作者: Oliveira, Jonas I. N. ; Manzoni, Vinícius ; Barbosa, Emmanuel D. ; Soares-Rachetti, Vanessa P. ; Albuquerque, Eudenilson L. ; Lima Neto, José X. ; Bezerra, Katyanna S. ; Fulco, Umberto L.

GABA_B is a G protein-coupled receptor that functions as a constitutive heterodimer composed of the GABA_B1a/b and GABA_B2 subunits. It mediates slow and prolonged inhibitory neurotransmission in the nervous system, representing an attractive target for the treatment of various disorders. However, the molecular mechanism of the GABA_B receptor is not thoroughly understood. Therefore, a better description of the binding of existing agonists and antagonists to this receptor is crucial to improve our knowledge about G protein-coupled receptor structure as well as for helping the development of new potent and more selective therapeutic agents. In this work, we used the recent X-ray cocrystallization data of agonists (GABA and baclofen) and antagonists (2-hydroxysaclofen, SCH50911, and CGP54626) bound to the GABA_B orthosteric site together with quantum biochemistry and the molecular fractionation with conjugate caps (MFCC) scheme to describe the individual contribution of each amino acid residue involved in the GABA_B-ligand interaction, pointing out differences and similarities among the compounds. Our quantum biochemical computational results show that the total binding energy of the ligands to the GABA_B ligand pocket, with radius varying from 2.0 to 9.0 Å, is well-correlated with the experimental binding affinity. In addition, we found that the binding site is very similar for agonists or antagonists, showing small differences in the importance of the most significant amino acids. Finally, we predict the energetic relevance of the regions of the five ligands as well as the influence of each protein lobe on GABA_B-ligand binding. These results provide important new information on the binding mechanism of the GABA_B receptor and should facilitate the development of new chemicals targeting this receptor.

2016-11-01·European Journal of Pharmacology3区 · 医学

In vitro and in vivo pharmacological characterization of SSD114, a novel GABAB positive allosteric modulator

3区 · 医学

Article

作者: Solinas, Maurizio ; Castelli, M Paola ; Giunta, Daniela ; Porcu, Alessandra ; Mugnaini, Claudia ; Lobina, Carla

Positive allosteric modulators (PAMs) of the GABA_B receptor have emerged as a novel approach to the pharmacological manipulation of the GABA_B receptor, enhancing the effects of receptor agonists with few side effects. Here, we identified N-cyclohexyl-4-methoxy-6-(4-(trifluoromethyl)phenyl)pyrimidin-2-amine (SSD114) as a new compound with activity as a GABA_B PAM in in vitro and in vivo assays. SSD114 potentiated GABA-stimulated [³⁵S]GTPγS binding to native GABA_B receptors, whereas it had no effect when used alone. Its effect on GTPγS stimulation was suppressed when GABA-induced activation was blocked with CGP54626, a competitive antagonist of the GABA_B receptor. SSD114 failed to potentiate WIN55,212,2-, morphine- and quinpirole-induced [³⁵S]GTPγS binding to cortical and striatal membranes, respectively, indicating that it is a selective GABA_B PAM. Increasing SSD114 fixed concentrations induced a leftward shift of the GABA concentration-response curve, enhancing the potency of GABA rather than its efficacy. SSD114 concentration-response curves in the presence of fixed concentrations of GABA (1, 10, and 20μM) revealed a potentiating effect on GABA-stimulated binding of [³⁵S]GTPγS to rat cortical membranes, with EC₅₀ values in the low micromolar range. Bioluminescence resonance energy transfer (BRET) experiments in Chinese Hamster Ovary (CHO)-cells expressing GABA_B receptors showed that SSD114 potentiates the GABA inhibition of adenylyl-cyclase mediated by GABA_B receptors. Our compound is also effective in vivo potentiating baclofen-induced sedation/hypnosis in mice, with no effect when tested alone. These findings indicate that SSD114, a molecule with a different chemical structure compared to known GABA_B PAMs, is a novel GABA_B PAM with potential usefulness in the GABA_B-receptor research field.

2013-04-01·Journal of Neurophysiology3区 · 医学

A novel GABAergic action mediated by functional coupling between GABA_B-like receptor and two different high-conductance K⁺channels in cricket Kenyon cells

3区 · 医学

Article

作者: Yoshino, Masami ; Nakamura, Atsunao

The γ-aminobutyric acid type B (GABAB) receptor has been shown to attenuate high-voltage-activated Ca2+currents and enhance voltage-dependent or inwardly rectifying K+currents in a variety of neurons. In this study, we report a novel coupling of GABAB-like receptor with two different high-conductance K+channels, Na+-activated K+(KNa) channel and Ca2+-activated K+(KCa) channel, in Kenyon cells isolated from the mushroom body of the cricket brain. Single-channel activities of KNaand KCachannels in response to bath applications of GABA and the GABAB-specific agonist SKF97541 were recorded with the cell-attached patch configuration. The open probability ( Po) of both KNaand KCachannels was found to be increased by bath application of GABA, and this increase in Powas antagonized by coapplication of the GABABantagonist CGP54626, suggesting that GABAB-like receptors mediate these actions. Similarly, GABAB-specific agonist SKF97541 increased the Poof both KNaand KCachannels. Perforated-patch recordings using β-escin further revealed that SKF97541 increased the amplitude of the outward currents elicited by step depolarizations. Under current-clamp conditions, SKF97541 decreased the firing frequency of spontaneous action potential (AP) and changed the AP waveform. The amplitude and duration of AP were decreased, whereas the afterhyperpolarization of AP was increased. Resting membrane potential, however, was not significantly altered by SKF97541. Taken together, these results suggest that GABAB-like receptor is functionally coupled with both KNaand KCachannels and this coupling mechanism may serve to prevent AP formation and limit excitatory synaptic input.

100 项与 CGP-54626 相关的药物交易

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