ATP/UTP activate cation-permeable channels with TRPC3/7 properties in rat cardiomyocytes.
Extracellular purines and pyrimidines have major effects on cardiac rhythm and contraction. ATP/UTP are released during various physiopathological conditions, such as ischemia, and despite degradation by ectonucleotidases, their interstitial concentrations can markedly increase, a fact that is clearly associated with arrhythmia. In the present whole cell patch-clamp analysis on ventricular cardiomyocytes isolated from various mammalian species, ATP and UTP elicited a sustained, nonselective cationic current, I(ATP). UDP was ineffective, whereas 2'(3')-O-(4-benzoylbenzoyl)-ATP was active, suggesting that P2Y(2) receptors are involved. I(ATP) resulted from the binding of ATP(4-) to P2Y(2) purinoceptors. I(ATP) was maintained after ATP removal in the presence of guanosine 5'-[gamma-thio]triphosphate and was inhibited by U-73122, a PLC inhibitor. Single-channel openings are rather infrequent under basal conditions. ATP markedly increased opening probability, an effect prevented by U-73122. Two main conductance levels of 14 and 23 pS were easily distinguished. Similarly, in fura-2-loaded cardiomyocytes, Mn(2+) quenching and Ba(2+) influx were significant only in the presence of ATP or UTP. Adult rat ventricular cardiomyocytes expressed transient receptor potential channel TRPC1, -3, -4, and -7 mRNA and the TRPC3 and TRPC7 proteins that coimmunoprecipitated. Finally, the anti-TRPC3 antibody added to the patch pipette solution inhibited I(ATP). In conclusion, activation of P2Y(2) receptors, via a G protein and stimulation of PLCbeta, induces the opening of heteromeric TRPC3/7 channels, leading to a sustained, nonspecific cationic current. Such a depolarizing current could induce cell automaticity and trigger the arrhythmic events during an early infarct when ATP/UTP release occurs. These results emphasize a new, potentially deleterious role of TRPC channel activation.
Alvarez
Julio
J
INSERM U-637, Physiopathologie cardiovasculaire, CHU Arnaud de Villeneuve, F-34295 Montpellier, France.
Coulombe
Alain
A
Cazorla
Olivier
O
Ugur
Mehmet
M
Rauzier
Jean-Michel
JM
Magyar
Janos
J
Mathieu
Eve-Lyne
EL
Boulay
Guylain
G
Souto
Rafael
R
Bideaux
Patrice
P
Salazar
Guillermo
G
Rassendren
François
F
Lacampagne
Alain
A
Fauconnier
Jérémy
J
Vassort
Guy
G
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000209:etiology / Q000378:metabolism; D002463:Cell Membrane Permeability; D004195:Disease Models, Animal; D004285:Dogs; D004963:Estrenes / Q000494:pharmacology; D006801:Humans; D008297:Male; D008564:Membrane Potentials; D051379:Mice; D018345:Mice, Knockout; D009203:Myocardial Infarction / Q000150:complications / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D054799:Phospholipase C beta / Q000037:antagonists & inhibitors / Q000378:metabolism; D011760:Pyrrolidinones / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000378:metabolism*; D058469:Receptors, Purinergic P2X; D058848:Receptors, Purinergic P2X4; D058473:Receptors, Purinergic P2Y2; D015398:Signal Transduction / Q000187:drug effects; D050052:TRPC Cation Channels / Q000378:metabolism*; D014544:Uridine Triphosphate / Q000378:metabolism*
D004963:Estrenes; C548226:P2RX4 protein, human; C546385:P2RY2 protein, human; C548227:P2rx4 protein, mouse; C548228:P2rx4 protein, rat; C546386:P2ry2 protein, mouse; C546387:P2ry2 protein, rat; D010726:Phosphodiesterase Inhibitors; D011760:Pyrrolidinones; D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; D058848:Receptors, Purinergic P2X4; D058473:Receptors, Purinergic P2Y2; D050052:TRPC Cation Channels; C104603:TRPC3 cation channel; C498498:Trpc7 protein, rat; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D000255:Adenosine Triphosphate; D054799:Phospholipase C beta; D014544:Uridine Triphosphate