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Cibacron blue allosterically modulates the rat P2X4 receptor
K J Miller1, A D Michel, I P Chessell
1Glaxo Institute of Applied Pharmacology, Department of Pharmacology, University of Cambridge, UK. ADM7393@glaxowellcome.co.uk
Neuropharmacology
|January 14, 1999
Summary
Cibacron blue acts as a weak antagonist or potentiator of P2X4 receptors, unlike its inhibitory effect on P2X2 receptors. This suggests cibacron blue allosterically regulates P2X4 receptor function, similar to zinc.
Area of Science:
- Pharmacology
- Neuroscience
- Molecular Biology
Background:
- Purinergic signaling via P2 receptors is crucial in cellular communication.
- P2X4 receptors are ligand-gated ion channels activated by adenosine triphosphate (ATP).
- Understanding P2X receptor modulation is key for developing targeted therapeutics.
Purpose of the Study:
- To characterize the effects of cibacron blue on rat recombinant P2X4 and P2X2 receptors.
- To investigate the potential allosteric modulation of P2X4 receptors by cibacron blue.
- To compare cibacron blue's actions with known modulators like zinc.
Main Methods:
- Whole-cell patch clamp electrophysiology was employed.
- Experiments were conducted on human embryonic kidney 293 (HEK293) cells stably expressing P2X4 or P2X2 receptors.
- Cell rafts (20-40 electrically coupled cells) were used to overcome current rundown.
Main Results:
- Cibacron blue weakly antagonized P2X4 receptors (IC50 > 300 µM) but potentiated ATP-evoked currents at lower concentrations (3-30 µM).
- Potentiation involved increased ATP potency (up to 4-fold) without altering maximum current.
- Cibacron blue inhibited P2X2 receptor activity (IC50 ≈ 600-800 nM).
- Effects on P2X4 receptors mirrored those of Zn2+, suggesting allosteric regulation.
Conclusions:
- Cibacron blue exhibits dual activity on P2X4 receptors: weak antagonism and potentiation.
- The potentiating effect of cibacron blue on P2X4 receptors is concentration-dependent and suggests allosteric modulation.
- Cibacron blue's differential effects on P2X4 and P2X2 receptors highlight subtype-specific interactions.