Negative and positive allosteric modulators of the P2X₇ receptor

Abstract

Background and purpose: Antagonist effects at the P2X 7 receptor are complex with many behaving in a non-competitive manner. In this study, the effects of N- [2-({2-[(2-hydroxyethyl) ylacetamide (compound-17) and N 2 -(3,4-difluorophenyl)-N 1 -[2-methyl-5-(1-piperazinylmethyl)phenyl]glycinamide dihydrochloride (GW791343) on P2X 7 receptors were examined and their mechanism of action explored. Experimental approach: Antagonist effects were studied by measuring agonist-stimulated ethidium accumulation in cells expressing human or rat recombinant P2X 7 receptors and in radioligand binding studies. Key results: Compound-17 and GW791343 were non-competitive inhibitors of human P2X 7 receptors. Receptor protection studies using decavanadate and pyridoxalphosphate-6-azophenyl-2',4 0 -disulphonic acid (PPADS) showed that neither compound-17 nor GW791343 competitively interacted at the ATP binding site and so were probably negative allosteric modulators of the P2X 7 receptor. GW791343 prevented the slowly reversible blockade of the human P2X 7 receptor produced by compound-17 and inhibited [ 3 H]-compound-17 binding to the P2X 7 receptor suggesting they may bind to similar or interacting sites. At rat P2X 7 receptors, compound-17 was a negative allosteric modulator but the predominant effect of GW791343 was to increase agonist responses. Antagonist interaction and radioligand binding studies revealed that GW791343 did not interact at the ATP binding site but did interact with the compound-17 binding site suggesting that GW791343 is a positive allosteric modulator of the rat P2X 7 receptor. Conclusions: Compound-17 was a negative allosteric modulator of human and rat P2X 7 receptors. GW791343 was a negative allosteric modulator of the human P2X 7 receptor but at the rat P2X 7 receptor its predominant effect was positive allosteric modulation. These compounds should provide valuable tools for mechanistic studies on P2X 7 receptors.

Natural compounds with P2X7 receptor-modulating properties

“…Taken together, the present findings should provide a solid basis for further studies to clarify the mechanism of negative or positive allosteric modulation of P2X7 [56]. Because high concentrations of these compounds may also modulate other receptor systems or ion channels like it is known for IVM [20], their selectivity must be verified in more detail.…”

CAY10593 inhibits the human P2X7 receptor independently of phospholipase D1 stimulation

“…Specific P2X7 antagonists including AZ10606120 [32], AZ11645373 [33] and A-438079 [34] have been characterised using cells expressing recombinant P2X7, however these antagonists have been far less studied on cells expressing endogenous (or native) P2X7. RPMI 8226 cells have been previously shown to express endogenous P2X7 [17,28,29].…”

Human P2X7 receptor activation induces the rapid shedding of CXCL16

“…2A). To confirm that ATP-induced shedding of CXCL16 was mediated by P2X7, cells were pre-incubated in the absence or presence of the P2X7 antagonists AZ10606120 [14] and KN-62 [15], and ATP-induced CXCL16…”