Characterization of a novel binding site sensitive to 5′-N-ethylcarboxamidoadenosine and cyclic AMP

Lorenzen, Anna; Groβekatthöfer, Birte; Kerst, Birgit; Guerra, Lili; Vogt, H.; Schwabe, U.

doi:10.1016/1043-6618(95)87051-2

Cited by 5 publications

(11 citation statements)

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“…In the adenosine A1 receptor system, a full agonist was shown to be maximally effective for the stimulation of [ 35 S]GTP␥S binding at a higher concentration of GDP than a partial agonist (32). Similar results were found in the mu opioid system, where increasing the concentration of GDP increased relative efficacy differences among agonists (33).…”

supporting

confidence: 72%

“…Studies with adenosine receptors in membranes showed that the magnitude of agonistinduced release of [ 3 H]GDP from membranes corresponded to agonist efficacy (32). In the current study, experiments measuring the effect of different cannabinoid agonists on GDP binding affinities indicated that the mechanism of agonist efficacy is the magnitude of the decrease in G-protein affinity for GDP.…”

Section: Discussionmentioning

confidence: 81%

“…In other receptor systems, increasing the GDP concentration was reported to increase differences between full and partial agonists for stimulating [ 35 S]GTP␥S binding (32,33). Therefore, the relationship between GDP and cannabinoid agonist efficacy was directly explored using a few representative cannabinoid ligands.…”

Section: Materials-malementioning

confidence: 99%

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Cannabinoid Receptor Agonist Efficacy for Stimulating [35S]GTPγS Binding to Rat Cerebellar Membranes Correlates with Agonist-induced Decreases in GDP Affinity

Breivogel

Selley

Childers

1998

Journal of Biological Chemistry

166

135

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Cannabinoid receptors mediate the actions of ⌬ 9 -tetrahydrocannabinol (⌬ 9 -THC) 1 and other cannabimimetic ligands (1). To date, two types of cannabinoid receptors have been discovered, CB1 (2, 3) and CB2 (4). A splice variant of CB1, termed CB1A, has also been reported (5). Apart from a recent report of CB2 in mouse cerebellum (6), CB1 has been the only cannabinoid receptor found in brain. All cannabinoid receptors discovered to date belong to the superfamily of G-protein-coupled receptors (3, 4); their effectors include inhibition of adenylyl cyclase (7, 8), inhibition of calcium influx (9), and activation of inwardly rectifying potassium channels (10, 11). The physiological actions of cannabinoid ligands have been shown to be mediated through the activation of pertussis toxin-sensitive G-proteins (G i ␣ and G o ␣ subtypes) (7, 12), although some effects have been implicated via G s ␣ as well (13, 14).G-proteins are heterotrimeric proteins that transduce the agonist binding signal from G-protein-coupled receptors to effectors (15, 16). Upon activation by an agonist-occupied receptor, the ␣ subunit of a G-protein (G␣) releases bound GDP, binds a molecule of GTP, and dissociates from the G-protein ␤␥ subunit complex. Both G␣ and ␤␥ subunits act upon effectors until G␣ cleaves the bound GTP to GDP by its intrinsic GTPase activity, and G␣ re-associates with a ␤␥ dimer (15, 16). The cycle is then complete, and the heterotrimeric G-protein is able to be activated again. Receptors act catalytically, as one receptor can activate multiple G-proteins (17)(18)(19). The activation and dissociation of the G-protein subunits occur very rapidly and thus do not appear to be rate-limiting steps in the signal transduction cascade (20). However, since the actions of G-protein-coupled receptors are mediated strictly via the activation of G-proteins, this step plays a key role in determining overall agonist efficacy (21) and may be the most relevant step in measuring agonist efficacy at G-protein-coupled receptors (22).Agonist-stimulated binding of the hydrolysis-resistant GTP analog, [35 S]GTP␥S, to G-protein ␣ subunits measures receptor activation of G-proteins in purified and reconstituted systems (23), native cell membrane preparations (24), and brain sections (25). The present study focuses on three aspects of the role of GDP in the agonist-stimulated [35 S]GTP␥S binding assay. First, GDP has been shown to decrease basal [35 S]GTP␥S binding and allow detection of agonist stimulation. The requirement for micromolar concentrations of GDP to observe agonist effects in native membrane preparations has been reported consistently in every system for which agonist-stimulated [ 35 S]GTP␥S binding has been demonstrated (24, 26 -28

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supporting

confidence: 72%

Section: Discussionmentioning

confidence: 81%

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Cannabinoid Receptor Agonist Efficacy for Stimulating [35S]GTPγS Binding to Rat Cerebellar Membranes Correlates with Agonist-induced Decreases in GDP Affinity

Breivogel

Selley

Childers

1998

Journal of Biological Chemistry

166

135

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“…A 3 ARs. 7,18 EC 50 values for 10 and 12 at the A 1 AR were 2.89±0.14 μM (30±1% efficacy) and 2.28±0.99 μM (40±8% efficacy), respectively. Thus these two 2′-deoxy analogues, 10 and 12, were weak, partial agonists at the A 1 AR.…”

