是这些药物具有高度安全性的原因之一。我们的结果表明，这个位点可能位于α/β亚基界面，与位于α/γ界面的经典苯二氮䓬类药物位点呈伪对称。
