Allosteric control of gating and kinetics at P2X(4) receptor channels.
The CNS abundantly expresses P2X receptor channels for ATP; of these the most widespread in the brain is the P2X(4) channel. We show that ivermectin (IVM) is a specific positive allosteric effector of heterologously expressed P2X(4) and possibly of heteromeric P2X(4)/P2X(6) channels, but not of P2X(2), P2X(3), P2X(2)/P2X(3,) or P2X(7) channels. In the submicromolar range (EC(50,) approximately 250 nM) the action of IVM was rapid and reversible, resulting in increased amplitude and slowed deactivation of P2X(4) channel currents evoked by ATP. IVM also markedly increased the potency of ATP and that of the normally low-potency agonist alpha, beta-methylene-ATP in a use- and voltage-independent manner without changing the ion selectivity of P2X(4) channels. Therefore, IVM evokes a potent pharmacological gain-of-function phenotype that is specific for P2X(4) channels. We also tested whether IVM could modulate endogenously expressed P2X channels in the adult trigeminal mesencephalic nucleus and hippocampal CA1 neurons. Surprisingly, IVM produced no significant effect on the fast ATP-evoked inward currents in either type of neuron, despite the fact that IVM modulated P2X(4) channels heterologously expressed in embryonic hippocampal neurons. These results suggest that homomeric P2X(4) channels are not the primary subtype of P2X receptor in the adult trigeminal mesencephalic nucleus and in hippocampal CA1 neurons.
Khakh
B S
BS
Division of Biology, California Institute of Technology, Pasadena, California 91125, USA.
Proctor
W R
WR
Dunwiddie
T V
TV
Labarca
C
C
Lester
H A
HA
D000255:Adenosine Triphosphate / Q000494:pharmacology / Q000502:physiology; D000494:Allosteric Regulation; D000818:Animals; D002460:Cell Line; D003001:Cloning, Molecular; D005260:Female; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D007559:Ivermectin / Q000494:pharmacology*; D007700:Kinetics; D008322:Mammals; D008564:Membrane Potentials / Q000187:drug effects; D009479:Neuropeptides / Q000502:physiology; D009865:Oocytes / Q000187:drug effects / Q000502:physiology; D010641:Phenotype; D018048:Receptors, Purinergic P2 / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D058476:Receptors, Purinergic P2X2; D058477:Receptors, Purinergic P2X3; D058848:Receptors, Purinergic P2X4; D011994:Recombinant Proteins / Q000187:drug effects / Q000378:metabolism; D013498:Suramin / Q000494:pharmacology; D014162:Transfection; D014982:Xenopus laevis
D009479:Neuropeptides; C546401:P2RX2 protein, human; C546407:P2RX3 protein, human; C548226:P2RX4 protein, human; D018048:Receptors, Purinergic P2; D058476:Receptors, Purinergic P2X2; D058477:Receptors, Purinergic P2X3; D058848:Receptors, Purinergic P2X4; D011994:Recombinant Proteins; D013498:Suramin; D007559:Ivermectin; D000255:Adenosine Triphosphate