Section: Agonist Efficacy Of Selected Adenosine Derivatives Was Determentioning

confidence: 94%

Ring-Constrained (N)-Methanocarba nucleosides as adenosine receptor agonists: independent 5′-Uronamide and 2′-deoxy modifications

Lee

Ravi

et al. 2001

Bioorganic & Medicinal Chemistry Letters

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“…At least two to three separate experiments were performed, each in duplicate or triplicate. , NEN) in a total volume of 200 mL in 50 mm Tris-HCl buffer pH 7.4 containing 1 mm EDTA, 5 mm MgCl 2 , 1 mm dithiothreitol, 10 mm GDP, 100 mm NaCl, 2 IUmL À1 adenosine deaminase (ADA), 0.5 % bovine serum albumin and test compound, according to Lorenzen et al [38] Adenosine (10 nm) was added to prove that the amount of ADA was sufficient to remove endogenous adenosine as well as the added adenosine (data not shown). Nonspecific binding was determined by using 10 mm of unlabeled GTPgS.…”

Section: -Amino-1-(1-phenylethyl)-3-propyluracil ((R)-2 a And (S)-2 A)mentioning

confidence: 99%

Improving Potency, Selectivity, and Water Solubility of Adenosine A₁ Receptor Antagonists: Xanthines Modified at Position 3 and Related Pyrimido[1,2,3‐cd]purinediones

et al. 2006

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The structure-activity relationships of xanthine derivatives related to the adenosine A(1) receptor antagonists 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) and 1,3-dipropyl-8-(3-noradamantyl)xanthine (KW3902) were investigated by focusing on variations of the 3-substituent. Aromatic residues were well tolerated by the A(1) receptor in that position. A moderate effect of stereochemistry was found for the 3-(1-phenylethyl)-substituted analogue of DPCPX (S>R) at A(1) and A(3) receptors, whereas the opposite stereoselectivity was observed at the A(2) receptor subtypes. A 3-hydroxypropyl substituent was found to be optimal for high A(1) affinity and selectivity. The most potent compound of the present series was 1-butyl-3-(3-hydroxypropyl)-8-(3-noradamantyl)xanthine (10 c), which exhibits a K(i) value of 0.124 nM at rat, and 0.7 nM at human adenosine A(1) receptors, combined with high selectivity (>>200-fold) versus the other receptor subtypes. The similarly potent 8-cyclopentyl-3-(3-hydroxypropyl)-1-propylxanthine was converted into a water-soluble phosphate prodrug, which may become a useful pharmacological tool for in vivo studies. 8-Alkyl-2-(3-noradamantyl)pyrimido[1,2,3-cd]purine-8,10-diones, which can be envisaged as xanthine analogues with a fixed 3-propyl substituent, were identified as a new class of potent, selective adenosine A(1) receptor antagonists. For example, compound 14 (8-butyl-substituted) exhibits a K(i) value of 13.8 nM at human A(1) receptors. A selection of the most potent compounds was investigated in [(35)S]GTPgammaS binding assays and showed inverse agonistic activity. Their efficacy was generally lower than that of the full inverse agonist DPCPX, and depended on subtle structural changes. Some of the new compounds belong to the most potent and selective A(1) antagonists described to date.

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Characterization of a novel binding site sensitive to 5′-N-ethylcarboxamidoadenosine and cyclic AMP

Cited by 5 publications

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Cannabinoid Receptor Agonist Efficacy for Stimulating [35S]GTPγS Binding to Rat Cerebellar Membranes Correlates with Agonist-induced Decreases in GDP Affinity

Cannabinoid Receptor Agonist Efficacy for Stimulating [35S]GTPγS Binding to Rat Cerebellar Membranes Correlates with Agonist-induced Decreases in GDP Affinity

Ring-Constrained (N)-Methanocarba nucleosides as adenosine receptor agonists: independent 5′-Uronamide and 2′-deoxy modifications

Improving Potency, Selectivity, and Water Solubility of Adenosine A₁ Receptor Antagonists: Xanthines Modified at Position 3 and Related Pyrimido[1,2,3‐cd]purinediones

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Characterization of a novel binding site sensitive to 5′-N-ethylcarboxamidoadenosine and cyclic AMP

Cited by 5 publications

References 0 publications

Cannabinoid Receptor Agonist Efficacy for Stimulating [35S]GTPγS Binding to Rat Cerebellar Membranes Correlates with Agonist-induced Decreases in GDP Affinity

Cannabinoid Receptor Agonist Efficacy for Stimulating [35S]GTPγS Binding to Rat Cerebellar Membranes Correlates with Agonist-induced Decreases in GDP Affinity

Ring-Constrained (N)-Methanocarba nucleosides as adenosine receptor agonists: independent 5′-Uronamide and 2′-deoxy modifications

Improving Potency, Selectivity, and Water Solubility of Adenosine A1 Receptor Antagonists: Xanthines Modified at Position 3 and Related Pyrimido[1,2,3‐cd]purinediones

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Improving Potency, Selectivity, and Water Solubility of Adenosine A₁ Receptor Antagonists: Xanthines Modified at Position 3 and Related Pyrimido[1,2,3‐cd]purinediones