An Allosteric Inhibitory Site Conserved in the Ectodomain of P2X Receptor Channels

AbstractThe P2X7 receptor, originally known as the P2Z receptor due to its distinctive functional properties, has a structure characteristic of the ATP-gated ion channel P2X receptor family. The P2X7 receptor is an important mediator of ATP-induced purinergic signalling and is involved the pathogenesis of numerous conditions as well as in the regulation of diverse physiological functions. Functional characterisations, in conjunction with site-directed mutagenesis, molecular modelling, and, recently, structural determination, have provided significant insights into the structure–function relationships of the P2X7 receptor. This review discusses the current understanding of the structural basis for the functional properties of the P2X7 receptor.

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Antagonism of endogenous putative P2Y receptors reduces the growth of MDCK-derived cysts cultured in vitro

AJP Renal Physiology ◽

10.1152/ajprenal.00103.2006 ◽

2007 ◽

Vol 292 (1) ◽

pp. F15-F25 ◽

Cited By ~ 25

Author(s):

Clare M. Turner ◽

Brian F. King ◽

Kaila S. Srai ◽

Robert J. Unwin

Keyword(s):

Therapeutic Potential ◽

Cyst Formation ◽

P2y Receptors ◽

P2x Receptor ◽

P2y Receptor ◽

Cyst Size ◽

Reactive Blue 2 ◽

Cyst Growth

P2Y receptors couple to G proteins and either mobilize intracellular Ca2+ or alter cAMP levels to modulate the activity of Ca2+- and cAMP-sensitive ion channels. We hypothesize that increased ion transport into the lumen of MDCK cysts can osmotically drive fluid movement and increase cyst size. Furthermore, activation of the adenylate cyclase/cAMP pathway may trigger cell proliferation via an extracellular signal-related kinase cascade. To test this hypothesis, several P2Y receptor inhibitors were used on the MDCK in vitro model of renal cyst formation. The nonspecific P2 receptor inhibitors reactive blue 2 and suramin reduced cyst growth significantly, as did PPADS and, to a lesser extent, the P2Y1-specific antagonist MRS2179. Cyst growth was reduced by ∼50% when ATP was removed from the culture medium with apyrase, although stable analogs of ATP failed to increase cyst size. The nonselective P2X receptor inhibitor Coomassie brilliant blue G was ineffective at reducing cyst growth, suggesting no involvement of P2X receptors. Finally, the presence of selective inhibitors of ERK activation (either PD98059 or U0126) greatly reduced cyst growth, whereas in untreated cysts ERK activity was observed to increase with time. We conclude that stimulation of endogenous P2Y receptors by extracellular ATP increases growth of MDCK cysts via cAMP-dependent activation of the ERK pathway. P2Y receptor antagonists may have therapeutic potential in reducing cyst size and slowing disease progression; although further studies in vitro and in vivo are needed to investigate the specificity and role of these P2Y receptors in renal cystic diseases.

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Validation of Alexa-647-ATP as a powerful tool to study P2X receptor ligand binding and desensitization

Biochemical and Biophysical Research Communications ◽

10.1016/j.bbrc.2013.07.058 ◽

2013 ◽

Vol 438 (2) ◽

pp. 295-300 ◽

Cited By ~ 6

Author(s):

Yogesh Bhargava ◽

Annette Nicke ◽

Jürgen Rettinger

Keyword(s):

Ligand Binding ◽

P2x Receptor ◽

Receptor Ligand

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Aurintricarboxylic acid is a potent inhibitor of phosphofructokinase

Biochemical Journal ◽

10.1042/bj2590925 ◽

1989 ◽

Vol 259 (3) ◽

pp. 925-927 ◽

Cited By ~ 27

Author(s):

S A McCune ◽

L G Foe ◽

R G Kemp ◽

R R Jurin

Keyword(s):

Protein Synthesis ◽

Fatty Acid ◽

Fatty Acid Synthesis ◽

Potent Inhibitor ◽

Rat Hepatocytes ◽

Acid Synthesis ◽

Rabbit Liver ◽

Irreversible Binding ◽

Aurintricarboxylic Acid ◽

Inhibitory Site

Aurintricarboxylic acid (ATA) was found to be a very potent inhibitor of purified rabbit liver phosphofructokinase (PFK), giving 50% inhibition at 0.2 microM. The inhibition was in a manner consistent with interaction at the citrate-inhibitory site of the enzyme. The data suggest that inhibition of PFK by ATA was not due to denaturation of the enzyme or the irreversible binding of inhibitor, since the inhibition could be reversed by addition of allosteric activators of PFK, i.e. fructose 2,6-bisphosphate or AMP. Two other tricarboxylic acids, agaric acid and (-)-hydroxycitrate, were found to inhibit PFK. ATA at much higher concentrations (500 microM) was shown to inhibit fatty acid synthesis from endogenous glycogen in rat hepatocytes; however, protein synthesis was not altered.

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Functional Coupling between the P2X7 Receptor and Pannexin-1 Channel in Rat Trigeminal Ganglion Neurons

International Journal of Molecular Sciences ◽

10.3390/ijms22115978 ◽

2021 ◽

Vol 22 (11) ◽

pp. 5978

Author(s):

Hiroyuki Inoue ◽

Hidetaka Kuroda ◽

Wataru Ofusa ◽

Sadao Oyama ◽

Maki Kimura ◽

...

Keyword(s):

Trigeminal Ganglion ◽

P2x7 Receptor ◽

P2x Receptor ◽

Functional Coupling ◽

Dependent Manner ◽

High Concentration ◽

Receptor Antagonists ◽

P2x7 Receptors ◽

Pannexin 1 ◽

Ganglion Neurons

The ionotropic P2X receptor, P2X7, is believed to regulate and/or generate nociceptive pain, and pain in several neuropathological diseases. Although there is a known relationship between P2X7 receptor activity and pain sensing, its detailed functional properties in trigeminal ganglion (TG) neurons remains unclear. We examined the electrophysiological and pharmacological characteristics of the P2X7 receptor and its functional coupling with other P2X receptors and pannexin-1 (PANX1) channels in primary cultured rat TG neurons, using whole-cell patch-clamp recordings. Application of ATP and Bz-ATP induced long-lasting biphasic inward currents that were more sensitive to extracellular Bz-ATP than ATP, indicating that the current was carried by P2X7 receptors. While the biphasic current densities of the first and second components were increased by Bz-ATP in a concentration dependent manner; current duration was only affected in the second component. These currents were significantly inhibited by P2X7 receptor antagonists, while only the second component was inhibited by P2X1, 3, and 4 receptor antagonists, PANX1 channel inhibitors, and extracellular ATPase. Taken together, our data suggests that autocrine or paracrine signaling via the P2X7-PANX1-P2X receptor/channel complex may play important roles in several pain sensing pathways via long-lasting neuronal activity driven by extracellular high-concentration ATP following tissue damage in the orofacial area.

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