Abstract

There are few antagonists selective for subtypes of the several P2X receptors, but these are needed to identify the receptors expressed on native cells and tissues. In particular, P2X₄ and P2X₇ receptor subunits are colocalized on immune, epithelial, and exocrine gland cells, but both are relatively insensitive to suramin and pyridoxal-5-phosphate-6-azo-2′,4′-disulfonic acid derivative. In this article, we show that Coomassie Brilliant Blue G selectively inhibits P2X₇ receptors with nanomolar affinity. We measured currents in response to P2X receptor activation in HEK293 cells heterologously expressing human or rat P2X₁, P2X₂, P2X₃, P2X_2/3, P2X₄, P2X_1/5, and P2X₇ receptors. Brilliant Blue G produced a noncompetitive inhibition of rat and human P2X₇ receptors with IC₅₀ values of 10 and 200 nM, respectively. IC₅₀ values for inhibition of the other receptors ranged from 2 to >30 μM; the rat and human P2X₄ receptors showed IC₅₀ values of >10 and 3.2 μM. Coomassie Blue G also blocked YO-PRO1 uptake and membrane blebbing, which are uniquely associated with activation of P2X₇ receptors. Thus, Brilliant Blue G is at least 1000-fold more potent at rat P2X₇ receptors than at rat P2X₄ receptors.